Research On Relay Selection For Considering The Characteristic Of Relay Nodes

Cooperative relay technique is an important wireless communication technology,which can bring spatial diversity and improve spectrum efficiency,link reliability,as well as the flexibility of network configuration,etc.with great potential for application.Relay selection can affect the performance of cooperative communication system directly,which makes relay selection attract a wide spread attention.General cooperative relay selections often pay attention to the signal to noise ratio(SNR)but neglect the other factors,such as the capacity of buffer,the battery supply at relay nodes and so on.The author hopes to further improve perfectly the performances of relay selection through paying more attentions to characteristic of relay nodes while designing the algorithm of relay selection.After investigation,the relay selection schemes to reduce the data's delay at nodes and prolong the life cycle of cooperation network are put forward.The specific contribution for this paper as follows:(1)Aiming at the problem that the data traffic will be delayed at relays and the delay requirement of it cannot be satisfied,a relay selection model with the consideration of the traffic delay is established in the two hop DF cooperative communication systems.On this basis,a new relay selection method in which both the channel conditions and the traffic delay at the relay are considered is proposed.The performances of the proposed method are also analyzed.First of all,the probability density function(PDF)of the traffic delay at the relay is derived.Thereafter,the analytical expressions of the average system capacity and outage probability are obtained.The simulation results are in accordance with the theory accurately and also verify that the proposed method can effectively reduce the average delay at relays while guaranteeing a considerable data rate.(2)Due to the fast energy consumption and even the reduction of the network lifetime caused by the frequent data forwarding for the battery supplied relays with high channel qualities,a novel relay selection method,considering the energy consumption of the battery,remain of battery and the channel conditions simultaneously,has been proposed in the cooperative scenario with only battery supplied relays.The signal to noise ratio(SNR)is weighted according to the ratio of energy consumption to transmit a symbol and remaining battery.Then the source or the relay of the relay link with maximum weighted SNR is chosen to transmit the data.On this basis,the performance of the proposed method is analyzed in terms of the average forwarding channel capacity and outage probability,the expressions of which have been derived.Finally,Simulation is done in the performances of the battery energy consumption,average forwarding channel capacity and outage probability.The simulation results match the analytical very well and these numerical results show that the proposed method is able to lower the energy consumption of the relays while guaranteeing the capacity and outage performances.