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In this paper, a new mode selection (MS) scheme for device-to-device (D2D) enabled cellular networks is proposed. The MS is carried out using a predefined signal-to-interference plus noise ratio (SINR) threshold and it aims to guarantee a minimum level of quality of service. With the new scheme, interfering effects are taken into consideration, while realistic assumptions for the acquisition of the channel information are made. Assuming a single-user case, an analytical framework is developed, which is based on the Markov-chain theory, and is used to study the system's performance. The various performance results obtained reveal that with the proposed MS, the probability of mode switching can be reduced (as compared to other systems), and thus, an increase on the overhead and signal processing is avoided. Moreover, a new approach is applied in a multi-user communication scenario, where a joint MS, resource allocation (RA), and scheduling optimization problem is formulated. The solution to this problem is based on a greedy heuristic algorithm that properly assigns the available resources among cellular users and D2D pairs. The joint MS, RA, and scheduling algorithm considers limited SINR awareness and it provides significant performance improvement in terms of sum-rate. © 1967-2012 IEEE.

One of the most promising applications of cognitive radio networks (CRNs) is the efficient exploitation of TV white spaces (TVWSs) for enhancing the performance of wireless networks. In this paper, we propose a cross-layer design (CLD) of carrier sense multiple access with collision avoidance (CSMA/CA) mechanism at the medium access control (MAC) layer with spectrum sensing (SpSe) at the physical layer, for identifying the occupancy status of TV bands. The proposed CLD relies on a Markov chain model with a state pair containing both the SpSe and the CSMA/CA from which we derive the collision probability and the achievable throughput. Analytical and simulation results are obtained for different collision avoidance and SpSe implementation scenarios by varying the contention window, back off stage and probability of detection. The obtained results depict the achievable throughput under different collision avoidance and SpSe implementation scenarios indicating thereby the performance of collision avoidance in TVWSs-based CRNs. © 2014 © 2014 Taylor & Francis.

We study the performance of cognitive radio networks (CRNs) when incorporating adaptive modulation at the physical layer. Three types of CRNs are considered, namely opportunistic spectrum access (OSA), spectrum sharing (SS) and sensing-based SS. We obtain closed-form expressions for the average spectral efficiency achieved at the secondary network and the optimal power allocation for both continuous and discrete rate types of adaptive modulation assuming perfect channel state information. The obtained numerical results show the achievable performance gain in terms of average spectral efficiency and the impact on power allocation when adaptive modulation is implemented at the physical layer that is due to the effect of the cut-off level that is determined from the received signal-to-noise ratio for each CRN type. The performance assessment is taking place for different target bit error rate values and fading regions, thereby providing useful performance insights for various possible implementations. © 2013 Published by Elsevier Ltd.

We study the problem of joint power control and spectrum sensing for maximising the capacity at the secondary user while protecting the primary user's transmissions in spectrum sharing cognitive radio systems. Power control regulates the transmission power of the secondary user and spectrum sensing regulates the sensing time and the sensing threshold that care for the primary user's protection. This problem is a capacity maximisation problem that we formulate and solve using an iterative greedy algorithm due to its complex form. The solution of the proposed algorithm leads to the global optimal solution that represents the optimal triplet values of transmission power, sensing time and threshold. The obtained results show the potential capacity maximisation that is achieved by the proposed joint design as long as the primary user's protection is provided. Finally the convergence behaviour of the proposed algorithm is assessed in terms of the needed iterations for enhancing the capacity of spectrum sharing systems. © 2013 Copyright Taylor and Francis Group, LLC.

Third-generation (3G) and beyond 3G mobile communication systems must provide interoperability with the Internet, increase throughput for mobile devices, and optimize their operation for multimedia applications. The limited ability of traditional layered architectures to exploit the unique nature of wireless communication has fostered the introduction of cross-layer design solutions that allow optimized operation for mobile devices in the modern heterogeneous wireless environment. In this article we present the major cross-layer design solutions that handle such problems, and discuss cross-layer implementations with a focus on functional entities that support cross-layer processes and the respective signaling. In addition, we consider the associated architectural complexity and communication overhead they introduce. Furthermore, we point out the major open technical challenges in the cross-layer design research area. Finally, we conclude our article with a summary of cross-layer approaches developed thus far and provide directions for future work.

The development, delivery and management of mobile services are the subject of many research activities in both the academia and industry. The ultimate goal of these efforts is a dynamic environment that enables the delivery of situation-aware, personalized multimedia services over heterogeneous, ubiquitous infrastructures, commonly termed as systems beyond 3rd generation (3G). Reconfigurability and adaptability are key aspects of the mobile systems beyond 3G. Reconfigurable mobile systems and networks introduce additional requirements and complexity. Using the existing network control plane is inadequate for the realization of the reconfigurability process. Introducing a Reconfiguration Management Plane is very important for the deployment of network/system wide reconfigurability. In this paper we intend to discuss the basic functionality of RMP and respective interrelations.

International audience; Industrial Internet of Things (IIoT) networks are considered the large-scale deployment of IoT devices for industrial applications such as smart manufacturing, harvesting and supply chain management. The Internet of Things (IoT) devices are typically connected over a wireless medium, given the large geographical distribution area and the increasing demand for flexible installations. In some cases, a combination of wired and wireless connectivity can be assumed as common practice. In both scenarios, wireless communications for IIoT networks is a fundamental component of the system architecture that needs to satisfy stringent requirements such as reliable connectivity and minimal delays. Therefore, the dependability of wireless communications for IIoT networks should be carefully studied to provide new solutions, which can guarantee that applications can meet their real-time and reliability requirements while optimizing the control capability of the overall network. This paper focuses on the dependable wireless communications in the IIoT networks, where wireless control and monitoring tasks need to meet stringent real-time and reliability constraints. After reviewing recent solutions and discussing their suitability for IIoT networks, we highlight the yet open challenges that needs to be tackled by both academia and industry.