Measurement Based Investigation of Cooperative Relaying

In this paper we present measurements that involve two access points (APs) and two user terminals, each of which is equipped with 4 antennas, in an indoor office environment. The data allow for the simultaneous characterization of the multiple input-multiple output (MIMO) links from the APs to the user terminals and between the user terminals, and are, to the best of our knowledge, the first of their kind. We show that the links between user terminals are impaired by body shadowing, and have therefore much lower gains than the direct links to the APs. Moreover we investigate the statistics of the links, and their correlation. Based on these measurements, we investigate the performance of cooperative relaying in terms of rate improvement (for this analysis the data from only one AP are used). We show that a significant rate improvement can be achieved if the relaying node is free to set the power level at which it transmits, and if it is free to select which of its antennas is used to perform the relaying.