LTE系统中安全机制研究

长期演进（LTE）系统代表了UMTS标准的最新发展方向。随着LTE网络架构的改变,原来UMTS提供的网络接入安全机制已不能够满足网络变化的需求。为了应对所面,临的各种威胁,LTE针对网络接入安全进行了大幅度的改进。丈中主要针对LTE网络的安全架构、认证和密钥协商、密钥管理体系和RRC、NAS层的安全机制等方面进行了研究。     

LTE系统与2G、3G系统共站址共存问题分析

以LTE系统与GSM系统和UMTS系统共站址部署为共存场景,对2.6 GHz频段LTE系统与2G/3G系统的共存问题进行了分析,得到了相应的额外隔离度需求和工程隔离需求,给出了2.6 GHz频段LTE系统部署与2G、3G系统共站址时的天线隔离距离的初步建议。     

某运营商农村数据业务承载方案建议

针对某运营商EGRPS网络在农村面对的困境和该运营商GSM900技术向UMTS900技术或LTE技术演进的必要性,分析7GSM900技术向UMTS900技术或LTE技术演进的频率规划,最后从覆盖、容量和网络改造三个方面分析了该运营商GSM900技术向UMTS900技术或LTE技术演进对现有GSM900网络影响。UMTS900和LTE允许的下行最大路径损耗比GSM900语音业务允许的最大路径损耗大3～4dB,部署UMTS900或者LTE系统后,可以提供的下行数据吞吐量是原有GSM900系统的4．38—20．18倍。     

LTE系统IMS用户安全性研究

长期演进（LTE）系统代表了UMTS标准的最新发展方向,作为一种纯分组系统,它具有全新的无线接口和体系结构,其频谱效率是HSDPA/HSUPA的2倍。文章分析了LTE系统安全的主要内容,提出了LTE系统用户安全的体系结构,给出了IP网络的NDS体系结构,介绍了IMS AKA工作流程,并描述了终端和P-CSCF之间的安全关联。     

蜂窝移动通信系统的安全架构

总结了移动通信系统中的信息安全问题,对GSM、UMTS和LTE移动通信系统的安全体系、安全目标、安全机制和安全缺陷等问题进行了详细分析;对未来移动通信网络进行了展望,认为未来移动通信网络是多种接入网络融合的通信网络,是开放的、弹性的、可编程的网络,其更加开放和灵活的网络架构不可避免地会引入新的安全风险。     

LTE系统中接入层加密和完整性保护研究

随着移动通信的发展,通信网络中安全问题也日益严重。LTE与UMTS和GSM一同提供了一种相似的安全性。本文首先介绍了安全性中的认证和密钥协商进程,然后对LTE系统中的密钥产生体系和使用流程进行了分析,着重对接人层的安全模式命令进行阐述,最后总结了LTE中两大安全性功能的实现方案。     

LTE系统中用户安全研究

介绍了LTE系统安全的主要内容,描述了UMTS AKA和EAP AKA的工作流程,分析了LTE密钥体系结构以及密钥与信息流之间的对应关系.     

LTE系统核心技术剖析及eNodeB测试方案探讨

UMTS系统的广泛应用满足了用户对数据业务的需求,并且有效提高了通话质量和数据速率。然而,宽带接入技术的出现及普及,Wi-Fi、WiMAX系统高数据速率的优势,对UMTS系统带来很大的冲击。这使得UMTS系统数据速率不高、时延较长、网络结构复杂等不足愈加明显。因此3GPP提出的UMTS的长期演进计划（LTE），通过提供一个以高速率和低时延为特征的分组优化系统来保证UMTS在未来10年的竞争力和领先性。     

LTE系统下行链路动态分组调度的性能研究

文章介绍评估了3GPP UTRAN(UMTS陆地无线接入网)LTE(长期演进)系统中下行链路的动态分组调度性能。因为具备不同QoS(服务质量)要求的业务都要竞争资源,故分组调度在LTE中占有非常重要的地位。文章基于LTE下行链路介绍了一种时域和频域分离的分组调度框架。在四种不同的3GPP宏观仿真案例下,使用三种基本调度方法组合的具有不同公平性的调度器进行仿真实验,结果展示了公平性和频谱效率之间的折衷。     

