Hybrid Automatic Repeat Request Protocol Research Articles

Adaptive Modulation/TDMA/TDD with Convolutionally Coded Type-II HybridARQ for Wireless Communication Systems

This paper proposes a time division multiple access/time division duplex (TDMA/TDD)-based adaptive modulation system (AMS) with a convolutionally coded Type-II Hybrid automatic repeat request (ARQ) protocol to achieve high throughput data transmission in wireless communication systems. First, this paper discusses the cause of throughput limitation of the conventional fixed-rate quaternary phase shift keying (QPSK) with ARQ protocol and suggests that the effective means to improve throughput performance are the reduction of re-transmission probability under bad channel condition and the increase of transmission bit rate per TDMA/TDD slot under good channel condition. Based on these strategies, this paper discusses an AMS with a convolutionally coded type-II hybrid ARQ protocol (type-II hybrid ARQ/AMS) and evaluates its performance by computer simulation. The results confirm that the proposed type-II hybrid ARQ/AMS can drastically improve throughput performances compared to the conventional fixed-rate QPSK with selective repeat ARQ protocol (SR-ARQ/QPSK) or a simple combination of SR-ARQ and AMS (SR-ARQ/AMS) under any channel conditions, especially under severe channel conditions.

A spread slotted CDMA/ALOHA system with hybrid ARQ for satellite multiple access

We propose and investigate a new type of satellite multiple access protocol that combines the characteristics of the spread slotted (SS)-ALOHA protocol, code division multiple access (CDMA), and the hybrid automatic repeat request (ARQ) error controlling and retransmission scheme, in order to increase the throughput by reducing the number of retransmissions and to keep the bit error rate (BER) of the satellite link low when the channel experiences heavy traffic. The main feature of our proposed system is the utilization of two different fields in the analysis of the satellite multiple access problem. Since the hub now possesses the forward error correction (FEC) capability to correct errors that appear after the CDMA despreading of the packets, the satellite does not need to ask so often for the retransmission of erroneous packets and will ask for retransmission only when the FEC error correcting capability is exceeded. This paper also presents the adaptive optimization of the balance between the CDMA processing gain and FEC coding gain in order to obtain a better throughput for the SS-CDMA/ALOHA with hybrid ARQ protocol for satellite multiple access. The optimization is made with the constraint of keeping the bandwidth of the transmitted packets constant during all times. According to this, the effective throughput of the protocol (information bits over total transmitted bits ratio) is improved by adaptively changing the CDMA and FEC codes used in the transmission. This adaptive optimization is done by observing the channel status or load and increasing or decreasing both coding schemes' gains. Computer simulations show the performance of the proposed multiple access scheme.

A unified analysis of hybrid ARQ protocol in frequency-hop spread-spectrum systems subject to frequency-selective fading and interference

This paper presents an exact analysis of the type-I hybrid automatic repeat request (ARQ) protocol for a frequency-hop (FH) communication system that uses symbol interleaving, multiple codewords per packet, and multiple symbols per dwell interval. The analysis relies on exact formulas for the probabilities of decoder error and failure with an arbitrary number of different conditional symbol error and erasure probabilities. We specialize our analysis to two channel models. The first channel exhibits frequency-selective fading, and the second exhibits frequency-selective interference. The results show that the interrelationships between system and channel parameters are complex and not always intuitive. Numerical results show that: (1) depending on the channel parameters, frequency-selective channel phenomena can result in either an improvement or degradation in system performance compared with an equivalent nonselective channel and (2) in a fading channel, increasing the number of symbols per dwell interval can result in a significant improvement in reliability at only a modest reduction in throughput.

An efficient hybrid ARQ protocol for point-to-multipoint communication and its throughput performance

This paper presents a new point-to-multipoint communication protocol, the nonselective repeat (NSR) protocol, for error control over broadcast channels. It is a hybrid forward-error-correction (FEC)/automatic-repeat-request (ARQ) scheme, based on the adaptive coding technique using incremental redundancy of Mandelbaum (1974). The FEC code is a rate-compatible punctured and shortened Reed-Solomon (RS) code, used for error correction only. The scheme is most attractive in situations where error occurrences are almost independent between the recipients of the messages. The throughput performance of the NSR protocol is analyzed in terms of all the parameters involved. Analysis shows that NSR significantly outperforms all the existing pure ARQ broadcast schemes. It is also shown that, even with a large number of recipients, NSR achieves performance which stays close to the capacity of the broadcast q-ary erasure channel, where q=2/sup m/ and m is the size in bits of a transmitted packet. Furthermore, on slow Rayleigh fading channels, this protocol is expected to provide better throughput performance than other hybrid ARQ protocols.

Type-II hybrid ARQ protocol using concatenated codes

The high throughput achieved by type-II hybrid automatic repeat request (ARQ) protocols can be enhanced by using the inner structure of a codeword in a concatenated coding scheme. The paper presents a new type-II hybrid scheme based on concatenated codes to which two retransmission strategies have been applied. The results on throughput bounds show that the proposed protocols are effective even in the case of communication channels with high error rates.

Protocol configuration and verification of an adaptive error control scheme over analog cellular networks

A high-speed and error-free voiceband data communication method using a hybrid automatic repeat request (ARQ) protocol over an analog cellular system is described. The present method adopts an adaptive error control scheme. This error control scheme automatically selects the optimal error correction code according to circuit bit error rate (BER), so as to match it to the frequently changing mobile radio propagation path conditions. This method adopts multiframe rejection as a retransmission scheme for a high throughput efficiency on the burst error circuit. Actual field evaluation was made by mounting this protocol on a CCITT V.22 bis modem with a data transmission speed of 2400 b/s and a modulation method using 16 carrier states over the Advanced Mobile Phone Service (AMPS) in Atlanta, GA, verifying that data communications can be achieved with an average throughput efficiency of 70% over a radio channel having a BER up to 10/sup -2/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance analysis of hybrid ARQ protocols in a slotted direct-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. >