1. 1Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 1 OFDMA Single Channel Harmonization IEEE P802.22 Wireless RANs Date: 2007.8.02 Authors: Notice: This document has been prepared to assist IEEE 802.22. 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 802.22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf 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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl R. Stevenson 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 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org. patcom@iee.org >

2. 2Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 2 Adequacy of CAZAC PN sequences Attributes of PN sequences needed to support WRAN deployment with Reuse factor 1/3 Partial simulations results on O-PUSC

3. 3Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 3 Adequacy of proposed CAZAC scheme the PAPR of preamble is an important property. However, the preamble PAPR should be examined in view of the payload PAPR. That is, decreasing the Preamble PAPR beneath the expected payload PAPR would not lead to any advantage on the system level. The very low 1-2 dB PAPR suggested by the CAZAC approach would give almost no advantage over another series with PAPR in the vicinity of 4-5dB. Although the CAZAC waveforms are simple to generate (similarity to the sounding waveforms of the 802.16e) the decoding/reception complexity is extremely high. This is easy to show by means of comparison with BPSK modulated preamble. The estimation process begin with multiplying the incoming preamble (in the frequency domain) with a series of PN sequences (stored at the UT memory). Obviously, the multiplication of a digital series with a sequence of +1, -1 (BPSK) is far more attractive and simpler than the multiplication with a series of complex value numbers (suggested by CAZAC approach)

4. 4Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 4 CAZAC approach would imply a complex HW required to carryout a large number of complex multiplications ( the number is identical to number of pilots within the preamble). The negligible gain of CAZAC preamble on the system level does not justify the massive HW requirements. we recommend use of binary PN sequences. Adequacy of proposed CAZAC scheme

5. 5Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 5 Attributes of PN sequences needed to support WRAN deployment with Reuse factor 1/3 (use of aggregated channels)

6. 6Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 6 In multi-cell deployment, the popular deployment is with Hexagon like cells. This allows the use of multiple different allocation within the cell (Reuse factor < 1) Reuse 1/3 deployment calls for decimated preamble with factor 3. This means that each segment uses a different set of pilot in Preamble (e.g. every 3n+k, K= 0,1,2). This preamble structure makes sure that the transmitted preamble by all 3 segments remain orthogonal (in the frequency domain) Simulation studies also show that in many scenarios (especially in the low CINR regime) the capacity of a cell with reuse less than 1 (e.g. 1/3) is higher than that in the elementary Reuse 1. We believe that similar deployment ideas will be predicted in the 80-2.22 standard. It is therefore important to adhere to the decimation with factor 3 for use as the 802.22 preambles. Support for Channel aggregation

7. 7Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 7 0 3 6 9 12 15 18 21 24 27 30 33 Preamble with 3 repetitions (for three different sectors) 3 different Binary PN Sequences each shifted by one subcarrier (k= 0,1,2), allocated for three different sectors, supports resuse 1/3 (Aggregated channels) Interference mitigation among sectors, differentiation among sectors Sub carriers Preamble Binary PN Sequences 1 4 7 10 13 17 20 23 26 29 32 +1

8. 8Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 8 Seg Different PN sequence, each to one of the three sectors Reuse 1/3

9. 9Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 9 Coverage - Simulations  Multi Sector Coverage, 3 Sectors, 3 Frequencies, achieves 2.8Bits/s/Hz/Cell, 22.5Mbps/Sector

10. 10Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 10 DL preamble and Ranging process

11. 11Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 11 The CDMA like synchronization is achieved by allocating several of the usable Sub-Channels for the Ranging process, the logic unit they consist is called a Ranging Sub-Channel. Onto the Ranging Sub-Channel users modulate a Pseudo Noise (PN) sequence using BPSK modulation The Base Station detects the different sequences and uses the CIR that he derives from the sequences for: –Time and power synchronization –Decide on the user modulation and coding Ranging Process

12. 12Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 12 Subscriber Units at the Current OFDMA Symbol = 3 Sub-Channels Allocated to Subscriber-Unit #1 = 12 Sub-Channels Allocated to Subscriber-Unit #2 = 9 Sub-Channels Allocated to Subscriber-Unit #3 = 6 Number Of New Subscriber-Units Requesting Services = 3 All Subscriber-Units Suffer Different Multi-Paths and different Attenuation's Effectiveness of DL Preamble and Ranging Example

