Cooperative Opportunistic Routing using Transmit Diversity in Wireless Mesh Networks

1. Cooperative Opportunistic Routing using Transmit Diversity in Wireless Mesh Networks Jongryool Kim Networked Media Laboratory School of Information & Mechatronics Gwangju Institute of Science & Technology http://netmedia.gist.ac.kr

2. Introduction • Cooperation • A generation of the relay data to multiple nodes with information to transmit that also serve as relays for each other • Neighboring nodes cooperate and assist in transmitting and receiving frames. • Transmit diversity : multiple transmit elements (MISO) • Opportunistic Routing • Some wireless network link’s error rate may be rather high for other links • This bring up the opportunity that a packet might skip a few nodes on its forwarding path if current radio propagation conditions are favorable

3. ExOR (Extremely Opportunistic Routing) @sigcomm 05 src A B C D E dst src src A A B Traditional Routing B ExOR C C D D E E dst dst • Traditional routing suffers high overhead because of much retransmission • ExOR can take advantages of broadcast reach unexpectedly short or far

4. Limitation of ExOR • Limitation of ExOR • The State-of-the-art opp. routing, ExOR imposes a global scheduler: • Selection Requires full coordination; every node must know who received what (too hard implementation) • Only one node transmits at a time, others listen (lost spatial reuse) packet packet packet packet A B src dst packet packet packet packet packet C

5. MORE (MAC-independent Opportunistic Routing) @ sigcomm 07 • MORE • Source sends packets in batches • Forwarders keep all heard packets in a buffer • Nodes transmit linear combinations of buffered packets • Destination decodes once it receives enough combinations • Destination acks batch, and source moves to next batch P1 R1 αP1+ß P2 P2 src dst Batch P1 R2 γP1+δP2 P2 Batch

6. TDiCOR (Transmit Diversity based on Cooperative Opportunistic Routing) @ Infocom 08 • Multiuser and transmit diversity -> overall throughput in WMN. • Cooperative Acknowledgements • MAC header contains the candidate set instead on a single receiver. • Only nodes enlisted in the header reply with ack after SIFS. • However, for reducing congestion at the downstream nodes(due to multiple ack) it uses the candidate equivalent backoff (scaled by the number of candidates) • It only requires at least one candidate successfully receives the packet. • Passive Forward Selection • Dynamic assignment of the forwarding responsibility to one node (one node at every point)

7. TDiCOR (Transmit Diversity based on Cooperative Opportunistic Routing) @ Infocom 08 • Cooperative Data Transmission using transmit diversity • It reduces the waste of network resource at the Passive Forward Selection • However, C2 done not have to receive same data frame D from S1 • Cancelation of non-innovative Transmissions • S1 miss ACK from receivers • It uses two consecutive ACK frame

8. Results

9. Conclusion • Conclusion • This paper proposes a cooperative forwarding protocol based on opportunistic routing and transmit diversity. • TDiCOR outperforms traditional routing (DSR) in terms of throughput by 30%(indoor) and by 50%(outdoor) with less complexity • Disscusion • This is only simulation • Without power control and congestion control.