Title of Invention	SYSTEM AND METHOD FOR DEVICE HANDOVER IN WIRELESS PERSONAL AREA NETWORKS
Abstract	ABSTRACT This invention relates to the field of wireless mobile ad-hoc networks. More specifically the invention relates the system and method for device handover from child PNC to parent PNC, when device is part of child piconet and also in range of parent piconet and device handover from parent PNC to child PNC, when device is part of parent piconet but moved out of the range of parent PNC but still present in range of child PNC of that parent PNC. The system and method by using facilities of current art and by inventing new method in form of signaling MSC (Message Sequence Charts) of device handover of type child to parent piconet and parent to child piconet. This invention also defines the required commands for invention and content for those commands.

Title of Invention

SYSTEM AND METHOD FOR DEVICE HANDOVER IN WIRELESS PERSONAL AREA NETWORKS

Abstract

ABSTRACT This invention relates to the field of wireless mobile ad-hoc networks. More specifically the invention relates the system and method for device handover from child PNC to parent PNC, when device is part of child piconet and also in range of parent piconet and device handover from parent PNC to child PNC, when device is part of parent piconet but moved out of the range of parent PNC but still present in range of child PNC of that parent PNC. The system and method by using facilities of current art and by inventing new method in form of signaling MSC (Message Sequence Charts) of device handover of type child to parent piconet and parent to child piconet. This invention also defines the required commands for invention and content for those commands.

