• Title/Summary/Keyword: relay cooperative

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Multi-Hop Cooperative Communications using Multi-Relays in IEEE 802.11 (IEEE 802.11에서 다중 릴레이를 이용한 멀티홉 방식 협력 무선통신)

  • Lee, Sook-Hyoun;Lee, Tae-Jin
    • Journal of KIISE:Information Networking
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    • v.36 no.6
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    • pp.528-535
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    • 2009
  • This paper proposes a mechanism to increase performance using cooperative communications in IEEE 802.11 environment. Existing algorithms use one relay between a source and a destination, which is a 2 hop relay. The proposed algorithm utilizes more than one relay to complement inefficiency of using one relay. In the proposed mechanism, an AP manages network information (rate), which is used to select relays of a source by the AP. The AP notifies the selected relays to the source and neighbor nodes, and the source transmits data to the relays for cooperative communications. Moreover, relays are given to have an opportunity to send its own data right after relaying the source's data. So relays are compensated for the power to send the source's data and overall throughput is improved.

Adaptive Decode-and-Forward Cooperative Networks with Multiple Relay Nodes

  • Vu, Ha Nguyen;Kong, Hyung-Yun
    • Journal of electromagnetic engineering and science
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    • v.11 no.1
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    • pp.5-10
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    • 2011
  • We propose an adaptive cooperative scheme with a multi-relay node that achieves high bandwidth efficiency and achieves better SEP performance. In the proposed protocol, if the quality of the direct channel is better than that of the all channels from relays to destination, the source will transmit directly to the destination. Otherwise, the source broadcasts the signal and then a potential relay will be chosen to help the source. A re-transmission will also occur if the potential relay cannot be detected. The spectral efficiency is first derived by calculating the probability of each mode, i.e., direct and cooperation transmission. Subsequently, the SEP performance of M-PSK modulation for the scheme is analyzed by considering each event where the source transmits data to the destination. Finally, the obtained analytical results are verified through computer simulations.

Effect of Cooperative and Selection Relaying Schemes on Multiuser Diversity in Downlink Cellular Systems with Relays

  • Kang, Min-Suk;Jung, Bang-Chul;Sung, Dan-Keun
    • Journal of Communications and Networks
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    • v.10 no.2
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    • pp.175-185
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    • 2008
  • In this paper, we investigate the effect of cooperative and selection relaying schemes on multiuser diversity in downlink cellular systems with fixed relay stations (RSs). Each mobile station (MS) is either directly connected to a base station (BS) and/or connected to a relay station. We first derive closed-form solutions or upper-bound of the ergodic and outage capacities of four different downlink data relaying schemes: A direct scheme, a relay scheme, a selection scheme, and a cooperative scheme. The selection scheme selects the best access link between the BS and an MS. For all schemes, the capacity of the BS-RS link is assumed to be always larger than that of RS-MS link. Half-duplex channel use and repetition based relaying schemes are assumed for relaying operations. We also analyze the system capacity in a multiuser diversity environment in which a maximum signal-to-noise ratio (SNR) scheduler is used at a base station. The result shows that the selection scheme outperforms the other three schemes in terms of link ergodic capacity, link outage capacity, and system ergodic capacity. Furthermore, our results show that cooperative and selection diversity techniques limit the performance gain that could have been achieved by the multiuser diversity technique.

Application of Cooperative Transmission Scheme in Railway Wireless Communication System (철도 무선통신내에서 협력전송기법의 응용)

  • Park, Jae Jung;Kim, Yoon Hyun;Kim, Jin Young;Yang, Jae Soo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.12 no.6
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    • pp.251-255
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    • 2012
  • In recent years, according to improvement of various vehicle instruments, railway also has been developed in various fields. As a result, to transmit accurate information to each railway system, the efficient communication system is required. In railway communication system, mitigation of wireless fading is very important. So, in this paper we introduced the cooperative relay channel model and cooperative relay scheme. Also we analyzed and simulated the cooperative relay scheme which is suitable for railway communication systems.

A New Incentive Based Bandwidth Allocation Scheme For Cooperative Non-Orthogonal Multiple Access (협력 비직교 다중 접속 네트워크에서 새로운 인센티브 기반 주파수 할당 기법)

  • Kim, Jong Won;Kim, Sung Wook
    • KIPS Transactions on Computer and Communication Systems
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    • v.10 no.6
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    • pp.173-180
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    • 2021
  • Non Orthogonal Multiple Access (NOMA) is a technology to guarantee the explosively increased Quality of Service(QoS) of users in 5G networks. NOMA can remove the frequent orthogonality in Orthogonal Multiple Access (OMA) while allocating the power differentially to classify user signals. NOMA can guarantee higher communication speed than OMA. However, the NOMA has one disadvantage; it consumes a more energy power when the distance increases. To solve this problem, relay nodes are employed to implement the cooperative NOMA control idea. In a cooperative NOMA network, relay node participations for cooperative communications are essential. In this paper, a new bandwidth allocation scheme is proposed for cooperative NOMA platform. By employing the idea of Vickrey-Clarke-Groves (VCG) mechanism, the proposed scheme can effectively prevent selfishly actions of relay nodes in the cooperative NOMA network. Especially, base stations can pay incentives to relay nodes as much as the contributes of relay nodes. Therefore, the proposed scheme can control the selfish behavior of relay nodes to improve the overall system performance.

