1. Nov 2004
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Impact of MB-OFDM and DS-UWB Interference on C Band Receivers]
Date Submitted: []
Source: [Torbjorn Larsson] Company [Paradiddle Communications]
Address [13141 Via Canyon Drive, San Diego, CA 92129, USA]
Voice:[ ], FAX: [ ],
Re: [Analysis of the impact of MB-OFDM and DS-UWB interference on a DTV receiver made in earlier contributions, in particular /547r0 and /0412r0]
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 P 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 P
Torbjorn Larsson

2. Impact of MB-OFDM and DS-UWB Inteference on C-Band Receivers
Nov 2004
Impact of MB-OFDM and DS-UWB Inteference on C-Band Receivers
Torbjorn Larsson
Paradiddle Communications, Inc.
Torbjorn Larsson

3. Motivation and Objective
Nov 2004
Motivation and Objective
Motivated by two 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, S. Emami, Freescale Semiconductor
The emphasis in the above contributions is on qualitative analysis
In contrast, the approach here is “brute force” simulation
Our hope is that the assumptions made are universal enough to be accaptable to the entire a task group
The author is an independent consultant, not affiliated with any UWB company. This work was not carried out under any consulting contract
Torbjorn Larsson

4. C-Band DTV Systems The C-band downlink spans 3.7 – 4.2 GHz
Nov 2004
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 )
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. Nov 2004
DVB-S
Torbjorn Larsson

6. Typical C-Band Downlink Channelization
Nov 2004
Typical C-Band Downlink Channelization
(Telesat satellite Anik F2. Footprint: North America)
Horizontal Polarization
Vertical Polarization
Channel
Center Frequency (GHZ)
Center Frequency (GHz) 1A
3.720 1B
3.740 2A
3.760 2B
3.780 3A
3.800 3B
3.820 4A
3.840 4B
3.860 5A
3.880 5B
3.900 6A
3.920 6B
3.940 7A
3.960 7B
3.980 8A
4.000 8B
4.020 9A
4.040 9B
4.060
10A
4.080
10B
4.100
11A
4.120
11B
4.140
12A
4.160
12B
4.180
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
Nov 2004
DTV Simulation Model
Excludes Reed-Solomon coding and interleaving
Impossible to simulate error rates with RS coding
Will probably favor DS-UWB
Symbol rate: 27 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
Intend to run simulations for all code rates – Results presented only include rate 1/2 and 2/3
Torbjorn Larsson

8. MB-OFDM Transmitter Model
Nov 2004
MB-OFDM Transmitter Model
Based on the Sep release of the MB-OFDM PHY Specifications (P /0493r1)
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
Nov 2004
DS-UWB Transmitter Model
Based on the July 2004 release of the DS-UWB PHY specifications (P /0137r3)
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 ( Mbps)
BPSK modulation
Spreading code for preamble and header (PAC):
Spreading code for frame body:
Torbjorn Larsson

10. Nov 2004
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 dBm
DS-UWB transmit power is dBm (data rate dependent)
Torbjorn Larsson

11. Interference Spectra – Close Up
Nov 2004
Interference Spectra – Close Up
DTV center frequencies
Both spectra exhibit substantial variations
Solution: run simulation for multiple DTV center frequencies
Torbjorn Larsson

12. Simulated DTV Center Frequencies
Nov 2004
Simulated DTV Center Frequencies
Rate 1/2 simulations: 3.8 – 4.3 GHz in steps of 10 MHz
Arbitrary choice across 500 MHz bandwidth
Rate 2/3 simulations: 3.72 – 4.18 GHz in steps of 20 MHz
According to channelization plan on slide 6
Torbjorn Larsson

13. Simulation Block Diagram
Nov 2004
Simulation Block Diagram
Attenuation 1 is set so that the received DTV power is 3 dB above sensitivity
Each simulation is performed with multiple DTC center frequencies
Simulation results are plotted as a function of center frequency and attenuation 2
No multipath!
Torbjorn Larsson

14. BER Performance without Interference
Nov 2004
BER Performance without Interference
Noise Figure = 4 dB
Defines sensitivity
Sensitivity for rate 1/2 is dBm (Eb/No = 3.2 dB)
Sensitivity for rate 2/3 is dBm (Eb/No = 3.7 dB)
Torbjorn Larsson

15. BER versus Center Frequency (Code Rate 1/2)
Nov 2004
BER versus Center Frequency (Code Rate 1/2)
Interference attenuation = 67 dB
Center frequencies separated by 10MHz
Torbjorn Larsson

16. Average BER (Code Rate 1/2)
Nov 2004
Average BER (Code Rate 1/2)
Torbjorn Larsson

17. Worst-Case BER (Code Rate 1/2)
Nov 2004
Worst-Case BER (Code Rate 1/2)
Torbjorn Larsson

18. BER versus Center Frequency (Code Rate 2/3)
Nov 2004
BER versus Center Frequency (Code Rate 2/3)
Interference attenuation = 67 dB
Center frequencies separated by 20MHz
Torbjorn Larsson

19. Average BER (Code Rate 2/3)
Nov 2004
Average BER (Code Rate 2/3)
Torbjorn Larsson

20. Worst-Case BER (Code Rate 2/3)
Nov 2004
Worst-Case BER (Code Rate 2/3)
Torbjorn Larsson

21. Nov 2004
Conclusions
For the two simulated cases (rate 1/2 and 2/3), the difference in average BER across the C-band is 1 dB or less
The difference in worst-case BER is less than 0.5 dB
More general conclusions should be postponed until all code rates have been simulated
Torbjorn Larsson

22. Onward… Run simulations for code rates 3/4, 5/6, 7/8
Nov 2004
Onward…
Run simulations for code rates 3/4, 5/6, 7/8
Run simulations for TFC 3 or 4
Include multipath
Suggestions?
Torbjorn Larsson