LTE-Advanced Heterogeneous Networks Research Articles

Heterogeneous networks: Fair power allocation in LTE-A uplink scenarios.

Effective management of radio resources and service quality assurance are two of the essential aspects to furnish high-quality service in Long Term Evolution (LTE) networks. Despite the base station involving several ingenious scheduling schemes for resource allocation, the intended outcome might be influenced by the interference, especially in heterogeneous scenarios, where many kinds of small cells can be deployed under the coverage of macrocell area. To develop the network of small cells, it is essential to take into account such boundaries, in particular, mobility, interference and resources scheduling a strategy which assist getting a higher spectral efficiency in anticipate small cells. Another challenge with small cellular network deployment is further analyzing the impact of power control techniques in the uplink direction for the network performance. With that being said, this article investigates the problem of interference in LTE-advanced heterogeneous networks. The proposed scheme allows mitigation inter-cell interference through fractional self-powered control performed at each femtocell user. This study analyzes a scheme with optimum power value that provides a compromise between the served uplink signal within unwanted interference plus noise ratio to enhance spectral efficiency in terms of throughput. In particular, the maximum transmit power for user equipment in uplink direction should be reviewed for small cells as a major contributor to the interference. The simulation results showed that the proposed fractional power control approach can outperform the traditional power control employed as a full compensation mode in small cell uplinks.

Delay-Sensitive Network Selection and Offloading in LTE-A and Wi-Fi Heterogeneous Networks

LTE-Advanced (LTE-A) offloading is concerned about alleviating traffic congestion for the LTE-A network, which includes the core network and the radio access network (RAN). Due to the scarcity of the radio resource, offloading for the LTE-A RAN is more critical, for which an efficient way is to integrate Wi-Fi with LTE-A to form a heterogeneous RAN environment. An LTE-A UE (User Equipment) with the wi-fi interface can therefore access the Internet via an LTE-A base station of Evolved Node B (eNB) or a wi-fi Access Point (AP). In this paper, wireless network selection for UEs with delay-sensitive traffic in the heterogeneous RAN of LTE-A and wi-fi is addressed. Based on the queueing model of M/G/1, a novel network selection and offloading scheme, namely Delay-Sensitive Network Selection and Offloading (DSO), is proposed. The average system time at LTE-A eNBs and wi-fi APs calculated according to M/G/1 is used for network selection as well as offloading operations in DSO. The benefit of DSO in terms of satisfying the delay budget of UEs and load balancing is demonstrated by the simulation study.

Power Control Schemes for Interference Management in LTE-Advanced Heterogeneous Networks

The issue of inter-cell interference with the co-tier and cross-tier arises in LTE-A Heterogeneous networks when thelow power base station deployed in a huge number in the ultra-densities area. This problem is managed by RRM (Radio Resource Management)technique. RRM uses different algorithms, application, and parameters to avoid and mitigate co-channel and cross-channel interference. The main objective of the Radio Resource Management is to maximize the use of limited resources. It manages all the resources like power, frequency and time. The power control Radio Resource Management scheme is used to control the interference between Femto to Femtocells and Femto to Macrocells. These resources are regulated separately or in combination,the approach is called hybrid Radio Resource Management. In this paper various Power schemebased on Fixed, Constant Femto Base Station and Targeted SINR is used. These Powers control Scheme are applied to the networktopology with increment in the size of femto cell range and number of femto and macro userin increment order. The performance is analyzed on SINR, pathloss and throughput. The comparison results of in between Fixed, Constant Femto Base Station and Targeted SINR power schemeare shown in graphs. The result reflects that constant FBS scheme has outperformed in user increment scenario and range increment scenario.