LTE产生背景及发展目标

LTE（长期演进）系统代表了UMTS标准的最新发展方向,作为一种纯分组系统．它具有全新的无线接口和体系结构,其频谱效率是HSDPA／HSUPA的2倍。文章分析了移动话音用户数和移动数据使用增长情况,介绍了有线技术演进的过程,提出了LTE发展的动机与目标。     

An effective approach to solving large communication overhead issue and strengthening the securities of AKA protocols

Authentication and key agreement (AKA) is a challenge‐response‐like security protocol that uses symmetric‐key cryptography to establish authenticated keys between 2 parties. Its application in the third‐generation mobile system universal mobile telecommunications system (UMTS) is called UMTS‐AKA, and the version applied in the fourth‐generation mobile communication system long‐term evolution (LTE) is called LTE‐AKA. Both UMTS‐AKA and LTE‐AKA share the same weakness: the network operators need to maintain a large space of authentication vectors for visiting stations, and the transmission of the vectors causes lots of overhead. This weakness will be amplified when there are billions of devices accessing the network in the Internet‐of‐things scenarios. In addition, these schemes provide only key distribution (not key agreement) and cannot provide session key forward secrecy. In this paper, we propose a range‐bound key assignment technique to tackle the challenges. The proposed scheme drastically reduces the communication overhead and greatly strengthens the security robustness. The securities are analyzed and are verified using the AVISPA toolset.     

Reward-Based Radio Interface Selection of Hybrid 4G UMTS and LTE Communications for Fast Cloud Accesses

For achieving fast accesses the cloud’s big data through mobile smart node, an extreme high data rate for the forwarding link under high-mobility wireless communications is necessary. 3GPP thus specifies LTE/LTE-Advanced specifications as the 4G system to cooperate with the existing UMTS system. To balance loads among different communication interfaces in the hybrid cellular system is one of the most important issues that should be addressed for achieving efficient radio resource allocations. In a shared packet service, the 3GPP UMTS adopts the VSF-OFCDM interface to allocate orthogonal codes of an OVSF code tree in two-dimension spreading of the time and frequency domains. However, UMTS suffers from high packet loss rate and high bandwidth waste rate. In 4G, although the LTE/LTE-Advanced interface offers a high data rate, it suffers from unbalanced loads and moderate reward. This paper thus proposes an adaptive radio interface selection for balancing loads between the UMTS and LTE/LTE-Advanced interfaces according to various interference and mobility environments. Numerical results indicate that the proposed approach outperforms other approaches in fairness, FRL, utilization and call blocking.     

3GPPLTE系统安全性研究

长期演进（LTE）系统代表TUMTS标准的最新发展方向,作为一种纯分组系统,它具有全新的无线接口和体系结构,其频谱效率是HSDPA／HSUPA的2倍。本文分析了LTE系统安全的主要内容,提出TLTE用户安全的体系结构,描述TIP网络的NDS体系结构,介绍了隧道模式下的ESP保护原理。     

Adaptive radio resource management for maximizing reward and balancing loads in 4G hybrid universal mobile telecommunications system and long term evolution communications

The universal mobile telecommunications system (UMTS) and long term evolution (LTE)/LTE‐advanced specifications have been proposed to offer high data rate for the forwarding link under high‐mobility wireless communications. The keys include supporting multi‐modes of various coding schemes (e.g., VSF‐OFCDM, OFDM, OFDMA), multiple‐input multiple‐output, relay networks, and so on. To balance loads among different communication interfaces is one of the most important issues that should be addressed for achieving efficient radio resource allocations. In a shared packet service, the 3GPP UMTS adopts the VSF‐OFCDM interface to allocate orthogonal codes of an OVSF code tree in two‐dimension (2D) spreading at the time and frequency domains. However, it easily leads to high packet loss rate and high bandwidth waste rate, because it does not consider interference and the adaptive modulation and coding scheme simultaneously. Conversely, although the LTE/LTE‐advanced interface offers a high data rate, it suffers from unbalanced loads and moderate reward. This paper thus proposes an adaptive radio resource allocation for balancing loads between the UMTS and LTE/LTE‐advanced interfaces according to various interference and mobility environments. In addition, an adaptive multi‐code allocation is proposed for the UMTS to minimize the bandwidth waste rate while guaranteeing quality of service. Numerical results indicate that the proposed approach outperforms other approaches in fractional reward loss and system utilization. Copyright © 2013 John Wiley & Sons, Ltd.     

