On the rate-equivocation region of parallel relay eavesdropper channels

We consider a four terminal parallel relay-eavesdropper channel which consists of multiple independent relay-eavesdropper channels as subchannels. For the discrete memoryless case, we establish inner and outer bounds on the rate equivocation region. For each subchannel, secure transmission is obtained through one of two coding schemes at the relay: decoding-and-forwarding the source message or confusing the eavesdropper through noise injection. The inner bound allows relay mode selection. We then apply our results to study the fading Gaussian relay-eavesdropper channel. In this case, we focus on perfectly secure transmission. We establish a lower bound on the perfect secrecy rate. Furthermore, considering individual sum power constraints at source and relay, we study power adjustment among the independent subchannels. We illustrate the results through some numerical examples.