Since wireless network virtualization enables abstraction and sharing of infrastructure and radio spectrum resources, the overall expenses of wireless network deployment and operation can be reduced significantly. Moreover, wireless network virtualization can provide easier migration to newer products or technologies by isolating part of the network. Despite the potential vision of wireless network virtualization, several significant research challenges remain to be addressed before widespread deployment of wireless network virtualization, including isolation, control signaling, resource discovery and allocation, mobility management, network management and operation, and security as well as non-technical issues such as governance regulations, etc. In this paper, we provide a brief survey on some of the works that have already been done to achieve wireless network virtualization, and discuss some research issues and challenges. We identify several important aspects of wireless network virtualization: overview, motivations, framework, performance metrics, enabling technologies, and challenges. Finally, we explore some broader perspectives in realizing wireless network virtualization.

Wireless Network Virtualization: A Survey, Some Research Issues and Challenges

Traditional power grids are currently being transformed into smart grids (SGs). SGs feature multi-way communication among energy generation, transmission, distribution, and usage facilities. The reliable, efficient, and intelligent management of complex power systems requires integration of high-speed, reliable, and secure data information and communication technology into the SGs to monitor and regulate power generation and usage. Despite several challenges, such as trade-offs between wireless coverage and capacity as well as limited spectral resources in SGs, wireless communication is a promising SG communications technology. Cognitive radio networks (CRNs) in particular are highly promising for providing timely SG wireless communications by utilizing all available spectrum resources. We provide in this paper a comprehensive survey on the CRN communication paradigm in SGs, including the system architecture, communication network compositions, applications, and CR-based communication technologies. We highlight potential applications of CR-based SG systems. We survey CR-based spectrum sensing approaches with their major classifications. We also provide a survey on CR-based routing and MAC protocols, and describe interference mitigation schemes. We furthermore present open issues and research challenges faced by CR-based SG networks along with future directions.

Cognitive Radio for Smart Grids: Survey of Architectures, Spectrum Sensing Mechanisms, and Networking Protocols

Due to its potential for multi-gigabit and low latency wireless links, millimeter wave (mmWave) technology is expected to play a central role in 5th generation (5G) cellular systems. While there has been considerable progress in understanding the mmWave physical layer, innovations will be required at all layers of the protocol stack, in both the access and the core network. Discrete-event network simulation is essential for end-to-end, cross-layer research and development. This paper provides a tutorial on a recently developed full-stack mmWave module integrated into the widely used open-source ns–3 simulator. The module includes a number of detailed statistical channel models as well as the ability to incorporate real measurements or ray-tracing data. The physical and medium access control layers are modular and highly customizable, making it easy to integrate algorithms or compare orthogonal frequency division multiplexing numerologies, for example. The module is interfaced with the core network of the ns–3 Long Term Evolution (LTE) module for full-stack simulations of end-to-end connectivity, and advanced architectural features, such as dual-connectivity, are also available. To facilitate the understanding of the module, and verify its correct functioning, we provide several examples that show the performance of the custom mmWave stack as well as custom congestion control algorithms designed specifically for efficient utilization of the mmWave channel.

End-to-End Simulation of 5G mmWave Networks

Due to its potential for multi-gigabit and low latency wireless links, millimeter wave (mmWave) technology is expected to play a central role in 5th generation cellular systems. While there has been considerable progress in understanding the mmWave physical layer, innovations will be required at all layers of the protocol stack, in both the access and the core network. Discrete-event network simulation is essential for end-to-end, cross-layer research and development. This paper provides a tutorial on a recently developed full-stack mmWave module integrated into the widely used open-source ns--3 simulator. The module includes a number of detailed statistical channel models as well as the ability to incorporate real measurements or ray-tracing data. The Physical (PHY) and Medium Access Control (MAC) layers are modular and highly customizable, making it easy to integrate algorithms or compare Orthogonal Frequency Division Multiplexing (OFDM) numerologies, for example. The module is interfaced with the core network of the ns--3 Long Term Evolution (LTE) module for full-stack simulations of end-to-end connectivity, and advanced architectural features, such as dual-connectivity, are also available. To facilitate the understanding of the module, and verify its correct functioning, we provide several examples that show the performance of the custom mmWave stack as well as custom congestion control algorithms designed specifically for efficient utilization of the mmWave channel.

Time-critical and delay-sensitive multimedia applications require more spectrum and transmission resources. With the provision of cognitive radios (CRs), the underutilized spectrum resources can be exploited to gain more bandwidth for the bandwidth hungry applications (multimedia applications). Cognitive radio networks (CRNs) also have the flexibility to adjust their transmission parameters according to the needs of multimedia services or applications. For this reason, wireless multimedia cognitive radio networks (WMCRNs) have gained much attentions in today’s research domain. In this paper, we present a comprehensive survey of WMCRNs. Various multimedia applications supported by CRNs, and various CR-based wireless networks are surveyed. We highlight the routing and link layer protocols used for WMCRNs. We cover the quality-of-experience design and security requirements for transmitting multimedia content over CRNs. We provide an in-depth study of white space, television white space, and cross-layer designs that have been used for WMCRNs. We also survey the major spectrum sensing approaches used for the communications of bandwidth hungry and time-critical data over CRNs.

