Removing redundant TCP functionalities in wired‐cum‐wireless networks with IEEE 802.11e HCCA support

The TCP was originally designed for wired networks, assuming transmission errors were negligible. Actually, any acknowledgment time‐out unconditionally triggers the congestion control mechanism, even in wireless networks in which this assumption is not valid. Consequently, in wireless networks, TCP performance significantly degrades. To avoid this degradation, this paper proposes the so‐called split TCP and UDP. In this approach, the access point splits the TCP connection and uses a customized and lighter transport protocol for the wireless segment. It takes advantage of the IEEE 802.11e Hybrid Coordination Function Controlled Channel Access (HCCA) mechanisms to remove redundant TCP functionalities. Specifically, the HCCA scheduler allows disabling of the congestion control in the wireless link. Similarly, the IEEE 802.11e error control service makes possible to eliminate TCP acknowledgments, therefore reducing the TCP protocol overhead. Finally, the usage of an HCCA scheduler permits providing fairness among the different data flows. The proposed split scheme is evaluated via extensive simulations. Results show that split TCP and User Datagram Protocol outperforms the analyzed TCP flavors—specifically designed for wireless environments—and the split TCP solution, achieving up to 95% of end‐user throughput gain. Furthermore, the proposed solution is TCP friendly because TCP flows are not degraded by the presence of flows by using this approach. Copyright © 2013 John Wiley & Sons, Ltd.     

Congestion control with dynamic threshold adaptation and cross‐layer response for TCP Vegas over IEEE 802.11 wireless networks

Wireless technologies provide mobile access and enable rapid andcost‐effective network deployment. But a wireless link is generally accompanied by high interference, transmission errors and a varying latency. The erratic packet losses usually lead to a curbing of the flow of segments on the TCP connection, and thus limit TCP performance. This paper presents a threshold control mechanism with cross‐layer response approach for improving TCP Vegas performance in IEEE 802.11 wireless networks. By making slight modifications to the legacy IEEE 802.11 MAC and TCP, the numerical results reveal that the proposed scheme provides a significant improvement in TCP performance under IEEE 802.11 wireless environments. Copyright © 2013 John Wiley & Sons, Ltd.     

Relative loss rate differentiation: performance of short‐lived TCP flows

The relative differentiated service model provides assurances for the relative quality ordering between service classes, rather than for the actual service level in each class. In this paper, we describe a relative loss rate differentiation scheme where packet drop probabilities are determined according to an active queue management (AQM) mechanism based on random early detection (RED) in a first‐in first‐out (FIFO) queue, are weighted in inverse proportion to the price that the network operator assigns to each service class. Basically, we describe a scheme where relative loss rate differentiation is incorporated directly into AQM. Most TCP flows today, particularly Web flows, can be characterized as short‐lived flows. Using simulations with short‐lived TCP flows, we show that the scheme is very effective in ensuring relative loss rate differentiation between service classes during times of network congestion. Copyright © 2004 John Wiley & Sons, Ltd.     

Empirical evaluation of receiver‐based TCP delay control in CDMA2000 networks

Wide‐area broadband wireless technologies such as CDMA2000 often suffer from variable transfer rate and long latency. In particular, TCP window‐based rate control causes excessive buffering at the base station because of the lower transfer rate of the wireless link than that of the wired backhaul link. This performance characteristic of TCP further increases the end‐to‐end delay, and additional resources are required at the base station. This paper presents a practical mechanism to control the end‐to‐end TCP delay for CDMA2000 networks (or other similar wireless technologies). The key idea is to reduce and stabilize RTT (round‐trip time) by dynamically controlling the TCP advertised window size, based on a runtime measurement of the wireless channel condition at the mobile station. The proposed system has been implemented by modifying the Linux protocol stack. The experiment results, conducted on a commercial CDMA2000 1x network, show that the proposed scheme greatly reduces the TCP delay in non‐congested networks, while not sacrificing the TCP throughput in congested networks. Copyright © 2006 John Wiley & Sons, Ltd.     

