Primary Communication Network Research Articles

Proportional Fairness in Cognitive Wireless Powered Communication Networks

In this letter, we consider a cognitive wireless powered communication network (CWPCN), with a secondary wireless powered communication network (WPCN) that has cognitive ability to coexist with a primary communication network. To tackle the unfairness resource allocation issue in CWPCN, we extend proportional fair scheduler to this category of network. By utilizing the time division-based “harvest-then-transmit” protocol, we establish an optimization problem for optimal time slot allocation, which maximizes the bandwidth utility function for proportional fairness, under the constraints of time and interference. To solve this problem, an algorithm is proposed to find a tradeoff between fairness and throughput. Simulation results confirm the positive effect on the promotion of fairness metric.

Transmit Precoding in Underlay MIMO Cognitive Radio With Unavailable or Imperfect Knowledge of Primary Interference Channel

This paper addresses the problem of precoder design that maximizes the throughput of a secondary user (SU) in an underlay multiple-input multiple-output cognitive radio network, where the channel state information (CSI) from the SU to the primary user (PU) is unavailable or inaccurate. The design maintains the quality of service for the PU through an interference amount measure in terms of the interference temperature or the leakage rate. For the case of unknown CSI, we propose an iterative adaptation algorithm by exploiting the side information in the primary communication network. For the case of imperfect CSI, we model the amount of uncertainty to be within a convex set defined by the Schatten norm and apply the maximin optimization to obtain the solution. To complete this paper, we derive the conditions on the CSI uncertainty radius under which the robust design with imperfect CSI would not perform better than the one with unknown CSI, when using the interference temperature metric. The proposed techniques are supported by numerical simulations.

Optimal power allocation for fading channels in cognitive radio networks: Ergodic capacity and outage capacity

A cognitive radio network (CRN) is formed by either allowing the secondary users (SUs) in a secondary communication network (SCN) to opportunistically operate in the frequency bands originally allocated to a primary communication network (PCN) or by allowing SCN to coexist with the primary users (PUs) in PCN as long as the interference caused by SCN to each PU is properly regulated. In this paper, we consider the latter case, known as spectrum sharing, and study the optimal power allocation strategies to achieve the ergodic capacity and the outage capacity of the SU fading channel under different types of power constraints and fading channel models. In particular, besides the interference power constraint at PU, the transmit power constraint of SU is also considered. Since the transmit power and the interference power can be limited either by a peak or an average constraint, various combinations of power constraints are studied. It is shown that there is a capacity gain for SU under the average over the peak transmit/interference power constraint. It is also shown that fading for the channel between SU transmitter and PU receiver is usually a beneficial factor for enhancing the SU channel capacities.