Negative Acknowledgement Research Articles

A Reliable and Efficient Broadcasting Scheme for Mobile Ad Hoc Networks

This letter proposes a busy-tone based scheme for reliable and efficient broadcasting in mobile ad hoc networks. Control packets such as RTS, CTS and ACK are ignored in the broadcast scheme, and two busy tones are used, one for channel reservation and the other for negative acknowledgement. Unlike traditional schemes for reliable broadcasting, the proposed scheme is highly efficient as it achieves both collision avoidance and fast packet loss recovery. Simulation results are presented which show the effectiveness of the proposed scheme.

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.

Adaptive Hybrid ARQ Systems With BCJR Decoding

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose and evaluate a novel method of constructing Hybrid Automatic Repeat reQuest (HARQ) systems using the specific properties of the Bahl, Cocke, Jelinek, and Raviv (BCJR) error-correcting algorithm. Because the convergence to the actual codeword is not always guaranteed with the BCJR approach, we propose a system in which two different types of Negative AcKnowledgement messages (NAKs) are employed. The first type is the conventional 1-bit NAK, and the second type specifies retransmission pattern in such a way that the additional parity bits are concentrated on the parts of the code trellis that did not converge to a valid sequence. This is different from the traditional construction of rate-compatible punctured codes (RCPCs), which attempts to obtain the optimal weight distance properties of the codes without taking the convergence properties of the BCJR decoder into account. We demonstrate the performance of the algorithm using RCPCs, and we show that our system outperforms the best known conventional HARQ scheme in terms of the throughput and the average length of retransmitted blocks on practical Gaussian, Rayleigh, and thresholded Rayleigh channels. Moreover, as opposed to other adaptive HARQ algorithms, our solution requires no precomputed lookup tables, and it is robust to changes in the channel characteristics and only introduces moderate increase in feedback link throughput requirements. </para>

A comparative investigation of acknowledgment mechanisms for data transport in space internet

As the Internet is changing the world dramatically, an initiative is being proposed within NASA and in the military to expand the Internet into space and for network-centric warfare using network protocols. An end-to-end effective data transport protocol is critical to the reliable transfer of information in space and for a battlefield environment. Consequently, a reliable and efficient acknowledgment mechanism is required to accommodate these unreliable communication conditions. In this article we conduct a comparative investigation of existing data transport acknowledgment mechanisms for possible adoption in the unreliable environment of space or a similarly stressed communication environment. We also introduce the selective negative acknowledgment (SNACK), which is designed as a reliable retransmission mechanism for space and stressed tactical communications, followed by a brief performance evaluation of the effectiveness of SNACK compared to the standard SACK mechanism.

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.

TCP Proxy for Satellite Network

When used with satellite links, traditional TCP suffers from a number of performance problems, especially for higher propagation delay, bit error rate, asymmetrical bandwidth and signal attenuation due to rain. A new active proxy without breaking TCP semantic is proposed to improve TCP performance of satellite network. The congestion control algorithm in the proxy sets the window size according to the measurement information on bandwidth changes from the two probe packet pairs with different priorities. A stability analysis of the hybrid proxy system is performed. The loss recovery based on selective negative acknowledgement (SNACK) can work even if the clocks is not synchronized. The results demonstrate that proxy in combination with SNACK allows TCP to fully exploit the possible throughput of the satellite network.

