| The increasing density and data rate of unlicensed band wireless devices has led to significant inter- and intra-radio interference problems. Multiple competing standards such as the IEEE 802.11b/g, Bluetooth and ZigBee, all of which operate in the 2.4 GHz ISM band, can interfere with each other when used in typical indoor environments, potentially causing significant performance degradation. This thesis aims to characterize different types of heterogeneous interference in the 2.4 GHz unlicensed band and develop techniques to diagnose interference related problems using passive monitoring. The first part of the thesis presents detailed experimental results (using the ORBIT radio grid testbed) to quantify the effects of such interference in representative small office and home (SOHO) environment. In particular, different topologies, traffic loads and number of interfering devices are emulated to show the impact of multi-radio interference and to characterize each kind of interference. The second part of the thesis describes a cross-layer, multi-radio interference diagnosis framework (called "spectrum MRI") which aims to classify and diagnose multi-radio interference problems using heuristic and model-based methods. Validation experiments show that broad auto-classification of multi-radio interference in terms of congestion, slow links, inter AP interference and Bluetooth interference is possible using heuristic algorithms and passive monitoring. |
