Title of Invention

SYSTEM AND METHOD FOR CHANNEL TIME RESERVATION IN WIRELESS PERSONAL AREA NETWORKS

Abstract

A system and method for channel time reservation in wireless personal area networks in the media access layer the said system comprising: Data Slot Reservation Indicator (DSRI), that is included and sent in beacon by the device and contains information about the status of all the data slots; DS-Req Information Element, to reserve slots between the source and destination; DS-Res Information Element, to respond to slot reservation requests from the source; DS-ACK Information Element, to respond to complete the three way handshake for slot reservation between the source and destination device; and DS-NACK Information Element, to signal cancellation or termination of slot reservation between the source and destination device.

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 mechanisms, for channel time reservations in the wireless personal area networks that allow the devices to communicate data with other devices in the network. More particularly, this invention encompasses a system and method for channel time reservation in the medium access control functionality for wireless personal area networks based on ultra wide band (UWB) systems. By incorporating the invention, ability is provided for devices to be able to reserve channel time for their communication in a completely distributed manner without the requirement of a centralized entity or infrastructure. 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 etc. Medium access control for wireless personal area networks can be designed in two approaches - centralized and distributed. In the centralized approach, one of the device acts on behalf of the whole network to coordinate in managing the media access operations for all the devices. All other devices seek help of the centralized coordinator for media access operations like joining the network, reserving channel time, etc. In the Distributed approach, the media access operations are distributed evenly across all devices in the network and all of the devices share the load of managing media access operations for each other. Figure 1 shows the wireless personal area network, which is based on IEEE-802.15.3 and illustrates the centralized media access control approach. It involves a network referred as piconet, in which a device may act as coordinator (referred as piconet coordinator or PNC in literature). 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. Figure 2 shows the wireless personal area network, which does not have any centralized coordinator and illustrates the distributed media access control approach. All devices cooperate and share information with each other to perform the media access control tasks such as allowing a new device to join, allocation of channel time to a device to transmit data to another device, synchronization mechanisms etc. This is a Distributed WPAN system which is formed in an ad-hoc fashion. Figure 2 illustrates the superframe structure, specified by the Multiband OFDM Alliance (MBOA, http://www.multibandofdm.org) draft vO.5. It consists of several Medium Access Slots (As an example, the number Is shown as 256). Some Medium Access Slots (MAS) constitute beacon period (comprising of beacon slots corresponding to multiple devices) and remaining MASes constitute data period (comprising of MASes those may be used by different devices in the network to transmit data to other devices in the network), employs superframe of duration approximately 64 milii-second, and each MAS is of 256 microseconds duration. It is important to note here that the channel time allocation schemes and beaconing schemes should be independent of the actual values of these parameters. Information about superframe is being broadcasted by each device in its broadcasted beacons in beacon period, so neighbors of that device can use that information for further processing. The start time of the superframe is determined by the beginning of the beacon period and defined as the beacon period start time (BPST). The Distributed media access control approach relies on a timing concept called the Superframe. Superframe has a fixed length in time and is divided into a number of time windows which are called time slots. Some of the time slots are used by the devices to send their beacons and the other are used by the devices to send the data. The slots in which beacon is sent are called beacon slots and the slots in which data is sent are called data slots. The length of a beacon slot may be less than the length of a data slot. The beacon slots may be distributed across the slots in the superframe or may appear together at the start of the superframe. In addition, the number of beacon slots may be fixed or variable leading to different configurations of Distributed Medium Access Control mechanisms. Devices need to find a free slot from the beacon slots to send its beacon. A device which is sending its beacon regularly is considered to be a part of the network. Further, devices need free data slot to communicate with each other. In order to reserve such a data slot, it is necessary to know that both the transmitter and receiver are free in that particular data slot. The reservation of data slots takes place in a completely distributed manner with the devices sharing information and helping each other to reserve slots. Here it is important to note that, unlike in the centralized WPANs, no device acts as a central coordinator for the various medium access operations. The illustrative example of the superframe as shown in Figure 3, consists of beacon period (comprising of beacon slots corresponding to multiple devices) and data period (comprising of data slots that may be used by different devices in the network to transmit data to other devices in the network), employs a superframe duration of 64 milli-second with 256 beacon slots and 128 data slots. It is important to note here that the channel time allocation schemes should be independent of the actual values of these parameters. It is also important to note that channel time allocation scheme is independent of number of beacon period and data period in superframe. Further, channel time negotiation is a scheme of negotiation of channel time, which is a time slot, anywhere in superframe regardless of beacon period or data period. Once a beacon slot is reserved, it is used by the device as long as it is a part of the network. On the contrary, the data slots are freed by the device as and when it has stopped using them (because of communication to other device being over). These freed data slots get added to the free data slot pool and can be reserved by other devices. No device can reserve a slot already reserved by another device. The present state of art in this field has certain limitations, namely, the methods are not robust enough to manage reservation conflicts arising out of two devices wanting to reserve the same data slot simultaneously, or the scheme are able to handle very simple cases only. Consequently, a robust and efficient method to perform slot reservations in a Distributed wireless personal area network is not available. Currently no method exists for data slot reservation in a distributed wireless personal area network that handles ail the below functions in an efficient manner: 1. Mechanism to find the common free slots to reserve for sender and receiver. 2. Mechanism to detect and resolve reservation conflicts arising out of two devices trying to reserve the same data slot simultaneously. 3. Mechanism to handle the case of multicast and unicast data streams differently by taking advantage of the differences between the properties of these streams. 4. Provision to allow communication on multiple channels, if allowed by the capabilities of the physical layer. 5. Ability to reduce time spent in reservation so that inter-device communication can start faster. 