Auto Repeat Request Research Articles

Performance Analysis of Total Power Consumption in Linear Multi-hop Networks

A multi-hop network transmits the data packets through some relay nodes. In the case of equidistant transmission, it can achieve lower transmission power than a single-hop network. On the other hand, the relay nodes also have their own power consumption that does not contribute to transmission. Therefore, the total power consumption, which are the transmission power of the relay nodes and their own power consumption, can be more than that of the direct communications in the case of numbers of relay nodes and values of power consumption. In this paper, we derive theoretical expression of total power consumption with ARQ (auto repeat request) for packetized transmitted data for linear topology multi-hop networks under path loss and shadowing environments. Moreover, we consider the maximum hops which is better than direct communications in total power consumptions and the optimum hops which minimizes them and evaluate their performance using numerical calculation.

A Model-based Scalable Reliable Multicast Transport Protocol for Satellite Networks

In this paper, we design a new scalable reliable multicast transport protocol for satellite networks (RMT). This paper is the extensions of paper in [18]. The proposed protocoldoes not require inspection and/or interception of packets at intermediate nodes. The protocol would not require anymodification of satellites, which could be bent-pipe satellites or onboard processing satellites. The proposed protocol is divided in 2 parts: error control part and congestion control part. In error control part, we intend to solve feedback implosion and improve scalability by using a new hybrid of ARQ (Auto Repeat Request) and adaptive forward error correction (AFEC). The AFEC algorithm adapts proactive redundancy levels following the number of receivers and average packet loss rate. This leads to a number of transmissions and the number of feedback signals are virtually independent of the number of receivers. Therefore, wireless link utilization used by the proposed protocol is virtually independent of the number of multicast receivers. In congestion control part, the proposed protocol employs a new window-based congestion control scheme, which is optimized for satellite networks. To be fair to the other traffics, the congestion control mimics congestion control in the wellknown Transmission Control Protocol (TCP) which relies on “packet conservation” principle. To reduce feedback implosion, only a few receivers, ACKers, are selected to report the receiving status. In addition, in order to avoid “drop-to-zero” problem, we use a new simple wireless loss filter algorithm. This loss filter algorithm significantly reduces the probability of the congestion window size to be unnecessarily reduced because of common wireless losses. Furthermore, to improve achievable throughput, we employ slow start threshold adaptation based on estimated bandwidth. The congestion control also deals with variations in network conditions by dynamically electing ACKers.

Cross Layer를 이용한 Hybrid ARQ System 분석

High quality and high speed multimedia services will be required in the next generation mobile communications. To satisfy these services, powerful error correction techniques are used. ARQ(Auto Repeat Request) techniques, aspects of the throughput, and FEC(Forward Error Correct) techniques have disadvantages in terms of reliability. H-ARQ(Hybrid Auto Repeat Request) systems have been studied extensively as a solution of these disadvantages. In this paper introduce double layer coding and H-ARQ type, proposed H-ARQ system using double layer coding methods. Simulate BER performance and throughput. And we suggest that according to channel condition suitable H-ARQ type.

Performance of a VSF-OFCDM system using a symbol relocated scheme during retransmission

A symbol-relocated (SR) scheme has been proposed for variable spreading factor orthogonal frequency code-division multiplex systems to achieve frequency diversity during retransmission. The performance has been evaluated for two combining schemes of hybrid auto repeat request, namely chase combining and incremental redundancy. The results show that the proposed SR scheme achieves significant improvement in terms of system throughput over conventional schemes. This effect is more significant for chase combining because the rotated mechanism is more effective when the same packet is transmitted during the retransmission. It is also found that the SR scheme is not sensitive to Doppler frequency variation, which makes it an attractive candidate for fast-fading channels. Further investigation also suggests the suitability of an SR scheme for smaller spreading factors (in the frequency domain) and larger coding rates.