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A Design Framework for High-Density Wireless Ad-Hoc Networks Achieving Cooperative Diversity

A Design Framework for High-Density Wireless Ad-Hoc Networks Achieving Cooperative Diversity. Hamid Gharavi, Bin Hu and Nan Wu IEEE ICC 2010 Speak: Huei -Rung, Tsai. Outline. Introduction Goals System Structure Network Layer Design (CDSR protocol) MAC Layer Design PHY Layer Design

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A Design Framework for High-Density Wireless Ad-Hoc Networks Achieving Cooperative Diversity

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  1. A Design Framework for High-Density Wireless Ad-Hoc Networks Achieving Cooperative Diversity Hamid Gharavi, Bin Hu and Nan Wu IEEE ICC 2010 Speak: Huei-Rung, Tsai

  2. Outline • Introduction • Goals • System Structure • Network Layer Design (CDSR protocol) • MAC Layer Design • PHY Layer Design • Simulation Results • Conclusions

  3. Introduction • In Multiple Input Multiple Output (MIMO) systems • meet the growing need for high-throughput • reliable transmissions • It may not be accommodated multiple antennas at the nodes • Virtual MIMO mimicking the behavior of the co-located MIMO • Cooperation benefit • increasing the data transmission reliability • providing higher throughput • extending network coverage • reducing the transmission delay • saving the transmit power

  4. Introduction • However, there are a number of challenges for VMIMO system • relay selection • nodes’synchronization • the use of a VMIMO structure • The existing cooperation schemes • additional control signals to select and maintain relays • reduces the effective throughput • TDMA-based synchronization • costly in ad hoc network (lack of base station, nodes mobility, large number of nodes)

  5. Introduction • Previous designs have two main issues • relay selection process is implemented in the MAC layer • control packets to provide handshakes between source, destination and relay • the relays are prohibited from transmitting simultaneously

  6. Goals • Present a systematic design structure for high-density ad hoc networks aimed at achieving full cooperative diversity, based on which the Network, MAC and PHY layers • Improved packet delivery reliability • Reduced transmission delay • Resistance to network topology variation • Synchronous transmissions in ad hoc networks • Simplicity of the proposed protocol

  7. System Structure VMIMO Source Destination • existing cooperative schemes, which merely use relays to ’enhance’ an existing link • cooperative routes are selected ’jointly’ in order to assist each other in every hop

  8. Network Layer Design • Cooperative Dynamic Source Routing (CDSR) protocol 2 3 4 5 6 1 8 9 7 10 11 12 Source Destination 14 15 13 16 17 18 20 21 24 19 22 23 25 26 27 29 30 28

  9. Network Layer Design • Cooperative Dynamic Source Routing (CDSR) protocol 2 3 4 5 6 1 8 9 7 10 11 12 Source Destination 14 15 13 16 17 18 20 21 24 19 22 23 25 26 27 29 30 28

  10. Network Layer Design λ(Node14)=7 λ(Node15)=6 λ(Node16)=6 λ(Node17)=7 λtotal=26 • Limit set to 11 35 33 32

  11. Network Layer Design • Route Maintenance of CDSR • Original DSR 8 9 7 10 11 12 re-establish the link by RTS/CTS RERR Source Destination 14 15 13 16 17 18 ACK=0 High transmission delay

  12. Network Layer Design • Route Maintenance of CDSR • CDSR (RERR packet initiate when both link fail ) RTS 8 9 7 10 11 12 NTS Source Destination 14 15 13 16 17 18 ACK=1

  13. MAC Layer Design • Every stage of the transmissions should form a (2×2) VMIMO structure having two transmitters and two receivers Transmitter-1 Receiver-1 Transmitter-2 Receiver-2 Contention DIFS SIFS SIFS SIFS Transmitter-1 ST-DATA ST-DATA RTS Transmitter-2 ST-CTS ST-ACK Receiver-1 ST-CTS ST-ACK Receiver-2 NAV(RTS) NAV(CTS) Other Nodes Other Nodes Time

  14. MAC Layer Design

  15. PHY Layer Design • The challenges addressed in the PHY layer are two fold • Space-Time Block Coding (STBC) schemes • even if these nodes are scheduled to transmit simultaneously, the propagation delays by the signals from cooperative nodes are different • asynchronous cooperative MIMO system using a linear dispersion

  16. Simulation Results • Using personal real-time network simulation testbed, where the invoked IEEE 802.11b standard • Input data generated at a Constant Bit Rate • Fixed 500 bytes UDP packets • data-rate is 2 Mbps • noise factor is 10.0. Rayleigh fading • transmit power • intermediate nodes is set as half of the original DSR • source and destination node’s is set as the same as original DSR • 40 nodes are placed randomly in a 1500 m × 1500 m area

  17. Simulation Results • Retransmissions counter = 4

  18. Simulation Results

  19. Conclusions • This paper proposed a cooperative diversity scheme for ad hoc networks. The core feature is that cooperative routes can assist the transmission of each other • hence the reliability of all wireless links • reduce the link breakage probability

  20. Thanks For Your Attention~

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