基于设备能耗分簇的M2M通信随机接入方法

针对机器对机器(Machine to Machine, M2M)通信设备数量的持续增大导致M2M通信在当前蜂窝网络架构下会产生网络拥塞和接入成功率下降的问题,提出了一种基于设备能耗率分簇的M2M通信随机接入方法。该方法中M2M通信设备根据自身能量消耗率划分优等簇,即能耗率越大其优等级越高,优等级高的簇内设备享有随机接入资源的优先分配权,其随机接入资源由每簇的簇头代表簇接收,并在簇内设备之间通过随机接入竞争过程实现分配。仿真结果表明,相对于接入级限制(Access Class Barring, ACB)方法,该方法在接入成功率方面提升约5%,在延迟方面降低约10 s,能够有效降低设备能耗,提高设备接入的成功率。     

TD-LTE随机接入前导码优先级控制算法

对TD-LTE系统随机接入过程进行分析,提出一种基于前导码优先级的随机接入前导码选择控制算法,增加基于优先级的前导码,由专用用户优先使用,由此减少系统广播资源,降低接入时延,提高接入成功率,解决碰撞问题。仿真结果证明,该算法可提高网络不同负载情况下的接入成功率。     

基于终端分组的非正交随机接入资源分配方案

为了解决机器到机器(Machine to Machine,M2M)通信中的冲突碰撞、资源短缺等问题,提出了基于终端分组的非正交随机接入和数据传输(Non-Orthogonal Random Access and Data Transmission based on Terminal Grouping,TG-NORA-DT)方案。首先,根据能量消耗速度对机器类型通信设备(Machine Type Communication Devices,MTCDs)进行分组,并对组设定优先级,优先级高的组MTCDs优先分配接入资源。其次,利用到达时间的差异,识别出选择相同前导码的多个MTCDs,且在随后的接入过程中实现冲突MTCDs的功率复用。最后,基于TG-NORA-DT方案,提出一种资源分配方法,以实现在物理随机接入信道(Physical Random Access Channel,PRACH)和物理上行共享信道(Physical Uplink Shared Channel,PUSCH)间的资源合理分配。仿真结果表明,与正交随机接入数据传输协议(Orthogonal Random Access and Data Transmission Protocol,ORADTP)和非正交随机接入的数据传输(Non-Orthogonal Random Access-Data Transmission,NORA-DT)方案相比,TG-NORA-DT方案提高了系统吞吐量和资源利用率,降低了前导码冲突概率,其中资源利用率提高了20%以上。     

M2M设备远程签约信息管理研究

M2M通信被看作是一种可能没有人际互动的实体与实体之间的通信形式.它面临的一个重大挑战是设备在没有人员值守的情况下的远程管理问题.针对此问题,3GPP标准化组织提出了一种基于可信环境(Trusted Environment,TRE)的M2M设备远程签约信息管理方案和基于通用集成电子卡(Universal Integrated Circuit Card,UICC)的两类解决方案.前者不需要给每一个设备安装UICC,而是可以将重要的认证数据和功能集成在M2M设备上TRE模块里.最后对方案的安全性和性能作了进一步研究和说明.     

一种M2M网络中的能量有效媒体访问控制协议

为了减小M2M网络中MAC(媒体访问控制)层接入冲突,提高数据传输效率和节点能量利用效率,提出了一种新的混合分组协议HG-MAC(Hybrid and Grouping MAC);HG-MAC混合利用基于调度与基于竞争的两种接入方式;对节点进行分组分层管理,减少冲突和提供QoS保障;采用休眠机制提高能量利用效率;引入动态调整机制和可变帧长度提高协议灵活性;通过建立二维马尔可夫链,对竞争时长与数据传输速率之间的关系进行了理论分析;利用OPNET仿真工具,将HG-MAC与CSMA/CA和TDMA的性能进行了仿真比较;结果表明HG-MAC在数据传输速率、能量效率和信道利用率上具有一定的优势。     

LTE系统中M2M业务随机接入优化方案

针对LTE系统中海量M2M终端同时接入引起的频繁碰撞问题, 提出一种基于分组的解决方案。将同一小区内的M2M终端划分成组并引入组长节点, 由组长代表本组发起接入请求, 基站根据当前负荷情况分配接入资源并通过组寻呼触发组员节点的随机接入过程。理论分析和系统级仿真实验结果表明, 相比LTE系统, 现有的随机接入策略新方案在终端数量较多时能够有效减少碰撞次数, 提高首次接入的成功概率。     

LTE-A中基于时隙接入的接入拥塞控制优化算法

在LTE-A中，由于物理随机接入信道(Physical Random Access Channel，PRACH)资源有限，当大量的设备几乎同时地向基站发起随机接入请求时，可能会导致接入网拥塞，接入时延增大，无法满足用户的服务质量需求。通过分析时隙接入模型，提出了一种自适应调整时隙接入周期的接入控制优化方案。与基于时隙接入的信道接入控制协议(slotted-access-based channel access control protocol，SCACP)相比，所提方案首先通过实时接入负载的估计，优化时隙接入周期的选择，均衡了接入时隙的接入请求，既保障了设备的接入成功率，又减少了不必要的前导重传，降低了接入时延。最后，仿真结果验证了所提接入控制优化方案的有效性。     

