LTE系统仿真平台设计及其调度算法性能验证

系统级仿真平台是实现LTE算法研究和验证,完成LTE系统性能评估和优化的重要方面。基于3GPP相关协议和标准,对LTE系统级仿真平台进行研究和设计。利用MATLAB模拟了实际的多用户蜂窝环境,搭建了功能完整的仿真平台,同时采用MEX技术提高了系统的仿真效率。利用文中设计的仿真平台就三种典型的资源调度算法进行性能仿真,仿真结果与理论分析相符,进一步验证了平台的有效性。     

LTE系统时频同步算法及其DSP实现

介绍了LTE—FDD系统主同步序列的产生,给出了一种基于主同步信道的时频同步算法,包括符号定时同步算法和频偏估计算法。定时同步算法引入了多径能量窗,并且根据LTE系统同步信道的特点,对多个同步信道上的相关值进行非相干合并,有效地提高了同步性能。对所给出的算法进行仿真,并采用DSP实现同步算法。仿真和实验结果表明,所给出的算法具有良好的性能,能够满足LTE系统对同步性能的要求。     

LTE系统中截尾卷积码译码算法研究及仿真性能分析

在LTE的下行控制信道和广播信道中采用了截尾卷积编码方式,本文介绍了LTE系统中采用的卷积编码器以及广播信道架构,详细分析了截尾卷积码的两种常用译码算法,文章提出了一种改进循环译码算法,在基于LTE-PBCH信道链路中对各种译码算法进行仿真,仿真测试结果表明,截尾卷积码可满足LTE信道对高速率业务的要求,双回溯循环译码算法的译码性能最佳。     

LTE系统中Turbo译码的改进算法

LTE系统对可靠通信提出了更高的要求,这在一定程度上依赖于信道编码的性能。针对LTE系统中的Turbo译码算法进行了研究,在Max-Log-MAP和Log-MAP算法的基础上提出了一种改进算法。理论分析和仿真结果表明,这种改进算法的性能有进一步提升,并且更加易于硬件实现,具有较低的复杂度。     

一种基于LLR软判决的LTE解映射简化算法

针对目前LTE解映射算法复杂度高的缺陷,提出了一种基于LLR软判决的LTE解映射简化算法SLLR。该算法旨在通过使用对数似然比进行软判决,以简化指数计算与对数计算为主,降低LTE解映射过程中计算的复杂度。通过对标准算法与简化算法的QAM调制方式产生的误码率、误块率进行仿真和比较,结果表明该SLLR简化算法性能良好,适用于LTE通信系统。     

LTE中小区初始搜索与主同步算法的研究

3GPPLTE系统的同步信号包括主同步信号PSS与辅同步信号SSS,用于小区搜索。时频同步是LTE系统小区搜索的基本需求,文章简单介绍了LTEFDD系统主同步序列与辅同步序列的产生、小区初始搜索流程,总结了探测LTE主同步信号PSS的几种不同方法,针对当系统频偏较大时同步性能较差这个问题,对一种改进的M．partN]步算法的性能进行仿真。仿真和实验结果表明,M-part同步算法具有良好的同步性能,能够满足LTE系统对同步性能的要求。     

LTE系统中的信号检测算法性能分析

为了满足高数据率和高系统容量的需求,LTE系统采用了MIM0多天线技术。MIMO信号检测算法的性能将直接影响系统的整体性能。本文主要介绍7＂LTE系统中的ZF、MMSE、OSIC和Turbo迭代检测算法,并通过LTE下行链路仿真对其进行性能分析。结果表NTurbo迭代检测性能最优,并选择2次迭代即可。MMSE—OSIC、MMSE、ZF—OSIC性能次之,ZF性能最差。     

自适应调制编码技术在LTE OFDM系统中的性能分析

文章在给出了自适应LTE OFDM系统模型之后,采用基于SNR的自适应算法,对自适应调制及编码技术在LTE OFDM系统中的误比特率性能进行了分析和仿真验证.仿真结果表明,将基于SNR门限的自适应编码调制技术用于LTE OFDM系统,可提高系统性能,且计算复杂度低.     

