Acknowledgement Scheme Research Articles

Wireless Fountain Coding with IEEE 802.11e Block ACK for Media Streaming in Wireline-cum-WiFi Networks: A Performance Study

We develop performance models for delay-sensitive uplink media streaming over a wireline-cum-WiFi network. Since the wireless channel is normally a bottleneck for such streaming, we modify the traditional 802.11e block acknowledgment (B-ACK) scheme to work with wireless fountain coding (WFC)-a packet-level coding scheme which codes packets in a similar manner to intrasession random network coding but delivers them in a manner similar to fountain coding. By using this modified B-ACK scheme, protocol complexity and wireless link-layer delay are potentially reduced. We analytically quantify this delay and use it to derive end-to-end packet loss/late probabilities when automatic repeat request (ARQ) and forward error correction (FEC) are jointly employed at the application-layer. We develop an integrated ns-3/EvalVid simulator to validate our models and compare them with the case when the traditional 802.11e B-ACK scheme is employed. Through simulations of video streaming, we observe that the modified B-ACK scheme does not always perform better than the traditional B-ACK scheme in terms of end-to-end packet loss/late probability and video distortion under certain conditions of the wireless channel. This observation leads us to propose a hybrid scheme that switches between the modified and traditional B-ACK strategies according to the conditions of the wireless channel and the number of packets to transmit in a block. Via simulations, we show the benefits of the hybrid scheme when compared to the traditional IEEE 802.11e B-ACK scheme under different network settings.

Acknowledgment based Reputation Mechanism to Mitigate the Node Misbehavior in Mobile Ad Hoc Networks

Problem statement: The cooperation between the nodes is essential to d iscover and maintain routes in mobile ad hoc network. Due to th e presence of misbehaving nodes, the node cooperation is not always guaranteed as the nodes a greed during the route discovery phase. This phenomenon results in frequent network partitioning and it makes the routing process difficult. It als o degrades the overall network performance and increases the control overhead due to frequent route discovery. Approach: This study proposed an Acknowledgment based Reputation Mechanism (ARM) to detected and isolated the misbehaving links in mobi le ad hoc networks. The proposed system introduced a novel dynamic acknowledgment ratio to make the nodes to request its second hop successor in the source route to acknowledge the receipt of the pack et. This makes the nodes to detect the behavior of the next hop links and to select the trusted routes for its transmissions. Results: The measured parameters such as packet drop ratio, malicious drop, false de tection and send buffer drop are reduced greatly. T he results also compared with the existing scheme and with original routing protocol performance. Conclusion/Recommendations: The proposed scheme performs better in detecting and isolating the misbehaving links. The overall network packet drop was decreased which in turn increase the overall network throughput. This shows that the proposed ac knowledgment scheme discovers the trusted routes with the presence of misbehaving nodes.

A request control scheme for data recovery in DVB‐IPDC systems with spatial and temporal packet loss

ABSTRACTRecently, digital video broadcasting‐handheld (DVB‐H) and IP datacast over DVB‐H (DVB‐IPDC) have been developed to support broadcasting services. DVB‐H is designed to support digital video broadcast for handheld devices, whereas DVB‐IPDC can integrate with an IP‐relay network to complement the data loss problem in DVB‐H. Assuming that WiMAX networks are adopted to support DVB‐IPDC, this paper points out two critical problems: group packet loss (GPL) and broadcast data handover (BDH). GPL occurs when there is a burst of retransmission requests for the same pieces of data with high spatial or temporal correlation. BDH happens when some devices that made the above requests handover to new serving cells. To solve these problems, we propose lazy wait and group acknowledgement schemes to alleviate duplicate requests by exploiting their spatial and temporal correlations. This not only reduces the requests submitted by neighboring devices in both space and time domains but also avoids handovering devices from sending duplicate requests in new cells. Through mathematical analysis, we show how to adaptively adjust the timers of lazy wait and group acknowledgement based on channel quality. Simulation results prove that our schemes can efficiently reduce retransmission requests and retransmission packets, thus alleviating congestion in the IP‐relay network. Copyright © 2011 John Wiley & Sons, Ltd.

Multi Hop Acknowledgement Scheme based Selfish Node Detection in Mobile Ad hoc Networks

Multi Hop Acknowledgement Scheme based Selfish Node Detection in Mobile Ad hoc Networks

Designing coded feedback for efficient network coding based opportunistic routing

A fundamental challenge faced by network coding (NC)-based opportunistic routing (OR) protocols is determining how many coded packets each forwarding node (FN) should transmit. Existing protocols address this challenge by combining NC with offline loss rate based heuristics to eliminate the overhead of feedback exchange, often at the cost of reduced performance in dynamic wireless environments. In this paper, we present a novel solution to this challenge through the design of the CCACK protocol. CCACK introduces an online Cumulative Coded ACKnowledgment scheme which allows the protocol to sustain high performance in dynamic wireless environments, with practically zero overhead.

