LTE-Advanced Networks Research Articles

Dynamic slot-based carrier scheduling scheme for downlink multimedia traffic over LTE advanced networks with carrier aggregation

Carrier aggregation (CA) in long-term evolution advanced (LTE-A) networks is a promising tool for providing bandwidth extension for high data rate communication. In CA, the efficient scheduling of carriers has imposed a new challenge in the design of delay-sensitive carrier scheduling for mobile multimedia applications. In this paper, a new dynamic slot-based carrier scheduling scheme has been proposed for efficient resource allocation to support the quality of service (QoS) of mobile traffic over CA transmission. The key idea of this scheduling is the allocation of slots for each component carrier based on the queue state information, taking into consideration the priority based on the delay requirements of individual mobile multimedia traffic. Two different cases of the scheduler with and without priority are implemented to facilitate the performance comparison. The simulation results show that the proposed scheme provides better spectrum utilization, throughput, and delay performance than the existing scheduling scheme and improves delay-sensitive mobile traffic QoS.

Specific buffer-aided full duplex relaying over LTE advanced networks

Full duplex relaying is an emerging technique to transmit and receive simultaneously at the same frequency for enhancing the attainable spectral efficiency in long term evolution advanced (LTE-A) network. The adoption of buffering over relay network outperforms and achieves better outage probability than the conventional relaying. In case of full duplex relaying (FDR) both transmission and reception are happening in same orthogonal channels, the increase in buffer length and higher delay deteriorates the system quality of service (QoS). To achieve both spectral efficiency and QoS, full duplex relay with the separate buffers for receiving and re-transmitting is proposed. The optimal trusted relay selection scheme is incorporated for maximising the security with effective signal-to-interference and noise ratio, which significantly improves the relaying transmission and further Tabu search-based metaheuristic algorithm is used for dealing with the trusted relay selection problem. The performance of three models, i.e., FDR without buffer-aided (conventional FDR), FDR with general buffer and FDR with specific buffer is investigated and compared in terms of outage probability and throughput. The simulation results revealed that the proposed FDR with specific buffer-aided scheme provides better performance compared with other FDR methods.

Gateway-assisted two-stage radio access for machine type communication in LTE-Advanced network

In Long Term Evolution-Advanced (LTE-A) network, Machine Type Communication (MTC) provides random access-based communication for automation applications. One of the most critical issues in MTC is the emergence of large number of MTC devices which may send requests to the base station simultaneously, and incur severe collision at the base station. When collision occurs, the data delivery fails, and the message delay accumulates.In this paper, we propose a gateway-assisted two-stage (GATS) radio access scheme to alleviate collision for delay-tolerant MTC applications. In GATS, MTC devices are divided into several groups, where random access in each group (as the first stage) is controlled by a device called MTC gateway. Collision of random access to the base station (as the second stage) is then effectively alleviated. Then we propose analytical model and simulation model to investigate the performance of GATS in terms of utilization of random access slots, access success probability and average message delay. Simulation results show that, by sacrificing a little message delay, GATS scheme significantly improves access success probability. Besides, when the group number increases, the delay becomes smaller.

A Moving Direction and Historical Information Assisted Fast Handover in LTE-A

Handover is one of the critical features in mobility management of Long Term Evolution Advanced (LTE-A) wireless systems. It allows the User Equipment (UE) to roam between LTE-A wireless networks. LTE-A is purely on hard handover, which may cause loss data if the handover is not fast. In this paper, an advanced technique proposed which combined between the current UE moving direction and its history information. Our proposed tracks the UE positions to discover its direction. When the UE is being near to handover area the UE starts searching in its history to return back the target cell. If the UE trajectory does not exist in its history then the UE and its serving cell start searching for target cell through using cosine function in order to select target cell. Our proposed technique is expected to increase the throughput, reduce the packet delay and loss, and reduce the frequent handovers.