13. 13Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 13 Constellation at the Base Station

14. 14Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 14 Users Separation

15. 15Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 15 User Estimation 1 Example - Results

16. 16Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 16 User Estimation 2 Results

17. 17Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 17 User Estimation 3 Results

18. 18Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 18 Finding New Subscriber-Units Requesting Services, Using the Ranging Pilots (CDMA/OFDM Techniques) Results Synchronization is achieved using DL preamble within accuracy of few micro seconds Preamble processing gain is 27dB, adding to that 9dB boosted pilots, overall 36dB Time accuracy at UT (o.1 Microsecond/step) Amp

19. 19Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 19 Simulations results on O-PUSC (Partial)

20. 20Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 20 Scope The purpose is to present performance of OPUSC scheme to various types of channel estimation methods. The simulations were ran with OPUSC frame structure for two profiles of WRAN channels.

21. 21Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 21 Simulations parameters: Bandwidth =6MHz. FFTSize=2048. FEC Size=480; Modulation =QPSK CTC coding. Coding rate=1/2. Guard Interval=256.

22. 22Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 22 OPUSC Frame Structure Pilot 1 OPUSC Frame 2048 subcarriers

23. 23Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 23 Additional assumptions: The simulation were ran without frequency shift and without phase noise. Since in the OPUSC scheme the pilots in each symbol are allocated not in all subcarriers, we used linear interpolation to perform channel estimation.

24. 24Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 24 Channel parameters:. 0.37Hz0.17Hz2.5 Hz0.13Hz00.1 Hz Doppler frequency -20 Db-16 Db-22 Db-7 Db0-6 Db Relative amplitude 117420-3 Excess delay, msec Path6Path5Path4Path3Path2Path1Profile 2 0.37Hz0.17Hz0.13Hz2.5 Hz0.1 Hz0 Doppler frequency -19 Db-24 Db-22 Db-15 Db-7 Db0 Relative amplitude 211311830 Excess delay, msec Path6Path5Path4Path3Path2Path1Profile 1

25. 25Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 25 Channel parameters The point spread function(PSD) of each tap is defined as follows:

26. 26Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 26 Reference Performance: Profile 1 (BER) 123456789 10 -7 10 -6 10 -5 10 -4 10 -3 SNR [dB] 10 -2 10 10 0 OPUSC allocation QPSK 1/2 FEC 480 Profile 1 BER 3 symbols 9 symbols 15 symbols Perfect channel

27. 27Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 27 Reference Performance: Profile 1 (PER) SNR [dB] PER 3 symbols 9 symbols 15 symbols Perfect channel

28. 28Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 28 Reference Performance: Profile 2 (BER) 10 10 0 OPUSC allocation QPSK 1/2 FEC 480 Profile 2 SNR [dB] BER 3 symbols 9 symbols

29. 29Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 29 Reference Performance: Profile 2 (PER) OPUSC allocation QPSK 1/2 FEC 480 Profile 2 SNR [dB] PER 3 symbols 9 symbols

30. 30Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 30 Conclusions: The presented graphs show us that we have BER=1e-5 with SNR=9.5. In order to improve the channel estimation we suggest to aggregate number of frames (3 and 5). From the first graph we see that the aggregation of 5 frames improves the performance in approx. 3.5db to compare with 1 frame and is close to the perfect channel performance.

31. 31Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 31 Water filling concept SNR Threshold Tiles spread Channel behavior, different users Tiles transmission on preferred frequencies Different thresholds for different modulation schemes and coding rates User1 User2

32. 32Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0072r1 Slide 32 Conclusions Preamble with 3 reps is recommended (for 3 different segments), accommodating different deployment scenarios and multi-cell scenarios. PUSC simulation results so far are poor unless used tiles are transmitted in favorable CINR. The concepts presented by ETRI are almost identical to the transmission scheme (US & DS) of the 802.16.e. The changes are mostly semantic. We propose to adopt the concepts presented by ETRI (not necessarily the details.