面向M2M通信的传输控制机制与方法

M2M通信是物联网的重要组成部分,其中基于IP的M2M通信方式实现了网络节点的统一编址、统一协调和统一管理,成为当前的研究重点和热点。传统TCP差错控制机制把数据丢失原因简单地归结为网络拥塞,并采用拥塞控制机制来解决,而忽略了无线连接存在的链路高比特误码率、拓扑频繁变化、信道非对称性、MAC协议的不公平性等缺陷,使得传统TCP不适合在高可靠性M2M通信中使用。分析了影响M2M通信的TCP因素和改进方法,以端对端连接、拆连接和混合连接3种方式分别讨论了相应的解决方案,提出了TCP在M2M通信中的改进思路和研究方向。     

M/G/1排队网络系统性能研究

本论文以单一路由器(服务器)为例,从最原始的队列理论出发,探讨具有容量C的M/G/1队列模型的系统平均时延、系统稳态下的报文(用户)平均值、以及时延等问题。并对报文(用户)的服务质量需求作了详尽的数学推导。     

支持机器类型通信的动态接入拦截方法

对提升机器到机器(M2M)通信的接入成功率进行研究,在分组接入拦截(ACB)方案的基础上,提出一种加入自适应调整机制的改进方法。应用近似最大后验概率(AMAP)算法对等待接入的机器设备(MDs)数做出比较准确的估计,基于这种估计动态地调整ACB拦截参数,强化对负载和接入尝试的控制,提升对先导序列资源的利用率和接入成功率。仿真结果表明该方法可行有效。     

Efficient cooperative access class barring with load balancing and traffic adaptive radio resource management for M2M communications over LTE-A

We propose two efficient cooperative access class barring with load balancing (CACB-LB) and traffic adaptive radio resource management (TARRM) schemes for M2M communications over LTE-A. The proposed CACB-LB uses the percentage of the number of Machine-Type Communication (MTC) devices that can only access one eNB between two adjacent eNBs as a criterion to allocate those MTC devices that are located in the overlapped coverage area to each eNB. Note that an eNB is a base station of LTE-A. In this way, the proposed CACB-LB can achieve better load balancing among eNBs than CACB, which is the best available related work. The proposed CACB-LB also uses the ratio of the channel quality indication that an MTC device received from an eNB over the number of MTC devices that attach to the eNB as a criterion to adjust the estimated number of MTC devices that may access the eNB. As a result, the proposed CACB-LB can have a better set of barring rates of access class barring than CACB and can reduce random access delay experienced by an MTC device, which is also applicable to user equipment (UE). After an MTC device successfully accesses to an eNB, the eNB needs to allocate radio resources for the MTC device. In addition, the proposed TARRM allocates radio resources for an MTC device based on the random access rate of the MTC device and the amount of data uploaded and downloaded by the MTC device in a homogeneous MTC device network, and the priority of an MTC device in a heterogeneous MTC device network. Furthermore, we use the concept from cognitive radio networks such that if there are unused physical resource blocks (PRBs) of UEs, an eNB can schedule MTC devices to use these PRBs to enhance the throughput performance. Simulation results show that either in a homogeneous MTC device network or in a heterogeneous MTC device network, the proposed CACB-LB’s average access delay of UEs/MTC devices and average throughput from UEs/MTC devices are better than CACB’s. The proposed CACB-LB with TARRM’s average throughput from UEs/MTC devices is also higher than CACB’s. Therefore, the proposed CACB-LB with TARRM is feasible for M2M communications over LTE-A.     

Dynamic LTE resource reservation for critical M2M deployments

Machine-to-machine (M2M) communications are envisioned to be major contenders for long term evolution (LTE) cellular resources in the time of fifth generation (5G) wireless communications and beyond. They will be used for a variety of applications on which users will rely for managing many aspects of their daily life. One of the promising fields in which M2M communications can play a major role is the field of emergency services. In such situations, it is crucial to ensure the reliable allocation of communication resources to M2M communications to ensure the right decisions and actions are taken in a timely manner. One of the techniques that could be used to ensure sustained and reliable resource allocation is to use an LTE-based virtual resource-slicing scheme. This scheme ensures a dynamic and an uninterrupted allocation of the resources dedicated to M2M communications in such a way that accommodates the changing needs of the emergency operations. In this paper, we introduce two schemes to allocate LTE resources to M2M emergency deployments in an adaptive manner. These schemes ensure that the resource allocation responds to the changing needs of the underlying emergency application. The adaptation period is also varied in response to the speed of change of the allocation requirements. This is done to ensure that the devices involved in critical missions are not competing for resources with the rest of network clients. We conduct several experiments to assess the success of the proposed schemes in responding to the needs of emergency M2M deployments.     

