Title of Invention	SYSTEM AND METHOD FOR SENDING BEACONS IN WIRELESS PERSONAL AREA NETWORKS
Abstract	ABSTRACT This invention explains a system and a method for sending beacons in wireless personal area networks having a medium access control mechanism the said system comprising: a superframe structure, having all beacons from different devices grouped at the start of the superframe and remaining period used as data period where the data period is further divided in several data slots; a beacon frame structure, including an element called Beacon Slot Reservation Indicator (BSRI) which contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon; a beacon elements. New Beacon Information Element (New Beacon IE) where if devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an indication of the New Device joining; and new DEVID structure, for addressing using information of device's MAC address and beacon slot number where device is sending its beacon and also by using information of device's MAC address and number obtained from MAS number where device is sending its beacon; a method for resending beacon using RSS procedure on detection of beacon collision. FIGURE 3 27

Title of Invention

SYSTEM AND METHOD FOR SENDING BEACONS IN WIRELESS PERSONAL AREA NETWORKS

Abstract

ABSTRACT This invention explains a system and a method for sending beacons in wireless personal area networks having a medium access control mechanism the said system comprising: a superframe structure, having all beacons from different devices grouped at the start of the superframe and remaining period used as data period where the data period is further divided in several data slots; a beacon frame structure, including an element called Beacon Slot Reservation Indicator (BSRI) which contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon; a beacon elements. New Beacon Information Element (New Beacon IE) where if devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an indication of the New Device joining; and new DEVID structure, for addressing using information of device's MAC address and beacon slot number where device is sending its beacon and also by using information of device's MAC address and number obtained from MAS number where device is sending its beacon; a method for resending beacon using RSS procedure on detection of beacon collision. FIGURE 3 27

