Long Term Evolution Downlink System Research Articles

QoS-Aware Scheduling Algorithm Enabling Video Services in LTE Networks

The Long-Term Evolution (LTE) system was a result of the 3rd-Generation Partnership Project (3GPP) to assure Quality-of-Service (QoS) performance pertaining to non-real-time and real-time services. An effective design with regards to resource allocation scheduling involves core challenges to realising a satisfactory service in an LTE system, particularly with the growing demand for network applications. The continuous rise in terms of the number of network users has resulted in impacts on the performance of networks, which also creates resource allocation issues when performing downlink scheduling in an LTE network. This research paper puts forward a review of optimisation pertaining packet scheduling performance through the LTE downlink system by introducing a new downlink-scheduling algorithm for serving video application through LTE culler networks, and also accounts for QoS needs and channel conditions. A comparison of the recommended algorithms’ performances was made with regards to delay, throughput, PLR, and fairness by utilising the LTE-SIM simulator for video flow. On the basis of the outcomes obtained, the algorithms recommended in this research work considerably enhance the efficacy of video streaming compared against familiar LTE algorithms.

Effective Estimation of Integer Carrier Frequency Offset in LTE Downlink Systems With Symbol Timing Error

An effective integer carrier frequency offset (IFO) detection scheme is proposed in the long-term evolution downlink system without relying on the knowledge of the cell ID (CID) that is carried through the synchronization signal. To enable IFO detection without relying on the CID, the proposed IFO detection method utilizes the symmetric property of the synchronization signal, such as the primary synchronization signal (PSS) and the secondary synchronization signal (SSS). This design avoids the need to retrieve the CID that is carried by the PSS and the SSS at the IFO-matching stage. In addition to investigating the usefulness of the proposed IFO detection method, the probability of detection failure is theoretically calculated. The simulation results demonstrate that both the synchronization signals are effectively exploited for the robust detection of the IFO in the presence of non-negligible symbol timing error, where the conventional approaches show unsatisfactory performance.

RS Codes for Downlink LTE System over LTE-MIMO Channel

Nowdays, different applications require a modern generation of mobile communication systems; long term evolution (LTE) is a candidate to achieve this purpose. One important challenge in wireless communications, including LTE systems, is the suitable techniques of controlling errors that degrade system performance in transmission systems over multipath fading channels. Different forward Error correction (FEC) techniqes are required to improve the robustness of transmission channels. In this paper, Reed-Solomon (RS) codes were used with a downlink LTE system over a LTE-MIMO channel. This research contributes by combining RS codes that have low decoding complexity (by using hard decision decoding) with a LTE-MIMO channel to improve downlink LTE system performance. The results show that using RS codes clearly improves LTE system performance and thus decreases Bit Error Rates (BER) more than convolutional and turbo codes which have high decoding complexity. Lastly, the results show also extra improvements of downlink LTE system performance by increasing the number of antennas of the LTE-MIMO channel.

Channel Estimation Techniques over MIMO-OFDM System

The multiple input multiple output-orthogonal frequency division multiplexing or MIMO-OFDM frameworks are utilized to satisfy the necessities of high information transmission rates, as a result of their exceptional properties, for example, high otherworldly proficiency, high information rate and obstruction towards multipath proliferation. MIMO-OFDM frameworks are finding their applications in the advanced remote correspondence frameworks like IEEE 802.11n, 4G. In this paper, we consider the plan of LTE system and diagram the channel estimation. To achieve high data rate correspondence with flexibility, Long term evolution (LTE) has been displayed. LTE Downlink systems get Symmetrical Recurrence Division Different and MIMO to give upto 100 Mbps (expecting a 2x2 MIMO structure with 20MHz transmission limit). The execution get of MIMO overwhelmingly depends upon the correct estimation of Channel State information (CSI), which is crucial for every trade structure. In this paper, we show assorted channel estimation computations for LTE Downlink structures. This joins channel estimation using Pilot Images and Visually impaired Channel estimation counts. The estimation procedures incorporated the Slightest Square Mistake (LSE) and the Minimum mean square error (MMSE) is being inspected in conclusion broke down.

