Interference-Assisted Wireless Energy Harvesting in Cognitive Relay Network with Multiple Primary Transceivers

We consider a spectrum sharing scenario, where a secondary network coexists with a primary network of multiple transceivers. The secondary network consists of an energy-constrained decode-and-forward secondary relay which assists the communication between a secondary transmitter and a destination in the presence of the interference from multiple primary transmitters. The secondary relay harvests energy from the received radio-frequency signals, which include the information signal from the secondary transmitter and the primary interference. The harvested energy is then used to decode the secondary information and forward it to the secondary destination. At the relay, we adopt a time switching policy due to its simplicity that switches between the energy harvesting and information decoding over time. Specifically, we derive a closed-form expression for the secondary outage probability under the primary outage constraint and the peak power constraint at both secondary transmitter and relay. In addition, we investigate the effect of the number of primary transceivers on the optimal energy harvesting duration that minimizes the secondary outage probability. By utilizing the primary interference as a useful energy source in the energy harvesting phase, the secondary network achieves a better outage performance.Comment: 6 pages, 5 figures, To be presented at IEEE GLOBECOM 201

How to Understand LMMSE Transceiver Design for MIMO Systems From Quadratic Matrix Programming

In this paper, a unified linear minimum mean-square-error (LMMSE) transceiver design framework is investigated, which is suitable for a wide range of wireless systems. The unified design is based on an elegant and powerful mathematical programming technology termed as quadratic matrix programming (QMP). Based on QMP it can be observed that for different wireless systems, there are certain common characteristics which can be exploited to design LMMSE transceivers e.g., the quadratic forms. It is also discovered that evolving from a point-to-point MIMO system to various advanced wireless systems such as multi-cell coordinated systems, multi-user MIMO systems, MIMO cognitive radio systems, amplify-and-forward MIMO relaying systems and so on, the quadratic nature is always kept and the LMMSE transceiver designs can always be carried out via iteratively solving a number of QMP problems. A comprehensive framework on how to solve QMP problems is also given. The work presented in this paper is likely to be the first shoot for the transceiver design for the future ever-changing wireless systems.Comment: 31 pages, 4 figures, Accepted by IET Communication

Optimal resource sharing and spectrum leasing in energy efficient relay-assisted networks

Assuming a bidirectional relay assisted network, we first study the problem of optimal resource sharing between two transceiver pairs. One of the pairs, referred to as the primary pair, owns the spectral resources while the other pair, called the secondary pair, is considered to own the relay infrastructure. Assuming amplify-and-forward relaying scheme and aiming to establish a cooperation between the two networks, we study three different design problems in a single carrier scenario. In the first approach we maximize the smaller of the secondary transceiver rates subject to two separate constraints on the total powers consumed in the primary and the secondary networks while providing a minimum data rate to the primary pair. In the second approach, we replace the per network power constraint by a constraint on the average total power consumed in both networks. The third approach combines the two aforementioned methods to materialize spectrum leasing and sharing for the case when the primary network is active with a certain probability. Then we investigate two different design approaches to the multi-carrier scenario. The first approach relies on maximizing the secondary network average sum-rate subject to two spectral power masks for the two networks while providing a minimum sum-rate to the primary pair in a multi-relay scenario. In the second approach, we replace the spectral power mask for each network by a constraint on the total power consumed in that network. Different from the previous studies, we further investigate the resource allocation problem between several energy harvesting relay nodes such that a unidirectional communication link is established between a pair of users and the harvested energy is optimally allocated between the relays such that the overall throughput of the network is maximized. Assuming the availability of full knowledge of channel state information and that of the energy packets, we maximize the throughput of the network under two sets of constraints on the status of the battery. We then consider the problem of maximizing the average throughput of the system, for the case when only the statistics of the channels are available