Full Text	FIELD OF TECHNOLOGY This invention relates to the field of wireless mobile ad-hoc networks. Further, this invention relates to device handover procedure for wireless personal area networks that are based on wireless mobile ad-hoc networks. Particularly, this invention relates to the effective mechanisms of handing over the device from child piconet to parent piconet and parent piconet to child piconet in the centralized wireless personal area networks. More particularly, this invention encompasses a system and method for device handover 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. at a distance of approximately 10 meters. The IEEE (http://www.ieee.org) 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. Medium Access Control mechanisms to deal with such high data rates are currently being discussed in IEEE draft P802.15.3/D17. The medium access control mechanisms broadly include how a device may join the network, how it can transfer data at the required rate to another device, how the medium is best used etc. Figure 1 illustrates the IEEE-802.15.3 based wireless personal area network. It involves a network referred as piconet, in which a device may act as coordinator (referred as piconet coordinator or PNC herein). The PNC performs the functions of allowing a device (referred as DEV) to join, allocating it a channel (time slot) to transmit to another device, synchronization mechanisms etc. This is a centralized WPAN system which is formed in an ad-hoc fashion. Dependant piconet is a piconet that exists entirely within a channel time allocation of another piconet, the parent piconet. Child piconet is a subtype of dependant piconet that exists entirely within a channel time allocation of another piconet, the parent piconet, is controlled by a device that is a member of the parent piconet. Neighbor piconet is also a subtype of dependant piconet that exists entirely within a channel time allocation of another piconet, the parent piconet, is controlled by a device that is not a member of the parent piconet. A child piconet is one that is formed under an established piconet. The established piconet then becomes the parent piconet. The child piconet functionality is useful for either extending the area of coverage of the piconet or shifting some computational or memory requirements to another PNC capable device. It is possible for the parent piconet to have more than one child piconet. In addition, it is also possible for a child PNC to allow a child piconet as a part of its own piconet. The child piconet uses a distinct piconet ID (PNID) and acts as an autonomous piconet except that it is dependent on a private CTA from the parent piconet. Association and security membership for the child piconet are handled within the child piconet and do not involve the parent PNC. The child PNC is a member of the parent piconet and thus is able to exchange data with any DEV in the parent piconet. The child PNC is also a member of the child piconet and thus is able to exchange data with any DEV in the child piconet. The invention also considers the Indian patent application bearing application No. 221/CHE/2004 titled "SYSTEM AND METHOD FOR MEDIUM ACCESS CONTROL IN WIRELESS MOBILE AD-HOC NETWORKS" as part of current art. Superframe structure described in that patent document is an enhanced superframe which is specified in IEEE draft P802.15.3/D17. Figure 2 illustrates the superframe structure. Superframe is channel distribution specified by the PNC among the DEVs in piconet. It is informed to DEVs through beacon frame, which is being broadcasted by PNC. Superframe is composed of 3 parts: 1. Beacon: It is used to set the timing allocations and to communicate management Information for the piconet. All the associated devices listen to this beacon. 2. Contention access period (CAP): It is used to communicate commands from the DEV to PNC or vice versa. It may also be used for asynchronous data if it is present in the superframe. The length of the CAP is determined by the PNC and communicated to the DEVs in the piconet via the beacon. The CAP uses CSMA/CA protocol for the medium access. 3. Channel time allocation period (CTAP): It consists of channel time allocations (CTAs), including management CTAs (MCTAs). CTAs are used for commands, isochronous streams and asynchronous data connections. A PNC may choose to use MCTAs instead of the CAP for sending command frames, unless otherwise restricted by the physical layer (PHY). An open MCTA is one where the SrcID is the BcstID; Any DEV that is associated in the piconet may attempt to send a command frame to the PNC in an open MCTA. An MCTA with the UnassocID as the SrcID is an association MCTA. Any DEV not currently associated in the piconet may attempt to send an Association Request command to the PNC in an association MCTA. Device Access Period (DAP): DAP is used by all the associated DEVs in piconet to send their respective heart beat frames. By listening to the heart beat frames as contained in DAP, it is possible for a first associated device to know exactly whether a second associated device is in range(reachable) or not, depending upon whether the first associated device was able to listen to the heart beat frame sent by the second associated device in the DAP. The CTAP, in contrast to CAP, uses a standard TDMA protocol where the devices (DEVs) have specified time windows which are called the CTAs. MCTAs are either assigned to a specific source/destination pair for management traffic and use TDMA for access or they are shared MCTAs that are accessed using the slotted aloha protocol. Beacon frame is illustrated in figure 3. Information Elements (lEs) in figure 3 are encoded in type, length, value format. The lEs in the beacon payload may appear in any order except for the channel time allocation (CTA) lEs, which is the first IE of the beacon payload following the piconet synchronization parameters field. CTA IE consists of information about the CTAs in the superframe. Figure 4 shows the structure of ADIE. Heart beat frame is a very small MAC frame which is always broadcasted by all the associated DEVs in the piconet. Format of the heart beat frame in the current art is illustrated in figure 5. One of purpose of the heart beat frame is to advertise its own presence of its neighbors and PNC. Associated Devices Information Element (ADIE) is broadcasted by the PNC to all the devices in the piconet. Usage of the ADIE is to provide the information to all the devices to schedule their heart beat frames in DAP. This information element must be sent with beacon if there is at least one device associated with the PNC. LIMITATIONS The present state of art in this field, as discussed in IEEE 802.15.3 (http://www.ieee.org) and as described in above mentioned patent, has certain limitations, namely, there is no mechanism when a device in child piconet is also in range of parent piconet and can effectively become a part of parent piconet and release resources for child PNC. Consequently, if there is no device left in child piconet then operation of child piconet can be terminated. Also, there is no mechanism for joining a child piconet by a device, when device in parent piconet moves out of the range of the parent PNC but still in range of child PNC. Stating same at broad level, there is no mechanism for device handover from child to parent piconet and parent to child piconet in current art. Currently in the medium access control mechanism as defined in current art; there is no mechanism for the following: 1. When device in child piconet is in radio range of parent piconet also, then there is no mechanism, that parent PNC can take over the device, associate the device with itself (Parent PNC) and child PNC can disassociate the device from itself (Child PNC); 2. When device in parent piconet moves out of the radio range of parent PNC, but if it is still in range of child PNC of the parent piconet, then there is no mechanism for child to become a part of child piconet without disassociation because of ATP timeout and scanning procedure again; and 3. In other words, current art does not provide the method for device handover from child to parent PNC and parent to child PNC. OBJECTS OF THE INVENTION The primary object of the invention is to provide a system and method for device handover from child to parent PNC and parent to child PNC in medium access control for the UWB wireless personal area networks, which are based on wireless ad-hoc networks, in a centralized network topology. It is another object of the invention to provide a mechanism where the device in child piconet is in radio range of the parent PNC then parent PNC and child PNC can communicate with each other and parent PNC can take over the charge of the device and child PNC can disassociate the device from child piconet. It is another object of the invention to provide the mechanism for device handover from child to parent PNC, in which device does not require disassociating itself from child PNC by initiating disassociation process, it does not require scanning and it does not require sending association request for associating itself with parent PNC. It is another object of the invention to provide a mechanism for where the device moves out of the radio range of the parent PNC but it is still in radio range of the child PNC, then parent PNC and child PNC can communicate with each other and child PNC can take over the charge of the device and parent PNC can disassociate the device from parent PNC. It is another object of the invention to provide the mechanism for device handover from parent to child PNC, in which device does not require to disassociate itself from parent PNC because of ATP timeout. SUMMARY OF THE INVENTION The present invention relates to a system that provides the mechanism of device handover from child to parent piconet and parent to child piconet in the Wireless Personal Area Networks based on mobile ad-hoc networks. In detail, the present invention provides the mechanism of device handover from child to parent and vice versa, without device to be disassociated from its PNC, so this handover is handled by coordination between child and parent PNCs. The present invention comprises of system and method which would overcome the inability of device handover with current art, in the following manner: There are two scenarios for device handover. One is device handover from child to parent PNC and other is device handover from parent to child PNC. 1. Device handover from Child to Parent PNC Figure 6 displays the topology for child to parent PNC handover of the device which is part of child PNC, and also it is in range of parent PNC. The present invention uses some mechanisms provided by current art to achieve the objectives of invention, so parent PNC is able to hear the heart beat of the device which is in range of parent PNC. The mechanism of the present invention defines new signaling and proposes that parent PNC sends device handover request to child PNC. According to the current art, child PNC is always in range of parent PNC and also it is a part of parent piconet so can communicate with parent PNC. The present invention proposes the mechanism wherein the parent PNC will send a new device ID for the device, which is going to be a part of parent, which is part of child PNC currently. The present invention provides the mechanism that, child PNC sends device handover information to the device which is part of child PNC and is range in parent PNC, also it informs in which superframe this handover will be complete. The present invention provides the mechanism that, child PNC sends device handover Response to the parent PNC, if device handover information is sent successfully. According to the present invention, in specified superframe, the device will be part of parent PNC and considered to be disassociated from child PNC. The present invention suggests that if there are no devices in child piconet, other than child PNC then child PNC should stop the operation and should work as a device of the parent PNC. 2. Device handover from Parent to Child PNC Figure 7 displays the topology for parent to child PNC handover of the device which is no more able to hear the beacons from parent PNC because of movement, and now it is in range of child PNC. The present invention uses some of mechanisms provided by the current art to achieve the objectives of the invention, so the present invention proposes that the parent PNC announces about device which has moved out of range, but that device can be there in range of child PNC. The present invention provides a mechanism for device to join child PNC, device is there in range of child PNC, so child PNC is able to hear the heart beat of the device, so child PNC associates the