A Re-Configurable Dual-Mode Delay-Aware Scheduling and Resource Allocation for LTE System

Long Term Evolution( LTE) has been proposed as an advanced wireless radio access technology to provide higher peak data rates and better spectral utilization efficiency,but the classical scheduling and resource allocation algorithms cannot optimally enhance the system performance due to high computational complexity. In this paper,a re-configurable dual mode delay-aware( CDD) scheduling and resource allocation algorithm is proposed to achieve the joint consideration of scheduling pattern,scheduling priority and quantity of scheduled data. In this study,dual-mode scheduling mechanism is associated with three configurable parameters and the CDD algorithm is involved to guarantee queuing delay with low loss of resource utilization and fairness.The computational cost of the scheduling and resource allocation algorithm is significantly reduced by efficiently utilizing Qo S Class Identifier( QCI) and Channel Quality Indicator( CQI) defined by LTE standards. The simulation results based on different application scenarios also represent the computation cost and complexity of scheduling algorithm along with the improved system throughput.

Energy-Saving Technology in Indoor LTE System with DTX Based on CQI

In LTE (Long Term Evolution) system, CQI (Channel Quality Indication) is a technical method to realize adaptive modulation and coding. The dispatcher of BS (base station) would allocate resource blocks to users dynamically based on CQI of uplink and downlink channels, which is necessary in the process of uplink and downlink transmission [1]. When the CQI level of the channel is high, the energy efficiency is high. On the contrary, when the CQI level of the channel is low, the energy efficiency is low. However, if signals are not transmitted until the quality of the channel is good, energy loss may be lowered in the expense of group delay. That is to say, we take CQI into account on the basis of the technology of DTX [2] [3] (Discontinuous Transmission). According to the result of simulation, the energy consumption can be reduced by using our proposed scheme. Particularly, the energy-saving effect is significant when the load is low.

Improved Method of Contention-Based Random Access in LTE System

Random access is the necessary process to establish the wireless link between the user equipment （UE） and network. The performance of the random access directly affects the performance of the network. In this work, we propose a method on the basis of the existing alternatives. In this method, we estimate the system load in advance to adjust the number of terminals. An access threshold is set to control the number of terminals which want to access the base station at an acceptable level. At the same time, we havean improvement on the existing power climbing strategy. We suppose that the power ramping is not always necessary for the re-access. And the selection ofpower ramping steps is studied in this paper. Simulations based on MATLAB are employed to evaluate the effectiveness of the proposed solution and to make comparisons with existing alternatives.

Throughput Evaluation of Downlink Multiuser-MIMO OFDM-LTE System

Recently, the mobile communication industry is moving rapidly towards long-term evolution (LTE) systems. LTE aims to provide improved service quality over 3G systems in terms of throughput, spectral efficiency, latency, and peak data rate, and MIMO technique is one of the key enablers of the LTE system for achieving these diverse goals. Among several operational modes of MIMO, multiuser MIMO (MU-MIMO) in which the base station transmits multiple streams to multiple users, has received much attention as a way for achieving improvement in performance. In this paper we present a Multiuser MIMO-OFDM-based simulator that includes the main physical layer functionalities and calculate the throughput of LTE Frequency Division Duplex (FDD) and Time Division Duplex (TDD) systems. The simulator has been used to evaluate the performance of the 3GPP Long-Term Evolution (LTE) technology.

MathWorks推出用于MATLAB的LTE System Toolbox

MathWorks推出了全新的LTESystemToolbox，为LTE和LTE—Advanced无线通信系统和设备提供了与标准兼容的仿真、验证和分析功能。此工具箱是MATLAB和CommunicationsSystemToolbox的扩展，目标用户针对需要设计或验证无线设备是否符合LTE标准的工程师。

Design of OFDM Transceiver for LTE System—A Survey

LTE (Long Term Evolution) is the latest technology in wireless communication. It is being used because of its peak data rate and spectral efficiency. LTE uses OFDMA (Orthogonal Frequency Division Multiple Access) technology for radio transmission and reception in downlink. OFDM is a multicarrier modulation and multiplexing technique to improve data rate, spectral efficiency and minimize the problem of fading and ISI (Inter Symbol Interference). Many transceivers design have been designed for OFDM system to minimize error and maximize throughput of the information being transmitted and received at the system. The purpose of this article is to present a survey of the published literature which deals with various OFDM transceiver design, focusing on the merits and demerits of the corresponding OFDM transceiver design.