Comparative study of OFDMA cooperative relaying methods in Rayleigh fading channel (레일레이 퍼이딩 채널에서 OFDMA 협동 릴레이 방식에 따른 성능비교)

  • Kim, Nam-Soo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.9 no.3
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    • pp.109-115
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    • 2009
  • Recently, the relay communication is focused for the power saving and coverage extension of ad-hoc networks. For the high date rate transmission, it is proposed to adapt OFDMA relays. In this paper, we assume the 2 hop cooperative OFDMA relays between the source and the destination. The performance of 3 different relaying methods are derived and compared. We noticed that the selective OFDMA relaying method has the best performance followed by opportunistic OFDMA relaying and repetition-based OFDMA relaying method under the same threshold mutual information rate.

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Cooperative Hybrid-ARQ Protocols: Unified Frameworks for Protocol Analysis

  • Byun, Il-Mu;Kim, Kwang-Soon
    • ETRI Journal
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    • v.33 no.5
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    • pp.759-769
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    • 2011
  • Cooperative hybrid-automatic repeat request (HARQ) protocols, which can exploit the spatial and temporal diversities, have been widely studied. The efficiency of cooperative HARQ protocols is higher than that of cooperative protocols because retransmissions are only performed when necessary. We classify cooperative HARQ protocols as three decode-and-forward-based HARQ (DF-HARQ) protocols and two amplified-and-forward-based HARQ (AF-HARQ) protocols. To compare these protocols and obtain the optimum parameters, two unified frameworks are developed for protocol analysis. Using the frameworks, we can evaluate and compare the maximum throughput and outage probabilities according to the SNR, the relay location, and the delay constraint. From the analysis we can see that the maximum achievable throughput of the DF-HARQ protocols can be much greater than that of the AF-HARQ protocols due to the incremental redundancy transmission at the relay.

Opportunistic Transmit Cognitive Radio Relay Systems with CSI Delay (CSI 지연을 갖는 기회전송 상황 인지 릴레이 시스템)

  • Kim, Nam-Soo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.10 no.5
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    • pp.39-44
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    • 2010
  • In this paper, we analyze the performance of the cooperative cognitive radio relay system which is adapted the recently highly focused cognitive radio system. The performance comparison is made between the system with and that without the opportunistic transmission relay. Especially the selection combining is considered at the destination for simple implementation. In this case, the effect of the channel state information (CSI) delay, which is caused essentially by the process during the CSI delivery, to the system performance is considered. It is noticed that the performance of the system with the opportunistic relay degrades up to 0.6 dB at a given condition compared to the system without the opportunistic relay. And it is shown that the system performance is more sensitive to the CSI delay compared to the frequency acquisition probability of the cognitive radio relay.

Performance Analysis of Coded Cooperation Protocol with Reactive and Proactive Relay Selection

  • Asaduzzaman, Asaduzzaman;Kong, Hyung-Yun
    • Journal of electromagnetic engineering and science
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    • v.11 no.2
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    • pp.133-142
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    • 2011
  • Coded cooperation that integrates channel coding in cooperative transmission has gained a great deal of interest in wireless relay networks. The performance analysis of coded cooperation protocol with multiple relays is investigated in this paper. We show that the diversity order achieved by the coded cooperation in a multi-relay wireless network is not only dependent on the number of cooperating relays but is also dependent on the code-rate of the system. We derive the code-rate bound, which is required to achieve the full diversity gain of the order of cooperating nodes. The code-rate required to achieve full diversity is a linearly decreasing function of the number of available relays in the network. We show that the instantaneous channel state information (CSI)-based relay selection can effectively alleviate this code-rate bound. Analysis shows that the coded cooperation with instantaneous CSI-based relay selection can achieve the full diversity, for an arbitrary number of relays, with a fixed code-rate. Finally, we develop tight upper bounds for the bit error rate (BER) and frame error rate (FER) of the relay selection based on coded cooperation under a Rayleigh fading environment. The analytical upper bounds are verified with simulation results.

A Pilot-Tone Based Channel Estimation Technique for Cooperative SFBC-OFDM Systems (Cooperative SFBC-OFDM 시스템을 위한 파일럿 톤 기반의 채널 추정 기법)

  • Park, Chang-Hwan;Ko, Yo-Han;Lee, Hee-Soo;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.9C
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    • pp.661-668
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    • 2008
  • In this paper, a channel estimation technique based on pilot tones is proposed for cooperative SFBC-OFDM systems with a STO(Symbol Timing Offset). In a cooperative SFBC-OFDM system, the STO between RS(Relay Station) and MS(Mobile Station) varies depending on the location of MS. Since the STO causes distortion in the form of phase rotation, a channel estimation technique based on linear interpolation with respect to phase and amplitude is proposed for the case of orthogonal pilot allocation. Also, a channel estimation technique is proposed by solving nonlinear equation for the case of pilot structure with orthogonal code. It is shown by computer simulation that the performance of channel estimation can be significantly improved when the proposed techniques are applied to cooperative SFBC-OFDM systems with STO.