device because that device is known to child PNC, because of information provided by parent PNC about moved out devices. According to the present invention, device becomes part of child piconet and parent PNC broadcasts the information that device is disassociated from parent PNC. The present invention also defines the content for the messages required for signaling the above mentioned handover procedures. Additional messages are introduced by invention are Device Handover Request, Device Handover Response and Device Handover Information Request. The present invention also introduces one Information Element named Device Moved IE for broadcast of the information of moved out devices from the range of the PNC. The present invention also defines the message sequence for performing device handover in above described scenarios. Accordingly, the present invention comprises a method of device handover from child to parent PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising the steps of: (a) sending device handover request command by parent PNC to child PNC with information of parent piconet ID, and DEVID of the device and new suggested DEVID for the device; (b) sending device handover information request command to the device by the child PNC with information of handover if the device is free; (c) sending device handover response command to parent PNC by the child PNC with response of SUCCESS and information of handover if device handover information request is sent properly; and (d) disassociating the device from child PNC and associating to parent PNC at the specified superframe number. Accordingly, the present invention further comprises a method of device handover from parent PNC to child PNC in the centralized wireless personal area networks based on mobile ad-hoc networks comprising the steps of: (a) broadcasting the information of DEVID and Device Address of the devices which are likely to move out of its range by parent PNC; (b) sending device handover information request command to the device by child PNC if it is a known device; (c) sending device handover response command to parent PNC with response of SUCCESS and information of handover by child PNC; and (d) disassociating device from parent PNC and associating to child PNC at the specified superframe number. Accordingly, the present invention further comprises a system for device handover from child to parent PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising: (a) means for sending device handover request command by parent PNC to child PNC with information of Parent piconet ID, and DEVID of the device and new suggested DEVID for the device; (b) means for sending device handover information request command to the device by the child PNC with information of handover if the device is free; (c) means for sending device handover response command to parent PNC by the child PNC with response of SUCCESS and information of handover if device handover information request is sent properly, else with response of FAILURE with reason code; and (d) means for disassociating the device from child PNC and associating to parent PNC at the specified superframe number. Accordingly, the present invention further comprises a system for device handover from parent PNC to child PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising: (a) means for broadcasting the information of DEVID and Device address of the devices which are likely to move out of its range by parent PNC; (b) means for sending device handover information request command to the device by child PNC if it is a known device; (c) means for sending device handover response command to parent PNC with response of SUCCESS and information of handover by child PNC, else with response of FAILURE with reason code; and (d) means for disassociating device from parent PNC and associating to child PNC at the specified superframe number. 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 piconet in WPAN ad-hoc network system. The piconet range, different piconet elements like DEV and PNC, frames being transferred in piconet like beacon and data transfer between DEV to DEV, PNC to DEV and DEV to PNC are shown; Figure 2 illustrates the superframe structure in current art, which includes the beacon, CAP, DAP, MCTA and CTA; Figure 3 illustrates the beacon frame in current art. Figure 4 illustrates the structure of Associated Devices Information Element in current art; Figure 5 illustrates the structure of Heart Beat Frame of in current art; Figure 6 illustrates the scenario for device handover from child to parent PNC, where device B is the device which is part of child piconet and moves in the range of parent PNC; Figure 7 illustrates the scenario for device handover from parent to child PNC, where device B is the device which is part of parent piconet and moves out of the range of parent PNC, but still in the range of child PNC; Figure 8 shows the invented MSC for device handover from child to parent PNC; and Figure 9 shows the invented MSC for device handover from parent to child PNC. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system that allows a device handover from child to parent PNC and parent to child PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks. The system and method of the present invention comprises of new frames for signaling of the device handover procedure, which includes Device Handover Request, Device Handover Response and Device Handover Information Request. The system and method of the present invention also comprises of a new information element for broadcasting the information of the device which are moved out of the range of the PNC, named Device Moved Information Element. Accordingly, the present invention provides the better reachability for the devices in a piconet. Accordingly, the invention provides the basic backbone for Mesh Networking. Accordingly, the invention also facilitates child PNC to stop its operation, if there are no devices under child PNC, because of handover of its devices to parent PNC. The subsequent subsections describe the invented individual procedures for invention. 1. Figure 8 illustrates the proposed MSC for device handover from child PNC to parent PNC. - As described in topology in figure 6, device is a part of child piconet, but it is also in range of parent PNC. Because of topology parent PNC is able to hear the heart beat from the device. - According to the invented mechanism, parent PNC sends Device Handover Request Command to child PNC with information of Parent piconet ID, and DEVID of the device and new suggested DEVID for the device. Parent PNC had learnt the DEVID of the device under child PNC by listening to its heart beats. Parent PNC expects an immediate acknowledgement for the command message sent to child PNC. - Child PNC checks that device, which is considered for handover by parent PNC is free to be handed over. If yes then child PNC sends Device Handover Information Request Command to the device with information of handover, some of them which child PNC had got from parent PNC. This information includes new piconet ID, new DEVID and superframe number when actual handover to be done and device will become part of parent piconet. Child PNC expects immediate acknowledge for the Device Handover Information Request Command. - If device is busy and cannot be handed over then child PNC does not send Device Handover Information command to the device, also it sends Device Handover Response command with the response of FAILURE to parent PNC with appropriate reason code. - If Device Handover Information Request is sent properly then child PNC will send Device Handover Response command to parent PNC with response of SUCCESS and information of handover. This information includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over. Child PNC also expects the immediate acknowledgement for this message. - According to the present invention, at the specified superframe number, the device is considered to be disassociated from child PNC and considered to be associated to parent PNC. In the same superframe parent PNC sends its beacon with information of association of the device with parent PNC and similarly child PNC sends its beacon with information of disassociation of the device from child PNC. - Parent PNC starts device handover timeout timer, when it had started the Device Handover Process. If it could not be done by the device handover timeout then it should be terminated, and if it is over by the time then timer should be stopped. 2. Figure 9 illustrates the proposed MSC for device handover from parent PNC to child PNC. - As described in topology in figure 7, device is moved out of parent piconet, but it is still in range of child PNC, which is part of parent piconet. In this situation according to invented system, parent PNC broadcasts the information of DEVID and Device Address of the devices which are likely to move out of its range. - As described in invented method above, the child PNC is aware of the DEVID and device address pair which are moved out from parent PNC. Also device is in range of child PNC, so child PNC is able to hear heart beat of device. By this heart beat child PNC can find out the DEVID of the device and PNID for that device, also by using the information provided by parent PNC, child PNC can conclude that device is known device, which is moved out from parent PNC's range or some alien device. - If device is known device then child PNC sends Device Handover Information Request command to the device with information of new DEVID, new PNID and superframe number when handover actually is going to happen. This information command will be sent with PNID of the parent PNID because device is still part of parent piconet. Child PNC expects an immediate acknowledge for this command. - If Device Handover Information Request is sent properly then child PNC will send Device Handover Response command to parent PNC with response of SUCCESS and information of handover. This information includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over. Child PNC also expects the immediate acknowledgement for this message. According to the invention, at the specified superframe number, the device is considered to be disassociated from parent PNC and considered to be associated to child PNC. In the same superframe child PNC sends its beacon with information of association of the device with child PNC and similarly parent PNC sends its beacon with information of disassociation of the device from parent PNC. Parent PNC starts device handover timeout timer, when it had started the Device Handover Process, means when parent PNC had sent its first beacon with information of the device which is supposed to be moved out. If it could not be done by the device handover timeout then it should stop sending that information in beacon and should consider that device being disassociated, and if it procedure is over with SUCCESS or FAILURE by the time then timer should be stopped. The subsequent subsections describe the additional entities introduced to effect the invention. 