Limitation on Range Extension using Multiple Antennas March 2004 Limitation on Range Extension using Multiple Antennas Heejung Yu, Taehyun Jeon, and Sok-Kyu Lee ETRI Next Generation Wireless LAN Research Team heejung@etri.re.kr Heejung Yu, ETRI

Contents Introduction Performance (refer to 11-03-0845-00-000n) March 2004 Contents Introduction Performance (refer to 11-03-0845-00-000n) Problem in Range extension Conclusion Heejung Yu, ETRI

Introduction Use of multiple antennas for range extension March 2004 Introduction Use of multiple antennas for range extension We can get diversity gain without bandwidth loss and power increase Diversity gain enables coverage extension Heejung Yu, ETRI

Performance Extended range depends on the channel parameters. March 2004 Performance Extended range depends on the channel parameters. Reference : 11-03-0845-00-000n 6.8dB SNR improvement Heejung Yu, ETRI

Problems in Range extension March 2004 Problems in Range extension In BSS with only 11n devices, we can achieve range extension with multi-antenna 11n mode for control, management and data frames. In other cases, control and management frames, such as RTS-CTS, ACK and so on, should be transmitted in the legacy 11a mode for compatibility. We cannot achieve range extension because of the coverage limitation of control and management frames. Heejung Yu, ETRI

Problems in Range extension March 2004 Problems in Range extension Uplink : STA=>AP Uplink(STAAP) coverage is extended to blue circle Heejung Yu, ETRI

Problems in Range extension March 2004 Problems in Range extension Downlink : AP  STA Downlink(APSTA) coverage for legacy devices is pink circle Heejung Yu, ETRI

Problems in Range extension March 2004 Problems in Range extension 11a STA is a hidden node Collision between 11a and 11n STA can be occurred. Heejung Yu, ETRI

Benefit of Alamuti code and MRC March 2004 Benefit of Alamuti code and MRC Legacy 6Mbps region is improved 12 and 18Mbps region by MRC and Alamouti + MRC, respectively. 12Mbps 18Mbps Heejung Yu, ETRI

March 2004 Conclusion Several documents say that Multiple antenna scheme is used for range extension, but we cannot perfectly achieve this as maintaining compatibility with 11a Benefit of Alamouti and MRC is throughput improvement We overcome or neglect the collision(hidden node) problem, range extension with MRC is possible. Heejung Yu, ETRI