• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1136-1144
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• 2010

In this paper, the effects of HARQ feedback error are evaluated in IEEE 802.16m system when the HARQ and ARQ interactions that utilize the HARQ feedback information is used. Also, the HARQ and ARQ interaction scheme considering HARQ feedback errors are proposed. The HARQ and ARQ interaction scheme improve the system throughput by using the HARQ feedback information instead of the ARQ feedback message, which reduce retransmission time. However, errors in the HARQ feedback information generate severe performance degradation. Especially, the local NAK errors between HARQ feedback error critically degrade the performance, because the local NAK errors lead the loss of ARQ blocks. We propose a channel state-based schemes for HARQ and ARQ interactions to mitigate the throughput degradation due to HARQ feedback errors. Simulation results show that the proposed scheme improves the throughput and the delay performance.

• ETRI Journal
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• v.26 no.5
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• pp.405-412
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• 2004

MC-CDMA, a multicarrier (MC) modulation scheme based on code division multiple access (CDMA), is the most likely candidate for the next generation of mobile radio communications. The rate compatible punctured turbo (RCPT) coded hybrid automatic repeat request (HARQ) has been found to give improved throughput performance in a direct sequence (DS) CDMA system. However, the extent to which the RCPT HARQ improves the throughput performance of an MC-CDMA system has not been fully understood. In this paper, we apply the RCPT HARQ to MC-CDMA and evaluate by computer simulations its performance in a frequency selective Rayleigh fading channel. We found that the performance of RCPT HARQ MC-CDMA is almost insensitive to channel characteristics. The performance can be drastically improved with receive diversity combined with space-time transmit diversity. In addition, the comparison of RCPT HARQ MC-CDMA, orthogonal frequency division multiplexing, and DS-CDMA shows that under similar conditions the throughput of MC-CDMA is the best in a frequency selective fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.370-378
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• 2007

The most appropriate low density parity check (LDPC) code for hybrid automatic repeat request (HARQ) system suitable for future multimedia communication systems is presented in this paper. HARQ system with punctured LDPC code is investigated at first. And two transmission schemes with parallel concatenated LDPC code are also presented and their performances are analyzed according to the various values of mean column weight (MCW). As a result, the parallel concatenated LDPC code with the diversity effect of information bit is considered to be more appropriate for HARQ system considering the throughput as well as error performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.5
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• pp.516-521
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• 2010

In the high-speed packet service, next generation mobile communication system has emerged as a major feature. If the fire of these high-speed D kit services and non-continuous transmission of data due to the symmetrical nature of daeyiteo traffic for D-CDMA system has been actively studied. In this paper, we apply turbo codes for D-CDMA has been investigated. Considering the nature of the system configuration of the transmission frame type, such as physical channel structure and channel coding has been investigated. In addition to TD-CDMA system, one HARQ gibeopjung hase Combining the performance analysis techniques were applied.

• Journal of Communications and Networks
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• v.14 no.5
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• pp.510-517
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• 2012

This paper analyzes the performance of voice-over-Internet protocol (VoIP) services in terms of the system throughput, the packet delay, and the signaling overhead in a mobile WiMAX system with a hybrid automatic repeat request (HARQ) mechanism. Furthermore, a queueing analytical model is developed with due consideration of adaptive modulation and coding, the signaling overhead, and the retransmissions of erroneous packets. The arrival process is modeled as the sum of the arrival rate at the initial transmission queue and the retransmission queue, respectively. The service rate is calculated by taking the HARQ retransmissions into consideration. This paper also evaluates the performance of VoIP services in a mobile WiMAX system with and without persistent allocation; persistent allocation is a technique used to reduce the signaling overhead for connections with a periodic traffic pattern and a relatively fixed payload. As shown in the simulation results, the HARQ mechanism increases the system throughput as well as the signaling overhead and the packet delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.662-668
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• 2013

Mobile communication systems have been adopting link adaptive transmission schemes such as adaptive modulation and coding (AMC) and hybrid-ARQ (HARQ). Incremental redundancy (IR) HARQ scheme is known to be highly efficient in terms of throughput and power consumption and can be a good solution for mobile communication systems. In this paper, we propose an IR-HARQ scheme based on dual-diagonal parity-type block LDPC codes in which we define a transmission priority of coded bits and propose the sub-packet construction rule. We present the throughput performance of IR-HARQ with various modulation and coding and multi-antenna modes. Consequently, the proposed scheme provides the improvement of system throughput by elaborate link adaptation with CQI information.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.4
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• pp.194-208
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• 2008

In this paper, a multiple-input-multiple-output (MIMO) hybrid-automatic repeat request (HARQ) algorithm with antenna scheduling is proposed. It retransmits the packet using scheduled transmit antennas according to the state of the communication link, instead of retransmitting the packet via the same antennas. As a result, a combination of conventional HARQ systems, viz. chase combining (CC) and incremental redundancy (IR) are used to achieve better performance and lower redundancy. The proposed MIMO-OFDM HARQ system with antenna scheduling is shown to be superior to conventional MIMO HARQ systems, due to its spatial diversity gain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3C
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• pp.195-204
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• 2007

The cyclic redundancy check(CRC) code used to decide retransmission request in hybrid automatic repeat request(HRAQ) system can also be used to stop iterative decoding of turbo code if it is used as an error correcting code(ECC) of HARQ system. Thus a scheme to use CRC code for both iteration stop and repeat request in the HARQ system with turbo code based on the standard of cdma 2000 system is proposed in this paper. At first, the optimum CRC code which has the minimum length without performance degradation due to undetected errors is found. And the most appropriate turbo encoder structure is also suggested. As results, it is shown that at least 32-bit CRC code should be used and a turbo code with 3 constituent encoders is considered to be the most appropriate one.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.212-219
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• 2006

In this paper, a new turbo codes-based hybrid automatic repeat request (TC-HARQ) scheme with segment selective repeat (SSR) is proposed. The main strategy is, upon retransmission, to repeat the data that are most important for the next round of decoding based on the distribution of residual errors after current decoding. The performance in terms of reliability and throughput is analyzed. To adapt to correlated fading channels where an inter-leaver is always employed before transmission, we further modify the SSR strategy so that data having experienced correlated deep fading are selected for retransmission. Finally, this proposed scheme is applied to the wideband code division multiple access (WCDMA) system under frequency selective fading channels. Simulation results demonstrate that in all single and multiple user cases, SSR-based TC-HARQ leads to significant throughput improvement with similar bit error rate (BER) performance as compared to type-I TC-HARQ.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.14-21
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• 2011

In this paper, we propose an efficient symbol mapping method based on LLR (log-likelihood ratio) statistic for HARQ employing CoRe (constellation rearrangement) with 64QAM. The signal constellations for 64QAM with limited number of retransmissions are selected by the proposed mapping rule. Then we determine the transmission order of selected constellations. The proposed scheme reduces the performance deviation between transmit symbols so as to improve the system performance. Through simulation results, the proposed and existing CoRe mapping methods are compared with respect to error rate and throughput in MIMO-OFDM system over fading channel and we confirm the applicability of the proposed scheme in practical wireless communications environment.