一种基于循环前缀ML算法的改进算法的研究

LTE作为引领未来通信发展的方向,OFDM技术凭借其优势,成为了LTE下行链路的关键技术,而接收端的同步性能对LTE系统的影响就显得尤为重要。文章简要介绍了一种基于循环前缀的同步算法经典算法ML算法,然后针对这种算法的弊端提出一种改进的基于循环前缀的同步算法,最后通过仿真得出改进的算法在同步性能上较经典算法有很大的提高。     

LTE基于码本选择预编码研究

本文研究了LTE系统中基于码本选择的预编码发送方案,对LTE基于码本选择的预编码方案进行了推导,提出了基于性干比（SINR）的码本选择算法,并对其进行了性能仿真。仿真结果表明,在4根发射天线和2根接收天线配置下,基于码本的预编码简单实用,且能够在在满足LTE性能需求的基础上大大提高系统性能。     

Comparative Study of Power Saving and Delay in LTE DRX,Directional-DRX and Hybrid-Directional DRX

With integration of advanced long term evolution networks (LTE networks) in mobile technology, 5G networks are introduced due to broadband spectrum extension which requires higher power consumption. Discontinuous reception (DRX) sleep mode mechanism is provided to accommodate lower power consumption of user equipment terminals (UE_s). For mmWave directional communication air interface in LTE between UE and LTE eNB, UE performs beam searching and alignment with LTE eNB (4G base station) after every short/long DRX cycle during ON duration. Dual connectivity of UE to both LTE eNB and NR NodeB (5G New RAN base station) is a hybrid-directional system. This allows us to propose a sleep mode mechanism which is called hybrid directional-DRX (HD-DRX). In HD-DRX, UE performs beam searching and alignment with NR NodeB during ON duration only if data packet intimation. A semi-Markov chain process is introduced to describe UE state transition. Depending on this chain, power saving factor and average delay are calculated. HD-DRX power saving as compared to LTE DRX and Directional-DRX (D-DRX) is conducted. Due to different beam searching procedure, another comparison of average delay is assigned between D-DRX and HD-DRX. Data traffic model parameters are considered and numerical analysis is validated using MATLAB program simulations.     

Accurate Modeling of the DRX Mechanism with Predetermined DRX Cycles Based on the 3GPP LTE Standard

In Long Term Evolution-Advanced (LTE-A), the Discontinuous Reception (DRX) mechanism conserves the power of a User Equipment (UE) by monitoring the UE’s downlink channels for a specific period and turning off the UE’s radio when no packets arrive during the period. There has been heated discussion in previous studies, but most previous models of DRX operation are partially inconsistent with the LTE-A specifications. The reason is that the previous models hold the assumption that a new DRX cycle starts after an expiration of a drx-InactivityTimer or a period of continuous reception. This assumption causes undetermined DRX cycles and fixed-length sleep time in a UE in a DRX mechanism. However, the drx-InactivityTimer expiration can occur at any instant within a DRX cycle, which causes the variable-length sleep time. In this paper, we first propose a novel analytical model fitting for the specification DRX mechanism by using a semi-Markov process. Two key performance indicators affected by the DRX mechanism, the power saving factor and the average buffering delay of radio-off periods, are derived. We also prove the feasibility of the proposed model with stability analysis. Finally, the analytical results are validated against the simulation results and show the effects of different DRX configurations for the Poisson arrival process.     

Energy Saving Mechanism with a Route Prediction Based Intra-handover in LTE Networks

Long term evolution standard employs the discontinuous reception (DRX) technology to help user equipment (UE) in energy saving. After the UE received nothing from the base station for a predefined time span, it turns off the radio frequency module to enter sleep mode for energy saving. An UE may fail to handover or lost connection for late handover in case it enters sleep mode before handover and missed the optimal handover timing, therefore results in data loss. This paper proposes an energy saving mechanism with a prediction based intra-handover which predicts the next target handover base station and the optimal handover time according to the historical path data kept in a database. The UE would check whether the next sleep mode outlast the handover time point before entering sleep mode to reduce power consumption for handover failure caused by the long DRX cycle and base station reselection. Simulation results show that the DRX mechanism helps reduce power consumption of UE by 90–95 % over the conventional one more than 7 % handover failures. The energy saving mechanism combined with route prediction leads to 22 % more energy saving while cutting handover failures to 5 %.

     

An application aware discontinuous reception mechanism in LTE-advanced with carrier aggregation consideration

3GPP Release 8 specifications define a mechanism named DRX (Discontinuous Reception) to save UE’s (User Equipment) energy consumption in LTE (Long Term Evolution). The DRX allow an UE to stop monitoring PDCCH (Physical Downlink Control CHannel) on a CC (Component Carriers) during some periods of the operation time. Obviously, the duration and the frequency of these non-monitoring periods are important parameters that can significantly impact the ES (Energy Saving) efficiency and the performance of applications running on the CC. In Release 9, 3GPP introduces an advanced technology named CA (Carrier Aggregation) for LTE-Advanced to achieve higher bandwidth and throughput: the UE may operate over up to 5 CCs. The conventional DRX operations are no longer appropriated in the CA case: applying the same DRX configuration for all the CCs is neither performance-optimal nor energy-efficient if applications with different QoS requirements operating simultaneously on the CCs in realistic environment. A DRX mechanism by taking both applications’ QoS requirement and CA into account to achieve reasonable ES might be an optimal choice. In this paper, based on the survey of various conventional DRX energy saving protocols in LTE networks, we propose a simple but efficient application aware DRX mechanism to optimize the performance in LTE-Advanced networks with CA consideration. The simulation results verify that the ES efficiency is conditioned to the fulfillment of the DRX parameters, and our proposed optimal scheme can significantly improve energy saving efficiency as compared to the conventional DRX mechanism.     

