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The transmission bit rate isR r ¼ r bT sT bbit=sec ð5:18Þwherer b ¼ input digital bit rate of the user (bit=sec).T s ¼ symbol (or frame) duration (sec).T b ¼ bit (or burst) duration (sec).It follows from this expression that if the rates R ri were selected to fallwithin the specified capacity region, the probabilities of errors z for l users tendto zero as the code block length, b, tends to infinity. Suffice to say that the sumof the rates tends to infinity with l users. In this instance, the cooperativeCDMA has a similar format as the FDMA and TDMA.Further comparison with FDMA and TDMA systems shows that if allthe rates in the CDMA are selected to be identical, than (5.17) reduces toR r < B log 21 þ lC iNð5:19Þwhich incidentally is identical to the constraint applied to TDMA and FDMA;note that N ¼ BN 0 and lC i is the total carrier power for all the users. Weconclude that if the aggregated rates are unequally selected, there exists a pointwhere the rates in the CDMA system exceed the capacity of FDMA andTDMA. This point will be fun for the reader to establish.5.3 SUMMARYThis chapter has discussed the techniques that permit several earth terminals orstations on the same network to exchange information via a nodal point thatthe satellite represents. These techniques are FDMA, TDMA, and CDMA:they exploit the geometric advantage created by the use of the satellite.Comparisons between the capacity of these multiple-access methods areexamined in terms of the information rate that each method achieves in anideal ‘‘additive white Gaussian noise’’ channel of finite bandwidth.z As defined in Chap. 3, Eq. (3.12).Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.