1. OFDM System Performance
November 2000
OFDM System Performance
Karen Halford, Steve Halford and Mark Webster
K. Halford, S. Halford and M. Webster

2. Outline of Proposal Presentations
November 2000
Outline of Proposal Presentations
TGg Regulatory Approval Plan Speaker: Jim Zyren
Overview of OFDM for High Rate Speaker: Steve Halford
Reuse of b Preambles with OFDM Speaker: Mark Webster
Ultra-short Preamble with HRb OFDM Speaker: Mark Webster
OFDM System Performance Speaker: Steve Halford
Power Am Effects for HRb OFDM Speaker: Mark Webster
Channelization for HRb OFDM Speaker: Mark Webster
Phase Noise Sensitivity for HRb OFDM Speaker: Mark Webster
Implementation and Complexity Issues for OFDM Speaker: Steve Halford
Why OFDM for the High Rate b Extension? Speaker: Jim Zyren
K. Halford, S. Halford and M. Webster

3. Outline of Presentation
November 2000
Outline of Presentation
5.1 AWGN Performance
5.2 Rayleigh Fading Performance
5.3 Multipath Performance
5.3.1 Exponential Channel with Flat Fading
5.3.2 Exponential Channel without Flat Fading (Normalized)
5.3.3 PER sweeps from 1% to 10 %
5.4 Throughput Performance
5.5 Performance Against CW Jammer (FCC Test)
K. Halford, S. Halford and M. Webster

4. 5.1 AWGN Performance: 100 Byte Packets
November 2000
5.1 AWGN Performance: 100 Byte Packets
K. Halford, S. Halford and M. Webster

5. 5.1 AWGN Performance: 1000 Byte Packets
November 2000
5.1 AWGN Performance: 1000 Byte Packets
K. Halford, S. Halford and M. Webster

6. 5.1 AWGN Performance: 2346 Byte Packets
November 2000
5.1 AWGN Performance: 2346 Byte Packets
K. Halford, S. Halford and M. Webster

7. 5.1 AWGN Performance: 1% and 10 % PER for 1000 Byte Packets
November 2000
5.1 AWGN Performance: 1% and 10 % PER for 1000 Byte Packets
Eb/No required for 1 % PER
Eb/No required for 10 % PER
K. Halford, S. Halford and M. Webster

8. 5.2 Rayleigh Fading Performance: Block Diagram
November 2000
5.2 Rayleigh Fading Performance: Block Diagram
Calculate Noise Power
(N0)
Generate
Noise
Measure
energy per bit
Measure
Packet Error
Rate
Transmitter
Model
Packet Error
Rate x +
Receiver
Model
Rayleigh
Coefficient
Packet Length
Data Rate
K. Halford, S. Halford and M. Webster

9. 5.2 Rayleigh Fading Performance: 1000 Byte Packets
November 2000
5.2 Rayleigh Fading Performance: Byte Packets
K. Halford, S. Halford and M. Webster

10. 5.2 Rayleigh Fading Performance: 1% and 10 % PER for 1000 Byte Packets
November 2000
5.2 Rayleigh Fading Performance: 1% and 10 % PER for 1000 Byte Packets
Eb/No required for 1 % PER
Eb/No required for 10 % PER
K. Halford, S. Halford and M. Webster

11. 5.3.1 Multipath Performance with Flat Fading: Block Diagram
November 2000
5.3.1 Multipath Performance with Flat Fading: Block Diagram
Calculate Noise Power
(N0)
Generate
Noise
Measure
energy per bit
Measure
Packet Error
Rate
Packet Error
Rate
Exponential
Channel Model
Transmitter
Model
Receiver
Model
Packet Length
Data Rate
Sample Rate
Delay Spread
K. Halford, S. Halford and M. Webster

12. 5.3.1 Multipath Performance with Flat Fading: Matlab® Code
November 2000
5.3.1 Multipath Performance with Flat Fading: Matlab® Code
K. Halford, S. Halford and M. Webster

13. 5.3.1 Multipath Performance with Flat Fading: Eb/No
November 2000
5.3.1 Multipath Performance with Flat Fading: Eb/No
K. Halford, S. Halford and M. Webster

