Half-Duplex Relaying Strategy Suitable for a Relay with Mobility

( Inho Hwang ),( Jeong Woo Lee ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.1

We propose a new time-division half-duplex estimate-and-forward (EF) relaying strategy suitable for a relay with mobility. We reconfigure EF relaying to guarantee a strong relay-destination link which is required to achieve a high rate using EF relaying. Based on the reconfigured model, we optimize the relaying strategy to attain a high rate irrespective of the relay position with preserving the total transmit bandwidth and energy. The proposed relaying strategy achieves high communication reliability for any relay position, which differs from conventional EF and decode-and-forward (DF) relaying schemes.

OFDMA 기반 Relay 시스템에서 Relay의 Capability에 따른 VoIP 성능 분석

안성보(Sungbo Ahn),최호영(Hoyoung Choi),홍대형(Daehyoung Hong),임재찬(Jaechan Lim) 한국통신학회 2009 韓國通信學會論文誌 Vol.34 No.3

본 논문에서는 OFDMA 기반 relay 시스템에서 사용자에게 VoIP 서비스를 제공할 경우, relay station (RS)의 capability에 따른 시스템의 성능 차이를 분석하였다. Relay 시스템은, relay의 스케줄링 수행 여부에 따라 mid-capability (MC)와 high-capability (HC) relay를 적용한 시스템으로 구분할 수 있다. HC relay를 적용한 시스템의 경우, base station (BS) 뿐만 아니라 RS도 직접 스케줄링을 수행한다. 반면에 MC relay를 적용한 시스템의 경우, 각 RS로부터 mobile station (MS) 들의 수신 SINR, 발생 traffic양 등의 정보를 BS에서 수집하여, BS가 단독으로 스케줄링을 수행한다. 이 경우 MS의 정보 수집 및 RS로의 스케줄링 정보 전달을 위해 control 오버헤드는 커지지만, BS가 모든 MS에 대한 정보를 알고 있으므로 효율적인 자원 할당 및 스케줄링이 가능하다. 따라서 RS의 capability에 따라 전체 시스템의 성능이 달라질 수 있고, 이에 대한 분석이 필요하다. 본 논문에서는 모의 실험을 통해 VoIP traffic 환경에서 RS의 capability에 따른 평균 packet delay, good packet ratio, cell goodput 등을 도출하였다. 선정한 VoIP 성능 지표에 의하면, MC relay를 적용한 시스템이 HC relay를 적용한 시스템에 비해 성능이 우수함을 확인하였다. In this paper, we evaluate the performance of VoIP in OFDMA-based relay systems with various capabilities of relays. We classify relays according to capability as “mid-capability (MC)” and “high-capability (HC)” relay. In system with HC relays, not only base station (BS) but also relay station (RS) performs scheduling at its own, whereas only BS performs scheduling in system with MC relays using the information reported by MS (i.e. the received signal-to-interference-plus-noise ratio (SINR) of mobile station (MS), the amount of MS traffic, etc). In system with MC relays, the controling overhead of BS is larger than that of system with HC relays. However, since BS has all MS information, efficient resource allocation and scheduling is possible. We derived the “average packet delay,” “good packet ratio,” and “cell goodput” in a VoIP environment. The simulation results demonstrate that the system with MC relays has better VoIP performance over that with HC relays.

Outage Capacity Analysis for Cooperative DF and AF Relaying in Dissimilar Rayleigh Fading Channels

스레스타,장경희,Shrestha, Suchitra,Chang, Kyung-Hi The Korea Institute of Information and Commucation 2008 韓國通信學會論文誌 Vol.33 No.4A

Cooperative relaying permits one or more relay to transmit a signal from the source to the destination, thereby increasing network coverage and spectral efficiency. The performance of cooperative relaying is often measured as outage probability. However, appropriate measure for the channel quality is outage capacity. Although the outage probability for cooperative relaying protocol has been analyzed before, very little research has been addressed for the outage capacity. This paper is the first of its kind to derive a closed-form analytical solution of outage capacity using fixed decode and forward relaying and amplify and forward relaying in dissimilar Rayleigh fading channels, considering channel coefficients known to the receiver side. The analytical results show a tradeoff between the SNR and the number of relays for specific outage capacity. A comparison between decode and forward relaying and amplify and forward relaying shows that decode and forward relaying outperforms amplify and forward relaying for a large number of relays.

