• Title/Summary/Keyword: user relay scheme

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Slotted ALOHA Based Greedy Relay Selection in Large-scale Wireless Networks

  • Ouyang, Fengchen;Ge, Jianhua;Gong, Fengkui
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.10
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    • pp.3945-3964
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    • 2015
  • Since the decentralized structure and the blindness of a large-scale wireless network make it difficult to collect the real-time channel state or other information from random distributed relays, a fundamental question is whether it is feasible to perform the relay selection without this knowledge. In this paper, a Slotted ALOHA based Greedy Relay Selection (SAGRS) scheme is presented. The proposed scheme allows the relays satisfying the user's minimum transmission request to compete for selection by randomly accessing the channel through the slotted ALOHA protocol without the need for the information collection procedure. Moreover, a greedy selection mechanism is introduced with which a user can wait for an even better relay when a suitable one is successfully stored. The optimal access probability of a relay is determined through the utilization of the available relay region, a geographical region consisting of all the relays that satisfy the minimum transmission demand of the user. The average number of the selection slots and the failure probability of the scheme are analyzed in this paper. By simulations, the validation and the effectiveness of the SAGRS scheme are confirmed. With a balance between the selection slots and the instantaneous rate of the selected relay, the proposed scheme outperforms other random access selection schemes.

Outage Probability Analysis of Adaptive Two-Way Relay Cooperative Communication (적응형 양방향 중계기 협력 통신의 오수신 확률 분석)

  • Lee, Jin-Hee;Kong, Hyung-Yun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.4
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    • pp.392-398
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    • 2010
  • In this paper, we proposed adaptive two-way relay cooperative communication considering the quality of the user-relay links, and derived outage probability. Network-coding based two-way relay communication can achieve more throughput since it can reduce transmission time compared conventional two-way relay communication. However, Network-coding based two-way relay communication assume that the relay can decode received signal correctly. If relay cannot decode the signal, it leads to error propagation at the relay. In this paper, we proposed adaptive two-way relay cooperative communication scheme. In proposed scheme, the user "A" transmits the signal to relay and another user "B". The relay operates adaptively depend on quality of user-relay links. Simulation result show that proposed scheme has better performance when the quality of the user-relay links are poor. Also it can get diversity order 2.

Transceiver Design Using Local Channel State Information at Relays for A Multi-Relay Multi-User MIMO Network

  • Cho, Young-Min;Yang, Janghoon;Kim, Dong Ku
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.11
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    • pp.2616-2635
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    • 2013
  • In this paper, we propose an iterative transceiver design in a multi-relay multi-user multiple-input multiple-output (MIMO) system. The design criterion is to minimize sum mean squared error (SMSE) under relay sum power constraint (RSPC) where only local channel state information (CSI)s are available at relays. Local CSI at a relay is defined as the CSI of the channel between BS and the relay in the $1^{st}$ hop link, and the CSI of the channel between the relay and all users in the $2^{nd}$ hop link. Exploiting BS transmitter structure which is concatenated with block diagonalization (BD) precoder, each relay's precoder can be determined using local CSI at the relay. The proposed scheme is based on sequential iteration of two stages; stage 1 determines BS transmitter and relay precoders jointly with SMSE duality, and stage 2 determines user receivers. We verify that the proposed scheme outperforms simple amplify-and-forward (SAF), minimum mean squared error (MMSE) relay, and an existing good scheme of [13] in terms of both SMSE and sum-rate performances.

The Partial Full Duplex Relay Scheme for Cell ID Detection of Type 1 Relay in 3GPP LTE-Advanced System (3GPP LTE-Advanced 시스템에서 Type 1 relay의 셀 ID 검출을 위한 부분 전이중 relay 기법)

  • Min, Young-Il;Jang, Jun-Hee;Choi, Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.6A
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    • pp.558-567
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    • 2011
  • In this paper, we propose a partial full duplex relay scheme for 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution)-Advanced system using a Type 1 relay. The Type 1 relay as inband relay is prohibited to transmit and receive simultaneously because of self-interference. Therefore, the Type 1 relay cannot receive synchronization signals which are transmitted to eNB. To overcoming this problem, we propose the partial full duplex relay scheme which transmits to R-UE (Relay-User Equipment) and receives from eNB (evolved NodeB) simultaneously when eNB and the Type 1 relay transmit subframes which have synchronization signals. Additionally, for solving self-interference, the Type 1 relay transmitter and receiver antennas are sufficiently sufficiently isolated and self-interference cancellation is applied for the self-interference signal from the relay transmitter. Thus, the partial full duplex relay scheme can receive synchronization signals from eNB and solve the problems of conventional solutions and we propose the partial channel estimation scheme for partial full duplex relay scheme using SCI. By extensive computer simulation, we verify that the partial full duplex relay scheme is attractive and suitable for the Type 1 relay system.

