Showing papers on "LTE Advanced published in 2015"

Device-to-Device Communication in LTE-Advanced Networks: A Survey

Abstract: Among the LTE-A communication techniques, Device-to-Device (D2D) communication which is defined to directly route data traffic between spatially closely located mobile user equipments (UEs), holds great promise in improving energy efficiency, throughput, delay, as well as spectrum efficiency As a combination of ad-hoc and centralized communication mechanisms, D2D communication enables researchers to merge together the long-term development achievements in previously disjoint domains of ad-hoc networking and centralized networking To help researchers to have a systematic understanding of the emerging D2D communication, we provide in this paper a comprehensive survey of available D2D related research works ranging from technical papers to experimental prototypes to standard activities, and outline some open research problems which deserve further studies

LTE-unlicensed: the future of spectrum aggregation for cellular networks

Abstract: The phenomenal growth of mobile data demand has brought about increasing scarcity in available radio spectrum. Meanwhile, mobile customers pay more attention to their own experience, especially in communication reliability and service continuity on the move. To address these issues, LTE-Unlicensed, or LTEU, is considered one of the latest groundbreaking innovations to provide high performance and seamless user experience under a unified radio technology by extending LTE to the readily available unlicensed spectrum. In this article, we offer a comprehensive overview of the LTEU technology from both operator and user perspectives, and examine its impact on the incumbent unlicensed systems. Specifically, we first introduce the implementation regulations, principles, and typical deployment scenarios of LTE-U. Potential benefits for both operators and users are then discussed. We further identify three key challenges in bringing LTE-U into reality together with related research directions. In particular, the most critical issue of LTE-U is coexistence with other unlicensed systems, such as widely deployed WiFi. The LTE/WiFi coexistence mechanisms are elaborated in time, frequency, and power aspects, respectively. Simulation results demonstrate that LTE-U can provide better user experience to LTE users while well protecting the incumbent WiFi users’ performance compared to two existing advanced technologies: cellular/WiFi interworking and licensed-only heterogeneous networks (Het-Nets).

M2M Communications in 3GPP LTE/LTE-A Networks: Architectures, Service Requirements, Challenges, and Applications

Abstract: Machine-to-machine (M2M) communication is an emerging technology to provide ubiquitous connectivity among devices without human intervention. The cellular networks are considered a ready-to-use infrastructure to implement M2M communications. However, M2M communications over cellular pose significant challenges to cellular networks due to different data transactions, diverse applications, and a large number of connections. To support such a large number of devices, M2M system architecture should be extremely power and spectrum efficient. In this paper, we provide a comprehensive survey on M2M communications in the context of the Third-Generation Partnership Project (3GPP) Long-Term Evolution (LTE) and Long-Term Evolution-Advanced (LTE-A). More specifically, this paper presents architectural enhancements for providing M2M services in 3GPP LTE/LTE-A networks and reviews the features and requirements of M2M applications. In addition, the signal overheads and various quality-of-service (QoS) requirements in M2M communications also deserve our attention. We address M2M challenges over 3GPP LTE/LTE-A and also identify the issues on diverse random access overload control to avoid congestion caused by random channel access of M2M devices. Different application scenarios are considered to illustrate futuristic M2M applications. Finally, we present possible enabling technologies and point out the directions for M2M communications research.

5G Communications Race: Pursuit of More Capacity Triggers LTE in Unlicensed Band

Abstract: Fifth-generation (5G) network developers need to identify the necessary requirements toward additional capacity and spectrally efficient wireless technologies. Therefore, the significant amount of underutilized spectrum in the Wi-Fi band is motivating operators to combine long-term evolution (LTE) with Wi-Fi technologies. This new LTE in unlicensed band (LTE-U) has the physical layer topology to access Wi-Fi spectrum, specifically the 5-GHz band. Nevertheless, the evolution of LTE-U affects the Wi-Fi operations due to the absence of any regularity for LTE-U transmissions in unlicensed band. In this article, we address the challenges for Wi-Fi to maintain transmissions under the umbrella of LTE-U as Wi-Fi is pushed offline because of the listen-before-talk (LBT) feature. Therefore, we derive a new adaptive LBT mechanism and and virtualized core network for the best practices in both Wi-Fi and LTE-U technologies. The proposed solutions include noncoordinated and coordinated network managements to enable coexistence between both technologies using tradeoff performance for fair spectrum sharing. We concentrate on the initial coexistent technique and discuss how it maps to higher-layer improvements. This article shows new approaches to achieve the Third-Generation Partnership Project (3GPP) Release 13.

