Throughput analysis of some ARQ protocols in the presence offeedback errors

Automatic-repeat-request (ARQ) protocols have been analyzed for quite some time, but the issue of errors in the feedback channel has not received much attention. In some applications, such as digital mobile communications, this issue can be important. Accordingly, this paper examines the effect of feedback errors on the throughputs of the stop-and-wait (SW), go-back-N (GBN), and selective repeat (SR) ARQ protocols for the ease of a point-to-point channel under some feedback information assumptions. It is shown that the deleterious effects of feedback errors on the throughputs of continuous (e.g., GBN and SR) ARQ protocols can be greatly reduced by a simple modification in the retransmission operation, provided that the “complete state” of the receiver is sent back with each acknowledgment     

Comparison of two ARQ protocols in a Rayleigh fading channel

Go-back-N (GBN) and selective repeat (SR) protocols for automatic repeat request (ARQ) are compared in a frequency-nonselective Rayleigh fading channel. Protocols implemented in software are used in a computer-simulated fading channel to study the throughput of these protocols as a function of fading parameters, such as the mean signal-to-noise ratio (SNR), maximum Doppler frequency number of diversity branches, time-out period and round-trip delay. The purpose is to complement well-documented theoretical work in (1) providing some design considerations and (2) investigating quantitatively whether data communications combining detection-only coding, diversity, and basic ARQ protocols can offer reasonable throughput in a fading channel. Although based on a set of assumptions, the following conclusions remain valid: (1) SR is significantly superior to GBN when the fading rate is high; this advantage decreases as fading becomes slower; and (2) error detection combined with ARQ and diversity selection can provide reliable data communications in a Rayleigh fading channel     

Multichannel ARQ protocols

The performance of stop-and-wait, go-back-N, and selective-repeat ARQ protocols is examined for a multichannel system. The channels can either operate independently or jointly. For each protocol, the results obtained include throughput efficiency and delay. The results are also validated by computer simulations. The performance is compared to that of the single-channel system under the constraint of fixed total capacity. It is observed that the multichannel system has a chance to outperform the single-channel system     

Linear block codes for nonindependent errors

A computerised search procedure based on certain properties of the parity-check matrix of those block codes capable of correcting nonindependent errors is described which yields a considerable number of linear block codes that are capable of correcting random or burst errors.     

Performance of hybrid ARQ schemes for the fading channel

We define and adopt a theoretical method, based on the sphere-packing bound, for evaluating and comparing the achievable performance of different hybrid automatic repeat request schemes for the fading channel. The channel state evolution is assumed to be represented by a finite-state Markov chain. To assess the correctness and the accuracy of the analysis, some simulation results, based on the use of turbo codes, are also presented.     

Optimal adaptive multireceiver ARQ protocols

The authors study data link error control protocols suitable for point-to-multipoint communication where data are delivered to the destinations in the order they are sent. They study a series of adaptive protocols differing in the way that the sender uses the outcomes of the previous transmissions. The protocols are based on the go-back-N schemes discussed by I.S. Gopal and J.M. Jaffe (1984), whose protocols are generalized to the case where multiple copies of a message are sent (instead of just a single copy). The optimum number of copies is determined and is found to depend on how many receivers have not yet received the message. These adaptive protocols can be applied to all three basic ARQ (automatic repeat request) schemes, namely, stop-and-wait, go-back-N, and selective-repeat. A dynamic programming technique is used to solve this optimization problem. A throughput comparison shows that, by sending the optimum number of copies of a data frame instead of just a single copy, the performance will be significantly improved     

Self-stabilizing sliding window ARQ protocols

It is shown that implementing a practical self-stabilizing sliding window protocol requires a bound on the maximum delay or maximum memory of the communication channel involved. This motivates using communication channel models that incorporate a delay or memory bound. For such models, two new ARQ protocols are presented that self-stabilize by using 1 bit of overhead in each transmitted message. The protocols operate like selective repeat ARQ, except that when a fault places them in an incorrect (unsafe) state, the additional bit in the protocol messages allows automatic recovery. Following a transient fault, the bounded delay protocol stabilizes within four round-trip times. The bounded memory protocol stabilizes after sending at most 2(K+n) messages, where K the is maximum number of messages that can be stored in one direction on the channel, and n is the window size of the sender     

