Cross-layer design for single-cell OFDMA systems with heterogeneous QoS and partial CSIT

Abstract— This paper proposes a novel cross-layer scheduling scheme for a single-cell orthogonal frequency division multiple access (OFDMA) wireless system with partial channel state information (CSI) at transmitter (CSIT) and heterogeneous user delay requirements. Previous research efforts on OFDMA resource allocation are typically based on the availability of perfect CSI or imperfect CSI but with small error variance. Either case consists to typify a non tangible system as the potential facts of channel feedback delay or large channel estimation errors have not been considered. Thus, to attain a more realistic resolution our cross-layer design determines optimal subcarrier and power allocation policies based on partial CSIT and individual user’s quality of service (QoS) requirements. The simulation results show that the proposed cross-layer scheduler can maximize the system’s throughput and at the same time satisfy heterogeneous delay requirements of various users with significant low power consumption

A selective delayed channel access (SDCA) for the high-throughput IEEE 802.11n

Abstract— In this paper we investigate the potential benefits of a selective delayed channel access algorithm (SDCA) for the future IEEE 802.11n based high-throughput networks. The proposed solution aims to resolve the poor channel utilization and the low efficiency that EDCA’s high priority stations adhere due to shorter waiting times and consequently to the network’s degrading overall end performance. The algorithm functions at the MAC level where it delays the packets from being transmitted by postponing the channel access request, based on their traffic characteristics. As a result, the flow’s average aggregate size increases and consequently so is the channel efficiency. However, in some situations we notice that further deferring has a negative impact with TCP applications, thus we further introduce a traffic awareness feature that allows the algorithm to distinguish which flows are using the TCP protocol and override any additional MAC delay. We validate through various simulations that SDCA improves throughput significantly and maximizes channel utilization

Energy efficient green wireless communication systems with imperfect CSI and data outage

Modern applications involve green communication technologies motivating well optimisation in the power–limited regime. In comparison to most of existing related work that assumes perfect channel state information (CSI) is always available, which is unfortunately not true in reality, this work focuses on an optimal energy efficient solution for resource allocation in multiuser orthogonal frequency division multiple access (OFDMA) networks in the presence of imperfect CSI and data outage conditions. Particularly, in view that wireless channel conditions, circuit power consumptions and users’ quality–of–service (QoS) requirements are heterogeneous in nature, we enable attractive tuning options by letting energy efficiency optimisation objective to assign weights to each allocation link. Also, we interpret effects of data outage due to imperfect CSI using a profound insight on the monotonicity of noncentral chi-squared inverse distribution function, which reveals that our design complies with expected physics and mechanics of conventional energy efficiency approach and that it can be successfully degenerated to the energy efficiency model with perfect CSI. Furthermore, we formulate a mixed combinatorial problem towards maximising the energy efficiency subject to a minimum QoS requirement, channel interference and transmitting power constraints. The problem is transformed into an equivalent quasiconcave problem with respect to power, and concave problem with respect to the subcarrier indexing coefficients using the concept of subcarrier time–sharing. We optimise through a simple and versatile methodology, which uses standard–Lagrangian optimisation technique to obtain joint dynamic subcarrier and adaptive power allocations by means of final formulas. We also examine key properties of the introduced optimal solution in terms of implementation convergence and complexity, level of optimality, and impact of imperfect CSI coefficients and circuit power on network performance. The simulation results demonstrate the effectiveness of our allocation scheme for achieving higher energy efficiency performance with the guaranteed QoS support and lower complexity than existing approaches especially when perfect CSI is not available

Enabling radioprotection capabilities in next generation wireless communication systems:An ecological green approach

In future fifth-generation and beyond radio systems, access points equipped with massive antennas will be deployed to support the increased communication demands. As a result, radio environments will become more dense and users will be exposed to higher electromagnetic field (EMF) radiation from wireless devices than today. This paper proposes to take preemptive action toward protecting the public health from potential EMF-related ill effects by examining radiation-aware solutions for future green wireless communication systems from the radio resource scheduling perspective. Our efforts focus on correlating the transmit power levels of the wireless system with the operands used to express the EMF dosimetry metrics known as maximum permissible exposure and specific absorption rate. In addition, we formulate power minimization problems subject to the maximum permissible exposure and specific absorption rate safety standards, and the individual user quality-of-service demands to derive convex optimization-based solution of dynamic subcarrier allocation and adaptive power management. The simulation results confirm that our green solution reduces significantly the user exposure to radiation, while providing the required quality of service. We expect that our findings can kick off new research directions for controlling the public exposure to radiation from wireless devices in dense networks toward safer fifth-generation communication systems. © 2018 John Wiley & Sons, Ltd

Sum-Rate Maximization Based Relay Selection for Cooperative NOMA over Nakagami-m Fading

This paper proposes a new sum-rate maximization based relay selection (RS) scheme for cooperative non-orthogonal multiple access (NOMA) networks over Nakagami-$m$ fading, where one base station communicates with two mobile users by means of multiple relays. The outage probability of the proposed scheme is derived in a closed-form expression, and the diversity order is also obtained. Simulation results are shown to compare the outage performance of the proposed scheme with that of the existing RS schemes

Stochastic Asymmetric Blotto Game Approach for Wireless Resource Allocation Strategies

The development of modellings and analytical tools to structurise and study the allocation of resources through noble user competitions become essential, especially considering the increased degree of heterogeneity in application and service demands that will be cornerstone in future communication systems. Stochastic asymmetric Blotto games appear promising to modelling such problems, and devising their Nash equilibrium (NE) strategies by anticipating the potential outcomes of user competitions. In this regard, this paper approaches the generic energy efficiency problem with a new stochastic asymmetric Blotto game paradigm to enable the derivation of joint optimal bandwidth and transmit power allocations by setting multiple users to compete in multiple auction-like contests for their individual resource demands. The proposed modelling innovates by abstracting the notion of fairness from centrally-imposed to distributed-competitive, where each user’s pay-off probability is expressed as quantitative bidding metric, so as, all users’ actions can be interdependent, i.e., each user attains its utility given the allocations of other users, which eliminates the chance of low-valued carriers not being claimed by any user, and, in principle, enables the full utilisation of wireless resources. We also contribute by resolving the allocation problem with low complexity using new mathematical techniques based on Charnes-Cooper transformation, which eliminate the additional coefficients and multipliers that typically appear during optimisation analysis, and derive the joint optimal strategy as a set of linear single-variable functions for each user. We prove that our strategy converges towards a unique, monotonous and scalable NE, and examine its optimality, positivity and feasibility properties in detail. Simulation comparisons with relevant studies confirm the superiority of our approach in terms of higher energy efficiency performance, fairness index and quality-of-service provision

Convex optimization-based resource scheduling for multi-user wireless systems

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.For the thesis abstract, please see the main thesis file. The abstract is available in English and Greek.United Kingdom Engineering and Physical Sciences Research Council (EPSRC) and Motorola Ltd: Grant number EP/G070350/1 and 07000486

Energy efficient designs for communication systems:resolutions on inverse resource allocation principles

Energy efficient designs of communication systems are receiving great attention in both academia and industry. This letter investigates the energy efficient resource allocation schemes with Quality of Service (QoS) guarantee towards green wireless communication systems. We utilise the convex optimisation theory to obtain the optimal joint subcarrier and power allocation strategy. A new solution methodology is proposed to achieve the resolutions of transcendental equations. The simulation results demonstrate that our scheme outperforms other related approaches in terms of the energy efficiency performance, QoS guarantee and implementation complexity