Joint downlink resource allocation in LTE-Advanced heterogeneous networks

Long Term Evolution-Advanced (LTE-A) heterogeneous network constituted by macro cells and small cells has attracted wide attentions as a solution to the data surge problem in the developing wireless networks, e.g., 5G mobile communication systems, demanding for higher bandwidth and better quality. Taking also cognitive radio into account, we develop here a dynamic resource allocation algorithm for the downlink transmission which involves resource blocks, component carriers, modulation and coding schemes, and frequency partitions with an overall consideration. Specially, we consider not only to determine the multiple kinds of resources at each transmission time interval, but also to enforce the constraints specific to the LTE-A system with carrier aggregation. To this end, we conduct a mathematical programming model which involves nonlinear constraints on binary variables to formulate the stochastic optimization problem, and introduce a submodular-based greedy algorithm to resolve the high-dimensional NP-hard allocation problem involved. In addition, for the traffic and channel conditions to be time-varying in practice, our approach based on the Lyapunov drift-plus-penalty framework requires no prior knowledge of such information to alleviate the system overhead. Given that, the greedy allocation algorithm embedded is further used to guarantee the performance of allocation by means of submodularity. Finally, the numerical evaluation is conducted to verify our approach, revealing its performance benefits complementing the previous works that pay no special attention to the issues addressed here.

A dynamic CRE and ABS scheme for enhancing network capacity in LTE-advanced heterogeneous networks

With the ever-growing popularity of wireless multimedia services, wireless network base stations are increasingly likely to overload in high population density areas. An economical means exists for operators to establish more picocells in order to reduce the user traffic load on base stations and increase system capacity; however, inter-cell interference is a challenge in such heterogeneous networks. This study proposes a novel scheme that integrates dynamic cell range expansion (CRE) and dynamic almost blank subframe (ABS) schemes based on 3GPP R10 eICIC. The proposed scheme can automatically adjust the CRE bias value according to the cell traffic load, thereby ensuring that users have access to sufficient resources to transmit data when they are offloaded to a smaller cell. Furthermore, the proposed ABS scheme can determine the ABS ratio that yields the highest system capacity. The proposed CRE scheme ensures that offloaded users always have access to sufficient resources. The proposed CRE and ABS scheme can improve network system capacity by more than 13.9% of 3GPP R10 and 11.7% of the competing algorithm.

Cell Selection and Resource Allocation in LTE-Advanced Heterogeneous Networks

A LTE-advanced heterogeneous network consists of many macrocells, and within each macrocell, there can have many picocells and user equipments (UEs). A UE within a macrocell can request resource blocks (RBs) from either the macrocell or a picocell within the macrocell. In this paper, two optimal problems are defined for the association of UEs, RBs, and heterogeneous cells. We show that both problems are equivalent to a 0/1 knapsack problem and, therefore, can be solved in pseudo-polynomial time by dynamic programming. Based on above two optimal problems, we, then, propose a cell selection and resource allocation (CSRA) scheme to solve the problem of allocating a UE to its macrocell or to a picocell within the macrocell. The design goal of picocells is to unload the traffic for the macrocell. When there are available RBs and UEs within the picocell, the CSRA scheme offloads UEs to the picocell to release the most number of RBs for the macrocell. Only when there are not enough RBs within a picocell and there are available RBs within the macrocell, for load balancing, the CSRA scheme moves some UEs to the macrocell. The CSRA scheme stops whenever the picocell is not overloaded or the macrocell does not have available RBs. Simulation results show that our proposed scheme performs better than the cell range expansion scheme in terms of goodput, loss rate, and delay.

Power efficient and coordinated eICIC-CPC-ABS method for downlink in LTE-advanced heterogeneous networks

In 2020, mobile data traffic is expected to be a thousand times more than the current scenario. In order to handle this increased capacity, improvement in spectral efficiency is one of the challenging task. In long term evolution (LTE) and long term evolution advanced (LTE-A), deployment of small cell base station (SBS) and hotspot are step to handle the increased capacity of the network and quality of service. In this scenario, the SBSs are deployed under the coverage of macro cell base station (MBS). Neighbour MBS and neighbour SBS create intra and inter-cell interference to the users in the overlapped region. In order to mitigate interference, coordination between base stations is required. In this paper, we propose an enhanced intercell interference coordination by considering centralized processing controller with almost blank subframe (eICIC-CPC-ABS) for heterogeneous networks (HetNets). Centralized processing controller (CPC) at MBS decides the radio resource allocation of each SBSs based on user location. The dynamic frequency and reduced transmission power depend on the user locations. The analytical and simulation results demonstrate that the proposed method (eICIC-CPC-ABS) provides higher signal to interference plus noise ratio (SINR) compared to existing models: inter cell interference coordination (ICIC) and enhanced inter cell interference coordination (eICIC). The proposed method provides significant savings in transmitting power. Additionally, it increases the network capacity and coverage.