Recent advancements in M2M communications in 4G networks and evolution towards 5G

Abstract: Machine-to-Machine (M2M) communications is considered to be one of the key enablers for the provisioning of advanced applications and services such as smart cities and hospitals, as well as automated vehicular and industrial automation operation. Currently, in LTE-Advanced systems, the main focus has been on supporting massive deployment of low cost devices, with enhanced radio access network coverage. In this work, we present the recent MTC enhancements in LTE system. Detailed performance analysis based on LTE system settings is also presented. The LTE capacity evaluations performed based on devices per physical resource block indicate that significantly large number of devices can already be supported in an LTE system, based on the assumptions used, with minimal system overhead. We also present an overview of some of the key scenarios, requirements and use cases currently being considered for M2M communication in fifth generation (5G) systems. The performance requirements currently being considered for massive and ultra-reliable M2M communication are also discussed.

Resource Allocation and Link Adaptation in LTE and LTE Advanced: A Tutorial

Abstract: Resource allocation and link adaptation in Long-Term Evolution (LTE) and LTE Advanced are discussed with focus on the location and formatting of the pertinent reference and control signals, as well as the decisions they enable. In particular, after reviewing the units for resource allocation and the time-frequency resource grid, the enabled resource-allocation modes and their purposes are reviewed. A detailed description of the way the resource allocations are encoded under these different modes is also given. Similarly, the various methods of link adaptation, including power control and rate control, both through the use of adaptive modulation and coding and hybrid automatic repeat request, are reviewed. The control signaling encoding for link adaptation is provided in detail, as is the encoding of channel state feedback for the purposes of link adaptation and resource allocation.

Coordinated Dynamic Spectrum Management of LTE-U and Wi-Fi Networks

Abstract: This paper investigates the co-existence of Wi-Fi and LTE in emerging unlicensed frequency bands which are intended to accommodate multiple radio access technologies. Wi-Fi and LTE are the two most prominent access technologies being deployed today, motivating further study of the inter-system interference arising in such shared spectrum scenarios as well as possible techniques for enabling improved co-existence. An analytical model for evaluating the baseline performance of co-existing Wi-Fi and LTE is developed and used to obtain baseline performance measures. The results show that both Wi-Fi and LTE networks cause significant interference to each other and that the degradation is dependent on a number of factors such as power levels and physical topology. The model-based results are partially validated via experimental evaluations using USRP based SDR platforms on the ORBIT testbed. Further, inter-network coordination with logically centralized radio resource management across Wi-Fi and LTE systems is proposed as a possible solution for improved co-existence. Numerical results are presented showing significant gains in both Wi-Fi and LTE performance with the proposed inter-network coordination approach.

Simulating LTE/LTE-Advanced Networks with SimuLTE

Abstract: In this work we present SimuLTE, an OMNeT++-based simulator for LTE and LTE-Advanced networks. Following well-established OMNeT++ programming practices, SimuLTE exhibits a fully modular structure, which makes it easy to be extended, verified, and integrated. Moreover, it inherits all the benefits of such a widely used and versatile simulation framework as OMNeT++, i.e., experiment support and seamless integration with the OMNeT++ network modules, such as INET. This allows SimuLTE users to build up mixed scenarios where LTE is only a part of a wider network. This paper describes the architecture of SimuLTE, with particular emphasis on the modeling choices at the MAC layer, where resource scheduling is located. Furthermore, we describe some of the verification and validation efforts and present an example of the performance analysis that can be carried out with SimuLTE.

