Physical layer security has been recently recognized as a promising new design paradigm to provide security in wireless networks in addition to the existing conventional cryptographic methods, where physical layer dynamics of fading channels are exploited to establish secured wireless links. In this project, we will develop different transmission strategies for secure transmission in wireless communications. Specifically, low complexity based transceiver designs will be focused based on convex optimization techniques with and without global channel state information. However, the performance of these transceiver designs is influenced by channel conditions between the legitimate user and eavesdropper channels. In order to further improve the performance of the secure communications, relay nodes can be incorporated into the network to relay the secret information between the legitimate terminals. For this relay assisted secrecy communication, a joint transmitter-relay based design will be investigated to enhance the achievable secrecy rates.