A new scheme to generate multiple weights used in opportunistic beamforming (OBF) system is proposed to deal with the performance degradation due to the fewer active users in the OBF system. In the proposed scheme, on...A new scheme to generate multiple weights used in opportunistic beamforming (OBF) system is proposed to deal with the performance degradation due to the fewer active users in the OBF system. In the proposed scheme, only two mini-slots are employed to create effective channels, while more channel candidates can be obtained via linearly combining the two effective channels obtained during the two mini-slots, thus increas-ing the multiuser diversity and the system throughputs. The simulation results verify the effectiveness of the proposed scheme.展开更多
In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming m...In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming multiple relays are available in the networks. We derive the moment generation function （MGF） of the received signal-to-noise ratio （SNR） at the destination, then obtain the exact closedform solution of OR and the approximate closed form expression of EGT-BF in terms of outage probability respectively through numerical inversion of Laplace transform. Simulation results are given to verify the correctness of theoretical analysis. We also compare the outage performance of OR and EGT-BF with oth- er transmission strategies and find that when decoding results of relays are available at the destination, OR achieves high performance and is the optimal scheme to achieve the tradeoff between performance and overheads. When relay decoding information is unachievable, the performance of OR degrades significant- ly, and the EGT-BF is a more preferred scheme.展开更多
We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper.The network consists of two multi-antenna source nodes and multiple distributed single-antenna rel...We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper.The network consists of two multi-antenna source nodes and multiple distributed single-antenna relays.Two opportunistic relaying schemes are proposed to efficiently utilize the antennas of the source nodes and the relay nodes.In the first scheme,the best relay is selected out by a max-min-max criterion before transmitting.After that,at each source,only the antenna with the largest channel gain between itself and the best relay is activated to transmit and receive signals with full power.In the second scheme,assisted by the best relay which is selected by the typical max-min criterion,both source nodes use all their antennas to exchange data,and match filter beamforming techniques are employed at both source nodes.Further analyses show that all schemes can achieve the full diversity order,and the conclusions are not only mathematically demonstrated but numerically illustrated.System performance comparisons are carried out by numerical methods in terms of rate sum and outage probability,respectively.The beamforming assisted scheme can be found to be superior to the antenna selection scheme when accurate Channel State Information (CSI) is available at the transmitters.Otherwise,the latter is very suitable.展开更多
文摘A new scheme to generate multiple weights used in opportunistic beamforming (OBF) system is proposed to deal with the performance degradation due to the fewer active users in the OBF system. In the proposed scheme, only two mini-slots are employed to create effective channels, while more channel candidates can be obtained via linearly combining the two effective channels obtained during the two mini-slots, thus increas-ing the multiuser diversity and the system throughputs. The simulation results verify the effectiveness of the proposed scheme.
基金Supported by the High Technology Research and Development Programme of China (No. 2007AA01Z2652009AA01Z247)the National Natural Science Foundation of China (No. 60972076)
文摘In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming multiple relays are available in the networks. We derive the moment generation function （MGF） of the received signal-to-noise ratio （SNR） at the destination, then obtain the exact closedform solution of OR and the approximate closed form expression of EGT-BF in terms of outage probability respectively through numerical inversion of Laplace transform. Simulation results are given to verify the correctness of theoretical analysis. We also compare the outage performance of OR and EGT-BF with oth- er transmission strategies and find that when decoding results of relays are available at the destination, OR achieves high performance and is the optimal scheme to achieve the tradeoff between performance and overheads. When relay decoding information is unachievable, the performance of OR degrades significant- ly, and the EGT-BF is a more preferred scheme.
基金supported by the National Natural Science Foundation of China under Grant No.60902092
文摘We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper.The network consists of two multi-antenna source nodes and multiple distributed single-antenna relays.Two opportunistic relaying schemes are proposed to efficiently utilize the antennas of the source nodes and the relay nodes.In the first scheme,the best relay is selected out by a max-min-max criterion before transmitting.After that,at each source,only the antenna with the largest channel gain between itself and the best relay is activated to transmit and receive signals with full power.In the second scheme,assisted by the best relay which is selected by the typical max-min criterion,both source nodes use all their antennas to exchange data,and match filter beamforming techniques are employed at both source nodes.Further analyses show that all schemes can achieve the full diversity order,and the conclusions are not only mathematically demonstrated but numerically illustrated.System performance comparisons are carried out by numerical methods in terms of rate sum and outage probability,respectively.The beamforming assisted scheme can be found to be superior to the antenna selection scheme when accurate Channel State Information (CSI) is available at the transmitters.Otherwise,the latter is very suitable.