Full Text	FIELD OF TECHNOLOGY This invention relates to the field of wireless mobile ad-hoc networks. Further, this invention relates to medium access control for wireless personal area networks that are based on wireless mobile ad-hoc networks. Particularly this invention relates to medium access control for wireless personal or networks which does not have any central coordinator. More particularly, this invention relates to effective mechanisms for the devices in sending beacons. More particularly, it provides mechanisms for network joining procedure for device, sending beacons, beacon collision avoidance, beacon collision detection either due to network joining or due to movement of the devices and beacon collision resolution procedure. Also more particularly, this invention encompasses a system and method for beaconing in wireless personal area networks based on ultra wide band (UWB) systems. DESCRIPTION OF RELATED ART The wireless personal area networks are defined to operate in the personal operating space, i.e. in a range of approximately 10 meters. The IEEE (http://www.ieee.orq) is involved in defining standards for such wireless personal area networks. The Ultra Wide Band (UWB) technology can provide data rates exceeding several hundreds of Mbps in this personal operating space. In wireless personal area networks, the medium is shared between all the devices for communication with each other. This necessitates a medium access control mechanism for the devices to manage medium access, broadly including how it may join the network, how it can transfer data at the required rate to another device, how the medium is best used, how to detect and resolve beacon collisions etc. Medium access control for wireless persona! area networks can be designed in two approaches - centralized and distributed. In the centralized approach, one of the devices acts On behalf of the whole network to coordinate in managing the media access operations for al! the devices. All other devices seek help of the centralized coordinator for media access operations like joining the network, reserving channel time, elc- In the Distributed approach, the media access operations are distributed evenly across all devices in the network and all the devices share the load of managing media access operations for each other. While the IEEE standards employ a centralized medium access control mechanisms, some distributed medium access control Devices that belong to the same beacon group shall utilize the same BPST for the superframe. However, some of the devices may define a different time as their BPST. In such case, 2 or more beacon groups may coexist. MASs are numbered relative to this starting time, The devices shall transform the numbering of MASs of other beaconing groups into the time reference of their main beaconing group. A device can be part of several beaconing groups but has to select one beaconing group as its main beaconing group. Devices include the BPOIE in all beacons. The BPOIE shall only include beacon information of devices that belong to the same beaconing group. Upon reception of a beacon frame, a device saves the DEVID of the sender and the slot number where the beacon is received. This information is included in (he BPOIE sent in the following superframe. Only the information of beacons received during a superframe is included in the BPOIE sent in the following superframe. If the DEVID of the device is missing in the BPOIE from a neighboring beacon during mMaxLostSeacons consecutive superframes, the device shall change the beacon slot to an idle slot in the following superframe. Data reservations (DRP) can be maintained, and don't need to be re-negotiated if the beacon slot is changed. Current art {MBOA draft specification) uses 2 byte DEVID as an addressing entity to represent 8 byte MAC address. A DEVID for a device is generated by the device using a 64 to 16 bit deterministic reduction operation performed on the device's MAC address. The association of the generated DEVID to the device's MAC address is transmitted in the device's beacon. The device will assure that the generated DEVID is unique within the device's cluster by receiving beacons and regenerating a new DEVID whenever conflict is identified. The present state of art in this field, as discussed in MBOA MAC, has certain limitations, namely, there is no mechanism to identify different type of beacon collision. Consequently, it does not have unique collision resolution scheme after detection of the collision. Also, multiple possible BP makes superframe fragmented. In addition, the usefulness of generating the DEVID from the 64 bit to 16 bit deterministic reduction operation, performed on the device's MAC address, is not clear. Currently the medium access control mechanism, as defined in MBOA MAC system, suffers from the following limitations: 1. Current mechanism makes superframe structure fragmented. 2. Current mechanism is not able to detect the different type of beacon collision, like collision at the time of joining the network and collision due to movement of devices, differently, 3- No mechanism provided for the beacon collision resolution. 4. Latency because of a complex method for creation of new beacon period when a beacon period is occupied with the beacons, for a device who is trying to join a network, 5. Large BPOIE size, if all devices in a beacon group are in range of a device in same beacon group. Consequently, the size of the beacon is larger, which is an overhead. 6. No method defined for device for joining a network, when existing beacon group is fully occupied with beacons. 7. Source and destination have to be in same beacon group to communicate with each other. 8. In current art there is a possibility of DEVID conflict and resolution procedure for this conflict is not defined. SUMMARY OF THE INVENTION The primary object of the invention is to provide a system and method for sending beacons continuously for the UWB wireless personal area networks, which are based on wireless ad-hoc networks, in a decentralized network topology where all devices undertakes the role of a light coordinator and there is no central coordinator. It is another object of the invention to provide a mechanism where new devices can determine the vacant slots for sending their beacons. It is another object of the invention to provide a mechanism where devices can avoid the collision of beacons transmitted by neighboring devices when joining the network by using the information provided in beacon of the device. It is another object of the invention to provide the mechanism for device to detect and distinguish the different type of beacon collision tike collision of beacons at the time of joining a network and collision of beacons due to movement of device, differently. It is another object of the invention to provide a mechanism and method for resolution of collision after the collision has been detected. It is another object of the invention to provide mechanism for the deterministic reduction of 64 bit MAC address to 16 bits which serves the purpose in a better way. The present invention relates to a system that allows an improved medium access control in the Wireless Personal Area Networks based on mobile ad-hoc networks in decentralized and distributed manner. The invention relates to system and method which allows all devices to send their beacon by avoiding, detecting and resolving the beacon collision. The system for the invention comprises of a new medium access control mechanism involving a new superframe structure, a new beacon frame structure, a new beacon elements, a new beacon procedure, new beacon collision detection and a new beacon collision resolution procedure. The present invention comprises of system and method which would solve the problems associated with current art, in the following manner: 1, The proposed superframe has all beacons from different devices grouped at the start of the superframe and remaining period in superframe is used as data period. The data period has been further divided in plural data slots. Grouped beacons and beacon period at the start of the superframe provides continuous data period for data transmission, 2, Proposed beacon includes an element called Beacon Slot Reservation Indicator (BSRI). This element contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon. 3, Current invention defines the method for joining the network by a device, which uses BSRI information for beacon collision avoidance. The device which is trying to join the network should listen to the beacons of neighboring devices, which all includes the BSRI, By ORing these BSRIs device can find the free slots in which it can start sending its beacon. 4, The invention defines an information element named New Beacon Irtformation Element (New Beacon IE). If devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an indication of the New Device joining, 5, The invention defines an information element named Expected Beacon Slot 6 Information Element (EBS IE), It indicates loss of expected beacon frorri a device in specific slot number 6. Proposed method in the invention also defines the mechanism for detection of different type of collision by using BSRI, New Beacon IE and EBS IE. If device that has sent its first beacon does not get New Beacon IE from its neighbor with new device's information, then it means that there is a collision at the time of joining because some other device also has sent its beacon in same beacon slot. BSRI is used for the detection of the collision due to movement of device. Because of movement of device, it is possible that there is a collision of beacons. As a result, some device, which does not get the beacon from both the devices, will send information the "beacon expected but did not receive" in its BSRI. By this information, device can find out that there is a collision because of movement and by looking to its neighbors it can find out whether it is moving or not, if it is moving then it should go to beacon collision resolution procedure. EBS IE is used to find the original owner of the beacon slot in case of collision. 7. Invention includes the method for collision resolution called Random Slot Selection (RSS) Procedure. A device, which suffers from beacon collision, should skip the random numbers of free beacon slot before start sending its beacon again. 8. The current invention avoids the complex method of creation of nev/ beacon period if existing beacon period is fully occupied, by having pre-allocated beacon period for beacons from different devices. So latency of joining network is also reduced. 9. BPOIE of existing art is not used in the invention but same functionality has been achieved by BSRI and it is useful for collision detection also. Size of BSRI is always fixed and does not increase in worst case scenario. The size of BSRI is lesser than that of BPOIE, which reduces the beacon overhead. 10. Methods provided in the invention do not require that, source and destination should be in same beacon group. The superframe structure proposed in the invention does not have different beacon groups, instead it has only one beacon period having all beacons grouped at the start of superframe, 11. As part of the invention, we propose a new structure for addressing entity (DEVID), using information of device's MAC address and beacon slot number where device is sending its beacon. 7 12, As part of the invention, we also propose a new structure for addressing entity (DEVID), using information of device's MAC address and number obtained from MAS number where device is sending its beacon. Accordingly the present invention relates to a system for sending beacons in wireless personal area networks having a medium access control mechanism, the said system comprising; (a) a superframe structure, having each beacon sent by each device are grouped at the start of the superframe and remaining period used as data period where the data period is further divided in plural data slots; (b) a beacon frame structure, including an information element called Beacon Slot Reservation Indicator (BSRI) which contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon; (c) an information element. New Beacon Information Element (NBIE) where if devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an indication of the New Device joining; (d) an information element, Expected Beacon Slot Information Element (EBSIE) where device misses a beacon from a device from which it has received earlier, then it sends EBSIE in its beacon; and (e) new DEVID structure, for addressing using information of device's MAC address and beacon slot number where device is sending its beacon and also by using information of device's MAC address and number obtained from MAS number where device is sending its beacon. The subsequent subsections describe the individual entities to effect the invention, In the superframe structure, all beacons are grouped at the start of the superframe and the total numbers of beacons slots may be fixed. The Superframe is composed of 2 periods: Beacon Period which is present at the beginning of the superframe and is divided into several beacon slots where each device in network broadcasts its beacon in one of these beacon slots; and Data Period (DP) where the said Data Period follows the beaconing period and is divided into several data slots where this data slots can be reserved for data transfer in peer-to-peer manner. All the beacons are sent during the BP, one beacon in one beacon slot by a device and every device sends a beacon such that it does not collide with other neighboring device's 8 beacons. The beacon frame structure contains some mandatory information and some optional information where the mandatory information comprise a BSRI (Beacon Slot Reservation Indicator) which indicates the beacon slots of the neighboring devices and a DSRI (Data Slot Reservation Indicator) which indicates the information of the data slot reservations. The beacon optionally contains IE (Information Elements), BSRI is the information about all the beacon slots from the reference of the device which is sending the beacon. BSRI consists of a bitmap which assigns 2 bits for the information of each of the possible beacon slots that are present in the BP of the superframe where the possible beacon slots are VBS, EBS, OBS, MBS wherein VBS is a Vacant Beacon Slot, for no beacon received in this slot number, EBS is a Beacon expected but not received in this slot, OBS is Other's Beacon Slot indicating Beacon received from some device in this slot and MBS is My Beacon Slot indicating the slot used by this device to send Its beacon. All devices, which are active, listen to the beacon period and update their BSRI on hearing beacons from neighboring devices. BSRI vary from one to other superframe as it is dynamically determined on the basis of receiving beacons from other devices and the BSRI is used by other devices receiving this beacon to decide the free slots for beaconing. The New Beacon Information Element (NBIE) contains the information of a new beacon received from a new device. NBIE includes the New Device's DEVID and beacon slot number in which the new beacon received where the said IE can include information about more than one new beacon. The Expected Beacon Slot Information Element (EBSIE) indicates loss of expected beacon from a device in specific beacon slot, EBSIE includes DEVID of the device from which beacon is missed and beacon slot number of that device, DEVID structure which uses superframe structure has grouped beacon in BP with several beacon slots where the structure includes Byte 1 which is 8 bit reduction of 64 bit MAC address of the device and Byte 0 which is 8 bit, and represents a beacon slot number in which device is sending a beacon. The slot in which the device is sending beacon is unique across the 2 hop neighborhood and slot number is used as a parameter in generating unique DEVID for the devices. The new DEVID structure includes a Byte 1 which is 8 bit reduction of 64 bit MAC address of the device and Byte 0 which is 8 bit obtained from MAS number in which device is sending a beacon. Accordingly this invention also explains a method for sending beacons in wireless personal area networks having a medium access control mechanism wherein the said method comprising the steps of: (a) BSRI Updation; (b) Network joining and Beaconing Procedure; (c) Beacon Collision Detection due to network joining where when a device that sends its first beacon does not get New Beacon IE from its neighbor with new device's information, resulting in a collision at the time of joining; (d) Beacon Collision Detection due to device movement when there is a possibility of collision of beacons because of movement of device; and (e) a new beacon collision resolution procedure Random Slot Selection (RSS) where the device, which suffers from beacon collision, skips the random numbers of free beacon slot before start sending its beacon again. 7 The device updates its own BSRI before sending it in its beacon and before updating BSRI, device listens to the entire beacon between times, when it had sent its last beacon in previous superframe and current time, BSR! updation comprising the steps of: initializing own BSRI bitmap with all zero; marking bit position as OBS in the BSRI bitmap, where device has received the beacon from other neighboring devices; marking bit position as MBS in the BSRI bitmap, the slot where device is going to send the beacon in next superframe; and marking bit position as EBS if device has received the beacon last superframe and expecting in this superframe but did not receive. For network joining, the device uses BSRIs from neighboring devices and when device which is trying to join the network starts listening for the beacons around it and if the device is within the range of some other devices that are already beaconing, then it receives some beacons else it will receive no beacons. The device is in receiving mode for an extended period which is at least the whole superframe period and when no beacons are received, the device chooses any of the slots from within the available beacon slots in the BP for its beacon. When the device initializes its BSRI with all bit pairs as VBS and marks its beacon slot with MBS in the BSRI the device begins transmitting its beacon with this BSRI. When one or more beacons are received, the device determines the parameters {BSRI) of the superframe from the received beacons and the device logically OR all the received BSRIs from the received beacons. From the resultant ORed BSRI's bitmap, the device decides a random VBS slot number and in next superframe, this device starts sending its beacon with updated BSRI and the 10 device always updates its BSRI before sending it in beacon. If no vacant slot is present, then the device does not start beaconing and waits for some random amount of time before starting again the network joining procedure. When a device in network, receives a beacon from a device for first time then the device which has received new beacon sends New Beacon IE in its superframe with information about the new beacon and device, which is sending that beacon. If device stops getting beacon in the slot in which, it was listening a beacon earlier then it sends that slot as BBS up to mMaxLosf Beacons counter, after that device marks thai slot as VBS. On Beacon Collision at network joining the device starts listening to beacon period just after sending its own beacon till the end of BP and in next superframe it listens till again, it reaches to its own slot to send the beacon. The device checks received beacons from different neighboring devices with BSRI in which the slot marked as OBS in the slot, in which the device itself has sent its first beacon. If device does not get a New Beacon IE with its information in that beacon slot with beacon from some neighboring device, then it is a collision of beacon. If there is no collision, then device creates its own BSRI and continue it's processing of sending beacons. If a collision of beacon is detected, then both devices, whose beacon have collided, does not send next beacon and try to resend beacon. On Beacon Collision due to device movement the device, which detects the collision, expects a beacon in the slot, but it does not get anything in case of collision where it changes the slot value to EBS (Beacon expected but not received) in the BSRI which is being sent by it. The devices which sent a beacon in that slot find out and know that the beacon they sent was not received; a collision occurs, A device which discovers that its beacon was not received by neighboring devices, checks to see if the neighborhood is the same or has it gone away from it by detecting from the identity of the devices whose beacons it received in the slots in previous superframe, if the device finds out that its neighborhood has changed then it is determined that this device ventured out into the zone of other devices. If EBSIE is received by a device with information of its own DEViD and beacon slot number It indicates that, its tDeacon did not reach one of the neighbor. If EBSIE is received by a device with information of its own beacon slot number but some other DEVID, it indicates to the device that, the slot has been reserved by some other device and there is a collision of beacon in the slot. In collision resolution procedure Random Slot Skip (RSS), the device is adapted to send first beacon, when device has suffered from beacon collision while sending its beacon. After detecting the collision, device decides a random number CW, which must 11 be in between CWmin and CWmax. The Device has to "skip" CW number of free slots in BP before introducing its beacon again in BP, which spans more than one superframe. The device is adapted to continuously update BSRI information received from its neighbors by listening to all the beacons. The device OR all BSRIs and count the free slots to find out CW numbers of slots has been skipped. After skipping CW numbers of slots, device introduces its beacon in next free slot and checks, if its beacon has been sent successfully. If there Is no collision, then device continues sending its tseacon in selected slot- If collision is detected after RSS procedure, then device increments the CWmin value where new CWmin is greater than or equal to CW. After selecting new CWmin and using existing CWmax, device selects random CW between CWmin and CWmax. The new device performs RSS procedure and on each beacon collision situation, CW will keep increasing. If (CWmax - CWmin) is less than CWmindur (Contention window minimum duration) then device stops its back-off procedure and avoid retrying for random amount of time and then start its procedure of beacon sending. The other objects, features and advantages of the present invention will be apparent from the accompanying drawings and the detailed description as follows. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 illustrates the WPAN as a decentralized and distributed ad-hoc network system and range of all devices; Figure 2 illustrate the superframe structure in current art, which includes MAS and beacon periods; Figure 3 illustrate the proposed superframe structure, in which all the beacons are grouped together at the start of the superframe; Figure 4 illustrates the structure of the proposed Beacon Slot Reservation Indicator (BSRI); Figure 5 illustrates the structure of New Beacon Information Element (NBIE); Figure 6 illustrates the structure of Expected Beacon Slot Information Element (EBSIE); Figure 7 depicts the network topology for the beacon collision situation at the time of network joining; Figure 8 shows the snap shot of the superframe at the time of beacon collision; 12 Figure 9 shows network topology for the beacon collision due to movement of the device in decentralized/distributed WPAN; Figure 10 illustrates the structure of DEVID, where one of the elements of DEVID is beacon slot number, where beacon of the device is sent; and Figure 11 illustrates the structure of DEVID, where one of the elements of DEVID is number from MAS number, where beacon of the device is sent. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system that allows an improved medium access control in the decentralized Wireless Personal Area Networks based on mobile ad'hoc networks. The invention relates to system and method which allows device to join the network and send ttie beacons by employing mechanisms for beacon collision avoidance, if tieacon collision occurs due to movement of device or at the time of joining of the network, then collision detection method and collision resolution method. The system for the invention comprises of a new medium access control mechanism involving a new superframe structure, a new element in beacon frame called Beacon Slot Reservation Indicator (BSRI), New Beacon Information Element, method for joining network using information provided in BSRI, beacon collision detection method using BSRI and New Beacon Information Element, and collision resolution procedure named Random Slot Skip (RSS) Procedure. The subsequent subsections describe the individual entities to effect the invention: 1. Figure 3 illustrates the proposed new superframe structure. Superframe structure of the Invention has following characteristics: - All beacons are grouped at the start of the superframe. - Total numbers of beacons slots may or may not be fixed (For example, 256 beacons slots). The choice for any other number does not affect the operation of the invention. Remaining period as data period (for example, 256 data slots). This number can be set depending on the actual number of devices in the current network configuration, and it does not affect the operation of the invention. Superframe is composed of 2 periods: 13 - Beacon Period: This period is present at the beginning of the superframe and is divided into several beacon slots (256 for the example). Each device in network broadcasts its beacon in one of these beacon slots. - Data Period (DP): Data Period follows the beaconing period and is divided into several (for example, 256) data slots. These data slots can be reserved tor data transfer in peer-to-peer manner. All the beacons are sent during the BP, one beacon in one beacon slot by a device. Every device will send a beacon such that it should not collide with other neighboring device's beacons. Data slots may require reservation by the devices for their use. 2. Figure 5 illustrate structure of New Beacon Information Element (NBIE). NBIE contains the information a new beacon received from a new device. As shown in Figure 5, NBIE includes the New Device's DEVID and beacon slot number in which the new beacon received. This IE can include information about more than one new beacon. 3. Figure 6 illustrate structure of Expected Beacon Slot Information Element (EBSIE). EBSIE contains the information of loss of beacon from particular devices. It includes the DEVID of the device whose beacon has been missed and beacon slot number. This IE can include information about more than one new beacon. 4. Figure 10 illustrates the proposed new DEVID structure which uses superframe structure proposed in the invention, which shows grouped beacon in BP with several (for example, 256) beacon slots. Structure includes the following elements: - Byte 1 is 8 bit reduction of 64 bit MAC address of the device. - Byte 0 is 8 bit, and represents a beacon slot number in which device is sending a beacon. The slot in which the device is sending beacon is unique across the 2 hop neighborhood. Hence slot number can be used as a parameter in generating unique DEVID for the devices. 5. Figure 11 illustrates the proposed new DEVID structure. Structure includes the following elements: - Byte 1 is 8 bit reduction of 64 bit MAC address of the device. 14 - Byte 0 is 8 bit obtained from MAS number in which device is sending a beacon. The subsequent subsections describe the operation of the invention: 1. BSRl Updation Device always updates its own BSRl before sending it in its beacon. Before updating BSRl, device listens to the entire beacon between times - when it had sent its last beacon in previous superframe and current time (i.e. just before sending its beacon again in this superframe). 1) Initialize own BSRl bitmap with all zero 2) Mark bit position as OBS in the BSRl bitmap, where device has received the beacon from other neighboring devices. 3) Mark bit position as MBS in the BSRl bitmap, the slot where device is going to send the beacon in next superframe. 4) Mark bit position as EBS if device has received the beacon last superframe and expecting in this superframe but did not receive. 2. Networking joining and Beaconing Procedure Network joining procedure in the current art uses BPOIE from neighboring devices and it includes procedure of new beacon period creation, if free slot is not available in existing beacon period. In our proposed inventive method for network joining, the device uses BSRIs from neighboring devices. Proposed procedure, in the present invention, for a device to join network is explained in following steps: 1} Device which is trying to join the network starts listening for the beacons around it. If the device Is within the range of some other devices that are already beaconing, then it receives some beacons else it will receive no beacons- The device should be in receiving mode for an extended period which is at least the whole superframe period. 2) In case no beacons are received, the device can choose any of the slots from within the available beacon slots (for example, 256) in the BP for its beacon. The device initializes its BSRl with all bit pairs as VBS (00) (since no beacons are being received in those slots) and marks its beacon slot with MBS (11) in the BSRl, The device begins transmitting its 15 beacon with this BSRI. 3) In case one or more beacons are received, the device determines the parameters (BSRI) of the superframe from the received beacons. The device should logically OR all the received BSRIs from the received beacons. 4) From the resultant ORed BSRI's bitmap, the device decides a random VBS slot number. In next superframe, this device starts sending its beacon with updated BSRI. Device should always update its BSRI before sending it in beacon. 5} If no vacant slot is present, then the device cannot start beaconing and hence waits for some random amount of time before starting again the ■network joining procedure. When a device in network, receives a beacon from a device for first time, i.e. it has not received any beacon from that device in same beacon slot previously, then the device which has received new beacon should send New Beacon IE in its superframe with information about this new beacon and device, which is sending that beacon. If device stops getting beacon in the slot in which, it was receiving a beacon earlier then it should send that slot as EBS up to mMaxLostBeacons counter, after that device should mark that slot as VBS. 3. Beacon Collision Detection (Beacon Collision at network joining) This situation may arise when two devices choose the same slot after listening to the channel and decide to beacon in the same slot. Figure 5 displays the topology for this type of beacon collision. New device had sent its first beacon in randomly selected slot, according to procedure as described in previous sections. After that, following procedure is required for collision detection. Device starts listening to beacon period just after sending its own beacon till the end of BP and in next superframe it listens till again, it reaches to its own slot to send the beacon. Device checks received beacons from different neighboring devices with BSRI in which the slot was marked as OBS in the slot, in which the device itself has sent its first beacon. If device does not get a New Beacon IE with its information in that beacon slot with beacon from some neighboring device, then it means that there is a collision of beacon. Figure 7 illustrates the superframe snap shot at the time of collision. 16 If there is no collision, then device should create its own BSRI and continue it's processing of sending beacons using procedure as described earlier. If a collision of beacon has been detected, then both devices, whose beacon have collided, should not send next beacon and try to resend beacon by Random Slot Skip Procedure, which is described in following sections. 4, Beacon Collision Detection (Beacon Collision due to device movement). This situation may arise when a mobile device moves away from its zone and enters a zone away from its two hop neighborhood. The beacon slot reservation is only guaranteed up to two hops by the BSRI and hence with this movement of the device, its beacon may now collide with some other beacons of the devices in this zone. Figure 9 illustrates the situation of collision due to device movement. This collision can be detected by the other devices in the network. Device, which detects the collision, is expecting a beacon in the slot, but it does not get anything in case of collision shown in figure 9. So it changes the slot value to EBS (Beacon expected but not received) in the BSRI which is being sent by it. The devices which sent a beacon in that slot find out and know that the beacon they sent was not received, this situation can be because of collision. A device which discovers that its beacon was not received by neighboring devices, checks to see if the neighborhood is the same or has gone away from it (changed). This can be detected from the identity of the devices whose beacons it received in the slots in previous superframe. If the device finds out that its neighborhood has changed then it is determined that this device ventured out into the ^one of other devices, at least 2 hops separated from its original position. If EBSIE is received by a device with information of its own DEVID and beacon slot number, it indicates that its beacon did not reach one of the neighbors. If EBSIE is received by a device with information of its own beacon slot number but some other DEVID, it indicates to the device that, the slot has been reserved by some other device and there is a collision of beacon in the slot. This device which finds that it has moved from its location should go for collision resolution. For collision resolution, it should use the proposed Random 17 Slot Skip Procedure, which is described in following sections. The device, whose neighborhood has not changed, should continue its process of sending beacon without going for collision resolution. 5, Beacon Collision Resolution (Random Slot Skip Procedure) This procedure is proposed for sending first beacon by the device, when device had suffered from beacon collision while sending its beacon, as described in previous section. Following steps describes the procedure in detail. 1) After detecting the collision, device decides a random number CW, which must be in between CWmin and CWmax. 2) Device has to "skip" CW number of free slots in BP before introducing its beacon again in BP, which may span more than one superframe. 3) For this procedure, device should continuously update BSRI information received from its neighbors by listening to all the beacons. Device should OR all BSRIs and should count the free slots to find out that, CW numbers of slots has been skipped. 4) After skipping CW numbers of slots, device should introduce its beacon in next free slot. Also it should check, if its beacon has been sent successfully as described in beaconing procedure in above sections. 5) If there is no collision, then device can continue sending its beacon in selected slot as described in beaconing procedure. If collision is detected again after RSS procedure, as described in collision detection procedure, then device should increment the CWmin value up to CW or more then that. So, new CWmin >= CW, After selecting new CWmin and using existing CWmax, device should select random CW between CWmin and CWmax. New device should perform RSS procedure again. On each beacon collision situation, CW will keep on increasing. If {CWmax - CWmin) is less, CWmindur (Contention window minimum duration) then device should stop its back-off procedure and should avoid retrying for random amount of time and then can start its procedure of beacon sending again as specified in above sections. Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention. 18 GLOSSARY OF TERMS AND DEFINITONS THEREOF ASIE: Application Specific Information Element BP: Beacon Period BPOIE: Beacon Period Occupancy Information Element BPST: Beacon Period Start Time BSRI: Beacon Slot Reservation Indicator CW: Contention Window DEVID: Device Identifier DP: Data Period DRP: Distributed Reservation Protocol DS: Data Slot DSRI: Data Slot Reservation Indicator EBS: Expected Beacon Slot IE". Information Element MAC: Medium Access Control MAS: Medium Access Slot MBOA: Multi Band OFDM Alliance MBS: My Beacon Slot N0IE: New Beacon Information Element OBS: Other's Beacon Slot OFDM: Orthogonal Frequency Division Multiplexing PSIE: Power Save Information Element RSS: Random Slot Skip UWB: Ultra Wide Band VBS: Vacant Beacon Slot VSIE: Vendor Specific Information Element WPAN: Wireless Personal Area Network EBSIE: Expected Beacon Slot Information Element 19 WE CLAIM 1. A system for sending beacons in wireless personal area networks having a medium access control mechanism, the said system comprising: a superframe structure, having each beacon sent by each device are grouped at the start of the superframe and remaining period used as data period -where the data period is further divided in plural data slots; a beacon frame structure, including an information element called Beacon Slot Reservation Indicator (BSRI) which contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon; an information element, New Beacon Information Element (NBIE) where if devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an Indication of the New Device joining; an information element. Expected Beacon Slot Information Element (EBSIE) where device misses a beacon from a device from which it has received earlier, then it sends EBSIE in its beacon; and new DEVID structure, for addressing using information of device's fylAC address and beacon slot number where device is sending its beacon and also by using information of device's MAC address and number obtained from MAS number where device is sending its beacon. 2. A system as claimed in claim 1, wherein in the superframe structure, all beacons are grouped at the start of the superframe and the total numbers of beacons slots can be variable. 3. A system as claimed in claim 1, wherein the superframe is composed of 2 periods: Beacon Period which is present at the beginning of the superframe and is divided into several beacon slots where each device in network broadcasts its beacon in one of these beacon slots; and Data Period (DP) where the said Data Period follows the beacon period and is divided into several data slots where this data slots is reserved for data transfer. 4. A system as claimed in claim 1, wherein all the beacons are sent during the BP, one beacon in one beacon slot by a device and each device sends a beacon such that it does not collide with other device's beacons. 20 5. A system as claimed in claim 1, wherein the beacon frame structure contains some mandatory information and some optional information where the mandatory information comprise; a BSRI (Beacon Slot Reservation Indicator) which indicates the beacon slots of the neighboring devices; a DSRI (Data Slot Reservation Indicator) which indicates the information of the data slot reservations; wherein the beacon optionally contain IE (Information Elements) where the available IE are DS-Req IE: Data Slot Request IE DS-Res IE: Data Slot Response IE NBIE: New Beacon IE EBSIE: Expected Beacon Slot IE SPSG-Req IE: Synchronized PS Group Request IE PSIE: Power Save IE VSIE: Vendor Specific IE ASIE: Application Specific IE. 6. A system as claimed in claim 5 wherein BSRI is the information about all the beacon slots from the reference of the device which is sending the beacon. 7. A system as claimed in claim 5 wherein BSRI consists of a bitmap which assigns 2 bits for the information of each of the possible beacon slots that are present in the BP of the superframe where the possible status of the beacon slot are VBS, EBS, OBS, MBS. 8. A system as claimed in claim 7 wherein VBS is a Vacant Beacon Slot, for no beacon received in this slot number, EBS is an Expected Beacon Slot, means beacon expected but not received in this slot, OBS is Other's Beacon Slot indicating beacon received from some device in this slot and MBS is My Beacon Slot indicating the slot used by the device to send its own beacon, 9. A system as claimed in claim 5 wherein each active device listens to the beacon period and update their BSRI on hearing beacons from neighboring devices. 10. A system as claimed in claim 5 wherein BSRI vary from one to other superframe as it is dynamically determined on the basis of receiving beacons from other devices and the 21 BSR! is used by other devices receiving the beacon to decide the free slots for transmitting beacon. 11. A system as claimed in claim 1 wherein the New Beacon Information Element (NBIE) contains the information of a new beacon other than received in earlier superframe from a new device in neighborhood. 12. A system as claimed in claim 11 wherein NBIE includes the New Device's D£VID and beacon slot number in wtiich the new beacon received where the said IE can include information about more than one new beacon. 13. A system as claimed in claim 1 wherein the Expected Beacon Slot Information Element (EBSIE) contains the information of the missed beacon which was received in earlier superframe from a device in neighborhood. 14. A system as claimed in claim 13 wherein EBSIE includes the DEVID of the device from which the beacon has been missed and beacon slot number of that, 15. A system as claimed in claim 1 wherein DEVID structure which uses superframe structure has grouped beacon in BP with several beacon slots. 16. A system as claimed in claim 15 wherein the slot in which the device is sending beacon is unique across the 2 hop neighborhood and slot number is used as a pafameter in generating unique DEVID for the devices. 17. A system as claimed in claim 15 wherein the new DEVID structure includes one of the byte, which is 8 bit reduction of 64 bit MAC address of the device and another byte is obtained from MAS number in which device is sending a beacon, 18. A method for sending beacons in wireless personal area networks having a medium access control mechanism wherein the said method comprising the steps of: BSRI Updation; Network joining and Beaconing Procedure; Beacon Collision Detection due to network joining where when a device that sends its first beacon does not get New Beacon IE from its neighbor with new device's information, resulting in a collision at the time of joining; Beacon Collision Detection due to device movement when there is a possibility of collision of beacons because of movement of device; and a new beacon collision resolution procedure Random Slot Selection (RSS) where the device, which suffers from beacon collision, skips the random numbers of free beacon 22 slot before start sending its beacon again, 19. A method as claimed in claim 18 wherein the device updates its own BSRI before sending it in its beacon and before updating BSRI, device listens to the entire beacon period. 20- A method as claimed in claim 18 wherein the said BSRI updation comprising the steps of: inilializtng own BSRI bitmap with ail zero; marking bit position as OBS in the BSRI bitmap, where device has received the beacon from other neighboring devices; marking bit position as MBS in the BSRI bitmap, the slot where device is going to send the beacon in next superframe; and marking bit position as EBS if device has received the beacon last superframe and expecting in this superframe but did not receive. 21. A method as claimed in claim 18 wherein for network joining, the device uses BSRIs from neighboring devices and when device which is trying to join the network starts listening for the beacons around it and if the device is within the range of some other devices that are already beaconing, then it receives some beacons else it will receive no beacons, 22. A method as claimed in claim 18 wherein the device is in receiving mode for an extended period which is at least the whole superframe period and when no beacons are received, the device chooses any of the slots from the available beacon slots in the BP for its beacon. 23. A method as claimed in claim 18 wherein when the device initializes its BSRI with all bit pairs as VBS and marks its beacon slot with MBS in the BSRI the device begins transmitting its beacon with this BSRI. 24. A method as' claimed in claim 18 wherein when one or more beacons are received, the device determines the parameters of the superframe from the received beacons, and the device logically OR alt the received BSRIs from the received beacons. 25. A method as claimed in claim 18 wherein from the resultant ORed BSRI's bitmap, the device decides a random VBS slot number and in next superframe, this device starts sending its beacon with updated BSRI and the device always update its BSRI before sending it in beacon. 23 26. A method as claimed in claim 18 wherein if no vacant slot is present, then the device does not start beaconing and waits for some random amount of time before starting again the network joining procedure. 27. A method as claimed in claim 18 wherein when a device in network, receives a beacon from a device from which the device has not received beacon earlier then the device which has received new beacon sends New Beacon IE in its superframe with information about the new beacon and device, which is sending that beacon. 28. A method as claimed in claim 18 wherein if device stops getting beacon in the slot in which, it was listening a beacon earlier then it sends that slot as EBS up to mMaxLostBeacons superframes, after that device marks that slot as VBS, 29. A method as claimed in claim 18 wherein on Beacon Collision at network joining, the device starts listening to beacon period just after sending its own beacon till the end of BP and in next superframe it listens till again, it reaches its own slot to send the beacon. 30. A method as claimed in claim 29 wherein the device checks received beacons from different neighboring devices with BSRI in which the slot marked as OBS in the slot, in which the device itself has sent its first beacon. 31. A method as claimed in claim 29 wherein if device does not get a New Beacon IE with its information in that beacon slot with beacon from some neighboring device, then it is a collision of beacon. 32. A method as claimed in claim 29 wherein if there is no coiiision, then device creates its own BSRI and continue its process of sending beacons. 33. A method as claimed in claim 29 wherein if a collision of beacon is detected, then both devices, whose beacon has collided, does not send next beacon and try to resend beacon. 34. A method as claimed in claim 18 wherein on beacon collision due to device movement the device, which detects the collision, expects a beacon in the slot, but it does not get anything in case of collision where it changes the slot value to EBS (Beacon expected but not received) in the BSRI which is being sent by it, 35. A method as claimed in claim 18 wherein if EBSIE is received by a device with information of its own DEVID and beacon slot number, it Indicates that its beacon did not reach one of the neighbors. If EBSIE is received by a device with information of its own beacon slot number but some other DEVID. it indicates to the device that the slot has been reserved by some other device and there is a collision of beacon in the slot. 24 36. A method as claimed in claim 34 wherein the devices which sent a beacon in that slot find out and know that the beacon they sent was not received; a collision occurred. 37. A method as claimed in claim 34 wherein if the device finds out that its neighborhood has changed then it is determined that this device ventured out into the zone of other devices, 38. A method as claimed in claim 18 wherein in collision resolution procedure Random Slot Skip (RSS), the device is adapted to send first beacon, when device has suffered from beacon collision while sending its beacon. 39- A method as claimed in claim 38 wherein after detecting the collision, device.decides a random number CW, which must be in between CWmin and CWmax, 40. A method as claimed in claim 39 wherein the device has to skip CW number of free slots in BP before introducing its beacon again in BP, which can span more than one superframe. 41. A method as claimed in claim 39 wherein the device is adapted to continuously update BSRI information received from its neighbors by listening to all the beacons during RSS procedure, 42. A method as claimed in claim 39 wherein the device OR all BSRIs and count the free slots to find out CW numbers of slots has been skipped. 43. A method as claimed in claim 39 wherein after skipping CW numbers of slots, device introduces its beacon in next free slot and checks, if its beacon has been sent successfully, 44. A method as claimed in claim 39 wherein if there is no collision, then device'continues sending its beacon in selected slot. 45. A method as claimed in claim 39 wherein if collision is detected after RSS procedure, then device increments the CWmin value where new CWmin is greater than or equal to CW. 46. A method as claimed in claim 39 wherein after selecting new CWmin and using existing CWmax. device selects random CW between CWmin and CWmax. 47. A method as claimed in claim 39 wherein the new device perform RSS procedure and on each beacon collision situation, CWwill keep increasing. 48. A method as claimed in claim 39 wherein if (CWmax - CWmin) is less than CWmindur (Contention window minimum duration) then device stops its back-off procedure and 25 I avoids retrying for random amount of time and then starts sending beacon by joining the network again. 49. A system for sending beacons in wireless personal area networks tiaving a medium access control mechanism substantially as herein described particularly with reference to the drawings. 50. A method for sending beacons in wireless networks having a medium access control mechanism substantially as herein described particularly with reference to the drawings. 26

