Resource Allocation In OFDMA Systems Research Articles

Bat pack algorithm for dynamic resource allocation in OFDMA systems

Bat pack algorithm for dynamic resource allocation in OFDMA systems

Hysteretic Noisy Chaotic Neural Networks for Resource Allocation in OFDMA System.

This paper addresses two-stage resource allocation in the orthogonal frequency division multiplexing access system. In the subcarrier allocation stage, hysteretic noisy chaotic neural network (HNCNN) with a newly established energy function is proposed for subcarrier allocation to improve the optimization performance and reduce the computational complexity. Activation functions with both anticlockwise and clockwise hysteretic loops are applied to the HNCNN. A new energy function is established for an objective function, which can be calculated offline, resulting in a lower computational complexity in solving subcarrier allocation than the previous energy function. In the power allocation stage, the water-filling algorithm is employed to attain optimal power allocation. Simulation results show that the energy function established in this paper can decrease the runtimes of the neural networks, and that the HNCNN with both anticlockwise and clockwise hysteretic-loop activation functions can improve probabilities of feasible and optimal solutions at higher noises. The two-stage algorithm in this paper outperforms the previous algorithms in fairness, system throughput, and resource utilization.

A novel low complexity energy‐efficient resource allocation for OFDM systems

AbstractIn this paper, we study energy efficiency of an orthogonal frequency division multiplexing based system under power constraint and minimum rate requirement with system circuit power consideration. The optimal radio resource allocation is then formulated as an energy‐efficient maximisation where we propose a novel low complexity solution for obtaining the optimal solution. The solution consists of the optimal source transmission power and its distribution among subcarriers. In spite of the iterative solution with high computational complexity in previous works, we propose a quickly convergent low complexity scheme based on solving a nonlinear logarithmic equation. To evaluate the accuracy of the proposed method, we compared its accuracy through simulations with the optimal solution in systems with and without circuit power consideration. Simulation studies indicate that the proposed method provide accurate solutions in both low and high signal to noise ratio regimes. The simulation results also indicate using our proposed method results in a significant improvement in the computational complexity. Copyright © 2015 John Wiley & Sons, Ltd.

Content-aware resource allocation in OFDM systems for energy-efficient video transmission

Demand on multimedia content by consumers' handheld devices over wireless channels is on the increase. In view of the accelerated trend towards consumption of high quality video, power utilization by mobile devices is expected to excessively increase. Hence, it becomes equally important to advance more efficient power minimization techniques, in light of the short battery life in portable devices. However, power minimization algorithms that adopt consumers' perceptual quality of video have not received adequate research. This paper proposes a joint optimization of energy and quality requirements in a multiuser orthogonal frequencydivision multiplexing environment. A multi-objective optimization problem is formulated with the aim to identify bitrate allocations among users such that total power is minimized, and average quality is maximized. For this, a content-aware and energy-efficient resource allocation scheme (CaERAS) is proposed based on genetic and greedy algorithms. Simulation results show that CaERAS, as a lowcomplexity scheme, outperforms comparable methods in terms of efficiency and selectivity of suboptimal solutions. It is shown to acquire a suboptimal solution in as low as 0.0025 of the search space in previous methods. Also, a significant average saving of 85.66% in required energy is observed in broadcast transmission as opposed to unicast transmission.

Dynamic resource allocation in OFDM systems using DE and FRBS

Dynamic allocation of the resources for optimum utilization is one of the most important fields of study in engineering as well as other disciplines nowadays. In this process the available resources are allocated in such a way that these resources are maximally utilized to enhance the overall system throughput while satisfying certain constraints at the same time. In this paper a similar constrained optimization problem is focused for Orthogonal Frequency Division Multiplexing OFDM environment, in which the transmission parameters namely code rate, modulation scheme and power are adapted in such a way that overall system data rate is maximized with a constrained bit error rate and transmit power. This is a highly non-linear problem that cannot be solved by ordinary linear optimization techniques. A Fuzzy Rule Base System FRBS is proposed for adapting the code rate and modulation scheme while Differential Evolution is used for choosing the optimum power vector. The proposed scheme is compared with other schemes.

