LTE-Advanced radio access enhancements: A survey

Long Term Evolution Advanced (LTE-Advanced) is the next step in LTE evolution and allows operators to improve network performance and service capabilities through smooth deployment of new techniques and technologies. LTE-Advanced uses some new features on top of the existing LTE standards to provide better user experience and higher throughputs. Some of the most significant features introduced in LTE-Advanced are carrier aggregation, enhancements in heterogeneous networks, coordinated multipoint transmission and reception, enhanced multiple input multiple output usage and deployment of relay nodes in the radio network. Mentioned features are mainly aimed to enhance the radio access part of the cellular networks. This survey article presents an overview of the key radio access features and functionalities of the LTE-Advanced radio access network, supported by the simulation results. We also provide a detailed review of the literature together with a very rich list of the references for each of the features. An LTE-Advanced roadmap and the latest updates and trends in LTE markets are also presented

Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks

Soaring capacity and coverage demands dictate that future cellular networks need to soon migrate towards ultra-dense networks. However, network densification comes with a host of challenges that include compromised energy efficiency, complex interference management, cumbersome mobility management, burdensome signaling overheads and higher backhaul costs. Interestingly, most of the problems, that beleaguer network densification, stem from legacy networks' one common feature i.e., tight coupling between the control and data planes regardless of their degree of heterogeneity and cell density. Consequently, in wake of 5G, control and data planes separation architecture (SARC) has recently been conceived as a promising paradigm that has potential to address most of aforementioned challenges. In this article, we review various proposals that have been presented in literature so far to enable SARC. More specifically, we analyze how and to what degree various SARC proposals address the four main challenges in network densification namely: energy efficiency, system level capacity maximization, interference management and mobility management. We then focus on two salient features of future cellular networks that have not yet been adapted in legacy networks at wide scale and thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and device-to-device (D2D) communications. After providing necessary background on CoMP and D2D, we analyze how SARC can particularly act as a major enabler for CoMP and D2D in context of 5G. This article thus serves as both a tutorial as well as an up to date survey on SARC, CoMP and D2D. Most importantly, the article provides an extensive outlook of challenges and opportunities that lie at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201

Intercell interference mitigation in long term evolution (LTE) and LTE-advanced

University of Technology Sydney. Faculty of Engineering and Information Technology.Bandwidth is one of the limited resources in Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks. Therefore, new resource allocation techniques such as the frequency reuse are needed to increase the capacity in LTE and LTE-A. However, the system performance is severely degraded using the same frequency in adjacent cells due to increase of intercell interference. Therefore, the intercell interference management is a critical point to improve the performance of the cellular mobile networks. This thesis aims to mitigate intercell interference in the downlink LTE and LTE-A networks. The first part of this thesis introduces a new intercell interference coordination scheme to mitigate downlink intercell interference in macrocell-macrocell scenario based on user priority and using fuzzy logic system (FLS). A FLS is an expert system which maps the inputs to outputs using “IF...THEN” rules and an aggregation method. Then, the final output is obtained through a deffuzifaction approach. Since this thesis aims to mitigate interference in downlink LTE networks, the inputs of FLS are selected from important metrics such as throughput, signal to interference plus noise ratio and so on. Simulation results demonstrate the efficacy of the proposed scheme to improve the system performance in terms of cell throughput, cell edge throughput and delay when compared with reuse factor one. Thereafter, heterogeneous networks (HetNets) are studied which are used to increase the coverage and capacity of system. The focus of the next part of this thesis is picocell because it is one of the important low power nodes in HetNets which can efficiently improve the overall system capacity and coverage. However, new challenges arise to intercell interference management in macrocell-picocell scenario. Three enhanced intercell interference coordination (eICIC) schemes are proposed in this thesis to mitigate the interference problem. In the first scheme, a dynamic cell range expansion (CRE) approach is combined with a dynamic almost blank subframe (ABS) using fuzzy logic system. In the second scheme, a fuzzy q-learning (FQL) approach is used to find the optimum ABS and CRE offset values for both full buffer traffic and video streaming traffic. In FQL, FLS is combined by q-learning approach to optimally select the best consequent part of each FLS rule. In the third proposed eICIC scheme, the best location of ABSs in each frame is determined using Genetic Algorithm such that the requirements of video streaming traffic can be met. Simulation results show that the system performance can be improved through the proposed schemes. Finally, the optimum CRE offset value and the required number of ABSs will be mathematically formulated based on the outage probability, ergodic rate and minimum required throughput of users using stochastic geometry tool. The results are an analytical formula that leads to a good initial estimate through a simple approach to analyse the impact of system parameters on CRE offset value and number of ABSs

Packet Scheduling Algorithms in LTE/LTE-A cellular Networks: Multi-agent Q-learning Approach

