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Impact of MB-OFDM and DS-UWB Interference - Part 2

Investigating the impact of MB-OFDM and DS-UWB interference on a C-band DTV receiver through simulation.

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Impact of MB-OFDM and DS-UWB Interference - Part 2

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Impact of MB-OFDM and DS-UWB Interference — Part 2] Date Submitted: [] Source: [Torbjorn Larsson] Company [Paradiddle Communications] Address [13141 Via Canyon Drive, San Diego, CA 92129, USA] Voice:[+1 858 538-3434], FAX: [+1 858 538-2284], E-Mail:[tlarsson@san.rr.com] Re: [Analysis of the impact of MB-OFDM and DS-UWB interference on a DTV receiver made in earlier contributions, in particular 802.15-04/0412r0, 802.15-04/547r0 and 04/451/r2] Abstract: [The impact of MB-OFDM and DS-UWB interference on a C-band DTV receiver is investigated by simulation] Purpose: [To present an unbiased comparison of the impact of MB-OFDM and DS-UWB interference based on a minimal set of universally accepted assumptions] 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. Torbjorn Larsson

  2. Impact of MB-OFDM and DS-UWB Inteference — Part 2 Torbjorn Larsson Paradiddle Communications, Inc. Torbjorn Larsson

  3. Motivation and Objective • Motivated by the following three contributions: • 04/0412r0, In-band Interference Properties of MB-OFDM, by C. Razell, Philips • 04/547r0, Responses to “In-Band Interference Properties of MB-OFDM”, by C. Corral, G. Rasor and S. Emami, Freescale Semiconductor • 04/451/r2, “Multiband OFDM Interference on In-band QPSK Receivers Revisited”, by C. Corral, S. Emami and G. Rasor, , Freescale Semiconductor • The above contributions focused on the impact of MB-OFDM interference on a DTV victim receiver • In contrast, the objective here is to quantify the difference in the impact of interference from MB-OFDM and DS-UWB Torbjorn Larsson

  4. C-Band DTV Systems • The C-band downlink spans 3.7 – 4.2 GHz • C-band antennas are typically 6 – 12 feet in diameter • Based on the DVB-S (Digital Video Broadcasting – Satellite) standard (EN 300 421) • DVB-S was designed for MPEG-2 broadcasting in the Ku-band, but is also used in the C-band • DVB-S does not specify a unique set of data rates or symbol rates; However… • Typical transponder bandwidth is 36 MHz (33 MHz also used) • Typical symbol rate 27 – 29 Msps • DVB-S2 is the next generation with improved bandwidth efficiency and FEC Torbjorn Larsson

  5. DVB-S Torbjorn Larsson

  6. Typical C-Band Downlink Channelization (Telesat satellite Anik F2. Footprint: North America) • Total of 24 channels • Each polarization has 12 channels • Transponder bandwidth is 36 MHz with a 4 MHz guard band • The center frequencies are separated by 40 MHz • The center frequencies for the two polarizations are offset by 20 MHz • The result is 24 center frequencies separated by 20 MHz Torbjorn Larsson

  7. DTV Simulation Model • Excludes Reed-Solomon coding and interleaving • Impossible to simulate error rates with RS coding • Symbol rate: 28 Msps • No quantization (including input to Viterbi decoder) • Ideal pulse shaping/matched filters (0.35 roll-off) • No nonlinarity • No frequency offset • No phase noise • Pre-computed phase error and time offset • Receiver noise figure: 4 dB • Code rates 1/2 and 7/8 Torbjorn Larsson

  8. MB-OFDM Transmitter Model • Based on the Jan. 2005 release of the MB-OFDM PHY spec • Complete Matlab implementation of the specifications • System operating in band-hopping mode • Includes (5-bit) DAC and realistic filter characteristics • Spectral pre-shaping to compensate for non-ideal filter characteristics (=> worst-case in this context!) • Channel number 9 (Band group 1, TFC 1) • Data rate “110” Mbps (106.7 Mbps) Torbjorn Larsson

