The Research Of Power Allocation In Cooperation Communications

Relay-based cooperative communication technology has developed rapidly in recent years. The basic idea is that in the communication environments with several single-antenna users, the mobile users can share other users'antennas to send data collaboratively according to a certain way, so as to produce a virtual environment with multiple antennas, get spatial diversity gain, and improve the system's transmission performance. Power allocation is one of the key technologies in the relay-based cooperative communication. Due to power resource is limited, so how to use the power efficiently has attracted a great deal of attentions from various countries' scholars. The problem of relay selection exists in the relay-based cooperative communication. If all relays are involved in cooperative communication, the system will bear a huge burden in many aspects such as feedback and synchronization, therefore, selecting cooperative relay effectively plays an important role in the improvement of the system performance.This paper considered the problem of relay selection and power allocation scheme in two-way AF relay system. First it analyzed the non-selection relay power allocation scheme carefully in the non-parallel and parallel data transmission modes. Base on this scheme, it proposed the optimal subcarrier selection scheme in the non-parallel transmission mode, this scheme not only made the receiver of the system more simple in design, but also reduced the requirements of the system in synchronization and peak-to-average power ratio. For parallel transmission mode, in order to reduce the influence of the transmission rate with several timeslots, the paper put forward the optimal single relay selection scheme in the parallel mode. Considering to the optimal single relay selection scheme exists the waste of subcarrier in the good state, this paper applied the optimal subcarrier selection to this scenario and put forward the optimal subcarrier selection scheme in the parallel transmission mode. Finally, the simulations in terms of the transmission rate showed that the two kinds of relay selection schemes in parallel mode are obviously better than the researched power allocation scheme without selection, which is the advantage of our schemes.