1. Device Handover Request This command is proposed by invention to perform the invented signaling mechanism for device handover. Following are the elements which are part of newly invented Device Handover Request command. - Old DEVID: The Old DEVID is the DEVID of the device, when it is a member of child piconet. - New DEVID: The New DEVID is the DEVID of the device, when it would be a member of parent piconet. - ATP: The ATP is association timeout period for the device, when it would join to parent piconet. The Source ID for this command is to be set to PNCID of parent PNC. The Destination ID for this command is to be set to DEVID of the device in parent piconet, which is also working as a child piconet's PNC. 2. Device Handover Response This command is also proposed by invention to perform the invented signaling mechanism for device handover. Following are the elements which are part of newly invented Device Handover Response command. - Old DEVID: The Old DEVID is the DEVID of the device before handover process is over. - Device Address: It is the MAC address of the device, whose DEVID is specified as Old DEVID. - Handover Beacon Number: The Handover beacon number is the beacon number of the parent PNC, when the actual handover process will happen. - Reason Code: If process is successful then reason code as SUCCESS, else appropriate reason code as FAILURE The Source ID is to be set to DEVID of the device in parent piconet, which is also working as a child piconet's PNC. The Destination ID is to be set to PNCID of parent PNC. 3. Device Handover Information Request This command is also proposed by invention to perform the invented signaling mechanism for device handover. Following are the elements which are part of newly invented Device Handover Information Request command. - New PNID: It is PNID of parent piconet in case of child to parent device handover, and it is PNID of child piconet in case of parent to child device handover. - New DEVID: The New DEVID is the DEVID of the device, when device will be handed over. - ATP: The ATP is association timeout period for the device, when it would be handed over. - Handover beacon number: It is the beacon number of the child PNC, when the device will be under control of the parent PNC, and beacon number of parent PNC, when the device will be under control of the child PNC. The source ID is to be set to DEVID of the device. The destination should be set to PNCID of the child PNC. 4. Device Moved Information Element This invented information element named Device Moved IE is sent by the PNC along with its beacon, which contains the information about DEVID and Device Address of the all devices which are supposed to be moved out from the range of PNC, and PNC is able to find out these devices because it would not hear the heart beat from those devices. Following are the elements which are part of newly invented Device Moved Information Element. - DEVID: DEVID is the ID of that device under the PNC, who is sending the Device Moved IE. - Device Address: DEV Address is the MAC address of the device which is supposed to be moved out of the range of the PNC. In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention. Embodiments of the invention may be implemented by using a programmed general purpose digital computer, by using application specific integrated circuits, programmable logic devices, field programmable gate arrays, optical, chemical, biological, quantum or nano-engineered systems, components and mechanisms may be used. In general, the functions of the present invention can be achieved by any means as is known in the art. Distributed or networked systems, components and circuits can be used. Communication, or transfer, of data may be wireless, wired or by any other means. It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. It is also within the spirit and scope of the present invention to implement a program or code that can be stored in a machine-readable medium to permit a computer to perform any of the methods described above. Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term "or" as used herein is generally intended to mean "and/or" unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear. As used in the description herein and throughout the claims that follow, "a", "an", and "the" includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise. The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention. Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims. GLOSSARY OF TERMS AND DEFINITONS THEREOF ADIE: Associated Devices Information Element ATP: Association Timeout Period CAP: Contention Access Period CSMA/CA: Carrier Sense Multiple Access - Collision Avoidance CTA: Channel Time Allocation CTAP: Channel Time Allocation Period DAP: Device Access Period DEV: Device DEVID: Device Identifier ID: Identifier IE: Information Element IEEE: Institute of Electrical and Electronics Engineers MAC: Medium Access Control MCTA: Management Channel Time Access MSC: Message Sequence Chart PHY: Physical Layer PNC: Piconet Coordinator PNID: Piconet Identifier PNCID: Piconet Coordinator Identifier TDMA: Time Division Multiple Access UWB: Ultra Wide Band WPAN: Wireless Personal Area Network WE CLAIM 1. A method of device handover from child to parent Piconet Coordinator (PNC) in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising the steps of: (a) sending device handover request command by parent PNC to child PNC with information of parent piconet ID, and Device Identifier (DEVID) of the device and new DEVID for the device; (b) sending device handover information request command to the device by the child PNC with information of handover if the device is free; (c) sending device handover response command to parent PNC by the child PNC with response of SUCCESS and information of handover if device handover information request is sent properly; and (d) disassociating the device from child PNC and associating to parent PNC at the specified superframe number. 2. A method as claimed in claim 1 wherein parent PNC can hear the heart beat from the said device since the device is a part of the child piconet, but also in range of parent PNC. 3. A method as claimed in claim 1 wherein Parent PNC gets the DEVID of the device under child PNC by listening to its heart beats. 4. A method as claimed in claim 1 wherein the said information sent along with device handover information request command includes new piconet ID, new DEVID and superframe number when actual handover to be done and when device will become part of parent piconet. 5. A method as claimed in claim 1 wherein if device is busy and cannot be handed over then child PNC does not send device handover information command to the device, but it sends device handover response command with the response of FAILURE to parent PNC with appropriate reason code. 6. A method as claimed in claim 1 wherein the said information send along with device handover response command includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over. 7. A method as claimed in claim 1 wherein in the superframe in which device is considered to be handed over, parent PNC sends its beacon with information of association of the device with parent PNC and similarly child PNC sends its beacon with information of disassociation of the device from child PNC. 8. A method as claimed in claim 1 wherein parent PNC starts device handover timeout timer, when it had started the device handover process and if it could not be over by the device handover timeout then it is terminated, and if it is over by the time then timer is stopped. 9. A method of device handover from parent PNC to child PNC in the centralized wireless personal area networks based on mobile ad-hoc networks comprising the steps of: (a) broadcasting the information of DEVID and Device Address of the devices which are likely to move out of its range by parent PNC; (b) sending device handover information request command to the device by child PNC if it is a known device; (c) sending device handover response command to parent PNC with response of SUCCESS and information of handover by child PNC, which is able to hear heart beat of device; and (d) disassociating device from parent PNC and associating to child PNC at the specified superframe number. 10. A method as claimed in claim 9 wherein the said device is moved out of parent piconet, but is still in range of child PNC, which is part of parent piconet. 11. A method as claimed in claim 9 wherein the child PNC is aware of the DEVID and device address pair which are moved out from parent PNC, by the information provided by parent PNC in its beacon. 12. A method as claimed in claim 9 wherein by the heart beat child PNC can find out the DEVID of the device and Piconet Identifier (PNID) for that device and also by using the information provided by parent PNC, child PNC can conclude that device is known device, which is moved out from parent PNC's range or some alien device. 13. A method as claimed in claim 9 wherein information sent to the device by Child PNC along with device handover information request command includes information of new DEVID, new PNID and superframe number when handover actually is going to happen and this information command will be sent with PNID of the parent PNID because device is still part of parent piconet. 14. A method as claimed in claim 9 wherein the information sent along with device handover response command includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over. 15. A method as claimed in claim 9 wherein the superframe in which device is considered to be handed over, child PNC sends its beacon with information of association of the device with child PNC and similarly parent PNC sends its beacon with information of disassociation of the device from parent PNC. 16. A method as claimed in claim 9 wherein parent PNC starts a device handover timeout timer, when it had started the device handover process and if it could not be over by the device handover timeout then it stop sending that information in beacon and consider that device being disassociated, and if the procedure is over with SUCCESS or FAILURE by the time then timer is stopped. 17. A method as claimed in claim 9 wherein the Device Moved information element for broadcasting the information of the device which is beyond the range of the PNC. 18. A method as claimed in claim 1 wherein the said device handover request command comprises elements such as: (a) The Old DEVID being the DEVID of the device, when it is a member of child piconet; (b) The New DEVID being the DEVID of the device, when it would be a member of parent piconet; and (c) Association Timeout Period (ATP) being association timeout period for the device, when it would join to parent piconet; 19. A method as claimed in claim 1 wherein the said device handover response command comprises elements such as: (a) The Old DEVID being the DEVID of the device before handover process is over; (b) Device Address being the Medium Access Control (MAC) address of the device, Old DEVID being the DEVID of that device; (c) Handover Beacon Number being the beacon number of the parent PNC, when the actual handover process will happen; and (d) On the event of the process being successful the reason code is SUCCESS, else reason code is FAILURE. 20. A method as claimed in claim 1 wherein the said device handover information request comprises elements such as: (a) New PNID being the PNID of parent piconet in case of child to parent device handover, and it is PNID of child piconet in case of parent to child device handover; (b) New DEVID being the DEVID of the device, when device will be handed over; (c) ATP being the association timeout period for the device, when it would be handed over; and (d) Handover Beacon Number being the beacon number of the child PNC, when the device will be under control of the parent PNC, and beacon number of parent PNC, when the device will be under control of the child PNC. 21. A method as claimed in claim 1 wherein the said Device Moved Information Element comprises elements such as: (a) DEVID being the ID of that device under the PNC, who is supposed to be moved out of the range of the PNC; and (b) Device Address being the MAC address of the device which is supposed to be moved out of the range of the PNC. 22. A method as claimed in claim 9 wherein the said device handover request command comprises elements such as: (a) The Old DEVID being the DEVID of the device, when it is a member of child piconet; (b) The New DEVID being the DEVID of the device, when it would be a member of parent piconet; and (c) Association Timeout Period (ATP) being association timeout period for the device, when it would join to parent piconet; 23. A method as claimed in claim 9 wherein the said device handover response command comprises elements such as: (a) The Old DEVID being the DEVID of the device before handover process is over; (b) Device Address being the Medium Access Control (MAC) address of the device, Old DEVID being the DEVID of that device; (c) Handover Beacon Number being the beacon number of the parent PNC, when the actual handover process will happen; and (d) On the event of the process being successful the reason code is SUCCESS, else reason code is FAILURE. 24. A method as claimed in claim 9 wherein the said device handover information request comprises elements such as: (a) New PNID being the PNID of parent piconet in case of child to parent device handover, and it is PNID of child piconet in case of parent to child device handover; (b) New DEVID being the DEVID of the device, when device will be handed over; (c) ATP being the association timeout period for the device, when it would be handed over; and (d) Handover Beacon Number being the beacon number of the child PNC, when the device will be under control of the parent PNC, and beacon number of parent PNC, when the device will be under control of the child PNC. 25. A method as claimed in claim 9 wherein the said Device Moved Information Element comprises elements such as: (a) DEVID being the ID of that device under the PNC, who is supposed to be moved out of the range of the PNC; and (b) Device Address being the MAC address of the device which is supposed to be moved out of the range of the PNC. 26. A method of device handover from child to parent PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks such as substantially herein described particularly with reference to the drawings.

