1. 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 Yu, ETRI

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

3. 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

4. Performance Extended range depends on the channel parameters.
March 2004
Performance
Extended range depends on the channel parameters.
Reference : n
6.8dB SNR
improvement
Heejung Yu, ETRI

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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