1. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 1 Simplifying Polling Mathilde Benveniste benveniste@ieee.org Dongyan Chen Avaya Labs Research

2. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 2 Background Avaya is interested in QoS (e.g. VoIP) and channel throughput in the enterprise space Minimal delay for time-sensitive applications and efficient channel use are the focus -- regardless of data rate

3. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 3 Motivation RRs serve QoS while promoting efficient channel use –RRs keep polling list short – limited to active stations –RRs permit the polling mechanism to work for burstry traffic as well as periodic traffic Simple implementation is attractive in an RR mechanism

4. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 4 Terminology CC/RR the reservation mechanism for polling, as it appears in D3.0 EDCF/RR alternative reservation mechanism for polling –no CCI; RRs comprise top priority EDCF class –the RR could be the QoS-Null frame

5. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 5 Simulations in 01/571r0 In 01/571r0 the results showed a better performance of CC/RR compared to ‘straight’ PCF –Straight PCF polls all associated stations These results were not sufficient to validate the CC/RR mechanism –The results simply showed that a managed polling list improves performance

6. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 6 Simulations in 02/305r0 02/305r0 results showed better performance with CC/RR compared to EDCF/RR while using a short CP –CFP uses up to 18 ms in a 20 ms cycle –Only 2 ms provided for CP; a fairer allocation of channel time would have averted the high collision rate affecting the RRs 02/305r0 results showed long access delays with EDCF/RR caused by DCF contention despite use of PF differentiation –A Persistence Factor was included, but not set at lowest value; a better choice of EDCF parameters would have protected the RRs The results in 02/305r0 do not establish the superior performance of CC/RR over EDCF/RR –CC/RR is compared to a sub-optimal EDCF/RR specification

7. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 7 Our objective To present an efficient specification of EDCF/RR To show simulation results comparing EDCF/RR to CC/RR

8. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 8 Simulation Scenarios Uplink and downlink transmission through HCF in CP The performance of the two reservation mechanisms –CC/RR: CCI period=5 ms; CCOPS=50 –EDCF/RR: PF=0.5 [01/409r2]; AIFS=PIFS; CWmin=8; Cwmax=2 is compared under two scenarios Under low load (LL) The load consists of time-sensitive bursty traffic (Load1, p 8) With heavy DCF load (HL) A best effort load of 5 stations, 1 Mpbs per station, is added (Load2, p 8) The same HCF implementation used on the downlink for both scenarios

9. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 9 Traffic Scenarios Two loads considered on 11Mbps DS channel Load1 is transmitted by polling; it generates frequent RRs –8 stations engaged in two-way exchange with AP of time-sensitive bursty traffic –Payload [excludes MAC & PHY overhead] per packet =120 bytes; inter-arrival fixed at 10 ms when ON; exponential 342 ms ON /650 ms OFF (example: silence suppressed voice) Load2 contends for the channel through DCF –5 stations sending low priority data uplink –Payload per packet=724 bytes; inter-arrival exponential at 7 ms

10. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 10 Statistics Reported RR ETE (end-to-end) delay Load1 uplink ETE delay – –Simple poll scheduling –Optimized poll scheduling Load1 downlink ETE delay Load2 load ETE delay

11. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 11 RR end-to-end delay (sec) CC/RR-LL under Light Load EDCF/RR-LL CC/RR-HL under Heavy Load EDCF/RR-HL EDCF/RR gets the RRs out sooner

12. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 12 Load1 uplink end-to-end delay (sec) CC/RR-LL under Light Load EDCF/RR-LL CC/RR-HL under Heavy Load EDCF/RR-HL Without optimization EDCF/RR leads to lower uplink delay

13. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 13 Load1 uplink end-to-end delay (sec) CC/RR-LL under Light Load EDCF/RR-LL CC/RR-HL under Heavy Load EDCF/RR-HL With optimization Even with optimization EDCF/RR does at least as well

14. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 14 Load1 downlink end-to-end delay (sec) CC/RR-LL under Light Load EDCF/RR-LL CC/RR-HL under Heavy Load EDCF/RR-HL Downlink performance is the same for the two mechanisms

15. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 15 Load2 end-to-end delay (sec) CC/RR-HL EDCF/RR-HL under Heavy Load CC/RR dedicates channel time (20% in this example) to CCI that could be otherwise used for transmission EDCF/RR uses channel more efficiently

16. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 16 Conclusions EDCF/RR gets the RRs out sooner EDCF/RR uses channel more efficiently EDCF/RR performs at least as well as CC/RR under all situations –Light load –Heavy load –Optimized and non-optimized poll scheduling EDCF/RR is simpler to implement

17. doc.:IEEE 802.11-02/525Ar0 Submission September 2002 Mathilde Benveniste, Avaya Labs Slide 17 Motion Remove CCI from D3.0 Devote top priority EDCF class to RRs exclusively Re-introduce the persistence factors and use lowest PF value for RRs only