A Joint Rate Control and AMC Algorithm for Adaptive Transmission Systems

The traditional communication system is effectively designed for the worst-case channel state and it can not use the spectral efficiently over the time-varying multipath channel. In order to improve the spectral efficiency and ensure robust and spectrally-efficient transmission over the time-varying multipath channel,a joint rate control and adaptive modulation and coding ( AMC) algorithm for adaptive transmission systems is proposed in this paper. Firstly,the proposed algorithm can formulate a modulation and coding scheme ( MCS) switching table according to the offline simulation results and the target bit error rate ( BER) . Then,the optimal MCS is selected in MCS switching table according to the channel state information ( CSI) and then passes to the transmitter and receiver to implement. So the adaptive system which always uses the optimal MCS to transmit signals uses the spectral efficiently. The simulation results validate the proposed algorithm and show that under the premise of meeting the target BER,the adaptive system performing the proposed algorithm has a higher average spectral efficiency ( ASE) than that of the non-adaptive system.

LLR-AWARE SMART LINK-ADAPTIVE STRATEGY FOR DECODE-AND-FORWARD COOPERATIVE COMMUNICATION

Error propagation seriously degenerate the diversity order of Decode-and-Forward (DF) cooperative communication. To address this problem, a novel Log Likelihood Ratio (LLR)-based Link Adaptive Relaying (LAR) is proposed to promote adaption accuracy at relay. The instantaneous Bit Error Probability (BEP) is calculated according to the LLR of the received signals firstly, then based on it, the equivalent Signal-to-Noise Ratio (SNR) is employed to operate dynamic power scaling by relay. It is theoretically proved that the full diversity order can be attained by the scheme. Besides, the power sensitivity is also analyzed. Simulation results show that the proposed scheme outperform the conventional LAR and can achieve full diversity order. Moreover, its strong adaptation to SNR fluctuation is validated.

Adaptive STBC-VBLAST transmission for mobile WiMAX

Multiple-input multiple-output（MIMO） technology can provide high data rate and substantial diversity.Space time block code（STBC） provides diversity gain and obtains signal of better quality even under bad channel conditions.However,it has no contribution to system average throughput.Vertical-bell laboratory layered space-time（VBLAST） improves peak data rate but leads to higher packet error rate（PER） at cell edge when the channel condition is poor.To get both higher system average throughput and cell edge throughput,an adaptive STBC-VBLAST transmission for downlink mobile WiMAX system is proposed and analyzed through system-level simulation in this article.The proposed approach compares the effective capacity of two candidate MIMO modes（STBC or VBLAST） and reports its decision to the base station with only one extra signaling bit.The simulation results show that the proposed approach can attain a balance between STBC and VBLAST.Besides,the cell throughput approximates that of pure VBLAST and the cell edge throughput is close to that of pure STBC.