Implicit hop-by-hop congestion control in wireless multihop networks

It has been shown that TCP and TCP-like congestion control are highly problematic in wireless multihop networks. In this paper we present a novel hop-by-hop congestion control protocol that has been tailored to the specific properties of the shared medium. In the proposed scheme, backpressure towards the source node is established implicitly, by passively observing the medium. A lightweight error detection and correction mechanism guarantees a fast reaction to changing medium conditions and low overhead. Our approach is equally applicable to TCP- and UDP-like data streams. We demonstrate the performance of our approach by an in-depth simulation study. These findings are underlined by testbed results obtained using an implementation of our protocol on real hardware.     

Cross-layer congestion control in ad hoc wireless networks

The paper presents the problem of performance degradation of transport layer protocols due to congestion of wireless local area networks. Following the analysis of available solutions to this problem, a cross-layer congestion avoidance scheme (C³TCP) is presented, able to obtain higher performance by gathering capacity information such as bandwidth and delay at the link layer. The method requires the introduction of an additional module within the protocol stack of the mobile node, able to adjust the outgoing data stream based on capacity measurements. Moreover, a proposal to provide optional field support to existing IEEE 802.11 protocol, in order to support the presented congestion control solution as well as many other similar approaches, is presented. Achieved results underline good agreement with design considerations and high utilization of the available resources.     

无线多媒体网络中自适应拥塞控制算法的研究

提出了一种适用于采用无线接入多媒体流的拥塞控制算法,简称adaptive-MQWB(adaptivemediaQoSandwirelessbandwidth)。该算法依据当前带宽的动态变化率,在满足多媒体传输的最大时延的前提下,以最佳目标队长为实现目标,寻求最优的主动队列管理方案。仿真结果表明,与目前已有的MADR、tuned-RED算法相比,adaptive-MQWB算法在带宽动态变化的自适应性和多媒体传输时延的QoS保证方面都表现出更好的性能优势。     

Error and congestion control for wireless sensor networks

In the wireless sensors network (WSN) field, a wide variety of sensors produce a heterogeneous traffic mix, targeting diverse applications with different reliability requirements. We focus on emergency response scenarios, where a mobile rescuer moves through a, possibly disconnected, network, trying to talk to diverse sensors. We assume two types of sensors, event sensors triggered by an event and periodic sensors activated at predefined time intervals, as well as two types of transmission, either using the highest bit rate available or using predefined bit rates. Our reliable transport protocol for sensor networks with mobile sinks (RT‐SENMOS) takes into account all these parameters and tries to provide the best possible user experience under the current circumstances of the network, using a sink‐driven approach where an application‐specific sink is combined with generic sensors. RT‐SENMOS was implemented and tested over a real network with emulated losses and compared against rate‐controlled reliable transport (RCRT), a well‐known sink‐driven protocol. The results show that RT‐SENMOS fully exploits the available bandwidth in all cases, while RCRT only manages to exploit 60% to 90% of it. Furthermore, RT‐SENMOS adapts much faster to prevailing network conditions, while its protocol overhead, in terms of control messages exchanged, is much lower than that of RCRT.     

传感器网络中基于事件信息量的公平性控制

在分析无线传感器网络现有公平性控制方法的基础上,依照新的公平性控制的基本原则实施带宽分配,即事件信息量是节点传输的有效信息量,公平性带宽分配是按事件信息量的比例来分配,如何计算带宽竞争节点所传的事件信息量是实现该基本原则的关键.针对事件信息均匀分布的情况,提出了以事件信息量为基础的公平性控制(EFFRC,event faith based fair rate control)算法,该算法将事件信息量的计算转换为事件区域大小的计算,并通过区域细分,将任意形状的事件区域大小的计算转换为若干四边形区域大小的求和,从而达到信息量计算的目的.实验表明,EFFRC算法能够有效计算事件信息量,实现公平的带宽分配.     

Novel congestion control approach in wireless multimedia sensor networks

Data generated in wireless multimedia sensor networks (WMSNs) may have different importance and it has been claimed that the network exert more efforts in servicing applications carrying more important information. Nevertheless, importance of packets cannot generally be accurately represented by a static priority value. This article presents a dynamic priority based congestion control (DPCC) approach that makes two major innovations in WMSNs. First, DPCC employs dynamic priority to represent packet importance. Second, it prioritizes the local traffic of motes near the base station when WMSN is highly congested. Simulation results confirm the superior performance of the proposed approach with respect to energy efficiency, loss probability and latency as well.     

Optimizing routing based on congestion control for wireless sensor networks

Along with the increasing demands for the applications running on the wireless sensor network (WSN), energy consumption and congestion become two main problems to be resolved urgently. However, in most scenes, these two problems aren’t considered simultaneously. To address this issue, in this paper a solution that sufficiently maintains energy efficiency and congestion control for energy-harvesting WSNs is presented. We first construct a queuing network model to detect the congestion degree of nodes. Then with the help of the principle of flow rate in hydraulics, an optimizing routing algorithm based on congestion control (CCOR) is proposed. The CCOR algorithm is designed by constructing two functions named link gradient and traffic radius based on node locations and service rate of packets. Finally, the route selection probabilities for each path are allocated according to the link flow rates. The simulation results show that the proposed solution significantly decreases the packet loss rate and maintains high energy efficiency under different traffic load.     

Network planning in wireless ad hoc networks: a cross-Layer approach

In this paper, the network planning problem in wireless ad hoc networks is formulated as the problem of allocating physical and medium access layer resources or supplies to minimize a cost function, while fulfilling certain end-to-end communication demands, which are given as a collection of multicast sessions with desired transmission rates. We propose an iterative cross-layer optimization, which alternates between: 1) jointly optimizing the timesharing in the medium access layer and the sum of max of flows assignment in the network layer and 2) updating the operational states in the physical layer. We consider two objectives, minimizing aggregate congestion and minimizing power consumption, respectively, corresponding to operating in a bandwidth-limited regime and in an energy-limited regime. The end result is a set of achievable tradeoffs between throughput and energy efficiency, in a given wireless network with a given traffic pattern. We evaluate our approach quantitatively by simulations of community wireless networks and compare with designs that decouple the layers. We demonstrate that significant performance advantages can be achieved by adopting a full-fledged cross-layer optimization. Furthermore, we observe that optimized solutions generally profit from network coding, physical-layer broadcasting, and traffic-dependent physical states.     

A cross-Layer quality-of-service mapping architecture for video delivery in wireless networks

Providing quality-of-service (QoS) to video delivery in wireless networks has attracted intensive research over the years. A fundamental problem in this area is how to map QoS criterion at different layers and optimize QoS across the layers. In this paper, we investigate this problem and present a cross-layer mapping architecture for video transmission in wireless networks. There are several important building blocks in this architecture, among others, QoS interaction between video coding and transmission modules, QoS mapping mechanism, video quality adaptation, and source rate constraint derivation. We describe the design and algorithms for each building block, which either builds upon or extend the state-of-the-art algorithms that were developed without much considerations of other layers. Finally, we use simulation results to demonstrate the performance of the proposed architecture for progressive fine granularity scalability video transmission over time-varying and nonstationary wireless channel.     

Upstream congestion control in wireless sensor networks through cross-layer optimization

Congestion in wireless sensor networks not only causes packet loss, but also leads to excessive energy consumption. Therefore congestion in WSNs needs to be controlled in order to prolong system lifetime. In addition, this is also necessary to improve fairness and provide better quality of service (QoS), which is required by multimedia applications in wireless multimedia sensor networks. In this paper, we propose a novel upstream congestion control protocol for WSNs, called priority-based congestion control protocol (PCCP). Unlike existing work, PCCP innovatively measures congestion degree as the ratio of packet inter-arrival time along over packet service time. PCCP still introduced node priority index to reflect the importance of each sensor node. Based on the introduced congestion degree and node priority index, PCCP utilizes a cross-layer optimization and imposes a hop-by-hop approach to control congestion. We have demonstrated that PCCP achieves efficient congestion control and flexible weighted fairness for both single-path and multi-path routing, as a result this leads to higher energy efficiency and better QoS in terms of both packet loss rate and delay.     

基于专家控制的无线网络拥塞控制机制的研究

由于无线网络中存在高误码、信号衰落、切换等原因，使得传统TCP的应用受到了挑战。本文提出了将专家控制用于无线网络的拥塞控制方案，它通过推理判断，确定当前的TCP连接状况，进而区分网络拥塞和无线链路差错，然后再针对不同的原因，选取正确的控制策略实施拥塞控制。仿真结果表明，该方法增强了网络对拥塞以及随机差错的实时处理能力，提高了网络的吞吐量，算法本身具有较强的顽健性。     

TCP CERL: congestion control enhancement over wireless networks

In this paper, we propose and verify a modified version of TCP Reno that we call TCP Congestion Control Enhancement for Random Loss (CERL). We compare the performance of TCP CERL, using simulations conducted in ns-2, to the following other TCP variants: TCP Reno, TCP NewReno, TCP Vegas, TCP WestwoodNR and TCP Veno. TCP CERL is a sender-side modification of TCP Reno. It improves the performance of TCP in wireless networks subject to random losses. It utilizes the RTT measurements made throughout the duration of the connection to estimate the queue length of the link, and then estimates the congestion status. By distinguishing random losses from congestion losses based on a dynamically set threshold value, TCP CERL successfully attacks the well-known performance degradation issue of TCP over channels subject to random losses. Unlike other TCP variants, TCP CERL doesn’t reduce the congestion window and slow start threshold when random loss is detected. It is very simple to implement, yet provides a significant throughput gain over the other TCP variants mentioned above. In single connection tests, TCP CERL achieved an 175, 153, 85, 64 and 88% throughput gain over TCP Reno, TCP NewReno, TCP Vegas, TCP WestwoodNR and TCP Veno, respectively. In tests with multiple coexisting connections, TCP CERL achieved an 211, 226, 123, 70 and 199% throughput improvement over TCP Reno, TCP NewReno, TCP Vegas, TCP WestwoodNR and TCP Veno, respectively.     

Distributed multichannel assignment with congestion control in wireless mesh networks

In Multichannel Wireless Mesh Network architecture, topology discovery, traffic profiling, channel assignment and routing are essential. From the existing work done so far, we can observe that no work has been carried out on the combined solution of multichannel assignment with routing protocol and congestion control. In this paper, we propose to design a Distributed Multichannel Assignment with Congestion control (DMAC) routing protocol. In this protocol, a traffic‐aware metric provides the solution for multichannel assignment and congestion control. Hence, the proposed protocol can improve the throughput and channel utilization to a very high extent. The proposed algorithm avoids self‐interference by not assigning a channel to any link whose incident links have already been assigned channels. By our simulation results, we show that our proposed protocol attains high throughput and delivery ratio along with reduced delay. Copyright © 2011 John Wiley & Sons, Ltd.     

A reliable congestion control mechanism for geocasting in mobile wireless networks

In this paper, we present a reliable congestion control mechanism for geocasting in mobile wireless networks. Our protocol can be used as an extension to conventional multicasting protocols in order to overcome the problems associated with terminal mobility and the wireless environment. We present the architecture and implementation of the Multicast ACK Aggregation Method (MAAM). And test the performance of MAAM in various scenarios. Our simulation results show the efficiency and reliability of MAAM in wireless networks with high bit error rates. We further enhance the performance of MAAM by designing MAAM with local recovery (MAAM/LR). Copyright © 2003 John Wiley & Sons, Ltd.     

A QoS-aware congestion control mechanism for wireless multimedia sensor networks

Wireless Networks - The amount of data produced by multimedia sensor nodes (such as video/audio sensors), is considerably huge comparing with the data of scalar sensor nodes. The great numbers of...     

Distributed cross-layer coordination of congestion control and resource allocation in S-TDMA wireless networks

We consider the problem of joint congestion control and resource allocation in spatial-TDMA wireless networks. The design problem is posed as a utility maximization problem subject to link rate constraints which involve both transmission scheduling and power allocation. Starting from the performance limitations of a centralized optimization based on global network information, we proceed systematically in our development of two distributed and transparent protocols that rely on local information only. In the process, we introduce a novel decomposition method for convex optimization, establish its convergence for the utility maximization problem, and demonstrate how it suggests a distributed solution based on TCP/AQM and incremental updates of the transmission schedule. We develop a two-step procedure for finding the schedule updates and suggest two schemes for distributed link scheduling and power control under realistic interference models. Although the final protocols are suboptimal, we isolate and quantify the performance losses incurred by each simplification and demonstrate strong performance in examples.

Transmission power control and scheduling algorithm in wireless body area networks

Wireless body area networks(WBAN)were expecting to play an essential role for healthcare,sports,leisure,and all the aspect of our daily life.The purpose was to solve two key issues of WBAN.The first issue was which sensor should transmit during each time slot in order to maximize the lifetime as well as maintaining fairness performance.The second issue was which transmit power level should be chosen for the purpose of energy saving without degrading reliability.For the first problem,a distributed scheduling algorithm was proposed to balance lifetime and fairness for WBAN.For the second issue,a modified transmission power control algorithm was presented to adjust transmit power adaptively.Simulation results are presented to demonstrated efficacy of the proposed algorithm.     

Towards combining admission control and link scheduling in wireless mesh networks

Wireless mesh networks (WMNs) have emerged recently as a key solution for next-generation wireless networks; they are low cost and easily deployed technology. However, WMNs have to deal with a low bandwidth which prevents them from guaranteeing the requirements of applications with strict constraints. To overcome this limitation, we propose in this paper a new admission control model which integrates a dynamic link scheduling scheme, named ACLS, in order to optimize the network bandwidth use. We formulate the admission control problem as a binary linear programming problem (BL2P). The proposed admission control integrates an algorithm, based on the Dakin’s branch and bound (B&B) method, which respects the bandwidth and delay required by the flows. The proposed ACLS solution has been validated on ns2, and the simulation results showed that ACLS model has better performance than the reference solution BRAWN; it accepts more flows while guaranteeing their delay and bandwidth.     

Joint scheduling and power control for wireless ad hoc networks

In this paper, we introduce a cross-layer design framework to the multiple access problem in contention-based wireless ad hoc networks. The motivation for this study is twofold, limiting multiuser interference to increase single-hop throughput and reducing power consumption to prolong battery life. We focus on next neighbor transmissions where nodes are required to send information packets to their respective receivers subject to a constraint on the signal-to-interference-and-noise ratio. The multiple access problem is solved via two alternating phases, namely scheduling and power control. The scheduling algorithm is essential to coordinate the transmissions of independent users in order to eliminate strong levels of interference (e.g., self-interference) that cannot be overcome by power control. On the other hand, power control is executed in a distributed fashion to determine the admissible power vector, if one exists, that can be used by the scheduled users to satisfy their single-hop transmission requirements. This is done for two types of networks, namely time-division multiple-access (TDMA) and TDMA/code-division multiple-access wireless ad hoc networks.     

QoS-driven adaptive congestion control for voice over IP in multiservice wireless cellular networks

This work establishes a QoS-driven adaptive congestion control framework that provides QoS guarantees to VoIP service flows in mixed traffic scenarios for wireless cellular networks. The framework is composed of three radio resource management algorithms: admission control, packet scheduling, and load control. The proposed framework is scalable to several services and can be applied in any current or future packet-switched wireless system. By means of dynamic system-level simulations carried out in a specific case study where VoIP and Web service flows compete for shared access in an HSDPA wireless network, the proposed framework is able to increase the overall system capacity twofold depending on the traffic mix, while keeping the system operating optimally in its target QoS profile.