 picocells and in-building cells, even these models are inadequate, and we need to build a more detailed model of the wire- less subscriber environment. We believe that urban ray-tracing models that sound like science fiction today will be used in a few years to plan high-density wireless service within dense high-rise workplaces. 47.8 The Signal Matrix A good summary of sector-to-sector interference is the signal matrix. In conventional reuse, it expresses the relationship between the serving signal and potential cochannel interferers. In CDMA it expresses the interference from nearby sectors that degrades CDMA capacity. The signal matrix is typically computed from propagation models, but it can be derived from system measurements. We put all the server groups across the top of the page and all the base station an- tenna faces along the left side to form a matrix structure. 12 In Table 47.1 we show a simple signal matrix for three cells, A, B, and C, in a row, shown in Fig. 47.8. The signal path gain from each base station to its own subscribers is -100 dB, on average. The direct neighbors enjoy about 15 dB less path gain, and the further reach from A to C has about 25 dB less than the serving signal. The columns represent communities of user terminals, so the first column is three sets of signal paths from three cells to subscribers being served by cell A. The rows represent the an- tenna faces, so the first row is the three sets of signal paths from all the user terminals to cell A. Another way of looking at this signal matrix is the columns represent the forward link and the rows represent the reverse link. That the A column has higher interfering path gain than the A row suggests that cell A has a tougher time on its forward link than on its reverse link. The forward direction has 1 dB more interference from cell B and 2 dB more from cell C. The asymmetry in the directions could be from elevation differences or different obstructions, but it appears in the signal matrix in any case. 12 This distinction betwe