Modeling and Analysis of an Extended Access Barring Algorithm for Machine-Type Communications in LTE-A Networks

Abstract: Simultaneous channel accesses from mass machine-type communications (MTC) devices may congest the random-access channels (RACHs) of LTE-A networks. Currently, 3GPP selects extended access barring (EAB) mechanism as the baseline solution to relieve the congestion of RACHs by barring low-priority devices. Different settings of EAB parameters may re-shape the arrival process of MTC traffic and thus, lead to unpredictable performance. This paper presents an analytical model to investigate the performance of the EAB algorithm on the RACHs in LTE-A networks. Computer simulations were conducted to verify the accuracy of the analysis. The optimal values of paging cycle and repetition period of system information block type 14 (SIB14) can then be obtained from the analytical model subject to a target quality-of-service (QoS) constraint.

Coexistence of Wi-Fi and LAA-LTE: Experimental evaluation, analysis and insights

Abstract: LTE-A as a cellular technology has gained tremendous importance in recent years due to its high data-rates and improved data access for mobile devices Recently, utilizing the unlicensed band as a supplementary band for LTE-A is being considered to expand the capacity of mobile systems License-assisted access using LTE (LAA-LTE) will thus operate in the unlicensed band, and will operate in a spectrum that overlaps with Wi-Fi, another popular unlicensed-band technology The concern is that LAA-LTE and Wi-Fi are unlikely to have mechanisms to directly coordinate with each other to address channel-sharing issues In this paper, we study the interference impact of LAA-LTE on Wi-Fi under various network conditions using purely experimental analysis in indoor environments The following three questions are specifically considered in this paper: (1) What are the implications of LAA-LTE usage on Wi-Fi? (2) How should LAA-LTE or Wi-Fi be configured for Wi-Fi to be less impacted? (3) How should the LAA-LTE MAC protocol be designed to be gracefully co-exist with Wi-Fi? To answer the above questions, we present comprehensive experimental results and give insights based on the results

5G Radio Access: Requirements, Concept and Experimental Trials

Abstract: Currently, many operators worldwide are deploying Long Term Evolution (LTE) to provide much faster access with lower latency and higher efficiency than its predecessors 3G and 3.5G. Meanwhile, the service rollout of LTE-Advanced, which is an evolution of LTE and a “true 4G” mobile broadband, is being underway to further enhance LTE performance. However, the anticipated challenges of the next decade (2020s) are so tremendous and diverse that there is a vastly increased need for a new generation mobile communications system with even further enhanced capabilities and new functionalities, namely a fifth generation (5G) system. Envisioning the development of a 5G system by 2020, at DOCOMO we started studies on future radio access as early as 2010, just after the launch of LTE service. The aim at that time was to anticipate the future user needs and the requirements of 10 years later (2020s) in order to identify the right concept and radio access technologies for the next generation system. The identified 5G concept consists of an efficient integration of existing spectrum bands for current cellular mobile and future new spectrum bands including higher frequency bands, e.g., millimeter wave, with a set of spectrum specific and spectrum agnostic technologies. Since a few years ago, we have been conducting several proof-of-concept activities and investigations on our 5G concept and its key technologies, including the development of a 5G real-time simulator, experimental trials of a wide range of frequency bands and technologies and channel measurements for higher frequency bands. In this paper, we introduce an overview of our views on the requirements, concept and promising technologies for 5G radio access, in addition to our ongoing activities for paving the way toward the realization of 5G by 2020. key words: next generation mobile communications system, 5G, 4G, LTE, LTE-advanced

A Fuzzy Multi-Metric QoS-Balancing Gateway Selection Algorithm in a Clustered VANET to LTE Advanced Hybrid Cellular Network

Abstract: Intelligent transportation systems are currently attracting the attention of the research community and the automotive industry, which both aim to provide not only more safety in the transportation systems but other high-quality services and applications for their customers as well. In this paper, we propose a cooperative traffic transmission algorithm in a joint vehicular ad hoc network–Long Term Evolution Advanced (LTE Advanced) hybrid network architecture that elects a gateway to connect the source vehicle to the LTE Advanced infrastructure under the scope of vehicle-to-infrastructure (V2I) communications. The originality of the proposed fuzzy quality-of-service (QoS)-balancing gateway selection (FQGwS) algorithm is the consideration of QoS traffic class constraints for electing the gateway. Our algorithm is a multicriteria and QoS-based scheme optimized by performing the fuzzy logic to make the decision on the appropriate gateway. Criteria are related to the received signal strength (RSS) and load of the cluster head (CH) and gateway candidates (GwCs), as well as the vehicle-to-vehicle link connectivity duration (LCD). Simulation results demonstrate that our algorithm gets better results than the deterministic scheme for gateway selection. Moreover, results show the efficiency of the FQGwS algorithm as it adapts its gateway selection decision to the cluster density and the relative velocity of the source node.

