1. 1Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 1 OFDMA Single Channel Harmonization IEEE P802.22 Wireless RANs Date: 2007.21.02 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 IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs 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.: IEEE802.22-07-0000 r3 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.: IEEE802.22-07-0000 r3 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.: IEEE802.22-07-0000 r3 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.: IEEE802.22-07-0000 r3 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.: IEEE802.22-07-0000 r3 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.: IEEE802.22-07-0000 r3 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.: IEEE802.22-07-0000 r3 Slide 8 Seg Different PN sequence, each to one of the three sectors Multicell Deployment with Reuse 1/3 Optimized deployment and better coverage of the sector No interference from antenna backlobes on adjacent sectors

9. 9Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 9 DL structure in Reuse 1/3 Each one of the three sectors of the cell has a known allocation of the subchannels for FCH. 4 subchannels (# 0,1,2 and 3) extending over two symbols are allocated to FCH0 (the first sector) 4 subchannels (#10, 11,12 and 13) extending over 2 symbols are allocated to FCH1 4 Subchannels (# 20, 21, 22 and 23) extending over 2 symbols are allocated to FCH2 Each FCHx (x = 0, 1, 2) is associated with one of the three preambles, therefore the user synchronized to the preamble of a specific sector knows which subchannels are allocated to FCH associated with that sector. Subcarriers in each Sub-channel (UL and DL) are distributed over the entire frequency band No impact on OH.

10. 10Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 10 Preamble 3 reps OFDM Symbols 0123 ……… 0123 ……… 10 11 12 13 … …… …. 20 21 22 23 … … ……. FCH 2 FCH 1 FCH 0 1 2 3 4 Sub-Channels DL Map Major Group 0 Major Group 1 Major Group 2 UL Map UL DL structure in Reuse 1/3

11. 11Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 11 Multicell deployment with Reuse ½ (4 sectors) Base Station Poor coverage of the sector Opposite sector in same cell could suffer interference from antenna backlobes. Use of only 2 sectors or 4 sectors is not suitable for multicell deployment Multicell deplyment should use hexagonal cell

12. 12Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 12 SINR CDF with Reuse 1/1 Capacity(DL) = 0.42 bps/Hz

13. 13Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 13 SINR CDF with Reuse 1/3 Capacity(DL) = 0.71 bps/Hz Mobility scenario

14. 14Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 14 DL preamble and Ranging process

15. 15Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 15 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

16. 16Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 16 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

17. 17Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 17 Constellation at the Base Station

18. 18Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 18 Users Separation

19. 19Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 19 User Estimation 1 Example - Results

20. 20Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 20 User Estimation 2 Results

21. 21Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 21 User Estimation 3 Results

22. 22Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 22 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

23. 23Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 23 Simulations results on O-PUSC (Partial)

24. 24Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 24 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.

25. 25Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 25 Simulations parameters: Bandwidth =6MHz. FFTSize=2048. FEC Size=480; Modulation =QPSK CTC coding. Coding rate=1/2. Guard Interval=256.

26. 26Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 26 OPUSC Frame Structure Pilot 1 OPUSC Frame 2048 subcarriers

27. 27Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 27 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.

28. 28Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 28 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

29. 29Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 29 Channel parameters The point spread function(PSD) of each tap is defined as follows:

30. 30Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 30 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

31. 31Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 31 Reference Performance: Profile 1 (PER) SNR [dB] PER 3 symbols 9 symbols 15 symbols Perfect channel

32. 32Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 32 Reference Performance: Profile 2 (BER) 10 10 0 OPUSC allocation QPSK 1/2 FEC 480 Profile 2 SNR [dB] BER 3 symbols 9 symbols

33. 33Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 33 Reference Performance: Profile 2 (PER) OPUSC allocation QPSK 1/2 FEC 480 Profile 2 SNR [dB] PER 3 symbols 9 symbols

34. 34Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 34 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.

35. 35Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 35 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

36. 36Runcom Technologies Ltd. Submission Eli Sofer, Runcom February 2007 Doc.: IEEE802.22-07-0000 r3 Slide 36 Conclusions Preamble with 3 reps is recommended (for 3 different segments), accommodating different deployment scenarios and multi-cell scenarios. Optional 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.