Abstract—Cooperative transmission has been used toachieve diversity gain through partner to create multipleindependent fading channels. It has attracted lots of researchattention in recent years. An important questionin cooperative communication is power allocation. Giventhe same total power, how much should be allocated toself-information transmission and how much to relayinginformationtransmission. In this paper, we investigate powerallocation problem using amplify-and-forward (AF) protocolconsidering bit error rate (BER) performance of both usersand the work region of two cooperative users. We solvecooperative ratio, which is defined as the ratio of power usedfor cooperative transmission over the total power. We firstconsider both users applying the same ratio, and then extendto two-dimensional cooperative ratio problem. Our resultsshow that it is sufficient to allocate both users the same ratio.This value is specified by the user with a weaker channelgain to the destination, i.e., bottleneck link.With appropriateselection of the cooperative ratio, the BER performance ofboth users can be improved significantly. User fairness isalso considered in the analysis.
 
Index Terms—cooperative communication, amplify-andforward,power allocation, cooperative ratio, work region,BER

Cite: Lian Zhao, Zaiyi Liao, "Power Allocation for Amplify-and-Forward Cooperative Transmission Over Rayleigh-Fading Channels," Journal of Communications, vol. 3, no.3, July, pp.33-42, 2008.