An Enhanced Handover Scheme for Mobile Relays in LTE-A High-Speed Rail Networks

Abstract: Recently, the mobile relay technique has been discussed to support communication services for Long-Term Evolution Advanced (LTE-A) high-speed rail networks. In the network, there are several mobile relays in a train. User equipment (UE) devices connect to in-car mobile relays instead of outside evolved NodeBs (eNBs). Mobile relays establish backhaul links with the serving donor eNBs (DeNBs) and coordinate control and data flows for UE devices. Since the train travels in high speed, mobile relays suffer from frequent handovers between DeNBs. We observe that the defined handover procedures in LTE-A specifications may incur message overhead and lengthen handover time. In this paper, we propose an enhanced handover scheme, which contains two procedures. The first procedure is an enhanced measurement procedure, which can accelerate the measurement procedure when the mobile relay knows that the train is moving toward some neighbor DeNBs. The second procedure is a group in-network handover procedure, which can aggregate similar in network handover procedures in the core network. Performance evaluations indicate that our design can conserve both time and messages when handover.

Device-to-Device Discovery for Proximity-Based Service in LTE-Advanced System

Abstract: In this paper, we propose a device-to-device (D2D) discovery scheme as a key enabler for a proximity-based service in the Long-Term Evolution Advanced (LTE-A) system. The proximity-based service includes a variety of services exploiting the location information of user equipment (UE), for example, the mobile social network and the mobile marketing. To realize the proximity-based service in the LTE-A system, it is necessary to design a D2D discovery scheme by which UE can discover another UE in its proximity. We design a D2D discovery scheme based on the random access procedure in the LTE-A system. The proposed random-access-based D2D discovery scheme is advantageous in that 1) the proposed scheme can be readily applied to the current LTE-A system without significant modification; 2) the proposed scheme discovers pairs of UE in a centralized manner, which enables the access or core network to centrally control the formation of D2D communication networks; and 3) the proposed scheme adaptively allocates resource blocks for the D2D discovery to prevent underutilization of radio resources. We analyze the performance of the proposed D2D discovery scheme. A closed-form formula for the performance is derived by means of the stochastic geometry-based approach. We show that the analysis results accurately match the simulation results.

Runtime Precoding: Enabling Multipoint Transmission in LTE-Advanced System-Level Simulations

Abstract: System-level simulations have become an indispensable tool for predicting the behavior of wireless cellular systems. As exact link-level modeling is unfeasible due to its huge complexity, mathematical abstraction is required to obtain equivalent results by less complexity. A particular problem in such approaches is the modeling of multiple coherent transmissions. Those arise in multiple-input-multiple-output transmissions at every base station but nowadays so-called coordinated multipoint (CoMP) techniques have become very popular, allowing to allocate two or more spatially separated transmission points. Also, multimedia broadcast single frequency networks (MBSFNs) have been introduced recently in long-term evolution (LTE), which enables efficient broadcasting transmission suitable for spreading information that has a high user demand as well as simultaneously sending updates to a large number of devices. This paper introduces the concept of runtime-precoding, which allows to accurately abstract many coherent transmission schemes while keeping additional complexity at a minimum. We explain its implementation and advantages. For validation, we incorporate the runtime-precoding functionality into the Vienna LTE-A downlink system-level simulator, which is an open source tool, freely available under an academic noncommercial use license. We measure simulation run times and compare them against the legacy approach as well as link-level simulations. Furthermore, we present multiple application examples in the context of intrasite and intersite CoMP for train communications and MBSFN.