6. Ability to prioritize reservations for various kinds of data traffic, hence aiding QoS in the network. SUMMARY OF THE INVENTION The primary object of this invention is therefore to provide a system and method for slot reservation in a completely distributed manner in UWB wireless personal area networks, which are based on wireless ad-hoc networks, in a distributed network topology. The mechanisms provides in the invention allows for channel time reservation in any other distributed network in which the channel time is slotted and distributed reservation is deemed necessary for reserving the channel time for any purpose in the media access layer. It is another object of the invention to provide a mechanism where the reservation mechanism provides information about the slots to the devices to assist them for the communication (data transfer) operation within the reserved slots. Also must be noted that, the slot can be used for the purpose other than data transfer. It is another object of the invention to provide its own availability in the superframe, in form of free or busy slots, to facilitate reservation and other tasks (e.g. communication using EDCA), power save synchronization etc. It is another object of the invention to enhance the performance of contention based communication schemes {e.g. EDCA) within the slots. It is another object of the invention to provide a mechanism for avoidance, detection and resolution of reservation conflicts between devices reserving the same slot simultaneously. It is another object of the invention to provide a mechanism by which the differences between properties of the multicast and Unicast streams are effectively used to make data slot reservations. It is another object of the invention to provide capability of spatial reuse through the use of multiple channels if supported by the underlying physical layer. The present invention relates to a system that allows reservation of channel time as slots for communication between devices in the Wireless Personal Area Networks based on mobile ad-hoc networks. The invention relates to system and method which allows all devices within the wireless personal area network to reserve channel time as data slots for their communication needs, without the need and assistance of a centralized coordinating device, in a completely distributed manner. Also the invention relates to system and method which allows all devices within the wireless personal area network to reserve channel time for any other purpose than data communication, without the need and assistance of a centralized coordination device, in a completely distributed manner. The system for the invention comprises of a distributed medium access control mechanism involving a superframe structure made up of timing slots where all inter device communication takes place within the time slots. The present invention comprises of system and method which would solve the problems associated with current art, in the following manner: 1. In the current invention, the beacon frame is enhanced to include a new entity called Data Slot Reservation Indicator (DSRI). DSRI contains information about the status of all the data slots from the viewpoint of the device sending this indicator. DSRI is sent by each device as a part of its beacon frame. In other words, DSRI represents the availability of the device for a slot (can be MAS or any other slot in superframe) from the point of view of device itself. Device can be unavailable for different reasons, e.g. due to reservation of neighbor, 2. When a device listens to the beacon belonging to a neighboring device, it receives the DSRI and therefore can know the status of data slots from the neighboring device's viewpoint, thus finding out all the slots when the neighboring device is indulging in communication (transmitting or receiving), when it is free, etc. 3. Each device updates its DSRI using the DSRI from other neighboring nodes (as received in their beacons). Each device includes its updated DSRI in each beacon sent by it. 4. By using the DSRI information, in invention, mechanism is provided for a source device to find and decide the slots where it can initiate communication (data transfer) with the destination device. 5. Mechanism is also provided for the source device to initiate resen/ation of the free slot with the destination device and to avoid, detect and resolve resolution confiicts with another pair of devices trying to reserve the same slot at the same time. 6. Mechanism is also provided to cancel or terminate the reservation at the end of communication or whenever the slot is no longer desired. 7. It is another object of the present invention to provide information to assist the devices to select the needed parameters for the operation of the communication mechanism employed between them during the reserved slots. 8. The present invention incorporates the ability to differentiate the multicast (No-ACK) and unicast (With ACK) streams and to provide reservation suited to the specific type of stream. This allows for better channel utilization and effective sharing of resources. Accordingly this invention explains a system for channel time reservation in wireless personal area networks in the media access layer the said system comprising: • Data Slot Reservation Indicator (DSRI), that is included and sent in every beacon by each device and contains information about the status of all the data slots ; • DS-Req Information Element, to reserve slots between the source and destination; • DS-Res Information Element, to respond to slot reservation requests from the source; • DS-ACK Information Element, to respond to complete the three way handshake for slot reservation between the source and destination device; and • DS-NACK Information Element, to signal cancellation or termination of slot reservation between the source and destination device. Accordingly this invention explains a method for channel time reservation in wireless personal area networks in the media access layer the said method comprising the steps of: • Calculation of DSRI; and • Data Slot Reservation ,where the Inter device communication takes place in the reserved data slots; • Wherein the data slot reservation between Source and Destination is divided into Free Slot Determination Procedure and Data Slot Reservation Procedure. 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 wireless personal area network, which is based on IEEE-802.15.3 and shows the Centralized media access control approach 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 Distributed media access control approach in wireless personal area network, which does not have any centralized coordinator. The various DEV are shown as dark circles (bullets) with their ranges in circles. The devices cooperate and share information with each other to perform the media access control operations. Figure 3 illustrates the skeleton of beacon slots and data slots within the superframe. The numbers such as superframe duration, number of beacon slots and number of data slots are indicative. A change in these numbers does not affect the operation of the present invention. Figure 4 illustrates the structure of the Data Slot Reservation Indicator (DSRI) which is sent in every beacon. Figure 5 illustrates the format of the Data Slot reservation Request Information Element (DS-Req IE) Figure 6 illustrates the format of the Data Slot reservation Response Information Element (DS-Res IE) Figure 7 illustrates the format of the Data Slot reservation ACK Information Element (DS-ACK IE) Figure 8 illustrates the format of the Data Slot reservation Negative ACK Information Element (DS-NACK IE) Figure 9 illustrates the scenario of two multicast streams in 2 hop neighborhood Figure 10 illustrates the scenario of two unicast streams in 2 hop neighborhood Figure 11 illustrates Scenario 1 of reservation conflict and resolution Figure 12 illustrates Scenario 2 of reservation conflict and resolution Figure 13 illustrates Scenario 3 of reservation conflict and resolution Figure 14 illustrates Scenario 4 of reservation conflict and resolution Figure 15 illustrates the state diagram for the Slot Reservation Procedure. DETAiLED DESCRIPTiON OF THE INVENTION The present invention relates to a system that allows devices to share channel time in a completely distributed manner in the Wireless Personal Area Networks based on mobile ad-hoc networks. The invention relates to system and method which allows all devices to reserve channel time for their use in a completely distributed manner without the need for a centralized coordinator. The system for the invention comprises of a distributed medium access control mechanism involving a superframe structure made up of timing slots where