Planning and Profit Sharing in Overlay WiFi and LTE Systems toward 5G Networks

With the increasing demand for data traffic and with the massive foreseen deployment of the Internet of Things (IoT), higher data rates and capacity are required in mobile networks. While Heterogeneous Networks (HetNets) are under study toward 5G technology, Wireless Fidelity (WiFi) Access Points (APs) are considered a potential layer within those multiple Radio Access Technologies (RATs). For this purpose, we have proposed in this paper a novel WiFi dimensioning method, to offload data traffic from Long Term Evolution (LTE) to WiFi, by transferring the LTE energy consuming heavy users, to the WiFi network. First, we have calculated the remaining available capacity of the WiFi network based on the estimated load of each WiFi physical channel using the overlapping characteristic of the channels. Then, we were able through this dimensioning method, to calculate the minimum needed number of WiFi APs that ensure the same or better throughput for the LTE transferred users. By this method, we have ensured additional capacity in the LTE network with minimum investment cost in the WiFi network. Finally, we have estimated the profit sharing between LTE and WiFi by considering data bundles subscription revenues and the infrastructure capital and operational costs. We have calculated for each network the profit share using a coalition game theory Shapley value that pinpoints the benefit of the cooperation using the proposed dimensioning method.

MathWorks推出用于MATLAB的LTE System Toolbox

MathWorks推出了全新的LTE System Toolbox，为LTE和LTE—Advanced无线通信系统和设备提供了与标准兼容的仿真、验证和分析功能。此工具箱是MATLAB和Communications System Toolbox的扩展，目标用户针对需要设计或验证无线设备是否符合LTE标准的工程师。

Study on coexistence between DCS1800 and TDD-LTE systems in multi-mode terminals

It＇s well known that the mobile stations will comprise a wide range of radio access technologies（RAT）, providing user with flexible and efficient access to multi-media service and high data rate communications. Although much work has been done for coexistence analysis between different systems base stations（BS）, most of them have not addressed the interference within multi-mode terminal. Hence, for filling the gap, The authors in the article present coexistence studyies of digital cellular system at 1 800 MHz（DCS1800） and time division duplex long term evolution（TDD-LTE） network in multi-mode terminal with multi-service provisioning. A new system model for coexistence was introduced and how deterministic analysis can be done within the terminal was explained. The interference evaluation model was given based on relations between reference sensitivity and signal-to-noise ratio（SNR）, which is also deduced. The system simulation methodology was provided and assumption used in simulation was given. Simulation results were shown with different system parameters. Numeric results indicate that multi-mode terminal is mainly affected by local interference. The minimum antenna isolation required for a health system operation was provided.

On design of physical random access channel in high-speed railway LTE systems

For the uplink in the long-term evolution(LTE)systems,the physical random access channel(PRACH)adopts Zadoff–Chu(ZC) sequences as preamble sequences,and each user can choose a unique cyclic shift for user identification.In high-mobility scenario,the Doppler frequency shift raises up the false alarm probability by inducing the correlation peak offsetting at the receiver side.Traditional detection method utilizes multiple search windows for searching the potential uplink users.When the Doppler frequency shift is larger than the subcarrier spacing,the energy of correlation peak leaks outside the search window and increases the false alarm probability.In this paper,we present a novel design for PRACH preamble sequence for high-speed railway scenario.Through numerical observation,we find out that the offset of the correlation peaks only depends on the initial root sequence number and the length of ZC sequences.Therefore,the root number of ZC sequences should be carefully designed to generate a preamble sequence to fight against the Doppler frequency shift.Consequently,those offsets of the correlation peaks are concentrated within a single search window,resulting in lower complexity of detection and lower probability of false alarm for random access in LTE uplink.

