TDMA时隙分配对业务时延性能的影响分析

 在TDMA通信系统中,时隙分配是影响业务时延性能的重要因素,包括时隙数量分配(带宽分配)、时隙分配周期(TDMA帧长)和时隙位置分配三方面.本文针对可变速率和固定速率两类业务,基于随机服务系统理论和交通流理论建立了业务时延模型,得到了平均时延的解析式,分析了时隙数量、时隙位置和TDMA帧长度对业务时延影响的规律和特点.结果表明时隙位置分配越均匀,越能改善业务的平均时延和时延抖动性能;而在传统的时隙连续分配方式下,增加时隙数量分配对时延性能提高非常有限.在DVB-RCS卫星系统等具有较长帧设计的TDMA系统中,采用时隙均匀分配方式能够有效提高业务时延性能.计算机仿真验证了建模分析的正确性.     

实时WDM网络的全光流量疏导算法

为解决波分复用(Wavelength Division Multiplexing,WDM)网络中实时性业务流疏导问题,提出一种考虑了网络端对端延迟的疏导算法.建立了WDM网络模型和实时消息模型,用网络演算理论分析了有连续时隙和没有连续时隙分配下实时消息的端对端的最大延迟,并推导出了算法的延迟关键性参数时隙距离.提出的实...     

分布式TDMA网络的时隙设计技术

时隙分配是分布式TDMA组网的一个基础性工作,直接影响到Adhoc网络的性能。为支持低延迟数据业务,通常选择TDMA组网技术,但常规的固定时隙TDMA网络对时隙的利用率较低。提出了一种基于跳频的固定时隙分配和动态时隙分配相结合的TDMA时隙资源管理技术,有效地解决了TDMA网络的不同类型用户信息传输时隙分配问题。     

一种新的有效支持智能天线应用的多址接入协议

本文研究将智能天线应用于分组无线网络中,提出了支持智能天线应用的自适应时隙分配多址接入协议(ASAMA).该协议采用时分双工(TDD)方式,每一帧开始时用户节点依次发送训练序列,基站的智能天线据此计算出各用户节点的空间特征(Spatial Signature).基于波束形成的信干噪比最大化准则,设计了逐点优化与全局优化两种不同复杂度的时隙分配算法.由基站对上下行业务的时隙进行动态分配,在保证通信质量的前提下,使每个时隙容纳多个数据分组,以充分实现信道的空分复用(SDMA).对该协议的信道利用率进行了近似分析,并利用仿真方法考察其性能.结果表明,ASAMA协议能有效支持智能天线应用并具有很高的信道利用率与良好的时延性能.     

CDMA/TDD系统的动态信道分配策略

为了适应上下行业务的不对称性,针对CDMA/TDD系统的动态信道分配(DCA),在慢速动态信道分配方面,提出了根据在线语音用户数和基于上下行数据业务比预测来动态分配上下行时隙数的策略,分析了此策略中上下行业务变化速率和时隙分配速率之间的关系对系统性能的影响。对于快速动态信道分配则设计了一种适用于多业务的呼叫接入控制算法,它对语音业务基于保护信道法而对语音和数据业务之间采取可移动边界法。仿真结果表明:提出的方案可以提供更高的数据处理能力而不影响语音业务的性能,而且信道利用率也得到提高。     

一种新的EPON动态带宽分配方法的研究

传统的EPON系统的上行带宽分配方案是类似于IPACT的基于时隙长度分配的,这样虽然使上行信道得到了充分的利用,但是由于包延迟变化较大,不适合实时业务的传送.介绍了一种混合时隙长度/速率DBA方案,它可以为不同业务提供不同的QoS,既满足了实时业务的需要,又在一定程度上提升了网络的利用率.     

一种TD-SCDMA动态信道分配的改进方案

在TD-SCDMA系统中,由于对上下行不对称业务的需求,使得不同小区间的上下行切换点不同,因此会产生严重的小区间干扰(基站和基站间干扰)。提出一种基于移动台位置的抗基站间干扰的动态信道分配(DCA)的改进方案,它通过增大交叉时隙的空间隔离度和减少交叉时隙的使用机率来改善基站间的相互干扰,同时使每个时隙的用户空间分布更加均匀,最大化提高系统容量,改善非对称业务下系统的整体性能。     

数据链动态时隙分配算法与仿真

在现有时隙分配方式基础上,提出了从时隙预分配、时隙动态需求预测、时隙动态分配计算和时隙调整四个步骤实施的动态时隙分配算法,并进行了仿真分析。仿真结果表明时隙动态分配能提高时隙利用率,最大程度地保证战术数据的传输性能。     

TD-SCDMA系统动态信道分配的改进方案

在时分同步码分多址(TD-SCDMA)系统中由于对上下行不对称业务的需求,不同小区间的上下行切换点不同,因此会产生严重的小区间干扰(基站和基站间干扰)。文章提出了一种基于移动台位置的抗基站间干扰的动态信道分配(DCA)的改进方案,它通过增大交叉时隙的空间隔离度和减少交叉时隙的使用机率来改善基站间的相互干扰,同时使每个时隙的用户空间分布更加均匀,最大化提高系统容量,改善非对称业务下系统的整体性能。     

EPON支持QoS的动态带宽算法研究

本文给出了一种支持多优先级业务的带宽分配算法。其中高优先级业务固定带宽分配和低优先级业务动态带宽分配,将上行帧分为第一时隙和第二时隙两部分,各ONU高优先级业务在上行第一时隙发送,第二时隙用于低优先级业务,同时采用固定周期的带宽分配方案,因此降低了高优先级业务的时延和时延抖动。通过ONU实行内部调度并且参与上行接入计算,避免了上行复杂的同步问题,提高了链路利用率。     

Dynamic congestion-based pricing of bandwidth and buffer

We consider pricing of network resources in a reservation-based quality-of-service architecture. The pricing policy implements a distributed resource allocation to provide guaranteed bounds on packet loss and end-to-end delay for real-time applications. Distributed pricing roles are assigned to each user, each network node, and an arbitrager in between the user and the network. When delay constraints are not binding, we investigate two dynamic pricing algorithms using gradient projection and Newton's method to update prices, and prove their convergence. We analyze the performance of the dynamic pricing policies and show that the gradient algorithm using Newton's method converges more quickly and displays only a few small fluctuations. When delay constraints are binding, we investigate subgradient methods which can provide convergence to some range of the optimal allocation.     

Minimizing call setup delay in ATM networks via optimal processingcapacity allocation

This paper considers the problem of process allocation in designing real-time call setup for asynchronous transfer mode (ATM) networks. With the constraint of finite processing capacity in a realistic ATM switching system, we aim to minimize the call setup delay by avoiding the potential bottleneck process. Our approach is to distribute and balance the processing loads among call control processes via optimal capacity allocation. The derived results can provide important and useful guidelines in system design and performance evaluation     

Dynamic bitrate allocation of interactive real-time streamed multi-view video with view-switch prediction

In multi-view video (MVV), the real-world scene is usually captured by more than two cameras positioned in an array. A viewer can consume MVV using either a non-interactive or an interactive transmission method. In the context of interactive MVV streaming, view switching may cause a long delay due to the frequent requests by the viewer. In this paper, we consider the use case of real-time interactive MVV (IMVV) streaming, where the view switching delay problem has a significant user experience impact. Our proposed method compress and send all the captured views using a dynamic bitrate allocation method. Also, a novel prediction algorithm has been used to choose possible views that the user might switch to. The predicted view switching is mapped to a hidden Markov model, and the transition probability is solved using Zipf distribution. The experimental results of the proposed method show a superior performance on an objective metric and view-switching delay for better viewing quality over the existing method.     

Resource allocation for real-time traffic in unreliable wireless cellular networks

Providing reliable transmission for real-time traffic in wireless cellular networks is a great challenge due to the unreliable wireless links. This paper concentrates on the resource allocation problem aiming to improve the real-time throughput. First, the resource allocation problem is formulated as a Markov Decision Process and thus the optimal resource allocation policy could be obtained by adopting the value iteration algorithm. Considering the high time complexity of the optimal algorithm, we further propose an approximate algorithm which decomposes the resource allocation problem into two subproblems, namely link scheduling problem and packet scheduling problem. By this method, the unreliable wireless links are only constrained in the link scheduling problem, and we can focus on the real-time requirement of traffic in packet scheduling problem. For the link scheduling problem, we propose the maxRel algorithm to maximize the long-term network reliability, and we theoretically prove that the maxRel algorithm is optimal in scenarios with dynamic link reliabilities. The Least Laxity First algorithm is adopted for the packet scheduling problem. Extensive simulation results show that the proposed approximate resource allocation algorithm makes remarkable improvement in terms of time complexity, packet loss rate and delay.     

Utility Based Short-term Throughput Driven Scheduling Approach for Efficient Resource Allocation in CDMA Wireless Networks

In this paper, we address the problem of efficient recourse allocation in CDMA wireless networks supporting multimedia services with various and often diverse QoS prerequisites, placing special emphasis on real-time services’ essential requirements satisfaction. We first provide an analytical framework for studying real-time users’ short-term delay and throughput properties under fundamental opportunistic scheduling policies. The corresponding results demonstrate that probabilistic delay constraints are insufficient indicators of real-time services’ QoS prerequisites, while probabilistic short-term throughput requirements are more appropriate in asserting their performance expectations. Based on these observations and results, we propose and develop a scheduling policy for efficiently supporting heterogeneous services that include delay-tolerant non-real-time and delay-sensitive real-time services, over a wireless CDMA system under a common utility based framework. A user’s utility characterizes his degree of satisfaction for the received service as well as QoS expectations fulfillment, in a normalized way. Aiming at the maximization of users’ utilities, both non-real-time services’ long-term and real-time services’ short-term throughput QoS requirements are met, under the proposed opportunistic scheduler. Finally, via modeling and simulation it is demonstrated that significant performance improvements concerning both types of services’ QoS requirements satisfaction are achieved through the proposed scheduling approach.     

Earliest Deadline First Scheduling with Active Buffer Management for Real-Time Traffic in the Internet

We studied the problem of QoS guarantee for differentiated services. A two-level hierarchical scheduling framework was deployed to separate QoS metrics. Due to its desirable property of minimizing the maximum packet lateness, the Earliest Deadline First (EDF) scheduling was adopted to provide the in-class scheduling for the time-sensitive traffic. We employed an EDF scheduler combined with an active buffer management scheme (CHOKe) to improve the fairness of resource allocation and to maintain a good delay performance for real-time applications. Simulation results showed that the proposed scheme can achieve a better delay performance and make a more fair bandwidth allocation between the real-time TCP and UDP connections than the First Come First Served (FCFS) scheduling with the drop-tail buffer management which is commonly deployed in traditional IP routers.     

Traffic management techniques to face the effects of intrinsicdelays in geostationary satellite networks

A new scheme for the management of real-time traffic over high-latency broadband satellite networks is described. Early studies on this topic have been reported by Iera, Molinaro and Marano (see IEEE J. Select Areas Commun.,, vol.18, p.2393-2403, 2000), with reference to an integrated terrestrial-satellite platform. In this paper, further enhancement is introduced into the traffic management scheme with a view to both the reduction of intrinsic impairments caused by the adverse operational environment and the achievement of better performance levels and QoS guarantees. A real-time traffic handling strategy, including distributed connection admission control (CAC) and traffic resource management (TRM) schemes, is harmonized with an in-band signaling technique for burst-based bandwidth request and with an effective policy for the allocation of radio resources. Furthermore, the impact of traffic reshaping at the satellite terminal on the CAC-TRM technique is tested. Added features reduce the adverse effects of the long propagation delay across the satellite link and show outstanding effectiveness in improving CAC-TRM performance and network resource efficiency, while matching service quality requirements. The main reason for the improved performance of the overall management scheme is the adaptability to different traffic profiles conveyed over satellite links     

Credit-based processor sharing for decoupled delay and bandwidthallocation

We propose a credit-based processor sharing (CPS) approach for decoupled allocation of delay and bandwidth. For bandwidth guarantees, a CPS system serves traffic flows in proportion to their service weights. For delay guarantees, on the other hand, a CPS system allows real-time flows to temporarily borrow bandwidth from nonreal-time flows using service credits. This borrowing mechanism boosts the delay performance of real-time flows without increasing their long-term bandwidth requirements. By systematically regulating service credits of real-time flows, nonreal-time flows are protected for their aggregate long-term bandwidth share     

Efficient Uplink Bandwidth Request with Delay Regulation for Real-Time Service in Mobile WiMAX Networks

The emerging broadband wireless access technology based on IEEE 802.16 is one of the most promising solutions to provide ubiquitous wireless access to the broadband service at low cost. This paper proposes an efficient uplink bandwidth request-allocation algorithm for real-time services in Mobile WiMAX networks based on IEEE 802.16e. In order to minimize bandwidth wastage without degrading quality of service (QoS), we introduce a notion of target delay and propose dual feedback architecture. The proposed algorithm calculates the amount of bandwidth request such that the delay is regulated around the desired level to minimize delay violation and delay jitter for real-time services. Also, it can increase utilization of wireless channel by making use of dual feedback, where the bandwidth request is adjusted based on the information about the backlogged amount of traffic in the queue and the rate mismatch between packet arrival and service rates. Due to the target delay and dual feedback, the proposed scheme can control delay and allocate bandwidth efficiently while satisfying QoS requirement. The stability of the proposed algorithm is analyzed from a control-theoretic viewpoint, and a simple design guideline is derived based on this analysis. By implementing the algorithm in OPNET simulator, its performance is evaluated in terms of queue regulation, optimal bandwidth allocation, delay controllability, and robustness to traffic characteristics.     

A spectrum-efficient algorithm based on traffic splitting and merging transmission for anycast in inter-datacenter elastic optical networks

Anycast is attracting much attention due to the need of scalable and cost-effective data delivery in inter-datacenter elastic optical networks. However, spectrum fragmentation degrades network’s performance and decreases probability of successful anycast delivery significantly. When the idle spectrum block in elastic optical network is not enough to transmit the anycast request, spectrum splitting with multi-path transmitting the anycast is an effective approach to improve the spectrum fragmentation utilization. For improving spectrum utilization and reducing time delay between multiple paths, we propose a spectrum-efficient algorithm based on traffic splitting and merging (Anycast_SA_TSM) transmission to avoid spectrum fragmentation and delay between multiple paths. In order to minimize the time delay between multiple paths, we design a modified scheme to select the multiple paths with minimal time delay to transmit the anycast. During the spectrum allocation phase, a new spectrum block allocation scheme, the exact fit or fragmentation minimal, is put forward. Moreover, when an appropriate size of spectrum block is found for the split anycast request, merging split sub-requests to a single path is activated for minimizing the additional guard bands and improving the spectrum efficiency. Comparing with other two anycast algorithms, simulation results show that the proposed algorithm can get minimal time delay between split multiple paths, the minimal bandwidth blocking probability and the highest spectrum utilization.