1. Block Spreading for OFDMA
November 2005
doc.: IEEE /0094r0
March 2006
Block Spreading for OFDMA
IEEE P Wireless RANs Date:
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Zhongding Lei, Institute for Infocomm Research, Singapore
Y.-C. Liang, Inst. for Infocomm Research

2. Abstract Block spreading for OFDMA Simulation results Conclusions
November 2005
doc.: IEEE /0094r0
March 2006
Abstract
Block spreading for OFDMA
Simulation results
Conclusions
Zhongding Lei, Institute for Infocomm Research, Singapore
Y.-C. Liang, Inst. for Infocomm Research

3. OFDMA Transmitter w/ Block Spreading
March 2006
OFDMA Transmitter w/ Block Spreading
Preamble/
Pilot
Windowing
Data
OFDMA
Randomizer
FEC
Interleaver
Symbol
Block Spread
& Pulse
Encoder
Mapper
Formulator
Shaping
Zhongding Lei, Institute for Infocomm Research, Singapore

4. Block Spreading (1) OFDMA w/ block spreading
March 2006
Block Spreading (1)
OFDMA w/ block spreading
Transmitter (frequency domain implementation)
P/S
IFFT
(size = NFFT)
Mapped Symbols from SS
Cyclic Prefix
Block Spread
Zhongding Lei, Institute for Infocomm Research, Singapore

5. Block Spreading (2) OFDMA w/ block spreading
March 2006
Block Spreading (2)
OFDMA w/ block spreading
Transmitter (time domain implementation)
Mapped Symbols from SS
Phase Rotation
Cyclic Prefix
Block Spread
Repetition
Zhongding Lei, Institute for Infocomm Research, Singapore

6. Block Spreading (3) March 2006 OFDM Block Spreading Code c1 P/S CP CP
Block K cK CP
Block K
Zhongding Lei, Institute for Infocomm Research, Singapore

7. Frequency domain Processing
March 2006
Block Spreading (4)
Reference Receiver
FFT
Frequency domain Processing
Received Signal
Remove cyclic Prefix
Block Despread
Zhongding Lei, Institute for Infocomm Research, Singapore

8. Block Spreading (5) Block de-spreading in Reference Receivers
March 2006
Block Spreading (5)
Block de-spreading in Reference Receivers
P/S c1 CP CP CP CP
Block 1
Block K cK CP
Zhongding Lei, Institute for Infocomm Research, Singapore

9. Block Spreading (6) Peak power reduction Other benefits f power t
March 2006
Block Spreading (6)
Peak power reduction
Other benefits
Multiuser diversity f
power t
No Block spreading
Block spreading
user 1
user 2 P
P/2
Zhongding Lei, Institute for Infocomm Research, Singapore

10. Simulations (1) Channel A FFT size = 1024 BW = 6 MHz CP = ¼
March 2006
Simulations (1)
Channel A
FFT size = 1024
BW = 6 MHz
CP = ¼
Modulation = QPSK
# of symbols per block = 48
Blocks per packet = 42
Distributed channelization
Runs = 1000
Zhongding Lei, Institute for Infocomm Research, Singapore

11. Simulations (2) Peak power reduction ratio March 2006
Un-coded performance in CM-A
Peak power reduction ratio
3 dB
spreading factor = 2
6 dB
spreading factor = 4
9 dB
spreading factor = 8 B E R
SNR (dB)
Zhongding Lei, Institute for Infocomm Research, Singapore

12. Conclusions Block spreading is promising for WRAN OFDMA systems Merits
March 2006
Conclusions
Block spreading is promising for WRAN OFDMA systems
Merits
Significant peak power reduction
Multiuser diversity
Zhongding Lei, Institute for Infocomm Research, Singapore