Full Text

FIELD OF TECHNOLOGY
This invention relates to the field of wireless mobile ad-hoc networks. Further, this invention relates to medium access control for wireless personal area networks that are based on wireless mobile ad-hoc networks. Particularly this invention relates to medium access control for wireless personal or networks which does not have any central coordinator. More particularly, this invention relates to effective mechanisms for the devices in sending beacons. More particularly, it provides mechanisms for network joining procedure for device, sending beacons, beacon collision avoidance, beacon collision detection either due to network joining or due to movement of the devices and beacon collision resolution procedure. Also more particularly, this invention encompasses a system and method for beaconing in wireless personal area networks based on ultra wide band (UWB) systems.
DESCRIPTION OF RELATED ART
The wireless personal area networks are defined to operate in the personal operating space, i.e. in a range of approximately 10 meters. The IEEE (http://www.ieee.orq) is involved in defining standards for such wireless personal area networks. The Ultra Wide Band (UWB) technology can provide data rates exceeding several hundreds of Mbps in this personal operating space. In wireless personal area networks, the medium is shared between all the devices for communication with each other. This necessitates a medium access control mechanism for the devices to manage medium access, broadly including how it may join the network, how it can transfer data at the required rate to another device, how the medium is best used, how to detect and resolve beacon collisions etc.
Medium access control for wireless persona! area networks can be designed in two approaches - centralized and distributed. In the centralized approach, one of the devices acts On behalf of the whole network to coordinate in managing the media access operations for al! the devices. All other devices seek help of the centralized coordinator for media access operations like joining the network, reserving channel time, elc- In the Distributed approach, the media access operations are distributed evenly across all devices in the network and all the devices share the load of managing media access operations for each other. While the IEEE standards employ a centralized medium access control mechanisms, some distributed medium access control