Assigning eNode B to Switches in LTE Advanced Network by an Approach Genetic

Assigning eNode B to Switches in LTE Advanced Network by an Approach Genetic

Towards Future Low Exposure Mobile Cellular Networks

Explosive growth of different type of wireless networks in the last decade has raised an issue of influence of electromagnetic fields originating from radio frequencies to human health. Thus, more and more researchers working on the solutions for the next generation wireless communication systems now have in mind the necessity of keeping the level of radiated power on the minimum level necessary for achieving the required performances. In this paper we analyze solutions for human exposure reduction in dual-hop Orthogonal Frequency Division Multiplexing (OFDM) based decode-and-forward (DF) relay systems, as this type of relay system is adopted for LTE-Advanced networks, also denoted as 4G. In our approach we seek for the solutions that keep the certain performance metric, i.e. system capacity in this analysis, on the same level like in baseline OFDM DF relay system, but attain exposure reduction from relay station (R) on downlink (DL). In one of the considered solutions, R station, having more than one antenna for DL communication, implements transmit antenna selection (TAS) on subcarrier basis, jointly with ordered subcarrier mapping (SCM). TAS solution assumes that on each subcarrier position, the transmit antenna having the best subcarrier channel transfer function is chosen. Ordered SCM is a technique where subcarriers from the first hop are mapped to corresponding subcarriers on the second hop in accordance to their instantaneous signal-to noise ratios. It is proven to be a mapping scheme that maximizes the achievable capacity in OFDM based DF relay systems, enabling bit error rate improvement at the same time. Besides this solution, we analyze the level of human exposure reduction in the cases where only SCM technique is implemented at R, as well as where only TAS is implemented. We have developed a simulation model for assessing the level of human exposure to EMF, with included real-case simulation parameters given in LTE-Advanced relay reference scenario. In this way, we have obtained and analyzed data on the level of human exposure reduction attained with the proposed solutions in indoor and outdoor environment, and for the different positions of end-users relative to R station.

Novel Design of Optimal Spectrum Sharing for Cognitive Radio-Enabled LTE-A Multi-Cell Networks

For long term evolution-advanced (LTE-A) system, carrier aggregation (CA) allows LTE evolved Node B (eNB) and user equipment (UE) to access idle frequency spectrum to serve continuously growing traffic demands. To efficiently enhance network throughput, the concept of cognitive radio (CR) is adopted for LTE-A system to dynamically access opportunistic spectrum not occupied by primary system. Under the consideration of limited feedback system, the partially observable Markov decision process (POMDP) is applied in this paper to estimate the channel occupancy information (COI) on shared spectrum by partially sensing the frequency carriers. A POMDP-based spectrum sharing (POSS) scheme is then proposed to realize throughput maximization via the designs of contention mechanism and resource allocation policy according to the partially observable COI, channel state information, and number of contending cells in the network. Compared with the exhaustive search, the proposed approach can achieve optimal performance gain with lower computational complexity, which is proved to be a linear time algorithm. Numerical results illustrate that the proposed POSS protocol can effectively improve system throughput on shared spectrum for the LTE-A networks.

A Review of Heterogeneous Resource Allocation in LTE-A based Femtocell Networks with CQI Feedback

Background/Objectives: The Long-Term Evolution- Advanced (LTE-A) based heterogeneous networks focus on the Femto based cell deployment. These Femto cells will benefit the customers and service providers in term of network coverage and spectral efficiency. In such networks, optimal means of resource allocations is the major concern. Methods/Statistical Analysis: This paper reviews a detail study of resource allocation in Femto cell based LTE-A networks. In addition, a resource allocation strategy is suggested by means of Heterogeneous Channel Quality Index (CQI) based Scheduling Techniques (HCBST). It makes use of an indexed adaptive modulation and coding technique by referring the various CQI parameters. Findings: The HCBST algorithm is implemented by analyzing various scheduling technique at Femto and Marco base stations. The proposed resource allocation strategy is implemented by means of two scenarios, namely, Femto without node mobility and Femto with node mobility. Application/Improvements: The proposed HCBST system with modified largest weight delay first with CQI at Macro cell and Exponential with CQI at Femto cell (ML-EXP-CQI) based scheduling display 1.1879% and 2.85% better in term of throughput and spectral efficiency, respectively, as compared to existing scheduling algorithm..

General expressions for downlink signal to interference and noise ratio in homogeneous and heterogeneous LTE-Advanced networks

The interference is the most important problem in LTE or LTE-Advanced networks. In this paper, the interference was investigated in terms of the downlink signal to interference and noise ratio (SINR). In order to compare the different frequency reuse methods that were developed to enhance the SINR, it would be helpful to have a generalized expression to study the performance of the different methods. Therefore, this paper introduces general expressions for the SINR in homogeneous and in heterogeneous networks. In homogeneous networks, the expression was applied for the most common types of frequency reuse techniques: soft frequency reuse (SFR) and fractional frequency reuse (FFR). The expression was examined by comparing it with previously developed ones in the literature and the comparison showed that the expression is valid for any type of frequency reuse scheme and any network topology. Furthermore, the expression was extended to include the heterogeneous network; the expression includes the problem of co-tier and cross-tier interference in heterogeneous networks (HetNet) and it was examined by the same method of the homogeneous one.