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

( Young-min Cho ),( Janghoon Yang ),( Dong Ku Kim ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.11

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.

Optimized Relay Selection and Power Allocation by an Exclusive Method in Multi-Relay AF Cooperative Networks

( Jianrong Bao ),( Bin Jiang ),( Chao Liu ),( Xianyang Jiang ),( Minhong Sun ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.7

In a single-source and multi-relay amplify-forward (AF) cooperative network, the outage probability and the power allocation are two key factors to influence the performance of an entire system. In this paper, an optimized AF relay selection by an exclusive method and near optimal power allocation (NOPA) is proposed for both good outage probability and power efficiency. Given the same power at the source and the relay nodes, a threshold for selecting the relay nodes is deduced and employed to minimize the average outage probability. It mainly excludes the relay nodes with much higher thresholds over the aforementioned threshold and thus the remainders of the relay nodes participate in cooperative forwarding efficiently. So the proposed scheme can improve the utility of the resources in the cooperative multi-relay system, as well as reduce the computational complexity. In addition, based on the proposed scheme, a NOPA is also suggested to approach sub-optimal power efficiency with low complexity. Simulation results show that the proposed scheme obtains about 2.1dB and 5.8dB performance gain at outage probability of 10^-4, when compared with the all-relay-forward (6 participated relays) and the single-relay-forward schemes. Furthermore, it obtains the minimum outage probability among all selective relay schemes with the same number of the relays. Meanwhile, it approaches closely to the optimal exhaustive scheme, thus reduce much complexity. Moreover, the proposed NOPA scheme achieves better outage probability than those of the equal power allocation schemes. Therefore, the proposed scheme can obtain good outage probability, low computational complexity and high power efficiency, which makes it pragmatic efficiently in the single-source and multi-relay AF based cooperative networks.

Performance Evaluation of Vehicle-mounted Mobile Relay in Next Generation Cellular Networks

( Keunhang Heo ),( Hyunsik Kang ),( Un-chul Moon ),( Jungryun Lee ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.5

Compared to nomadic and fixed relay stations, vehicle-mounted mobile relay stations show different characteristics caused by the time-variant topology, due to their mobility. Especially, a relay mounted in a vehicle is differentiated from nomadic or fixed relay by the restricted distance between the relay and associated mobile station and the variable density of relay deployment in a cell. In this paper, we identify the characteristics of vehicle-mounted mobile relay stations and provide some parameters that highly influence the performance of vehicle-mounted relay. Through simulation, we measure the effect of relay density, zone ratio, relay transmission power, and frame transmission mode on the performance of vehicle-mounted relay. The results show that the performance of vehicle-mounted relay is highly susceptible to the above vehicle-mounted relay-specific parameters.

Opportunistic Multiple Relay Selection for Two-Way Relay Networks with Outdated Channel State Information

( Sijia Lou ),( Longxiang Yang ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.2

Outdated Channel State Information (CSI) was proved to have negative effect on performance in two-way relay networks. The diversity order of widely used opportunistic relay selection (ORS) was degraded to unity in networks with outdated CSI. This paper proposed a multiple relay selection scheme for amplify-and-forward (AF) based two-way relay networks (TWRN) with outdated CSI. In this scheme, two sources exchange information through more than one relays. We firstly select N best relays out of all candidate relays with respect to signal-noise ratio (SNR). Then, the ratios of the SNRs on the rest of the candidate relays to that of the Nth highest SNR are tested against a normalized threshold μ∈[0, 1], and only those relays passing this test are selected in addition to the N best relays. Expressions of outage probability, average bit error rate (BER) and ergodic channel capacity were obtained in closed-form for the proposed scheme. Numerical results and Simulations verified our theoretical analyses, and showed that the proposed scheme had significant gains comparing with conventional ORS.