QoE and energy efficiency aware resource allocation for OFDM systems in group mobility environments

SUMMARYThe global information and communication technology industry is a fast growing contributor to the electrical energy consumption, especially for the base stations, accounting for a substantial amount of the energy use. Inherently, a resource allocation strategy including subchannels blackout would reduce energy consumption. In this paper, energy efficient resource allocation algorithms are addressed for the OFDM system in group mobility environments, suffering from high intercarrier interference. We first propose the subchannels blackout scheme to save energy implicitly without performance degradation by turning off certain subchannels when transmitting signals. Then, resource allocation scheme in combination with subchannels blackout scheme is developed, consisting of intergroup subchannels allocation and inner‐group subchannels blackout. Its advantage is twofold. (i) Energy consumption is reduced obviously; (ii) intercarrier interference is decreased and channel quality is enhanced simultaneously. However, the original transmit rate decreases with the decrease of active resources. We also prove under subchannels blackout scheme, achieved throughput and perceptual quality of experience (QoE) are quasiconcave in energy saving percentage, which reflects the number of blackout subchannels. We then present two energy efficient resource allocation algorithms. Both algorithms focus on the optimal solution by using an iteration method. The difference lies in the objective. One tries for energy consumption minimization above the satisfactory QoE level, but the other aims to maximize QoE perceived by users. Numerical results confirm the theoretical findings and demonstrate the promising energy‐saving capability with satisfying QoE of the proposed resource allocation schemes. Copyright © 2013 John Wiley & Sons, Ltd.

Using traffic asymmetry to enhance TCP performance

A wealth of recent work has gone into optimizing the performance of Transmission Control Protocol (TCP) on the downlink channel of wireless networks such as for example, honing its congestion awareness mechanism so that it is minimally affected by random wireless losses, and optimizing achieved fairness of the end-to-end TCP rates. Other work has gone into balancing the allocation of a shared resource between the downlink and uplink in order to optimize TCP performance. We build on such previous research by proposing a cross-layer algorithm for resource allocation in OFDMA systems aiming not only to achieve optimal throughput for competing TCP flows but also to allocate resources appropriately between the downlink and uplink. This is important due to the increasing number of Internet applications where the mobile terminal is the TCP sender (social networking, peer-to-peer, etc.). Therefore, our scheme makes use of the asymmetry in the traffic and by defining the boundary between downlink and uplink capacity dynamically, enhance the TCP performance. Through numerical investigations we show the performance of the proposed scheme in terms of achieved fairness to the receivers and efficient allocation of downlink to uplink ratios based on the TCP traffic.

A Strategy to Reduce the Signaling Requirements of CQI Feedback Schemes

Resource allocation in OFDMA systems involves the application of adaptive modulation/coding (AMC). AMC provides the flexibility to match the modulation-coding scheme (MCS) to each user's channel co...

Proportional Resource Allocation in OFDMA Systems Based on Weighted Normalized User's CSI

Proportional Resource Allocation in OFDMA Systems Based on Weighted Normalized User's CSI

Chunk-based resource allocation in OFDMA systems - part I: chunk allocation

In this paper, throughput performance analysis of the chunk-based subcarrier allocation is presented by considering the average bit-error-rate (BER) constraint over a chunk in downlink multiuser orthogonal frequency division multiplexing (OFDM) transmission. The outage probabilities per subcarrier are compared between the average BER-constraint based chunk allocation and the average signal-to-noise-ratio (SNR) based chunk allocation. The effects of system parameters, such as the number of users, the number of subcarriers per chunk, and the coherence bandwidth, are evaluated. The numerical results show that, when the chunk bandwidth is smaller than the coherence bandwidth, the average downlink throughput of the chunk-based subcarrier allocation is very close to that of the single-subcarrier-based allocation. When the number of users is small, the average throughput increases dramatically with increasing the number of users due to multiuser diversity, whereas when the number of users is large, the multiuser diversity gain is saturated. The effective throughput of the average BER-constraint based chunk allocation is higher than that of the average SNR based chunk allocation, especially when the number of users is large or when the ratio of the chunk bandwidth to the coherence bandwidth is large.