all inter device communication takes place within the time slots. The slots may be reserved by the devices for their communication needs. Slots are reserved in a completely distributed manner without the need for any centralized coordinator. The system and method of the invention comprises of new entity, Data Slot Reservation Indicator (DSRI) that is included and sent in every beacon by each device and contains information about the status of all the data slots from the viewpoint of that device. DSRI helps the devices to determine the slots in which the reservation can possibly take place with the destination device. The reservation is then accomplished using the Data Slot Reservation Procedure. Accordingly, the invention provides a method to avoid, detect and resolve data slot reservation conflicts. Accordingly, the invention provides a method to improve the channel access by providing information of availability about the status of all the slots. Accordingly, the invention also provides a method to spatially reuse the channel when the physical medium allows multiple channels to be used simultaneously in the same spatial region without co-channel interference. The subsequent subsections describe the individual entities to effect the invention. Figure 4 illustrates the proposed entity called DSRI. - Data Slot Reservation Indicator (DSRI) contains the availability information about the status of all the data slots in the superframe. It requires 3 bits to indicate the coded status of every data slot. For example, if the superframe has 256 data slots, the DSRI will be of size 96 Bytes. In case, the superframe has 128 data slots, the DSRI size is reduced to 48 Bytes. - DSRI is included in the beacon sent by each device. - When two or more triplets can be used to describe the status of a device, e.g. when it has a transmitter in neighborhood (101) and in addition it is a receiver for Unicast data (111), then the triplet with a higher value (111) is used as the value for the slot status in DSRI. - DSRI is used to determine the free slots for reservation between the devices. - DSRI can be extended to include information for multiple channels to allow spatial reuse, if such provision is made available by the underlying physical layer. It is also possible that DSRI can be of 2 bits for each slot, and then it can represent the availability of the device in the slot in a channel. Meaning of the bit values are as specified below: It is also possible that DSRI can be of 1 bit for each slot, and then it can represent the availability of the device in the slot in a channel, which might not represent the what the device is doing in that slot. Meaning of the bit values are as specified below: The meaning of bit '0' and '1' may be exchanged but must be used consistently for all implementations. It must be noted that DRSl bitmap might be sent on each superframe or in some superframe, voluntarily by the device or on basis of request from some device. It is also possible that it might be sent in beacons in form of Information Element or with some other frames in some other form. The subsequent subsections describe the additional entities introduced to effect the invention. 1. DS-Req Information Element In order to reserve slots between the source and destination we introduce an Information Element, the Data Slot Request IE (DS-Req IE). Data Slot Request Information Element (DS-Req IE) is used by the source device to initiate reservation in the free slots with the destination device. The DS-Req IE contains all required information about the reservation including destination ID, slots, priority and type of stream. The format of DS-Req IE is shown in Figure 5. As shown in the figure, the DS-Req IE contains the following fields: - Destination ID: This is the ID of the device to which this reservation is targeted. - Number of slots: This represents the number of slots that are requested to be reserved. - Number of choices offered: This indicates about the number of choices the source has offered the destination to choose the slots from. The number of slots required to be chosen is given by the second field. Multiple choices may be offered by the source in case it is available to allow the destination to resolve reservation conflicts faster. - Slot numbers: This is a list of slots that the source has determined to be free for reservation with the destination. The total number of slots listed is given by the number of choices offered field. - Type: This field signifies the type of reservation. This nibble can take the following values explained here, but it can be other type of reservation with some other purpose in some other form or bit(s) values. - Priority: This field defines the priority of this reservation on a scale of 1 to 8. Higher number specifies higher priority. Higher priority streams are given preference in case of reservation conflicts. Priority of a reservation is a QoS parameter and is defined by the upper layers and the devices should refrain from using more priority than required for reservation. - Random number: This number is used to resolve reservation conflicts in case of multiple reservations with same priority. The reservation with a higher random number is given preference. - Stream ID: This is used as a unique identifier for this reservation between the source and destination. This is required to uniquely identify a particular reservation request in cases where reservations for many streams may be simultaneously underway between source and desfination. Data slot reservation in the present invention is a source initiated procedure. DS-Req IE is sent as part of the beacon by the source whenever reservation is required. Since all devices listen to beacons of all neighboring devices in the network, therefore, all devices Including the destination receive the request for slot reservation. The desfination device, as identified by the destination ID included as a field in the DS-Req IE, is required to respond to the IE. All other devices excluding that device are required to make note of the DS-Req IE to aid in reservation conflict detection and resolution. DS-Req IE can be sent as part of beacon or it can be sent as a part of some other frame with some other name with same purpose as described above. 2. DS-Res Information Element In order to respond to slot reservation requests from the source, we introduce an Information Element, the Data Slot Response IE (DS-Res IE). Data Slot Response Information Element (DS-Res IE) is used by the destination device to respond to the DS- Req IE for reservation request sent by the source device. The DS-Res IE contains the response of the destination (Accept or Decline). In case the destination accepts the request, then required information about the response including destination ID, slots, priority and type of stream are also specified with correct values. The format of DS-Res IE is shown in Figure 6. As shown in the figure, the DS-Res IE contains the following fields: - Destination ID: This is the ID of the device to which this response is targeted. - Response: This informs the source about the response of the destination. This can take the following values - Response values mentioned here are may not be only values there can be other values possible for some purpose of indication of response. - Number of slots accepted: This tells about the number of slots on which the destination has accepted the reservation. The destination may choose to select fewer slots than requested by source for some reason. In case the response field has any value except 0x00, the value of this field should be 0x00. - Slot numbers: This is a list of slots that's the source has determined to be free for reservation with the destination. The total number of slots listed is given by the number of slots accepted field. - Type: This field signifies the type of reservation. This field must have the same value as the type field of the DS-Req IE for which this response is being generated. Priority: This field defines the priority of this reservation on a scale of 1 to 8. Higher number specifies higher priority. Higher priority streams are given preference in case of reservation conflicts. Priority of a reservation is a QoS parameter and is defined by the upper layers and the devices should refrain from using more priority than required for