Overview of LTE enhancements for cellular IoT

Abstract: The Internet of Things will bring about billions of connected devices. In the cellular space, machine type communications using LTE is under consideration by many operators. LTE, however, was designed to provide broadband high-speed data service with very low latency. Machine type communications, on the other hand, have a different set of requirements, namely low-rate, low-overhead, low-power-consumption, and low-cost. To address these requirements and also to minimize impact from machine traffic to human traffic, 3GPP has been working on numerous LTE features such as power saving, overload control, signaling reduction, complexity reduction, and coverage enhancement. This paper will provide an overview of LTE enhancements for machine type communications. The paper will also present LTE capacity analysis for machine traffic as well as the battery life of the devices.

A comprehensive survey of TDD-based mobile communication systems from TD-SCDMA 3G to TD-LTE(A) 4G and 5G directions

Abstract: TDD (Time Division Duplex) is one of the two duplex modes. TD-SCDMA (Time Division Synchronous CDMA) is the first TDD-based cellular mobile system which is commercialized in wide area and large scale and TD-SCDMA is also the first cellular mobile system which adopted smart antenna technology (also called as beamforming). As the long term evolution of TD-SCDMA, TD-LTE(A) (Time Division-Long Term Evolution, and TD-LTE Advanced) introduced OFDM (Orthogonal Frequency Division Multiplexing) and enhanced smart antenna technology together with MIMO (Multiple Input Multiple Output), which are adopted by LTE FDD (Frequency Division Duplex) either. It is indicated that TD-SCDMA and TD-LTE(A) have opened a sustainable utilization era of TDD and smart antenna technologies in the wireless mobile communication. This paper aims to present a systematic introduction to TDD-based mobile communications from TD-SCDMA to TD-LTE and beyond, with particular focuses on TDD key technologies, principles of TDD cellular mobile systems, TDD evolution path, and future TDD 5G directions. The comparisons between TDD and FDD are also included. We hope that this paper will provide a comprehensive overview of TDD technology upgrade and its standard evolution, and serve as a valuable reference for research on 5G mobile communication systems. It is believed that TDD will play more important role in 5G.

Capacity evaluation of Aerial LTE base-stations for public safety communications

Abstract: Aerial-Terrestrial communication networks able to provide rapidly-deployable and resilient communications capable of offering broadband connectivity are emerging as a suitable solution for public safety scenarios. During natural disasters or unexpected events, terrestrial infrastructure can be seriously damaged or disrupted due to physical destruction of network components, disruption in subsystem interconnections and/or network congestion. In this context, Aerial-Terrestrial communication networks are intended to provide temporal large coverage with the provision of broadband services at the disaster area. This paper studies the performance of Aerial UMTS Long Term Evolution (LTE) base stations in terms of coverage and capacity. Network model relies on appropriate channel model, LTE 3GPP specifications and well known schedulers are used. The results show the effect of the temperature, bandwidth, and scheduling discipline on the system capacity while at the same time coverage is investigated in different public safety scenarios.

Backhaul-Aware User Association in FiWi Enhanced LTE-A Heterogeneous Networks

Abstract: In this paper, we shed some light on the latency and reliability issues of mobile backhaul networks, which have been largely ignored in the past, and examine their impact on LTE-A heterogeneous networks (HetNets). Specifically, we propose a backhaul-aware user association algorithm for fiber-wireless (FiWi) enhanced LTE-A HetNets. The performance limiting factors of state-of-the-art fiber backhaul infrastructures are highlighted and a variety of solutions are described. To mitigate the vulnerability of the backhaul against fiber cuts, we introduce different advanced protection techniques. Accounting for the given conditions of the backhaul in terms of delay and reliability, we present a distributed load-balancing algorithm for user association in FiWi-LTE HetNets. The proposed algorithm is analyzed and evaluated numerically by comparing its performance with state-of-the-art alternative approaches in terms of average delay, blocking probability, average achievable throughput, and service interruption percentage. The obtained results demonstrate that our algorithm outperform its counterparts in terms of delay and service interruption percentage, while its average achievable throughput is the same as that of a backhaul-unaware alternative solution. In addition, the blocking probability of the proposed backhaul-aware load-balancing method is shown to be higher than that of backhaul-unaware ones.

