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This paper analyzes the outage probability for amplify-and-forward (AF) and decode-and-forward (DF) cooperative diversity systems with selective combining, for the case of a log-normal Nakagami faded desired signal and lognormal Rayleigh faded co-channel interferers. The outage probability is compared to that of a dual-receive antenna system also with selective combining. The results of this paper show that the proposed cooperative diversity systems can result in a lower outage probability than the corresponding dual-receive antenna system, but only when the relay is located in a particular region of the cell with respect to the destination mobile station location. Moreover, this paper shows that the AF cooperative diversity system is more robust than the DF cooperative diversity system for the composite channel condition and multiple interferers.which require a regenerating process. However, DF relays are nevertheless attractive, because the required signal processing can be performed with existing digital signal processing (DSP) blocks, while AF relays require expensive analog components and/or new hardware structures.In general, the performance of cooperative diversity schemes depends on the number of relays, the placement of relays, and the allocation of power. In addition, it is well known that cellular networks are interference limited rather than noise limited [1]. Hence, the cooperative diversity schemes can be vulnerable to co-channel interference (CCI), because the relays may all use the OUTAGE PROBABILITY FOR COOPERATIVE DIVERSITY 1565 × λth 0 exp{− (t 1 , t 2 )z}z mX−1 dzdt 1 dt 2 OUTAGE PROBABILITY FOR COOPERATIVE DIVERSITY 1567 Figure 4. Comparisons of the outage probability versus cochannel reuse factor on a shadowed Nakagami/shadowed Rayleigh channel, where ζ = 1 and Y = 3 dB.

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