Devices that belong to the same beacon group shall utilize the same BPST for the superframe. However, some of the devices may define a different time as their BPST. In such case, 2 or more beacon groups may coexist. MASs are numbered relative to this starting time, The devices shall transform the numbering of MASs of other beaconing groups into the time reference of their main beaconing group. A device can be part of several beaconing groups but has to select one beaconing group as its main beaconing group.
Devices include the BPOIE in all beacons. The BPOIE shall only include beacon information of devices that belong to the same beaconing group.
Upon reception of a beacon frame, a device saves the DEVID of the sender and the slot number where the beacon is received. This information is included in (he BPOIE sent in the following superframe. Only the information of beacons received during a superframe is included in the BPOIE sent in the following superframe.
If the DEVID of the device is missing in the BPOIE from a neighboring beacon during mMaxLostSeacons consecutive superframes, the device shall change the beacon slot to an idle slot in the following superframe. Data reservations (DRP) can be maintained, and don't need to be re-negotiated if the beacon slot is changed.
Current art {MBOA draft specification) uses 2 byte DEVID as an addressing entity to represent 8 byte MAC address. A DEVID for a device is generated by the device using a 64 to 16 bit deterministic reduction operation performed on the device's MAC address. The association of the generated DEVID to the device's MAC address is transmitted in the device's beacon. The device will assure that the generated DEVID is unique within the device's cluster by receiving beacons and regenerating a new DEVID whenever conflict is identified.
The present state of art in this field, as discussed in MBOA MAC, has certain limitations, namely, there is no mechanism to identify different type of beacon collision. Consequently, it does not have unique collision resolution scheme after detection of the collision. Also, multiple possible BP makes superframe fragmented. In addition, the usefulness of generating the DEVID from the 64 bit to 16 bit deterministic reduction operation, performed on the device's MAC address, is not clear.
Currently the medium access control mechanism, as defined in MBOA MAC system, suffers from the following limitations:
1. Current mechanism makes superframe structure fragmented.

2. Current mechanism is not able to detect the different type of beacon collision, like collision at the time of joining the network and collision due to movement of devices, differently,
3- No mechanism provided for the beacon collision resolution.
4. Latency because of a complex method for creation of new beacon period when a beacon period is occupied with the beacons, for a device who is trying to join a network,
5. Large BPOIE size, if all devices in a beacon group are in range of a device in same beacon group. Consequently, the size of the beacon is larger, which is an overhead.
6. No method defined for device for joining a network, when existing beacon group is fully occupied with beacons.
7. Source and destination have to be in same beacon group to communicate with each other.
8. In current art there is a possibility of DEVID conflict and resolution procedure for this conflict is not defined.
SUMMARY OF THE INVENTION
The primary object of the invention is to provide a system and method for sending beacons continuously for the UWB wireless personal area networks, which are based on wireless ad-hoc networks, in a decentralized network topology where all devices undertakes the role of a light coordinator and there is no central coordinator.
It is another object of the invention to provide a mechanism where new devices can determine the vacant slots for sending their beacons.
It is another object of the invention to provide a mechanism where devices can avoid the collision of beacons transmitted by neighboring devices when joining the network by using the information provided in beacon of the device.
It is another object of the invention to provide the mechanism for device to detect and distinguish the different type of beacon collision tike collision of beacons at the time of joining a network and collision of beacons due to movement of device, differently.
It is another object of the invention to provide a mechanism and method for

resolution of collision after the collision has been detected.
It is another object of the invention to provide mechanism for the deterministic reduction of 64 bit MAC address to 16 bits which serves the purpose in a better way.
The present invention relates to a system that allows an improved medium access control in the Wireless Personal Area Networks based on mobile ad-hoc networks in decentralized and distributed manner.
The invention relates to system and method which allows all devices to send their beacon by avoiding, detecting and resolving the beacon collision.
The system for the invention comprises of a new medium access control mechanism involving a new superframe structure, a new beacon frame structure, a new beacon elements, a new beacon procedure, new beacon collision detection and a new beacon collision resolution procedure.
The present invention comprises of system and method which would solve the problems associated with current art, in the following manner:
1, The proposed superframe has all beacons from different devices grouped at the start of the superframe and remaining period in superframe is used as data period. The data period has been further divided in plural data slots. Grouped beacons and beacon period at the start of the superframe provides continuous data period for data transmission,
2, Proposed beacon includes an element called Beacon Slot Reservation Indicator (BSRI). This element contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon.
3, Current invention defines the method for joining the network by a device, which uses BSRI information for beacon collision avoidance. The device which is trying to join the network should listen to the beacons of neighboring devices, which all includes the BSRI, By ORing these BSRIs device can find the free slots in which it can start sending its beacon.
4, The invention defines an information element named New Beacon Irtformation Element (New Beacon IE). If devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an indication of the New Device joining,
5, The invention defines an information element named Expected Beacon Slot
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Information Element (EBS IE), It indicates loss of expected beacon frorri a device in specific slot number
6. Proposed method in the invention also defines the mechanism for detection of different type of collision by using BSRI, New Beacon IE and EBS IE. If device that has sent its first beacon does not get New Beacon IE from its neighbor with new device's information, then it means that there is a collision at the time of joining because some other device also has sent its beacon in same beacon slot. BSRI is used for the detection of the collision due to movement of device. Because of movement of device, it is possible that there is a collision of beacons. As a result, some device, which does not get the beacon from both the devices, will send information the "beacon expected but did not receive" in its BSRI. By this information, device can find out that there is a collision because of movement and by looking to its neighbors it can find out whether it is moving or not, if it is moving then it should go to beacon collision resolution procedure. EBS IE is used to find the original owner of the beacon slot in case of collision.
7. Invention includes the method for collision resolution called Random Slot Selection (RSS) Procedure. A device, which suffers from beacon collision, should skip the random numbers of free beacon slot before start sending its beacon again.
8. The current invention avoids the complex method of creation of nev/ beacon period if existing beacon period is fully occupied, by having pre-allocated beacon period for beacons from different devices. So latency of joining network is also reduced.
9. BPOIE of existing art is not used in the invention but same functionality has been achieved by BSRI and it is useful for collision detection also. Size of BSRI is always fixed and does not increase in worst case scenario. The size of BSRI is lesser than that of BPOIE, which reduces the beacon overhead.
10. Methods provided in the invention do not require that, source and destination should be in same beacon group. The superframe structure proposed in the invention does not have different beacon groups, instead it has only one beacon period having all beacons grouped at the start of superframe,
11. As part of the invention, we propose a new structure for addressing entity (DEVID), using information of device's MAC address and beacon slot number where device is sending its beacon.
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12, As part of the invention, we also propose a new structure for addressing entity (DEVID), using information of device's MAC address and number obtained from MAS number where device is sending its beacon.
Accordingly the present invention relates to a system for sending beacons in wireless personal area networks having a medium access control mechanism, the said system comprising;
(a) a superframe structure, having each beacon sent by each device are grouped at the start of the superframe and remaining period used as data period where the data period is further divided in plural data slots;
(b) a beacon frame structure, including an information element called Beacon Slot Reservation Indicator (BSRI) which contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon;
(c) an information element. New Beacon Information Element (NBIE) where if devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an indication of the New Device joining;
(d) an information element, Expected Beacon Slot Information Element (EBSIE) where device misses a beacon from a device from which it has received earlier, then it sends EBSIE in its beacon; and
(e) new DEVID structure, for addressing using information of device's MAC address and beacon slot number where device is sending its beacon and also by using information of device's MAC address and number obtained from MAS number where device is sending its beacon.
The subsequent subsections describe the individual entities to effect the invention,
In the superframe structure, all beacons are grouped at the start of the superframe and the total numbers of beacons slots may be fixed. The Superframe is composed of 2 periods: Beacon Period which is present at the beginning of the superframe and is divided into several beacon slots where each device in network broadcasts its beacon in one of these beacon slots; and Data Period (DP) where the said Data Period follows the beaconing period and is divided into several data slots where this data slots can be reserved for data transfer in peer-to-peer manner. All the beacons are sent during the BP, one beacon in one beacon slot by a device and every device sends a beacon such that it does not collide with other neighboring device's
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beacons. The beacon frame structure contains some mandatory information and some optional information where the mandatory information comprise a BSRI (Beacon Slot Reservation Indicator) which indicates the beacon slots of the neighboring devices and a DSRI (Data Slot Reservation Indicator) which indicates the information of the data slot reservations. The beacon optionally contains IE (Information Elements), BSRI is the information about all the beacon slots from the reference of the device which is sending the beacon.
BSRI consists of a bitmap which assigns 2 bits for the information of each of the possible beacon slots that are present in the BP of the superframe where the possible beacon slots are VBS, EBS, OBS, MBS wherein VBS is a Vacant Beacon Slot, for no beacon received in this slot number, EBS is a Beacon expected but not received in this slot, OBS is Other's Beacon Slot indicating Beacon received from some device in this slot and MBS is My Beacon Slot indicating the slot used by this device to send Its beacon. All devices, which are active, listen to the beacon period and update their BSRI on hearing beacons from neighboring devices. BSRI vary from one to other superframe as it is dynamically determined on the basis of receiving beacons from other devices and the BSRI is used by other devices receiving this beacon to decide the free slots for beaconing.
The New Beacon Information Element (NBIE) contains the information of a new beacon received from a new device. NBIE includes the New Device's DEVID and beacon slot number in which the new beacon received where the said IE can include information about more than one new beacon.
The Expected Beacon Slot Information Element (EBSIE) indicates loss of expected beacon from a device in specific beacon slot, EBSIE includes DEVID of the device from which beacon is missed and beacon slot number of that device,
DEVID structure which uses superframe structure has grouped beacon in BP with several beacon slots where the structure includes Byte 1 which is 8 bit reduction of 64 bit MAC address of the device and Byte 0 which is 8 bit, and represents a beacon slot number in which device is sending a beacon. The slot in which the device is sending beacon is unique across the 2 hop neighborhood and slot number is used as a parameter in generating unique DEVID for the devices. The new DEVID structure includes a Byte 1 which is 8 bit reduction of 64 bit MAC address of the device and Byte 0 which is 8 bit obtained from MAS number in which device is sending a beacon.

