In this letter, we consider a cooperation system with multiple untrusted relays (URs). To keep the transmitted information confidential, we obtain joint channel characteristics (JCCs) through combining the channels from the source to the destination. Then, in the null space of the JCCs, jammers construct artificial noise to confuse URs when the source node broadcasts its data. Through a distributed implementation algorithm, the weight of each node can be obtained from its own channel state information. Simulation results show that high‐level security of the system can be achieved when internal and external eavesdroppers coexist.

Abstract. This paper studies on the problem that the unreasonable choice of clustered routing protocol cluster head of energy heterogeneous WSN and the overload of some cluster head node which are far away from the base station in remote communication. And an improved clustering routing protocol based on energy and density for heterogeneous wireless sensor networks is proposed. Firstly, the optimal number of cluster head is got according to the network energy consumption model, and the node density factor is modified. Then, the new threshold is established by considering the residual energy of the node, the node density and the distance from the node to the BS. The cluster head communicates with the BS by using a single hop and a hybrid way through a relay node to reduce the cluster head load of the remote base station. Finally, the simulation results based on OMNet++ and Matlab show that the improved protocol has better performance in terms of network lifetime and network energy consumption compared with existing protocols.