Downlink scheduling and resource allocation for OFDM systems

We consider scheduling and resource allocation for the downlink of a cellular OFDM system, with various practical considerations including integer tone allocations, different sub-channelization schemes, maximum SNR constraint per tone, and self-noise due to channel estimation errors and phase noise. During each time-slot a subset of users must be scheduled, and the available tones and transmission power must be allocated among them. Employing a gradient-based scheduling scheme presented in earlier papers reduces this to an optimization problem to be solved in each time-slot. Using a dual formulation, we give an optimal algorithm for this problem when multiple users can time-share each tone. We then give several low complexity heuristics that enforce integer tone allocations. Simulations are used to compare the performance of different algorithms.

Dynamic Resource Allocation in OFDMA Systems with Adjustable QoS

Traditional algorithms for dynamic OFDMA resource allocation have relatively deterministic system capacity and user fairness. Thus, in this letter, an efficient scheme is proposed to flexibly adjust quality-of-service for users, which is achieved by appropriately setting minimum data-rate of each user.

Resource Allocation for OFDMA System with Orthogonal Relay using Rateless Code

This paper considers the resource allocation problem in the wireless OFDMA system with a relay node. We consider orthogonal relay in which the relay node cannot transmit and receive simultaneously on the same frequency. As a result, the use of relay node may enhance or degrade the achievable transmission rate depending on the instantaneous channel states between the source and the relay, the relay and the destination as well as the source and the destination. Hence, it is very important to dynamically adjust the resources (subbands) allocated to the relay node so that the relay is used only at the right time according to the instantaneous channel states. Conventional approaches dynamically schedule the usage of the relay node in a centralized manner in which full knowledge of the channel states between any two nodes in the network is required. However, perfect knowledge of the channel states at various nodes is very difficult to obtain. In this paper, we shall propose a resource allocation algorithm, which iteratively allocates resource to the source and relay, and converge to the close-to-optimal allocation. Asymptotic achievable rate of the proposed algorithm is derived. We show that the system achieves significant improvement of the achievable rate compared to the point-to-point baseline system without relay as well as the baseline system with random subband allocation.

An Efficient Radio Resource Allocation Scheme for Minimum Outage Probability Using Cooperation in OFDMA Systems

Cooperation can increase the system performance by obtaining the spatial diversity. While most of the present works concentrate on the analysis of the cooperation based on the inter-user channel response and developing a scheme for higher cooperative diversity, in this paper, we focus on practical resource allocation in OFDMA systems. Since the user who uses the same center frequency can not receive the signal when transmitting, this constraint should be considered to apply the cooperation to OFDMA systems. In this paper, we propose the pair-based OFDMA frame structure that overcomes this constraint. Also in this frame structure to achieve the minimum outage probability of system, we select the best partner among the candidate neighbors and allocate the suitable subchannels to bandwidth requested users through a cooperative subchannel allocation (CSA) algorithm. In order to evaluate the proposed resource allocation scheme, we carry out simulations based on IEEE 802.16e. The simulation results show that our proposed algorithm offers smaller outage probability than one based on non-cooperative communications and we get the minimum outage probability when a threshold for selection of candidate neighbors is 10dB. We analyze that these results can be achieved by helping users located around the edge of the cell.

Traffic-diversity-based resource allocation for OFDMA system

A new concept-traffic diversity is proposed for resource allocation of orthogonal frequency division multiple access system. With traffic diversity, the transmitter designates different bit error rate (BER) level for each kind of traffic. The transmission data rate corresponds to the BER level. At the receiver, this separated traffic, which belong to the same user, will be aggregated. Simulation results show that traffic diversity can increase the throughput by 27%.

Dynamic resource allocation in OFDM systems: an overview of cross-layer optimization principles and techniques

Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e., policies) potentially provide significant performance gains for various systems. In this article we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by means of dynamic resource allocation. Two specific areas are treated separately: models and dynamic approaches for single transmitter/receiver pairs (i.e., a point-to-point communication scenario) as well as models and approaches for point-to-multipoint communication scenarios (e.g., the downlink of a wireless cell). This article provides basic knowledge in order to investigate future OFDM cross-layer-optimization issues