LTE网络上行共享信道功控参数优化研究

LTE无线系统中的反向功控主要用来使反向传输适应不同的无线传输环境,减少LTE网络中边缘用户的干扰。主要介绍了LTE反向功控原理,重点研究上行共享信道标称功率参数优化原理。从理论上研究LTE上行共享信道标称功率对LTE网络反向吞吐量的影响,并通过实际网络进一步验证上行共享信道标称功率功控参数对网络反向吞吐量的影响,并提出上行共享信道标称功率功控参数优化的建议。     

动态频谱访问中的最小最大公平功率与数据率联合控制算法

该文研究动态频谱访问中次用户通过功率控制共享主用户频谱资源的问题。将最小最大公平功率与数据率联合控制问题建模为准凹优化问题,提出了基于迭代求解线性规划问题的功率控制算法。此外,还提出了通过次用户间相互协作估计次用户到主用户以及次用户间链路增益的方法,分析了链路增益估计误差的统计特性,提出了利用保护裕量降低链路增益估计误差对主用户和次用户服务质量影响的方法。仿真结果表明：所提出算法的性能与现有算法相同,但计算时间仅为现有算法的10%~50%,甚至更低;1 dB的干扰裕量和1.5 dB的信干噪比裕量足以保证主用户和次用户服务质量免受链路增益估计误差的影响。     

Spectrum Allocation for Enhanced Cross-Tier Interference Mitigation with Throughput Improvement for Femtocells in a Heterogeneous LTE Cellular Network

Wireless Personal Communications - Femtocells are the solution to improve cellular system capacity in indoor coverage. In two-tier networks, co-channel interference is a serious problem. In this...     

基于Licensed Assisted Access技术的退避算法设计与优化

随着无线宽带网络的发展,移动数据业务疯狂增长,频谱资源紧缺,为了扩充LTE容量,提高频谱利用率,LAA(Licensed Assisted Access)技术,即在非授权频段部署LTE网络,与其他无线接入技术(如Wi-Fi技术)融合共存的问题,逐渐成为研究焦点。因此,竞争机制中退避算法的设计成为关键。本文主要针对Wi-Fi与LAA共存的场景,基于LBT(Listen Before Talk)竞争机制,设计了三种退避算法,并在ns-3仿真平台上实现仿真,对比纯Wi-Fi环境下的性能表现,对退避算法进行合理的优化。     

可编程控制器在电源控制中的应用

详细介绍了可编程控制器及模拟量输入、输出单元DA003和AD003的功能和应用方法,给出了在电源控制中的部分应用实例。     

基于增强型智能网的接入控制及协议

本文针对个人通信系统的需求,给出一种基于公钥体系的认证和密钥约定协议的实现方案.在智能网体系结构中引入相应的接入控制实体,给出其实现结构、功能、协议和操作,描述了基于增强型智能网系统的安全接入.     

HSDPA系统中HS-SCCH的功率控制算法

为提高高速下行链路分组接入(HSDPA)系统功率的利用率,降低干扰,提出了HS-SCCH控制信道的两种功率控制算法:基于下行DPCCH导频域的功率偏移和基于CQI的功率控制.仿真表明,当信道条件好、时延小的时候,第一种算法优于第二种算法大约1～2 dB;当信道条件差、时延大的时候,第二种算法优于第一种算法大约2～5 dB.两种算法结合使用时,能达到更好的效果.     