reservation. - Random number: This number is used to resolve reservation conflicts in case of multiple reservations with same priority. The reservation with a higher random number is given preference. - Stream ID: This is the same unique identifier that was sent as part of the DS-Req IE for which this response is generated. This is required to uniquely identify a particular reservation request in cases where reservations for many streams may be simultaneously underway between source and destination. DS-Req IE is sent as part of the beacon by the destination in the next superframe after receiving the DS-Req IE from some source device. As previously mentioned, all devices listen to beacons of all neighboring devices in the network. Hence, all devices including the requester device which sent the DS-Req IE in the previous superframe, receive the response for slot reservation. The device, as identified by the destination ID included as a field in the DS-Res IE, is required to respond to the IE. All other devices excluding that device are required to make note of the DS-Res IE to aid in reservation conflict detection and resolution. DS-Res IE can be sent as part of beacon or it can be sent as a part of some other frame with some other name with same purpose as described above. 3. DS-ACK Information Element In order to respond to complete the three way handshake for slot reservation between the source and destination device, we introduce an Information Element, the Data Slot ACKnowledgement IE (DS-ACK IE). Data Slot ACK Information Element is used by a device to Acknowledge the DS-Res IE (sent as a response to the DS-Req IE sent by this device), thus completing the three-way handshake required to reserve a slot successfully. The DS-ACK IE from the reservation requestor to the destination signifies that the requestor has accepted the reservation parameters and data transmission can now begin. DS-ACK IE needs to be sent only in case the requestor is satisfied with the reservation parameters as responded by the destination. Only the DS-Res lE's which accept the reservation request need to be acknowledged using DS-ACK. In addition, if the initiator of the reservation is dissatisfied with the parameters of reservation accepted by the destination, as responded back in the DS-Res IE, then there is no need to acknowledge the DS-Res IE. The format of DS-ACK IE is shown in Figure 7. As shown in the figure, the DS-ACK IE contains the following fields: - Destination ID: This is the ID of the device to which this acknowledgement is targeted. - Type: This field signifies the type of reservation. - Stream ID: This is the same unique identifier that was sent as part of the DS-Req IE for which this response is generated. This is required to uniquely identify a particular reservation request in cases where reservations for many streams may be simultaneously underway between source and destination. The transmission of the DS-ACK IE in the superframe, after the superframe in which the DS-Res IE was received, signifies the completion of reservation procedure from the side of the requestor. The requestor will now get ready for data transmission in the reserved slot/slots starting from the same superframe in which the DS-ACK IE was sent. DS-ACK IE is sent as part of the beacon by the reservation requestor in the next superframe after receiving the DS-Res IE from some device targeted to it. As previously mentioned, all devices listen to beacons of all neighboring devices in the network. Hence, all devices, including the device which sent the DS-Res IE in the previous superframe, receive the acknowledgement for slot reservation. The device, as identified by the destination ID included as a field in the DS-ACK IE, is required to get ready for data reception in the acknowledged slots. All other devices excluding that device are required to make note of the DS-ACK IE to aid in reservation conflict detection and resolution. DS-ACK IE can be sent as part of beacon or it can be sent as a part of some other frame with some other name with same purpose as described above. 4. DS-NACK Information Element In order to signal cancellation or termination of slot reservation between the source and destination device, we introduce an Information Element, the Data Slot Negative ACKnowledgement IE (DS-NACK IE). The DS-NACK IE from any device during the reservation stage signals the cancellation of the reservation for the mentioned reason. The reason includes inability to reserve due to reservation conflicts or any other reason at the device end. The DS-NACK IE from any device after successful reservation signals the intent to terminate the stream. Usually the termination will be initiated by the source device. No acknowledgement is solicited for the DS-NACK IE and the stream or reservation stands cancelled with immediate effect. The DS-NACK IE, when it appears during the reservation procedure is used to signal the cancellation of the reservation underway. The DS-NACK IE, when it appears after the reservation is successfully completed and communication is in progress is used to signal the formal termination of the stream. The format of DS-NACK IE is shown in Figure 8. As shown in the figure, the DS-NACK IE contains the following fields: - Destination ID; This is the ID of the device to which this negative acknowledgement is targeted. - Stream ID: This is the unique identifier that identifies which stream or reservation to terminate. - Type: This field signifies the type of reservation. DS-NACK IE plays an important role in collision resolution as will be described in detail later. DS-NACK IE is sent as part of the beacon by a device. All devices, including the target device, listen to beacons of all neighboring devices in the network and receive the acknowledgement for slot reservation. The device, as identified by the destination ID included as a field in the DS-NACK IE, is required to cancel the reservation or terminate the stream as identified by the stream ID. All other devices excluding that device can simply neglect the DS-NACK IE. DS-NACK IE can be sent as part of beacon or it can be sent as a part of some other frame with some other name with same purpose as described above. The subsequent subsections describe the operation of the invention: 1 Calculation of DSRI All devices include DSRI in their beacons. Each device update its DSRI using me DSRI OT neighboring devices as well as based on what it is doing in the data slots. Whether or not a device is interested in reservation of slots, it is required for it to keep its DSRI updated and to include the updated DSRI in every beacon sent by it. DSRI contains information about the status of every data slot in the superframe from the viewpoint of the device. This simply means that in the triplet of any slot in the DSRI, the device reports what it does in that slot. If the device does not do anything then it reports if its neighborhood is doing something. In case the neighborhood also does nothing then the value of 000 for the triplet is used. The DSRI calculation procedure is very simple as written below. The triplet in DSRI for each slot 'x' can take one of 5 values. The possible values for the triplets, along with explanation, have been listed in a table earlier in the document. The triplet in DSRI for some slot 'x' is: - '111': If this device is the transmitter of a Unicast or multicast stream in this slot or this device is a receiver of a Unicast stream in this slot. - *110': If this device is the receiver of a multicast stream in this slot - Else the value is determined by the following procedure a. List down the triplets corresponding to slot 'x* from the DSRI of all the neighbors as received with the beacons in the beacon period. b. Find the triplet having the maximum value from the list in (a) c. Use the DSRI mapping table as given below to obtain the mapped triplet using the triplet found in (b) f d. The mapped triplet is the value to be put for slot 'x' in the DSRI of this device I \ 1 DSRI is calculated and updated each time a new beacon is received by a device. This way DSRI calculation becomes an integral part of beacon frame processing at each device and the device always has the latest updated DSRI. The device sends this DSRI as part of its beacon to help other devices to update their DSRI. This way information about slot reservation and status of data slots is disseminated and distributed across the network. It should be noted that DSRI should be calculated and updated on periodic basis, this period can be a superframe or may be less or more than that. Also, DSRI calculation which can be called as formation of DSRI, can be different on definition of DSRI bit values, it can also be different in case of number of bit used for DSRI. In other words DSRI represents the availability status of the slot including what activity is going on by the device, in that slot. Again, it is a representation of information of own activity and information of neighbors activity in the slot. Again, it is propagation of neighbor's information to other neighbors, means propagation of information till 2-hop neighborhood. 