MIMO Broadcast Scheduling with Limited Feedback

We consider multiuser scheduling with limited feedback of partial channel state information in MIMO broadcast channels. By using spatial multiplexing at the base station (BS) and antenna selection for each user, we propose a multiuser scheduling method that allocates independent information streams from all M transmit antennas to the M most favorable users with the highest signal-to-interference-plus-noise ratio (SINR). A close approximation of the achievable sum-rate throughput for the proposed method is obtained and shown to match the simulation results very well. Moreover, two reduced feedback scheduling approaches are proposed. In the first approach, which we shall refer to as selected feedback scheduling, the users are selected based on their SINR compared to a predesigned threshold. Only those selected users are allowed to feed back limited information to the BS. The resultant feedback load and achievable throughput are derived. It will then be demonstrated that with a proper choice of the threshold, the feedback load can be greatly reduced with a negligible performance loss. The second reduced feedback scheduling approach employs quantization for each user, in which only few bits of quantized SINR are fed back to the BS. Performance analysis will show that even with only 1-bit quantization, the proposed quantized feedback scheduling approach can exploit the multiuser diversity at the expense of slight decrease of throughput.     

基于约束判决的二次门限检测

该文针对微弱回波信号的检测,在二次门限检测过程中引入约束判决。就约束判决对总虚警概率的改善作用及对总检测概率的影响进行了定量分析,建立了基于约束判决的二次门限检测总虚警概率和总检测概率的数学模型,并对模型的有效性进行了仿真验证。仿真结果表明,将约束判决引入二次门限检测可以保证在总检测概率和总虚警概率满足预定指标的条件下降低对信噪比的要求。     

An enhanced channel-quality indication (CQI) reporting scheme for HSDPA systems

A major evolution of UMTS standard is the high speed downlink packet access (HSDPA). One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. This letter proposes an enhanced CQI reporting scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The proposed scheme uses a dynamic threshold to filter off redundant CQI reports. With the proposed scheme, the battery capacity of UK can be conserved, maintaining the performance of traditional CQI reporting scheme.     

一种多信道的分簇式短波令牌协议

传统的短波令牌协议( HFTP)调度方式单一,在没有数据传送时,信道资源会被各节点间的令牌传递所占用,且令牌在通信质量较差时易丢失。基于此,提出一种多信道的分簇式短波令牌协议( CHFTP),通过以通信质量评估为标准的分簇算法和基于预约的动态令牌调度,减小了令牌丢失的概率和令牌传递、处理的开销,并给出了仿真分析。仿真结果表明,该协议的端到端平均时延和网络吞吐量明显优于短波令牌协议, CHFTP 的平均时延最多可减少75%,网络吞吐量最多可增加66.7%,适合在短波通信网络中使用。     

The iSLIP scheduling algorithm for input-queued switches

An increasing number of high performance internetworking protocol routers, LAN and asynchronous transfer mode (ATM) switches use a switched backplane based on a crossbar switch. Most often, these systems use input queues to hold packets waiting to traverse the switching fabric. It is well known that if simple first in first out (FIFO) input queues are used to hold packets then, even under benign conditions, head-of-line (HOL) blocking limits the achievable bandwidth to approximately 58.6% of the maximum. HOL blocking can be overcome by the use of virtual output queueing, which is described in this paper. A scheduling algorithm is used to configure the crossbar switch, deciding the order in which packets will be served. Previous results have shown that with a suitable scheduling algorithm, 100% throughput can be achieved. In this paper, we present a scheduling algorithm called iSLIP. An iterative, round-robin algorithm, iSLIP can achieve 100% throughput for uniform traffic, yet is simple to implement in hardware. Iterative and noniterative versions of the algorithms are presented, along with modified versions for prioritized traffic. Simulation results are presented to indicate the performance of iSLIP under benign and bursty traffic conditions. Prototype and commercial implementations of iSLIP exist in systems with aggregate bandwidths ranging from 50 to 500 Gb/s. When the traffic is nonuniform, iSLIP quickly adapts to a fair scheduling policy that is guaranteed never to starve an input queue. Finally, we describe the implementation complexity of iSLIP. Based on a two-dimensional (2-D) array of priority encoders, single-chip schedulers have been built supporting up to 32 ports, and making approximately 100 million scheduling decisions per second     

基站协作系统下行链路中基于不同QoS的用户调度策略

在基站协作通信中,协作用户的调度是关键的问题之一。传统的用户调度方法为了片面追求小区的边缘传输速率与平均传输速率,造成了资源分配的不合理。本文着眼于最大限度地提升小区用户容量,提出了一种基于用户服务质量的调度策略,依据用户的需求速率和允许时延等条件确定优先级合理地调度分配资源,同时兼顾考虑小区吞吐率的提升。仿真结果表明,与原有的用户调度策略相比,该策略能够以较小的吞吐率损失为代价,大大提高了小区的用户容量。      

基于TG-PF的LTE-A中继蜂窝网络下行分层调度方法

设计了一种中继蜂窝网络的分层调度模型,将中继蜂窝小区的资源调度过程分为高层调度和低层调度两部分,分别由基站和中继站完成。所设计模型中,高层调度和低层调度分别采用PF算法和保障吞吐量的比例公平（TG-PF算法）,该算法充分利用了最大载干比（Max C/I）算法和比例公平（PF）算法的优势,能够有效地提升小区边缘的吞吐量,以满足中继蜂窝小区的系统吞吐量和调度公平性要求。仿真结果表明,所提方法能够以较低的调度公平性牺牲换取小区边缘吞吐量的较大提升。     

Transmission scheduling in a multi‐channel wireless network with bidirectional relaying links

Using network coding in a wireless network can potentially improve the network throughput. On the other hand, it increases the complexity of resource allocations as the quality of one transmission is affected by the link conditions of the transmitter to multiple receivers. In this work, we study time slot scheduling and channel allocations jointly for a network with bidirectional relaying links, where the two end nodes of each link can exchange data through a relay node. Two scenarios are considered when the relay node forwards packets to the end nodes. In the first scenario, the relay node always forwards network‐coded packets to both end nodes simultaneously; in the second scenario, the relay node opportunistically uses network coding for two‐way relaying and traditional one‐way relaying. For each scenario, an optimization problem is first formulated for maximizing the total network throughput. The optimum scheduling is not causal because it requires future information of channel conditions. We then propose heuristic scheduling schemes. The slot‐based scheduling maximizes the total transmission rate of all the nodes at each time slot, and the node‐based scheduling schedules transmissions based on achievable transmission rates of individual nodes at different channels. The node‐based one has lower complexity than the slot‐based one. Our results indicate that although the node‐based scheduling achieves slightly lower throughput than the slot‐based one, both the proposed scheduling schemes are very effective in the sense that the difference between their throughput and the optimum scheduling is relatively small in different network settings. Copyright © 2015 John Wiley & Sons, Ltd.     

A new analytical model for the CQ switch throughput calculation under the bursty traffic

In this paper we propose a new analytical iterative method for the throughput calculation of the Crosspoint Queued (CQ) switch with a random scheduling algorithm under the bursty traffic model. This method is verified by comparing it with the simulation results, which shows a very good match. To the authors’ knowledge, this is the first analytical method for the throughput calculation of such a switch for the bursty traffic model.     

Optimal scheduling of coordinated multipoint transmissions in cellular networks

In this paper, we study the optimal scheduling problem in coordinated multipoint (CoMP) transmission–based cellular networks. We consider joint transmission and coordinated scheduling together in CoMP transmission–based cellular networks and develop an optimization framework to compute the optimal max‐min throughput and the optimal scheduling of the transmissions to the users. The optimization problem is found to be a complex linear program with number of variables in for a cellular network of N users and K cells. We solve the optimization problem for several network instances using an optimization tool. The numerical results show that the optimal CoMP transmission provides a significant throughput gain over a traditional transmission. We find that in optimal scheduling the fraction time of coordinated scheduling is higher than that of joint transmission. To solve the optimization problem without any optimization tool, we propose a heuristic algorithm. The performance of the heuristic algorithm is evaluated and found to be provided throughput around 97% of the optimal throughput. Further, we extend the optimization framework to study joint scheduling and power allocation (JSPA) problem in CoMP transmission–based cellular networks. We numerically solve the JSPA problem for the network instances and demonstrate that the optimal power allocation at the base stations is not binary for a significant fraction of time of scheduling. However, the gain in max‐min throughput by the optimal JSPA technique over the optimal scheduling technique is not significant.     

一种基于SNR门限的上行虚拟MIMO配对算法

虚拟多输入多输出（VMIMO）系统由多个单天线的移动终端配成一组,占用相同的时频资源传输信息,关键技术之一是用户配对算法。基于传统的配对算法无法兼顾到配对用户间远近效应与系统吞吐量问题,提出了一种基于信噪比（SNR）门限融合调度的上行VMIMO配对算法。仿真结果表明,所提算法在保证低信噪比用户服务质量的基础上提高了系统吞吐量,同时可以降低对相邻小区的干扰,减小系统丢包率,更适合实际系统的应用。     

Improving DL-MU-MIMO performance in IEEE 802.11ac networks through decoupled scheduling

The IEEE 802.11ac standard introduces new downlink multi-user MIMO (DL-MU-MIMO) transmissions to up to four users in order to increase spatial reuse in wireless local area networks (WLANs). We argue that even better WLAN performance can be achieved by slightly modifying the DL-MU-MIMO scheduling. To this end we propose a new queuing mechanism based on the decoupling of EDCA and DL-MU-MIMO scheduling (DEMS) to avoid head-of-line blocking. We show that DEMS outperforms traditional 802.11ac scheduling based on first in, first out transmission queues. The improvement is shown in terms throughput achieved with: (a) more efficient channel usage, (b) increased probability of transmission of high priority traffic, and (c) decreased competition between frames destined to distinct users.

     

车联网中交通安全消息动态优先调度机制

车联网中两类交通安全消息共享有限控制信道带宽,在消息突发状态下无法保证事件触发消息的传播性能,导致预警失效.基于差异化的消息传播性能需求提出了一种动态优先级区分的调度机制,按事件优先级分别进行队列管理,赋予事件触发消息优先权,通过设置优先级调度阈值实现对事件触发消息的动态调度.当优先队列长度高于阈值时,其抢占调度时隙.当队列长度低于阈值一半,退出抢占过程,恢复非抢占优先调度方法.仿真显示,所提调度机制能够减小事件触发消息的端到端时延约1.3 ms,提高周期性消息的公平性约0.22.     

单跳波分复用网络中的优化数据传送策略

本文研究无源生形波分复用网络中数据传送的变化。在传统策略的基础上，本文提出了两各优化方案；最早发送时间数据传送策略和最小发送间隙数据传送策略，计算机模拟结果表明现任中优化部有力地改进了网络性能，既能显著地提高网络吞吐量，又极大地减小分组时延。     

The Effect of On-Off Scheduling to the Required Transmit Power in Systems with Fast Power Control

Physical layer channel-aware scheduling may significantly improve coverage and throughput of IP based services in wireless cellular networks, and the feasibility of such schedulers is actively studied within 3G and 4G systems. A channel-aware scheduler requires access to instantaneous channel state information in order to direct transmission to users with favorable channel conditions. In frequency division duplex (FDD) systems, this requires a fast feedback channel between mobile and base stations, and the overhead of the feedback control channel should be kept as low as possible.In this paper, we study the effect of control channel overhead to on-off scheduling (OOS) when fast transmit power control is applied in data and control channels. On-off scheduling is a simple channel-aware scheduling algorithm, where transmission to a user is suspended if the transmit power exceeds a given threshold. On-off scheduling is applied on the data channel while control channel is always on so that the scheduler is able to obtain channel state information from active users. The gain of OOS strongly depends on the power ratio between control and data channels, and increased interference due to control signaling and decreased interference due to channel-aware scheduling should be jointly considered in system design. Gains in the required transmit power are translated into gains in coverage and capacity assuming WCDMA parameters, and the results can be applied, e.g., when designing scheduling algorithms and corresponding signaling formats for WCDMA uplink.     

MU-MIMO系统下行链路中的自适应用户调度算法

在多用户MIMO系统下行链路中,经典的半正交用户调度算法(SUS)难以控制备选用户的门限参数值,且该算法没有考虑QOS对时延的要求。为此,提出一种自适应用户调度算法(AUS),在其调度过程中根据备选用户数及基站端天线数动态改变门限参数值,同时将用户最大时延限制作为用户选择准则的权重。仿真结果表明,与其他算法比,该算法提高了系统吞吐率,在加权用户选择准则时最大可减少24%的平均时延。     

Multi-user Fair Scheduling in the Downlink of CDMA Packet Systems

A fair scheduling algorithm is proposed to improve the system throughput while maintaining the fairness in the downlink of a code-division multiple access (CDMA) system employing AMC and multicodes. R. Kwan and C. Leung suggested an optimal scheduling to maximize the total throughput based on simultaneous transmissions strategy. In this letter, we extend the optimal scheduling so that some degree of fairness can be maintained. We formulate a mixed-integer nonlinear programming problem to assign the radio resources such as the transmit power and codes to several users effectively. The result shows that the proposed algorithm provides a significant throughput gain over PF scheduling with one-by-one transmission at the same level of fairness     

Effective resource scheduling scheme considering scheduling relevancy for downlink joint transmission system

Coordinated multi-point(CoMP) transmission is a promising technique to improve both cell average and cell edge throughput for long term evolution-advanced(LTE-A).For CoMP joint transmission(CoMP-JT) in heterogeneous scenario,if joint transmission(JT) users are firstly scheduled,other non-JT users will not be allocated sufficient resources,i.e.,scheduling relevancy exists in the users under different cells in the same coordination cluster.However,the CoMP system throughput will decline remarkably,if the impact of scheduling relevancy is not considered.To address this issue,this paper proposes a novel scheduling scheme for CoMP in heterogeneous scenario.The principles of the proposed scheme include two aspects.Firstly,this scheme gives priority to user fairness,based on an extended proportional fairness(PF) scheduling algorithm.Secondly,the throughput of the coordination cluster should be maintained at a high level.By taking the non-CoMP system as a baseline,the proposed scheme is evaluated by comparing to random PF(RPF) and orthogonal PF(OPF) scheme.System-level simulation results indicate that,the proposed scheme can achieve considerable performance gain in both cell average and cell edge throughput.     

The Maximum Throughput of A Wireless Multi-Hop Path

In this paper, the maximum end-to-end throughput that can be achieved on a wireless multi-hop path is investigated analytically. The problem is modeled using the conflict graph, where each link in the multi-hop path is represented uniquely by a vertex in the conflict graph and two vertices are adjacent if and only if the associated links mutually interfere. Using the conflict graph and the linear programming formulations of the problem, we analyzed the maximum end-to-end throughput of a wireless multi-hop path a) in a simple scenario where nodes are optimally placed and each node can only interfere with the transmission of its adjacent nodes along the path, and b) in a more complicated scenario where nodes are randomly placed and each node can interfere with the transmission of any number of nearby nodes along the path in both a) an error free radio environment and b) an erroneous radio environment. The maximum end-to-end throughputs for each of the above four scenarios are obtained analytically. We show that the maximum achievable end-to-end throughput is determined by the throughput of its bottleneck clique, where a clique is a maximal set of mutually adjacent vertices in the associated conflict graph. Further our analysis suggests the optimum scheduling algorithm that can be used to achieve the maximum end-to-end throughput and that it is convenient to use the (maximal) independent sets as the basic blocks for the design of scheduling algorithms. The findings in this paper lay guidelines for the design of optimum scheduling algorithms. They can be used to design computationally efficient algorithms to determine the maximum throughput of a wireless multi-hop path and to design a scheduling algorithm to achieve that throughput.     

Resource allocation based on cross-layer QoS-guaranteed scheduling for multi-service multi-user MIMO–OFDMA systems

Cross-layer strategies for resource allocation in wireless networks are essential to guaranty an efficient utilization of the scarce resource. In this paper, we present an efficient radio resource allocation scheme based on PHY/MAC cross layer design and QoS-guaranteed scheduling for multi-user (MU), multi-service (MS), multi-input multi-output (MIMO) concept, orthogonal frequency division multiple access (OFDMA) systems. It is about a downlink multimedia transmission chain in which the available resources as power and bandwidth, are dynamically allocated according to the system parameters. Among these parameters, we can mention the physical link elements such as channel state information, spectral efficiency and error code corrector rate, and MAC link variables, which correspond to the users QoS requirements and the queue status. Primarily, we use a jointly method which parametrizes these system parameters, according to the total power, and the bit error rate constraints. Secondly, we propose a QoS-guaranteed scheduling that shares the sub-carriers to the users. These users request several type of traffic under throughput threshold constraints. The main objective in this work is to adjust the average throughput per service of each user, according to their needs and likewise to satisfy a great number of connexions. Subsequently, we consider a model of moderated compartmentalization between various classes of services by partitioning the total bandwidth into several parts. Each class of service will occupy a part of the bandwidth and will be transmitted over a maximum number of sub-carriers. The simulation results show that the proposed strategy provides a more interesting performance improvement (in terms of average data rate and user satisfaction) than other existing resource allocation schemes, such as nonadaptive resource allocation strategy. The performances are also analyzed and compared for the two multi-service multi-user MIMO–OFDMA systems; with sub-carriers partitioning and without sub-carriers partitioning.