外腔半导体激光器的场功率谱和线宽

本文采用低频近似的方法,用半经典理论,给出了外腔半导体激光器的场功率谱和线宽公式,理论分析与实验结果是吻合的。     

认知中继协同无线通信系统功率分配和混合频谱接入方案

文章首先对Underlay 认知-中继协作（cognitive radio relay cooperation, CR-RC）系统信源和中继的功率分配问题进行了研究,获得了Underlay CR-RC系统信源、中继独立功率分配(independent power allocation, IPA）和联合功率分配（joint power allocation, JPA）方案,并给出了基于IPA和JPA的CR-RC系统的中断概率和各态历经容量的封闭解析解;其次通过对Underlay CR-RC系统中断性能的比较分析,提出了高频谱效率、高能量效率的混合Interweave-Underlay CR-RC方案。在该方案中,定义了主、从用户中断概率约束,充分考虑了主、从系统的服务质量(quality of service, QoS),当即使从用户的发射功率为零,主系统的QoS仍不能满足时,从用户以最大功率发送信号,无需考虑其对主用户的影响;当由于很强的主用户干扰,使得从用户的QoS不能得到满足时,从用户不再发射信号,发信功率为零;当主、从系统的QoS能够同时满足时,以Underlay模式工作。      

LTE与非3GPP接入网的系统架构研究

首先分析了LTE与非3GPP互通系统架构配置,描述了3GPP互通系统架构中的逻辑单元（包括用户设备、非3GPP可信网络、非3GPP不可信接入网和EPC）,给出了非3GPP互通系统架构中的接口与协议,讨论了非3GPP互通系统架构中的漫游问题。     

Dynamic Spectrum Access with QoS and Interference Temperature Constraints

Spectrum is one of the most precious radio resources. With the increasing demand for wireless communication, efficiently using the spectrum resource has become an essential issue. With the Federal Communications Commission's (FCC) spectrum policy reform, secondary spectrum sharing has gained increasing interest. One of the policy reforms introduces the concept of an interference temperature - the total allowable interference in a spectral band. This means that secondary users can use different transmit powers as long as the sum of these power is less than the interference threshold. In this paper, we study two problems in secondary spectrum access with minimum signal to interference noise ratio (quality of service (QoS)) guarantee under an interference temperature constraint. First, when all the secondary links can be supported, a nonlinear optimization problem with the objective to maximize the total transmitting rate of the secondary users is formulated. The nonlinear optimization is solved efficiently using geometric programming techniques. The second problem we address is, when not all the secondary links can be supported with their QoS requirement, it is desirable to have the spectrum access opportunity proportional to the user priority if they belong to different priority classes. In this context, we formulate an operator problem which takes the priority issues into consideration. To solve this problem, first, we propose a centralized reduced complexity search algorithm to find the optimal solution. Then, in order to solve this problem distributively, we define a secondary spectrum sharing potential game. The Nash equilibria of this potential game are investigated. The efficiency of the Nash equilibria solutions are characterized. It is shown that distributed sequential play and an algorithm based on stochastic learning attain the equilibrium solutions. Finally, the performances are examined through simulations     

Beacon-Assisted Spectrum Access with Cooperative Cognitive Transmitter and Receiver

Spectrum access is an important function of cognitive radios for detecting and utilizing spectrum holes without harming the legacy systems. In this paper, we propose novel cooperative communication models and show how deploying such cooperations between a pair of secondary transmitter and receiver assists them in identifying spectrum opportunities more reliably. These cooperations are facilitated by dynamically and opportunistically assigning one of the secondary users as a relay to assist the other one, which results in more efficient spectrum hole detection. Also, we investigate the impact of erroneous detection of spectrum holes and thereof missing communication opportunities on the capacity of the secondary channel. The capacity of the secondary users with interference-avoiding spectrum access is affected by 1) how effectively the availability of vacant spectrum is sensed by the secondary transmitter-receiver pair, and 2) how correlated are the perceptions of the secondary ransmitter-receiver pair about network spectral activity. We show that both factors are improved by using the proposed cooperative protocols. One of the proposed protocols requires explicit information exchange in the network. Such information exchange in practice is prone to wireless channel errors (i.e., is imperfect) and costs bandwidth loss. We analyze the effects of such imperfect information exchange on the capacity as well as the effect of bandwidth cost on the achievable throughput. The protocols are also extended to multiuser secondary networks.     

