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Multi-User Diversity in Single-Radio OFDMA Ad Hoc Networks Based on Gibbs Sampling

Multi-User Diversity in Single-Radio OFDMA Ad Hoc Networks Based on Gibbs Sampling. Marzieh Veyseh J.J. Garcia-Luna-Aceves Hamid R. Sadjadpour. Motivation. Channel 1. Channel 1. Concurrency Frequency Code Space. Channel 3. fc3. fc4. fc5. fc1. fc2. Code 1. Channel 1. Code 3.

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Multi-User Diversity in Single-Radio OFDMA Ad Hoc Networks Based on Gibbs Sampling

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  1. Multi-User Diversity in Single-Radio OFDMA Ad Hoc Networks Based on Gibbs Sampling Marzieh Veyseh J.J. Garcia-Luna-Aceves Hamid R. Sadjadpour

  2. Motivation Channel 1 Channel 1 Concurrency • Frequency • Code • Space Channel 3 fc3 fc4 fc5 fc1 fc2 Code 1 Channel 1 Code 3 Code 2 Code 3 Code 1 fc fc fc fc

  3. Motivation t1 Adaptivity • Time • Frequency, through different modulations… Diversity To use fading in our advantage and to improve rate… • MIMO • OFDAM-Multiuser diversity t2 t3 t5 t1 t3 t4

  4. OFDMA Subchannel i Subchannel 3 Subchannel 1 Subchannel 2 Subchannel 4 fc • Proposed for infrastructure-based OFDMA networks • We think that utilizing OFDMA in ad hoc networks gives us the ability to achieve our goals: • Concurrency: multiple nodes use different portions of BW • Diversity: multi-user diversity • Adaptivity: subchannels can have different sizes

  5. OFDMA Synchronization C-Tx C-Tx • In an ad hoc multi-transmitter scenario to avoid loss of orthogonality at a common neighbor to multiple transmitters, a quasi-synchronousnetwork is required. • Quasi-synchronous : transmitter start sending data at the same time • Multi-transmission synchronization achieved via control message exchanges

  6. Previous work • Not much work on protocols for OFDMA for ad hoc networks • CTRMA: In our previous work, we assigned non-overlapping channels unique within the two hop neighborhood based on some priority order. [OFDMA Based Multiparty Medium Access Control in Wireless Ad Hoc Networks, ICC, 09]) • CBD: We added diversity when distributing the assigned subchannels among neighbors[Cross-Layer Channel Allocation Protocol for OFDMA Ad Hoc Networks, Globecom 10]

  7. GSA Gibbs Sampling a C-Tx_1 C-Rx Goal: • Maximize concurrency • Design a MAC that assigns subchannels to each directional link on-demand and based on the present interference, and node’s needs • Maximize diversity • Subchannel selection should be done based on minimizing fading • Gibbs sampling previously used to distribute channels among multiple 802.11 Aps : min direct interference C-Tx_2 C-Rx b

  8. Gibbs Sampling • Graph , and state X…want to find

  9. GSA Gibbs Subchannel Assignment (GSA) • We propose to use Gibbsian method by defining a new energy model and a MAC protocol that works to select subchannels (Schannel) for each communicating link. b u v C-Tx (c) C-Tx (a) C-Rx Subchannel k

  10. MDMA a c Freq C-Tx b d RTM-T Control FreeTx Schannel_1 FreeTx Schannel_2 time

  11. MDMA MDMA a c Freq C-Tx b d RTM-T Control FreeTx Schannel_1 Pilot FreeTx Schannel_2 Pilot time

  12. MDMA a c Freq C-Tx SINR(k)>Thr a b c d v b d e RTM-T Control CTR FreeTx Schannel_1 Pilot FreeTx Schannel_2 Pilot time

  13. MDMA a c Freq C-Tx a b c d b d RTM-T Control CTR FreeTx Schannel_1 Pilot Data: C-Tx->a Broadcast FreeTx Schannel_2 Pilot Data: C-Tx->b Broadcast time

  14. MDMA c a Freq C-Rx b d RTM-R Control FreeRx Schannel_1 FreeRx Schannel_2 time

  15. MDMA c a Freq C-Rx b d RTM-R Control a b c d FreeRx Schannel_1 CTT a b c d FreeRx Schannel_2 CTT time

  16. MDMA c a Freq C-Rx b d STT RTM-R Control a b c d FreeRx Schannel_1 CTT a b c d FreeRx Schannel_2 CTT time

  17. MDMA c a Freq C-Rx b d STT RTM-R Control a b c d FreeRx Schannel_1 Data: a->C-Rx CTT a b c d FreeRx Schannel_2 CTT Data: b->C-Rx time

  18. Analysis Range = a v v u Average =4

  19. Analysis 1.3 v v a u

  20. Analysis Result Analytically GSA is outperforming ideal scheduling 2.6 times

  21. Matlab Simulations Simulations a C-Tx b u c

  22. Matlab Simulations Simulations A B A B C B A

  23. Matlab Simulations MDMA • GSA increases concurrency comparing to CBD 2.3 times 63%

  24. Qualnet Simulations MDMA 1.6 times

  25. Conclusion Conclusion • Previous cross-layer MAC fail to effectively utilize OFDMA • We improved our previous works by • Utilizing Gibbs method • Increasing two-hop neighbor concurrency • Attaining diversity • Our analysis and simulations proved that MDMA’s performance with the same BW is • 1.6 times better than CBD • 2.2 times better than CTRMA • 2.4 times better than traditional multi-channel networks • Future work • Mobility • 802.11n OFDMA

  26. Questions

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