An Analytical Evaluation Approach for Control Plane Operations of a Multi-RAT Mobility Procedures in a User Equipment

It is evident that the present and future deployment of multiple radio access technology (RAT), e.g., WLAN, LTE, WiMAX, etc., will advent multi-RAT user equipment (UE). There will be four major challenges due to multi-RATs existence, i.e., fast-reliable signaling, fast-reliable mobility with Quality of Service (QoS), security and reasonable cost. In this paper we deal with performance modeling signaling plane. Most of the reported works present signaling performance between two RATs e.g., EUTRAN to CDMA2000 etc., and vice versa (or single RAT scenarios e.g., UMTS to UMTS). To the best of our knowledge, there has been no analytical modeling approach available for performance analysis of entire control plane operations in a multi-RAT UE, right from cell search to completion of mobility procedures in case of more than two RATs, i.e., a generic model for N-number of RATs. This paper proposes a generic Discrete Time Markov Chain (DTMC) based analytical method for evaluation of control plane operations for multi-RAT mobility procedures. Using the case of UE initiated multi-RAT mobility procedures, for presenting our analytical model we propose an algorithm, integrating and extending some of the known approaches which were mostly limited to single RAT. For this algorithm a generic analytical relationship is derived between time taken by each signaling process in each layer involved in the multi-RAT mobility procedure and the probability of success of the same. Finally, using the above analytical model a case study is presented where the performance of UE initiated mobility procedure for WLAN interworking with LTE supported by Proxy Mobile IP (PMIP) and Media Independent Handover (MIH). With our analytical model, results show that, for a target LTE cell, the increase in probability of successful completion of mobility procedure is 11 % from existing procedures. For target WLAN cell, the same is around 9 %. Notably, the results show how our analytical approach helps in modeling most of the control plane operations in multi-RAT mobility procedures, in a holistic manner.     

A narrow-frame antenna for WWAN/LTE/WiMAX/WLAN mobile phones

In this paper, we present a novel narrow-frame antenna with a size of 75 × 8 × 5.8 mm³ for 5.7 in. mobile phones. The antenna mainly consists of a monopole with four branches that are coupled to a two-branch grounded strip. Our antenna is able to cover more bands than other narrow-frame antennas by excitation of several resonant modes. The improved range of the antenna covers the following eleven bands: LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, LTE2500, LTE3400 (3400–3800 MHz)/WiMAX3.5 GHz (3400–3650 MHz), WLAN5.2 GHz (5150–5350 MHz) and WLAN5.8 GHz (5725–5875 MHz). Another advantage of the proposed antenna is that it does not need any lumped element to match the antenna. The working principles of the proposed antenna are thoroughly studied. A prototype of the proposed antenna is fabricated and measured, with the results in good agreement with the simulation results.     

Two Dimensional Signal Spreading in UMTS LTE: Exploiting Time-Frequency Diversity to Increase Throughput

This paper proposes a two-dimensional spreading method in UMTS Long Term Evolution (LTE). Such a method brings additional time-frequency diversity which is beneficial in terms of the ability to decode transmitted data at the receiver site under multipath fading. Additional diversity is provided due to the fact that chips of transmitted signals are spread using a Walsh-Hadamard spreading sequence over several subcarriers as well as over several time-slots simultaneously. A comparison with state-of-the-art LTE downlink transmission is provided. To enable reproducibility and to increase credibility of our results, an open source Vienna LTE simulator is utilized. LTE transmissions with the proposed 2D spreading are tested on several channel models. Simulations show that apart from an Additive White Gaussian Noise channel model, this 2D spreading based method outperforms the throughput performance of standard LTE. At high Signal to Noise Ratio (SNR), the throughput increase in most channel models is higher than 10 %.