Methodology and Preliminary Findings towards the Characterization and Evaluation of Non-Line-of-Sight (NLOS) Paths for Fixed Broadband Wireless Communications for Emergency and Disaster Response

Fixed broadband microwave communications are usually considered line-of-sight (LOS) technologies. Conventional wisdom holds that non-line-of-sight (NLOS) paths are of insufficient quality for broadband commercial deployments. However, it is possible that the only links available in an emergency deployment are NLOS paths. Since little work has been published regarding the usefulness of these channels, the proposed measurement campaign will be focused on characterizing these channels and evaluating their potential to carry digital data with a desired fidelity. Field measurements are expected to begin in April, 2003 and will include channel impulse response measurements as well as bit error rate (BER) tests. Preliminary simulations have been run that demonstrate the dependence of BER on the complex channel impulse response rather than on certain statistics of the power delay profile. Early indications are that BER degradations due to the amplitude variation of the channel frequency response can be related to the variance of the amplitudes across the frequency band of interest.