异构移动终端能量感知的P2P数据共享机制

针对现有P2P数据共享网络中存在的移动终端异构性这一问题,提出一种异构移动终端能量感知的P2P数据共享机制。该机制在判断移动终端类型的同时引入能量感知模块,用于预测终端的剩余能量,在此基础上,根据网络环境的变化动态地调整数据的共享策略。仿真实验表明,该机制能够有效提高移动终端的能量利用率,平衡终端的负载,延长数据共享时间,从而提高数据分发成功率。在保持文件高可用性的前提下,平均减少15%的终端能耗。     

无线网络数据帧新型传输策略及仿真

该文针对IEEE802．11无线Adhoe网络提出了一种新型的帧传输策略。IEEE802．11无线网络标准支持分布式协调功能(DCF),即带冲突避免的载波监听多点接入(CSMA／CA),在数据传输过程中使用“请求发送-确认发送-数据-接收确认(RTS-CTS-DATA-ACK)”模式。但是当数据帧长度较短时,很多带宽被浪费在信道竞争上,而且降低了信道传输成功率,减少了网络吞吐量。因此,根据每个帧携带的延时(Duration)值,调整站点的网络分配向量(NAV),以此来动态调整数据帧的长度,从而增大网络传输的成功率,提高网络的吞吐量,减小整个网络的传送时延。将这种数据单元长度动态调整的帧传输策略简记为DTUL。     

面向工业无线网络的动态TDMA系统设计与实现

随着工业4.0的发展, 不同种类的新型工业应用被部署到工厂中, 这对现有工业无线技术提出了实时性和高速率的要求. 为了同时满足这两种需求, 本文在支持高速率的IEEE802.11的基础上, 提出了基于软件定义的动态时分多址(Time division multiple access, TDMA)机制无线接入系统. 首先, 为了提供时延有界的传输服务, 设计并实现了基于MAC (Medium access control)层的动态TDMA接入机制. 然后, 为了满足工业无线网络中的动态变化的带宽需求, 考虑设备数据量的动态变化, 在SDN (Software defined network)控制器上通过基于最小二乘法的线性回归算法预测设备时隙需求, 再将动态时隙分配问题转化为优化问题以最大化网络中所有设备动态时隙需求. 最后, 通过仿真对比TDMA时隙分配算法的性能, 并在实际网络环境中开展系统部署与测试. 结果表明, 相对于其他TDMA接入机制, 动态TDMA机制在保障时延有界的同时能有效提升传输性能.     

Low-delay rate control for real-time H.264/AVC video coding

This paper presents an efficient rate control scheme for the H.264/AVC video coding in low-delay environments. In our scheme, we propose an enhancement to the buffer-status based H.264/AVC bit allocation method. The enhancement is by using a PSNR-based frame complexity estimation to improve the existing mean absolute difference based (MAD-based) complexity measure. Bit allocation to each frame is not just computed by encoder buffer status but also adjusted by a combined frame complexity measure. To prevent the buffer from undesirable overflow or underflow under small buffer size constraint in low delay environment,the computed quantization parameter (QP) for the current MB is adjusted based on actual encoding results at that point. We also propose to compare the bits produced by each mode with the average target bits per MB to dynamically modify Lagrange multiplier (/spl lambda//sub MODE/) for mode decision. The objective of QP and /spl lambda//sub MODE/ adjustment is to produce bits as close to the frame target as possible, which is especially important for low delay applications. Simulation results show that the H.264 coder, using our proposed scheme, obtains significant improvement for the mismatch ratio of target bits and actual bits in all testing cases, achieves a visual quality improvement of about 0.6 dB on the average, performs better for buffer overflow and underflow,and achieves a similar or smaller PSNR deviation.     

基于AHP的分布式星群接入策略研究

分布式星群网络是打赢未来信息化战争的有利武器,星群的接入技术对于提升我国空天信息获取能力具有重要意义。针对分布式星群网络高动态拓扑导致资源利用不充分的问题,提出了一种基于层次分析法的分布式星群网络接入策略。该接入策略首先是利用层次分析法动态计算资源利用率各指标权重;其次是根据各卫星节点的实时资源情况,动态调整资源利用率的权重。仿真表明,该接入策略降低了分布式星群网络的新呼叫阻塞率和强制中断率,有效地解决了星群网络资源利用率问题,提高了星群网络群内业务分配的合理性。     

基于联合优先级调度的协作动态频谱分配机制设计

在协作频谱接入过程中,共享频谱各网络中的频谱需求呈现高度动态性,现有机制难以兼顾分组传输时延和服务公平性。针对这一问题,提出一种基于联合优先级调度的协作动态频谱分配机制。将频谱分配问题建模为比例公平模型并联合网络的服务等级和用频请求的到达时间为各网络设定动态服务优先级,解得分配结果后,基于分配频谱的中心频率与需求频谱的中心频率最近的原则将频谱资源分配给各网络。仿真结果表明,与已有的基于网络固定优先级调度、基于网络动态优先级调度和基于用频请求动态优先级调度的协作频谱分配机制相比,本机制能够更好地保证网络获取频谱的公平性,并且在分组传输时延性能上有所改进。