Toward 5G: FiWi Enhanced LTE-A HetNets With Reliable Low-Latency Fiber Backhaul Sharing and WiFi Offloading

To cope with the unprecedented growth of mobile data traffic, we investigate the performance gains obtained from unifying coverage-centric 4G mobile networks and capacity-centric fiber-wireless (FiWi) broadband access networks based on data-centric Ethernet technologies with resulting fiber backhaul sharing and WiFi offloading capabilities. Despite recent progress on backhaul-aware 4G studies with capacity-limited backhaul links, the performance-limiting impact of backhaul latency and reliability has not been examined in sufficient detail previously. In this paper, we evaluate the maximum aggregate throughput, offloading efficiency, and in particular, the delay performance of FiWi enhanced LTE-Advanced (LTE-A) heterogeneous networks (HetNets), including the beneficial impact of various localized fiber-lean backhaul redundancy and wireless protection techniques, by means of probabilistic analysis and verifying simulation, paying close attention to fiber backhaul reliability issues and WiFi offloading limitations due to WiFi mesh node failures as well as temporal and spatial WiFi coverage constraints. We use recent and comprehensive smartphone traces of the PhoneLab data set to verify whether the previously reported assumption that the complementary cumulative distribution function of both WiFi connection and interconnection times fit a truncated Pareto distribution is still valid. In this paper, we put a particular focus on the 5G key attributes of very low latency and ultra-high reliability and investigate how they can be achieved in FiWi enhanced LTE-A HetNets. Furthermore, given the growing interest in decentralization of future 5G networks (e.g., user equipment assisted mobility), we develop a decentralized routing algorithm for FiWi enhanced LTE-A HetNets.

Inter-Cell Interference Mitigation in LTE-Advanced Heterogeneous Networks by Dynamic Subframes Assignment Guaranteeing Fairness

Inter-Cell Interference Mitigation in LTE-Advanced Heterogeneous Networks by Dynamic Subframes Assignment Guaranteeing Fairness

Review of Adaptive Cell Selection Techniques in LTE-Advanced Heterogeneous Networks

Poor cell selection is the main challenge in Picocell (PeNB) deployment in Long Term Evolution- (LTE-) Advanced heterogeneous networks (HetNets) because it results in load imbalance and intercell interference. A selection technique based on cell range extension (CRE) has been proposed for LTE-Advanced HetNets to extend the coverage of PeNBs for load balancing. However, poor CRE bias setting in cell selection inhibits the attainment of desired cell splitting gains. By contrast, a cell selection technique based on adaptive bias is a more effective solution to traffic load balancing in terms of increasing data rate compared with static bias-based approaches. This paper reviews the use of adaptive cell selection in LTE-Advanced HetNets by highlighting the importance of cell load estimation. The general performances of different techniques for adaptive CRE-based cell selection are compared. Results reveal that the adaptive CRE bias of the resource block utilization ratio (RBUR) technique exhibits the highest cell-edge throughput. Moreover, more accurate cell load estimation is obtained in the extended RBUR adaptive CRE bias technique through constant bit rate (CBR) traffic, which further improved load balancing as against the estimation based on the number of user equipment (UE). Finally, this paper presents suggestions for future research directions.

The tactile internet: vision, recent progress, and open challenges

The advent of commercially available remote-presence robots may be the precursor of an age of technological convergence, where important tasks of our everyday life will be increasingly done by robots. A very low roundtrip latency in conjunction with ultra-high reliability and essentially guaranteed availability for control communications has the potential to move today’s mobile broadband experience into the new world of the Tactile Internet for a race with (rather than against) machines. To facilitate a better understanding of the Tactile Internet, this article first elaborates on the commonalities and subtle differences between the Tactile Internet and the Internet of Things and 5G vision. After briefly reviewing its anticipated impact on society and infrastructure requirements, we then provide an up-to-date survey of recent progress and enabling technologies proposed for the Tactile Internet. Given that scaling up research in the area of future wired and wireless access networks will be essential for the Tactile Internet, we pay particular attention to the latency and reliability performance gains of fiber-wireless (FiWi) enhanced LTE-Advanced heterogeneous networks and their role for emerging cloudlets, mobile-edge computing, and cloud robotics. Finally, we conclude by outlining remaining open challenges for the Tactile Internet.