A study on a receiver‐based management scheme of access link resources for QoS‐controllable TCP connections

Although the bandwidth of access networks is rapidly increasing with the latest techniques such as DSL and FTTH, the access link bandwidth remains a bottleneck, especially when users activate multiple network applications simultaneously. Furthermore, since the throughput of a standard TCP connection is dependent on various network parameters, including round‐trip time and packet loss ratio, the access link bandwidth is not shared among the network applications according to the user's demands. In this thesis, we present a new management scheme of access link resources for effective utilization of the access link bandwidth and control of the TCP connection's throughput. Our proposed scheme adjusts the total amount of the receive socket buffer assigned to TCP connections to avoid congestion at the access network, and assigns it to each TCP connection according to characteristics in consideration of QoS. The control objectives of our scheme are (1) to protect short‐lived TCP connections from the bandwidth occupation by long‐lived TCP connections, and (2) to differentiate the throughput of the long‐lived TCP connections according to the upper‐layer application's demands. One of the results obtained from the simulation experiments is that our proposed scheme can reduce the delay of short‐lived document transfer perceived by the receiver host by up to about 90%, while a high utilization of access link bandwidth is maintained. Copyright © 2006 John Wiley & Sons, Ltd.     

Corruption‐aware adaptive increase and adaptive decrease algorithm for TCP error and congestion controls in wireless networks

The conventional TCP tends to suffer from performance degradation due to packet corruptions in the wireless lossy channels, since any corruption event is regarded as an indication of network congestion. This paper proposes a TCP error and congestion control scheme using corruption‐aware adaptive increase and adaptive decrease algorithm to improve TCP performance over wireless networks. In the proposed scheme, the available network bandwidth is estimated based on the amount of the received integral data as well as the received corrupted data. The slow start threshold is updated only when a lost but not corrupted segment is detected by sender, since the corrupted packets still arrive at the TCP receiver. In the proposed scheme, the duplicated ACKs are processed differently by sender depending on whether there are any lost but not corrupted segments at present. Simulation results show that the proposed scheme could significantly improve TCP throughput over the heterogeneous wired and wireless networks with a high bit error rate, compared with the existing TCP and its variants. Copyright © 2008 John Wiley & Sons, Ltd.     

Cross‐layer error recovery in wireless access networks: The ARQ proxy approach

Wireless networks are being increasingly employed to provide mobile access to network services. In most existing standards, reliable transmission on the wireless medium is achieved through the introduction of ARQ schemes at MAC layer, a strategy which is also employed by TCP for reliable end‐to‐end data delivery. The paper proposes an approach to overcome the performance degradation deriving from the duplicate ARQ strategies implemented at the transport and MAC layers by introducing a cross‐layer solution to reduce un‐necessary transmissions on the wireless medium. Furthermore, the paper describes how the proposed scheme, called ARQ Proxy, can be deployed in three different wireless technologies (3G Long‐Term Evolution, Wi‐Fi, and WiMAX) and provides extensive validation of the achievable improvement through simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

Delayed duplicate acknowledgements: a TCP‐Unaware approach to improve performance of TCP over wireless

Since a TCP sender cannot distinguish between packet losses arising from transmission errors from those due to congestion, TCP tends to perform poorly on wireless links that are prone to transmission errors. Several techniques have previously been proposed to improve TCP performance over wireless links. Existing schemes typically require an intermediate node (typically, a base station) to be TCP‐aware. For instance, the Snoop scheme requires the base station to interpret TCP headers and take appropriate action to help improve TCP performance. This paper proposes an alternative TCP‐unaware technique that attempts to mimic the behavior of the Snoop protocol. Performance evaluation shows that the proposed Delayed Dupacks scheme performs quite well. Copyright © 2001 John Wiley & Sons, Ltd.     

