Guftaar Ahmad Sardar Sidhu

A Joint Resource Allocation Scheme for Multiuser Two-Way Relay Networks

In this letter, we study the problem of resource allocation in amplify-and-forward (AF) based multiuser two-way relay network that is operated under orthogonal frequency division multiple access (OFDMA) modulation. We formulate an end-to-end throughput maximization problem subject to limited power constraint at individual user and relay. The optimization targets to find the best sub-carrier allocation to each user, sub-carrier pairing at the relay, as well as the power allocation at all nodes, which turns out to be a mixed integer programming problem. We then derive an asymptotically optimal solution through Lagrange dual decomposition approach and further design a suboptimal algorithm to trade the performance for computational complexity. Finally, simulation results are provided to demonstrate the performance gain of the proposed algorithms.

Resource Allocation in Relay-Aided OFDM Cognitive Radio Networks

In this paper, we investigate the resource allocation problem in a single-user relay-aided cognitive radio (CR) underlay network. Both the CR network and the primary network operate under the orthogonal frequency-division multiplexing (OFDM) scheme. Different from the conventional resource allocation problem, the relay node here is capable of performing subcarrier permutation over two hops such that the signal received over a particular subcarrier is forwarded via a different subcarrier. The objective is to maximize the throughput of the CR network subject to a limited power budget at the secondary source and the relay node and to interference constraints at the primary receiver. Optimization is performed under a unified framework where power allocation at the source node, power allocation at the relay node, and subcarrier pairing at the two hops are jointly optimized. The joint resource-allocation scheme yields an asymptotically optimal solution. We further design a suboptimal algorithm that sacrifices little on performance but could significantly reduce computational complexity. Finally, numerical examples are provided to corroborate the proposed studies.

Efficient and Autonomous Energy Management Techniques for the Future Smart Homes

Smart grid with latest technologies provides solid foundation for the implementation of energy management systems at home premises. This paper proposes an autonomous energy management-based cost reduction solution for peak load times using a home energy management system (HEMS). Within a home environment, both the real time and the schedulable appliances are connected with smart meter through HEMS. We formulate an optimization problem under various practical constraints, which is shown to be a mixed integer programming problem that can be solved through a step-wise approach. A novel scheme based on Dijkstra algorithm is proposed, which results in the similar performance to that of the proposed optimal scheme while exhibiting much lower complexity. To further save the computational efforts, a low complexity scheme is also proposed, which produces considerably better results than the non-optimized scheme with the same complexity yet. Simulation results are presented at show the performance and complexity comparison of different proposed solutions and the existing methods.

Resource Allocation for Relay Aided Uplink Multiuser OFDMA System

In this paper, we study the resource allocation problem in relay aided two-hop uplink multi-user transmission with a single relay node and a single destination node. The orthogonal frequency division multiple access (OFDMA) is adopted as the main transmission modulation. We investigate the problems of subcarrier allocation, subcarrier coupling, and power allocation. The optimization is formulated as maximizing the capacity under constraints of limited number of available subcarriers and a limited amount of power for each source node. A low complexity, suboptimal solution is presented to solve the problem. Simulation results are presented to evaluate the performance of the proposed algorithm.

Joint subcarrier pairing and power loading in relay aided cognitive radio networks

This paper investigates the resource allocation problem in a relay-aided cognitive radio (CR) system under the orthogonal frequency division multiplexing (OFDM) transmission. Different from the conventional CR resource allocation problem, the relay node here is capable of performing subcarrier permutation over two hops such that the signal received over a particular subcarrier is forwarded on a different subcarrier. The objective is to maximize the throughput of the CR network subject to a limited power budget at the secondary source and relay node, as well as the interference constraints at the primary receiver. The optimization is performed under a unified framework where the power allocation at the source node, power allocation at the relay node, and subcarrier pairing at the two hops are optimized jointly. Finally, numerical examples are provided to corroborate the proposed studies.

A Joint Resource Allocation Scheme for Relay Aided Uplink Multi-User OFDMA System

In this paper, we study the problem of resource allocation in orthogonal frequency division multiple access (OFDMA) based multi-user dual-hop uplink transmission where a single relay station is deployed between the mobile users and the base station which operates under amplify-and-forward (AF) relaying mode. The optimization targets to maximize the overall system throughput through joint optimization of sub-carrier allocation, sub-carrier pairing, and the power allocation, subject to individual power constraint at each node. The optimization results in mixed integer programming problem and a near optimal solution is obtained through dual decomposition approach. Further, we develop a suboptimal scheme to trade the performance for lower complexity. Finally, numerical examples are provided to demonstrate the performance gain of the proposed schemes.

Lifetime maximization in multihop mixed AF-DF relay networks

In this paper, we study the problem of the lifetime maximization in a new type of multi-hop relay network where the amplify-and-forward (AF) and the decode-and-forward (DF) relay nodes are alternatingly cascaded. In order to cope with the general frequency selective fading channel, the orthogonal frequency division multiplexing (OFDM) modulation is adopted over each hop. We formulate the optimization problem as maximizing the network lifetime subject to the constraint of minimum end-to-end rate requirement, while each relay node is constrained to its limited battery energy as well as the maximum power supply. Under certain assumptions, we transform the original problem into the standard convex optimization problem and solve it from the dual decomposition technique. Simulation results are provided to corroborate the proposed strategy.

Multiuser MIMO-OFDMA with Different QoS Using a Prioritized Channel Adaptive Technique

In this paper, an orthogonal multiple access scheme is considered for different users with different quality of ser- vice (QoS) requirements. Therefore, the users are multiplexed using orthogonal frequency division multiple access (OFDMA) transmission. A multiple-input multiple-output (MIMO) antenna system is considered between the base-station (BS) and the existing mobile sets (MSs). In order to realize different QoS, the transmission bit-rates and powers are adapted to the various channel conditions with different margin separations. In here, we proposed two different subcarrier sorting schemes in order to exploit the multiuser diversity and to enhance the performance in case of channel uncertainties. Accordingly, our simulations examine the performance of the downlink (broadcast) channel adaptation for different channel conditions assuming a single cell scenario. Index Terms—MIMO, OFDMA, adaptive modulation, power allocation, limited feedback, QoS, multiuser diversity

Optimizing Combined Emission Economic Dispatch for Solar Integrated Power Systems

The dispatch of power at minimum operational cost of thermal energy sources has been a significant part of research since decades. Recently, with increasing interests in renewable energy resources, the optimal economic dispatch has become a challenging issue. This paper presents combined emission economic dispatch model for a solar photo voltaic integrated power system with multiple solar and thermal generating plants. We formulate mixed integer binary programming problem subject to various practical constraints. A decomposition framework is proposed where the original problem is split into two sub-problems. Particle swarm optimization, Newton-Raphson method, and binary integer programming techniques are exploited to find the joint optimization solution. The proposed model is tested on the IEEE 30 bus system. The simulation results demonstrate the effectiveness of the proposed model.

A general framework for optimizing AF based multi-relay OFDM systems

In this paper, we study the joint resource allocation problem in multi-carrier multi-relay aided dual hop single-user communication. We adopt orthogonal frequency division multiplexing (OFDM) as the transmission modulation and consider amplify-and-forward (AF) relaying scheme. The optimization is performed over power allocation at source node, beamforming at relay nodes and subcarrier pairing at two hops, such that the overall system throughput is maximized under limited power budget at the source and relay nodes. The optimization is a mixed integer programming problem which is solved through dual decomposition approach. To further reduce the complexity, we propose a suboptimal algorithm which sacrifices very little on the performance. Finally, simulation results are provided to corroborate the proposed studies.