Accordingly this invention also explains a method for sending beacons in wireless personal area networks having a medium access control mechanism wherein the said method comprising the steps of:
(a) BSRI Updation;
(b) Network joining and Beaconing Procedure;
(c) Beacon Collision Detection due to network joining where when a device that sends its first beacon does not get New Beacon IE from its neighbor with new device's information, resulting in a collision at the time of joining;
(d) Beacon Collision Detection due to device movement when there is a
possibility of collision of beacons because of movement of device; and
(e) a new beacon collision resolution procedure Random Slot Selection (RSS)
where the device, which suffers from beacon collision, skips the random numbers of
free beacon slot before start sending its beacon again.
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The device updates its own BSRI before sending it in its beacon and before updating BSRI, device listens to the entire beacon between times, when it had sent its last beacon in previous superframe and current time, BSR! updation comprising the steps of: initializing own BSRI bitmap with all zero; marking bit position as OBS in the BSRI bitmap, where device has received the beacon from other neighboring devices; marking bit position as MBS in the BSRI bitmap, the slot where device is going to send the beacon in next superframe; and marking bit position as EBS if device has received the beacon last superframe and expecting in this superframe but did not receive. For network joining, the device uses BSRIs from neighboring devices and when device which is trying to join the network starts listening for the beacons around it and if the device is within the range of some other devices that are already beaconing, then it receives some beacons else it will receive no beacons. The device is in receiving mode for an extended period which is at least the whole superframe period and when no beacons are received, the device chooses any of the slots from within the available beacon slots in the BP for its beacon. When the device initializes its BSRI with all bit pairs as VBS and marks its beacon slot with MBS in the BSRI the device begins transmitting its beacon with this BSRI. When one or more beacons are received, the device determines the parameters {BSRI) of the superframe from the received beacons and the device logically OR all the received BSRIs from the received beacons. From the resultant ORed BSRI's bitmap, the device decides a random VBS slot number and in next superframe, this device starts sending its beacon with updated BSRI and the
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device always updates its BSRI before sending it in beacon. If no vacant slot is present, then the device does not start beaconing and waits for some random amount of time before starting again the network joining procedure. When a device in network, receives a beacon from a device for first time then the device which has received new beacon sends New Beacon IE in its superframe with information about the new beacon and device, which is sending that beacon. If device stops getting beacon in the slot in which, it was listening a beacon earlier then it sends that slot as BBS up to mMaxLosf Beacons counter, after that device marks thai slot as VBS.
On Beacon Collision at network joining the device starts listening to beacon period just after sending its own beacon till the end of BP and in next superframe it listens till again, it reaches to its own slot to send the beacon. The device checks received beacons from different neighboring devices with BSRI in which the slot marked as OBS in the slot, in which the device itself has sent its first beacon. If device does not get a New Beacon IE with its information in that beacon slot with beacon from some neighboring device, then it is a collision of beacon. If there is no collision, then device creates its own BSRI and continue it's processing of sending beacons. If a collision of beacon is detected, then both devices, whose beacon have collided, does not send next beacon and try to resend beacon.
On Beacon Collision due to device movement the device, which detects the collision, expects a beacon in the slot, but it does not get anything in case of collision where it changes the slot value to EBS (Beacon expected but not received) in the BSRI which is being sent by it. The devices which sent a beacon in that slot find out and know that the beacon they sent was not received; a collision occurs, A device which discovers that its beacon was not received by neighboring devices, checks to see if the neighborhood is the same or has it gone away from it by detecting from the identity of the devices whose beacons it received in the slots in previous superframe, if the device finds out that its neighborhood has changed then it is determined that this device ventured out into the zone of other devices. If EBSIE is received by a device with information of its own DEViD and beacon slot number It indicates that, its tDeacon did not reach one of the neighbor. If EBSIE is received by a device with information of its own beacon slot number but some other DEVID, it indicates to the device that, the slot has been reserved by some other device and there is a collision of beacon in the slot.
In collision resolution procedure Random Slot Skip (RSS), the device is adapted to send first beacon, when device has suffered from beacon collision while sending its beacon. After detecting the collision, device decides a random number CW, which must
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be in between CWmin and CWmax. The Device has to "skip" CW number of free slots in BP before introducing its beacon again in BP, which spans more than one superframe. The device is adapted to continuously update BSRI information received from its neighbors by listening to all the beacons. The device OR all BSRIs and count the free slots to find out CW numbers of slots has been skipped. After skipping CW numbers of slots, device introduces its beacon in next free slot and checks, if its beacon has been sent successfully. If there Is no collision, then device continues sending its tseacon in selected slot- If collision is detected after RSS procedure, then device increments the CWmin value where new CWmin is greater than or equal to CW. After selecting new CWmin and using existing CWmax, device selects random CW between CWmin and CWmax. The new device performs RSS procedure and on each beacon collision situation, CW will keep increasing. If (CWmax - CWmin) is less than CWmindur (Contention window minimum duration) then device stops its back-off procedure and avoid retrying for random amount of time and then start its procedure of beacon sending.
The other objects, features and advantages of the present invention will be apparent from the accompanying drawings and the detailed description as follows.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 illustrates the WPAN as a decentralized and distributed ad-hoc network system and range of all devices;
Figure 2 illustrate the superframe structure in current art, which includes MAS and beacon periods;
Figure 3 illustrate the proposed superframe structure, in which all the beacons are grouped together at the start of the superframe;
Figure 4 illustrates the structure of the proposed Beacon Slot Reservation Indicator (BSRI);
Figure 5 illustrates the structure of New Beacon Information Element (NBIE);
Figure 6 illustrates the structure of Expected Beacon Slot Information Element (EBSIE);
Figure 7 depicts the network topology for the beacon collision situation at the time of network joining;
Figure 8 shows the snap shot of the superframe at the time of beacon collision;
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Figure 9 shows network topology for the beacon collision due to movement of the device in decentralized/distributed WPAN;
Figure 10 illustrates the structure of DEVID, where one of the elements of DEVID is beacon slot number, where beacon of the device is sent; and
Figure 11 illustrates the structure of DEVID, where one of the elements of DEVID is number from MAS number, where beacon of the device is sent.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a system that allows an improved medium access control in the decentralized Wireless Personal Area Networks based on mobile ad'hoc networks.
The invention relates to system and method which allows device to join the network and send ttie beacons by employing mechanisms for beacon collision avoidance, if tieacon collision occurs due to movement of device or at the time of joining of the network, then collision detection method and collision resolution method.
The system for the invention comprises of a new medium access control mechanism involving a new superframe structure, a new element in beacon frame called Beacon Slot Reservation Indicator (BSRI), New Beacon Information Element, method for joining network using information provided in BSRI, beacon collision detection method using BSRI and New Beacon Information Element, and collision resolution procedure named Random Slot Skip (RSS) Procedure.
The subsequent subsections describe the individual entities to effect the invention:
1. Figure 3 illustrates the proposed new superframe structure. Superframe structure of the Invention has following characteristics:
- All beacons are grouped at the start of the superframe.
- Total numbers of beacons slots may or may not be fixed (For example, 256 beacons slots). The choice for any other number does not affect the operation of the invention.
Remaining period as data period (for example, 256 data slots). This number can be set depending on the actual number of devices in the current network configuration, and it does not affect the operation of the invention.
Superframe is composed of 2 periods:
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- Beacon Period: This period is present at the beginning of the superframe and is divided into several beacon slots (256 for the example). Each device in network broadcasts its beacon in one of these beacon slots.
- Data Period (DP): Data Period follows the beaconing period and is divided into several (for example, 256) data slots. These data slots can be reserved tor data transfer in peer-to-peer manner.
All the beacons are sent during the BP, one beacon in one beacon slot by a device. Every device will send a beacon such that it should not collide with other neighboring device's beacons. Data slots may require reservation by the devices for their use.
2. Figure 5 illustrate structure of New Beacon Information Element (NBIE). NBIE contains the information a new beacon received from a new device. As shown in Figure 5, NBIE includes the New Device's DEVID and beacon slot number in which the new beacon received. This IE can include information about more than one new beacon.
3. Figure 6 illustrate structure of Expected Beacon Slot Information Element (EBSIE). EBSIE contains the information of loss of beacon from particular devices. It includes the DEVID of the device whose beacon has been missed and beacon slot number. This IE can include information about more than one new beacon.
4. Figure 10 illustrates the proposed new DEVID structure which uses superframe structure proposed in the invention, which shows grouped beacon in BP with several (for example, 256) beacon slots. Structure includes the following elements:

- Byte 1 is 8 bit reduction of 64 bit MAC address of the device.
- Byte 0 is 8 bit, and represents a beacon slot number in which device is sending a beacon. The slot in which the device is sending beacon is unique across the 2 hop neighborhood. Hence slot number can be used as a parameter in generating unique DEVID for the devices.
5. Figure 11 illustrates the proposed new DEVID structure. Structure includes the
following elements:
- Byte 1 is 8 bit reduction of 64 bit MAC address of the device.
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- Byte 0 is 8 bit obtained from MAS number in which device is sending a beacon.
The subsequent subsections describe the operation of the invention:
1. BSRl Updation
Device always updates its own BSRl before sending it in its beacon. Before updating BSRl, device listens to the entire beacon between times - when it had sent its last beacon in previous superframe and current time (i.e. just before sending its beacon again in this superframe).
1) Initialize own BSRl bitmap with all zero
2) Mark bit position as OBS in the BSRl bitmap, where device has received the beacon from other neighboring devices.
3) Mark bit position as MBS in the BSRl bitmap, the slot where device is going to send the beacon in next superframe.
4) Mark bit position as EBS if device has received the beacon last superframe and expecting in this superframe but did not receive.
2. Networking joining and Beaconing Procedure
Network joining procedure in the current art uses BPOIE from neighboring devices and it includes procedure of new beacon period creation, if free slot is not available in existing beacon period. In our proposed inventive method for network joining, the device uses BSRIs from neighboring devices.
Proposed procedure, in the present invention, for a device to join network is explained in following steps:
1} Device which is trying to join the network starts listening for the beacons around it. If the device Is within the range of some other devices that are already beaconing, then it receives some beacons else it will receive no beacons- The device should be in receiving mode for an extended period which is at least the whole superframe period.
2) In case no beacons are received, the device can choose any of the slots from within the available beacon slots (for example, 256) in the BP for its beacon. The device initializes its BSRl with all bit pairs as VBS (00) (since no beacons are being received in those slots) and marks its beacon slot with MBS (11) in the BSRl, The device begins transmitting its
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beacon with this BSRI.
3) In case one or more beacons are received, the device determines the parameters (BSRI) of the superframe from the received beacons. The device should logically OR all the received BSRIs from the received beacons.
4) From the resultant ORed BSRI's bitmap, the device decides a random VBS slot number. In next superframe, this device starts sending its beacon with updated BSRI. Device should always update its BSRI before sending it in beacon.
5} If no vacant slot is present, then the device cannot start beaconing and hence waits for some random amount of time before starting again the ■network joining procedure.
When a device in network, receives a beacon from a device for first time, i.e. it has not received any beacon from that device in same beacon slot previously, then the device which has received new beacon should send New Beacon IE in its superframe with information about this new beacon and device, which is sending that beacon.
If device stops getting beacon in the slot in which, it was receiving a beacon earlier then it should send that slot as EBS up to mMaxLostBeacons counter, after that device should mark that slot as VBS.
3. Beacon Collision Detection (Beacon Collision at network joining)
This situation may arise when two devices choose the same slot after listening to the channel and decide to beacon in the same slot. Figure 5 displays the topology for this type of beacon collision. New device had sent its first beacon in randomly selected slot, according to procedure as described in previous sections. After that, following procedure is required for collision detection.
Device starts listening to beacon period just after sending its own beacon till the end of BP and in next superframe it listens till again, it reaches to its own slot to send the beacon. Device checks received beacons from different neighboring devices with BSRI in which the slot was marked as OBS in the slot, in which the device itself has sent its first beacon. If device does not get a New Beacon IE with its information in that beacon slot with beacon from some neighboring device, then it means that there is a collision of beacon. Figure 7 illustrates the superframe snap shot at the time of collision.
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If there is no collision, then device should create its own BSRI and continue it's processing of sending beacons using procedure as described earlier.
If a collision of beacon has been detected, then both devices, whose beacon have collided, should not send next beacon and try to resend beacon by Random Slot Skip Procedure, which is described in following sections.
4, Beacon Collision Detection (Beacon Collision due to device movement).
This situation may arise when a mobile device moves away from its zone and enters a zone away from its two hop neighborhood. The beacon slot reservation is only guaranteed up to two hops by the BSRI and hence with this movement of the device, its beacon may now collide with some other beacons of the devices in this zone. Figure 9 illustrates the situation of collision due to device movement.
This collision can be detected by the other devices in the network. Device, which detects the collision, is expecting a beacon in the slot, but it does not get anything in case of collision shown in figure 9. So it changes the slot value to EBS (Beacon expected but not received) in the BSRI which is being sent by it. The devices which sent a beacon in that slot find out and know that the beacon they sent was not received, this situation can be because of collision.
A device which discovers that its beacon was not received by neighboring devices, checks to see if the neighborhood is the same or has gone away from it (changed). This can be detected from the identity of the devices whose beacons it received in the slots in previous superframe. If the device finds out that its neighborhood has changed then it is determined that this device ventured out into the ^one of other devices, at least 2 hops separated from its original position.
If EBSIE is received by a device with information of its own DEVID and beacon slot number, it indicates that its beacon did not reach one of the neighbors. If EBSIE is received by a device with information of its own beacon slot number but some other DEVID, it indicates to the device that, the slot has been reserved by some other device and there is a collision of beacon in the slot.
This device which finds that it has moved from its location should go for collision resolution. For collision resolution, it should use the proposed Random
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Slot Skip Procedure, which is described in following sections. The device, whose neighborhood has not changed, should continue its process of sending beacon without going for collision resolution.
5, Beacon Collision Resolution (Random Slot Skip Procedure)
This procedure is proposed for sending first beacon by the device, when device had suffered from beacon collision while sending its beacon, as described in previous section. Following steps describes the procedure in detail.
1) After detecting the collision, device decides a random number CW, which must be in between CWmin and CWmax.
2) Device has to "skip" CW number of free slots in BP before introducing its beacon again in BP, which may span more than one superframe.
3) For this procedure, device should continuously update BSRI information received from its neighbors by listening to all the beacons. Device should OR all BSRIs and should count the free slots to find out that, CW numbers of slots has been skipped.
4) After skipping CW numbers of slots, device should introduce its beacon in next free slot. Also it should check, if its beacon has been sent successfully as described in beaconing procedure in above sections.
5) If there is no collision, then device can continue sending its beacon in selected slot as described in beaconing procedure.
If collision is detected again after RSS procedure, as described in collision detection procedure, then device should increment the CWmin value up to CW or more then that. So, new CWmin >= CW, After selecting new CWmin and using existing CWmax, device should select random CW between CWmin and CWmax. New device should perform RSS procedure again. On each beacon collision situation, CW will keep on increasing. If {CWmax - CWmin) is less, CWmindur (Contention window minimum duration) then device should stop its back-off procedure and should avoid retrying for random amount of time and then can start its procedure of beacon sending again as specified in above sections.
Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention.
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GLOSSARY OF TERMS AND DEFINITONS THEREOF
ASIE: Application Specific Information Element
BP: Beacon Period
BPOIE: Beacon Period Occupancy Information Element
BPST: Beacon Period Start Time
BSRI: Beacon Slot Reservation Indicator
CW: Contention Window
DEVID: Device Identifier
DP: Data Period
DRP: Distributed Reservation Protocol
DS: Data Slot
DSRI: Data Slot Reservation Indicator
EBS: Expected Beacon Slot
IE". Information Element
MAC: Medium Access Control
MAS: Medium Access Slot
MBOA: Multi Band OFDM Alliance
MBS: My Beacon Slot
N0IE: New Beacon Information Element
OBS: Other's Beacon Slot
OFDM: Orthogonal Frequency Division Multiplexing
PSIE: Power Save Information Element
RSS: Random Slot Skip
UWB: Ultra Wide Band
VBS: Vacant Beacon Slot
VSIE: Vendor Specific Information Element
WPAN: Wireless Personal Area Network
EBSIE: Expected Beacon Slot Information Element
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WE CLAIM
1. A system for sending beacons in wireless personal area networks having a medium
access control mechanism, the said system comprising:
a superframe structure, having each beacon sent by each device are grouped at the start of the superframe and remaining period used as data period -where the data period is further divided in plural data slots;
a beacon frame structure, including an information element called Beacon Slot Reservation Indicator (BSRI) which contains the information about all the occupied beacon slots from the reference of the device which is sending the beacon;
an information element, New Beacon Information Element (NBIE) where if devices hear a beacon from a neighboring device for the first time, then it sends New Beacon IE in its beacon as an Indication of the New Device joining;
an information element. Expected Beacon Slot Information Element (EBSIE) where device misses a beacon from a device from which it has received earlier, then it sends EBSIE in its beacon; and
new DEVID structure, for addressing using information of device's fylAC address and beacon slot number where device is sending its beacon and also by using information of device's MAC address and number obtained from MAS number where device is sending its beacon.
2. A system as claimed in claim 1, wherein in the superframe structure, all beacons are grouped at the start of the superframe and the total numbers of beacons slots can be variable.
3. A system as claimed in claim 1, wherein the superframe is composed of 2 periods:
Beacon Period which is present at the beginning of the superframe and is divided into several beacon slots where each device in network broadcasts its beacon in one of these beacon slots; and
Data Period (DP) where the said Data Period follows the beacon period and is divided into several data slots where this data slots is reserved for data transfer.
4. A system as claimed in claim 1, wherein all the beacons are sent during the BP, one
beacon in one beacon slot by a device and each device sends a beacon such that it
does not collide with other device's beacons.
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5. A system as claimed in claim 1, wherein the beacon frame structure contains some
mandatory information and some optional information where the mandatory information
comprise;
a BSRI (Beacon Slot Reservation Indicator) which indicates the beacon slots of the neighboring devices;
a DSRI (Data Slot Reservation Indicator) which indicates the information of the data slot reservations;
wherein the beacon optionally contain IE (Information Elements) where the available IE are
DS-Req IE: Data Slot Request IE
DS-Res IE: Data Slot Response IE
NBIE: New Beacon IE
EBSIE: Expected Beacon Slot IE
SPSG-Req IE: Synchronized PS Group Request IE
PSIE: Power Save IE
VSIE: Vendor Specific IE
ASIE: Application Specific IE.
6. A system as claimed in claim 5 wherein BSRI is the information about all the beacon slots from the reference of the device which is sending the beacon.
7. A system as claimed in claim 5 wherein BSRI consists of a bitmap which assigns 2 bits for the information of each of the possible beacon slots that are present in the BP of the superframe where the possible status of the beacon slot are VBS, EBS, OBS, MBS.
8. A system as claimed in claim 7 wherein VBS is a Vacant Beacon Slot, for no beacon received in this slot number, EBS is an Expected Beacon Slot, means beacon expected but not received in this slot, OBS is Other's Beacon Slot indicating beacon received from some device in this slot and MBS is My Beacon Slot indicating the slot used by the device to send its own beacon,
9. A system as claimed in claim 5 wherein each active device listens to the beacon period and update their BSRI on hearing beacons from neighboring devices.
10. A system as claimed in claim 5 wherein BSRI vary from one to other superframe as it is dynamically determined on the basis of receiving beacons from other devices and the
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BSR! is used by other devices receiving the beacon to decide the free slots for transmitting beacon.
11. A system as claimed in claim 1 wherein the New Beacon Information Element (NBIE) contains the information of a new beacon other than received in earlier superframe from a new device in neighborhood.
12. A system as claimed in claim 11 wherein NBIE includes the New Device's D£VID and beacon slot number in wtiich the new beacon received where the said IE can include information about more than one new beacon.
13. A system as claimed in claim 1 wherein the Expected Beacon Slot Information Element (EBSIE) contains the information of the missed beacon which was received in earlier superframe from a device in neighborhood.
14. A system as claimed in claim 13 wherein EBSIE includes the DEVID of the device from which the beacon has been missed and beacon slot number of that,
15. A system as claimed in claim 1 wherein DEVID structure which uses superframe structure has grouped beacon in BP with several beacon slots.
16. A system as claimed in claim 15 wherein the slot in which the device is sending beacon is unique across the 2 hop neighborhood and slot number is used as a pafameter in generating unique DEVID for the devices.
17. A system as claimed in claim 15 wherein the new DEVID structure includes one of the byte, which is 8 bit reduction of 64 bit MAC address of the device and another byte is obtained from MAS number in which device is sending a beacon,
18. A method for sending beacons in wireless personal area networks having a medium access control mechanism wherein the said method comprising the steps of:
BSRI Updation;
Network joining and Beaconing Procedure;
Beacon Collision Detection due to network joining where when a device that sends its first beacon does not get New Beacon IE from its neighbor with new device's information, resulting in a collision at the time of joining;
Beacon Collision Detection due to device movement when there is a possibility of collision of beacons because of movement of device; and
a new beacon collision resolution procedure Random Slot Selection (RSS) where the device, which suffers from beacon collision, skips the random numbers of free beacon
22