Gap Processing Time Analysis of Stall Avoidance Schemes for High-Speed Downlink Packet Access with Parallel HARQ Mechanisms

The parallel multichannel stop-and-wait (SAW) hybrid automatic repeat request (HARQ) mechanism is one of key technologies for high-speed downlink packet access in the wideband code division multiple access system. However, this parallel HARQ mechanism may encounter a serious stall problem, resulting from the error of the negative acknowledgement (NACK) changing to the acknowledgement (ACK) in the control channel. In the stall situation, the receiver waits for a packet that will be no longer be sent by the transmitter and stops delivering the medium access control (MAC) layer packets to the upper layer. The stall issue seriously degrades the quality of service for the high-speed mobile terminal owing to the high probability of NACK-to-ACK errors. In this paper, we present an analytical approach to compare three stall avoidance schemes: the timer-based, the window-based, and the indicator-based schemes. To this end, we first propose a new performance metric-gap processing time, which is defined as the duration for a nonrecoverable gap appearing in the MAC layer reordering buffer until it is recognized. Second, we derive the probability mass functions and the closed-form expressions for the average gap processing time of these three stall avoidance schemes. It will be shown that our analytical results match the simulations well. Further, by analysis, we demonstrate that the indicator-based stall avoidance scheme outperforms the timer-based and the window-based schemes. The developed analytical approaches can help determine a proper number of processes for the parallel SAW HARQ mechanisms. We also show that the analytical formulas can be used to design the number of acceptable fully loaded users for an admission control policy subject to the gap processing time constraint. In the future, our analysis can facilitate the MAC/radio link control (RLC) cross-layer design because the gap processing time in the MAC layer is closely related to the RLC timeout mechanism and the window size in the RLC retransmission mechanism.

Accentuate the Negative

Three studies investigated the capacity of negative acknowledgment, the admission of an unfavorable quality, to elicit relatively positive responses. In Study 1, an acknowledgment that a written paragraph was confusing led individuals to rate the paragraph as clearer than they did when no acknowledgment was offered. In Study 2, a foreign speaker was rated as possessing a clearer voice when he acknowledged his strong accent than when he did not. In Study 3, a hypothetical college applicant's acknowledgment of receiving less than stellar high school grades resulted in a more positive evaluation of those grades. The interpersonal risks and benefits of negative acknowledgment as an impression-management strategy are discussed.

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.

On the Performance of an Indicator-Based Stall Avoidance Mechanism for High-Speed Downlink Packet Access Systems

The stall of delivering medium access control (MAC) layer data to the upper layer is a serious problem when a negative acknowledgement (NACK) control signal becomes an acknowledgement (ACK) signal, especially for a high-speed mobile terminal during handoff. Stall avoidance mechanisms aim to reduce such the transmission delay and keep in-sequence delivery of the MAC layer data to the upper layer. Recently, for providing high-speed downlink packet access (HSDPA) in the wideband code-division multiple access system, an indicator-based stall avoidance (ISA) mechanism was proposed to remove the nonrecoverable gap in the received out-of-sequence packets. In this paper, we derive the closed-form expression for the gap-processing time of the ISA mechanism when applying the multiprocess stop-and-wait (SAW) hybrid automatic repeat request (HARQ) mechanism. The derived analytical formulas can be used to understand performance tradeoffs between the gap-processing time and throughput in terms of various numbers of users and parallel processes when implementing the multiprocess SAW HARQ mechanism in the HSDPA system.

Reliability analysis of a data transmission model for multicast

As computer systems have been widely used, Internet, which is a network-of-network, has been greatly developed and rapidly spread all over the world. In addition to unicast transmissions of point-to-point, multicast transmissions of one-to-many and many-to-many have been recently used. This paper considers a stochastic model where data are transmitted through multicast. The data are divided into n packets at a transmission server, and their packets are transmitted successively to each receiver of multicast group. Positive (ACK) or negative (NAK) acknowledgements are returned from each receiver, by depending on whether he or she has received all packets, correctly or not. When the server has received NAK, retransmissions only for receivers with NAK are made. The mean time until the data transmission succeeds is analytically derived and an optimal policy which maximizes the throughput is discussed. Finally, numerical examples are given under suitable conditions.