Advances in Cooperative Single-Carrier FDMA Communications: Beyond LTE-Advanced

Abstract: In this paper, we focus our attention on the cooperative uplink transmissions of systems beyond the LTE-Advanced initiative. We commence a unified treatment of the principle of single-carrier frequency-division multiple-access (FDMA) and the similarities and dissimilarities, advantages, and weakness of the localized FDMA, the interleaved FDMA, and the orthogonal FDMA systems are compared. Furthermore, the philosophy of both user cooperation and cooperative single-carrier FDMA is reviewed. They are investigated in the context of diverse topologies, transmission modes, resource allocation, and signal processing techniques applied at the relays. Benefits of relaying in LTE-Advanced are also reviewed. Our discussions demonstrate that these advanced techniques optimally exploit the resources in the context of cooperative single-carrier FDMA system, which is a promising enabler for various uplink transmission scenarios.

Mobility load balancing aware radio resource allocation scheme for LTE-Advanced cellular networks

Abstract: Mobility load balancing (MLB) is widely used to address the uneven load distribution problem. The basic idea is that a hot-spot cell selects less-loaded neighbouring cells as assistant cells, and thenshiftsitsedge users to assistant cells via the handover region adjustment. However, shifted users receive the reduced signal power after MLB, which may result in the poor link quality problem for shifted users. In order to deal with this problem, this paper proposes a mobility load balancing aware radio resource allocation (MLBRRA) scheme. In the MLBRRA scheme, the assistant cell jointly considers the MLB factor of the shifted user and that of the hot-spot cell, as well as the proportional fairness scheduling factor. More specifically, the assistant cell preferentially allocates radio resources to shifted users, which are suffering poor link quality or previously served by a hot-spot cell with large handover region. Simulation results show that the proposed MLBRRA scheme can effectively deal with the poor link quality problem in terms of handover failure and call dropping. The proposed scheme can also reduce the call blocking probability.

Resource Allocation Strategies for Network-Coded Video Broadcasting Services Over LTE-Advanced

Abstract: Video service delivery over 3GPP Long Term Evolution-Advanced (LTE-A) networks is gaining momentum with the adoption of the evolved Multimedia Broadcast Multicast Service (eMBMS). In this paper, we address the challenge of optimizing the radio resource allocation process so that heterogeneous groups of users, according to their propagation conditions, can receive layered video streams at predefined and progressively decreasing service levels matched to respective user groups. A key aspect of the proposed system model is that video streams are delivered as eMBMS flows that utilize the random linear network coding (NC) principle. Furthermore, the transmission rate and NC scheme of each eMBMS flow are jointly optimized. The simulation results show that the proposed strategy can exploit user heterogeneity to optimize the allocated radio resources while achieving desired service levels for different user groups.

Macro-assisted data-only carrier for 5G green cellular systems

Abstract: As the commercial operation of 4G systems is speeding up worldwide to meet the increasingly explosive growth of mobile Internet in the 2020 era, a great many R&D efforts targeting the next generation wireless systems (5G) have been launched. With densely deployed small cells in a heterogeneous network, the excessive signaling overhead of conventional carrier design greatly degrades system performance. A new carrier designed for small cells in the next generation system will be highly beneficial toward a green communication network. In this article, we propose a macro-assisted data-only carrier for future 5G networks from a green prospective. With the help of macro base stations, control channel overhead, and cell-specific reference signals for small cells can be minimized to achieve a pure-data carrier. Under this architecture, key procedures are designed including small cell identification and access, synchronization, hand over, and small cell sleeping. Furthermore, to evaluate the potential of our proposed scheme, a complete system and link-level simulation platform according to the current 3GPP LTE standard is built. The simulation results show that our proposed systems, achieving significant performance enhancement of signaling overhead, can lead to more than 17 percent throughput improvement and 90 percent energy efficiency gain over the current LTE HetNet with on-off strategy implemented. The proposed scheme appears to be highly attractive as part of the future 5G green mobile networks.

