A new opportunistic cross-layer MAC protocol involving channel allocation and packet scheduling for cognitive radio networks is proposed. Cognitive radio allows secondary users SUs to exploit the available portions of the licensed spectrum bands without interfering with primary users. In particular, we consider a cognitive radio system, where SUs are equipped with two transceivers: a control transceiver and a software-defined radio transceiver. Data traffic characteristics of SUs are considered to ameliorate system performance. So, we propose a mechanism of resource reservation to improve QoS requirements that favors successful SUs to transmit data during x time slots without interfering with primary users. The key novelty of this paper is giving priority for SUs with important data traffic and which frequently solicits data channels to transmit for the remaining time of the ongoing time slot and for the next time slots directly after checking the channel availability. We develop a new analytical model to evaluate delay parameter for two scenarios with and without resource reservation and we then investigate the impact of those scenarios on the energy consumption. We show through simulations that cognitive radio performances increase noticeably with the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.

Data traffic-based analysis of delay and energy consumption in cognitive radio networks with and without resource reservation

In wireless communication systems, the delay remains a crucial factor. In this work, we focus on the design of a new opportunistic cross-layer MAC protocol involving channels allocation and packet scheduling for cognitive networks in order to optimize system performance. Cognitive radio provides the opportunity for secondary users (unlicensed users) to use available portions of the licensed spectrum bands without interfering with primary users (licensed users). We consider that each secondary user is equipped with two transceivers. The role of the first transceiver is to obtain and exchange channels information on the control channel. The second transceiver is devoted to periodically detect and dynamically use the available data channels. The paper deals with channel allocation considering traffic characteristics of secondary users. So, we propose a mechanism of resource reservation to improve Quality of Service (QoS) requirements that favors successful secondary users to transmit data during x time slots without interfering with primary users. We develop a new analytical model, while taking into account the backoff mechanism. We analyze delay parameter for two scenarios with and without resource reservation. We show through simulations that our approach guarantees an optimal response delay.

New insights from a delay analysis for cognitive radio networks with and without reservation

Daily increasing demand for new wireless services with higher data rate and QoS level makes the upgrade of the physical layer modulation techniques inevitable. OFDMA is a common multiple access multicarrier modulation technique that is usually used in cognitive radio (CR) systems. Recently, a new technology, filter bank multicarrier system (FBMC) has been introduced to provide multiple access systems with filter banks. Therefore, it seems that OFDMA is not always the best candidate for CR systems. FBMC system is an evolutionary scheme with some advantages over the common-used OFDM multicarrier systems. This technology uses filter banks to produce independent subcarriers with better spectrum efficiency and resolutions in comparison with OFDM subcarriers. In this paper, by using an idea related to this modulation technique, we propose an uplink radio resource allocation algorithm in which fairness issue is also considered. Basically, we have focused on total capacity enhancement of a CR network using FBMC modulation. In order to better illustrate the efficiency FBMC modulation technique in future CR systems, we have also enhanced the proposed resource allocation algorithm for OFDM and FBMC based CR system in the case MIMO communications.

Uplink resource allocation for cognitive radio systems: QAM-OFDM or OQAM-OFDM?

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Device-to-device (D2D) communication broadens the applicability of cellular networks, which permits <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">user equipments (UEs) to converse with each other without the relay by a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">base station (BS) . D2D pairs can reuse the spectrum resources allocated to cellular UEs but they would cause interference. How to well manage resources and transmitted power for UEs is critical. This article considers a radio access network (RAN) sharing scenario, where multiple <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">service providers (SPs) collocate in the BS and have dedicated resources. To serve the maximum UEs, we propose a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">joint resource allocation and power control with RAN sharing (JAPS) scheme. Each SP allocates the dedicated resource to UEs and decides initial power to meet their signal-to-interference-plus-noise ratio (SINR) demands and restrain interference. Then, SPs can borrow resources from each other (i.e., inter-SP loan) to serve more UEs and better resource utilization. Finally, the power of senders is carefully adjusted to improve the signal quality. Simulation results show that JAPS can achieve a high service ratio, improve D2D throughput, and raise energy efficiency.

Joint Resource and Power Management for D2D Communication Across Multiple Service Providers

To satisfy the rapid growth of data service demands on the limited spectrum resources, wireless network virtualization (WNV) has been proposed as a promising technology in the future wireless networks. Meanwhile, Device-to-Device (D2D) communication, as an underlay to cellular networks, is also a proposed solution to promote the spectrum efficiency. However, it is a challenge to design an appropriate virtual resource slicing strategy among different wireless service providers in the two-tier LTE-D2D networks. In this paper, considering dynamic traffic arrivals and time-varying channel conditions, the virtualized resource management in the multi-service coexisting LTE-D2D networks is formulated into a multi-objective stochastic optimization problem. Leveraging on weighted Tchebycheff approach and Lyapunov optimization technique, the multi-objective stochastic optimization problem can be transformed into a delay-aware optimization problem, which is a mixed-integer nonlinear programming (MINLP) problem and can be transformed into a convex one by a series of reformulation. A distributed algorithm based on the alternating direction method of multipliers (ADMM) is proposed to obtain a close-to-optimal solution with a lower computational complexity. Finally, the simulation results show that the proposed scheme can achieve a performance-delay tradeoff related to the control factor $V$ with at most ${0.2}{\%}$ performance loss compared with the optimal solution.

Delay-Aware Resource Management for Multi-Service Coexisting LTE-D2D Networks With Wireless Network Virtualization

This context addresses the subcarrier and power allocation problem in the uplink of an OFDMA system under the cognitive radio environment. The objective is to maximize the sum transmission rate of secondary users, without causing adverse interference to the primary users. We formulate the optimization problem subject to the individual power constraints and the interference constraints. We also propose two suboptimal power loading algorithms that are less complex and a new subcarrier allocation algorithm. The performance of the optimal scheme is compared with the performance of the suboptimal. Simulation results show that the optimal algorithm significantly improves the sum transmission rate, and provides good convergence.

Resource allocation algorithm for uplink OFDMA-based cognitive radio systems

Wireless virtualization is an emerging solution for future wireless networks. Besides, device-to-device (D2D) communications has also gathered significant attention as another promising technology to meet the increasing demand. To merge the merits of the both, this paper addresses the virtual resource allocation with D2D communications underlaying LTE networks. By considering the cost of all the service providers (SP), the problem is formulated as a binary integer programming. On the basis of that, the cost-oriented virtual resource allocation is proposed. Simulation results shows that the proposed scheme outperforms the benchmark in terms of the total utility and cost for all the SPs.

Cost-oriented virtual resource allocation for device-to-device communications underlaying LTE networks

Phase offset is inevitable in asynchronous physical-layer network coding (PNC) systems, which restricts the accuracy of PNC decoding. To address this issue, this paper proposes a half-blind equalization based on pre-distortion. In the scheme, the intentional phase distortion is pre-brought into the symbols of one user, and then, it is utilized by the relay to equalize the received signals and modify the updating equations in the decoding process. By formulating a phase gain-loss factor model, the upper bound of proposed equalization is proved. On the basis of that, a threshold is proposed to avoid unnecessary distortion. Simulation results verify the effectiveness of the theoretical analysis, and show that the bit error rate performance can be improved by the proposed algorithm.

Longxiang Yang

Papers

Resource allocation algorithm for uplink OFDMA-based cognitive radio systems

Cost-oriented virtual resource allocation for device-to-device communications underlaying LTE networks

Phase offset equalization based on half-blind pre-distortion for asynchronous physical-layer network coding