Downlink LTE System Performance Improvement by Using BCH Codes over LTE-MIMO Channel

Long-term Evolution (LTE) has potential feasibility to implement high-speed data transmission. This technology is essential for accommodating the rising utilization of data and voice service. Nonetheless, the main problem is the deteriorated performance of wireless communication systems following the elevation in bit error rate (BER) owing to multipath fading environments. Therefore, using channel coding is essential to reduce BER, which leads to enhancement of system performance of digital communication systems. Previous studies have reported utilization of channel codes including turbo and convolutional codes in LTE systems for attaining error control system. As such, the key challenge of selecting category of coding method is the trade-off between elevating decoding complexity and enhancing system performance. Hence, the study herein proposed Bose and Chaudhuri (BCH) codes as channel coding for downlink LTE system over MIMO channel. This is aimed to attain an adaptive error control with low complexity compared to turbo and convolutional codes. The findings indicated that BCH codes had reduced BER compared to turbo and convolutional codes in both quadrature phase-shift keying (QPSK) modulation schemes and binary phase-shift keying (BPSK) with regard to the downlink LTE system performance. The suggested method had approximately 4dB coding gain at 1X10-1 against both of convolutional and turbo codes in BPSK. While, for QPSK, the proposed method had approximately 5dB and 6dB compared to turbo and convolutional codes, respectively. Nonetheless, enhanced performance of the suggested system was observed through reducing BER of the received data by adding the number of antennas in MIMO channel.

SVM based on LMMSE for high-speed coded OFDM channel with normal and extended cyclic prefix

We propose in this article, a Linear Minimum Mean Squares Error-Support Vector Machine regression (LMMSE-SVR) method which is employed high-speed 3GPP Long Term Evolution (LTE) downlink coded channel estimation environment. LMMSE-SVR approach is applied to track and estimate the fast fluctuations caused by Doppler effect of a 3GPP realistic Extended Vehicular A model (EVA) channel. We integrate in this contribution both channel estimation at pilot symbols and interpolation at data symbols into the LMMSE-SVR process with and without turbo coding scheme. Bit Error Rate (BER) performance of our channel environment estimation proposal is validated via simulation of LTE downlink system for both coded and uncoded high-speed scenarios with normal and extended Cyclic Prefix (CP) modes.

Fast-Fading Channel Environment Estimation Using Linear Minimum Mean Squares Error-Support Vector Regression

In this article, we propose a Linear Minimum Mean Squares Error-Support Vector Machine regression (LMMSE-SVR) approach which is applied to Long Term Evolution (LTE) downlink channel environment estimation under high mobility conditions. LMMSE-SVR is employed to track and estimate the rapid variations of a realistic Extended Vehicular A model channel according to 3GPP specifications. This contribution assimilates both channel estimation at reference signals and interpolation at data signals into the LMMSE-SVR method. Performances of our channel environment estimation proposal in terms of Bit Error Rate and Mean Squares Error are established via simulation for both normal and extended Cyclic Prefix scenarios in LTE downlink system with 64-QAM modulation scheme under 350 km/h mobile speed.

Real Time- Optimized Scheduler Using Earliest Due Date Mechanism in LTE Downlink System

Long Term Evolution (LTE) is standardized by the Third Generation Partnership Project (3GPP) as the most recent standard in the mobile network technology tree with flat architecture in order to conduct a new model aiming to offer higher-data-rate, lower-latency, and packet-optimized radio access technology called Evolved Universal Terrestrial Radio Access Network (E-UTRAN). However, the schedulers aiming to deal with the Real Time (RT) and the Non-Real Time (NRT) traffic have not defined by the 3GPP specifications. Accordingly, it is very important to design and implement optimum scheduling schemes for achieving the required Quality of Service (QoS) prerequisites such as packet delay and Packet Loss Rate (PLR) of RT multimedia services in E-UTRAN. Thus, the proposed scheduler is presented in this paper as well as the performance of the new scheduling strategy which is based on the Earliest Due Date (EDD) approach. The new proposed scheduler provides better results as compared with the conventional scheduling strategies, especially for multimedia applications in downlink framework of LTE system. The proposed scheduler achieves the highest good-put as well as the lowest PLR especially for the video users.