Full Text

FIELD OF TECHNOLOGY
This invention relates to the field of wireless mobile ad-hoc networks. Further, this invention relates to device handover procedure for wireless personal area networks that are based on wireless mobile ad-hoc networks. Particularly, this invention relates to the effective mechanisms of handing over the device from child piconet to parent piconet and parent piconet to child piconet in the centralized wireless personal area networks. More particularly, this invention encompasses a system and method for device handover 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. at a distance of approximately 10 meters. The IEEE (http://www.ieee.org) 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. Medium Access Control mechanisms to deal with such high data rates are currently being discussed in IEEE draft P802.15.3/D17. The medium access control mechanisms broadly include how a device may join the network, how it can transfer data at the required rate to another device, how the medium is best used etc.
Figure 1 illustrates the IEEE-802.15.3 based wireless personal area network. It involves a network referred as piconet, in which a device may act as coordinator (referred as piconet coordinator or PNC herein). The PNC performs the functions of allowing a device (referred as DEV) to join, allocating it a channel (time slot) to transmit to another device, synchronization mechanisms etc. This is a centralized WPAN system which is formed in an ad-hoc fashion.
Dependant piconet is a piconet that exists entirely within a channel time allocation

of another piconet, the parent piconet. Child piconet is a subtype of dependant piconet that exists entirely within a channel time allocation of another piconet, the parent piconet, is controlled by a device that is a member of the parent piconet. Neighbor piconet is also a subtype of dependant piconet that exists entirely within a channel time allocation of another piconet, the parent piconet, is controlled by a device that is not a member of the parent piconet.
A child piconet is one that is formed under an established piconet. The established piconet then becomes the parent piconet. The child piconet functionality is useful for either extending the area of coverage of the piconet or shifting some computational or memory requirements to another PNC capable device. It is possible for the parent piconet to have more than one child piconet. In addition, it is also possible for a child PNC to allow a child piconet as a part of its own piconet.
The child piconet uses a distinct piconet ID (PNID) and acts as an autonomous piconet except that it is dependent on a private CTA from the parent piconet. Association and security membership for the child piconet are handled within the child piconet and do not involve the parent PNC.
The child PNC is a member of the parent piconet and thus is able to exchange data with any DEV in the parent piconet. The child PNC is also a member of the child piconet and thus is able to exchange data with any DEV in the child piconet.
The invention also considers the Indian patent application bearing application No. 221/CHE/2004 titled "SYSTEM AND METHOD FOR MEDIUM ACCESS CONTROL IN WIRELESS MOBILE AD-HOC NETWORKS" as part of current art. Superframe structure described in that patent document is an enhanced superframe which is specified in IEEE draft P802.15.3/D17.
Figure 2 illustrates the superframe structure. Superframe is channel distribution specified by the PNC among the DEVs in piconet. It is informed to DEVs through beacon frame, which is being broadcasted by PNC.

Superframe is composed of 3 parts:
1. Beacon: It is used to set the timing allocations and to communicate management Information for the piconet. All the associated devices listen to this beacon.
2. Contention access period (CAP): It is used to communicate commands from the DEV to PNC or vice versa. It may also be used for asynchronous data if it is present in the superframe. The length of the CAP is determined by the PNC and communicated to the DEVs in the piconet via the beacon. The CAP uses CSMA/CA protocol for the medium access.
3. Channel time allocation period (CTAP): It consists of channel time allocations (CTAs), including management CTAs (MCTAs). CTAs are used for commands, isochronous streams and asynchronous data connections. A PNC may choose to use MCTAs instead of the CAP for sending command frames, unless otherwise restricted by the physical layer (PHY). An open MCTA is one where the SrcID is the BcstID; Any DEV that is associated in the piconet may attempt to send a command frame to the PNC in an open MCTA. An MCTA with the UnassocID as the SrcID is an association MCTA. Any DEV not currently associated in the piconet may attempt to send an Association Request command to the PNC in an association MCTA.
Device Access Period (DAP): DAP is used by all the associated DEVs in piconet to send their respective heart beat frames. By listening to the heart beat frames as contained in DAP, it is possible for a first associated device to know exactly whether a second associated device is in range(reachable) or not, depending upon whether the first associated device was able to listen to the heart beat frame sent by the second associated device in the DAP.
The CTAP, in contrast to CAP, uses a standard TDMA protocol where the devices (DEVs) have specified time windows which are called the CTAs.

MCTAs are either assigned to a specific source/destination pair for management traffic and use TDMA for access or they are shared MCTAs that are accessed using the slotted aloha protocol.
Beacon frame is illustrated in figure 3. Information Elements (lEs) in figure 3 are encoded in type, length, value format. The lEs in the beacon payload may appear in any order except for the channel time allocation (CTA) lEs, which is the first IE of the beacon payload following the piconet synchronization parameters field. CTA IE consists of information about the CTAs in the superframe. Figure 4 shows the structure of ADIE.
Heart beat frame is a very small MAC frame which is always broadcasted by all the associated DEVs in the piconet. Format of the heart beat frame in the current art is illustrated in figure 5. One of purpose of the heart beat frame is to advertise its own presence of its neighbors and PNC.
Associated Devices Information Element (ADIE) is broadcasted by the PNC to all the devices in the piconet. Usage of the ADIE is to provide the information to all the devices to schedule their heart beat frames in DAP. This information element must be sent with beacon if there is at least one device associated with the PNC.
LIMITATIONS
The present state of art in this field, as discussed in IEEE 802.15.3 (http://www.ieee.org) and as described in above mentioned patent, has certain limitations, namely, there is no mechanism when a device in child piconet is also in range of parent piconet and can effectively become a part of parent piconet and release resources for child PNC. Consequently, if there is no device left in child piconet then operation of child piconet can be terminated. Also, there is no mechanism for joining a child piconet by a device, when device in parent piconet

moves out of the range of the parent PNC but still in range of child PNC. Stating same at broad level, there is no mechanism for device handover from child to parent piconet and parent to child piconet in current art.
Currently in the medium access control mechanism as defined in current art; there is no mechanism for the following:
1. When device in child piconet is in radio range of parent piconet also, then there is no mechanism, that parent PNC can take over the device, associate the device with itself (Parent PNC) and child PNC can disassociate the device from itself (Child PNC);
2. When device in parent piconet moves out of the radio range of parent PNC, but if it is still in range of child PNC of the parent piconet, then there is no mechanism for child to become a part of child piconet without disassociation because of ATP timeout and scanning procedure again; and
3. In other words, current art does not provide the method for device handover from child to parent PNC and parent to child PNC.
OBJECTS OF THE INVENTION
The primary object of the invention is to provide a system and method for device handover from child to parent PNC and parent to child PNC in medium access control for the UWB wireless personal area networks, which are based on wireless ad-hoc networks, in a centralized network topology.
It is another object of the invention to provide a mechanism where the device in child piconet is in radio range of the parent PNC then parent PNC and child PNC can communicate with each other and parent PNC can take over the charge of the device and child PNC can disassociate the device from child piconet.
It is another object of the invention to provide the mechanism for device handover from child to parent PNC, in which device does not require disassociating itself from

child PNC by initiating disassociation process, it does not require scanning and it does not require sending association request for associating itself with parent PNC.
It is another object of the invention to provide a mechanism for where the device moves out of the radio range of the parent PNC but it is still in radio range of the child PNC, then parent PNC and child PNC can communicate with each other and child PNC can take over the charge of the device and parent PNC can disassociate the device from parent PNC.
It is another object of the invention to provide the mechanism for device handover from parent to child PNC, in which device does not require to disassociate itself from parent PNC because of ATP timeout.
SUMMARY OF THE INVENTION
The present invention relates to a system that provides the mechanism of device handover from child to parent piconet and parent to child piconet in the Wireless Personal Area Networks based on mobile ad-hoc networks.
In detail, the present invention provides the mechanism of device handover from child to parent and vice versa, without device to be disassociated from its PNC, so this handover is handled by coordination between child and parent PNCs.
The present invention comprises of system and method which would overcome the inability of device handover with current art, in the following manner:
There are two scenarios for device handover. One is device handover from child to parent PNC and other is device handover from parent to child PNC.
1. Device handover from Child to Parent PNC

