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。     

定向自组网中基于报文多时延等级的发送端调度算法

面向接收机冲突的多址接入（ROMA）是一种高效的适用于多波束自适应阵列天线的调度协议,但它无法保证具有不同时延要求的报文传输的服务质量。针对此问题,在原始ROMA的基础上提出了一种多时延限制的调度算法（MDRS）。通过在调度接入过程中插入子时隙,比较发送端报文时延信息,调度发送节点的传输顺序,使得时延限制更严格的报文优先发送,从而提高了不同时延等级的报文的传输成功率。最后,通过仿真验证了MDRS的性能：与原始ROMA相比,所提算法在多时延限制的发送端调度中表现出了更好的吞吐量和传输成功率。     

基于优先级的包插入队列调度算法仿真研究

提出一种高优先级数据包插入到低优先级数据包中发送的新型队列调度算法,该算法不仅较大幅度地降低了高优先级数据包的时延和时延抖动,同时不会降低带宽利用率,具有很强的实用性.通过OPNET建模验证了此种算法的有效性.     

一种支持多优先级的高速Crossbar调度算法

现有支持多优先级的高速Crossbar调度算法需要交互的控制信息较多,控制信息的传输时间已成为调度算法性能提高的主要瓶颈.为提高Crossbar调度的性能,本文提出一种新的支持多优先级的高速Crossbar调度算法p-iDRR,该算法具有硬件实现简单、控制信息量少、高速和可扩展性强等优点.仿真结果表明,p-iDRR具有良好的吞吐量、时延性能,适用于高速、多端口、大容量的路由器.     

基于多业务预测的EPON动态带宽分配算法

针对EPON系统中上行链路的时分复用机制,提出了一种基于多业务预测的动态带宽分配算法.该算法根据各个优先级业务的实时变化,通过一定的预测机制,实现动态分配带宽.相对其它算法,该算法能在保障高优先级业务优先的同时,降低数据时延.     

一种适用于W-CDMA系统的多业务无线资源调度算法

3G系统将以分组交换方式提供语音、数据、视频等具有不同QoS要求的多种业务，资源调度对保证系统服务质量和提高资源利用效率起关键作用．本文提出了一种基于业务类型、当前待发送负荷以及剩余延时限的时间调度策略和基于资源优化的资源调度策略，并使无线链路的传输质量与业务的优先级水平一致．通过系统仿真评价了算法的性能．     

无线MESH网络QoS机制研究*

随着无线MESH网络与实时多媒体业务的迅速发展,要求无线网络不仅能提供简单的连通性,还需要提供非常有效的QoS保证机制。针对这一需求,提出一种基于服务流映射的QoS保障机制,通过服务流定义及业务映射、基于QoS优先级的带宽预约、分级多轮调度等关键算法,实现多业务QoS保障。并通过仿真和样机测试验证QoS性能。仿真及试验结果分析表明,与无QoS机制相比,时延降低约20%,在各种链路负载下,高优先级业务丢包率维持在0.05%左右,能够很好的满足无线MESH网络多业务QoS需求。     

一种基于时延补偿的星上分组调度算法

EDF策略具有有线调度算法中最大调度域和时延保障特性,根据分组时延要求确定服务优先级,是一种动态权重调度策略,通过将IQ-VOQ结构EDF策略引入无线调度并通过加入信道补偿机制和门限丢弃策略,得到一种新的算法IQCEDF,它避开公平排队固有的时延一带宽耦合问题,获得了比EDF更加出色的时延特性,更适于为卫星通信系统分组业务提供服务质量保证。     

基于列生成的毫米波多连接链路配置调度算法

多连接技术允许用户同时建立和保持与多个小区/接入点的连接,通过网络元素之间的协调在吞吐量和可靠性方面大幅提高网络性能。针对毫米波通信中超高频段的链路中断问题,研究了多连接基于链路配置的调度算法,以提高链路调度效率,降低复杂度。首先,在系统模型中采用链路配置作为优化变量;其次,设计了多连接比例公平的调度准则;最后,提出一种基于列生成算法的链路配置调度优化算法,利用Dantzig-Wolfe分解将原问题分解为限制主问题和定价问题,并结合分支定界方法获得最优解。仿真结果表明,所提算法能够在数值上逼近全局最优,并且比现有的毫米波蜂窝网络链路调度方案增益平均提高40%以上。     

广义数据包到达的时延优化研究

在无线传感网中,Choobkar算法与Dilmaghani算法分析仅适用于在较高优先级节点空时隙时,较低优先级的节点总是有数据包要发送的情况。为此,提出了一种广义数据包到达算法(GPA)的时延分析。算法适用于数据包到达的任何模式,其中包括在较高优先级节点空时隙的情况下,较低优先级的节点可能或可能不具有待发送数据包。通过仿真验证,对比Choobkar算法和Dilmaghani算法,GPA算法的时延分析在整个负载范围内具有较好的准确度。     

Receiver-Oriented Multiple Access in Ad Hoc Networks with Directional Antennas

Directional antennas can adaptively select radio signals of interest in specific directions, while filtering out unwanted interference from other directions. A couple of medium access protocols based on random access schemes have been proposed for networks with directional antennas, using the omnidirectional mode for the transmission or reception of control packets in order to establish directional links. We propose a distributed receiver-oriented multiple access (ROMA) scheduling protocol, capable of utilizing multi-beam forming directional antennas in ad hoc networks. Unlike random access schemes that use on-demand handshakes or signal scanning to resolve communication targets, ROMA computes a link activation schedule in each time slot using two-hop topology information. It is shown that significant improvements on network throughput and delay can be achieved by exploiting the multi-beam forming capability of directional antennas in both transmission and reception. The performance of ROMA is studied by simulation, and compared with a well-know static scheduling scheme that is based on global topology information.     

Low Access Delay Anti-Collision Algorithm for Readers in Passive RFID Systems

Even though radio frequency identification (RFID) systems are spreading more and more as a medium for identification, location and tracking purposes, some reliability issues of these systems still need to be solved. In fact, RFID readers and tags experience collisions when sharing the wireless transmission channel over the same area. In this work, we propose a centralized scheduling-based algorithm as possible candidate solution for the reader collision problem in passive RFID systems. This algorithm has been designed taking into account the circuitry limitations of the tags, which do not allow the usage of frequency or code division multiple access schemes in passive RFID systems. The solution herewith proposed, which is suitable for those scenarios involving static or low mobility readers, aims at preventing reader collisions and provides at the same time low channel access delay to the readers. The performance of this algorithm has been tested via computer simulations. The results show that the proposed solution strongly reduces collision occurrences and, especially in static scenarios, provides low access delay to the readers during the channel contention phase.     

Delay Aware Link Scheduling for Multi-Hop TDMA Wireless Networks

Time division multiple access (TDMA) based medium access control (MAC) protocols can provide QoS with guaranteed access to the wireless channel. However, in multi-hop wireless networks, these protocols may introduce scheduling delay if, on the same path, an outbound link on a router is scheduled to transmit before an inbound link on that router. The total scheduling delay can be quite large since it accumulates at every hop on a path. This paper presents a method that finds conflict-free TDMA schedules with minimum scheduling delay. We show that the scheduling delay can be interpreted as a cost, in terms of transmission order of the links, collected over a cycle in the conflict graph. We use this observation to formulate an optimization, which finds a transmission order with the min-max delay across a set of multiple paths. The min-max delay optimization is NP-complete since the transmission order of links is a vector of binary integer variables. We devise an algorithm that finds the transmission order with the minimum delay on overlay tree topologies and use it with a modified Bellman-Ford algorithm, to find minimum delay schedules in polynomial time. The simulation results in 802.16 mesh networks confirm that the proposed algorithm can find effective min-max delay schedules.     

Multi-channel-based scheduling for overlay inband device-to-device communications

In this paper, we consider the problem of distributed scheduling for overlay inband device-to-device (D2D) communication systems that employ an orthogonal frequency division multiple access physical layer technology. To improve the spatial reuse gain, we propose a multi-channel-based scheduling algorithm that divides the overall radio resource dedicated to D2D communication into multiple data channels and schedules the links allocated to each channel based on a signal-to-interference-aware priority-based scheduling method. Further, we develop a cross-layer queueing model to analyze the medium-access-control layer performance of the proposed scheduling algorithm and compare the analytic results with the simulation results. We demonstrate that the proposed scheduling algorithm outperforms the existing single one-channel-based algorithm to provide lower packet dropping probability, higher spectral efficiency, and lower packet delay.     

Channel-aware priority-based groupwise packet scheduling for non-real time data service with burst-switching DS/CDMA system

The algorithm of scheduling scheme of channel-aware priority-based groupwise transmission is investigated for non-real time data service for the uplink direct sequence code division multiple access (DS/CDMA) system using the burst-switching scheme to support the integrated voice/data service. The proposed scheme optimally determines the transmission-time groups and assigns optimal data rates to the users with packets in the transmission-time group depending on priority metric, which involves several parameters such as delay threshold, waiting time, length of packet, and state of the channel, in a way of minimizing the average transmission delay. Simulation results show that the proposed algorithm gives better performance of average transmission delay and packet loss probability than any other conventional algorithms.     

一种自适应的OFDMA系统下行分组调度算法

提出了一种适合于OFDMA（正交频分多址接入）系统的资源分配与调度算法,该算法利用物理层的信道信息和MAC层的队列状态信息,并综合考虑了数据分组传输的时延要求和业务的优先级,采取资源块与子载波分配相结合的资源分配方式。仿真结果表明,该算法在吞吐量和公平性方面都得到了较好的改善。     

Medium access control in ad hoc networks with MIMO links: optimization considerations and algorithms

we present a medium access control (MAC) protocol for ad hoc networks with multiple input multiple output (MIMO) links. MIMO links provide extremely high spectral efficiencies in multipath channels by simultaneously transmitting multiple independent data streams in the same channel. MAC protocols have been proposed in related work for ad hoc networks with other classes of smart antennas such as switched beam antennas. However, as we substantiate in the paper, the unique characteristics of MIMO links coupled with several key optimization considerations, necessitate an entirely new MAC protocol. We identify several advantages of MIMO links, and discuss key optimization considerations that can help in realizing an effective MAC protocol for such an environment. We present a centralized algorithm called stream-controlled medium access (SCMA) that has the key optimization considerations incorporated in its design. Finally, we present a distributed SCMA protocol that approximates the centralized algorithm and compare its performance against that of baseline protocols that are CSMA/CA variants.     

A dynamic channel assignment algorithm for a hybrid TDMA/CDMA-TDDinterface using the novel TS-opposing technique

It has been demonstrated that code division multiple access (CDMA) provides great flexibility by enabling efficient multiuser access in a cellular environment. In addition, time division duplex (TDD) as compared to frequency division duplex (FDD) represents an appropriate method to cater for the asymmetric use of a duplex channel. However, the TDD technique is subject to additional interference mechanisms compared to an FDD system, in particular if neighboring cells require different rates of asymmetry. If TDD is combined with an interference limited multiple access technique such as CDMA, the additional interference mechanism represents an important issue. This issue poses the question of whether a CDMA/TDD air-interface can be used in a cellular environment. The problems are eased if a hybrid time division multiple access (TDMA)/CDMA interface (TD-CDMA) is used. The reason for this is that the TDMA component adds another degree of freedom which can be utilized to avoid interference. This, however, requires special channel assignment techniques. A notable example of a system which uses a TD-CDMA/TDD interface is the Universal Mobile Telecommunications System (UMTS). This paper presents a novel centralized dynamic channel assignment (DCA) algorithm for a TD-CDMA/TDD air-interface. The DCA algorithm exploits a new technique which is termed “TS-opposing technique.” The key result is that the new DCA algorithm enables neighboring cells to adopt different rates of asymmetry without a significant capacity loss     

Wireless Packet Scheduling Algorithm for OFDMA System Based on Time‐Utility and Channel State

In this paper, we propose an urgency‐ and efficiencybased wireless packet scheduling (UEPS) algorithm that is able to schedule real‐time (RT) and non‐real‐time (NRT) traffics at the same time while supporting multiple users simultaneously at any given scheduling time instant. The UEPS algorithm is designed to support wireless downlink packet scheduling in an orthogonal frequency division multiple access (OFDMA) system, which is a strong candidate as a wireless access method for the next generation of wireless communications. The UEPS algorithm uses the time‐utility function as a scheduling urgency factor and the relative status of the current channel to the average channel status as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics while satisfying quality‐of‐service (QoS) requirements of RT traffics. The simulation study shows that the UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modifiedlargest weighted delay first (M‐LWDF), while satisfying the QoS requirements of RT traffics such as average delay and packet loss rate under various traffic loads.     

Throughput evaluation of a satellite-switched CDMA (SS/CDMA) demandassignment system

This paper presents throughput evaluation of a satellite-switched code-division multiple-access (SS/CDMA) system which operates under demand assignment control. SS/CDMA provides both multiple access and switching to a geostationary multibeam satellite. Multiple access is resolved by space, frequency, and code division. Space division is introduced by the multibeam antennas that provide frequency reuse in each beam. The spectrum is then channelized into frequency bands where each band is accessed by code division for both the uplink and downlink. The satellite on-board performs the switching function, which is also based on compatible code-multiplexed switching. The switch may route both circuit calls and data packets which are assigned upon request. The on-board code-division switch operates under the control of a channel assignment algorithm. We provide channel assignment algorithms for optimum, suboptimum, and random switch operation. The system throughput has been evaluated for each case and compared. Performance analysis has been carried out for the case of the optimum switch scheduling. The analysis is based on a discrete-time Markovian model, and provides the call-blocking probabilities and data packet delays. Computer simulations have been used to evaluate the performance of the optimum, suboptimum, and random cases. It is shown that the circuit call-blocking probabilities achieved for these cases are almost the same. The optimum algorithm achieves the minimum data packet delay, while the performance of the suboptimum algorithm is slightly better than the random one. Furthermore, data packets may be routed via the switch with limited delays, even with a heavy load of circuit calls