Random neural network based cognitive engines for adaptive modulation and coding in LTE downlink systems

This paper presents two random neural network (RNN) based context-aware decision making frameworks to improve adaptive modulation and coding (AMC) in long-term evolution (LTE) downlink systems. In the first framework, AMC is modelled as a traditional classification problem with the aim to maximize the probability of correct classification. The second framework seeks to optimize the throughput as opposed to simply maximizing the probability of the correct classification. To model the second framework, we developed a hybrid cognitive engine (CE) architecture by integrating an RNN based learning algorithm with genetic algorithm (GA) based reasoning. RNN inherent properties help CE to comply with the essential CE design requirement (i.e. concurrent long-term-learning, low computational complexity, and fast decision making). The performance of RNN is compared with artificial neural networks (ANN) and state-of-the-art effective exponential SINR mapping (EESM) algorithm. A comprehensive analysis of the proposed RNN based AMC scheme is presented by jointly incorporating the effect of different schedulers, feedback delays, and multi-antenna diversity on the throughput of an orthogonal frequency-division multiple access (OFDMA) system. The critical analysis of the first framework revealed that RNN based CE can achieve comparable results with faster adaptation, even in severe environment changes without the need of retraining compared to ANN. The analysis of the second approach demonstrated RNNs faster adaptation as compared to ANN and showed upto 253% gain in user throughput. RNN based CE efficiently exploited the channel quality information feedback delay to improve system throughput and helped cell-edge and cell-centre users to experience much better services in terms of achieved throughput as compared to EESM.

Performance Improvement for PAPR Reduction in LTE Downlink System with Elliptic Filtering

This paper is concerned with the performance improvement of PAPR reduction of orthogonal frequency division multiplexing (OFDM) signal using amplitude clipping & filtering based design. Note that OFDM is one of the well adept multi-carrier multiplexing transmission scheme which has been implemented in long term evolution (LTE) downlink. Nonetheless peak to average power ratio (PAPR) is the more rattling problem with OFDM, consequently in this paper a reduction procedure of the PAPR by using amplitude clipping and filtering is proposed. Here we used IIR bandpass elliptic filter after amplitude clipping to reduce the PAPR. The performance of the system in terms of bit error rate (BER) is also canvased as a new filter based clipping method. Our results show that the proposed methodology of clipping method with the IIR elliptic band pass filter significantly reduces the PAPR value.

Computationally effective sampling frequency‐offset estimation for OFDM‐based LTE downlink systems

AbstractIn this paper, we present a low‐complexity sampling frequency‐offset (SFO) estimation scheme suitable for the 3GPP long‐term evolution (LTE) downlink system. First, a novel SFO estimation method for a pilot‐aided orthogonal frequency division multiplexing system is proposed providing a good performance with reduced complexity. To achieve low complexity, the proposed estimation scheme uses a central conjugate‐symmetric primary synchronisation signal specified in the LTE standard, which eases the SFO estimation at the receiver. For performance evaluation, we derive the mean square error expression of the proposed frequency estimation scheme. Simulations show that the proposed frequency estimation scheme can detect the SFO with higher accuracy and much lower complexity, compared with the conventional estimation schemes. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of Bandwidth Scalability on System Performance in the Downlink LTE Systems