2. Data Slot Reservation The data period is divided into a number of slots. Inter device communication takes place in the reserved data slots. Slots may be reserved by the devices for their communication needs. Slots in data period, in the superframe, can be reserved for isochronous or asynchronous streams by a request response acknowledge based three way handshake. If Source S gets positive response for the request command from the destination D, then those slots should be reserved both by the source and destination and the status updated in their DSRI. The current invention has the ability to distinguish, based upon their properties, the multicast and Unicast streams. Accordingly, the data slot reservation procedure is detailed. As seen from Figure 9, two multicast streams can share the two hop neighborhood and exist without interfering with each other. This is because multicast streams in a slot involve completely unidirectional traffic and acknowledgement from the receivers is not solicited as part of multicast transmission. On the other hand, two Unicast streams (Figure 10) cannot exist in the 2 hop neighborhood since either the transmitters or the receivers will interfere. This is because Unicast streams are bidirectional since the transmitter solicits regular acknowledgement from the receiver and the acknowledgements are sent in the same reserved channel time. Herein we detail the various operations related to the operation of data slot reservation mechanism. The procedure for data slot reservation between Source S and Destination D is divided into two steps: (A) Free Slot Determination Procedure and; (B) Data Slot Reservation Procedure. A, Free Slot Determination Procedure The first step in slot reservation involves determining a common free slot in which the transmitter is free to transmit and receiver is free to receive. Since the scheme is completely distributed in nature, the presence of neighboring nodes, which may be in the send or receive mode in some slots, must be taken into account. The DSRI, as proposed in the invention, helps in the Free Slot Determination Procedure by giving the source node the view of the data slots from the destination point of view. Since the slot reservation procedure is "source initiated", the following steps detail the procedure at the source to determine such free slot-channel pairs: 1 S (source device) should first determine the slots in the data period where it is free to transmit to D (destination device). As seen from the DSRI triplet value table, the slots, where the triplet value is *000', will be free for the source to transmit. 2 Next. S determines the slots where D is free to receive. This is handled differently for the case of multicast and Unicast streams, to account for the differences between the two streams (i.e. multicast streams do not require acknowledgement within the same data slot). i. If S is interested to start a multicast streams then it selects the slots, in which the DSRI of D is either of the triplets '000' or '100' ii. If S Is interested to start a unicast streams then it selects the slots, in which the DSRI of D is the triplets '000'. 3 The slots which are free for both S and D, as determined in steps 1 and 2 above, are the common free slots and can be used for reservation between S and D. 4 If no common free slots are found, then there exist no slots in which the source device can have reservation with destination device. In such a case the source device needs to wait for some time before trying to find the free slots again. If a free slot-channel is found, then the Data Slot Reservation Procedure is used to reserve the slot. It must be noted that, free slot finding procedure can be used without multicast spatial reuse and multiple channel, but it uses DSRI bits of source and destination(s) in any possible form and finds the free slot if DSRI indicates the slot as free. B. Data Slot Reservation Procedure The Data Slot Reservation Procedure is the method using which the common free slots between a pair of devices are reserved for communication (data transfer) purpose. Once a free slot is determined using the Free Slot Determination Procedure, reservation involves message exchange between the source and destination in a Request/Response manner. The following steps detail the Data Slot Reservation Procedure: 1 The source includes a DS-Req IE in its beacon, which contains details about the destination ID, number of slots to be reserved, list of common free slots, type of reservation (isochronous, asynchronous, broadcast, multicast, etc), priority, a random number and a stream ID (the stream ID is used to differentiate various requests from the same source). If possible, the source includes multiple choices of slots for reservation. For example, if the source wants to reserve a single slot and multiple slots are determined to be free for reservation, then the source should mark number of slots to be reserved as 1 but still include multiple slots in the request to give the destination a choice of accepting one slot from the many available options. This reduces the overall time required for a successful Data Slot Reservation Procedure in scenarios where multiple node pairs are trying to reserve slots and some of those reservations may unknowingly be for the same slot. 2 The destination can accept the request on any of the slots if multiple choices for slots are provided as part of the reservation request. Destination accepts the request if it finds that no other neighbor node has, in the meanwhile, finished the Data Slot Reservation Procedure for the same slot. Otherwise it has to choose another slot (from the multiple choices provided by the source). If no slot can be chosen, then the destination rejects the request. The appropriate response (ACCEPT or REJECT) is sent back as a DS-Res IE in the beacon of the destination. 3 In case the destination hears multiple requests for slot reservations between pair of nodes with at least one request directed towards it, it undertakes reservation conflict resolution mechanism. In such a case the destination compares the requests directed to it with other requests based firstly on higher priority and secondly on a higher random number. The destination accepts the request directed towards it if this request wins this comparison, othenA^ise it rejects this request from the source. Also, instead of rejecting, if the source has provided multiple choices for slots then the destination can accept the request on another slot for which it wins the comparison, and for which there is no other reservation between any pair of nodes. 4 In case that along with the DS-Req IE from the source, the destination also hears DS-Rsp lEs from one or more neighboring nodes which may have accepted their respective DS-Rsp, then the destination cannot accept the DS-Req in that particular slot. This provision ensures first-start-first-reserve for reservations for same slot. The destination is free to accept the DS-Req on any other slot if multiple options are provided by the source. 5 The destination updates its DSRi only when it sends an ACCEPT in the DS-Res IE. By updating, it reserves that slot in its DSRI so that other device pairs cannot reserve that slot. 6 On getting an accept response, the source should ACK the response in the next superframe (by sending DS-ACK IE). The ACK follows with the data in the reserved data slot and channel in the Data Period of the same superframe. The DSRI of the source is updated when it decides on positive ACK. 7 At any time, including step 7, if the destination finds out that another simultaneous reservation for the same slot is conflicting with this reservation, then the destination needs to cancel the reservation by sending a DS-NACK IE in its beacon to the source device. Hence, in step 6 communication takes place in the slot if and only if source sends a DS-ACK IE and the destination has not included a DS-NACK IE in its beacon in the same superframe, in which case the reservation stands cancelled due to reservation conflict. 