共查询到20条相似文献,搜索用时 171 毫秒
1.
在多数的公网集群通信系统中,对切换的时延要求很高,如何减小切换时延变得相当重要?在公网集群通信系统中引入TD-LTE技术,使切换时延得到一定的减小,但切换过程中,基站和eMME间的频繁通信仍然增大了延时?基于背景扫描的切换算法,其思想是让eMME将其控制的所有基站下的小区的信息缓存起来,在进行切换时,eMME只需要查询自己的信息列表,从中获取目标小区的切换门限值?载频?预留的信道资源等信息,无需与目标基站通信,这样就减少基站和eMME间的频繁通信,整个切换过程主要在源基站和eMME侧完成,从而获得更低的时延? 相似文献
2.
TD-SCDMA集群系统切换研究 总被引:1,自引:1,他引:0
介绍了TD-SCDMA集群通信系统的工作方式和特点及TD-SCDMA集群通信系统的切换.结合TD-SCDMA集群系统的特点提出了适合该系统的切换流程,本流程考虑了TD-SCDMA集群通信中基于用户优先级的排队以及在通信中不同情况下目标小区的排序准则.提出了一种基于模糊数学的切换控制方法,将满足切换程度最大的相邻基站作为目标小区,同时可以计算出允许的切换延时,为小区切换提供时间参考.本算法适用于可获得用户设备的运动状态和位置信息的TD-SCDMA集群系统的切换控制. 相似文献
3.
大多数垂直行业场景可以通过公网公用或公网专用来解决,但是与公网用户不同的是,2B用户的关键网络性能需求更多集中在时延、可靠性、上行速率等方面.目前很多无线参数只能按照小区级来进行配置,也有一些参数可以按照QCI来进行配置.2B关键技术中低时延技术、GBR保障方案、RB资源预留方案、增强的可靠性技术势必对2C用户的功耗、... 相似文献
4.
5.
6.
7.
LTE是新一代通信技术的代名词,它对现有3G系统的网络结构和无线接入方式都有较大改进.在简要介绍LTE系统的网络架构及切换功能的基础上,重点介绍并比较了2种LTE切换自优化算法:常见的用户速度的负载均衡算法有效地降低了系统的掉话率,使系统的整体性能得到提高,但没有考虑到目标小区资源变化的情况;基于RSRP/RSRQ负载均衡算法综合考虑了源小区和目标小区的RSRP(参考信号接收功率)和RSRQ(参考信号接收质量),降低了系统的切换失败率,同时减少了不必要的切换,但没有考虑用户运动方向的影响.综合加权考虑多种因素,如用户的移动方向以及小区资源的变化等对切换的影响等方面均有待深入开展研究. 相似文献
8.
9.
10.
11.
随着高铁的快速发展,铁路移动通信系统对切换时延、切换成功率等要求更为苛刻。该文针对铁路长期演进(LTE-R)系统提出基于速度触发的提前切换算法,通过提前进行信令交互、设置切换预承载点切换的方式抑制过早或过迟切换所带来的通信中断、掉话等问题。通过信令流程图进行理论分析,并对长期演进(LTE)各结构类型数据计算可知,该算法均可缩短切换时延,其中TDD帧结构类型2时效果最为显著。最后通过仿真对比得到提前切换算法相比传统切换算法有着更高且更稳定的切换成功率,验证算法的有效性,为LTE-R在未来铁路专网的应用提供技术支持。 相似文献
12.
Mobility management is the most important feature of a wireless cellular communication system. Continuation of an active call
is one of the most important quality measurements in the cellular systems. Handover makes it possible for a user to travel
between various networks or cells while having a seamless connection. This paper shows that, performance of cellular network
can be increased with proposed adaptive soft handoff algorithm, which dynamically calculates the Soft handover margin based
on the received signal strength and distance. Performance is evaluated in terms of the performance metrics active set update
rate, active set size, soft handover region and probability of outage. Simulation results show that soft handover algorithm
gives better performance with adaptive soft handoff margin compared to that of fixed soft handover margin in varied propagation
conditions. 相似文献
13.
TD-SCDMA数字集群系统是集群通信系统的一个发展方向。首先介绍集群通信系统的单呼和组呼,分析这两种不同通信方式切换的特点;然后对TD-SCDMA系统的传统切换进行介绍,给出TD-SCDMA集群系统基于移动台移动速度的自适应切换算法;最后对切换性能进行简单分析。 相似文献
14.
未来网络的发展趋势是各种无线接入网络共存的异构网络环境,而垂直切换技术是融合多个异构接入网络的关键技术之一,垂直切换包括三个阶段,即系统发现、切换决策和切换执行。文中主要研究了基于上下文感知的垂直切换判决策略,并与移动垂直切换技术相结合,实现了WLAN/UMTS网络间的垂直切换,通过仿真表明该方法在吞吐量和切换时延方面都得到改善。 相似文献
15.
16.
在主动频谱切换中,预先确定目标信道存在高失效风险,从而增加切换时延的问题。该文提出一种基于混合主被动频谱切换的最优目标信道选择算法。该算法结合主动频谱切换和被动频谱切换的优点,引入最小累积切换时延评价标准,综合考虑次用户的多次中断、主用户的到达率和非理想频谱检测对次用户累积切换时延的影响,并详细分析和推导了非理想检测下次用户的累积切换时延。仿真表明,相较于主动和被动频谱切换中目标信道选择策略,在信道状态变化频繁或业务量较大等极端情况下,该算法的性能优势尤为明显。 相似文献
17.
In heterogeneous network environments, it is very important for users to provide seamless services while satisfying quality-of-service,
regardless of the connected access network. In this paper, we apply a concept of ad hoc cooperation for the vertical handoff
in the heterogeneous network. For the seamless vertical handoff of mobile nodes, a neighbor ad hoc node assists some parts
of the handoff procedures requiring large latency, such as authentication and IP registration procedures. Details of the vertical
handover operation using the ad hoc cooperation are presented and its performance is evaluated. Numerical results show that
the proposed vertical handoff procedure decreases the service disruption time and the probability of packet loss, compared
with the conventional handoff methods that do not consider the cooperation of ad hoc node. 相似文献
18.
Ju Wang Liu J.C.L. Yuehao Cen 《Selected Areas in Communications, IEEE Journal on》2003,21(10):1652-1662
The undergoing third-generation wireless network needs to support the integration of voice and multimedia data services with varying quality-of-service (QoS) requirements. It is critical that the least bit-error rate (BER) for voice traffic, World Wide Web (WWW) traffic, and streaming video traffic be guaranteed at all time. In this paper, we discussed the integration of soft handoff and dynamic spreading factor in wideband code-division multiple-access system in supporting multimedia traffic. The contribution of our work is twofold. First, the processing time of the handoff request is analyzed. We found that intensive mobile handoff might consume significant amount of access channel time and increase the delay of handoff. We, therefore, proposed a batch mechanism such that multiple handoff requests could be processed simultaneously. The average delay is reduced from 1.12 s to 800 ms at heavy handoff rate. Our second contribution is a new resource allocation algorithm, where the spreading factor and transmission power for the handoff mobiles are jointly considered to maximize the throughput. The BER requirements for the handoff mobiles and the target cell are maintained during the handoff process. The original problem is formulated into a nonlinear programming format. We proposed a procedure to simplify it into a linear constraint problem, which is solved by a revised simplex method. Numerical results show a 25% increase in throughput for WWW traffic and a 26% improvement for the video traffic. 相似文献
19.
网络切换技术不仅可以保证用户的网络连接,同时能够以较强的信号传输网络数据。网络切换技术的性能对网络服务质量(quality of service, QoS)的影响至关重要。然而,现有的切换算法多数存在严重的乒乓效应,这不仅造成网络资源的严重浪费,还会损害用户的QoS。为此,提出了一种基于强化学习的异构网络垂直切换方案,主要从触发切换、网络选择及判决切换等方面进行优化。在触发切换时将垂直切换考虑成必要切换和择优切换,通过Q-Learning(QL)算法在选择网络时优化垂直切换;然后以QoS为条件,在判决切换时加入驻留定时器,从多角度减少用户切换次数,降低乒乓效应对异构网络垂直切换的影响。仿真结果表明,基于强化学习的异构网络垂直切换方法可以在保证QoS的条件下有效减少用户切换网络的次数,短时间内频繁切换的情况也有所改善,降低了乒乓效应的影响。 相似文献
20.
Recent developments in heterogeneous mobile networks and growing demands for variety of real-time and multimedia applications have emphasized the necessity of more intelligent handover decisions. Addressing the context knowledge of mobile devices, users, applications, and networks is the subject of context-aware handoff decision as a recent effort to this aim. However, user perception has not been attended adequately in the area of context-aware handover decision making. Mobile users may have different judgments about the Quality of Service (QoS) depending on their environmental conditions, and personal and psychological characteristics. This reality has been exploited in this paper to introduce a personalized user-centric handoff decision method to decide about the time and target of handover based on User Perceived Quality (UPQ) feedbacks. The UPQ degradations are mainly for the sake of (1) exiting the coverage of the serving Point of Attachment (PoA) or (2) QoS degradation of serving access network. Using UPQ metric, the proposed method obviates the necessity of being aware about rapidly varying network QoS parameters and overcomes the complexity and overhead of gathering and managing some other context information. Moreover, considering the underlying network and geographical map, the proposed method is able to inherently exploit the trajectory information of mobile users for handover decision. UPQ degradation is not only due to the user behaviour, but also due to the behaviours of others users. As such, multi-agent reinforcement learning paradigm has been considered for target PoA selection. The employed decision algorithm is based on WoLF-PHC learning method where UPQ is used as a delayed reward for training. The proposed handoff decision has been implemented under IEEE 802.21 framework using NS2 network simulator. The results have shown better performance of the proposed method comparing to conventional methods assuming regular movement of mobile users. 相似文献