Dual connectivity for LTE-advanced heterogeneous networks

Dual connectivity (DC) allows user equipments (UEs) to receive data simultaneously from different eNodeBs (eNBs) in order to boost the performance in a heterogeneous network with dedicated carrier deployment. Yet, how to efficiently operate with DC opens a number of research questions. In this paper we focus on the case where a macro and a small cell eNBs are inter-connected with traditional backhaul links characterized by certain latency, assuming independent radio resource management (RRM) functionalities residing in each eNB. In order to fully harvest the gain provided by DC, an efficient flow control of data between the involved macro and small cell eNBs is proposed. Moreover, guidelines for the main performance determining RRM algorithms such as UE cell association and packet scheduling are also presented. It is demonstrated how proper configuration of the proposed flow control algorithm offers efficient trade-offs between reducing the probability that one of the eNBs involved in the DC runs out of data and limiting the buffering time. Simulation results show that the performance of DC over traditional backhaul connections is close to that achievable with inter-site carrier aggregation (CA) and virtually zero-latency fronthaul connections, and in any case it is significantly higher compared to the case without DC.

An open framework for programmable, self-managed radio access networks

SON technologies have been a promising approach for simplified and automated RAN management. Currently, SON functions can be D-SON among the network elements or C-SON as part of the OSS/NMS. D-SON technology is typically provided by equipment vendors, while C-SON is provided by both third parties and equipment vendors. D-SON has high reactivity but is usually provided as black boxes with poor or no interoperability between different vendors and management systems, hence rendering their integration a challenging task. On the other hand, OSS/NMS-level SONs, although provided with a global network view, are limited to coarse time operation. In this work we apply SDN principles to the management of RANs and propose a software-defined SON (SD-SON) framework that tackles the shortcomings and combines the benefits of both approaches above, namely, high reactivity along with flexibility, programmability, and openness. The architectural components, implementation aspects, and advantages of the proposed SD-SON framework are described in detail. A proof-of-concept prototype of a programmable self-managed LTE-Advanced heterogeneous network is also presented.

Interference Alignment in Two-Cell LTE-Advanced Heterogeneous Networks

In this paper, we address the issue of interference alignment (IA) in a two-cell network and consider both inter-cell and intra-cell interferences. For cell one, a linear processing scheme is proposed to align the inter-cell interference to the same signal dimension space of intra-cell interference. For cell two, we propose a distributed interference alignment scheme to manage the interference from the nearby cell. We assume that the relay works in an amplify-and-forward (AF) mode with a half-duplex and MIMO relaying. We show that the composite desired and interfering signals aggregated over two time slots can be aligned such that the interfering signal is eliminated completely by applying a linear filter at the receiver. The precoding matrix of the relay is optimized jointly with the precoding matrix of the base station (BS). The number of data streams is optimized jointly for every user terminal (UT). The degree of freedom (DoF) performance of the proposed scheme as well as the conventional cooperation scheme are derived for multiple antennas at both base stations, relay station and user terminals. Simulation results show that the proposed alignment scheme can achieve a better DoF performance.

Backhaul-aware energy efficient heterogeneous networks with dual connectivity

In this paper, we consider backhaul-aware mechanisms for energy efficient operation of next generation heterogeneous wireless networks, with dense small cell deployments. We assume control and data plane separation based on the LTE-Advanced dual connectivity architecture. The mechanisms are evaluated using LTE-Advanced heterogeneous network scenarios, with varying levels of network densities, user traffic and cell load conditions. For comparison, conventional traffic offloading schemes based on small cell proximity and load are also evaluated. The performance results indicate significant energy saving (ES) gains for the backhaul-aware mechanism, depending on the backhaul technology used. Evaluations were also done on the impacts of user mobility, and for indoor and outdoor deployments of small cells. Trade-offs between user throughput and energy efficiency are evaluated, and using the considered mechanism, ES gains of up to 20 % is observed, without significant loss in throughput.

