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 eychoi@etri.re.kr Eun-young Choi, ETRI

Contents Why is bandwidth extension needed? BW extension schemes March 2004 Contents Why is bandwidth extension needed? BW extension schemes Clock doubling scheme Dual 802.11a scheme System with New OFDM parameters Conclusion Eun-young Choi, ETRI

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

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

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

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

Dual 802.11a The simple way to implement March 2004 Dual 802.11a 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

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 802.11n and 802.11a are necessary Eun-young Choi, ETRI

March 2004 Conclusion For 802.11n, dualband + 2 Tx ant scheme is more reasonable than single band + 4 Tx ant scheme. In dualband methods, dual 802.11a is more preferable Eun-young Choi, ETRI