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Scheduling Scheme for PCF with Diversity

Scheduling Scheme for PCF with Diversity. Marc Realp and Ana Pérez-Neira Telecommunications Technological Center of Catalonia-CTTC (marc.realp@cttc.es). Contents. Motivation MPR Capability Model Scheduling Procedure Simulations Further Work. Motivation(1).

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Scheduling Scheme for PCF with Diversity

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  1. Scheduling Scheme for PCF with Diversity Marc Realp and Ana Pérez-Neira Telecommunications Technological Center of Catalonia-CTTC (marc.realp@cttc.es) Marc Realp-CTTC

  2. Contents • Motivation • MPR Capability Model • Scheduling Procedure • Simulations • Further Work Marc Realp-CTTC

  3. Motivation(1) • In PCF of the IEEE 802.11, the PC allows transmission of only one STA at a time in order to avoid collisions. • Diversity at physical level allows more than one packet to be transmitted simultaneously. Hence, giving Multi-Packet Reception (MPR) capabilities. • The802.11-99do not consider MPR capability. NG MAC protocols must fully exploit PHY MPR capabilities. Marc Realp-CTTC

  4. Motivation(2) • Example Scenarios: How many STAs should the PC poll simultaneously? Access Set (AS) Marc Realp-CTTC

  5. MPR Capability(1) • The packet success probability will mainly depend on the number of additional packets present at the receivern-1 (or Multiple Access Interference): • Hence, the MPR capability, Marc Realp-CTTC

  6. MPR Capability(2) • Capacity: Maximum expected successfully received packets • Therefore: • Without diversity (no MPR): Only one packet at a time to achieve maximum capacity. Hence, nmax=1 • With diversity (with MPR): More than one packet at a time. Hence, nmax>1. Marc Realp-CTTC

  7. Scheduling Procedure • The AS is directly nmax • If we have a probability q to receive a CF-Poll correctly: • Computation of AS (>nmax) size is based on Modified Dynamic Queue Protocol (MDQP) protocol. • The optimal AS size that minimizes duration of CFP (or maximizes throughput) is computed off- line as a function of the MPR and the estimated probability (q). • CCA.indicate primitive is used as information from PHY layer to determine STAs that did not receive the CF-Poll. (main difference with Dynamic Queue Protocol (DQP)) • The PC is capable to distinguish between: • Empty slots. • Successfully received packets in non-empty slots. • Packets lost due to collision in non-empty slots. • STAs that did not receive the CF-Poll in non-empty slots. (Not possible with the DQP) Marc Realp-CTTC

  8. Scheduling Procedure for PCF SIFS 5(NULL) SIFS 3 SIFS SIFS SIFS PIFS 2 4 CF-End Beacon Poll 1,2,3 1(NULL) 2 Poll 2,4,5 1 2 The PC determines that packet from STA 2 is lost. Access Set Size is 3 2 4 3 5 4 5 Successfully received packet Packet waiting for transmission Empty buffer Packet Lost Marc Realp-CTTC

  9. Scheduling Procedure for PCFwithq SIFS SIFS SIFS SIFS SIFS PIFS 3 4 CF-End Beacon Poll 1,2,3 2 Poll 2,4,5 2 1 2 The PC determines that STA 1 has not received a CF-Poll and packet from STA 2 is lost. The PC determines that STA 5 has not received a CF-Poll. 4 2 Access Set Size is 3 5 3 4 5 Successfully received packet Packet waiting for transmission CF-Poll lost Packet Lost Marc Realp-CTTC

  10. Access Set Vs User Packet Probability MDQP DQP Number of Users (M)=15 SNR=10dB Spreading Gain (SG)=6 Access Set Packet Length (pl)=200bits Receiver type: Matched Filter CF-Poll Success Probability (q) Marc Realp-CTTC

  11. Throughput Vs User Packet Probability M=10 M=15 SNR=10 Spreading Gain (SG)=6 Packet Length (pl)=200bits Receiver type: Matched Filter Throughput M=5 Ideal case for w/o diversity PCF MDQP DQP w/o Diversity PCF CF-Poll Success Probability (q) Marc Realp-CTTC

  12. Further work • Introduction of diversity at PHY • Estimate probability of CF-Poll lose(q) • Must consider PC packets (Downlink) in the scheduling. Marc Realp-CTTC

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