TCP with delayed ack for wireless networks

This paper studies the TCP performance with delayed ack in wireless networks (including ad hoc and WLANs) which use IEEE 802.11 MAC protocol as the underlying medium access control. Our analysis and simulations show that TCP throughput does not always benefit from an unrestricted delay policy. In fact, for a given topology and flow pattern, there exists an optimal delay window size at the receiver that produces best TCP throughput. If the window is set too small, the receiver generates too many acks and causes channel contention; on the other hand, if the window is set too high, the bursty transmission at the sender triggered by large cumulative acks will induce interference and packet losses, thus degrading the throughout. In wireless networks, packet losses are also related to the length of TCP path; when traveling through a longer path, a packet is more likely to suffer interference. Therefore, path length is an important factor to consider when choosing appropriate delay window sizes. In this paper, we first propose an adaptive delayed ack mechanism which is suitable for ad hoc networks, then we propose a more general adaptive delayed ack scheme for ad hoc and hybrid networks. The simulation results show that our schemes can effectively improve TCP throughput by up to 25% in static networks, and provide more significant gain in mobile networks. The proposed schemes are simple and easy to deploy. The real testbed experiments are also presented to verify our approaches. Furthermore, a simple and effective receiver-side probe and detection is proposed to improve friendliness between the standard TCP and our proposed TCP with adaptive delayed ack.     

An end‐to‐end alternative to TCP PEPs: Initial Spreading,a TCP fast start‐up mechanism

While Transmission Control Protocol (TCP) Performance Enhancing Proxy (PEP) solutions have long been undisputed to solve the inherent satellite problems, the improvement of the regular end‐to‐end TCP congestion avoidance algorithms and the recent emphasis on the PEPs drawbacks have opened the question of the PEPs sustainability. Nevertheless, with a vast majority of Internet connections shorter than ten segments, TCP PEPs continue to be required to counter the poor efficiency of the end‐to‐end TCP start‐up mechanisms. To reduce the PEPs dependency, designing a new fast start‐up TCP mechanism is therefore a major concern. But, while enlarging the Initial Window (IW) up to ten segments is, without any doubt, the fastest solution to deal with a short‐lived connection in an uncongested network, numerous researchers are concerned about the impact of the large initial burst on an already congested network. Based on traffic observations and real experiments, Initial Spreading has been designed to remove those concerns whatever the load and type of networks. It offers performance similar to a large IW in uncongested network and outperforms existing end‐to‐end solutions in congested networks. In this paper, we show that Initial Spreading, taking care of the satellite specificities, is an efficient end‐to‐end alternative to the TCP PEPs. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance analysis of the IEEE 802.11e wireless networks with TCP ACK prioritization

With the advent of multimedia over wireless local area networks, the IEEE 802.11e standard was proposed to incorporate Quality of Service (QoS). It has been found that the throughput of Transmission Control Protocol (TCP) is less than that of User Datagram Protocol (UDP) in the IEEE 802.11e. This is because the TCP acknowledgment packets are queued up at the access points. In this paper, two types of TCP acknowledgment prioritizing schemes are proposed. The proposed schemes improve the overall throughput of TCP while maintaining the QoS requirements. We also analyze the problem of starvation of lower priority traffic and its effects on the performance of lower priority TCP traffic. The proposed dynamic scheme of TCP acknowledgment prioritization aims at improving the throughput of the lower priority TCP traffic under heavy network load while maintaining the QoS requirements of the higher priority traffic. The schemes have been verified through extensive simulation.     

Performance evaluation of TCP algorithms in multi‐hop wireless packet networks

Wireless packet ad hoc networks are characterized by multi‐hop wireless connectivity and limited bandwidth competed among neighboring nodes. In this paper, we investigate and evaluate the performance of several prevalent TCP algorithms in this kind of network over the wireless LAN standard IEEE 802.11 MAC layer. After extensively comparing the existing TCP versions (including Tahoe, Reno, New Reno, Sack and Vegas) in simulations, we show that, in most cases, the Vegas version works best. We reveal the reason why other TCP versions perform worse than Vegas and show a method to avoid this by tuning a TCP parameter— maximum window size. Furthermore, we investigate the performance of these TCP algorithms when they run with the delayed acknowledgment (DA) option defined in IETF RFC 1122, which allows the TCP receiver to transmit an ACK for every two incoming packets. We show that the TCP connection can gain 15 to 32 per cent good‐put improvement by using the DA option. For all the TCP versions investigated in this work, the simulation results show that with the maximum window size set at approximately 4, TCP connections perform best and then all these TCP variants differ little in performance. Copyright © 2001 John Wiley & Sons, Ltd.     

A cross‐layer TCP for providing fairness in wireless mesh networks

The fair allocation of resources among different nodes is one of the critical problems in wireless mesh networks. Existing solutions mainly focus on rate‐limitation policies or distributed fair MAC schemes at the potential expense of total network utilization. This paper investigates a special starvation problem among TCP flows that are different hops away from the BS, as well as its recently proposed solution, the ‘Minimum Content Window’ policy based on IEEE 802.11e. It is found that the aggregate throughput degrades sharply because the effect of this policy on the TCP congestion mechanism has been overlooked. This paper proposes a priority‐based congestion control by using ‘Cross‐Layer Explicit Congestion Notification’. Analysis and simulation results demonstrate that our scheme can improve the fairness of TCP flows while the aggregate throughput is at least 20% higher than the ‘Minimum Content Window’ policy. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance evaluation of TCP under dynamic allocation scheme for down‐link transmission rate in W‐CDMA systems

IMT‐2000 has attracted much attention as the Next Generation Mobile Communication System. IMT‐2000 can provide high‐bit‐rate data communication service, so that a great number of packets conveyed by TCP (transmission control protocol) can be transmitted over a wireless link. W‐CDMA, standardized in 3GPP (which standardizes IMT‐2000), allows dynamically allocating transmission rates to flow over a wireless link in response to a changing FER for each flow, which is thought to be essential for a next generation mobile communication system. Therefore, in this paper, we study the characteristics of the dynamic allocation scheme when TCP flows share a wireless link, and, in particular, we focus on the throughput performance of these TCP flows. First, we use simulations to examine the effectiveness of the dynamically allocating down‐link transmission rate for TCP flows in response to changing the frame error rate (FER). Through the simulation results, we will show how it can improve the total throughput performance of TCP flows. Furthermore, we can obtain an effective way to allocate transmission rates to flows with different FERs in order to achieve high total throughput. Finally, we will deal with a case of multiple flows from a fixed host to a mobile host. In actual networks, this often happens. In this case, we will show that the total throughput of TCP flows degrades less than in the single‐flow case, even when the FER is high. Copyright © 2004 John Wiley & Sons, Ltd.     

An energy‐aware transmission mechanism for WiFi‐based mobile devices handling upload TCP traffic

This paper presents an energy‐aware transmission mechanism that improves the throughput and reduces the energy consumption of mobile devices in wired‐cum‐wireless TCP networks. The proposed mechanism places an agent at the base station, which identifies the cause of packet losses in the underlying network. When the mobile device acts as a TCP source, it adjusts the size of the congestion window adaptively according to the cause of packet losses with the aids of the agent in order to improve the transmission performance. In addition, the proposed mechanism lets the communication device to stay in sleep mode after completing the transmission in order to reduce the energy consumption. As a result, the cooperation between the mobile device and the agent improves the transmission performance as well as the energy efficiency greatly. To evaluate the performance of the proposed mechanism, we analyzed the effect of TCP on the communication device for mobile devices and present a power model. With extensive simulations based on the power model, we demonstrate that the proposed mechanism significantly improves the transmission performance, and reduces the energy consumption over a wide range of both wired and wireless packet losses. Copyright © 2008 John Wiley & Sons, Ltd.     

一种改善TCP性能的cdma2000链路层RLP重传方案

在无线数据传输网络中,物理层帧差错率(FER)是影响网络性能的一个主要因素。无线链路层重传技术是改善网络性能因无线信道误码率较高而下降的一项重要措施。本文主要研究cdma2000无线网络中链路层重传技术对无线TCP数据传输的影响,提出一种cdma2000链路层重传方案,并通过OPNET仿真技术对该重传方案进行仿真,验证了该方案能改善TCP数据在cdma2000无线网络中的传输性能。     

A fragment‐based retransmission scheme with quality‐of‐service considerations for wireless networks

In order to satisfy quality‐of‐service requirements for real‐time multimedia applications over wireless networks, IEEE 802.11e has been proposed to enhance wireless‐access functionalities. In IEEE 802.11e, collisions occur frequently as the system load becomes heavy, and then, the latency for successfully transmitting data is lengthened seriously because of contention, handshaking, and backoff overheads for collision avoidance. In this paper, we propose a fragment‐based retransmission (FBR) scheme with quality‐of‐service considerations for IEEE 802.11e‐based wireless local area networks. Our FBR can be used in all proposed fragmentation‐based schemes and greatly decrease redundant transmission overheads. By utilizing FBR, the retransmission delay will be significantly improved to conform strict time requirements for real‐time multimedia applications. We develop an analytical model and a simulation model to investigate the performance of FBR. The capability of the proposed scheme is evaluated by a series of simulations, for which we have encouraging results. Copyright © 2011 John Wiley & Sons, Ltd.     

QoS aware transmission control scheme for multihop WiMAX network

The IEEE 802.16j Mobile Multihop Relay (MMR) WiMAX network allows the number of hops between the end user and the base station to be more than two hops. It supports non‐real‐time Polling Service, which considers the minimum reserved rate and the maximum sustained rate as a QoS requirements. The reliability of sending the data over MMR WiMAX is achieved by using Transmission Control Protocol (TCP) in transport layer and automatic repeat request in the link layer. However, the use of automatic repeat request in the link layer makes the round trip time fluctuate rapidly, which increases the possibility of retransmission timeout (RTO) expiration. TCP performance degrades because of frequent timeout, and hence the QoS transmission rates cannot be satisfied. Therefore, this paper presents an RTO smoothing scheme and QoS aware transmission control to enhance the performance of data transmission over MMR WiMAX networks. The RTO smoothing scheme aims to reduce the frequent timeout occurrences. The slow start threshold and maximum congestion window are adjusted to satisfy the required QoS and it provides transmission rate fairness for the users at different hops. The results showed that, the proposed schemes reduce the timeout, and improve the utilization of the allocated resources and TCP throughput. Copyright © 2012 John Wiley & Sons, Ltd.     

EVA: a better TCP version for resource‐insufficient networks

TCP Vegas exhibits unfair congestion avoidance mechanism, which aggravates when there are insufficient network resources to accommodate buffer space of a pipe (bandwidth delay product). To remedy this shortcoming, we propose an Enhanced VegAs (EVA) that employs three auxiliary mechanisms: Δ revision, congestion detection and congestion tendency detection. A 2^k factorial design with replications is used to study the effect of the three mechanisms. Our results show that TCP EVA achieves better performance than Vegas under various network conditions. Furthermore, congestion avoidance schemes, such as TCP EVA, perform much better than congestion control schemes, such as TCP Reno, in resource‐insufficient networks. Copyright © 2002 John Wiley & Sons, Ltd.     

Syndrome: a light‐weight approach to improving TCP performance in mobile wireless networks

It is well known that the performance of TCP deteriorates in a mobile wireless environment. This is due to the fact that although the majority of packet losses are results of transmission errors over the wireless links, TCP senders still take packet loss as an indication of congestion, and adjust their congestion windows according to the additive increase and multiplicative decrease (AIMD) algorithm. As a result, the throughput attained by TCP connections in the wireless environment is much less than it should be. The key problem that leads to the performance degradation is that TCP senders are unable to distinguish whether packet loss is a result of congestion in the wireline network or transmission errors on the wireless links. In this paper, we propose a light‐weight approach, called syndrome, to improving TCP performance in mobile wireless environments. In syndrome, the BS simply counts, for each TCP connection, the number of packets that it relays to the destination host so far, and attaches this number in the TCP header. Based on the combination of the TCP sequence number and the BS‐attached number and a solid theoretical base, the destination host will be able to tell where (on the wireline or wireless networks) packet loss (if any) occurs, and notify TCP senders (via explicit loss notification, ELN) to take appropriate actions. If packet loss is a result of transmission errors on the wireless link, the sender does not have to reduce its congestion window. Syndrome is grounded on a rigorous, analytic foundation, does not require the base station to buffer packets or keep an enormous amount of states, and can be easily incorporated into the current protocol stack as a software patch. Through simulation studies in ns‐2 (UCB, LBNL, VINT network simulator, http://www‐mash.cs.berkeley.edu/ns/ ), we also show that syndrome significantly improves the TCP performance in wireless environments and the performance gain is comparable to the heavy‐weight SNOOP approach (either with local retransmission or with ELN) that requires the base station to buffer, in the worst case, a window worth of packets or states. Copyright © 2001 John Wiley & Sons, Ltd.