1. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 1 Proposal to Add Link Margin Field in IEEE 802.11h A. Soomro and S. Choi PHILIPS Research, USA

2. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 2 Introduction Review of current Path Loss Estimation mechanism in IEEE 802.11h draft Benefits of TX Power and/or Rate Adaptation Proposed changes Conclusions

3. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 3 Path Loss Estimation RATE 4 bits Reserved 1 bit LENGTH 12 bits Parity 1 bit Tail 6 bits SERVICE 16 bits PSDU Tail 6 bits Pad Bits PLCP Header SIGNAL One OFDM Symbol DATA Variable Number of OFDM Symbols PLCP Preamble 12 Symbols Coded OFDM BPSK, r = 1/2 Coded OFDM RATE is indicated in SIGNAL PPDU frame format

4. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 4 TX Power contains the power used to transmit the PPDU –Relative to the max TX Power Level Path Loss Estimation SERVICE field frame format Bit Value

5. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 5 Path Loss Estimation TX Power field encoding

6. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 6 Path Loss Estimation Process TX STA encodes the TX power level of PPDU in SERVICE field RX STA measures the RX power level of PPDU Path Loss = Encoded TX Level - RX Power Level Assuming reverse symmetry, path loss in reverse direction is estimated

7. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 7 Benefits Contention Period (CP) –Better adaptation of TX rate Contention Free Period –Better TX Power and/or TX Rate control Results in –Increased throughput –Lower interference –Longer battery life –More reliable communication

8. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 8 However… Could be improved further, due to –Implementation-dependent receiver performance –Local noise/interference levels –Channel characteristics

9. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 9 The Link Margin The difference in signal level in dB, from the level of the immediately prior frame received from the STA (that is the current PPDU’s destination STA) that could be tolerated by this STA without affecting its correct reception at that rate.

10. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 10 Proposed Changes Use bits 12-15 to convey Link Margin Bit Value Range: +9 dB to -5 dB

11. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 11 Proposed Changes Margin encoding

12. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 12 Proposed Changes Transmission of Link Margin by a STA is optional Usage of this information by a receiving STA is optional –A STA could choose to ignore this information –Or, it could utilize this information to intelligently control TX power and/or TX rate for future transmissions

13. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 13 An Example APSTA 1 STA 1 sends one MPDU to AP with TX Power field set AP sends ACK with TX power and Link Margin fields set STA 1 adjusts TX Power and/or TX rate STA 1 sends next MPDU to AP with adjusted power and/or rate The current channel/receiver information could be an input factor to select TX power/rate for subsequent transmissions to the AP AP sends ACK with TX power and Link Margin fields set

14. doc.: IEEE 802.11-01/536r0 Submission September 2001 A. Soomro and S. Choi, Philips Research, USASlide 14 Conclusions Enhances network performance –Increased network throughput –More reliable communications –Lower interference –Longer battery life Backward compatible Little additional complexity Optional Features