不连续接收与电压岛结合的省电方法

LTE系统支持高速的数据传输。高的数据传输速率需要更复杂的基带调制解调器芯片,这就加快了终端电池的能量的消耗。因此,LTE引入了不连续接收机制(DRX)来延长终端的电池试用时间。结合DRX,本文提出了一个动态的电源管理方案—分层多级电压岛(HMVIP),并建立省电类。结果表明,在单一的LTE终端芯片上,DRX结合HMVIP可以达到更好的省电性能。     

Improvement in DRX Power Saving for Non‐real‐time Traffic in LTE

A discontinuous reception (DRX) operation is included in the Long Term Evolution (LTE) system to achieve power saving and prolonged battery life of the user equipment. An improvement in DRX power saving usually leads to a potential increase in the packet delay. An optimum DRX configuration depends on the current traffic, which is not easy to estimate accurately, particularly for non‐real‐time applications. In this paper, we propose a novel way to vary the DRX cycle length, avoiding a continuous estimation of the data traffic when only non‐real‐time applications are running with no active real‐time applications. Because a small delay in non‐real‐time traffic does not essentially impact the user's experience adversely, we deliberately allow a limited amount of delay in our proposal to attain a significant improvement in power saving. Our proposal also improves the delay in service resumption after a long period of inactivity. We use a stochastic analysis assuming an M/G/1 queue to validate this improvement.     

Performance Evaluation of Sleep Mode on Power Saving in WiMAX IEEE 802.16m and LTE DRX

Power saving represents a vital role in mobile communications networks such as IEEE 802.16m and LTE. Modern user equipment (UE_s) require high data rates and low power consumption. It is found that arranging sleep mode mechanisms ensures UE battery longer lifetime. In this paper, different sleep mode mechanisms are investigated for both IEEE 802.16m and LTE networks. The analyses are based on Markov and Semi-Markov chains. It is focused on the determination of UE transition state. Web traffic model parameters were considered in MATLAB simulation and a comparison assessment was conducted between WiMAX IEEE 802.16m and LTE DRX. It was found that LTE DRX sleep mode provides more power saving than WiMAX IEEE 802.16m sleep mode. The study is now implemented for 5G networks with encouraging results.     

DRX mechanism for power saving in lte - [topics in radio communications]

Enhanced discontinuous reception mode is supported in long term evolution of 3GPP standards to conserve the mobile terminal?s battery power. Furthermore, there are additional advantages in using DRX, such as over-the-air resource saving on both the uplink and downlink to increase overall system capacity. One of the enhancements over 3G wireless systems is that in LTE DRX mode can be enabled even when the user equipment is registered with the evolved node-B. However, there is a need to optimize the DRX parameters, so as to maximize power saving without incurring network re-entry and packet delay. In particular, care should be exercised for real-time services. In this article the power saving methods in both network attached and network idle modes as outlined in LTE are explained. The optimum criteria to select the DRX mode are defined for different applications. Analytical/simulation results are presented to show the power saving/connection reestablishment and packet delay.     

下一代移动网络中非连续接收机制对移动互联网业务性能影响分析

移动互联网业务的发展引发了大量需要终端与网络间进行频繁交互的业务,产生了终端能量和无线信令资源消耗过度的问题。结合3GPP标准定义的下一代移动网络非连续接收(discontinuous reception,DRX)机制,从终端能耗、数据包延时、空口资源开销等角度出发,分析了DRX机制对典型移动互联网业务的网络性能影响,并对DRX机制的参数配置提出了优化建议。     

Modeling UMTS Power Saving with Bursty Packet Data Traffic

The universal mobile telecommunications system (UMTS) utilizes the discontinuous reception (DRX) mechanism to reduce the power consumption of mobile stations (MSs). DRX permits an idle MS to power off the radio receiver for a predefined sleep period and then wake up to receive the next paging message. The sleep/wake-up scheduling of each MS is determined by two DRX parameters: the inactivity timer threshold and the DRX cycle. In the literature, analytic and simulation models have been developed to study the DRX performance mainly for Poisson traffic. In this paper, we propose a novel semi-Markov process to model the UMTS DRX with bursty packet data traffic. The analytic results are validated against simulation experiments. We investigate the effects of the two DRX parameters on output measures including the power saving factor and the mean packet waiting time. Our study provides inactivity timer and DRX cycle value selection guidelines for various packet traffic patterns.