8 If the source, between sending the DS-Req IE and receiving the ACCEPT (from DS-Res IE), has heard ACCEPT for the same slot from another device, then the source cannot ACK to the destination and data transfer cannot begin. In such a case, the source may send a DS-Req IE again (same as starting from step 1 again) with other slots if some are free or the source sends a NACK to cancel the current reservation procedure. 9 The destination on receiving a NACK (from DS-NACK IE) updates its DSRI removing the slot reservation it made earlier while sending the ACCEPT in step 5. 10 The destination, on hearing an ACK from the source will wait for the data in the reserved slot in the reserved channel. This is when no conflict has been discovered by any of source or destination device and the reservation can result in a valid and successful data transfer. This completes the Data Slot Reservation Procedure. It should be noted that reservation procedure can be carried over by beacon or by some other means like command frame. Figures 10, 11, 12, 13, 14 illustrate the four scenarios which may arise during reservation conflict detection and resolution. The scenarios show two pair of devices trying to reserve the slots where one pair has a higher priority and the other has a lower. The scenarios illustrate how the various conflicts are resolved, as per Data Slot Reservation Procedure and it can be seen that the pair of devices with higher priority always gets the reservation. The decision point in case of all reservations is also indicated. In case when a multiple number of such pairs of devices are reserving the same slot, then the same principle can be extended to reserve the slots with the slot being given to the pair having a higher priority reservation. A Schematic State diagram for the Slot Reservation Procedure is given in Figure 15. 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 ACK: Acknowledgement BP: Beacon Period BPST: Beacon Period Start Time DEV: Device DEVID: Device Identifier DP: Data Period DS-ACK IE: Data Slot reservation ACK Information Element DS-NACK IE: Data Slot reservation Negative ACK Information Element DS-Req IE: Data Slot reservation Request Information Element DS-Res IE: Data Slot reservation Response Information Element DSRI: Data Slot Reservation Indicator EDCA: Enhanced Distributed Channel Access ID: Identifier IE: Information Element IEEE: Institute of Electrical and Electronics Engineers MAC: Medium Access Control MAS: Medium Access Slot MBOA: Mult) Band OFDM Alliance MSC: Message Sequence Chart NACK: Negative Acknowledgement OFDM: Orthogonal Frequency Division Multiplexing PHY: Physical Layer PNC: Piconet Coordinator QoS: Quality of Service UWB: Ultra Wide Band WPAN: Wireless Personal Area Network WE CLAIM 1. A system for channel time reservation in wireless personal area networks in the media access layer the said system comprising: Data Slot Reservation Indicator (DSRI), that is included and sent in beacon by each device and contains information about the status of all the data slots; DS-Req Information Element, to reserve slots between the source and destination; DS-Res Information Element, to respond to slot reservation requests from the source; DS-ACK Information Element, to respond to complete the three way handshake for slot reservation between the source and destination device; and DS-NACK Information Element, to signal cancellation or termination of slot reservation between the source and destination device. 2. A system as claimed in claim 1 wherein the reservation is accomplished using the Data Slot Reservation Procedure. 3. A system as claimed in claim 1 wherein DSRI contains the availability information about the status of ail the data slots in the superframe where DSRI requires 3 bits to indicate the coded status of every data slot. 4. A system as claimed in claim 1 wherein DSRI is included in at least one beacon sent by the device. 5. A system as claimed in claim 1 wherein DSRI is used to determine the free slots for reservation between the devices and DSRI is extended to include information for multiple channels to allow spatial reuse, when a provision is made available by the underlying physical layer. 6. A system as claimed in claim 1 wherein DSRI requires 2 bits for each slot, for representing the availability of the device in the slot in a channel. 7. A system as claimed in claim 1 wherein DSRI requires 1 bit for each slot, for representing the availability of the device in the slot in a channel, which may not represent what the device is doing in that slot. 8. A system as claimed in claim 1 wherein DRSI bitmap is sent during each superframe or in some superframe, voluntarily by the device or on basis of request from some device. 9. A system as claimed in claim 1 wherein DRSI bitmap is sent in beacons in form of Information Element. 10. A system as claimed in claim 1 wherein Data Slot Request Information Element (DS-Req IE) is used by the source device to initiate reservation in the free slots with the destination device. 11. A system as claimed in claim 10 wherein the DS-Req IE contains all required information about the reservation including destination ID, slots, priority and type of stream. 12. A system as claimed in claim 10 wherein DS-Req IE contains : Destination ID, to which this reservation request is targeted; Number of slots, which represents the number of slots that are requested to be reserved; Number of choices offered, which indicates about the number of choices the source has offered the destination to choose the slots from; Slot numbers which is a list of slots that the source has determined to be free for reservation with the destination; Type, which signifies the type of reservation; Priority, which the field defines the priority of this reservation on a scale of 1 to 8; Random number which is used to resolve reservation conflicts In case of multiple reservations with same priority where the reservation with a higher random number is given preference; and Stream ID which is a unique identifier for this reservation between the source and destination where the said ID is required to uniquely identify a particular reservation request in cases where reservations for many streams may be simultaneously unden/vay between source and destination. 13. A system as claimed in claim 12 wherein multiple choices is offered by the source in case it is available to allow the destination to resolve reservation conflicts faster. 14. A system as claimed in claim 12 wherein higher number for priority field specifies higher priority and the higher priority streams are given preference in case of reservation conflicts. 15. A system as claimed in claim 12 wherein DS-Req IE is sent as part of the beacon or is sent by some other mean by the source whenever reservation is required. 16. A system as claimed in claim 10 wherein as all devices listen to beacons of all neighboring devices in the network, all devices including the destination receive the request for slot reservation or destination device receives the reservation request by some other mean. 17. A system as claimed in claim 10 wherein the destination device, as identified by the destination ID included as a field in the DS-Req IE, respond to the IE and all other devices excluding that device make note of the DS-Req IE to aid in reservation conflict detection and resolution. 18. A system as claimed in claim 10 wherein Data Slot Response Information Element is used by the destination device to respond to the DS-Req IE for reservation request sent by the source device. 19. A system as claimed in claim 18 wherein the DS-Res IE contains the response of the destination and if the destination accepts the request, then required information about the response including destination ID, slots, priority and type of stream are specified. 