1. Submission July 2012 Soo-Young Chang (CSUS) Slide 1 doc.: IEEE802.15-12-0377-00-004m Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Spectra and bandwidth overhead with and without filtering for TG4m OFDM Date Submitted: July 15, 2012 Source: Soo-Young Chang (CSUS) and Cristina Seibert (Silver Spring Networks) Voice: +1 530 574 2741, E-mail: sychang@ecs.csus.edu Re: [802.15.4m] Abstract:Raised cosine filters are examined for OFDM signals to meet the regulatory spectral requirements of white space bands through real data simulations for four proposed OFDM options. Purpose: To provide information on filtering OFDM signals to the 802.15 TG4m group Notice: This document has been prepared to assist the IEEE P802.15. 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 acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

2. Submission July 2012 Soo-Young Chang (CSUS) Slide 2 doc.: IEEE802.15-12-0377-00-004m Spectra and bandwidth overhead with and without filtering for TG4m OFDM Soo-Young Chang July 15, 2012

3. Submission July 2012 Soo-Young Chang (CSUS) Slide 3 doc.: IEEE802.15-12-0377-00-004m SUMMARY OF PROPOSED TG4m OFDM PARAMETERS * Subcarrier spacing – (10416 and 2/3) Hz or (31250/3) Hz OFDM symbol rate – (8 and 1/3) ksymbol/s, which corresponds (4/5)x(31250/3) or 120 μs per symbol – a quarter-duration cyclic prefix (CP; 24 μs) + a base symbol (96 μs) Four OFDM options parameterOption 1Option 2Option 3Option 4 Channel spacing (kHz)1200600400200 Nominal bandwidth (kHz)1094552281156 DFT size128643216 modulationBPSK, QPSK, 16QAM * 15-12-0338-00-004m-phy-proposal-for-tg4m

4. Submission July 2012 Soo-Young Chang (CSUS) Slide 4 doc.: IEEE802.15-12-0377-00-004m OFDM SPECTRAL SHAPES WITHOUT FILTERING

5. Submission July 2012 Soo-Young Chang (CSUS) Slide 5 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITHOUT FILTERING, 128 SUBCARRIERS (OPTION 1)

6. Submission July 2012 Soo-Young Chang (CSUS) Slide 6 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITHOUT FILTERING, 64 SUBCARRIERS (OPTION 2)

7. Submission July 2012 Soo-Young Chang (CSUS) Slide 7 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITHOUT FILTERING, 32 SUBCARRIERS (OPTION 3)

8. Submission July 2012 Soo-Young Chang (CSUS) Slide 8 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITHOUT FILTERING, 16 SUBCARRIERS (OPTION 4)

9. Submission July 2012 Soo-Young Chang (CSUS) Slide 9 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS WITHOUT FILTERING No. of Subcarriers Total bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 128 (Option 1)23.310.9 64 (Option 2)16.28.1 32 (Option 3)6.73.2 16 (Option 4)4.52.2 OFDM signals without filtering do not meet the out-of-band (OOB) - 55dB requirement (unless we allow impractical amount of bandwidth overhead). We need filtering (or pulse shaping) to filter out the out-of-band components.

10. Submission July 2012 Soo-Young Chang (CSUS) Slide 10 doc.: IEEE802.15-12-0377-00-004m OFDM SPECTRAL SHAPES WITH RAISED COSINE FILTERING FOR VARIOUS ROLLOFF FACTORS

11. Submission July 2012 Soo-Young Chang (CSUS) Slide 11 doc.: IEEE802.15-12-0377-00-004m SPECRUM WITH FILTERING, OPTION 1 * Filter order of 256 rolloff=0.1rolloff=0 rolloff=0.5rolloff=0.25 Filter order of 256