slot before start sending its beacon again,
19. A method as claimed in claim 18 wherein the device updates its own BSRI before sending it in its beacon and before updating BSRI, device listens to the entire beacon period.
20- A method as claimed in claim 18 wherein the said BSRI updation comprising the steps of:
inilializtng own BSRI bitmap with ail zero;
marking bit position as OBS in the BSRI bitmap, where device has received the beacon from other neighboring devices;
marking bit position as MBS in the BSRI bitmap, the slot where device is going to send the beacon in next superframe; and
marking bit position as EBS if device has received the beacon last superframe and expecting in this superframe but did not receive.
21. A method as claimed in claim 18 wherein for network joining, the device uses BSRIs from neighboring devices and when device which is trying to join the network starts listening for the beacons around it and if the device is within the range of some other devices that are already beaconing, then it receives some beacons else it will receive no beacons,
22. A method as claimed in claim 18 wherein the device is in receiving mode for an extended period which is at least the whole superframe period and when no beacons are received, the device chooses any of the slots from the available beacon slots in the BP for its beacon.
23. A method as claimed in claim 18 wherein when the device initializes its BSRI with all bit pairs as VBS and marks its beacon slot with MBS in the BSRI the device begins transmitting its beacon with this BSRI.
24. A method as' claimed in claim 18 wherein when one or more beacons are received, the device determines the parameters of the superframe from the received beacons, and the device logically OR alt the received BSRIs from the received beacons.
25. A method as claimed in claim 18 wherein from the resultant ORed BSRI's bitmap, the device decides a random VBS slot number and in next superframe, this device starts sending its beacon with updated BSRI and the device always update its BSRI before sending it in beacon.
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26. A method as claimed in claim 18 wherein if no vacant slot is present, then the device does not start beaconing and waits for some random amount of time before starting again the network joining procedure.
27. A method as claimed in claim 18 wherein when a device in network, receives a beacon from a device from which the device has not received beacon earlier then the device which has received new beacon sends New Beacon IE in its superframe with information about the new beacon and device, which is sending that beacon.
28. A method as claimed in claim 18 wherein if device stops getting beacon in the slot in which, it was listening a beacon earlier then it sends that slot as EBS up to mMaxLostBeacons superframes, after that device marks that slot as VBS,
29. A method as claimed in claim 18 wherein on Beacon Collision at network joining, the device starts listening to beacon period just after sending its own beacon till the end of BP and in next superframe it listens till again, it reaches its own slot to send the beacon.
30. A method as claimed in claim 29 wherein the device checks received beacons from different neighboring devices with BSRI in which the slot marked as OBS in the slot, in which the device itself has sent its first beacon.
31. A method as claimed in claim 29 wherein if device does not get a New Beacon IE with its information in that beacon slot with beacon from some neighboring device, then it is a collision of beacon.
32. A method as claimed in claim 29 wherein if there is no coiiision, then device creates its own BSRI and continue its process of sending beacons.
33. A method as claimed in claim 29 wherein if a collision of beacon is detected, then both devices, whose beacon has collided, does not send next beacon and try to resend beacon.
34. A method as claimed in claim 18 wherein on beacon collision due to device movement the device, which detects the collision, expects a beacon in the slot, but it does not get anything in case of collision where it changes the slot value to EBS (Beacon expected but not received) in the BSRI which is being sent by it,
35. A method as claimed in claim 18 wherein if EBSIE is received by a device with information of its own DEVID and beacon slot number, it Indicates that its beacon did not reach one of the neighbors. If EBSIE is received by a device with information of its own beacon slot number but some other DEVID. it indicates to the device that the slot has been reserved by some other device and there is a collision of beacon in the slot.
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36. A method as claimed in claim 34 wherein the devices which sent a beacon in that slot find out and know that the beacon they sent was not received; a collision occurred.
37. A method as claimed in claim 34 wherein if the device finds out that its neighborhood has changed then it is determined that this device ventured out into the zone of other devices,
38. A method as claimed in claim 18 wherein in collision resolution procedure Random Slot Skip (RSS), the device is adapted to send first beacon, when device has suffered from beacon collision while sending its beacon.
39- A method as claimed in claim 38 wherein after detecting the collision, device.decides a random number CW, which must be in between CWmin and CWmax,
40. A method as claimed in claim 39 wherein the device has to skip CW number of free slots in BP before introducing its beacon again in BP, which can span more than one superframe.
41. A method as claimed in claim 39 wherein the device is adapted to continuously update BSRI information received from its neighbors by listening to all the beacons during RSS procedure,
42. A method as claimed in claim 39 wherein the device OR all BSRIs and count the free slots to find out CW numbers of slots has been skipped.
43. A method as claimed in claim 39 wherein after skipping CW numbers of slots, device introduces its beacon in next free slot and checks, if its beacon has been sent successfully,
44. A method as claimed in claim 39 wherein if there is no collision, then device'continues sending its beacon in selected slot.
45. A method as claimed in claim 39 wherein if collision is detected after RSS procedure, then device increments the CWmin value where new CWmin is greater than or equal to CW.
46. A method as claimed in claim 39 wherein after selecting new CWmin and using existing CWmax. device selects random CW between CWmin and CWmax.
47. A method as claimed in claim 39 wherein the new device perform RSS procedure and on each beacon collision situation, CWwill keep increasing.
48. A method as claimed in claim 39 wherein if (CWmax - CWmin) is less than CWmindur (Contention window minimum duration) then device stops its back-off procedure and
25

I
avoids retrying for random amount of time and then starts sending beacon by joining the network again.
49. A system for sending beacons in wireless personal area networks tiaving a medium
access control mechanism substantially as herein described particularly with reference to
the drawings.
50. A method for sending beacons in wireless networks having a medium access control
mechanism substantially as herein described particularly with reference to the drawings.

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Documents:

0417-che-2004 abstract duplicate.pdf

0417-che-2004 abstract.jpg

0417-che-2004 abstract.pdf

0417-che-2004 claims duplicate.pdf

0417-che-2004 claims.pdf

0417-che-2004 correspondence-others.pdf

0417-che-2004 correspondence-po.pdf

0417-che-2004 descrption (complete) duplicate.pdf

0417-che-2004 descrption (complete).pdf

0417-che-2004 drawings.pdf

0417-che-2004 form-1.pdf

0417-che-2004 form-13.pdf

0417-che-2004 form-18.pdf

0417-che-2004 form-26.pdf

0417-che-2004 form-5.pdf

0417-che-2004 form-9.pdf

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Patent Number

229596

Indian Patent Application Number

417/CHE/2004

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

18-Feb-2009

Date of Filing

06-May-2004

Name of Patentee

SAMSUNG INDIA SOFTWARE OPERATIONS PRIVATE LIMITED

Applicant Address

BAGMANE LAKEVIEW, BLOCK 'B', NO. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,

Inventors:

#	Inventor's Name	Inventor's Address
1	SUNIL JOGI	BAGMANE LAKEVIEW, BLOCK 'B', NO. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR, BYRASANDRA, BANGALORE - 560 093,
2	PRASHANTH WASON	BAGMANE LAKEVIEW, BLOCK 'B', NO. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR, BYRASANDRA, BANGALORE - 560 093,
3	BALAJI SRINIVAS HOLUR	BAGMANE LAKEVIEW, BLOCK 'B', NO. 66/1, BAGMANE TECH PARK, C V RAMAN NAGAR, BYRASANDRA, BANGALORE - 560 093,
4	HOLUR, BALAJI SRINIVAS	J.P. TECHNO PARK, 3/1, MILLERS ROAD, BANGALORE 560 052,
5	CHOUDHARY, DR. MANOJ	J.P. TECHNO PARK, 3/1, MILLERS ROAD, BANGALORE 560 052,
6	ARUNAN, THENMOZHI	J.P. TECHNO PARK, 3/1, MILLERS ROAD, BANGALORE 560 052,
7	KUMAR, VIVEK	J.P. TECHNO PARK, 3/1, MILLERS ROAD, BANGALORE 560 052,

PCT International Classification Number

H04L12/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA