The vision of next generation 5G wireless communications lies in providing very high data rates (typically of Gbps order), extremely low latency, manifold increase in base station capacity, and significant improvement in users’ perceived quality of service (QoS), compared to current 4G LTE networks. Ever increasing proliferation of smart devices, introduction of new emerging multimedia applications, together with an exponential rise in wireless data (multimedia) demand and usage is already creating a significant burden on existing cellular networks. 5G wireless systems, with improved data rates, capacity, latency, and QoS are expected to be the panacea of most of the current cellular networks’ problems. In this survey, we make an exhaustive review of wireless evolution toward 5G networks. We first discuss the new architectural changes associated with the radio access network (RAN) design, including air interfaces, smart antennas, cloud and heterogeneous RAN. Subsequently, we make an in-depth survey of underlying novel mm-wave physical layer technologies, encompassing new channel model estimation, directional antenna design, beamforming algorithms, and massive MIMO technologies. Next, the details of MAC layer protocols and multiplexing schemes needed to efficiently support this new physical layer are discussed. We also look into the killer applications, considered as the major driving force behind 5G. In order to understand the improved user experience, we provide highlights of new QoS, QoE, and SON features associated with the 5G evolution. For alleviating the increased network energy consumption and operating expenditure, we make a detail review on energy awareness and cost efficiency. As understanding the current status of 5G implementation is important for its eventual commercialization, we also discuss relevant field trials, drive tests, and simulation experiments. Finally, we point out major existing research issues and identify possible future research directions.

Next Generation 5G Wireless Networks: A Comprehensive Survey

This paper summarizes the main initiatives toward 5G wireless communication networks. Emphasis is paid on the program and project activities as well as on the recent literature. A closer look to a wide range of European Union 5G related projects is conducted. Literature review is restricted to recent thematic IEEE CommunicationsMagazine 5G issues and relevant white papers from different sources. The aim is to shed some light on what 5G is about: what are the building blocks of core 5G system concept, what are the main challenges and how to tackle them. The studied references indicate that in addition to capacity boosting technologies 5G needs to offer, e.g., low latency, ultra-reliable communications, and massive connectivity. Thus, the most demanding part in 5G development will be the design of flexible enough system concept platform that allows successful integration and management of various distinct technologies optimized for diverse use cases.

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A brief overview of 5G research activities

The ongoing densification of small cells yields an unprecedented paradigm shift in user experience and network design The most notable change comes from cellular rates being comparable to next-generation WiFi systems Cellular-to-WiFi offloading, the standard modus operandi of recent years, is therefore shifting towards a true integration of both technology families Users in future 5G systems will thus likely be able to use 3GPP, IEEE, and other technologies simultaneously, so as to maximize their quality of experience To advance this high-level vision, we perform a novel performance analysis specifically taking the system-level dynamics into account and thus giving a true account on the uplink performance gains of an integrated multi radio access technology (RAT) solution versus legacy approaches Further, we advocate for an enabling architecture that embodies the tight interaction between the different RATs, as we lay out a standardization roadmap able to materialize the envisaged design 3GPP-compliant simulations have also been carried out to corroborate the rigorous mathematical analysis and the superiority of the proposed approach

5G Multi-RAT LTE-WiFi Ultra-Dense Small Cells: Performance Dynamics, Architecture, and Trends

The exponential increase in mobile data traffic is considered to be a critical driver towards the new era, or 5G, of mobile wireless networks. 5G will require a paradigm shift that includes very high carrier frequency spectra with massive bandwidths, extreme base station densities, and unprecedented numbers of antennas to support the enormous increase in the volume of traffic. This paper discusses several design choices, features, and technical challenges that illustrate potential research topics and challenges for the future generation of mobile networks. This article does not provide a final solution but highlights the most promising lines of research from the recent literature in common directions for the 5G project. The potential physical layer technologies that are considered for future wireless communications include spatial multiplexing using massive multi-user multiple-input multiple-output (MIMO) techniques with millimetre-waves (mm-waves) in small cell geometries. These technologies are discussed in detail along with the areas for future research.

Evolution towards fifth generation (5G) wireless networks: Current trends and challenges in the deployment of millimetre wave, massive MIMO, and small cells

With the dense deployment of small cell networks, the powering and backhaul problem of small cell base stations (SBSs) has attracted great attention, and energy harvesting technology and self-backhaul technology have been proposed as promising solutions. Although some excellent works have been done on energy harvesting and self-backhaul in small cell networks, most existing works do not consider them jointly. In this paper, we aim at green small cell networks by jointly achieving self-backhaul and energy harvesting. In addition, full-duplex and massive multiple-input and multiple-output technologies are also exploited to enhance the system performance. In order to improve the energy efficiency (EE) further, a novel precoding scheme is designed to eliminate both the inter-tier and multi-user interference. Based on the proposed precoding scheme, we formulate the cell association and power allocation problem as an optimization problem to optimize the system EE performance, with the energy arrival rate and remaining battery energy in SBSs involved. The formulated optimization problem implies a sleep mechanism to control the ON/OFF of SBSs, which will further reduce the energy consumption of small cell networks. In addition, to reduce the computation complexity to solve this non-convex problem, we propose to transform the original problem into a difference of convex program, which can be efficiently solved via a constrained concave convex procedure-based algorithm. Extensive simulation results are presented to justify the effectiveness of the proposed scheme with different system configurations.

Green Full-Duplex Self-Backhaul and Energy Harvesting Small Cell Networks With Massive MIMO

The fifth generation mobile networks will be developed to improve area spectral and energy efficiency, and provide uniform user experience. Hyper-dense small cell deployment can move devices closer to the wireless network and satisfy 5G system requirements. The main challenge of this network deployment results from the random deployment, dynamic on-off, flexible connection to cellular core networks, and flat system architecture of 5G systems. Therefore, conventional network planning and radio resource management, which depend on a central control node, cannot be applied to small cell networks. In this article some cooperative distributed radio resource management algorithms for time synchronization, carrier selection, and power control are discussed for hyper-dense small cell deployment.

Cooperative distributed optimization for the hyper-dense small cell deployment

A method and an apparatus for resource allocation in a local wireless node of a system of a plurality of local wireless nodes is disclosed. An inner circle subgradient resource allocation iteration is performed based on information received from at least one other wireless node of the system and an iteration parameter until a convergent result. An updated iteration parameter is provided by at least one outer circle subgradient iteration based on the convergent result of the inner circle subgradient resource allocation iteration. The inner circle subgradient resource allocation iteration is then repeated at least once using the updated iteration parameter until a convergent result. Resources are then allocated based on the iterations.

Allocation of resources in a communication system

Efficient radio resource management is a key issue in a multi-channel femtocell system, where femtocell base stations are deployed randomly and will generate interference to each other. In this research, we formulate multi-channel power allocation as a convex optimization problem, in order to maximize the overall system throughput under complex transmit power constraint. We apply the Lagrangian duality techniques to make the problem decomposable and propose a distributed iterative subgradient algorithm, namely Multi-channel Power Allocation and Optimization (McPAO). Specifically, McPAO consists of two phases: (I) a gradient projection algorithm to solve the optimal power allocation for each channel under a fixed Lagrangian dual cost; and (II) a subgradient algorithm to update the Lagrangian dual cost by using the power allocation results from Phase I. This two-phase iteration process continues until the Lagrangian dual cost converges to the optimal value. Numerical results show that our McPAO algorithm can improve the overall system throughput by 18 %, comparing to with fixed power allocation schemes. In addition, we study the impact of errors in gradient direction estimation (Phase I), which are caused by limited or delayed information exchange among femtocells in realistic situations. These errors will be propagated into the subgradient algorithm (Phase II) and, subsequently, affect the overall performance of McPAO. A rigorous analytical approach is developed to prove that McPAO can always achieve a bounded overall throughput performance very close to the global optimum.

McPAO: A Distributed Multi-channel Power Allocation and Optimization Algorithm for Femtocells

3GPP LTE has approved uplink intra-cell power control and defined Overload Indicator (OI) for uplink intercell power control to mitigate the inter-cell interference (ICI), respectively. In this paper, we propose a hierarchical power control (HPC) scheme where intra-cell and inter-cell power control interact with each other. Inter-cell power control command is generated by Radio Resource Management (RRM) entity according to ICI-load model together with the current ICI and served load information. This ICI-load model is proposed as a guideline for coordination among cells to enable the system approach its system specific interference over thermal noise (IoT) work area. Simulation results show that for HPC scheme, the system’s IoT is well controlled to fit its pre-defined work area and the power efficiency is improved significantly. Also our proposed scheme is robust to the different settings of its inter-cell power control period.

Xiaojin Zheng

Papers

Cooperative distributed optimization for the hyper-dense small cell deployment

Allocation of resources in a communication system

McPAO: A Distributed Multi-channel Power Allocation and Optimization Algorithm for Femtocells

Hierarchical Power Control for OFDM Based LTE System