Fig. 6

Outage probability versus the information transmission rate. The figure shows that the simulations on outage probability versus transmission rate of partial transmission (PT) and three conventional cooperative strategies, direction transmission (DT), selective decode-and-forward (SDF), and amplify-and-decode (AF), on the situations with one-relaying system and two-relaying system. To simulate the unreliable relays, the simulation parameters are set as follows: the number of information bits is 100,000; the transmit SNR of source is 20 dB; and all the channel states from source to relays, relays to destination, and source to destination are set the same, as 0.1. It can be seen in Fig. 6 that the outage probability gets higher as the information transmission rate increases. For the case of two-relaying system at low transmission rate, the PT performs worse than SDF and AF. Because the relays at low rate have high probability to decode the message or help the decoding at destination, they are reliable relays, while the relays in PT cannot transmit all the information sequence. As transmission rate gets higher, the relays become unreliable, where the partial transmission shows the great advantage. However, if transmission rate rises to some certain threshold, all the relays are useless, so that the two-relaying system performs worse than the one-relaying system and even worse than the direct transmission. However, PT can postpone this threshold