Interference map for 802.11 networks

ABSTRACT

The interference map of an 802.11 network is a collection of data structures that can help heuristics for routing, channel assignment and call admission in dense wireless networks. The map can be obtained from detailed measurements, which are time consuming and require network down time. We explore methods and models to produce the interference map with a reduced number of measurements, by identifying interference properties that help to extrapolate complex measurements from simple measurements. Actual interference in an 802.11a testbed is shown to follow certain regularities - it is linear with respect to packet rate of the source, packet rate of the interferer, and shows independence among interferers. When multiple cards are available, they behave differently, and even different channels of the same card have different performance. We find that while current methods of gathering the interference map may be appropriate for characterizing interference in one card networks, they are unscalable for multiple card networks when considering: 802.11 characteristics (card and channel asymmetries, time variation), required downtime, and complexity of the measurement procedure.

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INDEX TERMS

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

Additional Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.3 Network Operations
          Subjects: Network monitoring

General Terms:
Experimentation, Measurement

Keywords:
802.11, interference, measurement, model