1. Bandwidth Extension for High Throughput
March 2004
Bandwidth Extension for High Throughput
Eun-young Choi, Heejung Yu, Taehyun Jeon, Sok-kyu Lee
ETRI
Next Generation Wireless LAN Research Team
Eun-young Choi, ETRI

2. Contents Why is bandwidth extension needed? BW extension schemes
March 2004
Contents
Why is bandwidth extension needed?
BW extension schemes
Clock doubling scheme
Dual a scheme
System with New OFDM parameters
Conclusion
Eun-young Choi, ETRI

3. Why Bandwidth Extension? 4 Tx ant. in 20MHz vs. 2 Tx ant in 40MHz
March 2004
Why Bandwidth Extension? 4 Tx ant. in 20MHz vs. 2 Tx ant in 40MHz
To achieve about 200Mbps in PHY layer, 4 transmit antenna is required in 20MHz BW.
4 Tx ant. : high RF cost, high modem complexity
40MHz BW and 2 Tx antennas can be better choice.
Problems
reducing the number of channels
20MHz BW regulations in some countries
Eun-young Choi, ETRI

4. Bandwidth Extension Clock doubling Dual 11a System with
March 2004
Bandwidth Extension
Clock doubling
Dual 11a
System with
new OFDM parameters
64 subcarrier
40MHz
64 subcarrier
64 subcarrier
40MHz
20MHz
TBD subcarrier
40MHz
Eun-young Choi, ETRI

5. Bandwidth Extension Clock doubling Dual 11a
March 2004
Bandwidth Extension
Clock doubling
802.11a modem with clock switching(double clock)
Dual 11a
802.11a modem with parallel architecture
System with new OFDM parameters
New modem for TBD subcarriers
Eun-young Choi, ETRI

6. Clock doubling Shortened guard interval (CP : 400nsec)
March 2004
Clock doubling
Shortened guard interval (CP : 400nsec)
induce performance loss in large space
Shortened preamble duration
performance loss in signal detection, AGC, …
Need the compatibility scheme, such as protection mechanism
Loss in throughput
Eun-young Choi, ETRI

7. Dual 802.11a The simple way to implement
March 2004
Dual a
The simple way to implement
Utilizing parallel architecture of legacy 11a PHY
Easy to achieve the compatibility
Selection single channel operation
Eun-young Choi, ETRI

8. System with new OFDM parameters
March 2004
System with new OFDM parameters
The optimal PHY for 40MHz channel
Determine FFT size, CP length, subcarriers/pilots allocation and so on.
For compatibility, both n and a are necessary
Eun-young Choi, ETRI

9. March 2004
Conclusion
For n, dualband + 2 Tx ant scheme is more reasonable than single band + 4 Tx ant scheme.
In dualband methods, dual a is more preferable
Eun-young Choi, ETRI