Dynamic Cooperative Base Station Selection Scheme for Downlink CoMP in LTE-Advanced Networks

Coordinated Multi-Point (CoMP) transmission is a technique proposed to enhance the spectral efficiency and system throughput in an interference limited cellular networks. In CoMP joint processing (JP) scheme multiple base stations (BSs) are coordinately transmit data streams to each user. As more than two base stations are involved, abundant spatial resources are exploited and more backhaul spectrum for JP cooperation is required. The backhaul architecture for CoMP JP is crucial to provide low latency, unlimited capacity, less power consumption, and perfect synchronization among the BSs. However, satisfying all these constraints is impossible as the number of cooperative BSs increases for each user. In this paper, a dynamic cooperative base station selection scheme is proposed to reduce the backhaul load for CoMP user by selecting the appropriate number of coordinated BSs from the CoMP cluster to ensure the certain quality of service (QoS). In particular, for cell edge user the number of cooperative BSs per user has been selected in order to achieve reduced overhead and the allocation of backhaul capacity is performed under the max---min fairness criterion. Simulation results show that the proposed selection scheme achieves significant performance improvement than other transmission modes in terms of the average sum rate per backhaul use and minimal total power consumption.

Effective resource block allocation procedure for quality of service provisioning in a single-operator heterogeneous LTE-A network

We consider the problem of resource block (RB) allocation in the integrated pico/macrocell Long Term Evolution - Advanced (LTE-A) network. It is assumed that the network is controlled by a single service provider (SP) and all the operation of the picocells is coordinated with a macro-network. To improve the quality of service (QoS) for end-to-end applications, we take into account the individual traffic demands of the users and allocate the RBs to minimize the sum of user utilities which are expressed in terms of the size of their queues. The formulated RB allocation problem belongs to the family of the multiple knapsack problems (MKPs) and, therefore, it is non-deterministic polynomial time (NP) hard in the strong sense. To reduce the complexity of this problem, we propose a simple heuristic technique to find the suitable (but not necessarily optimal) solution. The proposed RB allocation procedure requires only two additional signalling steps (necessary to maintain the coordination among different cells) and, therefore, its impact of the control signalling overhead is neglectable. It was shown (using OPNET-based simulations) that the proposed technique has low complexity, fast solution time, and shows improved performance when compared to other relevant schemes.

Self-organized Dynamic FFR Resource Allocation Scheme for LTE-Advanced Relay Based Networks

Inter-Cell Interference (ICI) from neighboring cells is a major challenge that severely degrade the performance of Orthogonal Frequency Division Multiple Access based cellular mobile systems, particularly for cell-edge users. An efficient technique to mitigate ICI is interference coordination. The most commonly Inter-Cell Interfere Coordination technique is Fractional Frequency Reuse (FFR). Furthermore in order to effectively improve cell-edge performance in terms of coverage extension and throughput, the 3rd Generation Partnership Project introduced the use of relays in Long Term Evolution-Advanced (LTE-A) networks to achieve self-backhauling of radio signals between Evolved NodeBs (eNBs) and UEs. This paper introduces a Self-Organized Dynamic FFR Resource Allocation scheme (SODRA-FFR) which dynamically allocates frequency resources to cell inner and outer regions in relay based LTE-A networks to improve cell edge performance and maximize fairness among UEs. In this scheme, the downlink frequency resources are dynamically allocated to cell inner and outer regions and the outer region frequency resources are dynamically distributed between eNB and relay stations in each cell based on coordination between neighboring eNBs and relay stations through a message passing approach over LTE-X2 interfaces. The performance of the proposed SODRA-FFR scheme without and with relays is evaluated using MATLAB simulations and compared with different combinations of frequency resources allocation to cell inner and outer regions as well as with other frequency reuse scheme (i.e., frequency reuse-1 and frequency reuse-3). The results show that the proposed SODRA-FFR scheme improves cell-edge performance and achieves high degree of fairness among UEs compared to reference resource allocation schemes. The results also show that the proposed SODRA-FFR scheme with RSs improves the fairness performance by 30 and 13 % compared to that of frequency reuse-1 and frequency reuse-3 schemes, respectively. In addition, the proposed SODRA-FFR scheme with RSs achieves 55 and 26 % increase in cell-edge throughput compared to that of frequency reuse-1 and frequency reuse-3 schemes, respectively.

