• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.223-224
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• 2008

Automatic repeat request (ARQ) protocol is attention for recent years as one protocol for reliable, accurate signal at the destination. However, in almost recently proposed ARQ protocols, the authors only consider advantage about the diversity gain. In this paper, we propose a novel cooperative ARQ protocol with advantage about the bandwidth in which the source sends a number of frames before stopping and worrying about the acknowledgment.

• ETRI Journal
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• 제26권5호
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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.

• Journal of Communications and Networks
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• 제14권5호
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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.

• 한국통신학회논문지
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• 제32권3C호
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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.

• 한국멀티미디어학회논문지
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• 제12권12호
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• pp.1769-1777
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• 2009

With the advent of the ubiquitous technology age, the progress of network technology has enabled a robust sensor communication, not just in cities, but also in poor surroundings such as deserts, polar regions, or underwater environments. In this paper, we propose a Multiple Acknowledgement (MA) technique to replace the conventional Automatic Repeat request (ARQ) technique. The MA mechanism is to send an Ack to many receivers simultaneously. The CH (master, coordinator) of the unit cluster broadcasts a Beacon frame where Ack information of the previously transmitted data is included. This technique can reduce the number of transmissions and overhead significantly. The proposed technique is a scheme improving the efficiency of an underwater sensor network where the uplink data transmission is the mainstream. The Performance of the ARQ, Block Ack, Pervasive Block Ack and the proposed method were compared with one another and analyzed. The proposed method showed significant performance improvement as compared with the ARQ, BA, and PBA in its channel efficiency.

• 전자공학회논문지A
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• 제32A권2호
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• pp.11-18
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• 1995

Error detection in ARQ(Automatic Repeat Request) protocols is very important in wireless data communication systems. The throughput efficiency of ARQ protocols can be improved by dynamically adapting the protocol packet length so that it approaches the optimum value for throuhput efficiency. In this paper, a simple and novel adaptive packet length allocation method is proposed which transmits the packets with variable length by dyanmically estimating the channel codition. The simulation results show that the average of throughput is improved by 315.4% in the stop-and-wait protocol, 41.4% in the go-back-N protocol and 155.9% in the selective repeat protocol respectively. And the throughput performances of adaptive packet length allocation method approximately approach the theoritically optimal throughput performances.

• 한국정보과학회논문지:시스템및이론
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• 제26권5호
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• pp.602-608
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• 1999

멀티미디어 서비스를 제공하는 미래의 이동통신 시스템에서는 데이터의 신뢰성 있는 전송을 위해 물리 계층에서 제공하는 프레임 에러율을 감소시켜야한다. 이를 위해 라디오링크프로토콜(RLP : radio link protocol) 계층에서는 ARQ(automatic repeat request)기법을 사용한다. 본 논문에서는 멀티미디어 서비스를 제공하는 차세대 이동통신 시스템에 적용될수 있는 새로운 SR(Selective repeat) ARQ 기법을 제안하고 그 성능을 분석한다. 제안하는 SR 기법은 재전송이 반복될수록 NAK(negative acknowledge)수와 재전송 프레임수를 지수적으로 (exponentially)증가시킴으로써 프레임손실확률을 감소시킨다. 또한 제안한 SR 기법의 성능을 기존의 전형적인 SR 기법 및 IS-707의 SR 기법과 비교하였다. 비교결과, 제안한 SR 기법은 프레임 손실 확률과 프레임 전송지연 측면에서 다른 두 비교대상 Sr 기법들에 비해 더 나은 성능을 제공한다.

• 대한전자공학회논문지TC
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• 제47권11호
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• pp.19-23
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• 2010

본 논문에서는 MIMO 시스템에서 부분 증분 리던던시 방식 Hybrid ARQ를 위한 결합 기법을 제안한다. 제안 결합 기법은 부분 증분 리던던시 방식 Hybrid ARQ에서 반복 전송되는 정보 심볼들을 위한 심볼 레벨 결합 기법이다. 본 논문에서는 제안 결합 기법이 반복 전송되는 정보 심볼들뿐 아니라 매 전송마다 새로이 전송되는 패리티 심볼들의 검출 성능 또한 향상시킴을 보인다. 모의실험 결과를 통해 제안된 결합 기법이 특히 Zero Forcing 검출 사용 시에 기존의 비트 레벨 결합 기법보다 부분 증분 리던던시 방식 Hybrid ARQ의 성능을 크게 향상시킴을 확인하였다.

• 대한전자공학회논문지TC
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• 제46권5호
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• pp.104-108
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• 2009

본 논문에서는 WCDMA LCR-TDD 시스템에서 ARQ 방식을 적용한 하향 링크 TSTD (Time Switched Transmit Diversity)의 성능을 계산한다. 제안된 TSTD는 ARQ 방식을 적용하여 수신측이 에러체크를 수행한 후 송신측으로 응답신호(ACK or NACK 신호)를 전송하고 전송된 응답신호를 바탕으로 해당 에러 프레임을 재전송한다. 시뮬레이션 결과는 3km/h의 이동국 속도에서 프레임 오류 확률 (Frame Error Rate)이 1%일 때 제안된 ARQ가 적용된 TSTD 기법이 기존의 TSTD보다 약 5.5dB의 성능이득이 있으며, Eb/N0=7dB일 때 약 7%의 수율 개선이 있음을 보여준다.

• 한국통신학회논문지
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• 제33권9C호
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• pp.683-690
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• 2008

반복적인 신뢰 전파 알고리듬을 low-density parity-check(LDPC) 부호에 적용하는 경우 패리티-검사를 이용한 기존 복호 중단 기법은 높은 signal-to-noise ratio(SNR) 영역에서 반복 복호 수를 줄이는 것을 가능케 한다. 그러나 재전송 요청이 빈번한 Hybrid-ARQ(H-ARQ) 시스템에서는 낮은 SNR 영역에 적합한 복호 중단 기법이 없기 때문에 복호에 실패하는 경우 많은 양의 불필요한 반복 복호가 수행된다. 본 논문에서는 결국 복호에 실패하게 될 LDPC 부호 블록들을 복호 초기 단계에서 발견하기 위하여 신뢰 전파 복호에서 임시 부호어의 신드롬 무게를 이용한 중단 기법을 제안한다. 제안된 기법은 H-ARQ 시스템을 위한 LDPC 복호기에서 구현 복잡도의 증가와 성능의 열화 없이도 연산량을 70-80% 감소시킨다.