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We consider combined rate and power adaptations in direct-sequence code-division multiple-access communications, where the transmission power and the data rate are adapted relative to channel variations. We discuss the power gain that the combined adaptations provide over power adaptation. Then, we consider an integrated voice and data transmission system(More)
We propose new routing scheme, Cooperative Diversity-based Routing (CDR) which utilize the cooperative space diversity for power saving and for performance enhancement of wireless ad-hoc networks. The end-to-end performance of the proposed routing, CDR, is analyzed based on the Haenggi's link model. The improved performance is compared with Multi-hop Relay(More)
We consider a hybrid direct-sequence frequency-hopped (DS/FH) code division multiple access (CDMA) communication system, where the transmission power and data rate are adapted relative to the channel variation. Instead of random frequency hopping, hopping pattern is adaptively adjusted to obtain the maximum channel gain among available frequency slots.(More)
The effect of channel estimation errors and fading channel correlation on closed-loop transmit diversity (CTD) systems is investigated in frequency flat Rayleigh fading channels. A bit error rate expression for the CTD system is analytically derived as a function of the channel correlation coefficient, feedback delay, and fading index. Numerical results(More)
In this paper, power minimization for Poisson distributed random relay networks in Rayleigh fading channels is considered. We investigate two power allocation methods; one is a minimum power allocation (MPA) strategy and the other is an equal outage power allocation (EOPA) strategy. We analyze the total transmit power of two allocation methods under the(More)
In this paper, we consider a time-division multiple-access relay channel (MARC), in which two source nodes (SNs) transmit data with different data rate to a destination node (DN) with the help of a relay node (RN). To provide asymmetric data rates, we consider joint hierarchical 16QAM (HM 16QAM) and network coding. Simulations results show that the joint HM(More)