LTE with listen-before-talk in unlicensed spectrum

Abstract: We consider the adoption of listen-before-talk (LBT) for Long Term Evolution (LTE) in unlicensed spectrum, which is currently under discussion in the 3rd Generation Partnership Project (3GPP). The first and foremost task to be done to allow LTE to use unlicensed spectrum is to study the coexistence with incumbent system, such as the Wireless Local Area Network (WLAN). In our study, we observe that a proper coexistence mechanism is imperative especially when both LTE Evolved Node Bs (eNBs) and WLANs are located outdoor. The outdoor deployment scenario is considered by the next generation WLAN, the IEEE 802.11ax, with high importance. The implementation of LBT in LTE plays an effective role in this scenario in balancing the performance between LTE and WLAN. In the conventional scenario where WLANs are located indoor and LTE eNBs are located outdoor, a plain coexistence without additional mechanism could be acceptable due to high penetration loss of outdoor walls.

Medium access design for LTE in unlicensed band

Abstract: In this paper, a medium access protocol suitably adapted for the operation of Long term evolution (LTE) in unlicensed band (LTE-U) is proposed. The MAC design considers the impact of LTE-U on the devices operating in unlicensed band, such as WiFi and legacy LTE. The LTE-U design differences from the legacy LTE system, an inherently a synchronized, tightly controlled system are explored. The performance of LTE-U is studied via a detailed system level simulator implementation and 3GPP simulation test scenarios. We show that our proposed MAC design enables high throughput in unlicensed band and achieves co-existence with the incumbent systems. Moreover, the use of channel reservation mechanisms is shown to improve LTE-U cell edge performance.

Enabling Cooperative Relaying VANET Clouds Over LTE-A Networks

Abstract: This paper addresses the area of heterogeneous wireless relaying vehicular clouds. We devise an advanced vehicular relaying technique for enhanced connectivity in densely populated urban areas. We investigate the performance of a transmission scheme over a Long-Term Evolution-Advanced (LTE-A) network where vehicles act as relaying cooperating terminals for a downlink session between a base station and an end-user. The abundance of moving vehicles, operating in an ad hoc fashion, can eliminate the need for establishing a dedicated relaying infrastructure. However, the associated wireless links in vehicular clouds are characterized by a doubly selective fading channel; this causes performance degradation in terms of increased error probability. Hence, we propose a precoded cooperative transmission technique to extract the underlying rich multipath–Doppler-spatial diversity, which is a relay selection scheme to take advantage of the potentially large number of available relaying vehicles. We further contribute by the derivation of a closed-form error rate expression, diversity gain, and outage expressions and introduce our derived performance unconditional expressions as a benchmark to assess our analysis and future research studies of such an approach. Our analytical and simulation results indicate that significant diversity gains and reduced error rates are achievable. In addition, there is a noticeable reduction in the required transmitting power compared with traditional transmission schemes, as well as an increase in distance coverage.

High-capacity mobile fronthaul supporting LTE-advanced carrier aggregation and 8×8 MIMO

Abstract: We demonstrate a SCM-PON mobile fronthaul architecture supporting 4+G cell sites with 3 RRHs, 5 aggregated carriers, and 8×8 MIMO (60×20MHz per λ) using 2-GHz-bandwidth optical components with first demonstration of complete RF signal processing.

Management architecture for location-aware self-organizing LTE/LTE-a small cell networks

Abstract: This article proposes a novel architecture for next-generation cellular networks in indoor scenarios. The objective of this model is to support SON mechanisms based on the knowledge of the user equipment location in a small cell network, the use of such information being a key enabler for advanced SON methods. The defined design is the basis for systems providing innovative location-aware SON techniques that make use of user localization in medium/large indoor areas (e.g., malls or corporate buildings). The functional and physical characteristics of this architecture and their technical implications are analyzed. Proposed innovations to generic mobile architecture are described as well as specific implementation for LTE/LTE-A standards. Interoperability with standard management systems and localization services, congestion avoidance, and data offloading are the key drivers of the design. Finally, the capabilities of the proposed architecture are demonstrated through the performance analysis of a simple key use case for location-aware self-optimization.