The cooperative communications show the great advantage on the relays that can share their resource to improve the decoding of destination. However, relays are considered not reliable due to a low signal strength or high interference, where the relays only transmit a fraction of the message. To solve this problem, in this work, the block processing are implemented in partial transmission (PT), which allows the relays to divide the source information into small blocks and calculate the reliability information of the message. In the destination, a correlated spatial reception scheme is designed to jointly decode several information copies. The motivation is that even if each relay may not decode the message completely correct, the relay can still improve the decoding of destination. This paper formulates the end-to-end outage probability of PT with unreliable relays. Simulation shows the proposed strategy can provide a significant improvement over the conventional strategies with unreliable relays.

Topology control is an efficient strategy to improve robustness and connectivity in networks. The mobility of nodes, the limited node degree and fragile links in optical wireless communication (OWC) networks make topology control a great challenge. In this paper, the node-block (NB) based topology control algorithm is proposed. Firstly, the proposed algorithm uses the prediction of the contact time between the nodes as the link weight to form a stable tree structure that is called node-block; secondly, the quantized value based on Gamma-Gamma channel model is used as the link weight between node-blocks, and then a multi-link connection is established between any two node-blocks; finally, a connected graph is formed. The performance evaluation parameters, such as topological stability, algebraic connectivity and average node degree are discussed, and their expressions are given. The related simulations are carried out, and comparing with MST algorithm are also made. The results show that our proposed topology control algorithm can ensure the connectivity and stability of the OWC networks, meanwhile, the available node degree are reserved is applied to the large-scale networks.