Figure 6 displays the topology for child to parent PNC handover of the device which is part of child PNC, and also it is in range of parent PNC.
The present invention uses some mechanisms provided by current art to achieve the objectives of invention, so parent PNC is able to hear the heart beat of the device which is in range of parent PNC.
The mechanism of the present invention defines new signaling and proposes that parent PNC sends device handover request to child PNC. According to the current art, child PNC is always in range of parent PNC and also it is a part of parent piconet so can communicate with parent PNC. The present invention proposes the mechanism wherein the parent PNC will send a new device ID for the device, which is going to be a part of parent, which is part of child PNC currently.
The present invention provides the mechanism that, child PNC sends device handover information to the device which is part of child PNC and is range in parent PNC, also it informs in which superframe this handover will be complete.
The present invention provides the mechanism that, child PNC sends device handover Response to the parent PNC, if device handover information is sent successfully.
According to the present invention, in specified superframe, the device will be part of parent PNC and considered to be disassociated from child PNC.
The present invention suggests that if there are no devices in child piconet, other than child PNC then child PNC should stop the operation and should work as a device of the parent PNC.
2. Device handover from Parent to Child PNC

Figure 7 displays the topology for parent to child PNC handover of the device which is no more able to hear the beacons from parent PNC because of movement, and now it is in range of child PNC.
The present invention uses some of mechanisms provided by the current art to achieve the objectives of the invention, so the present invention proposes that the parent PNC announces about device which has moved out of range, but that device can be there in range of child PNC.
The present invention provides a mechanism for device to join child PNC, device is there in range of child PNC, so child PNC is able to hear the heart beat of the device, so child PNC associates the device because that device is known to child PNC, because of information provided by parent PNC about moved out devices.
According to the present invention, device becomes part of child piconet and parent PNC broadcasts the information that device is disassociated from parent PNC.
The present invention also defines the content for the messages required for signaling the above mentioned handover procedures. Additional messages are introduced by invention are Device Handover Request, Device Handover Response and Device Handover Information Request. The present invention also introduces one Information Element named Device Moved IE for broadcast of the information of moved out devices from the range of the PNC.
The present invention also defines the message sequence for performing device handover in above described scenarios.

Accordingly, the present invention comprises a method of device handover from child to parent PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising the steps of:
(a) sending device handover request command by parent PNC to child PNC with information of parent piconet ID, and DEVID of the device and new suggested DEVID for the device;
(b) sending device handover information request command to the device by the child PNC with information of handover if the device is free;
(c) sending device handover response command to parent PNC by the child PNC with response of SUCCESS and information of handover if device handover information request is sent properly; and
(d) disassociating the device from child PNC and associating to parent PNC at the specified superframe number.
Accordingly, the present invention further comprises a method of device handover from parent PNC to child PNC in the centralized wireless personal area networks based on mobile ad-hoc networks comprising the steps of:
(a) broadcasting the information of DEVID and Device Address of the devices which are likely to move out of its range by parent PNC;
(b) sending device handover information request command to the device by child PNC if it is a known device;
(c) sending device handover response command to parent PNC with response of SUCCESS and information of handover by child PNC; and
(d) disassociating device from parent PNC and associating to child PNC at the specified superframe number.
Accordingly, the present invention further comprises a system for device handover from child to parent PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising:

(a) means for sending device handover request command by parent PNC to child PNC with information of Parent piconet ID, and DEVID of the device and new suggested DEVID for the device;
(b) means for sending device handover information request command to the device by the child PNC with information of handover if the device is free;
(c) means for sending device handover response command to parent PNC by the child PNC with response of SUCCESS and information of handover if device handover information request is sent properly, else with response of FAILURE with reason code; and
(d) means for disassociating the device from child PNC and associating to parent PNC at the specified superframe number.
Accordingly, the present invention further comprises a system for device handover from parent PNC to child PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks comprising:
(a) means for broadcasting the information of DEVID and Device address of the devices which are likely to move out of its range by parent PNC;
(b) means for sending device handover information request command to the device by child PNC if it is a known device;
(c) means for sending device handover response command to parent PNC with response of SUCCESS and information of handover by child PNC, else with response of FAILURE with reason code; and
(d) means for disassociating device from parent PNC and associating to child PNC at the specified superframe number.
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 piconet in WPAN ad-hoc network system. The piconet range, different piconet elements like DEV and PNC, frames being transferred in piconet like beacon and data transfer between DEV to DEV, PNC to DEV and DEV to PNC are shown;
Figure 2 illustrates the superframe structure in current art, which includes the beacon, CAP, DAP, MCTA and CTA;
Figure 3 illustrates the beacon frame in current art.
Figure 4 illustrates the structure of Associated Devices Information Element in current art;
Figure 5 illustrates the structure of Heart Beat Frame of in current art;
Figure 6 illustrates the scenario for device handover from child to parent PNC, where device B is the device which is part of child piconet and moves in the range of parent PNC;
Figure 7 illustrates the scenario for device handover from parent to child PNC, where device B is the device which is part of parent piconet and moves out of the range of parent PNC, but still in the range of child PNC;
Figure 8 shows the invented MSC for device handover from child to parent PNC; and
Figure 9 shows the invented MSC for device handover from parent to child PNC.

DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a system that allows a device handover from child to parent PNC and parent to child PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks.
The system and method of the present invention comprises of new frames for signaling of the device handover procedure, which includes Device Handover Request, Device Handover Response and Device Handover Information Request.
The system and method of the present invention also comprises of a new information element for broadcasting the information of the device which are moved out of the range of the PNC, named Device Moved Information Element.
Accordingly, the present invention provides the better reachability for the devices in a piconet.
Accordingly, the invention provides the basic backbone for Mesh Networking.
Accordingly, the invention also facilitates child PNC to stop its operation, if there are no devices under child PNC, because of handover of its devices to parent PNC.
The subsequent subsections describe the invented individual procedures for invention.
1. Figure 8 illustrates the proposed MSC for device handover from child PNC to parent PNC.
- As described in topology in figure 6, device is a part of child piconet, but it is also in range of parent PNC. Because of topology parent PNC is able to hear the heart beat from the device.
- According to the invented mechanism, parent PNC sends Device Handover Request Command to child PNC with information of Parent

piconet ID, and DEVID of the device and new suggested DEVID for the device. Parent PNC had learnt the DEVID of the device under child PNC by listening to its heart beats. Parent PNC expects an immediate acknowledgement for the command message sent to child PNC.
- Child PNC checks that device, which is considered for handover by parent PNC is free to be handed over. If yes then child PNC sends Device Handover Information Request Command to the device with information of handover, some of them which child PNC had got from parent PNC. This information includes new piconet ID, new DEVID and superframe number when actual handover to be done and device will become part of parent piconet. Child PNC expects immediate acknowledge for the Device Handover Information Request Command.
- If device is busy and cannot be handed over then child PNC does not send Device Handover Information command to the device, also it sends Device Handover Response command with the response of FAILURE to parent PNC with appropriate reason code.
- If Device Handover Information Request is sent properly then child PNC will send Device Handover Response command to parent PNC with response of SUCCESS and information of handover. This information includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over. Child PNC also expects the immediate acknowledgement for this message.
- According to the present invention, at the specified superframe number, the device is considered to be disassociated from child PNC and considered to be associated to parent PNC. In the same superframe parent PNC sends its beacon with information of association of the device with parent PNC and similarly child PNC sends its beacon with information of disassociation of the device from