A heuristic design for the uplink scheduling in LTE-A networks

Long Term Evolution advanced (LTE-A) is recognized as the main technology towards the broadband wireless access for emerging network services. In LTE, single carrier frequency division multiple access (SC-FDMA) is applied as the transmission technology for uplink traffic. This paper proposes a novel scheme to schedule the uplink traffic of both LTE and LTE-A UE in LTE-A network environment. The proposed scheme considers the localized subcarrier by properly using the Gale-Sharply concept, quality of services (QoS), and the selection of component carriers (CC) for LTE-A UE. The simulation results show that the proposed scheme can effectively schedule radio resource to UE according to their types and desired QoS.

ANDSF-Assisted vertical handover decisions in the IEEE 802.11/LTE-Advanced network

To address the challenging issues of energy-efficiency and seamless connectivity in heterogeneous networks, 3GPP and IEEE have recently incorporated several architectural and functional enhancements to the baseline operation of their standards for cellular and wireless local area network access, respectively. Based on the 3GPP Access Network Discovery and Selection Function (ANDSF) as well as the advanced measurement capabilities provided by the IEEE 802.11-2012 and the 3GPP Long Term Evolution–Advanced (LTE-A) Standards, we propose an ANDSF-assisted energy-efficient vertical handover decision algorithm for the heterogeneous IEEE 802.11-2012 / LTE-A network. The proposed algorithm enables multi-mode mobile terminals to select and associate with the network point of attachment that minimizes the average overall power consumption at the mobile terminal and guarantees a minimum supported quality of service for its ongoing connections. System-level simulations demonstrate the performance of the proposed algorithm and compare it against that of other competing solutions.

Ambulance Telemedicine Using Mobile Smart Devices Connected Through an LTE-A Network

Background and Objectives: With the development of communications technologies, media transmitting could be possible in real time without having space and time limitations. In this study, we evaluate the feasibility of using mobile smart devices to exchange data between a moving ambulance and a hospital using LTE-A (long term evolution-advanced) network technology. Materials and Methods: In the evaluation, a server and monitoring system were used to link four mobile devices simultaneously via a commercial LTE-A network. The proposed system was designed to monitor the status of a patient being transported in an ambulance, using mobile smart devices communicating via a commercial LTE-A network, in real time without delays or video image break up. Results: This was achieved by decreasing image transmission overloads for each channel and increasing the compressibility of transmissions to the server. Based on these techniques, captured media could be transmitted without data loss using a bandwidth of 512Kbps. Conclusions: Collectively, the study demonstrates that efficient, real-time telemedicine in ambulance emergency scenarios can be realized by using mobile smart devices connected through an LTE-A network. (J Clinical Otolaryngol 2016;27:112-120)

Joint Network Channel Fountain Schemes for Machine-Type Communications Over LTE-Advanced

Machine-type communications (MTC) also known as machine-to-machine (M2M) communications over long-term evolution-advanced (LTE-A) networks with ubiquitous coverage and global Internet working is expected to constitute a significant part of the Internet of Things (IoT) paradigm. However, there are paramount challenges and active research activities to accommodate M2M communications over LTE-A network without sacrificing the quality of human-based services. Among them the performance of M2M communications in LTE advanced relay network has not been fully investigated yet. In particular, LTE/LTE-A uses turbo codes as the forward error correction (FEC) mechanism in the physical layer. Since turbo codes are fixed rate codes, an automatic repeat request (ARQ) is sent to the sender when the receiver fails to recover complete packet that results in packet failure and waste of radio resources. In this paper, to combat the detrimental effects of wireless fading channel, we propose a set of joint network and fountain coding (JNFC) schemes for reliable uplink transmission between M2M devices and evolved NodeB (eNB). Specially, we consider clustered heterogeneous M2M networks, where cluster heads (CHs) transmit to eNB directly or by the help of relays. Numerical results are presented to demonstrate the performance of the proposed schemes over type I and type II relay-enhanced LTE-A networks. It shows that in type I relay enhanced networks, JNFC with space time block codes (JNFC-STBC) outperforms the direct transmission with relays (DTRs) and in type II enhanced networks, JNFC with robust soliton distribution (JNFC-RSD) outperforms JNFC with random linear network coding (JNFC-RLNC) in a variety of metrics.

