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Efficient Availability Synchronization Scheme for IEEE 802.16 (WiMAX) Mesh and Relay Networks

IP.com Disclosure Number: IPCOM000169478D
Published in the IP.com Journal: Volume 8 Issue 5A (2008-05-08)
Included in the Prior Art Database: 2008-May-08
Document File: 6 page(s) / 209K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

IEEE (Institute of Electrical & Electronics Engineers) 802.16/WiMAX (Worldwide Interoperability for Microwave Access) networks have been specified for point-to-point and point-to-multipoint operation. In WiMAX TDMA (Time Division Multiple Access) is used for channel access, i.e. dedicated timeslots are reserved and granted for every transmission, so each participant in the network has his guaranteed time window for communication. However, the specification with its scheduling mechanism is not mesh-capable. The problem is illustrated in Figure 1 and the notation XY denotes node X having the status explained in Figure 2. Nodes A, B, and C have established a network (1a) and node A made a minislot reservation for transmitting data to node B. To this end, node A sent a request, the request was granted by B and confirmed by A. Node C overheard the grant message from node B but did not overhear the grant confirmation message from A (1b). Thus the slots in C are in the state receive available. Now a fourth node (node N) being neighbor to all other nodes joins the network (1c) and all slots of node N are still available. If N requests slots from C, C may include in its grant the same minislot range as A, which leads to a collision at B.

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Efficient Availability Synchronization Scheme for IEEE 802.16 (WiMAX) Mesh and Relay Networks

Idea: Parag Sudhir Mogre, DE-Darmstadt; Christian Schwingenschloegl, Ph.D., DE-Munich;
Matthias Hollick, Ph.D., DE-Darmstadt; Nico D`Heureuse, DE-Ladenburg

IEEE (Institute of Electrical & Electronics Engineers) 802.16/WiMAX (Worldwide Interoperability for Microwave Access) networks have been specified for point-to-point and point-to-multipoint operation. In WiMAX TDMA (Time Division Multiple Access) is used for channel access, i.e. dedicated timeslots are reserved and granted for every transmission, so each participant in the network has his guaranteed time window for communication. However, the specification with its scheduling mechanism is not mesh-capable.

The problem is illustrated in Figure 1 and the notation XY denotes node X having the status explained in Figure 2. Nodes A, B, and C have established a network (1a) and node A made a minislot reservation for transmitting data to node B. To this end, node A sent a request, the request was granted by B and confirmed by A. Node C overheard the grant message from node B but did not overhear the grant confirmation message from A (1b). Thus the slots in C are in the state receive available. Now a fourth node (node N) being neighbor to all other nodes joins the network (1c) and all slots of node N are still available. If N requests slots from C, C may include in its grant the same minislot range as A, which leads to a collision at B.

A novel solution to the problem mentioned above is presented in the following. The solution is presented in the scope of IEEE 802.16 but is generic in nature and can be applied or adapted to other standards as well. An efficient method for synchronizing the status of upcoming timeslots or transmission opportunities between a mobile node and the surrounding network can be based on an extension of the existing MSH-DSCH (Mesh Distributed Scheduling) message within the 802.16 standard. A node may ask other nodes for retransmission of all grants and grant confirmations that have not yet timed out. In doing so as soon as a new neighbor is detected, the nodes can keep their availability states consistent. Lost grants and grant confirmations can be covered by periodic retransmission requests ("Availability Synchronization").

To this end two new IEs (Information Elements), namely MSH-DSCH-Synchronization-IE (Figure 3) and MSH-DSCH-Defragmented-Grant-IE (Figure 4), can be included in the existent MSH-DSCH message. The MSH-DSCH-Synchronization-IE is used by nodes either to re-send their grant/grant confirmation messages or to query a node to send the very same. A flag in the message is used to distinguish between queries and responses. In the case of a query, a list of Node-IDs (Identifications) is included in the message. Nodes receiving the query chec...