Spectrum utilization is vital for mobile operators. It ensures an efficient use of spectrum bands, especially when obtaining their license is highly expensive. Long Term Evolution (LTE), and LTE-Advanced (LTE-A) spectrum bands license were auctioned by the Federal Communication Commission (FCC) to mobile operators with hundreds of millions of dollars. In the first part of this dissertation, we study, analyze, and compare the QoS performance of QoS-aware/Channel-aware packet scheduling algorithms while using CA over LTE, and LTE-A heterogeneous cellular networks. This included a detailed study of the LTE/LTE-A cellular network and its features, and the modification of an open source LTE simulator in order to perform these QoS performance tests. In the second part of this dissertation, we aim to solve spectrum underutilization by proposing, implementing, and testing two novel multi-agent Q-learning-based packet scheduling algorithms for LTE cellular network. The Collaborative Competitive scheduling algorithm, and the Competitive Competitive scheduling algorithm. These algorithms schedule licensed users over the available radio resources and un-licensed users over spectrum holes. In conclusion, our results show that the spectrum band could be utilized by deploying efficient packet scheduling algorithms for licensed users, and can be further utilized by allowing unlicensed users to be scheduled on spectrum holes whenever they occur

Inter-cell interference mitigation in LTE-advanced heterogeneous mobile networks

Heterogeneous Networks are one of the most effective solutions for enhancing the network performance of mobile systems, by deploying small cells within the coverage of the ordinary Macro cells. The goals of deploying such networks are to offload data from the possibly congested Macro cells towards the small cells and to achieve enhancements for outdoor/ indoor coverage in a cost-effective way. Moreover, heterogeneous networks aim to maximise the system capacity and to provide lower interference by reducing the distance between the transmitter and the receiver. However, inter-cell interference is a major technical challenge in heterogeneous networks, which mainly affects system performance and may cause a significant degradation in network throughput (especially for the edge users) in co-channel deployment. So, to overcome the aforementioned problem, both researchers and telecommunication operators are required to develop effective approaches that adapt different mobile system scenarios. The research study presented in this thesis provides a novel interference mitigation scheme, based on power control and time-domain inter-cell interference coordination to improve cell and users’ throughputs. In addition, powerful scheduling algorithms have been developed and optimised to adapt the proposed scheme for both macro and small cells. It is responsible for the optimum resource allocation to minimise the inter-cell interference to the minimum ranges. The focus of this work is for downlink inter-cell interference in Long Term Evolution (LTE- Advanced) mobile networks, as an example of OFDMA (orthogonal frequency division multiple access)-based networks. More attention is paid to the Pico cell as an important cell type in heterogeneous deployment, due to the direct backhauling with the macro cell to coordinate the resource allocation among cells tightly and efficiently. The intensive simulations and results analyses show that the proposed scheme demonstrates better performance with less complexity in terms of user and cell throughputs, and spectral efficiency, as compared with the previously employed schem

Self-Organizing Radio Resource Management and Backhaul Dimensioning for Cellular Networks

The huge appetite for mobile broadband has resulted to continuous and complementary improvement in both radio access technology and mobile backhaul of cellular networks, along with network densification. Femtocells are foreseen to complement traditional macro base stations (BSs) in Long Term Evolution (LTE) and future cellular networks.  Deployment of femtocells, introduce new requirements for distributing phase synchronization and interference management in heterogeneous network. Achieving phase synchronization for indoor femtocells will be beneficial for time division duplexing (TDD) operation and inter-cell interference cancellation and management techniques, but challenging to achieve as global positioning system does not work indoors. In this thesis, we propose coordinated transmission and reception algorithms to reduce interference across BSs, and thereby achieve better network-wide phase synchronization over the air. We also cover the problem of selecting component carriers for dense small cell network, by improving the throughput of cell-edge user equipment's (UEs). We propose three strategies: Selfish, Altruistic and Symmetric for primary carrier selection and remove the outage of the macro UEs near the closed subscriber group (CSG) femtocells. Further, we propose dynamic frequency selection algorithm for component carrier selection, where decisions to select or drop a carrier are based on gain/loss predictions made from UE handover measurements. Thereby, we maximize the sum utility of the dense femtocell network, which includes mean-rate, weighted fair-rate, proportional fair-rate and max-min utility.  Mobile backhaul dimensioning is studied to improve the handover and provide the cost-effective backhaul opportunity for femtocells deployed in emerging markets. In a packet-switched wireless system e.g. LTE, data packets are needed to be efficiently forwarded between BSs during handover over the backhaul. We improve the packet forwarding handover mechanism by reducing the amount of forwarded data between BSs. Another challenge lies in equipping the femtocells with backhaul, where copper cable, optical fiber or microwave radio links are expensive options for unplanned emerging market case. We consider leveraging macro LTE networks to backhaul High Speed Packet Access femtocells, thereby highlight the possibilities for cost-effective capacity upgrades of dense settlements