A performance analysis of block ACK scheme for IEEE 802.11e networks

The demand for the IEEE 802.11 wireless local-area networks (WLANs) has been drastically increasing along with many emerging applications and services over WLAN. However, the IEEE 802.11 medium access control (MAC) is known to be limited in terms of its throughput performance due to the high MAC overhead, such as interframe spaces (IFS) or per-frame based acknowledgement (ACK) frame transmissions. The IEEE 802.11e MAC introduces the block ACK scheme for improving the system efficiency of the WLAN. Using the block ACK scheme can reduce the ACK transmission overhead by integrating multiple ACKs for a number of data frames into a bitmap that is contained in a block ACK frame, thus increasing the MAC efficiency. In this paper, we mathematically analyze the throughput and delay performance of the IEEE 802.11e block ACK scheme in an erroneous channel environment. Our extensive ns-2 simulation results validate the accuracy of our analytical model and they further demonstrate that the block ACK scheme enhances the MAC throughput performance at the cost of the resequencing delay at the receiving buffer .

Efficient Network-Coding-Based Opportunistic Routing Through Cumulative Coded Acknowledgments

The use of random linear network coding (NC) has significantly simplified the design of opportunistic routing (OR) protocols by removing the need of coordination among forwarding nodes for avoiding duplicate transmissions. However, NC-based OR protocols face a new challenge: How many coded packets should each forwarder transmit? To avoid the overhead of feedback exchange, most practical existing NC-based OR protocols compute offline the expected number of transmissions for each forwarder using heuristics based on periodic measurements of the average link loss rates and the ETX metric. Although attractive due to their minimal coordination overhead, these approaches may suffer significant performance degradation in dynamic wireless environments with continuously changing levels of channel gains, interference, and background traffic. In this paper, we propose CCACK, a new efficient NC-based OR protocol. CCACK exploits a novel Cumulative Coded ACKnowledgment scheme that allows nodes to acknowledge network-coded traffic to their upstream nodes in a simple way, oblivious to loss rates, and with negligible overhead. Through extensive simulations and testbed experiments, we show that CCACK greatly improves both throughput and fairness compared to MORE, a state-of-the-art NC-based OR protocol.

Video transmission enhancement in presence of misbehaving nodes in MANETs

Mobile Ad-hoc NETworks (MANET) are infrastructureless networks where self-configuring mobile nodes are connected by wireless links. Because of its decentralized operation, these nodes rely on each other to store and forward packets. Video transmission over MANETs is more challenging than over conventional wireless networks due to rapid topology changes and lack of central administration. Most of the proposed MANET protocols assume that all nodes are working within a cooperative and friendly network context. However, misbehaving nodes that exhibit abnormal behaviors can disrupt the network operation and affect the network availability by refusing to cooperate to route packets due to their selfish or malicious behavior. In this paper, we examine the effect of packet dropping attacks on video transmission over MANETs. We also study the effects of mitigation using intrusion detection systems to MANET in presence of video traffic. To the best of our knowledge, this is the first attempt to study multimedia over such environments. We propose a novel intrusion detection system, which is an adaptive acknowledgment scheme (AACK) with the ability to detect misbehaved nodes and avoid them in other transmissions. The aim of AACK scheme is to overcome watchdog weaknesses due to collisions and limited transmission power and also to improve TWOACK scheme. To demonstrate the performance of our proposed scheme, simulation experiments are performed. The results of our experiments show that MPEG4 is more suitable for our simulation environment than H264 video traffic. The simulation results show that AACK scheme provides better network performance with less overhead than other schemes; it also shows that AACK outperforms both TWOACK and watchdog in video transmission applications in the presence of misbehaving nodes.

Multilevel Control Signaling for Hybrid ARQ in the UMTS HSDPA System

In this paper, we propose and analyze a multi-level acknowledgement scheme for hybrid ARQ (H-ARQ) systems, which modifies the general ACK/NAK signals to represent multilevel information. For instance, the other signals except the ACK/NAK signals may be used for scheduling of retransmission in the H-ARQ scheme, which results in increasing the resolution of the uplink channel estimation signals. Simulation results demonstrate that when the retransmission interval is set to the optimal length, the proposed H-ARQ scheme shows a 0.5-2dB gain with properly selected parameters.