Optimal deployment of pico base stations in LTE-Advanced heterogeneous networks

As data traffic demand in cellular networks grows exponentially, operators need to add new cell sites to keep up; unfortunately, it is costly to build and operate macrocells. Moreover, it may not be possible to obtain the needed approvals for additional macrocell sites. Recently, the 3rd Generation Partnership Project (3GPP) introduced the concept of heterogeneous networks in Long Term Evolution (LTE) Release 10, where low-power base stations (BSs) are deployed within the coverage area of a macrocell to carry traffic. However, this new type of deployment can cause more severe interference conditions than a macro-only system, due to inter-cell interference; hence, enhanced inter-cell interference coordination (eICIC) has been actively discussed in LTE Release 10. Nevertheless, eICIC cannot completely eliminate interference and, to make matters worse, high-power transmissions of the reference signals from the BSs may increase the interference level. In this paper, we propose an algorithm for deploying low-power nodes within macrocell coverage areas in LTE heterogeneous networks, which aims to increase the system utility while minimizing the installation cost.

Service Self-Organization Based on SON in LTE-Advanced Heterogeneous Networks

Since global service providers consider seamless interworking with existing networks as the most important factor, it is most likely that LTE-Advanced of 3GPP is selected as international standard for 4G wireless communication. As such, we suggest SON based service self-organization which provides users with service continuity even when mobile users have terminal mobility and session mobility, and enable service providers to implement “heterogeneous multi-network of integrated” which guarantees better service in terms of wireless communication access, transmission speed, and Quality of Service (QoS). It is also expected to allow fast handover service such as VOD, and streaming in LTE-Advanced system. Moreover, this study could be conducted with various research institutions and manufacturers, leading joint research and technology transfer in the future.

A Dynamic Cell Range Expansion for LTE-Advanced Heterogeneous Networks

Deploying Pico cell Base Station (PBS) throughout a Macro cell layout is a promising solution to enhance system capacity and users throughput. However, the strong received power from Macro cell Base Station (MBS) makes the Pico cell areas narrow and limits cell splitting gain. Range Expansion (RE) is desirable to balance the network load between MBS and PBS by expanding the coverage, which subsequently increases cell splitting gains. However, more interference may be introduced if the bias value of RE is not set properly. In this paper, we propose a Dynamic Cell Range Expansion (DCRE) strategy that the bias value of RE is set dynamically according to the change of network environment. The proposed scheme aims to fulfill the resources utilization by RE scheme, and meanwhile improve the users performance of cell edge through cell load balancing method. Simulation results show that DCRE scheme can improve the network performance of cell edge, and increase the cell capacity and users throughput compared with the existing methods.

Dynamic bias setting for range extension in LTE-advanced macro-pico heterogeneous networks

In co-channel deployment of macro cell and pico cells, cell range extension (RE), a simple and typical cell association scheme, is introduced to achieve better load balancing and improve cell edge performance. In this article, a novel dynamic and distributed bias setting scheme is proposed for RE technique in macro-pico heterogeneous networks. In this strategy, the worst user throughput of each cell during an adjusting time interval T is obtained to change the bias values according to certain procedures, where an introduced indicator is used to freeze the possibility of increasing bias value if needed. Furthermore, silent state and coarse control process are employed to achieve low overheads and computational complexity. Simulation results show that the proposed scheme can greatly improve the cell-edge performance compared with the static bias setting strategies, while maintaining the overall cell performance at the same time.

Self-configuration and self-optimization in LTE-advanced heterogeneous networks

Self-organizing network, or SON, technology, which is able to minimize human intervention in networking processes, was proposed to reduce the operational costs for service providers in future wireless systems. As a cost-effective means to significantly enhance capacity, heterogeneous deployment has been defined in the 3GPP LTEAdvanced standard, where performance gains can be achieved through increasing node density with low-power nodes, such as pico, femto, and relay nodes. The SON has great potential for application in future LTE-Advanced heterogeneous networks, also called HetNets. In this article, state-of-the-art research on self-configuring and self-optimizing HetNets are surveyed, and their corresponding SON architectures are introduced. In particular, we discuss the issues of automatic physical cell identifier assignment and radio resource configuration in HetNets based on selfconfiguring SONs. As for self-optimizing SONs, we address the issues of optimization strategies and algorithms for mobility management and energy saving in HetNets. At the end of the article, we show a testbed designed for evaluating SON technology, with which the performance gain of SON algorithms is demonstrated.