Performance analysis of data transfer protocols over space communications

The work presented here concerns the study and the investigation of data transmission mechanisms, employed above the network layer of the protocol stack, used to transmit a data file through an end-to-end path composed of low Earth orbit (LEO) and geostationary (GEO) portions. A link built in the unexplored band W connects the Earth station to a LEO satellite (called DAVID). The communication among DAVID and other sites is performed by means of an inter-satellite link in Ka band, which connects the LEO satellite to a GEO one (called ARTEMIS) and the latter to the Earth stations. The main peculiarities of the investigated scenario consist of the visibility of a LEO satellite, limited to a few minutes, and of the only partial availability over time of a return link on the GEO path. LEO visibility may seriously affect the data communication because it implies suspend/resume mechanisms to match nonvisibility periods. The partial unavailability of the return link makes (transmission control protocol) TCP-based solutions barely applicable and implies the design of effective protocol architectures, in order to guarantee a reliable data communication. Several investigations about alternative novel architectures have been produced in order to individuate solutions that meet all the network requirements in terms of service reliability, exploitation of the network resources, and overall service time. The analysis is two-fold: on one hand the attention has been addressed to the LEO path, highlighting the features offered by a transport layer splitting approach and by an application-based solution exploiting the CCSDS (Consultative Committee for Space Data Systems) protocol stack, whose performance is compared with the results provided by the TCP/IP protocol stack, commonly used in the Internet (where IP stands for Internet Protocol). Concerning CEO path, assuming the return link only partially available, two alternatives of the CCSDS protocol stack have been investigated: the first one implies the use of a negative acknowledgement scheme, the second one does not require any availability of a return link. The two paths together compose the end-to-end communication, which is also globally analyzed on the basis of the performance offered by the solutions presented for the two portions. All the results have been obtained by using a simulator developed for the aim.

Analysis of CCSDS file delivery protocol: immediate NAK mode

We analyze the immediate negative acknowledgment (NAK) mode of the consultative committee for space data systems (CCSDS) file delivery protocol for the single-hop file transfer operation. We propose a timer setting rule that minimizes the expected time taken to transfer a file under the constraint that the throughput efficiency is maximized. Then, we derive the expected file delivery time and compare it with that of the deferred NAK mode. The main contribution is the closed-form expression for evaluating the performance metrics.

A Heuristic Buffer Management and Retransmission Control Scheme for Tree‐Based Reliable Multicast

We propose a heuristic buffer management scheme that uses both positive and negative acknowledgments to provide scalability and reliability. Under our scheme, most receiver nodes only send negative acknowledgments to their repair nodes to request packet retransmissions while some representative nodes also send positive acknowledgments to indicate which packets can be discarded from the repair node's buffer. Our scheme provides scalability because it significantly reduces the number of feedbacks sent by the receiver nodes. In addition, it provides fast recovery of transmission errors since the packets requested from the receiver nodes are almost always available in their buffers. Our scheme also reduces the number of additional retransmissions from the original sender node or upstream repair nodes. These features satisfy the original goal of tree-based protocols since most packet retransmissions are performed within a local group.

Bitmapped NAK feedback aggregation for improved reliable multicast scalability

A scheme for the router aggregation of bitmapped Negative AcKnowledgement (NAK) feedback packets in reliable multicast is presented. The scheme greatly improves the scalability of reliable multicast sessions. A brief probabilistically analysis of the performance of the scheme is provided, and its capacity to reduce feedback loads on shared links is simulated.

Feedback load characteristics of reliable multicast downloads in mobile networks

Feedback load in a reliable multicast session is a pressing research issue owing to the risk of a feedback implosion. Synchronous feedback packet arrivals greatly increase this risk. The work that is the subject of this report analysed Negative AcKnowledgement feedback packet arrivals for a reliable multicast session in a generic mobile network, obtaining a probabilistic description of the feedback load variation in time.

