Research On Routing Protocol Based On Virtual MIMO In Wireless Sensor Networks

Wireless sensor network(WSN)is widely used in military,medical care and logistics management for its small size,low cost and low power consumption.It is composed of a large number of sensor nodes,but the nodes are powered by batteries with limited energy,and are generally deployed in harsh environments,so the battery cannot be replaced.Therefore,reducing the energy consumption of nodes and extending the lifetime are important to WSN research.Compared with homogeneous WSNs,heterogeneous WSNs are more flexible and are more in line with the reality.Appropriate routing algorithm can balance network energy consumption and improve network operation efficiency.Typical clustering routing protocols include low energy adaptive clustering hierarchy protocol(LEACH)and distributed energy-efficient clustering protocol(DEEC).The application of multi-input multi-output(MIMO)technology in routing protocols can obtain the space-time diversity gain,improve the channel capacity and maximize the utilization of resources.Aiming at the shortcomings of the existing WSN cooperative MIMO routing algorithm,this thesis studies the propagation characteristics of wireless signals in different environments and the advantages and disadvantages along with the application scope of different coding cooperative transmissions.Through mathematical proofs,we derive a proposition and two lemmas on the choice of cooperative single-hop or multi-hop modes,which gives a sufficient condition on cooperative multi-hop transmission.Finally,a DEEC adaptive cooperative routing algorithm based on energy heterogeneous WSN is proposed.The specific research content is as follows:1)In view of the wide application of WSN in the forestry,we study the transmission characteristics of wireless signals in the three environments such as forest,playground and Liriodendron.In the research,Zig Bee and Lo Ra wireless technologies are used to measure RSSI of the WSN under different antenna heights.According to the measured data and the channel propagation model,the attenuation coefficient of wireless signal propagation is fitted,which provides a theoretical basis for calculation of WSN energy consumption in different actual scenes.2)A WSN cooperative transmission system combining a typical multiple-input multiple-output(MIMO)technology—vertical layered space time code(VBLAST)is studied.Specifically,we describe the cooperation mechanism in detail,obtain the energy consumption ratio per bit of non-cooperative transmission and cooperative transmission,and deduce the expressions of transmission energy consumption and throughput.It also compares the system performance of LEACH combined with another classic MIMO technology—space-time block code(STBC)for WSN cooperative transmission.Through comparative analysis,the advantages and disadvantages and scope of application are obtained,which can provide reference and basis for the coding selection in cooperative routing.3)Based on the above research,in the energy heterogeneous WSN,an STBC coded DEEC adaptive cooperative routing algorithm is proposed.First,we give the proposition of cooperative single-hop or multi-hop mode selection,and prove the sufficient conditions for selecting multi-hop cooperative transmission;then,based on the sufficient conditions,we propose two lemmas as the distance threshold for the mode selection in the routing algorithm.According to these two lemmas,an adaptive cooperative routing algorithm combining DEEC in energy heterogeneous WSN is proposed.Based on the path loss index obtained from the experimental analysis in the first part above,combined with the energy consumption expressions,the two lemmas on mode selection are re-derived,and the two lemmas in general on mode selection are obtained.On this basis,performances of the proposed adaptive routing algorithm are tested in the ideal and the actual environment.Simulations show that,the proposed routing algorithm outperforms the benchmark schemes and can effectively reduce the network energy consumption and prolong the network lifetime.The application of adaptive routing algorithm in WSN can increase network flexibility.The focus of this thesis is on the adaptation of single-hop and multi-hop cooperation modes.In the future,we can also study the adaptation of multiple transmission modes to realize energy-efficient WSN.