essary that dk dw/VK.Suppose the per-channel PDI and PFAI of the K-band detec- tor are defined as: PDI=PD/K (1A.6) PFAI = P FA/ K. (1A.7) The requirement then comes: (1A.8) Although the validity of (1A.8) cannot be readily established, recourse to Figure 1.2 or to numerical examples, shows that equality will not be obtained Appendix 1A. Conditions for Viable Multichannel Detector Performance and that the inequality [Q-1(PFA/K) - Q-1(PD/K)] > - (1A.9) must hold. [Example: With PD = 0.9, PFA = 10-6, = and I K = 10, (1A.9) becomes, specifically, 5.8 dB > 2.8 dB.] The conclusion, then, is that a K channel detector of the form postulated above requires a higher SIN than the simple single-channel wideband radiometer. A manifest reason for this is that the channels are not matched to the times when signal is present within them. This is a necessary criterion for any detector that is going to outperform the wideband radiometer. (In theory, the partial-band FBC meets this criterion and, as a result, its per- formance is generally superior.) Chapter Chapter 2 MULTIPLE ACCESS Spread-spectrum signals¹ examined in this book are designed to combat intentional jamming interference in radio channels. Thus, to any spread- spectrum transmitter/receiver pair that is communicating in a network of radios, other spread-spectrum signals can be collectively regarded as a jam- ming signal and, provided their numbers are not too large, each such link should be able to achieve reliable communication with this unintentional mutual interference. This chapter presents a somewhat tutorial discussion of the performance of spread-spectrum communication systems in some generic networks where there are several spread-spectrum signals of the same type occupying the same time and frequency. Specifically, we examine two basic questions con- cerning multiple access communications: 1. Point-to-Point: How well can a receiver detect and decode a spread-spec- trum signal from one radio transmitter when there is interference from several other spread-spect