Analysing the PGM protocol with UPPAAL

Pragmatic General Multicast (PGM) is a reliable multicast protocol, designed to minimize both the probability of negative acknowledgement implosion and the load of the network due to the retransmission of lost packets. This protocol was presented to the Internet Engineering Task Force as an open reference specification. In this paper, we focus on the main reliability property which PGM intends to guarantee: a receiver either receives all data packets from transmissions and repairs or is able to detect unrecoverable data packet loss. We first propose a modelization of (a simplified version of) PGM via a network of timed automata. Using the UPPAAL model-checker, we then study the validity of the above reliability property, which does not always turn out to be verified, but to depend on the values of several parameters, which we underscore.

The impact of negative acknowledgments in shared memory scientific applications

Negative acknowledgments (NACKs) and subsequent retries, used to resolve races and to enforce a total order among shared memory accesses in distributed shared memory (DSM) multiprocessors, not only introduce extra network traffic and contention, but also increase node controller occupancy, especially at the home. We present possible protocol optimizations to minimize these retries and offer a thorough study of the performance effects of these messages on six scalable scientific applications running on 64-node systems and larger. To eliminate NACKs, we present a mechanism to queue pending requests at the main memory of the home node and augment it with a novel technique of combining pending read requests, thereby accelerating the parallel execution for 64 nodes by as much as 41 percent (a speedup of 1.41) compared to a modified version of the SGI Origin 2000 protocol. We further design and evaluate a protocol by combining this mechanism with a technique that we call write string forwarding, used in the AlphaServer GS320 and Piranha systems. We find that without careful design considerations, especially regarding atomic read-modify-write operations, this aggressive write forwarding can hurt performance. We identify and evaluate the necessary micro-architectural support to solve this problem. We compare the performance of these novel NACK-free protocols with a base bitvector protocol, a modified version of the SGI Origin 2000 protocol, and a NACK-free protocol that uses dirty sharing and write string forwarding as in the Piranha system. To understand the effects of network speed and topology the evaluation is carried out on three network configurations.

Caching policy design and cache allocation in active reliable multicast

Active reliable multicast (ARM) is a novel loss recovery scheme for large-scale reliable multicast. It uses active routers to perform NACK (negative-acknowledgement) consolidation and scoped retransmission. For optimizing the loss recovery performance of ARM under limited cache resources, the work in this paper aims at designing efficient and robust cache allocation schemes and caching policies. When a packet arrives at an active router, a caching policy determines if this packet should be cached and if cached, for how long. Three caching policies, timer-based, simple FIFO and probabilistic FIFO, are investigated in this paper. For a given amount of cache, the cache allocation problem is to find the best way to allocate the cache to each active router such that the overall network loss recovery performance can be optimized. Three cache allocation schemes, equal sharing, least requirement first and proportional allocation, are proposed. Among all the combinations of cache allocations and caching policies, we found that the proportional cache allocation with probabilistic FIFO caching policy gives the best overall performance.

Error-resilient video coding using long-term memory prediction and feedback channel

Abstract The MC–DCT-based video coding has been generally used for its efficiency and easy implementation, but it is very vulnerable in error-prone environments. In this paper, we address an error-resilient video coding using multiple reference frame, based on the long-term memory motion compensated prediction (LTMP) (IEEE Trans. Circuits Syst. Video Technol. 9 (1) (1999) 70), and an error concealment technique associated with the proposed technique. The rate-distortion optimization of T. Wiegand et al. (1999) is modified by adding dispersion measure of the temporal motion vectors in order to provide the error-resiliency and much improved error concealment performance. Also, the proposed algorithm confines the temporal error propagation using negative acknowledgement in feedback channel, in which both the corrupted area by channel errors and the error-propagated area are estimated and removed from the search region for the motion compensation. Thus, the proposed algorithm yields the similar performance to the forced intra update (FIU) in terms of the PSNR, but avoids the abrupt increase in the bitrate, resulting in more efficient network utilization than the FIU. By the computer simulations, we shall demonstrate that the proposed technique provides an acceptable performance both subjectively and objectively in error-prone environments, as compared with H.263 and LTMP, with or without the feedback messages.