1. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 1 Dual CTS for Extended Range Normal Range considerations Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Date: 2006-05-16 Authors:

2. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 2 11n will bring range extension What is the largest range difference between ER and NR devices? –It occurs when having heterogeneous STA with different antenna configurations e.g. between 1RX to 4TX, According to table: more than 8dB difference is observed i.e. 69% more range 187% additional surface –Origin: minor factor CDD/STBC when multiple TX gain but mostly MRC when multiple RX STBC 1 stream BPSK R=1/2 channel D results with 11n 2 slopes path loss models, 5% PER target 1000B packets –Is the SIG field a limitation? No because it is MRC with multiple RX that grants most of the range Goal: fight against hidden terminal effect (yet do not resolve it)

3. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 3 Additional range gain for STBC over CDD On top of range natively provided by CDD (see previous slide), an additional range extension is provided by STBC (5% PER target): 2TX 22% (1.5dB), 3TX 28% (1.8dB), 4TX 46% (2.9dB)

4. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 4 What has changed compared to WWiSE Two ways of enabling ER/NR cohabiting –Secondary beacon Tx –Dual CTS protection –Additional HT info elements sent into beacon: 3 added fields (two 1 bit wide and one 6 bits wide) Dual CTS protection (on/off) Secondary beacon (primary/secondary) Basic STBC MCS (6bits) indicates what MCS shall be used for STBC control frames and Beacon Simplifications –Secondary beacon Tx (TBTT scheduled half beacon period) followed by BC/MC Tx –What is covered: dual CTS protection targeting In UL: 11n devices (no specific rule for UL legacy) In DL: all devices Reason for this simplification: limit the implementation complexity –Rules apply for all devices (no need to distinguish for specific class of device, such as ER- capable STA in NR or ER mode, NR STA, leg STA) –Reduced overhead (suppress unpredictable awkward double backoff issue with former leg STA protection in UL) Motivation: legacy STA often do not make use of RTS/CTS anyway. Capturing the UL leg STA case was adding unnecessary complexity on the AP side, for no added protection –Better consistency: now same modulation type (STBC or no STBC) is used for a CTS in reply an RTS –Generic: in DL, the simple rule proposed also protects other modes of operation than those under EDCA (e.g. polling, SAPSD)

5. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 5 ER/NR coexistence MAC protection mechanisms The dual CTS response only applies to the AP, STA always respond with a single CTS In UL –STA shall start a TXOP with an RTS directed at the AP –AP shall respond with a dual CTS Non-STBC RTS: –CTS1: Same rate or MCS as the RTS (non-STBC) –CTS2: Lowest basic STBC MCS (STBC) sent only if medium is idle –PIFS separation to account for legacy devices continuing after SIFS STBC RTS –CTS1: Lowest basic STBC MCS (STBC) –CTS2: Lowest basic rate (non-STBC) –SIFS separation In DL –AP should protect STBC TXOPs with a non-STBC CTS non-STBC TXOPs with an STBC CTS –AP should continue PIFS after the CTS, to allow for a collision detect.

6. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 6 Overhead evaluation Assumptions –10 users, EDCA.11 MAC Tx (or dual CTS Tx) + RTS/CTS, CWmin=15,.11n PHY overhead considered, PER=0, same MCS used Conclusion –No major loss induced by dual CTS Tx

7. doc.: IEEE 802.11-06/0732r1 Submission 05 2006 Marc de Courville (Motorola)Slide 7 Considerations for preserving dual-CTS Remarks: –Make STBC mandatory would remove need to have dual-CTS and simplify standard Improvement: –L-SIG TXOP Protection mechanism can be extended to be mandated for STBC use by extending the normative text Observations: –Mixed mode: range is determined by LSIG perf –Green field: range is determined by HTSIG perf Why preserving dual-CTS –Improve perf balance between preamble and data –Do not throw away 0.9dB! (increae of 6% in range, 13% in surface) –It doesn’t show a large penalty in throughput –It is optional –STBC importance for HH inherently limited in range (#antennas) HTSIG NR -DATA NR HTSIG NR -DATA ER 2.5dB When to dupplicate? Δ?Δ? Observations (con’t): –HTSIG is based on rBPSK and not pQPSK and has same robustness as data –For a target PER (i.e. 5%) short packets (SIG/HTSIG/CTS/RTS) have better C/I requirements than larger packets (i.e. at a given SNR PER increases with packet size)