Frequency domain channel measurements for wireless localization - practical considerations and effects of the measurement

The measurement of wireless channels is a crucial step for realistic simulations of networks. Plenty of measurements and channel models have been published for communication applications. However, channel measurements for wireless localization focus on specific aspects like the exact representation of antenna distances by the path delays. Unfortunately, there are certain properties and effects of the measurement that complicate the correct extraction of the channel impulse response. Therefore, this paper deals with the well known method of frequency domain channel measurements with a focus on localization applications. We will give an overview over the general measurement system which is based on a vector network analyzer (VNA). The measurement parameters and methods necessary for the reconstruction of the impulse response with precise distance information will be presented. We will also reveal possible error sources of the measurement. For example, reflections and crosstalk result in several limitations of the impulse response. The influence of interfering networks and other man made distortions during the measurement will be estimated. We will show how the VNA based channel measurement can effectively be used for realistic simulations of localization algorithms.