2. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 1 Single Burst Contention Resolution “Wireless Collision Detection” (“CSMA/CS”)

3. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 2 Overview Proposed new technology family for collision detection Uses OFDM modulation techniques Potentially provides better then 50% improvement in network efficiency Potential use in 802.11a and 802.11g

4. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 3 CSMA/CA Positive Acknowledgement Collision time equals length of longest colliding data frame

5. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 4 CSMA/CS Positive Acknowledgement Optional in certain circumstances Fixed short collision time

6. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 5 Performance IEEE 802.11 Wireless LAN: Capcity Analysis and Protocol Enhancement Packet transmit time = average length of packet + acknowledgement + (IFSs + backoffs) Data transmit time = Packet transmit time + (Collision time x average collision percent)

7. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 6 CSMA/CA vs CSMA/CS performance graph

8. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 7 CSMA/CA vs CSMA/CS performance graph

9. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 8 Current Solution: RTS/CTS Performs contention resolution function Used in larger sized packet transfers Significant overhead due to total packet length of RTS and CTS

10. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 9 What is needed? Low network overhead contention resolution Minimal implementation complexity Minimal per node processing overhead Fast collision detection at contending nodes

11. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 10 Contention Symbol (“CSMA/CS”) Channel Arbiter (“CA”) and nodes Contention Symbol: single short OFDM burst CA - fast collision detection algorithm CA – single short OFDM burst response OFDM burst length principally determined by propagation delay

12. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 11 CSMA/CS How it works.

13. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 12 Binary amplitude OFDM tones implies: –Ignores all phase information –No synchronization information needed –Only requires overlap of orthogonal section of all received OFDM bursts

14. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 13 Binary tone patterns Set of linear independent basis vectors, example: –1010, 0101, 0110, 1001, 0011, 1100 Binary OR of two or more vectors from set, result not in set Property: any vector with greater then ½ binary 1’s means OR of 2 or more vectors occured

15. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 14 Multiple sets of vectors 13 vectors of 4 bits each Each vector random choice from set of 6 basis vectors Resulting concatenated 52 bit vector Very low probability of all 13 vectors identical from any two nodes. (Binomial probability distribution)

16. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 15 Frequency Mapping 52 bit binary vector mapped as binary on/off tones in 802.11 OFDM frequency map magnitudes Discrete randomized phase rotations on a per tone basis. –Reduces opportunity for destructive phase interference between two signals

17. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 16 OFDM burst transmission Perform IFFT Perform digital and analog modulation and transmission

18. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 17 Burst reception at CA Performs threshold power detection at defined sensitivity level Waits for predefined propagation interval and guard interval Captures OFDM burst Performs analog and digital demodulation to baseband

19. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 18 Burst reception at CA Performs FFT on OFDM burst Takes magnitude of complex frequency map elements Creates binary vector using threshold value Compares 13 sub vectors with set of basis vectors, using binary 1’s count Collision detected in any single sub vector

20. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 19 CA response CA generates similar binary amplitude OFDM burst, consisting of: Pattern A – collision detected Pattern B – no collision detected

21. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 20 Node receiving CA burst Performs FFT on baseband signal Thresholds magnitudes to create binary vector Compares vector with known CA symbols On no collision detected, waits for propagation delays, and transmits normal data frame

22. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 21 Approximate Timing for 802.l1a 4 uS frame + cyclic extension for propagation delays (< 1 uS per 100 meters) + cyclic extension for carrier sense delays at nodes (2 < uS ?) Fixed wait between node burst and CA burst = (carrier sense delay) 4 uS CA frame + propagation delay + carrier sense delay (carried forward)

23. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 22 Approximate Timing for 802.11a 16 uS for no collision detection 14 uS for collision detected Node transmits data frame after processing delays

24. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 23 Comparison with RTS/CTS RTS approximately 24 uS (54 MB) or greater CTS approximately 24 uS (54 MB) or greater 2 IFS = 32 uS Total >= 80 uS for no collision detected Total >= 49 uS for collision detected CSMA/CS > 5 times faster data transmit turnaround CSMA/CS > 3 times faster collision detection

25. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 24 Comments Constant fixed overhead suitable for all contention based traffic Solves near/far power “capture” problem Allows multiple infrastructure access points Back compatible with 802.11 protocol

26. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 25 Solutions For Quality of Service “Semi-soft” cell switching Transmit power modulation “Micro cells” Inbuilding geolocation Frequency offset error correction Short duration burst noise

27. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 26 Solutions For Contention free operation periods Collision detection in Ad hoc network operation

28. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 27 Intellectual Property Statement Corporate Wave Net, Inc. has multiple patents pending regarding the information presented. CWN is willing to consider licensing of certain pending patents in its portfolio which are directed to and necessary for the implementation and practice of the technology presented for the purposes of IEEE standardization, on fair, reasonable and non-discriminatory terms and conditions to qualified applicants in accordance with IEEE patent policy

29. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 28 Corporate Wave Net, Inc. David Beberman 104 Otis St. Ste. 29 Northboro, MA. 01532 P: (508) 351 – 9492 CWN1@world.std.com

30. doc.: IEEE 802.11-02/183r0 Submission March 2002 David Beberman, Corporate Wave Net, Inc.Slide 29 Carrier Sense Multiple Access with Contention Symbol CSMA/CS