20. A system as claimed in claim 18 wherein the DS-Res IE contains the following fields: Destination ID, which is the ID of the device to which this response is targeted; Response, which informs the source about the response of the destination; Number of slots accepted, which tells about the number of slots on which the destination has accepted the reservation; Slot numbers, which is a list of slots, that the source has determined to be free for reservation with the destination; Type, which signifies the type of reservation; Priority, which defines the priority of this reservation on a scale of 1 to 8; Random number, which is used to resolve reservation conflicts in case of multiple reservations with same priority where the reservation with a higher random number is given preference; and Stream ID which is the same unique identifier that was sent as part of the DS-Req IE for which this response is generated. 21. A system as claimed in claim 18 wherein DS-Req IE is sent as part of the beacon by the destination in the next superframe after receiving the DS-Req IE from source device or by some other mean. 22. A system as claimed in claim 18 wherein all devices listen to beacons of all neighboring devices in the network and all devices including the requester device which sent the DS-Req IE in the previous superframe, receive the response for slot reservation or receive the response by some other mean. 23. A system as claimed in claim 18 wherein the device, as identified by the destination ID included as a field in the DS-Res IE, is required to respond to the IE and all other devices excluding that device are required to make note of the DS-Res IE to aid in reservation conflict detection and resolution. 24. A system as claimed in claim 18 wherein DS-Res IE is sent as part of beacon or it is sent as a part of some other frame. 25. A system as claimed in claim 1 wherein Data Slot ACK Information Element is used by a device to Acknowledge the DS-Res IE for completing the three-way handshake required to reserve a slot successfully. 26. A system as claimed in claim 25 wherein the DS-ACK IE from the reservation requestor to the destination signifies that the requestor has accepted the reservation parameters and data transmission can begin. 27. A system as claimed in claim 25 wherein DS-ACK IE is sent only in case the requestor is satisfied with the reservation parameters as responded by the destination. 28. A system as claimed in claim 25 wherein only the DS-Res lE's which accept the reservation request are acknowledged using DS-ACK. 29. A system as claimed in claim 25 wherein, if the initiator of the reservation is dissatisfied with the parameters of reservation accepted by the destination, as responded back in the DS-Res IE, then no acknowledgement is sent for the DS-Res IE. 30. A system as claimed in claim 25 wherein the DS-ACK IE contains the following fields: Destination ID, which is the ID of the device to which this acknowledgement is targeted; Type, which signifies the type of reservation; and Stream ID, which is the same unique identifier that was sent as part of the DS-Req IE for which the response is generated. 31. A system as claimed in claim 25 wherein the transmission of the DS-ACK IE in the superframe, after the superframe in which the DS-Res IE was received, signifies the completion of reservation procedure from the side of the requestor and the requestor can get ready for data transmission in the reserved slot or slots starting from the same superframe in which the DS-ACK IE was sent. 32. A system as claimed in claim 25 wherein DS-ACK IE is sent as part of the beacon by the reservation requestor in the next superframe after receiving the DS-Res IE from a device targeted to it or it is sent by some other mean. 33. A system as claimed in claim 25 wherein, all devices listen to beacons of all neighboring devices in the network and all devices, including the device which sent the DS-Res IE in the previous superframe, receive the acknowledgement for slot reservation or is received by some other mean. 34. A system as claimed in claim 25 wherein the device, as identified by the destination ID included as a field in the DS-ACK IE, gets ready for data reception in the acknowledged slots and all other devices excluding that device makes note of the DS-ACK IE to aid in reservation conflict detection and resolution. 35. A system as claimed in claim 25 wherein DS-ACK IE is sent as part of beacon or it is sent as a part of some other frame. 36. A system as claimed in claim 1 wherein the Data Slot Negative Acknowledgement IE (DS-NACK IE) from any device during the reservation stage signals the cancellation of the reservation for the mentioned reason. 37. A system as claimed in claim 36 wherein the said reason includes inability to reserve due to reservation conflicts or any other reason at the device end. 38. A system as claimed in claim 36 wherein the DS-NACK IE from any device after successful reservation signals the termination of the stream and the termination is initiated by the source device and No acknowledgement is solicited for the DS-NACK IE and the stream or reservation stands gets cancelled. 39. A system as claimed in claim 36 wherein the DS-NACK IE. appearing during the reservation procedure is used to signal the cancellation of the reservation undenvay, 40. A system as claimed in claim 36 wherein DS-NACK IE, when appears after the reservation is successfully completed and communication is in progress is used to signal the formal termination of the stream. 41. A system as claimed in claim 36 wherein the DS-NACK IE contains the following fields: Destination ID, which is the ID of the device to which this negative acknowledgement is targeted; Stream ID, which is the unique identifier that identifies which stream or reservation to terminate; and Type, which signifies the type of reservation. 42. A system as claimed in claim 36 wherein DS-NACK IE is sent as part of the beacon by a device and all devices, including the target device, listen to beacons of all neighboring devices in the network and receive the acknowledgement for slot reservation or sent by some other mean. 43. A system as claimed in claim 36 wherein the device, as identified by the destination ID included in the DS-NACK IE, is required to cancel the reservation or termination of the stream as identified by the stream ID and all other devices excluding that device neglects the DS-NACK IE. 44. A system as claimed in claim 36 wherein DS-NACK IE is sent as part of beacon or it is sent as a part of some other frame. 45. A method for channel time reservation in wireless personal area networks in the media access layer the said method comprising the steps of: Calculation of DSRI; and Data Slot Reservation, where the inter device communication takes place in the reserved data slots; - Wherein the data slot reservation between Source and Destination is divided into Free Slot Determination Procedure and Data Slot Reservation Procedure. 46. A method as claimed in claim 45 wherein at least one device include DSRI in its beacons and the device updates its DSRI using the received DSRI of neighboring devices as well as based on what it is doing in the data slots. 47. A method as claimed in claim 45 wherein whether or not a device is interested in reservation of slots, DSRI gets updated and the updated DSRI is sent in at least one beacon. 48. A method as claimed in claim 45 wherein DSRI contains information about the status of each data slot in the superframe where in the status information made up of one or more bits of any slot in the DSRI, the device reports what it does in that slot. 49. A method as claimed in claim 45 wherein if the device does not do anything then it reports if its neighborhood is doing something and if the neighborhood does nothing then the value of 000 for the triplet is used or it is considered free to reserved or available or unused. 50. A method as claimed in claim 45 wherein the triplet in DSRI for a slot 'x' is: 111: If this device is the transmitter of a unicast or multicast stream in this slot or this device is a receiver of a unicast stream in this slot; 110': If this device is the receiver of a multicast stream in this slot; Else the value is determined by: - Listing down the triplets corresponding to slot 'x' from the DSRI of all neighbors as received with the beacons in the beacon period; - Finding the triplet having the maximum value; - Using the DSRI mapping table to obtain the mapped triplet; and - putting a value for slot 'x' in the DSRI of this device which is the mapped triplet. 