Dual QoS driven power allocation in MIMO cognitive network with limited feedback

In this paper, we consider the adaptive power allocation in the MIMO cognitive network with limited feedback. It is well known that, with the view of guaranteeing the link quality of primary receiver (PRx), the transmit power of second transmitter (STx) is strictly constrained, resulting in that it is difficult to provides QoS guarantee to second receiver (SRx) in the fading channel. This paper focuses on searching a feasible scheme to satisfy the QoS of PRx and SRx currently. First, we prove that the capacity of SRx can be obviously improved without adding interference to PRx by exploiting the spatial degrees of freedom of MIMO. Then, in order to making use of the benefit of MIMO, joint maximum ratio transmission (MRT) and maximum ratio combination (MRC) with finite rate channel information feedback, a way to adapt the signal to the instantaneous channel condition, is adopted. The relationship of QoS provisioning and feedback amount is researched so as to meet the performance requirements with the least feedback bits. Next, based on the above MIMO setting, an adaptive power allocation strategy is proposed to maximize the average capacity of SRx while satisfy the dual QoS requirements. Finally, numerical results reconfirms the effectiveness of the proposed adaptive strategy.