Coexistence Studies on the Interference Performance Between Mobile Satellite System and LTE Network

The interference coexistence performance between the systems of a Long Term Evolution(LTE) network and Mobile Satellite Service(MSS) system,both of which work around the frequency of approximately 2 GHz according to the bandwidth allocation in China,is proposed in this article.The related background of an MSS system and the common terminologies are introduced.Further,the coexistence scenarios of different coverage situations shared by the two systems are discussed.The interference impact of an MSS transmission on an LTE system is evaluated using a specific Monte Carlo method.Finally,simulation results show that although no crucial issues for the coexistence of an LTE downlink and the MSS are observed,the LTE uplink suffers a considerable amount of interference from the MSS transmission.Given the insufficient isolation between LTE and MSS existing networks,and the rapid advance in the field of LTE,problems may emerge in the near future.Further,this article can be of significance in providing reference for frequency spectrum planning in the existing LTE networks.

The System Performance for TD-LTE with Precoded MIMO

This paper introduces the rank adaptive precoded MIMO in TD-LTE downlink system.

基于动态贝叶斯网络的LTE-M车地无线综合承载系统可靠性分析

针对LTE-M车地无线通信系统可靠性分析中存在动态失效及承载不同业务等问题,基于动态贝叶斯网络对LTE-M车地无线通信系统进行可靠性评估。首先,在分析LTE-M系统结构和功能的基础上构建可靠性框图,并将可靠性框图转化为动态贝叶斯网络,实现网络的结构学习和参数学习。然后,通过动态贝叶斯网络正向推理得到LTE-M系统承载不同业务的可靠度并进行比较分析。最后,通过动态贝叶斯网络反向推理得到LTE-M系统的薄弱环节。研究结果表明:LTE-M车地无线通信系统运行100周后,承载CBTC业务的可靠度为0.903 17,承载乘客信息系统等业务的可靠度为0.719 91;基带处理单元、列车接入单元为系统薄弱环节,需要重点关注。

Modeling Components and Services of LTE Mobile Communications System

The latest wireless broadband network standard is LTE (Long Term Evolution) which is developed by 3GPP (3rd Generation Partnership Project). It will enable mobile devices such as smart phones, tablets and laptops to access Internet at a very high speed along with lots of multimedia services. There are many issues that are yet to be solved due to dynamic complex nature of wireless systems, multimedia software applications and software requirements. Poor service quality, service disconnections due to mobility, seamless handover, handover interruption time and downward compatibility to other Radio Access Networks (RAN) are some of the key issues for the current LTE systems that are addressed very recently in the scientific literature. Formal method is one of the promising software engineering techniques that assure quality and perfection in software system models. Formal methods use mathematical language to explicitly specify system specifications and requirements that serve as initial grounds for further development and implementation. It efficiently handles all component connections and resource management parameters using discrete structures. Z Schema language is used to model static aspects of LTE communications system. All the schemas are being verified using Z/Eves toolset. The aim is to provide sound mathematical foundation for system validation and verification that eventually results in a more reliable, scalable and complete software system.

轨道交通LTE系统等保接入方案及实现

根据西安地铁14号线研究对承载信号业务的LTE系统增加3级等级保护的具体方案及步骤,针对14号线线路特点提出2个可行的等级保护接入方案,并通过网络架构及性能评估比较,选择最优的等保接入方案,确保网络传输的安全稳定。同时通过等保系统相关接口配置、注意事项等描述,详细阐述涉及行车安全的LTE系统在增加等级保护过程中的重要步骤,确保网络安全,为轨道交通信号系统的行车指挥和列车运行控制提供重要保证,为后续轨道交通等保接入提供可参考价值。

An Energy Efficient Transmission Scheme for OFDM Systems in LTE

In orthogonal frequency division multiplexing(OFDM) systems,for given total transmit power,insertion of the noninformation bearing cyclic prefix(CP) will reduce the effective energy per information bit.Generally,the energy loss is proportional to the ratio of CP length to the symbol duration.If the CP is too long,the energy loss will be considerable high.In this paper,we propose an energy efficient transmission scheme for OFDM systems in Long Term Evolution(LTE) which is developed based on reduction of the CP energy.Simulation results show that the proposed method can save up to about10%of the total energy,while keeping almost the same bit-error-rate(BER) performance in some applications.