Power Allocation and Performance Analysis for the Secondary User under Primary Outage Constraint in Cognitive Relay Network (Cognitive Relay 네트워크에서 일차 사용자의 Outage 제약 조건 하에서의 이차 사용자의 파워 할당 기법 및 성능 분석)

  • Kim, Hyung-Jong;Hong, Dae-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.49 no.8
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    • pp.46-51
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    • 2012
  • In this paper, we investigate the power allocation for cognitive relay networks. Cognitive relay networks offer not only increasing spectral efficiency by spectrum sharing but also extending the coverage through the use of relays. For spectrum sharing, conventional works have assumed that secondary users know perfect channel information between the secondary and primary users. However, this channel information may be outdated at the secondary user because of the time-varying properties or feedback latency from the primary user. This causes the violation for interference constraint, and the secondary user cannot share the spectrum of the primary after all. To overcome this problem, we propose the power allocation scheme for the secondary user under the allowable primary user's outage probability constraint. Since the proposed power allocation scheme does not use the instantaneous channel information, the secondary users have lower feedback burden. In addition, the proposed scheme is also robust to the outdated channel environment.

Improvement of Channel Efficiency in Mobile Communications by User Relay Scheme

  • JIA, Zhongning;MUTSUURA, Kouichi;AKIZUKI, Osamu;CHIN, YoonTze;HANDA, Shiro;OSHITA, Shinjiro
    • Proceedings of the IEEK Conference
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    • 2002.07c
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    • pp.1447-1450
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    • 2002
  • In this paper, we propose a new access method named UR (Use. Relay) scheme to improve the channel efficiency in mobile communications. In UR scheme, packets of a data terminal that do not demand real time communications are relayed by other terminals during their inactive periods, which ue communicating with the base station through a fixed channel at that time. Simulation results show that with UR scheme, the blocking probability md the throughput are improved considerably with an allowable increase in the average delay.

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Adaptive Power Control Strategy based on Spectrum Sensing for Cognitive Relay Networks (CR 넷워크를 위한 주파수 감지에 기번한 적응적인 전력 제어 전략)

  • HU, SIYUAN;Joe, Inwhee
    • Proceedings of the Korea Information Processing Society Conference
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    • 2019.05a
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    • pp.82-85
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    • 2019
  • An adaptive power control scheme is proposed for the cognitive relay networks with joint overlay and underlay spectrum sharing model. The transmit power of the secondary user is adjusted adaptively according to the spectrum sensing results and the interference channel condition. The outage probability of the secondary user is compared by Monte - Carlo simulations between the fixed power control scheme and pure overlay or underlay spectrum sharing schemes. The results show that, by employing the adaptive power control strategy, the interference probability of the secondary user to the primary user is decreased by 70 % ~ 80 % under the same outage probability. Also, the outage probability of the secondary user is reduced by 1 ~ 2 orders of magnitude under the same interference probability. Thus, the performance of the spectrum sharing is improved effectively.

Network-Coding Based Two-way Relay Communication Using Adaptive Modulation Sheme (적응형 변조 기법을 이용한 네트워크 부호화 기반 양방향 중계 통신)

  • Lee, Jin-Hee;Kong, Hyung-Yun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.10 no.5
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    • pp.147-151
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    • 2010
  • In this paper, we propose network-coding based two-way relay communication using adaptive modulation scheme for satisfying relay QoS(Quality of Service) according to channel environment between user and relay. Two-way relay communication is bidirectional cooperative communication that users exchange own signal with help of relay. Network-coding based two-way relay communication can achieve high throughput compared to conventional scheme through reducing time slots. we propose adaptive M-QAM modulation scheme in network-coding based two-way relay communication for satisfying QoS of relay. Simulation result shows that the proposed scheme satisfies goal QoS of system.

Power Allocation Framework for OFDMA-based Decode-and-Forward Cellular Relay Networks

  • Farazmand, Yalda;Alfa, Attahiru S.
    • Journal of Communications and Networks
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    • v.16 no.5
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    • pp.559-567
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    • 2014
  • In this paper, a framework for power allocation of downlink transmissions in orthogonal frequency division multiple access-based decode-and-forward cellular relay networks is investigated. We consider a system with a single base station communicating with multiple users assisted by multiple relays. The relays have limited power which must be divided among the users they support in order to maximize the data rate of the whole network. Advanced power allocation schemes are crucial for such networks. The optimal relay power allocation which maximizes the data rate is proposed as an upper bound, by finding the optimal power requirement for each user based on knapsack problem formulation. Then by considering the fairness, a new relay power allocation scheme, called weighted-based scheme, is proposed. Finally, an efficient power reallocation scheme is proposed to efficiently utilize the power and improve the data rate of the network. Simulation results demonstrate that the proposed power allocation schemes can significantly improve the data rate of the network compared to the traditional scheme.

A Positioning Algorithm Using Virtual Reference for Accuracy Improvement in Relay-Based Navigation System (중계 기반 항법시스템에서 위치정확도 향상을 위한 가상 기준점 활용 측위 알고리즘)

  • Lee, Kyuman;Lim, Jaesung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.10
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    • pp.2102-2112
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    • 2015
  • In this paper, we propose a new positioning scheme for accuracy improvement of Relay-based Navigation System. The conventional relay-based system occurs larger vertical error than horizontal one due to structural characteristics that positioning references are located toward same direction and a location of user is estimated by triangulation technique. In the proposed positioning scheme, the user position is reestimated using an additional virtual reference which is generated based on position information of reference stations in navigation signals and estimated initial user position. The nearest reference station from the estimated user position is selected as a virtual reference to minimize the effect of geometrical factor. The vertical error decreases by using reference points on multi planes, therefore, accurate positioning is possible than the conventional scheme. We demonstrated that the accuracy of a user is improved through simulation results.