51. A method as claimed in claim 45 wherein DSRI is calculated and updated each time a new beacon is received by a device and the device sends and new DSRI received from some other devices or device notices change in neighborhood or change in neighbor's behavior or change in its own behavior. 52. A method as claimed in claim 45 wherein DSRI is calculated and updated on periodic basic, where the said period is a superframe or less or more than the superframe. 53. A method as claimed in claim 45 wherein the data period is divided into a number of slots where the slots is reserved by the devices for their communication. 54. A method as claimed in claim 45 wherein slots in data period, in the superframe, is reserved for isochronous or asynchronous streams by a request response acknowledge based three way handshake. 55. A method as claimed in claim 45 wherein if source gets positive response for the request command from the destination , then those slots are reserved both by the source and destination and the status gets updated in their DSRI. 56. A method as claimed in claim 45 wherein, two multicast streams share the two hop neighborhood and exist without interfering with each other where multicast streams in a slot contain completely unidirectional traffic and no acknowledgement from the receivers. 57. A method as claimed in claim 45 wherein two unicast streams do not exist in the 2 hop neighborhood as either the transmitters or the receivers will interfere as the unicast streams are bidirectional and with regular acknowledgement from the receiver and the acknowledgements are sent in the same reserved channel time. 58. A method as claimed in claim 45 wherein the procedure for data slot reservation between Source and Destination is divided into Free Slot Determination Procedure and Data Slot Reservation Procedure. 59. A method as claimed in claim 58 wherein Free Slot Determination Procedure involves determining a common free slot in which the transmitter is free to transmit and receiver is free to receive. 60. A method as claimed in claim 58 wherein the source device determines the slots in the data period where it is free to transmit to destination device. 61. A method as claimed in claim 58 wherein source determines the slots where destination is free to receive. 62. A method as claimed in claim 58 wherein if source is interested to start a multicast streams then it selects the slots, in which the DSRI of destination is either of the triplets '000'or'100'. 63. A method as claimed in claim 58 wherein if source is interested to start a unicast streams then it selects the slots, in which the DSRI of Destination is the triplets '00064. A method as claimed in claim 58 wherein the slots which are free for both Source and Destination, are the common free slots that are used for reservation between Source and Destination. 65. A method as claimed in claim 59 where if no common free slots are found, there are no slots in which the source device can have reservation with destination device wherein the source device waits for some time before trying to find the free slots again and if a free slot-channel is found, then the Data Slot Reservation Procedure is used to reserve the slot. 66. A method as claimed in claim 59 wherein the said method uses DSRI bits of source and destination in any possible form and finds the free slot if DSRI of source and destination indicates the slot as free. 67. A method as claimed in claim 58 wherein in Data Slot Reservation Procedure the source includes a DS-Req IE in its beacon, which contains details about the destination ID, number of slots to be reserved, list of common free slots, type of reservation, priority, a random number and a stream ID. 68. A method as claimed in claim 67 wherein the source includes multiple choices of slots for reservation. 69. A method as claimed in claim 67 wherein the destination accepts the request on any of the slots if multiple choices for slots are provided as part of the reservation request and the destination accepts the request if it finds that no other neighbor node has finished the Data Slot Reservation Procedure for the same slot else it chooses another slot from the multiple choices provided by the source. 70. A method as claimed in claim 67 wherein if no slot is chosen, then the destination rejects the request and the appropriate response is sent back as a DS-Res IE in the beacon of the destination. 71. A method as claimed in claim 67 wherein in case the destination listens multiple reservation requests for same slot between pair of nodes with at least one request directed towards it, it undertakes reservation conflict resolution mechanism where the destination compares the requests directed to it with other requests based firstly on higher priority and secondly on a higher random number. 72. A method as claimed in claim 67 wherein the destination accepts the request directed towards it if the request wins the comparison; else it rejects this request from the source. 73. A method as claimed in claim 67 wherein instead of rejecting, if the source has provided multiple choices for slots then the destination accepts the request on another slot for which it wins the comparison, and for which there is no other reservation between any pair of nodes. 74. A method as claimed in claim 67 wherein if along with the DS-Req IE from the source, the destination also hears DS-Rsp lEs from one or more neighboring nodes which have accepted their respective DS-Rsp, then the destination cannot accept the DS-Req in that particular slot where the destination is free to accept the DS-Req on any other slot if multiple options are provided by the source. 75. A method as claimed in claim 67 wherein the destination updates its DSRI only when it sends an ACCEPT in the DS-Res IE. And by updating, it reserves that slot in its DSRI so that other device pairs cannot reserve that slot. 76. A method as claimed in claim 67 wherein on getting an accept response, the source ACK the response in the next superframe by sending DS-ACK IE and the ACK follows with the data in the reserved data slot and channel in the Data Period of the same superframe where the DSRI of the source is updated when it decides on positive ACK. 77. A method as claimed in claim 67 wherein if the destination finds out that another simultaneous reservation for the same slot is conflicting with this reservation, then the destination cancels the reservation by sending a DS-NACK IE to the source device. 78. A method as claimed in claim 67 wherein if the source, between sending the DS-Req IE and receiving the ACCEPT has heard ACCEPT for the same slot from another device, then the source does not ACK to the destination and data transfer does not begin where the source sends a DS-Req IE again with other slots if some are free or the source sends a NACK to cancel the current reservation procedure. 79. A method as claimed in claim 67 wherein the destination on receiving a NACK from DS-NACK IE updates its DSRI removing the slot reservation it made while sending the ACCEPT. 80. A method as claimed in claim 67 wherein the destination, on hearing an ACK from the source waits for the data in the reserved slot in the reserved channel when no conflict is discovered by any of source or destination device and the reservation results in a valid and successful data transfer. 81. A system for channel time reservation in wireless personal area networks in the media access layer substantially as herein described particularly with reference to the drawings. 82. A method for channel time reservation in wireless personal area networks in the media access layer substantially as herein described particularly with reference to the drawings.

Documents:

418-che-2004 abstract granted.pdf

418-che-2004 claims granted.pdf

418-che-2004 description (complete) granted.pdf

418-che-2004 drawings granted.pdf

418-che-2004-abstract.pdf

418-che-2004-claims.pdf

418-che-2004-correspondnece-others.pdf

418-che-2004-correspondnece-po.pdf

418-che-2004-description(complete).pdf

418-che-2004-description(provisional).pdf

418-che-2004-drawings.pdf

418-che-2004-form 1.pdf

418-che-2004-form 5.pdf

418-che-2004-form 9.pdf