802.11n under the microscope

ABSTRACT

We present an experimental study of IEEE 802.11n (high throughput extension to the 802.11 standard) using commodity wireless hardware. 802.11n introduces a variety of new mechanisms including physical layer diversity techniques, channel bonding and frame aggregation mechanisms. Using measurements from our testbed, we analyze the fundamental characteristics of 802.11n links and quantify the gains of each mechanism under diverse scenarios. We show that the throughput of an 802.11n link can be severely degraded (up ≈85%) in presence of an 802.11g link. Our results also indicate that increased amount of interference due to wider channel bandwidths can lead to throughput degradation. To this end, we characterize the nature of interference due to variable channel widths in 802.11n and show that careful modeling of interference is imperative in such scenarios. Further, as a reappraisal of previous work, we evaluate the effectiveness of MAC level diversity in the presence of physical layer diversity mechanisms introduced by 802.11n.

REFERENCES

• 1: Sanjit Biswas , Robert Morris, ExOR: opportunistic multi-hop routing for wireless networks, Proceedings of the 2005 conference on Applications, technologies, architectures, and protocols for computer communications, August 22-26, 2005, Philadelphia, Pennsylvania, USA
• 2: Szymon Chachulski , Michael Jennings , Sachin Katti , Dina Katabi, Trading structure for randomness in wireless opportunistic routing, Proceedings of the 2007 conference on Applications, technologies, architectures, and protocols for computer communications, August 27-31, 2007, Kyoto, Japan
• 3: M. Heusse, F. Rousseau, G. Berger-Sabbatel, and A. Duda. Performance anomaly of 802.11b. In IEEE INFOCOM 2003.
• 4: Arunesh Mishra , Vivek Shrivastava , Suman Banerjee , William Arbaugh, Partially overlapped channels not considered harmful, Proceedings of the joint international conference on Measurement and modeling of computer systems, June 26-30, 2006, Saint Malo, France
• 5: Allen Miu , Hari Balakrishnan , Can Emre Koksal, Improving loss resilience with multi-radio diversity in wireless networks, Proceedings of the 11th annual international conference on Mobile computing and networking, August 28-September 02, 2005, Cologne, Germany [doi>10.1145/1080829.1080832]
• 6: F. Mlinarsky. Testing 802.11n. In Octoscope, 2007.
• 7: P. Thornycroft. Designed for speed: Network infrastructure in an 802.11n world. In Aruba Networks white paper, 2007.

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.1 Network Architecture and Design
          Subjects: Wireless communication

General Terms:
Experimentation, Measurement, Performance

Keywords:
802.11n, channel bonding, frame aggregation, mac diversity, mimo, performance, phy diversity, wireless