Uncoordinated Beamforming for Cognitive Networks

Performance evaluation of uncoordinated beamforming over cognitive radio network

“…The method employed in this section is as proposed in [9], where we find the transmit and receive weight by performing an exhaustive search in and . Here, we define and as a set of basis vectors which spans the null space of , * and , , respectively, where the cardinality of is given as − 1 and is given as − 1.…”

“…This is due to the fact that, in gradient algorithm, a thorough search in the null space of , * and , satisfying the zero interference condition has been performed in order to find the optimum weight, whereas in discrete search, the weight is obtained without carried out the search over the entire null space of From both figures, it is verified that the SINR performance of secondary user are always outperform the SINR at the primary user. This shows that in order to maximize the total system sum rate, the fairness issue in both primary and cognitive link has not been taken into consideration in [9]. Therefore, in our future work, we aim to propose a method to improve the SINR performance of primary user, thus the SINR performance in primary and cognitive link is both maximized and fair.…”

“…In [9], the authors proposed beamforming vectors designs such that the interference caused by the cognitive transmitter to the primary receiver and the interference caused by the primary transmitter to the cognitive receiver is totally nullified while maximizing the rate of both the primary and secondary link. Although the authors claimed that the proposed methods maximize the achievable rates of both links, however, the fairness in the signal-to-interference-plus-noise ratio (SINR) performance is still remain a question.…”

“…In this network also, we examined an uncoordinated beamforming technique to completely remove the cross interference between the primary and secondary users using multiple antennas. Two methods that have been proposed in [9] has been considered, where we evaluate the fairness performance of using those methods in maximizing the individual SINR of both primary and secondary users and its achievable sum rate.…”

LTE-A femto-cell interference mitigation with MuSiC DOA estimation and null steering in an actual indoor environment

“…However, with the recent advances in multi-antenna technologies space and angle dimensions can be exploited. An useful approach is to use beamforming at the femtocell transmitter in order to maximize the secondary system performance while the interference on the primary system receiver is minimized [7], [8]. This operation is named as Cognitive Beamforming (CB) and requires complex numerical solutions and the knowledge of all propagation channels that is impracticable in actual systems.…”