Efficient TCP variant with congestion notification for heterogeneous networks

In wireless networks, the packet loss may occur due to high bit error rate, packet corruption and link failures. The existing implementations of TCP interpret the loss occurrence is only due to congestion. This erratic prediction reduces the flow rate of TCP segments and it directly degrades its performance. The TCP variants like TCP New Jersey and TCP NJ+ achieve improvements in goodput over existing TCP NewReno by distinguishing wireless losses from congestion losses. In this paper, we propose an explicit congestion notification (ECN) enabled negative acknowledgement scheme SNACK-NJ, based on TCP NJ+ to further improve the performance of TCP over wireless networks. The simulation results confirm that the proposed scheme outperforms the conventional TCP implementations.

Dynamic Bandwidth Allocation for QoS Provisioning in IEEE 802.16 Networks with ARQ-SA

In this paper, bandwidth allocation, in terms of distributing available data slots among different users, is studied for QoS provisioning in IEEE 802.16 networks. By considering the automatic repeat request with selective acknowledgement (ARQ-SA) scheme for erroneous wireless channels, a mathematical model is established to theoretically analyze the delay performance of transmitting service data unit (SDU) under a multiuser environment. The analytical results indicate that the delivery delay of the SDU is dominated by the time spent for the first transmission of all its protocol data units (PDUs). Based on this observation, a novel dynamic bandwidth allocation algorithm is proposed and a detailed performance analysis is provided. Simulation results show that the proposed bandwidth allocation algorithm can significantly improve the delay performance of SDUs and ensure the fairness among different users.

Robust time‐division channel‐access approach for an ad hoc underwater network

An ad hoc underwater network is formed by a cluster of stationary nodes that can act as a source, destination, or a relay, in which data packet usually travels across multiple hops. Using a time-division scheme where the propagation delay between the nodes is used as a packet queuing buffer optimises throughput. This requires accurate knowledge of the relative ranges of all the nodes, a high level of accuracy in time-synchronisation, and restricts changes in the position of the nodes especially in the absence of a central server or master node within the network. A method that offers greater robustness is by using a time-slotted approach, where each node is offered a time-slot sufficient for one transmission to reach its maximum effective range. A passive acknowledgement scheme is implemented where a node listens for acknowledgement when the transmitted is being relayed. Nodes monitor other time-slots for the opportunity to contend for idle slots in order to enhance throughput. Results obtained from simulations demonstrate that this method is robust in supporting changes in the relative distances between the nodes, and can operate with a time synchronisation error of up to 1 second.

Rateless Forward Error Correction for Topology-Transparent Scheduling

Topology-transparent scheduling for mobile wireless ad hoc networks has been treated as a theoretical curiosity. This paper makes two contributions towards its practical deployment: (1) We generalize the combinatorial requirement on the schedules and show that the solution is a cover-free family. As a result, a much wider number and variety of constructions for schedules exist to match network conditions. (2) In simulation, we closely match the theoretical bound on expected throughput. The bound was derived assuming acknowledgments are available immediately. We use rate less forward error correction (RFEC) as an acknowledgment scheme with minimal computational overhead. Since the wireless medium is inherently unreliable, RFEC also offers some measure of automatic adaptation to channel load. These contributions renew interest in topology-transparent scheduling when delay is a principal objective.

Improving TCP performance with bandwidth estimation and selective negative acknowledgment in wireless networks

This paper investigates the performance of the transmission control protocol (TCP) transport protocol over IEEE 802.11 infrastructure based wireless networks. A wireless link is generally characterized by high transmission errors, random interference 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's performance. This paper examines the impact of the lossy nature of IEEE 802.11 wireless networks on the TCP performance and proposes a scheme to improve the performance of TCP over wireless links. A negative acknowledgment scheme, selective negative acknowledgment (SNACK), is applied on TCP over wireless networks and a series of ns-2 simulations are performed to compare its performance against that of other TCP schemes. The simulation results confirm that SNACK and its proposed enhancement SNACK-S, which incorporates a bandwidth estimation model at the sender, outperform conventional TCP implementations in 802.11 wireless networks.

Reliable bursty convergecast in wireless sensor networks

We address the challenges of bursty convergecast in multi-hop wireless sensor networks, where a large burst of packets from different locations needs to be transported reliably and in real-time to a base station. Via experiments on a 49 MICA2 mote sensor network using a realistic traffic trace, we determine the primary issues in bursty convergecast, and accordingly design a protocol, RBC (for Reliable Bursty Convergecast), to address these issues: To improve channel utilization and to reduce ack-loss, we design a window-less block acknowledgment scheme that guarantees continuous packet forwarding and replicates the acknowledgment for a packet; to alleviate retransmission-incurred channel contention, we introduce differentiated contention control. Moreover, we design mechanisms to handle varying ack-delay and to reduce delay in timer-based retransmissions. We evaluate RBC, again via experiments, and show that compared to a commonly used implicit-ack scheme, RBC doubles packet delivery ratio and reduces end-to-end delay by an order of magnitude, as a result of which RBC achieves a close-to-optimal goodput.

CHEMAS: Identify suspect nodes in selective forwarding attacks

Selective forwarding attacks may corrupt some mission-critical applications such as military surveillance and forest fire monitoring in wireless sensor networks. In such attacks, most of the time malicious nodes behave like normal nodes but will from time to time selectively drop sensitive packets, such as a packet reporting the movement of the opposing forces, and thereby make it harder to detect their malicious nature. In this paper, we propose CHEMAS (CHEckpoint-based Multi-hop Acknowledgement Scheme), a lightweight security scheme for detecting selective forwarding attacks. Our scheme can randomly select part of intermediate nodes along a forwarding path as checkpoint nodes which are responsible for generating acknowledgements for each packet received. The strategy of random-checkpoint-selection significantly increases the resilience against attacks because it prevents a proportion of the sensor nodes from becoming the targets of attempts to compromise them. In our scheme, each intermediate node in a forwarding path, if it does not receive enough acknowledgements from the downstream checkpoint nodes, has the potential to detect abnormal packet loss and identify suspect nodes. We explore the feasibility of our detection scheme using both theoretical analysis and simulations. The simulation results show that our scheme can achieve a high detection rate, even in harsh radio conditions. The communication overhead incurred by our scheme is also within reasonable bounds.

Reverse acknowledgment (ra) scheme: fast detection of retransmission failures for SR-ARQ

This letter proposes a simple modification called reverse acknowledgement (RA) scheme to a negative acknowledgement (NAK)-based selective repeat automatic repeat request (SR-ARQ) protocol for its fast loss recovery. By adopting the RA scheme, a NAK-based SR-ARQ receiver can detect and recover retransmission failures without invoking retransmission timeouts (RTOs). By OPNET simulations, we evaluate the performance of the RA scheme in terms of the transport delay and re-sequencing delay and show that the RA scheme considerably improves the performance of NAK-based SR-ARQ.

Investigation of the block ACK scheme in wireless ad hoc networks

A Block Transmission and Acknowledgement (BTA) scheme, also called Block ACK, has been proposed in the IEEE 802.11e wireless local area networks (WLAN) specification to improve efficiency of the me...

Investigation of the block ACK scheme in wireless ad hoc networks

AbstractA Block Transmission and Acknowledgement (BTA) scheme, also called Block ACK, has been proposed in the IEEE 802.11e wireless local area networks (WLAN) specification to improve efficiency of the medium access control layer. The idea of the BTA scheme is to transmit multiple data frames followed by only one acknowledgement frame in a transmission block. In this paper, we present a theoretical model to evaluate the saturation throughput for the BTA scheme under error channel conditions in the ad hoc mode, validated with simulations. We show some advantages of BTA over the legacy MAC, and analyze how to select a proper number of frames for each transmission block. Results show that BTA is particularly effective in very high‐speed wireless networks, and it is important that the number of frames in each block is negotiated before transmissions to provide better efficiency. Copyright © 2006 John Wiley & Sons, Ltd.

Performance Analysis of Delayed Acknowledgment Scheme in UWB-Based High-Rate WPAN

The wireless personal area network (WPAN) is designed for short-range connectivity among fixed or portable moving devices. The ultra-wideband (UWB) technology is being defined as the physical-layer (PHY) support for the high-rate WPAN. At medium access control (MAC) layer of the WPAN, a delayed acknowledgment (Dly-ACK) or burst-ACK (B-ACK) scheme is introduced to improve the channel utilization by reducing the overhead of ACK. In this paper, the authors first study the delay performance of the Dly-ACK scheme. An analytical model is developed for the Dly-ACK mechanism, and the delay is decomposed into queuing delay and delivery delay. These delay metrics are derived, and some important observations are obtained. In particular, there exists an optimal burst size, which is determined by the input traffic load and is very insensitive to the channel error rate within a normal error-rate range. It is also demonstrated that Dly-ACK cannot work properly if the burst size is fixed. The authors then propose a dynamical Dly-ACK scheme that can adaptively change its burst size according to the queue buffer size. Simulation results show that the dynamical scheme can improve the delay performance significantly.