1. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 1 Discussions on the access control mechanisms for WLAN NG Yasuhiko Inoue, Satoru Hori, Tetsu Sakata and Masahiro Morikura NTT Access Network Service Systems Laboratories mailto:yinoue@ansl.ntt.co.jp

2. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 2 HDR more than 100M bit/s Our initial analysis shows that it is difficult to achieve data rate of 100M bit/s with 20MHz (02/159r1) –Combination with new techniques MIMO, Link aggregation –Increase the bandwidth for a channel High efficiency is required for MAC protocol –Access control mechanism TDMA based CSMA based Additional functions topic of this presentation

3. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 3 AP Scenario Single-cell environment –Example: SOHO, etc –no need to consider interference Multi-cell environment –Example: hotspot, flat, etc. –may experience sever interference AP ISP C o f f e e AP Interference same channel

4. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 4 Multi-cell environment Channel selection: may not be always done ideally Problem: co-channel interference degrades throughput To avoid interference: –Channel separation: Prepare enough number of channels to satisfy C/I requirement. –Channel sharing: Share the same frequency channel with other areas AP

5. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 5 Channel separation Channel separation: –Basically the same idea as cellular systems. –Prepare enough number of channels to satisfy C/I requirement when the channel is reused. –Problem: Do we have enough bandwidth? f2 f3 f1 f7 f6 f5 f4 f1f2f3f4f5f6f7 Freq. f2 f3 f1 f7 f6 f5 f4 f2 f3 f1 f7 f6 f5 f4 f2 f3 f1 f7 f6 f5 f4 f2 f3 f1 f7 f6 f5 f4 Example of 7 channels

6. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 6 Channel sharing Channel sharing: –Basically the same idea as current 802.11. Share the same channel with other area autonomously. Problem: Hidden terminal problem. –Other mechanism something like CDMA also be considered.

7. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 7 TDMA Based Access Protocol Channel separation: –C/I requirements: have an effect on the radius of a service area (BSA) determines necessary number of the channels for stable operation Channel sharing: –mechanism for channel sharing will be required. –Problem: Autonomous synchronization of the time frame between APs Autonomous scheduling for transmission between APs, etc. TDMA based protocol will work well if enough number of channels are available

8. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 8 CSMA Based Access Mechanism Channel separation: –The effect of hidden terminal problem will greatly decreased. Channel sharing: –CSMA based protocol basically provides this mechanism –Problem: Hidden terminals causes throughput degradation RTS/CTS procedure may not enough to prevent inter-cell interference CSMA based protocol can be adopted for both scenarios

9. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 9 Coexistence with legacy systems in UNII band TDMA based protocol –Additional mechanism will be required for coexistence. –High efficiency of the new protocol may not be seen as far as coexisting with the legacy system. CSMA based protocol –Good solution considering coexistence. –Backward compatibility will be achieved. –CDMA may be used with this mechanism. time TDMA CSMA TDMA CSMA TDMA

10. doc.: IEEE 802.11-02/446r0 Submission July 2002 Y.Inoue, NTTSlide 10 Summary TDMA based access control: –High efficiency –Needs a number of channels to satisfy C/I requirement. CSMA based access control: –Good channel sharing mechanism if hidden terminal problem is avoided. –flexible configuration –lower efficiency than TDMA based mechanism, but it can be improved by additional mechanism. CSMA based protocol will be a better solution for WLAN NG