child PNC.
- Parent PNC starts device handover timeout timer, when it had started
the Device Handover Process. If it could not be done by the device
handover timeout then it should be terminated, and if it is over by the
time then timer should be stopped.
2. Figure 9 illustrates the proposed MSC for device handover from parent PNC to child PNC.
- As described in topology in figure 7, device is moved out of parent piconet, but it is still in range of child PNC, which is part of parent piconet. In this situation according to invented system, parent PNC broadcasts the information of DEVID and Device Address of the devices which are likely to move out of its range.
- As described in invented method above, the child PNC is aware of the DEVID and device address pair which are moved out from parent PNC. Also device is in range of child PNC, so child PNC is able to hear heart beat of device. By this heart beat child PNC can find out the DEVID of the device and PNID for that device, also by using the information provided by parent PNC, child PNC can conclude that device is known device, which is moved out from parent PNC's range or some alien device.
- If device is known device then child PNC sends Device Handover Information Request command to the device with information of new DEVID, new PNID and superframe number when handover actually is going to happen. This information command will be sent with PNID of the parent PNID because device is still part of parent piconet. Child PNC expects an immediate acknowledge for this command.
- If Device Handover Information Request is sent properly then child PNC will send Device Handover Response command to parent PNC with response of SUCCESS and information of handover. This information includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which

device will be considered to be handed over. Child PNC also expects the immediate acknowledgement for this message. According to the invention, at the specified superframe number, the device is considered to be disassociated from parent PNC and considered to be associated to child PNC. In the same superframe child PNC sends its beacon with information of association of the device with child PNC and similarly parent PNC sends its beacon with information of disassociation of the device from parent PNC. Parent PNC starts device handover timeout timer, when it had started the Device Handover Process, means when parent PNC had sent its first beacon with information of the device which is supposed to be moved out. If it could not be done by the device handover timeout then it should stop sending that information in beacon and should consider that device being disassociated, and if it procedure is over with SUCCESS or FAILURE by the time then timer should be stopped.
The subsequent subsections describe the additional entities introduced to effect the invention.
1. Device Handover Request
This command is proposed by invention to perform the invented signaling mechanism for device handover. Following are the elements which are part of newly invented Device Handover Request command.
- Old DEVID: The Old DEVID is the DEVID of the device, when it is a member of child piconet.
- New DEVID: The New DEVID is the DEVID of the device, when it would be a member of parent piconet.
- ATP: The ATP is association timeout period for the device, when it would join to parent piconet.
The Source ID for this command is to be set to PNCID of parent PNC.

The Destination ID for this command is to be set to DEVID of the device in parent piconet, which is also working as a child piconet's PNC.
2. Device Handover Response
This command is also proposed by invention to perform the invented signaling mechanism for device handover. Following are the elements which are part of newly invented Device Handover Response command.
- Old DEVID: The Old DEVID is the DEVID of the device before handover process is over.
- Device Address: It is the MAC address of the device, whose DEVID is specified as Old DEVID.
- Handover Beacon Number: The Handover beacon number is the beacon number of the parent PNC, when the actual handover process will happen.
- Reason Code: If process is successful then reason code as SUCCESS, else appropriate reason code as FAILURE
The Source ID is to be set to DEVID of the device in parent piconet, which is also working as a child piconet's PNC. The Destination ID is to be set to PNCID of parent PNC.
3. Device Handover Information Request
This command is also proposed by invention to perform the invented signaling mechanism for device handover. Following are the elements which are part of newly invented Device Handover Information Request command.
- New PNID: It is PNID of parent piconet in case of child to parent device handover, and it is PNID of child piconet in case of parent to child device handover.
- New DEVID: The New DEVID is the DEVID of the device, when device will be handed over.
- ATP: The ATP is association timeout period for the device, when it would be handed over.
- Handover beacon number: It is the beacon number of the child PNC,

when the device will be under control of the parent PNC, and beacon number of parent PNC, when the device will be under control of the child PNC.
The source ID is to be set to DEVID of the device.
The destination should be set to PNCID of the child PNC.
4. Device Moved Information Element
This invented information element named Device Moved IE is sent by the PNC along with its beacon, which contains the information about DEVID and Device Address of the all devices which are supposed to be moved out from the range of PNC, and PNC is able to find out these devices because it would not hear the heart beat from those devices. Following are the elements which are part of newly invented Device Moved Information Element.
- DEVID: DEVID is the ID of that device under the PNC, who is sending the Device Moved IE.
- Device Address: DEV Address is the MAC address of the device which is supposed to be moved out of the range of the PNC.
In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.
Embodiments of the invention may be implemented by using a programmed general purpose digital computer, by using application specific integrated circuits, programmable logic devices, field programmable gate arrays, optical, chemical,

biological, quantum or nano-engineered systems, components and mechanisms may be used. In general, the functions of the present invention can be achieved by any means as is known in the art. Distributed or networked systems, components and circuits can be used. Communication, or transfer, of data may be wireless, wired or by any other means.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. It is also within the spirit and scope of the present invention to implement a program or code that can be stored in a machine-readable medium to permit a computer to perform any of the methods described above.
Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term "or" as used herein is generally intended to mean "and/or" unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear.
As used in the description herein and throughout the claims that follow, "a", "an", and "the" includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will

recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention.
Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims.

GLOSSARY OF TERMS AND DEFINITONS THEREOF
ADIE: Associated Devices Information Element
ATP: Association Timeout Period
CAP: Contention Access Period
CSMA/CA: Carrier Sense Multiple Access - Collision Avoidance
CTA: Channel Time Allocation
CTAP: Channel Time Allocation Period
DAP: Device Access Period
DEV: Device
DEVID: Device Identifier
ID: Identifier
IE: Information Element
IEEE: Institute of Electrical and Electronics Engineers
MAC: Medium Access Control
MCTA: Management Channel Time Access
MSC: Message Sequence Chart
PHY: Physical Layer
PNC: Piconet Coordinator
PNID: Piconet Identifier
PNCID: Piconet Coordinator Identifier
TDMA: Time Division Multiple Access
UWB: Ultra Wide Band
WPAN: Wireless Personal Area Network

WE CLAIM
1. A method of device handover from child to parent Piconet Coordinator (PNC) in
the Centralized Wireless Personal Area Networks based on mobile ad-hoc
networks comprising the steps of:
(a) sending device handover request command by parent PNC to child PNC with information of parent piconet ID, and Device Identifier (DEVID) of the device and new DEVID for the device;
(b) sending device handover information request command to the device by the child PNC with information of handover if the device is free;
(c) sending device handover response command to parent PNC by the child PNC with response of SUCCESS and information of handover if device handover information request is sent properly; and
(d) disassociating the device from child PNC and associating to parent PNC at the specified superframe number.

2. A method as claimed in claim 1 wherein parent PNC can hear the heart beat from the said device since the device is a part of the child piconet, but also in range of parent PNC.
3. A method as claimed in claim 1 wherein Parent PNC gets the DEVID of the device under child PNC by listening to its heart beats.
4. A method as claimed in claim 1 wherein the said information sent along with device handover information request command includes new piconet ID, new DEVID and superframe number when actual handover to be done and when device will become part of parent piconet.
5. A method as claimed in claim 1 wherein if device is busy and cannot be handed over then child PNC does not send device handover information command to the

device, but it sends device handover response command with the response of FAILURE to parent PNC with appropriate reason code.
6. A method as claimed in claim 1 wherein the said information send along with device handover response command includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over.
7. A method as claimed in claim 1 wherein in the superframe in which device is considered to be handed over, parent PNC sends its beacon with information of association of the device with parent PNC and similarly child PNC sends its beacon with information of disassociation of the device from child PNC.
8. A method as claimed in claim 1 wherein parent PNC starts device handover timeout timer, when it had started the device handover process and if it could not be over by the device handover timeout then it is terminated, and if it is over by the time then timer is stopped.
9. A method of device handover from parent PNC to child PNC in the centralized wireless personal area networks based on mobile ad-hoc networks comprising the steps of:

(a) broadcasting the information of DEVID and Device Address of the devices which are likely to move out of its range by parent PNC;
(b) sending device handover information request command to the device by child PNC if it is a known device;
(c) sending device handover response command to parent PNC with response of SUCCESS and information of handover by child PNC, which is able to hear heart beat of device; and
(d) disassociating device from parent PNC and associating to child PNC at the specified superframe number.

