Robust power allocation designs for cognitive radio networks with cooperative relays

Abstract

In this paper, we develop robust power allocation schemes for cognitive radio networks (CRNs) that can operate in multiple bands with cooperative relays considering uncertainty among the channels of secondary user (SU) network and among the channels of SU transmitters to primary user (PU) receivers. Our objective is to formulate the robust design optimization problems taking into account the interference threshold in the PU band specified by the regulatory guidelines. To optimally allocate power with channel uncertainty, two robust algorithms are developed: (i) the worst-case optimization, where the interference constraints are satisfied for all channels contained in some bounded uncertainty regions, and (ii) the probabilistically constrained optimization, where interference constraints are satisfied with certain probabilities. We show that the formulated problems are convex, which can be efficiently solved. Numerical results show the effectiveness of the proposed schemes and the implications of ignoring the uncertainties among different channels when designing power allocation schemes for CRNs.

Filter‐and‐forward relaying in cognitive networks with blind channel estimation

“…In the literature, there are two types of such robust design, which corresponds to different ways that the channel error is modelled: stochastic and worst-case. These schemes were studied for CRNs with and without relays, assuming flat fading channels in [16][17][18][19][20][21][22]. In [22], robust beamforming is assumed for CRNs over flat fading channel and the channel error is modelled by a Gaussian random variable (RV).…”

Resource Allocation Under Channel Uncertainties for Relay-Aided Device-to-Device Communication Underlaying LTE-A Cellular Networks

“…For an OFDMA system, the resource allocation problem under channel uncertainty for a cognitive radio (CR) base station communicating with multiple CR mobile stations is considered in [22] for downlink communication. Two robust power control schemes are developed in [23] for a CR network with cooperative relays. In [24], a robust power control algorithm is proposed for a CR network to maximize the social utility defined as the network sum rate.…”

“…In the formulation of robust problem, we utilize a similar rate expression [i.e., equation (9)] as the one used in the nominal problem formulation. Although dealing with similar utility function (i.e., rate equation) for both nominal and robust problems is quite common in literature (e.g., in [22], [23], [25]), when perfect channel information is not available to receiver nodes, the rate obtained by (9) actually approximates the achievable rate 3 The solution to P2 is robust against uncertainties if and only if for any realization of g…”