New ARQ protocols using concatenated codes

Two automatic-repeat-request (ARQ) protocols using a concatenated coding scheme are described. The structure, introduced in a codeword of a concatenated coding scheme, is used to improve the performance of ARQ protocols, especially for high error rates in the communication channel. The performance of the scheme described herein is derived through theoretical analysis. The results show that the proposed scheme outperform other similar ARQ protocols     

Performance analysis of ARQ schemes with code combining over Nakagami-m fading channel

This article investigates the performance of hybrid automatic repeat request (HARQ) with code combining over the ideally interleaved Nakagami-m fading channel. Two retransmission protocols with coherent equal gain code combining are adopted, where the entire frame and several selected portions of the frame are repeated in protocols Ⅰ and Ⅱ, respectively. Protocol Ⅱ could be viewed as a generalization of the recently proposed reliability-based HARQ. To facilitate performance analysis, an approximation of the product of two independent Nakagami-m distributed random variables is first developed. Then the approximate analysis is utilized to obtain exact frame error probability (FEP) for protocol Ⅰ, and the upper bound of the FEP for protocol Ⅱ. Furthermore, the throughput performance of both two protocols is presented. Simulation results show the reliability of the theoretical analysis, where protocol Ⅱ outperforms protocol Ⅰ in the throughput performance due to the reduced amount of transmitted information.     

Performance analysis of hybrid ARQ protocols in a slotteddirect-sequence code division multiple-access network: jamming analysis

An examination is made of the performance of type-I hybrid ARQ (automatic repeat request) protocols in a slotted direct-sequence CDMA (code-division multiple access) network operating in a hostile jamming environment. The network consists of an arbitrary number of transceivers arranged in a paired-off topology. The traffic arrival process is derived by means of a Markov model. Throughput-delay expressions are derived in terms of the channel cutoff rate and capacity. The effects of jammer state information are discussed. Network design parameters are identified and their dependency on system parameters is examined in detail. It is shown that, for a given population size, traffic intensity, and bit energy/jammer noise ratio, there is an optimal probability of retransmission, code rate, and processing gain that maximizes network performance in the presence of worst-case pulse jamming     

Analysis of ARQ protocols via signal flow graphs

A unified methodology using signal flow graphs is proposed and used to analyze several existing ARQ (automatic repeat request) protocols. The methodology offers a systematic and efficient way of obtaining throughput and delay. It also offers additional advantages in obtaining results such as the mean response time, and in analyzing the ARQ protocols in which the feedback channel is not error-free     

Impact of ARQ protocols on QoS in 3GPP systems

Traffic transmission over the radio channel requires appropriate techniques to preserve information integrity while maintaining the desired quality of service (QoS) and energy constraints. We focus on a possible configuration of the automatic repeat request (ARQ) protocol defined in the Third Generation Partnership Project (3GPP) technical specifications. A Markov model is developed in order to study the protocol behavior as channel characteristics change. Through this model, we evaluate the impact of the 3GPP ARQ scheme on the QoS of traffic services such as data file transfer and IP telephony. In the case of data transfer, a tradeoff between loss probability and energy efficiency is derived. In the case of IP telephony, we investigate the possibility of guaranteeing low maximum delay and low jitter by adopting the ARQ protocol as an error-recovery scheme.     

New modified stop-and-wait ARQ protocols for mobile communications

Mobile communication channels are frequently plagued by severe noise and disturbances such as multipath fading and doppler effects that severely degrade performance. Among the automatic-repeat-request (ARQ) protocols used to improve the communication channel reliability, the stop-and-wait (SW) is positively characterized by simple implementation and negatively by low throughputs. This work describes the application of some new SW protocols that retain the simple implementation of the classical SW schemes, while reducing the transmitter's wait state time to increase throughput. The performance of the modified SW protocols, derived through computer simulations, is shown to be comparable to that of more complex ARQ protocols.     