Long Term Evolution (LTE) system employs Orthogonal Frequency Division Multiple Access (OFDMA) in downlink in order to support network deployment using various system bandwidth configurations i.e., 1.4MHz, 3MHZ, 5MHz, 10MHz, 15MHz and 20MHz. The bandwidth scalability enables operator to access multiple channels to achieve higher peak data rates. Also, the bandwidth scalability allows operators to deploy LTE network with the existing spectrum or newly licensed band. Therefore the study on performance of LTE system with different bandwidth configuration becomes vital. Hence in this paper, an attempt has been made to study and compare the performance of LTE system with different spectrum configuration i.e., 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz and 20MHz for Constant Bit Rate (CBR) traffic scenario in the downlink. The performance metrics considered for simulation studies are aggregate bytes received, average throughput, average delay and average jitter. Keywords- LTE, OFDMA, downlink, bandwidth scalability, aggregate bytes received, avearge throughput, avearge delay, average jitter

Optimized scheduling technique of null subcarriers for peak power control in 3GPP LTE downlink.

Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system.

Two-Step Resource Block Allocation Algorithm for Data Rate Maximization in LTE Downlink Systems

This study focuses on resource block allocation issue in the downlink transmission systems of the Long Term Evolution (LTE). In existing LTE standards, all Allocation Units (AUs) allocated to any user must adopt the same Modulation and Coding Scheme (MCS), which is determined by the AU with the worst channel condition. Despite its simplicity, this strategy incurs significant performance degradation since the achievable system throughput is limited by the AUs having the worst channel quality. To address this issue, a two-step resource block allocation algorithm is proposed in this paper. The algorithm first allocates AUs to each user according to the users' priorities and the number of their required AUs. Then, a re-allocation mechanism is introduced. Specifically, for any given user, the AUs with the worst channel condition are removed. In this manner, the users may adopt a higher MCS level, and the achievable data rate can be increased. Finally, all the unallocated AUs are assigned among users without changing the chosen MCSs, and the total throughput of the system is further enhanced. Simulation results show that thanks to the proposed algorithm, the system gains higher throughput without adding too many complexities.

Comparison between Performances of Channel estimation Techniques for CP-LTE and ZP-LTE Downlink Systems

In this paper, we propose to evaluate the performance of channel estimation techniques for Long Term Evolution (LTE) Downlink systems based on Zero Padding technique (ZP) instead of Cyclic Prefixing (CP). LTE Downlink system is a multiuser system based on a MIMO-OFDMA technology. Usually, in OFDM systems, a guard interval is inserted in order to mitigate both inter-carrier interference (ICI) and inter-symbol interference (ISI). LTE Downlink systems are based on CP-OFDM technique which consists of a copy a last OFDM symbols inserted at the beginning of each transmitted OFDM symbol. Although this technique shows good performances, the CP-LTE system suffers from a power efficiency loss.With the number of present OFDM symbols in LTE Downlink radio frame, the bandwidth loss becomes more important. Instead of CP, we propose to evaluate the performance of ZP-LTE systems in order to avoid the power efficiency .In this paper, we interest to evaluate the performance of channel estimation techniques for the two LTE Downlink systems. Simulations results show that although ZP-LTE systems outperform CP-LTE Downlink systems in terms of power efficiency, the CP-LTE systems show better performance than ZP-LTE systems and especially for high SNR values. MATLAB Monte-Carlo simulations are used to evaluate the performance of LS, LMMSE and Lr-LMMSE estimators in terms of Mean Square Error (MSE) and Bit Error Rate (BER) for 2x2 LTE Downlink systems.

Complex Support Vector Machine Regression for Robust Channel Estimation in Lte Downlink System

In this paper, the problem of channel estimation for LTE Downlink system in the environment of high mobility presenting non-Gaussian impulse noise interfering with reference signals is faced. The estimation of the frequency selective time varying multipath fading channel is performed by using a channel estimator based on a nonlinear complex Support Vector Machine Regression (SVR) which is applied to Long Term Evolution (LTE) downlink. The estimation algorithm makes use of the pilot signals to estimate the total frequency response of the highly selective fading multipath channel. Thus, the algorithm maps trained data into a high dimensional feature space and uses the structural risk minimization principle to carry out the regression estimation for the frequency response function of the fading channel. The obtained results show the effectiveness of the proposed method which has better performance than the conventional Least Squares (LS) and Decision Feedback methods to track the variations of the fading multipath channel.