  9. DS-UWB Transmitter Model • Based on the January 2005 release of the DS-UWB PHY specifications (P802.15-04/0137r4) • Complete Matlab implementation of the specifications • No DAC • Ideal RRC pulse shaping filter truncated to 12 chip periods (=> worst-case) • Channel number 1 (chip rate: 1313 Mcps) • Data rate: “110” Mbps (109.417 Mbps) • BPSK modulation • Spreading code for preamble and header (PAC): -1 0 +1 -1 -1 -1 +1 +1 0 +1 +1 +1 +1 -1 +1 -1 +1 +1 +1 +1 -1 -1 +1 • Spreading code for frame body: +1 0 0 0 0 0 Torbjorn Larsson

  10. Interference Spectra Resolution: 10 kHz PSD averaged over 10 packets (roughly 0.9 ms) • Transmit power is set so as to push each spectrum as close as possible to the FCC limit (worst-case condition) • MB-OFDM transmit power is -10.3 dBm • DS-UWB transmit power is -10.8 dBm (data rate dependent) Torbjorn Larsson

  11. Interference Spectra – Close Up • Both spectra exhibit substantial variations • Solution: run simulation for multiple DTV center frequencies DTV center frequencies Torbjorn Larsson

  12. Amplitude Histogram: Wideband (without Multipath) Data rate: 110 kbps PAR = 12.0 dB PAR = 11.9 dB Torbjorn Larsson

  13. Amplitude Histogram: Wideband (with Multipath) PAR = 14.1 dB PAR = 14.2 dB Data rate: 110 kbps 100 multipath channel realizations Torbjorn Larsson

  14. Amplitude Histogram: Output of DTV Matched Filter (with Multipath) Center frequency = 4 GHz 100 multipath channel realizations Torbjorn Larsson

  15. Output of Matched Filter (Close-Up) Torbjorn Larsson

  16. Changes Since November 2004 • All simulations carried out with center frequencies according to channelization plan on slide 6 • 3.72 GHz to 4.18 GHz in steps of 20 MHz • Added multipath (CM3, no shadowing) • Increased symbol rate from 27 to 28 Msps Torbjorn Larsson

  17. Simulation Block Diagram • Attenuation 1 is set so that the received DTV power is 3 dB above sensitivity • Each simulation is performed with all 24 DTV center frequencies • Simulation results are plotted as a function of center frequency and attenuation 2 Torbjorn Larsson

  18. DTV Sensitivity (NF = 4 dB) Defines sensitivity Torbjorn Larsson

  19. DTV Sensitivity (NF = 4 dB) (Symbol rate: 28 Msps) Torbjorn Larsson

  20. BER versus Center Frequency Code Rate 1/2, without multipath Interference attenuation = 67 dB Torbjorn Larsson

  21. BER versus Center Frequency Code Rate 1/2, with multipath Interference attenuation = 71 dB 100 multipath channel realizations Torbjorn Larsson

  22. Two Performance Metrics • Compute average error rate over the 24 center frequencies • Select maximum error rate from the 24 center frequencies Torbjorn Larsson

  23. Average BER Code Rate 1/2, with multipath Torbjorn Larsson

  24. Maximum BER Code Rate 1/2, with multipath Torbjorn Larsson

  25. BER versus Center Frequency Code Rate 7/8, with multipath Interference attenuation = 71 dB 100 multipath channel realizations Torbjorn Larsson

  26. Average BER Code Rate 7/8, with multipath Torbjorn Larsson

  27. Worst-Case BER Code Rate 7/8, with multipath Torbjorn Larsson

  28. Conclusions • For DTV code rate 1/2, there is practically no difference between the two interfering waveforms • The difference increases with code rate • MB-OFDM interference is more bursty in nature and thus has more impact for higher code rates • For DTV code rate 7/8, MB-OFDM is ≈ 1.3 dB worse than DS-UWB @ BER 2·10-4 Torbjorn Larsson

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