12. Submission July 2012 Soo-Young Chang (CSUS) Slide 12 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS ROLLOFF FACTORS (1) No. of subcarriers Rolloff factor Total bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 128 (Option 1) 04.101.51 0.12.750.83 0.251.580.25 0.51.610.26 12.130.52 64 (Option 2) 01.640.55 0.11.300.38 0.250.790.12 0.50.800.13 11.040.25 * Filter order of 256

13. Submission July 2012 Soo-Young Chang (CSUS) Slide 13 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS ROLLOFF FACTORS (2) No. of subcarriers Roll off factor Total bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 32 (Option 3) 00.980.36 0.10.690.21 0.250.380.06 0.50.400.07 10.520.13 16 (Option 4) 00.480.17 0.10.360.11 0.250.270.07 0.50.200.03 10.260.06 * Filter order of 256

14. Submission July 2012 Soo-Young Chang (CSUS) Slide 14 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS ROLLOFF FACTORS (3) 0.250.51.0 0.25 0.5 0.75 1.0 Rolloff factor Bandwidth overhead (MHz) Option 1 Option 2 Option 3 Option 4 0.10

15. Submission July 2012 Soo-Young Chang (CSUS) Slide 15 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS ROLLOFF FACTORS (4) Observations regarding bandwidth and height of skirts of spectra 1.The width of the required band increases as roll-off increases - the relationship should be proportional to (1 + rolloff). 2.The height of the skirts outside the main lobe of the band decreases as rolloff increases. Control of rolloff factors is a very useful way to adjust the out- of-band attenuation, in addition to that of filter orders.

16. Submission July 2012 Soo-Young Chang (CSUS) Slide 16 doc.: IEEE802.15-12-0377-00-004m OFDM SPECTRAL SHAPES WITH RAISED COSINE FILTERING FOR COMBINATIONS OF ROLLOFF FACTORS AND FILTER ORDERS

17. Submission July 2012 Soo-Young Chang (CSUS) Slide 17 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 128 SUBCARRIERS ROLLOFF OF 0 Filter order=512Filter order=256 Filter order=2048Filter order=1024 Option 1

18. Submission July 2012 Soo-Young Chang (CSUS) Slide 18 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 128 SUBCARRIERS ROLLOFF OF 0.1 Filter order=256Filter order=512 Filter order=1024Filter order=2048 Option 1

19. Submission July 2012 Soo-Young Chang (CSUS) Slide 19 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 128 SUBCARRIERS ROLLOFF OF 0.25 Filter order=256Filter order=512 Filter order=1024Filter order=2048 Option 1

20. Submission July 2012 Soo-Young Chang (CSUS) Slide 20 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 1 (1) Rolloff factorFilter orderTotal bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 02563.851.38 5122.870.89 10242.050.48 20481.720.32 0.12562.870.89 5121.280.10 10241.200.06 20481.190.05 0.252561.540.23 5121.350.13 10241.340.12 20481.340.12

21. Submission July 2012 Soo-Young Chang (CSUS) Slide 21 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 1 (2) 500100015002000 0.25 0.5 0.75 1.0 Filter order Bandwidth overhead (MHz) Rolloff: 0 Rolloff: 0.1 Rolloff: 0.25 0

22. Submission July 2012 Soo-Young Chang (CSUS) Slide 22 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 64 SUBCARRIERS ROLLOFF OF 0 Filter order=256Filter order=128 Filter order=1024Filter order=512 Option 2

23. Submission July 2012 Soo-Young Chang (CSUS) Slide 23 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 64 SUBCARRIERS ROLLOFF OF 0.1 Filter order=256Filter order=128 Filter order=1024Filter order=512 Option 2

24. Submission July 2012 Soo-Young Chang (CSUS) Slide 24 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 64 SUBCARRIERS ROLLOFF OF 0.25 Filter order=256Filter order=128 Filter order=1024Filter order=512 Option 2

25. Submission July 2012 Soo-Young Chang (CSUS) Slide 25 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 2 (1) Rolloff factorFilter orderTotal bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 01282.761.11 2561.850.65 5121.390.42 10241.070.26 0.11282.711.08 2561.250.35 5120.620.04 10240.600.03 0.251281.640.55 2560.850.15 5120.670.06 10240.670.06