10. A method as claimed in claim 9 wherein the said device is moved out of parent piconet, but is still in range of child PNC, which is part of parent piconet.
11. A method as claimed in claim 9 wherein the child PNC is aware of the DEVID and device address pair which are moved out from parent PNC, by the information provided by parent PNC in its beacon.
12. A method as claimed in claim 9 wherein by the heart beat child PNC can find out the DEVID of the device and Piconet Identifier (PNID) for that device and also by using the information provided by parent PNC, child PNC can conclude that device is known device, which is moved out from parent PNC's range or some alien device.
13. A method as claimed in claim 9 wherein information sent to the device by Child PNC along with device handover information request command includes information of new DEVID, new PNID and superframe number when handover actually is going to happen and this information command will be sent with PNID of the parent PNID because device is still part of parent piconet.
14. A method as claimed in claim 9 wherein the information sent along with device handover response command includes new suggested DEVID, device address of the device which is going to be handed over, superframe number in which device will be considered to be handed over.
15. A method as claimed in claim 9 wherein the superframe in which device is considered to be handed over, child PNC sends its beacon with information of association of the device with child PNC and similarly parent PNC sends its beacon with information of disassociation of the device from parent PNC.
16. A method as claimed in claim 9 wherein parent PNC starts a device handover timeout timer, when it had started the device handover process and if it could not be over by the device handover timeout then it stop sending that information in

beacon and consider that device being disassociated, and if the procedure is over with SUCCESS or FAILURE by the time then timer is stopped.
17. A method as claimed in claim 9 wherein the Device Moved information element for broadcasting the information of the device which is beyond the range of the PNC.
18. A method as claimed in claim 1 wherein the said device handover request command comprises elements such as:

(a) The Old DEVID being the DEVID of the device, when it is a member of child piconet;
(b) The New DEVID being the DEVID of the device, when it would be a member of parent piconet; and
(c) Association Timeout Period (ATP) being association timeout period for the device, when it would join to parent piconet;
19. A method as claimed in claim 1 wherein the said device handover response
command comprises elements such as:
(a) The Old DEVID being the DEVID of the device before handover process is over;
(b) Device Address being the Medium Access Control (MAC) address of the device, Old DEVID being the DEVID of that device;
(c) Handover Beacon Number being the beacon number of the parent PNC, when the actual handover process will happen; and
(d) On the event of the process being successful the reason code is SUCCESS, else reason code is FAILURE.
20. A method as claimed in claim 1 wherein the said device handover information
request comprises elements such as:

(a) New PNID being the PNID of parent piconet in case of child to parent device handover, and it is PNID of child piconet in case of parent to child device handover;
(b) New DEVID being the DEVID of the device, when device will be handed over;
(c) ATP being the association timeout period for the device, when it would be handed over; and
(d) Handover Beacon Number being the beacon number of the child PNC, when the device will be under control of the parent PNC, and beacon number of parent PNC, when the device will be under control of the child PNC.
21. A method as claimed in claim 1 wherein the said Device Moved Information
Element comprises elements such as:
(a) DEVID being the ID of that device under the PNC, who is supposed to
be moved out of the range of the PNC; and
(b) Device Address being the MAC address of the device which is
supposed to be moved out of the range of the PNC.
22. A method as claimed in claim 9 wherein the said device handover request
command comprises elements such as:
(a) The Old DEVID being the DEVID of the device, when it is a member of child piconet;
(b) The New DEVID being the DEVID of the device, when it would be a member of parent piconet; and
(c) Association Timeout Period (ATP) being association timeout period for the device, when it would join to parent piconet;
23. A method as claimed in claim 9 wherein the said device handover response
command comprises elements such as:

(a) The Old DEVID being the DEVID of the device before handover process is over;
(b) Device Address being the Medium Access Control (MAC) address of the device, Old DEVID being the DEVID of that device;
(c) Handover Beacon Number being the beacon number of the parent PNC, when the actual handover process will happen; and
(d) On the event of the process being successful the reason code is SUCCESS, else reason code is FAILURE.
24. A method as claimed in claim 9 wherein the said device handover information
request comprises elements such as:
(a) New PNID being the PNID of parent piconet in case of child to parent device handover, and it is PNID of child piconet in case of parent to child device handover;
(b) New DEVID being the DEVID of the device, when device will be handed over;
(c) ATP being the association timeout period for the device, when it would be handed over; and
(d) Handover Beacon Number being the beacon number of the child PNC, when the device will be under control of the parent PNC, and beacon number of parent PNC, when the device will be under control of the child PNC.
25. A method as claimed in claim 9 wherein the said Device Moved Information
Element comprises elements such as:
(a) DEVID being the ID of that device under the PNC, who is supposed to
be moved out of the range of the PNC; and
(b) Device Address being the MAC address of the device which is
supposed to be moved out of the range of the PNC.

26. A method of device handover from child to parent PNC in the Centralized Wireless Personal Area Networks based on mobile ad-hoc networks such as substantially herein described particularly with reference to the drawings.

Documents:

0574-che-2004 abstract duplicate.pdf

0574-che-2004 abstract.pdf

0574-che-2004 claims duplicate.pdf

0574-che-2004 claims.pdf

0574-che-2004 correspondence-others.pdf

0574-che-2004 correspondence-po.pdf

0574-che-2004 description (compelet) duplicate.pdf

0574-che-2004 description (compelet).pdf

0574-che-2004 drawings duplicate.pdf

0574-che-2004 drawings.pdf

0574-che-2004 form-1.pdf

0574-che-2004 form-13.pdf

0574-che-2004 form-19.pdf

0574-che-2004 form-26.pdf

0574-che-2004 form-5.pdf

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Patent Number

231330

Indian Patent Application Number

574/CHE/2004

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

04-Mar-2009

Date of Filing

17-Jun-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	WASON, PRASHANT	BAGMANE LAKEVIEW, BLOCK B, NO. 66/1, BAGMANE TECH PARK, C.V. RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,
2	HOLUR, BALAJI SRINIVAS	BAGMANE LAKEVIEW, BLOCK B, NO. 66/1, BAGMANE TECH PARK, C.V. RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,
3	CHOUDHARY, DR. MANOJ	BAGMANE LAKEVIEW, BLOCK B, NO. 66/1, BAGMANE TECH PARK, C.V. RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,
4	ARUNAN, THENMOZHI	BAGMANE LAKEVIEW, BLOCK B, NO. 66/1, BAGMANE TECH PARK, C.V. RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,
5	KUMAR, VIVEK	BAGMANE LAKEVIEW, BLOCK B, NO. 66/1, BAGMANE TECH PARK, C.V. RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,
6	JOGI, SUNIL	BAGMANE LAKEVIEW, BLOCK B, NO. 66/1, BAGMANE TECH PARK, C.V. RAMAN NAGAR, BYRASANDRA, BANGALORE 560 093,

PCT International Classification Number

H04L 012/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA