Wireless Link Errors Research Articles

Fundamental Performance Limits on Terahertz Wireless Links Imposed by Group Velocity Dispersion

A theoretical framework and numerical simulations quantifying the impact of atmospheric group velocity dispersion (GVD) on wireless terahertz communication link error rate were developed based upon experimental work. This article presents, for the first time, predictions of symbol error rate (SER) as a function of link distance, signal bandwidth, signal-to-noise ratio (SNR), and atmospheric conditions, revealing that long-distance, broadband terahertz communication systems may be limited by intersymbol interference stemming from GVD, rather than attenuation. In such dispersion limited links, increasing signal strength does not improve the SER and, consequently, theoretical predictions of SER based only on SNR are invalid for the broadband case. This article establishes a new and necessary foundation for link budget analysis in future long-distance terahertz communication systems that accounts for the nonnegligible effects of both attenuation and dispersion.

Packet Loss Differentiation Over Manet Based on a BP Neural Network

An adaptive distributed routing algorithm is essential in MANETs, since there is no central routing system. Actually, there is no central point of coordination; each node is responsible for forwarding data packets to other nodes, thereby acting as router and host. A packet might travel through multiple intermediary ad hoc nodes in order to arrive to its destination, while the nature of wireless multi-hop channel is bringing in various types of packet losses. This paper focuses on three main reasons of online packet losses in MANETs: (1) losses due to wireless link errors; (2) losses due to congestion; and (3) losses due to route alteration. It proposes a deep learning-based algorithm for packet loss discrimination. The algorithm uses the backpropagation neural network (BPNN) concept. We performed simulation experiments for evaluating the performance of the proposed loss discrimination algorithm under different network configurations. Through simulation results, we confirmed that the proposed algorithm improves packet loss discrimination and route alteration in the network. It also reduces congestion and increases network throughput.

TCP adaptation with network coding and opportunistic data forwarding in multi-hop wireless networks

Opportunistic data forwarding significantly increases the throughput in multi-hop wireless mesh networks by utilizing the broadcast nature of wireless transmissions and the fluctuation of link qualities. Network coding strengthens the robustness of data transmissions over unreliable wireless links. However, opportunistic data forwarding and network coding are rarely incorporated with TCP because the frequent occurrences of out-of-order packets in opportunistic data forwarding and long decoding delay in network coding overthrow TCP’s congestion control. In this paper, we propose a solution dubbed TCPFender, which supports opportunistic data forwarding and network coding in TCP. Our solution adds an adaptation layer to mask the packet loss caused by wireless link errors and provides early positive feedbacks to trigger a larger congestion window for TCP. This adaptation layer functions over the network layer and reduces the delay of ACKs for each coded packet. The simulation results show that TCPFender significantly outperforms TCP/IP in terms of the network throughput in different topologies of wireless networks.

Queueing analysis of the DRX power saving mechanism in fault-tolerant 3GPP LTE wireless networks

Energy efficiency and high reliability are major aspects of modern mobile wireless networks. Therefore, it is a critical step to use power management methods along with fault-tolerant techniques. In this paper, we mathematically investigate the Discontinuous Reception, a power saving mechanism in 3GPP LTE wireless networks, with checkpointing and rollback recovery using a variant of an M/G/1 queue with a modified service time and multiple vacations. Due to the lack of enough storage, the mobile device periodically stores its checkpoint data in a stable fixed server, and rolling back to the latest checkpoint when a transient fault or a wireless link error occurs. Various energy and performance metrics are obtained, while constrained optimization problems are formulated and solved. Extensive numerical results are provided, and give an insight into the operation of the model.

A modified vacation queueing model and its application on the Discontinuous Reception power saving mechanism in unreliable Long Term Evolution networks

In this paper, Discontinuous Reception, a power saving mechanism in Long Term Evolution wireless networks, is analytically investigated in the presence of transient faults by using an unreliable M/G/1 queue with multiple vacations. System failures may occur either due to transient faults in the mobile device or due to wireless link errors. When a failure occurs, the device may request the retransmission of the packet after a recovery period. In such a case, the power consumption will be further increased. Steady state analysis is presented, and decomposition results are discussed. Energy and performance metrics are obtained, and used to provide useful numerical results.

A Rate based Congestion Control Mechanism Using Fuzzy Controller in MANETs

The traditional congestion control mechanism TCP, performs very poorly in MANETs Because there are a number of new challenges such as wireless link error, medium contention and frequent route failures in this kind of networks. In this paper, we propose a fuzzy adhoc rate-based congestion control (FARCC) to enhance the efficiency of network in MANETs. In FARCC, we use a rate-based transmission scheme using two fuzzy controller of zero order Takagi Sugeno Kang (TSK) model to congestion detection and congestion control. The FARCC sender adjusts data rate by receiving a feedback packet from FARCC destination. NS2-based simulation results show that FARCC outperforms ITP and ATP to achieve, in terms of throughput and fair resource allocation in AdHoc networks under random topology.

Reliable Cluster-Based Routing Algorithms in Wireless Sensor Networks

With advanced micro-electromechanical technology, the development of small-size, low-cost, and low-power sensors that possess sensing, signal processing and wireless communication capabilities is becoming popular than ever. To achieve the energy efficiency in the wireless sensor networks, LEACH has been proposed as a routing protocol, composing of a few clusters, each of which consists of member nodes that sense the data, and head nodes that deliver the collected data from member nodes to a sink node. When wireless link error occurs, LEACH may miss some messages because of only one cluster head. As our proposed scheme manages two cluster heads for each cluster, there should be higher probabilities for messages to reach the sink node. Simulation results show that our proposed algorithm provides more robust than LEACH when wireless link error occurs.

Stochastic method for power-aware checkpoint intervals in wireless environments: Theory and application

The checkpoint and rollback scheme is a useful fault-tolerance method for mobile devices in wireless environments. Since battery power is one of the most critical resources for mobile devices, it is important to identify optimal checkpoint intervals that minimize power consumption. In this paper, we propose a method that minimizes power consumption in wireless remote checkpoint environments by considering environmental parameters such as device failure rate, wireless link error rate, and checkpoint overhead. To evaluate the proposed solution, we conducted analytical estimations, simulations, and experimental measurements in a real test-bed.

Provisioning QoS for WiFi-enabled Portable Devices in Home Networks

Wi-Fi-enabled portable devices have recently been introduced into the consumer electronics market. These devices download or upload content, from or to a host machine, such as a personal computer, a laptop, a home gateway, or a media server. This paper investigates the fairness among multiple Wi-Fi-enabled portable devices in a home network when they are simultaneously communicated with the host machine. First, we present that, a simple IEEE 802.11-based home network suffers from unfairness, and the fairness is exaggerated by the wireless link errors. This unfairness is due to the asymmetric response of the TCP to data-packet loss and to acknowledgment-packet loss, and the wireless link errors that occur in the proximity of any node; the errors affect other wireless devices through the interaction at the interface queue of the home gateway. We propose a QoS-provisioning framework in order to achieve per-device fairness and service differentiation. For this purpose, we introduce the medium access price, which denotes an aggregate value of network-wide traffic load, per-device link usage, and per-device link error rate. We implemented the proposed framework in the ns-2 simulator, and carried out a simulation study to evaluate its performance with respect to fairness, service differentiation, loss and delay. The simulation results indicate that the proposed method enforces the per-device fairness, regardless of the number of devices present and regardless of the level of wireless link errors; furthermore it achieves high link utilization with only a small amount of frame losses.

End-to-end loss differentiation for video streaming with wireless link errors

Video delivery in heterogeneous wired/wireless networks is challenging, since link errors commonly degrade throughput performance, smoothness, and eventually impair the playback quality. We present an end-to-end Loss Differentiation Mechanism (LDA) which effectively decouples congestion from wireless loss in order to abolish the damage of error-induced multiplicative decrease on flow throughput and smoothness. The proposed LDA relies on Round Trip Time measurements to estimate the queuing delay and determine the appropriate error-recovery strategy. This mechanism can be easily adapted and incorporated into existing Additive Increase Multiplicative Decrease (AIMD) protocols, enabling them to utilize the available resources more efficiently. In this context, we incorporate the LDA into AIMD-based Scalable Streaming Video Protocol (SSVP), an end-to-end TCP-friendly protocol optimized for video streaming applications. Based on simulation results, we show that the combined approach provides the desired functionality to bind operationally wired and wireless links, within the framework of bandwidth efficiency, smoothness, and fairness.

SVM-based loss differentiation algorithm for wired-cum-wireless networks

In a hybrid wired-cum-wireless network environment, packet loss may happen because of congestion or wireless link errors. Therefore, differentiating the cause is important for helping transport protocols take actions to control congestion only when the loss is caused by congestion. In this article, an end-to-end loss differentiation mechanism is proposed to improve the transmission performance of transmission control protocol (TCP)-friendly rate control (TFRC) protocol. Its key design is the introduction of the outstanding machine learning algorithm – the support vector machine (SVM) into the network domain to perform multi-metric joint loss differentiation. The SVM is characterized by using end-to-end indicators for input, such as the relative one-way trip time and the inter-arrival time of packets fore-and-aft the loss, while requiring no support from intermediate network apparatus. Simulations are carried out to evaluate the loss differentiation algorithm with various network configurations, such as with different competing flows, wireless loss rate and queue size. The results show that the proposed classifier is effective under most scenarios, and that its performance is superior to the ZigZag, mBiaz and spike (ZBS) scheme.

Transport mechanism for streaming media in wireless network

A novel transport protocol Wireless Multimedia Transport Congestion Control (WMTCC) to was presented to improve the performance of streaming media transmission over wireless networks. The proposed protocol can distinguish packet loss due to network congestion from packet loss due to wireless link error by sending probing packets. In this way the sender can get the accurate state of the networks and adjust the transmission rate appropriately to maintain the Quality of Service (QoS) of the streaming media services. Due to the accurate distinguishing of the packet loss between network congestion and wireless link error, the protocol can maintain high throughput even with high bit error rate. The simulation results show that the new protocol can get higher throughput and larger congestion window in wireless networks and performs consistently better than other existing mechanisms.

TCP-friendly congestion control for streaming real-time applications over wireless networks

Congestion control for streaming real-time applications, which need smoothness of the transmission rate, should be transmission control protocol (TCP)-friendly. Moreover, in wireless networks, TCP-friendly congestion control should be based on differentiation of packet losses due to congestion and wireless link error to improve network utilisation. The authors propose a TCP-friendly congestion control algorithm based on explicit congestion notification over the wireless networks. The simulation results show that the proposed algorithm utilises the link bandwidth efficiently, providing smoothness of the transmission rate.

Improving performance of TCP over mobile wireless networks

Mobile IP is a network layer protocol for handling mobility of hosts in the Internet. However, mobile IP handoff causes degradation of TCP performance. Hence, there is a need for improving performance of TCP over mobile IP in wireless mobile networks. We propose an approach which handles losses due to both wireless link errors and host mobility. To handle losses due to host mobility, a method for seamless handoff is proposed. Empirical results show that the scheme provides substantial improvement of performance.

Cross-Layer Design of Source Rate Control and Congestion Control for Wireless Video Streaming

Cross-layer design has been used in streaming video over the wireless channels to optimize the overall system performance. In this paper, we extend our previous work on joint design of source rate control and congestion control for video streaming over the wired channel, and propose a cross-layer design approach for wireless video streaming. First, we extend the QoS-aware congestion control mechanism (TFRCC) proposed in our previous work to the wireless scenario, and provide a detailed discussion about how to enhance the overall performance in terms of rate smoothness and responsiveness of the transport protocol. Then, we extend our previous joint design work to the wireless scenario, and a thorough performance evaluation is conducted to investigate its performance. Simulation results show that by cross-layer design of source rate control at application layer and congestion control at transport layer, and by taking advantage of the MAC layer information, our approach can avoid the throughput degradation caused by wireless link error, and better support the QoS requirements of the application. Thus, the playback quality is significantly improved, while good performance of the transport protocol is still preserved.

Snug-Vegas and Snug-Reno: efficient mechanisms for performance improvement of TCP over heterogeneous networks

Improving the performance of the traditional TCP in wireless IP communications has been an active research area. The significant cause of packet losses in such heterogenous networks is no longer limited to network congestion. The performance degradation of TCP in wireless and wired-wireless hybrid networks is mainly due to its lack of ability to differentiate the packet losses caused by network congestions from the losses caused by wireless link errors. New variants of TCP Vegas and TCP Reno named Snug-Vegas and Snug-Reno, respectively, are proposed. By using random-loss indications marked by base stations, Snug-Vegas and Snug-Reno may detect random packet losses precisely. Through the packet loss differentiation, Snug-Vegas and Snug-Reno react appropriately to the losses, and based on the simulation results, it is seen that the throughput of connection over heterogeneous networks can be significantly improved.

A Generalized Analytical Framework for SMPT in a Multicode CDMA Wireless System

Simultaneous MAC Packet Transmission (SMPT) has recently been proposed for stabilizing the throughput over wireless links, which is one of the key challenges in providing high-quality wireless multimedia services. SMPT stabilizes the wireless link by transmitting multiple packets on multiple CDMA channels in parallel in response to packet drops due to wireless link errors. These parallel packet transmissions stabilize the link layer throughput, but they also increase the interference level in a given cell of a cellular network or cluster of an ad-hoc network, which in turn reduces the number of traffic flows that can be simultaneously supported in a cell/cluster. We have recently developed an analytical framework for the class of SMPT mechanisms for a simple Bernoulli packet generation process, which does not reflect the oftentimes bursty packet generation processes encountered in real networks. In this paper we develop a generalized analytical framework for SMPT, which accommodates bursty packet traffic (and also non-bursty Bernoulli traffic). This framework expresses the system dynamics in transition probabilities for a Markov chain and calculates the effects of the interference through an iterative approach. The numerical results from our analytical framework and verifying simulations indicate that SMPT provides a significant reduction in packet loss and buffer occupancies (and delay), especially for persistent traffic bursts, in exchange for a reduced number of supported flows. Our analytical framework quantifies these system trade-offs with good accuracy and can thus be employed for resource management.

Improving TCP performance in integrated wireless communications networks

Many analytical and simulation-based studies of TCP performance in wireless environments assume an error-free and congestion-free reverse channel that has the same capacity as the forward channel. Such an assumption does not hold in many real-world scenarios, particularly in the hybrid networks consisting of various wireless LAN (WLAN) and cellular technologies. In this paper, we first study, through extensive simulations, the performance characteristics of four representative TCP schemes, namely TCP New Reno, SACK, Veno, and Westwood, under the network conditions of asymmetric end-to-end link capacities, correlated wireless errors, and link congestion in both forward and reverse directions. We then propose a new TCP scheme, called TCP New Jersey, which is capable of distinguishing wireless packet losses from congestion packet losses, and reacting accordingly. TCP New Jersey consists of two key components, the timestamp-based available bandwidth estimation (TABE) algorithm and the congestion warning (CW) router configuration. TABE is a TCP-sender-side algorithm that continuously estimates the bandwidth available to the connection and guides the sender to adjust its transmission rate when the network becomes congested. TABE is immune to the ACK drops as well as ACK compression. CW is a configuration of network routers such that routers alert end stations by marking all packets when there is a sign of an incipient congestion. The marking of packets by the CW-configured routers helps the sender of the TCP connection to effectively differentiate packet losses caused by network congestion from those caused by wireless link errors. Our simulation results show that TCP New Jersey is able to accurately estimate the available bandwidth of the bottleneck link of an end-to-end path; and the TABE estimator is immune to link asymmetry, bi-directional congestion, and the relative position of the bottleneck link in the multi-hop end-to-end path. The proactive congestion avoidance control mechanism proposed in our scheme minimizes the network congestion, reduces the network volatility, and stabilizes the queue lengths while achieving more throughput than other TCP schemes.

TCP-Jersey for Wireless IP Communications

Improving the performance of the transmission control protocol (TCP) in wireless Internet protocol (IP) communications has been an active research area. The performance degradation of TCP in wireless and wired-wireless hybrid networks is mainly due to its lack of the ability to differentiate the packet losses caused by network congestions from the losses caused by wireless link errors. In this paper, we propose a new TCP scheme, called TCP-Jersey, which is capable of distinguishing the wireless packet losses from the congestion packet losses, and reacting accordingly. TCP-Jersey consists of two key components, the available bandwidth estimation (ABE) algorithm and the congestion warning (CW) router configuration. ABE is a TCP sender side addition that continuously estimates the bandwidth available to the connection and guides the sender to adjust its transmission rate when the network becomes congested. CW is a configuration of network routers such that routers alert end stations by marking all packets when there is a sign of an incipient congestion. The marking of packets by the CW configured routers helps the sender of the TCP connection to effectively differentiate packet losses caused by network congestion from those caused by wireless link errors. This paper describes the design of TCP-Jersey, and presents results from experiments using the NS-2 network simulator. Results from simulations show that in a congestion free network with 1% of random wireless packet loss rate, TCP-Jersey achieves 17% and 85% improvements in goodput over TCP-Westwood and TCP-Reno, respectively; in a congested network where TCP flow competes with VoIP flows, with 1% of random wireless packet loss rate, TCP-Jersey achieves 9% and 76% improvements in goodput over TCP-Westwood and TCP-Reno, respectively. Our experiments of multiple TCP flows show that TCP-Jersey maintains the fair and friendly behavior with respect to other TCP flows.

TP-Planet: A Reliable Transport Protocol for Interplanetary Internet

Space exploration missions are crucial for acquisition of information about space and the Universe. The entire success of a mission is directly related to the satisfaction of its communications needs. For this goal, the challenges posed by the InterPlaNetary (IPN) Internet need to be addressed. Current transmission control protocols (TCPs) have very poor performance in the IPN Internet, which is characterized by extremely high propagation delays, link errors, asymmetrical bandwidth, and blackouts. The window-based congestion control, which injects a new packet into the network upon an ACK reception, is responsible for such performance degradation due to high propagation delay. Slow start algorithms of the existing TCPs further contribute to the performance degradation by wasting long time periods to reach the actual data rate. Moreover, wireless link errors amplify the problem by misleading the TCP source to unnecessarily throttle the congestion window. The recovery from erroneous window decrease takes a certain amount of time, which is proportional to the round-trip time (RTT) and further decreases the network performance. In this paper, a reliable transport protocol (TP-Planet) is presented for data traffic in the IPN Internet. It is intended to address the challenges and to achieve high throughput performance and reliable data transmission on deep-space links of the IPN Backbone Network. TP-Planet deploys a rate-based additive-increase multiplicative-decrease (AIMD) congestion control, whose AIMD parameters are tuned to help avoid throughput degradation. TP-Planet replaces the inefficient slow start algorithm with a novel Initial State algorithm, which allows the capture of link resources in a very fast and controlled manner. A new congestion detection and control mechanism is developed, which decouples congestion decisions from single packet losses in order to avoid the erroneous congestion decisions due to high link errors. In order to reduce the effects of blackout conditions on the throughput performance, TP-Planet incorporates the blackout state procedure into the protocol operation. The bandwidth asymmetry problem is addressed by the adoption of delayed selective acknowledgment (SACK). Simulation experiments show that the TP-Planet significantly improves the throughput performance and addresses the challenges posed by the IPN Backbone Network.