26. Submission July 2012 Soo-Young Chang (CSUS) Slide 26 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 2 (2) 2505007501000 0.25 0.5 0.75 1.0 Filter order Bandwidth overhead (MHz) Rolloff: 0 Rolloff: 0.1 Rolloff: 0.25 0

27. Submission July 2012 Soo-Young Chang (CSUS) Slide 27 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 32 SUBCARRIERS ROLLOFF OF 0 Filter order=64Filter order=128 Filter order=256Filter order=512 Option 3

28. Submission July 2012 Soo-Young Chang (CSUS) Slide 28 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 32 SUBCARRIERS ROLLOFF OF 0.1 Filter order=64Filter order=128 Filter order=256Filter order=512 Option 3

29. Submission July 2012 Soo-Young Chang (CSUS) Slide 29 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 32 SUBCARRIERS ROLLOFF OF 0.25 Filter order=64Filter order=128 Filter order=256Filter order=512 Option 3

30. Submission July 2012 Soo-Young Chang (CSUS) Slide 30 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 3 (1) Rolloff factorFilter orderTotal bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 0641.800.77 1281.300.52 2560.980.36 5120.720.23 0.1641.800.77 1281.160.45 2560.720.23 5120.330.03 0.25641.670.70 1280.750.24 2560.360.05 5120.340.04

31. Submission July 2012 Soo-Young Chang (CSUS) Slide 31 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 3 (2) 125250375500 0.25 0.50 0.75 1.0 Filter order Bandwidth overhead (MHz) Rolloff: 0 Rolloff: 0.1 Rolloff: 0.25 0

32. Submission July 2012 Soo-Young Chang (CSUS) Slide 32 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 16 SUBCARRIERS ROLLOFF OF 0 Filter order=32Filter order=64 Filter order=128Filter order=256 Option 4

33. Submission July 2012 Soo-Young Chang (CSUS) Slide 33 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 16 SUBCARRIERS ROLLOFF OF 0.1 Filter order=32Filter order=64 Filter order=128Filter order=256 Option 4

34. Submission July 2012 Soo-Young Chang (CSUS) Slide 34 doc.: IEEE802.15-12-0377-00-004m SPECTRUM WITH FILTERING, 16 SUBCARRIERS ROLLOFF OF 0.25 Filter order=32Filter order=64 Filter order=128Filter order=256 Option 4

35. Submission July 2012 Soo-Young Chang (CSUS) Slide 35 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 4 (1) Rolloff factorFilter orderTotal bandwidth Use (MHz) Guard band needed at each side of TV band (MHz) 0321.770.82 640.950.41 1280.690.28 2560.530.20 0.1321.770.82 640.970.42 1280.650.25 2560.380.12 0.25321.640.75 640.900.38 1280.410.14 2560.190.03

36. Submission July 2012 Soo-Young Chang (CSUS) Slide 36 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS, OPTION 4 (2) 62.5125187.5250.025.05.75.10 Filter order Bandwidth overhead (MHz) Rolloff: 0 Rolloff: 0.1 Rolloff: 0.25 0

37. Submission July 2012 Soo-Young Chang (CSUS) Slide 37 doc.: IEEE802.15-12-0377-00-004m JOINT CONSIDERATION OF ROLLOFF FACTORS AND FILTER ORDERS TO MINIMIZE BANDWIDTH OVERHEAD AT EDGE OF A TV BAND

38. Submission July 2012 Soo-Young Chang (CSUS) Slide 38 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS ROLLOFF FACTORS Filter order: 256 0.250.51.0 0.25 0.5 0.75 1.0 Rolloff factor Bandwidth overhead (MHz) Option 1 Option 2 Option 3 Option 4 0.10

39. Submission July 2012 Soo-Young Chang (CSUS) Slide 39 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS (1) For Option 1 500100015002000 0.25 0.5 0.75 1.0 Filter order Bandwidth overhead (MHz) Roll off: 0 Roll off: 0.1 Roll off: 0.25 0