Performance Analysis of Cognitive Radio Spectrum Access with Different Primary User Access Schemes

The cognitive access process based on different access schemes of the primary user in the spectrum sharing system of cognitive radio is studied. In the cognitive system with finite user population, the primary users access the licensed channels through random access, real-reservation access, pseudo-reservation access and non-random access. The cognitive users access the licensed channels without interfering the primary users. Their access process is modeled using the three-dimensional continuous Markov model. The performance analysis is presented with variation of the number of cognitive users. It is known from the simulated results that the handoff probability, the blocking probability and the forced termination probability of the cognitive users increase with the increase of the number of cognitive users. It is also found that the random access scheme has the highest handoff probability. And the real-reservation access scheme has the highest blocking probability and forced termination probability. In addition, the non-random access scheme has the maximum channel utilization.     

Combined Tuning of RF Power and Medium Access Control for WLANs

Mobile communication systems, such as handhelds and laptops, still suffer from short operation time due to limited battery capacity. We exploit the approach of protocol harmonization to extend the time between battery charges in mobile devices using an IEEE 802.11 network interface. Many known energy saving mechanisms only concentrate on a single protocol layer while others only optimize the receiving phase by on/off switching. We show, that energy saving is also possible during the sending process. This is achieved by a combined tuning of the data link control and physical layer. In particular, harmonized operation of power control and medium access control will lead to reduction of energy consumption. We show a RF power and medium access control trade-off. Furthermore we discuss applications of the results in IEEE 802.11 networks.     

LTE/SAE系统接入层安全性的研究与实现

伴随着移动通信的迅速发展,多样数据业务的出现对信息的安全提出了更高的要求.针对当前热门的LTE/SAE系统,提出了一种有关接入层数据安全的可行性方案.首先研究了LTE/SAE安全体系结构,重点介绍了系统接入层的安全性实现过程.该方案实现简单,对用户平面数据的安全传输具有较重要的作用.     

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。     

Energy‐Efficient Power Allocation for Cognitive Radio Networks with Joint Overlay and Underlay Spectrum Access Mechanism

Traditional designs of cognitive radio (CR) focus on maximizing system throughput. In this paper, we study the joint overlay and underlay power allocation problem for orthogonal frequency‐division multiple access–based CR. Instead of maximizing system throughput, we aim to maximize system energy efficiency (EE), measured by a “bit per Joule” metric, while maintaining the minimal rate requirement of a given CR system, under the total power constraint of a secondary user and interference constraints of primary users. The formulated energy‐efficient power allocation (EEPA) problem is nonconvex; to make it solvable, we first transform the original problem into a convex optimization problem via fractional programming, and then the Lagrange dual decomposition method is used to solve the equivalent convex optimization problem. Finally, an optimal EEPA allocation scheme is proposed. Numerical results show that the proposed method can achieve better EE performance.     

TD-SCDMA系统的外环功率控制算法研究

在3GPP协议规范中对外环功率控制算法没有定义,由各设备生产和制造商决定。TD-SCDMA系统每时隙下服务用户数较WCDMA系统每帧下服务用户数明显减少;另外,采用了自适应的智能天线技术,适合WCDMA的外环功率控制算法不能直接适用于TD-SCDMA,提出了一种先进的自适应功率调整步长的外环功率控制算法。由于外环功率控制参数对系统性能影响较大,基于自适应智能天线技术,给出了不同参数下外环功率控制算法的性能,可用于TD-SCDMA网络的规划优化。     

伺机频谱接入协同分集的中断概率

固定频谱分配政策导致频谱使用率低,为克服这一缺点,人们提出使用认知无线电技术实现伺机频谱接入,从而有效利用频谱空穴.分析了一个解码转发协作网络真实的中断概率,并且推导了独立等同、独立非等同两种瑞利信道下的中断概率,最后进行了仿真和分析.     

On the Throughput of Channel Access Algorithms with Limited Sensing

We consider some access protocols for Aloha type multiaccess channels. We argue, and show in an important case, that they can be modified to allow new transmitters to join the system at arbitrary times. This feature, known as "limited sensing" or "continuous entry," need not reduce throughput performances. In the case presented, the modified algorithm is also robust with respect to feedback errors.