A radio multiplexing architecture for high throughput point to multipoint wireless networks

ABSTRACT

WiFi-based point-to-multipoint systems are a cost-effective solution for providing high-bandwidth connectivity to remote rural regions. However, current point-to-multipoint deployments are hampered by several challenges. Their capacity to support a large number of clients simply by increasing the number of radios at the base station is limited because space restrictions on radio towers bound the number of antennas that can be installed at one physical location. Also the limited availability of wireless channels restricts the number of clients that can be simultaneously supported by a base station at any point of time.

In this paper, we explore high-throughput architectures for point-to-multipoint networks. We show how we can increase the number of radios at the base station without increasing the number of antennas simultaneously. We propose a simple yet practical multiplexing design that uses cheap RF combiner/splitter devices for multiplexing several radios onto a single antenna. We also examine a more general design that uses RF switches, and which allows us to allocate radios to antennas dynamically based on client traffic demands.

As a proof of concept, we demonstrate and evaluate the simple case of combining up to three radios operating on different channels onto only one antenna, using off-the-shelf combiner/splitters and attenuators. We show that not only is such a design feasible, but also that the achieved link throughput in both directions is as good as the one obtained by using separate antennas for each radio, as long as we provide sufficient RF isolation between the multiplexed radios.

REFERENCES

• 1: AirJaldi Wireless Network. http://summit.airjaldi.com.
• 2: Akshaya E-Literacy Project. http://www.akshaya.net.
• 3: Aravind Eye Care System. http://www.aravind.org.
• 4: Eric Brewer , Michael Demmer , Bowei Du , Melissa Ho , Matthew Kam , Sergiu Nedevschi , Joyojeet Pal , Rabin Patra , Sonesh Surana , Kevin Fall, The Case for Technology in Developing Regions, Computer, v.38 n.6, p.25-38, June 2005 [doi>10.1109/MC.2005.204]
• 5: Kameswari Chebrolu , Bhaskaran Raman, FRACTEL: a fresh perspective on (rural) mesh networks, Proceedings of the 2007 workshop on Networked systems for developing regions, August 27-27, 2007, Kyoto, Japan [doi>10.1145/1326571.1326583]
• 6: S. M. Mishra, J. Hwang, D. Filippini, T. Du, R. Moazzami, and L. Subramanian. Economic Analysis of Networking Technologies for Rural Developing Regions. In WINE, December 2005.
• 7: Vishnu Navda , Anand Prabhu Subramanian , Kannan Dhanasekaran , Andreas Timm-Giel , Samir Das, MobiSteer: using steerable beam directional antenna for vehicular network access, Proceedings of the 5th international conference on Mobile systems, applications and services, June 11-13, 2007, San Juan, Puerto Rico [doi>10.1145/1247660.1247684]
• 8: R. Patra, S. Nedevschi, S. Surana, A. Sheth, L. Subramanian, and E. Brewer. WiLDNet: Design and Implementation of High Performance WiFi Based Long Distance Networks. In NSDI, 2007.
• 9: Rabin Patra , Sonesh Surana , Sergiu Nedevschi , Eric Brewer, Optimal scheduling and power control for tdma based point to multipoint wireless networks, Proceedings of the second ACM SIGCOMM workshop on Networked systems for developing regions, August 18-18, 2008, Seattle, WA, USA [doi>10.1145/1397705.1397708]
• 10: K. Paul, A. Varghese, S. Iyer, and B. R. A. Kumar. WiFiRe: Rural Area Broadband Access Using the WiFi PHY and a Multisector TDD MAC. New Directions in Networking Technologies in Emerging Economics, IEEE Communications Magazine, 2006.
• 11: Bhaskaran Raman , Kameswari Chebrolu, Design and evaluation of a new MAC protocol for long-distance 802.11 mesh networks, Proceedings of the 11th annual international conference on Mobile computing and networking, August 28-September 02, 2005, Cologne, Germany [doi>10.1145/1080829.1080847]
• 12: N. P. Reddy. The SRAWAN MAC Protocol to support Real-Time Services in Long Distance 802.11 Networks. Master's thesis, IIT Chennai, 2006.
• 13: Sonesh Surana , Rabin Patra , Sergiu Nedevschi , Manuel Ramos , Lakshminarayanan Subramanian , Yahel Ben-David , Eric Brewer, Beyond pilots: keeping rural wireless networks alive, Proceedings of the 5th USENIX Symposium on Networked Systems Design and Implementation, p.119-132, April 16-18, 2008, San Francisco, California

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:
Design, Performance

Keywords:
antenna combining, point-to-multipoint, rural wireless