Joint Resource Allocation and Relay Selection in LTE-Advanced Network Using Hybrid Co-Operative Relaying and Network Coding

The problem of joint resource allocation and relay selection is studied for bidirectional LTE-advanced relay networks. The bidirectional communication between user equipment (UE) and eNodeB (eNB) is performed via direct transmission, co-operative relaying (CoR), or a combination of network coding (NC) and CoR (NC/CoR). In this paper, an enhanced three-time-slot per cycle time-division duplexing (TDD) scheme is proposed for LTE-Advanced frame architecture to accommodate a hybrid transmission scheme. More specifically, we formulate the problem of joint resource assignment, relay selection, and bidirectional transmission scheme selection as a combinatorial optimization problem with the objective to maximize the total product of backlog and rate (back-pressure principle). Two approaches are considered to solve our combinatorial optimization problem. First, a graph-based framework is proposed in which the problem is transformed into a maximum weighted Clique problem (MWCP). In addition, our problem is also transformed into a three-dimensional assignment problem (3DAP) which is solved using a hybrid ant colony optimization (ACO) algorithm. Using simulations, it is concluded that the hybrid transmission scheme outperforms all conventional nonhybrid schemes. Moreover, the simulation results confirm that while the two proposed solutions provide similar results, the ACO algorithm is faster due to its lower complexity.

An Optimized and Distributed Data Packet Forwarding Scheme in LTE/LTE-A Networks

Long-term evolution (LTE)/LTE-advanced (LTE-A) networks have recently introduced a data packet forwarding scheme between evolved node Bs (eNBs) to reduce the signaling overhead and the delay incurred in the data path switching scheme, which is a baseline handover scheme in LTE/LTE-A networks. Even with the data packet forwarding scheme, if the length of the forwarding chain is set inappropriately, the data packet forwarding scheme suffers from the degraded throughput. To attain the optimal handover performance in terms of throughput and delay and reduce the signaling overhead, we propose an optimized and distributed data packet forwarding scheme where the optimal length of the forwarding chain is obtained by a Markov decision process (MDP). In addition, a low-complexity value iteration algorithm is devised to solve the optimality equation of MDP in a more practical manner. Real trace-driven evaluation results demonstrate that the proposed scheme determines the optimal length of the forwarding chain adaptively to the applications' quality-of-service (QoS) requirements and reduces the signaling overhead and delay while achieving higher throughput in diverse environments.

Nframe: A privacy-preserving with non-frameability handover authentication protocol based on (t, n) secret sharing for LTE/LTE-A networks

Seamless handover between the evolved universal terrestrial radio access network and other access networks is highly desirable to mobile equipments in the long term evolution (LTE) or LTE-Advanced (LTE-A) networks, but ensuring security and efficiency of this process is challenging. In this paper, we propose a novel privacy-preserving with non-frameability handover authentication protocol based on (t, n) secret sharing to fit in with all of the mobility scenarios in the LTE/LTE-A networks, which is called Nframe. To the best of our knowledge, Nframe is the first to support protecting users’ privacy with non-frameability in the handover process. Moreover, Nframe uses pairing-free identity based cryptographic method to secure handover process and to achieve high efficiency. The formal verification by the AVISPA tool shows that Nframe is secure against various malicious attacks and the simulation result indicates that it outperforms the existing schemes in terms of computation and communication cost.

Scheduling Impact on the Performance of Relay-Enhanced LTE-A Networks

This paper studies the performance of two traditional schedulers, namely, proportional fair (PF) and round robin (RR), in the context of relay-enhanced Long-Term Evolution Advanced (LTE-A) networks. These two schedulers are natural candidates for implementation in relay nodes (RNs), and following the results obtained in single-hop networks, mobile operators could be tempted to adopt PF because of the good tradeoff it offers between cell capacity and fairness. Based on a statistical throughput evaluation model, we show that this is not necessarily the right option. The number of RNs, their locations in the cell, and backhaul link quality have a decisive influence on scheduler choice. In some scenarios, it is even not desirable to deploy relays as they degrade the network performance compared with the no-relay case. For the purpose of performance evaluation, we develop a realistic and computationally tractable statistical network model that takes into account fast fading, multiple interferers, cell range expansion bias, backhaul link quality, and traffic load. We also propose optimization of the radio frame structure and a suboptimal RN placement scheme to fairly compare RR and PF.