Performance of type-II hybrid ARQ in a shadowed Rician fading LEOsatellite-based spread slotted ALOHA communication channel

Type-II hybrid ARQ is applied to a shadowed Rician fading low earth-orbiting (LEO) satellite-based spread slotted ALOHA communication channel. In particular it is found to be effective in combating heavy shadowing     

Reducing time delay of ARQ protocols by simple error-correcting codes

Time delay analysis is carried out for type-I hybrid ARQ with BCH codes. It is found that the time delay of ARQ protocols can be significantly reduced by using simple BCH codes. Implementation trade-off can then be made between buffer size and simple decoding facilities to achieve maximum performance and minimum complexity.<>     

On the use of renewal theory in the analysis of ARQ protocols

An automatic-repeat-request (ARQ) Go-Back-N (GBN) protocol with unreliable feedback and time-out mechanism is studied, using renewal theory. Transmissions on both the forward and the reverse channels are assumed to experience Markovian errors. The exact throughput of the protocol is evaluated, and simulation results, that confirm the analysis, are presented. A detailed comparison of the proposed method and the commonly used transfer function method reveals that the proposed approach is simple and potentially more powerful     

New MIMO ARQ protocols and joint detection via sphere decoding

In this paper, we develop some new automatic repeat request (ARQ) protocols for multiple-input multiple-out (MIMO) flat-fading channels which adapt the bit-to-symbol mapping of each ARQ retransmission. We begin by defining a model for distinctly mapped transmissions through flat-fading MIMO channels. We characterize the effect that such a mapping diversity has on an integrated receiver utilizing sphere decoding. Varying the symbol mapping complicates the sphere decoding process, particularly for the enumeration of candidate solutions within the sphere. A technique that enables quick candidate enumeration is presented, utilizing concepts from existing closest point search schemes. The advantage of mapping diversity, in reducing bit error rate and reducing computational complexity, is presented along with simulation examples.     

A MAC/PHY cross-layer design for efficient ARQ protocols

In many wireless data systems, automatic repeat request (ARQ) and hybrid automatic repeat request (HARQ) work independently. In this paper, we introduce a new ARQ feedback scheme called Cross-Layer ARQ (CL-ARQ), where ARQ closely interoperates with HARQ by making use of the acknowledgement of HARQ internally. By doing so, CL-ARQ not only removes the overhead for ARQ acknowledgement messages, but also improves the average delivery delay and TCP throughput. Especially, when the entities in charge of HARQ and ARQ are located far apart geographically, CL-ARQ remarkably outperforms the legacy scheme.     

A hybrid ARQ protocol using integrated channel equalization

In this letter, a new hybrid automatic repeat request (ARQ) approach is presented to enhance receiver performance for communication systems employing forward error-correction codes in frequency-selective fading environments. This new approach involves a simple modification to the traditional turbo equalizer by combining multiple ARQ transmissions via integrated channel equalization. This modification leads to better computational efficiency, better exploitation of channel diversity, better channel-estimation ability, and improved performance (frame-error rates) when concatenated with an outer code. These improvements are verified through evaluations of extrinsic information transfer charts and ARQ simulations when compared with iterative combining of multiple transmissions.     

Performance of Single-Relay Cooperative ARQ Retransmission Strategies

In Cooperative Automatic Repeat reQuest (C-ARQ) protocols, the retransmission process between a pair of nodes can be assisted by a relay node. We investigate the performance of C-ARQ algorithms in cellular access networks, where the use of relays is a promising strategy for future evolutions. By means of Markov analysis and simulation we show that the implementation of acknowledgment signals from the relays and the retransmission policy at the base station have a notable impact on the throughput of the system.