Outage Capacity Analysis for Cooperative DF and AF Relaying in Dissimilar Rayleigh Fading Channels

Suchitra Shrestha(스레스타),KyungHi Chang(장경희) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.4A

Cooperative relaying permits one or more relay to transmit a signal from the source to the destination, thereby increasing network coverage and spectral efficiency. The performance of cooperative relaying is often measured as outage probability. However, appropriate measure for the channel quality is outage capacity. Although the outage probability for cooperative relaying protocol has been analyzed before, very little research has been addressed for the outage capacity. This paper is the first of its kind to derive a closed-form analytical solution of outage capacity using fixed decode and forward relaying and amplify and forward relaying in dissimilar Rayleigh fading channels, considering channel coefficients known to the receiver side. The analytical results show a tradeoff between the SNR and the number of relays for specific outage capacity. A comparison between decode and forward relaying and amplify and forward relaying shows that decode and forward relaying outperforms amplify and forward relaying for a large number of relays.

MC-CDMA 시스템에 대한 주파수 효율적인 CDD-DF-Relay 기법에 관한 연구

고균병(Kyun-Byoung Ko),우중재(Choong-Chae Woo) 大韓電子工學會 2011 電子工學會論文誌-TC (Telecommunications) Vol.48 No.5

본 논문에서는 CDD-DF-Relay 기법을 MC-CDMA 시스템에 대해 제안하고 제안된 기법의 성능을 다중경로 레일리 페이딩 채널에서 검증한다. 일반적인 DF-Relay 기법에서는 모든 Relay들이 직교 채널들로 신호를 전송하여야 하기 때문에 그 장점 즉, 다이버시티 이득은 주파수 효율의 저하로부터 얻어진다고 할 수 있다. 따라서 이러한 주파수 효율 저하의 문제점을 해결하기 위하여 본 논문에서는 CDD 기법을 각 Relay 노드에 적용하여 모든 Relay가 하나의 채널만을 사용하도록 한다. 이는 Destination에서 바라본 하나의 R-D 링크 채널의 Delay Spread가 길어지는 효과를 갖는다. 즉 Relay 개수의 증가에 따라 다중 경로수가 증가됨을 의미하고, 이는 MC-CDMA 시스템에서 주파수 다이버시티 이득으로 해설될 수 있다. 모의실험에서는 일반적인 DF-Relay 기법과 제안된 CDD-DF-Relay 기법의 성능을 비교 분석한다. 이를 통해 제안된 기법이 주파수 효율의 저하없이 협력 다이버시디 이득을 획득할 수 있음을 확인하였다. In this paper, CDD(Cyclic Delay Diversity)-DF(Decode-and-Forward)-Relay scheme is proposed for MC-CDMA(Multicarrier-Code Division Multiple Access) systems over multipath Rayleigh fading channels. The advantages of general DF schemes come at the expense of the spectral efficiency since the source and all the relays must transmit on orthogonal channels. In order to mitigate this disadvantage of general DF schemes, we have applied CDD techniques to each relays so that all the relays can transmit on single channel. It means that all R-D link channels can be considered as a single channel which is widely delay spread. Namely, it causes the increasing the number of multipath so that the frequency diversity gain can be achieved in MC-CDMA systems. By simulations, we have compared proposed one with general DF scheme. Therefore, it is confirmed that the proposed one can be a possible solution to achieve cooperative diversity gain without a reduction of spectral efficiency.

Bi-Directional Half-Duplex Relaying Protocols

Kim, Sang-Joon,Devroye, Natasha,Tarokh, Vahid The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.5

The bi-directional relay channel is the natural extension of a three-terminal relay channel where node a transmits to node b with the help of a relay r to allow for two-way communication between nodes a and b. That is, in a bi-directional relay channel, a and b wish to exchange independent messages over a shared channel with the help of a relay r. The rates at which this communication may reliably take place depend on the assumptions made on the relay processing abilities. We overview information theoretic limits of the bi-directional relay channel under a variety of conditions, before focusing on half-duplex nodes in which communication takes place in a number of temporal phases (resulting in protocols), and nodes may forward messages in four manners. The relay-forwarding considered are: Amplify and forward (AF), decode and forward (DF), compress and forward (CF), and mixed forward. The last scheme is a combination of CF in one direction and DF in the other. We derive inner and outer bounds to the capacity region of the bi-directional relay channel for three temporal protocols under these four relaying schemes. The first protocol is a two phase protocol where a and b simultaneously transmit during the first phase and the relay r alone transmits during the second. The second protocol considers sequential transmissions from a and b followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. We provide a comprehensive treatment of protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries.