应用于航空Ad Hoc网络的高负载优先级均衡MAC协议

针对航空Ad Hoc网络在高负载下的低时延信道接入问题,提出一种优先级与公平性协作的多信道MAC协议(PBLL/HL)。在多信道检测统计基础上加以改进,结合优先级机制,在高负载网络中适时截流低优先级业务,优化网络流量,保证高优先级业务低时延发送;设计公平性优先级阈值与冲突退避窗口算法(PCA),减小低优先级业务接入时延。仿真结果表明,PBLL/HL能够在高负载网络有效控制信道接入,维持良好的网络流量,降低网络平均接入时延(低优先级业务时延过载时降低10%以上),稳定高负载网络吞吐量(最大吞吐量88.1%,过载时吞吐量下滑平缓),解决了航空数据链高业务量带来的高时延和网络拥塞。     

面向确定性网络的按需智能路由技术

确定性网络需要保证不同应用在时延、丢包率、抖动、吞吐量和可靠性等方面的确定性传输需求。针对应用的差异化、确定性的网络传输需求,提出了一种面向确定性网络的按需智能路由学习框架 OdR,在OdR框架下提出一种基于深度强化学习的按需智能路由算法OdR-TD3,OdR-TD3算法可以根据应用流量的确定性QoS需求生成路由策略,以满足确定性网络应用的需求。通过网络仿真实验评估,在确定性应用的QoS需求达成率上,OdR-TD3算法相较DV算法和SPF算法,具有显著的优势。     

移动流媒体并行多路传输机制研究

随着我国移动终端的多样化以及人们对网络需求的不断增长,我国移动网络数据的传输数量在近5年增长迅速。然而人们利用移动终端进行网络传输时,通常会受到网络带宽、网络拥塞、网络时延等因素的影响。传统的传输控制协议(Transmission Control Protocol, TCP)与用户数据报协议(User Datagram Protocol, UDP)使用单条路径进行网络传输,已不能很好地满足人们对高速率、实时播放、大吞吐量等网络传输的需求。为了解决这一问题,文章提出一种移动流媒体并行多路传输机制,即多路径传输协议(Multipath Transmission Control Protocol, MPTCP)。该协议可充分发挥多路径传输特性,一方面优化了网络传输的性能,另一方面提高了用户的体验感。     

无线网络中一种改进的TCP拥塞控制机制

由于无线网络中存在高误码、信号衰落、切换等原因，使传统TCP的应用受到了挑战。本文提出了一种新的无线网络拥塞控制方案—MRBR算法，它根据RTT值的变化对Reno协议进行修改，区分网络拥塞和无线链路差错，然后针对不同的原因，选取正确的参数实施拥塞控制。MRBR算法只需修改协议的发送部分，并且可以与Reno兼容。仿真结果表明，该方法增强了网络对拥塞以及随机差错的判断处理能力，有效提高了网络的吞吐量。     

基于802.11e的无线多跳自适应合作式QoS算法

 为解决Ad hoc网络中转发节点拥塞和低优先级业务增多而影响高优先级业务带宽的问题,提出了一种无线多跳网络服务质量保证框架WMHQ(Wireless Multiple Hop QoS)和自适应合作式信道接入算法QAC-EDCA(QoS guaranteed Adaptive Cooperation EDCA).算法将802.11e的优先级区分机制扩展成了三层优先级机制,通过将业务的服务质量需求映射成时隙利用率进行周期性的监测,并以控制帧捎带的方式在两跳范围内传播竞争窗口调整信息,使得高优先级业务具备剥夺低优先级业务带宽的能力和拥塞节点具有协调获取更多带宽的能力.仿真表明,该算法相对802.11e能更好地保护多跳情况下高优先级业务的服务质量.     

Ad hoc网络中基于多波束天线的集中式低时延调度算法

UxDMA算法是一种高效的集中式算法,是用于时分多址、频分多址和码分多址信道分配的统一算法。在UxDMA的基础上,利用多波束天线的多波束形成能力,针对低时延定向ad hoc网络提出了一种集中式调度算法——CLSM(Centralized Low-delay Scheduling Algorithm Based on Multi-beam Antennas)。CLSM通过不同时延等级限制的报文来比较着色后发送链路的优先级,优先选择高优先级链路传输。通过仿真验证了CLSM的性能：与UxDMA相比,该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时延性能。     

一种基于WSN时变性与节点剩余能量均衡的机会路由算法

 为了解决数据报文在无线传感网络中动态路由以及网络内各节点剩余能量均衡问题,该文提出了一种机会路由算法。首先,利用热力学第2定律描述数据报文在无线传感器网络中动态路由的传输过程,其中,为了表征网络内各节点状态的时变性以及剩余能量,提出了机会熵模型;其次,以机会熵模型作为选择下一跳节点的理论依据,并结合蚁群优化(ACO)算法,设计并实现了考虑网络中各节点时变性与剩余能量均衡的机会路由算法(ACO for Time Dependent Opportunistic-routing Protocol, ATDOP),使得数据报文在转发过程时,能够有效地选择下一跳节点,从而使网络内各节点的通信资源和能量资源达到负载均衡。最后,通过实验证明,相对于已有的机会路由协议,ATDOP具有报文成功传输率高、网络有效吞吐量大以及网络工作寿命长等优点。     

基于QoS付费业务的LTE下行跨层分组调度算法

准4G网络（LTE）即将商用会给人们带来更多的方便,以至于大量用户在日常生活中使用更多的QoS业务,这样系统会出现了拥塞和调度不够合理的情况,影响了高优先级业务的丢包率、时延和公平性。通过对LTE下行跨层分组调度各种算法的研究分析,从时延、丢包率、吞吐量和公平性等因素入手,在原有的比例公平性调度算法（PF）上进行改进,加入了补偿因子和付费权重值,使得改进型跨层调度算法,在吞吐量有一定提高的情况下,有效地降低了高优先级业务的丢包率和时延,并确保了高优先级业务的公平性。     

无线传感器网络中PECR协议的改进

PECR协议中对下游节点是否拥塞仅仅是一种预测,这种预测有时是不准确的,且在下游节点没有满足条件拥塞度和剩余能量的时候,传输层的问题要回到网络层去处理。为了解决PECR协议中存在的这些问题,文章引入了具有发送优先级的两个队列,优先发送优先级高的数据,在实际出现拥塞时会通知上游节点减少发送速率,并先抛弃掉优先级低的数据。在拥塞严重的时候也会抛弃掉优先级高的数据,但不会再回到网络层去处理问题。     

一种新的GEO/LEO双层星座路由算法

针对多层卫星星座网络的复杂通信环境和特殊应用背景,提出一种新的基于优先级的星上分布式路由算法( PDRA)。 PDRA算法采用新的分层管理策略,根据信息重要程度设置优先级,在拓扑快照起始时刻进行路由计算与更新,信息传输过程中采用拥塞回避策略。理论分析和仿真验证表明,PDRA算法与现有典型卫星星座网络路由算法相比性能优越,能够很好地利用GEO/LEO双层星座特点,有较低的数据丢包率和较高的吞吐量,可有效避免链路拥塞,并能保证重要信息实时可靠传输。     

数据中心网络中的MPTCP Incast（英文）

In recent years,dual-homed topologies have appeared in data centers in order to offer higher aggregate bandwidth by using multiple paths simultaneously.Multipath TCP(MPTCP) has been proposed as a replacement for TCP in those topologies as it can efficiently offer improved throughput and better fairness.However,we have found that MPTCP has a problem in terms of incast collapse where the receiver suffers a drastic goodput drop when it simultaneously requests data over multiple servers.In this paper,we investigate why the goodput collapses even if MPTCP is able to actively relieve hot spots.In order to address the problem,we propose an equally-weighted congestion control algorithm for MPTCP,namely EW-MPTCP,without need for centralized control,additional infrastructure and a hardware upgrade.In our scheme,in addition to the coupled congestion control performed on each subflow of an MPTCP connection,we allow each subflow to perform an additional congestion control operation by weighting the congestion window in reverse proportion to the number of servers.The goal is to mitigate incast collapse by allowing multiple MPTCP subflows to compete fairly with a single-TCP flow at the shared bottleneck.The simulation results show that our solution mitigates the incast problem and noticeably improves goodput in data centers.     

一种基于链路传输延迟的MPTCP拥塞控制算法*

由于传统TCP拥塞控制算法直接应用到MPTCP(Multipath Transport Control Protocol)中存在公平性问题,以及不能有效地发挥多路径传输的优势,因而从公平性方面对MPTCP现有拥塞控制算法进行研究.研究发现,现有的MPTCP拥塞控制算法均受到相同的回路时间限制.提出一种基于链路延迟的RTT补偿算法(Compensating for RTT mismatch,C-RTT ).该算法通过设置网络带宽占用比参数以及对MPTCP连接的子流设置侵略因子,从而保证瓶颈链路处MPTCP数据流和TCP数据流公平地共享可用带宽.最后通过NS3仿真实验证明,该算法能够有效地补偿链路中因RTT不等引起的公平性问题,并避免链路之间数据的非周期抖动,且保证了多路径传输的优越性.     

多源协作的传输控制机制

多路径传输控制协议（Multipath Transmission Control Protocol,MPTCP）是传输控制协议的一种扩展,实现端到端动态地利用多个地址建立多条传输路径,从而提高网络传输质量和可靠性.但是,MPTCP仍存在局限,能够解决端到端已确定的多路径调度问题,但难以实现不同端以及变化端间的路径协作.智慧协同网络是一种新型的未来网络体系,其核心思想是通过网络组件的智慧协作,最大限度优化利用网络资源,提高网络工作效率.本论文提出了基于智慧协同网络的多源协作传输控制机制,实现了传输控制协议从单源多路径向多源多路径的突破.具体来说,首先刻画了一种智慧协同网络的多源协作传输架构,引入子源协作传输方法,并详细介绍了多源协作机制的理论模型、报文格式以及子源协作管理的核心工作流程.通过仿真实验验证,多源协作传输控制机制能够将拥塞窗口平均利用率从51%提升至96%,并提高网络利用率和吞吐量.     

Multipath congestion control algorithm based on link capacity

Factors such as link differences and TCP friendliness constraints lead to the problem of unfair bandwidth allocation when the TCP congestion control mechanism was applied directly to multi-path transmission.To address the problem,it was proposed that a multipath congestion control algorithm was based on link capacity.The proposed algorithm which was based on the concept of feedback regulation achieved multipath joint congestion control by establishing the M/M/1 cache queue model to adjust the throughput rate of senders.Experimental results show the proposed algorithm can improve the multipath transmission bandwidth utilization and the multipath congestion control algorithm responsiveness,and ensure the fairness of multipath transmission.     

Joint Congestion Control Strategy During V2V Communication Among Authentic Vehicles in VANET

The wireless access in vehicular environment system is developed for enhancing the driving safety and comfort of automotive users. However, such system suffers from quality of service degradation for safety applications caused by the channel congestion in scenarios with high vehicle density. In the present work channel congestion is controlled jointly by road side unit, and vehicle. The present work supports vehicle to vehicle communication of authentic safe messages among authentic vehicles only. The road side unit reduces channel congestion by allowing only the authentic vehicles to participate in vehicle to vehicle communication, and by discarding unauthentic messages from the network. It revokes vehicles which are not authentic, and vehicles which are communicating unauthentic messages. Each vehicle also participates in the reduction of channel congestion by varying the size of beacon message dynamically, by removing the duplicate messages from message queue, and also by controlling the transmission power, and transmission range of a message during transmission. It further reduces the channel congestion by controlling the message generation rate using message generation rate control algorithm. Two different message generation rate control algorithm are proposed in the present work. In the first approach it maintains the channel load to an estimated initial value whereas the second approach increases the channel load till the percentage of message loss lies below a predefined threshold. The performance of the proposed scheme is studied on the basis of percentage of successful message reception, and percentage of message loss. The performance of the two message generation rate control algorithms are also compared in the present work.     

An implementation of Min–Max optimization for multipath SCTP through bandwidth estimation based resource pooling technique

Multipath transport protocols like Stream Control Transmission Protocol (SCTP) and Multipath TCP (MPTCP) have been introduced in the past as alternatives to traditional single path transport protocols like TCP and UDP. Various approaches to divide the flow on multiple paths have also been proposed in the literature. In this work, we show that the bandwidth estimation based resource pooling (BERP) congestion control algorithm is a practical implementation of the Min–Max optimization approach for flow division and verify this through ns-2 based simulations.     

A random-access algorithm for data networks carrying high-prioritytraffic

The authors consider data networks carrying mixed traffic, partially low and partially high priority. For such networks, they propose a synchronous limited sensing random access algorithm per channel, which gives a delay advantage to the high-priority traffic. The algorithm basically consists of two dynamically coupled window algorithms, one for the high and one for the low-priority packets. Assuming limit Poisson user models for both the traffic classes, the authors optimize the windows of the mixed algorithm for: (a) throughput maximization under no specific delay constraints, and (b) throughput maximization subject to expected delay constraints for the high-priority traffic. For cases (a) and (b), they study the delay characteristics of the algorithm, for the two classes of data traffic. With appropriate selection of the two window sizes, the algorithm can attain relatively high throughput, while it simultaneously maintains low expected per high-priority packet delays, whose values are only slightly affected by the total traffic rate     

信道公平分配的局部拥塞控制算法

提出基于信道公平分配的局部拥塞控制算法FCA(fair channel allocation),在缓解局部拥塞的同时增强信道分配的公平性。为减少获取邻居节点实时缓存信息的通信开销和提高以单一节点缓存是否溢出为检测模型的准确性,FCA采用以节点实时缓存长度预测为基础的邻居节点缓存总长度和分组平均传输延迟作为检测指标的拥塞检测模型。为避免使用独立拥塞通告消息增加信道负载,FCA采用在ACK控制帧中增加一个节点地址位携带拥塞信息。在去拥塞阶段,FCA采用基于实时缓存长度和队列优先权值的信道分配机制保证公平传输和防止部分节点因缓存增速过快导致溢出分组丢失。实验结果表明,FCA在碰撞次数、分组传递率、吞吐量和公平性等方面相比802.11、CODA和PCCP具有显著优势。     

Industrial IEEE 802.3 networks with short delivery time for urgentmessages

Two solutions are investigated for introducing priority mechanisms in the CSMA/CD (carrier-sense multiple access with collision detection) protocol defined in the IEEE 802.3 standard to provide short delivery times for urgent messages even when the overall traffic on the channel is heavy. Thus the CSMA/CD protocol, attractive because of its low cost, also becomes suitable for a class of industrial control applications. The proposed schemes can easily be implemented by using already-available chips and boards because they are based on the dynamic management of a transmission parameter, the slot time; this feature is already present in the standard IEEE 802.3, where it is set statically when the network is configured. The first configuration considered implements a message priority scheme, where the priority level for the station can be updated at each new message transmission, varying the slot time according to the message characteristics. The second configuration introduces a fixed-station-priority mechanism which allows each node in the network to be assigned to a specific priority class     

Queue‐based congestion detection and multistage rate control in event‐driven wireless sensor networks

Protocols for sensor networks have traditionally been designed using the best effort delivery model. However, there are many specific applications that need reliable transmissions. In event‐driven wireless sensor networks, the occurrence of an event may generate a large amount of data in a very short time. Among them, some critical urgent information needs to be transmitted reliably in a timely manner. In this scenario, congestion is inevitable because of the constraints in available resources. How to control the congestion is very important for the reliable transmission of urgent information. To address this problem, we propose a queue‐based congestion detection and a multistage rate control mechanism. In our proposed mechanism, not only the current queue length but also the queue fluctuation are adopted as indications of congestion. Each sensor node evaluates its congestion level locally and determines its congestion state with a state machine. We design a multistage rate adjustment mechanism for nodes to adjust their rates depending on their congestion states. We also distinguish high‐priority critical traffic from low‐priority non‐critical traffic. Extensive simulation results confirm the superior performance of our proposed protocol with respect to throughput, loss probability, and delay.Copyright © 2012 John Wiley & Sons, Ltd.