Wireless Multimedia Cognitive Radio Networks: A Comprehensive Survey

Cognitive radio technology is a key enabler to reuse a finite, scarce, and expensive resource: the radio spectrum. Guaranteeing required levels of QoS to cognitive users and ensuring necessary protection to incumbent users are the two main challenges in opportunistic spectrum access. This article identifies the main requirements and challenges for QoS support in cognitive radio networks. A framework for a twofold cognitive manager is presented; one part managing spectrum availability on longer timescales and the other handling resource management on shorter timescales. This article gives particular focus to the functionalities of the latter cognitive manager related to resource management. Finally, we present a few key scenarios and describe how QoS can be managed with the proposed approach without disturbing the communications of incumbent users.

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Resource management for QoS support in cognitive radio networks

Millimeter wave point to point links have been used as backhaul links for cellular networks for decades. These have always been carefully planned so that their link budgets include a reserve for rain fading. Fast and low cost deployment of 5G backhaul networks may be enabled by a system of millimeter wavelength point to point links where the network is not carefully planned; instead the nodes are semi-randomly deployed and afterwards organized into a network. While this concept has many benefits, rain fading may cause some links to fail, thereby threatening the connectivity of the network. This paper presents the effects of rain fading in such millimeter wavelength mesh networks. The issue is investigated with simulations, and with the use of rain fading measurement data covering a span of five years. Our main result quantifies the probability of network failure due to rain fading in millimeter wave flexible backhaul mesh networks of future 5G systems.

Effects of rain fading in 5G millimeter wavelength mesh networks

The performance of rain rate and rain attenuation prediction models are vital for planning wireless networks consisting of millimeter wave links. As several different prediction models exist in literature we give a comparison of the performance of the most applied ones. Moreover, we introduce methods for transforming rain attenuation between different millimeter wave links based on the investigated prediction models. This transformation enables the exploitation of long-range link measurements to effectively plan networks comprised of short-range millimeter wave links (like 5G mesh networks). We identify the most suitable rain attenuation prediction model and verify the proposed transformation model with the ITU-P.530-15 model on long-term statistics. The purpose of this paper is to investigate different rain attenuation prediction models for terrestrial links and to find a suitable prediction method to perform a transformation of rain attenuation on millimeter wave links with different physical parameters (length, frequency, and polarization).

http://ieeexplore.ieee.org/iel7/7474317/7481093/07481358.pdf

Characteristics of 5G wireless millimeter wave propagation: Transformation of rain attenuation applying different prediction models

The short range microwave mesh network concept will play a significant role in 5th generation communication systems. However, precipitation is crucial in this frequency range as it causes additional attenuation. In this paper a simulated Exponential Cell rain model is applied for the generation of synthetic rain cells that cross the area according to a two dimensional non-symmetrical random walk (applying a discrete time and discrete state homogenous Markov model). The rain cell occurrence probability and the translational velocity are derived from measured rain rate statistics. Our goal is to investigate how the ratio of the disconnected nodes in the microwave mesh network varies according to rain intensities in a scenario when rerouting is applied as a technique to improve network resilience. Outcomes of this work on the performance of 5G mesh networks strengthen our previous conclusions that are based on a transformation of rain attenuation on long range links.

Precipitation modelling for performance evaluation of ad-hoc microwave 5G mesh networks

This paper investigates the bandwidth efficiency of packet based mobile backhaul in case of low rate, delay sensitive voice service. Evolved HSPA is a fully packet based mobile technology where the voice service is VoIP based. VoIP sources generate small packets periodically. The overhead on these packets is significant; it even exceeds the useful payload, causing efficiency problems on the mobile backhaul where bandwidth is still a scarce resource. A possible way to improve the efficiency of the voice service is to aggregate multiple voice packets into a single transport frame, a technique that reduces the relative overhead. This paper provides an overview of the available aggregation methods referred to as bundling and multiplexing. The performance of these solutions and their impact on the QoS of the voice service is investigated with simulations. Results show that if the backhaul is the bottleneck, the maximum number of VoIP connections that can be served jumps by up to 60%.

Arpad Drozdy

Papers

Resource management for QoS support in cognitive radio networks

Effects of rain fading in 5G millimeter wavelength mesh networks

Characteristics of 5G wireless millimeter wave propagation: Transformation of rain attenuation applying different prediction models

Precipitation modelling for performance evaluation of ad-hoc microwave 5G mesh networks

Bundling and multiplexing in packet based mobile backhaul