40. Submission July 2012 Soo-Young Chang (CSUS) Slide 40 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS (2) For Option 2 2505007501000 0.25 0.5 0.75 1.0 Filter order Bandwidth overhead (MHz) Roll off: 0 Roll off: 0.1 Roll off: 0.25 0

41. Submission July 2012 Soo-Young Chang (CSUS) Slide 41 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS (3) For Option 3 125250375500 0.25 0.50 0.75 1.0 Filter order Bandwidth overhead (MHz) Roll off: 0 Roll off: 0.1 Roll off: 0.25 0

42. Submission July 2012 Soo-Young Chang (CSUS) Slide 42 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS FILTER ORDERS (4) For Option 4 62.5125187.5250 0.25 0.5 0.75 1.0 Filter order Bandwidth overhead (MHz) Roll off: 0 Roll off: 0.1 Roll off: 0.25 0

43. Submission July 2012 Soo-Young Chang (CSUS) Slide 43 doc.: IEEE802.15-12-0377-00-004m BANDWIDTH OVERHEAD ANALYSIS FOR VARIOUS ROLLOFFS AND FILTER ORDERS Observations regarding bandwidth and height of skirts of spectra 1.The width of the required band increases as roll-off increases - the bandwidth should be proportional to (1 + rolloff). 2.The height of the skirts outside the main lobe of the band decreases as roll-off increases. 3.The height of the skirts outside the main lobe of the band decreases as filter order increases. Rolloff factor is a very useful parameter to control the out-of- band attenuation, in addition to the filter order. To achieve out-of-band requirement, the design parameter choice should depend on the tradeoff between rolloff factor (which requires additional bandwidth) and filter order (which affects computation complexity). – For filter order of 512 and greater, rolloff of 0.1 results in less bandwidth overhead than rolloff of 0.25.

44. Submission July 2012 Soo-Young Chang (CSUS) Slide 44 doc.: IEEE802.15-12-0377-00-004m JOINT CONSIDERATION AND CONCULUSION (1) Factors for joint optimization of the two parameter choices of rolloff factor and filter order – Each OFDM option can have a different combination of rolloff factor and filter order to achieve an appropriate bandwidth overhead. Option 1 needs the largest bandwidth overhead to satisfy -55.4 dB attenuation requirement for a fixed rolloff and a fixed filter order. Other options need smaller rolloffs and filter orders for the same bandwidth overhead. – Simple system implementation should be considered. Smaller filter order is more desirable. – Required bandwidth increases as rolloff increases. Smaller rolloff is more desirable. From the above three factors, for pulse shaping of TG4m systems a raised cosine filter with – rolloff factor of 0.1 and filter order of 512 for Option 1, – rolloff factor of 0.2 and filter order of 256 for Option 2, – rolloff factor of 0.1 and filter order of 256 for Option 3, and – rolloff factor of 0.1 and filter order of 128 for Option 4 is recommended so that the bandwidth overhead at the edge of TV band is at most 0.25MHz.

45. Submission July 2012 Soo-Young Chang (CSUS) Slide 45 doc.: IEEE802.15-12-0377-00-004m JOINT CONSIDERATION AND CONCULUSION (2) By using the above recommended raised cosine filtering, the following channels can be accommodated in a 6MHz TV band. OFDM option Recommended filter parameters Bandwidth overhead for -55dB attenuation (MHz) Channel spacing (MHz) No. of channels in a 6MHz TV band * Guard band at edge of TVBD (MHz) Rolloff factor Filter order Option 10.252560.231.240.6 Option 20.22560.210.690.3 Option 30.12560.230.4130.4 Option 40.11280.250.2270.3 * At least 0.25MHz bandwidth overhead should be considered to meet the FCC’s new out-of- band emission constraints. (FCC Third MO&O, FCC-12-36A1, April. 2012.)