14. 5.3.1 Multipath Performance with Flat Fading: SNR
November 2000
5.3.1 Multipath Performance with Flat Fading: SNR
K. Halford, S. Halford and M. Webster

15. 5.3.2 Multipath Performance without Flat Fading: Block Diagram
November 2000
5.3.2 Multipath Performance without Flat Fading: Block Diagram
Calculate Noise Power
(N0)
Generate
Noise
Measure
energy per bit
Measure
Packet Error
Rate
Exponential
Channel Model
Transmitter
Model
Receiver
Model
Packet Error
Rate
Packet Length
Data Rate
Sample Rate
Delay Spread
K. Halford, S. Halford and M. Webster

16. 5.3.2 Multipath Performance without Flat Fading: Eb/No
November 2000
5.3.2 Multipath Performance without Flat Fading: Eb/No
K. Halford, S. Halford and M. Webster

17. 5.3.2 Multipath Performance without Flat Fading: SNR
November 2000
5.3.2 Multipath Performance without Flat Fading: SNR
K. Halford, S. Halford and M. Webster

18. 5.3.3: Multipath Sweeps: 1% to 10%
November 2000
5.3.3: Multipath Sweeps: 1% to 10%
Comparison Item 24
For each modulation mode detemine and state the SNR (Es/No) at which in AWGN only, the waveform can achieve a PER of 0.01 for packets lengths of 1000B. Using the multipath model used in 23b above, fix the amount of AWGN at the 0.01 PER level for AWGN only. Increase the RMS delay spread until the PER for 1000B packets reach State the RMS delay spread at this point.
Answer: 0.0 nSeconds for all rates
Why ?
K. Halford, S. Halford and M. Webster

19. 5.3.3 Multipath Sweeps: 1% to 10%
November 2000
5.3.3 Multipath Sweeps: 1% to 10%
PER Curves are very steep --
about 2 dB separates the 1% from the 10 % point
K. Halford, S. Halford and M. Webster

20. 5.3.3 Multipath Sweeps: 1% to 10%
November 2000
5.3.3 Multipath Sweeps: 1% to 10%
Rayleigh fading causes frequent swings to low SNR level
K. Halford, S. Halford and M. Webster

21. 5.3.3 Multipath Sweeps: 1% to 10%
November 2000
5.3.3 Multipath Sweeps: 1% to 10%
What we ran in place of Comparison Item 24
For each modulation mode detemine and state the SNR (Es/No) at which 25 nSeconds RMS delay, the waveform can achieve a PER of 0.01 for packets lengths of 1000B. Using the multipath model used in 23c above, fix the amount of AWGN at the 0.01 PER level for 25 nSeconds RMS delay. Increase the RMS delay spread until the PER for 1000B packets reach State the RMS delay spread at this point.
K. Halford, S. Halford and M. Webster

22. 5.3.3 Multipath Performance: PER sweeps from 1% to 10%
November 2000
5.3.3 Multipath Performance: PER sweeps from 1% to 10%
K. Halford, S. Halford and M. Webster

23. 5.4 Throughput Performance
November 2000
5.4 Throughput Performance
5.4.1 Preamble Structures
5.4.2 ACK Assumptions
5.4.3 Throughput Analysis
Tables of 100, 1000, 2346 Byte Packets
Plots for full range of packet sizes
5.4.4 Throughput analysis for varying durations of overhead
K. Halford, S. Halford and M. Webster

24. 5.4.1 Preamble Structures: Long and Short Preambles
November 2000
5.4.1 Preamble Structures: Long and Short Preambles
HRb LONG PREAMBLE
Signal
Extension
OFDM
SYNC
PSDU SELECTABLE
OFDM Symbols
@ 6.6, 9.6, 13.2, 19.8, 26.4, 39.3, 52.8 or 59.4 Mbps
PREAMBLE/HEADER
192 usecs
10.9 usecs
~6 usecs
Data Payload
HRb SHORT PREAMBLE
Signal
Extension
PREAM/HDR
72 BITS
@ 1 Mbps
OFDM
SYNC
PSDU SELECTABLE
OFDM Symbols
@ 6.6, 9.6, 13.2, 19.8, 26.4, 39.3, 52.8 or 59.4 Mbps
~6 usecs
96 usecs
10.9 usecs
K. Halford, S. Halford and M. Webster

25. 5.4.1 Preamble Structures: Ultra-Short Preamble
November 2000
5.4.1 Preamble Structures: Ultra-Short Preamble
Proposed Ultra-Short Preamble
Signal
Extension
Data Rate
# bytes of data
Data
Payload
12 Short
Syncs Rep’s
Long
SYNC
PSDU
SELECTABLE
@ 6.6, 9.9, 13.2, 19.8, 26.4, 39.6, 52.8 or 59.4 Mbps
SIGNAL
SYMBOL
16 usecs
3.6 usecs
~6 usecs
K. Halford, S. Halford and M. Webster

26. 5.4.2 ACK Assumptions 1) No RTS/CTS OR MPDU < RTS_Threshold:
November 2000
5.4.2 ACK Assumptions
1) No RTS/CTS OR MPDU < RTS_Threshold:
Many different scenarios,
but the constant is: {MPDU, SIFS, ACK}
source
DIFS
Data
destination
SIFS
ACK
2) RTS/CTS and/or MPDU > RTS_Threshold:
source
DIFS
RTS
SIFS
Data
destination
SIFS
CTS
SIFS
ACK
3) Middle of Fragmented Transmission:
source
SIFS
Fragment 1
destination
SIFS
ACK 1
K. Halford, S. Halford and M. Webster

27. 5.4.2 ACK Assumptions (continued)
November 2000
5.4.2 ACK Assumptions (continued)
Mbps = 20 usec
SIFS
PSDU SELECTABLE
OFDM Symbols
@ 6.6, 9.6, 13.2, 19.8, 26.4, 39.3, 52.8 or 59.4 Mbps
Packet Header
Packet Header
ACK
OFDM PAD
~6 usecs
K. Halford, S. Halford and M. Webster

28. 5.4.3.1 Throughput for 100 Byte Packets
November 2000
Throughput for 100 Byte Packets
K. Halford, S. Halford and M. Webster

29. 5.4.3.1 Throughput for 1000 Byte Packets
November 2000
Throughput for 1000 Byte Packets
K. Halford, S. Halford and M. Webster

30. 5.4.3.1 Throughput for 2346 Byte Packets
November 2000
Throughput for 2346 Byte Packets
K. Halford, S. Halford and M. Webster

31. 5.4.3.2 Throughput with ACK November 2000
K. Halford, S. Halford and M. Webster

32. 5.4.3.2 Throughput without ACK
November 2000
Throughput without ACK
K. Halford, S. Halford and M. Webster

33. 5.4.4 Comparison of Throughput for Variable Overhead for 100 Byte MPDU
November 2000
5.4.4 Comparison of Throughput for Variable Overhead for 100 Byte MPDU
K. Halford, S. Halford and M. Webster

34. November 2000
5.4.4 Comparison of Throughput for Variable Overhead for 1000 Byte MPDU
K. Halford, S. Halford and M. Webster

35. November 2000
5.4.4 Comparison of Throughput for Variable Overhead for 2346 Byte MPDU
K. Halford, S. Halford and M. Webster

36. 5.4.5 Aggregate Throughputs for 2.4 GHz
November 2000
5.4.5 Aggregate Throughputs for 2.4 GHz
Our proposal allows for 3 channels in US 2.4 GHz band
Each channel can coexist in the same area
Aggregate throughput is 3 times single channel throughput
K. Halford, S. Halford and M. Webster

37. 5.5 CW Jammer Test Description
November 2000
5.5 CW Jammer Test Description
CW jammer test steps a CW tone across the signal band in 50 kHz steps. At each step, the jamming level required to to produce the recommended BER is determined. The worst 20% of the J/S levels are discarded and the smallest of the remaining J/S is used as the jamming margin. Processing gain is then calculated according to the following:
K. Halford, S. Halford and M. Webster

38. 5.5 Performance Against CW Jammer
November 2000
5.5 Performance Against CW Jammer
Gp = (S/N)0 + Mj + Lsys
K. Halford, S. Halford and M. Webster