Coalition-based downlink resource allocation for LTE system with divide-and-conquer approach

To take advantage of the multiuser diversity resulted from the variation in channel conditions among the users, it has become an interesting and challenging problem to efficiently allocate the resources such as subcarriers, bits, and power. Most of current research concentrates on solving the resource-allocation problem for all users together in a centralized way, which brings about high computational complexity and makes it impractical for real system. Therefore, a coalitional game framework for downlink multi-user resource allocation in long term evolution （LTE） system is proposed, based on the divide-and-conquer idea. The goal is to maximize the overall system data rate under the constraints of each user＇s minimal rate requirement and maximal transmit power of base station while considering the fairness among users. In this framework, a coalitional formation algorithm is proposed to achieve optimal coalition formation and a two-user bargaining algorithm is designed to bargain channel assignment between two users. The total computational complexity is greatly reduced in comparison with conventional methods. The simulation results show that the proposed algorithms acquire a good tradeoff between the overall system throughout and fairness, compared to maximal rate and max-min schemes.

Frequency offset estimation based on peak power ratio in LTE system

Orthogonal frequency division multiplexing （OFDM） is one of the key techniques for long term evolution （LTE） system. Frequency offset estimation of OFDM is an essential issue. Especially in the high-speed environment, the frequency offset will become large. Based on the features of LTE uplink physical random access channel （PRACH）, this paper proposes a new frequency offset algorithm by using peak power ratio to enlarge the range of frequency offset estimation. According to the relation between frequency offset and the power delay profile （PDP）, the ratio of the peak power of the PDP at the main window to that at the negative window or positive window is utilized to estimate frequency offset. Simulation results show that the new proposed algorithm extends the estimation range of frequency offset from 1 000 Hz to 1 250 Hz. Meanwhile the accuracy of frequency offset estimation is almost not lost. Particularly in low signal noise ratio （SNR）, the new algorithm has lower mean square error （MSE） compared with traditional phase differential algorithm.

痰热清注射液辅助支气管肺泡灌洗对重症肺炎患者血清sCD163、Presepsin、LTE4水平的影响

目的探究痰热清注射液辅助支气管肺泡灌洗对重症肺炎患者血清可溶性CD163(sCD163)、可溶性白细胞分化抗原14(Presepsin)、尿白三烯E4(LTE4)水平的影响。方法选取重症肺炎患者180例,随机法分为参考组与研究组,各90例。参考组予以支气管肺泡灌洗治疗,研究组在参考组的基础上增用痰热清注射液治疗。对比两组疗效,各项症状消失时间,血清sCD163、Presepsin、LTE4水平,血气指标。结果研究组总有效率高于参考组,差异有统计学意义(P<0.05)。研究组各项症状消失时间均短于参考组,差异均有统计学意义(P<0.05)。治疗后两组血清sCD163、Presepsin、LTE4水平均低于治疗前,且研究组上述各项指标水平均低于参考组,差异均有统计学意义(P<0.05);两组各项血气指标较治疗前均明显改善,且研究组改善优于参考组,差异均有统计学意义(P<0.05)。结论痰热清注射液辅助支气管肺泡灌洗治疗重症肺炎患者的效果较佳,且能降低血清sCD163、Presepsin、LTE4水平,改善血气指标水平。

一种新颖的NTN频段和LTE频段共享的天线设计

在无线通信领域,传统天线结构通常仅支持地面(LTE)通信或者非地面网络(NTN)通信,无法同时满足两者的频段需求。随着频段的不断扩充,高集成度的天线设计已经成为无线通信领域重要的发展趋势。针对这一问题,提出了一种新颖的天线设计方案,能够在同一天线结构中实现NTN频段和LTE频段的共享。该方案通过使用射频开关,使天线能够在不同模式下独立工作,不仅简化了终端设备的设计,而且提高了天线的利用效率。通过使用CST Studio Suite进行全面仿真验证,结果表明该天线在LTE模式下覆盖880 MHz至960 MHz、1710 MHz至2170 MHz、2300 MHz至2690 MHz频段,天线的效率最低为-3 dB;在NTN模式下覆盖1.5 GHz至1.6 GHz频段,天线效率可达-1 dB,天线增益达到3 dB。此外,射频开关在高功率输入下的电压远低于门限压值,确保了实际应用的可行性。该研究为现代无线通信系统的发展提供了多功能、高效的天线设计思路,具有应用潜力。