Beamforming in Two-Way Fixed Gain Amplify-and-Forward Relay Systems with CCI

We analyze the outage performance of a two-way fixed gain amplify-and-forward (AF) relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Assuming CCI at the relay, we derive the exact individual user outage probability in closed-form. Additionally, while neglecting CCI, we also investigate the system outage probability of the considered network, which is declared if any of the two users is in transmission outage. Our results indicate that in this system, the position of the relay plays an important role in determining the user as well as the system outage probability via such parameters as signal-to-noise imbalance, antenna configuration, spatial correlation, and CCI power. To render further insights into the effect of antenna correlation and CCI on the diversity and array gains, an asymptotic expression which tightly converges to exact results is also derived.Comment: Accepted for presentation on IEEE International Conference on Communications (ICC 2012), Ottawa, Canada, June 201

Adaptive Modulation Scheme with Cooperative Diversity in Wireless Systems

A common technique that is conjointly wide utilized in communication systems are that the adjustive Modulation (AM). During this technique the foremost applicable sort of modulation is chosen additionally to size of the constellation betting on the Signal to Noise magnitude relation (SNR) measured at the receiver aspect. AM technique is utilized at intervals the systems of cooperative diversity so as to get outturn sweetening from SNR gain. The variety is additionally thought-about another common technique that is utilized in mitigating the attenuation impact. Time diversity strategies are not able to use for channels of frequency non-selective and slow attenuation varieties. The AM and cooperative diversity techniques, that area unit thought-about two common and deployed algorithms in up the wireless communication performance. This project investigated many studies that were introduced within the literature involving these two topics. The planned ways, concepts, outcomes and regarded conditions throughout the implementation or derivation were conjointly mentioned and compared. Every of the studies achieved a transparent improvement inside the wireless communication system upon considering many criteria, such as: outturn, SNR, SE and BER

Outage Probability of Dual-Hop Selective AF With Randomly Distributed and Fixed Interferers

The outage probability performance of a dual-hop amplify-and-forward selective relaying system with global relay selection is analyzed for Nakagami-$m$ fading channels in the presence of multiple interferers at both the relays and the destination. Two different cases are considered. In the first case, the interferers are assumed to have random number and locations. Outage probability using the generalized Gamma approximation (GGA) in the form of one-dimensional integral is derived. In the second case, the interferers are assumed to have fixed number and locations. Exact outage probability in the form of one-dimensional integral is derived. For both cases, closed-form expressions of lower bounds and asymptotic expressions for high signal-to-interference-plus-noise ratio are also provided. Simplified closed-form expressions of outage probability for special cases (e.g., dominant interferences, i.i.d. interferers, Rayleigh distributed signals) are studied. Numerical results are presented to show the accuracy of our analysis by examining the effects of the number and locations of interferers on the outage performances of both AF systems with random and fixed interferers.Comment: 35 pages, 11 figures, accepted with minor revisions for publication as a regular paper in the IEEE Transactions on Vehicular Technology on 21/09/201

Performance Analysis of Multi-Antenna Hybrid Satellite-Terrestrial Relay Networks in the Presence of Interference

Abstract—The integration of cooperative transmission into satellite networks is regarded as an effective strategy to increase the energy efficiency as well as the coverage of satellite communications. This paper investigates the performance of an amplifyand-forward (AF) hybrid satellite-terrestrial relay network (HSTRN), where the links of the two hops undergo Shadowed- Rician andRayleigh fadingdistributions, respectively.By assuming that a single antenna relay is used to assist the signal transmission between the multi-antenna satellite and multi-antenna mobile terminal, and multiple interferers corrupt both the relay and destination, we first obtain the equivalent end-to-end signal-to-interference-plus-noise ratio (SINR) of the system. Then, an approximate yet very accurate closed-form expression for the ergodic capacity of the HSTRN is derived. The analytical lower bound expressions are also obtained to efficiently evaluate the outage probability (OP) and average symbol error rate (ASER) of the system. Furthermore, the asymptotic OP and ASER expressions are developed at high signal-to-noise ratio (SNR) to reveal the achievable diversity order and array gain of the considered HSTRN. Finally, simulation results are provided to validate of the analytical results, and show the impact of various parameters on the system performance

Outage Probability Analysis of Dual Hop Relay Networks in Presence of Interference

Cooperative relaying improves the performance of wireless networks by forming a network of multiple independent virtual sources transmitting the same information as the source node. However, interference induced in the network reduces the performance of cooperative communications. In this work the statistical properties, the cumulative distribution function (CDF) and the probability density function (PDF) for a basic dual hop cooperative relay network with an arbitrary number of interferers over Rayleigh fading channels are derived. Two system models are considered: in the first system model, the interferers are only at the relay node; and in the second system model, interferers are both at the relay and the destination. This work is further extended to Nakagami-m faded interfering channels. Simulation results are presented on outage probability performance to verify the theoretical analysis

동일채널간섭이 존재하는 페이딩채널에서 무선 중계 네트워크의 성능 분석

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 8. 이재홍.무선 중계 기술은 차세대 통신 시스템에서 요구되는 높은 서비스 품질/데이터 전송률 달성을 위한 가장 중요한 기술 중 하나이다. 중계 기술이 갖고 있는 다양한 장점으로 인해 중계 기술은 지금까지 IEEE 802.16j 및 3GPP LTE-Advanced 등의 무선통신 시스템 표준에 반영되기도 하였다. 그러나 실질적인 무선 중계 네트워크의 프로토콜 개발을 위해서는 여전히 해결해야하는 많은 문제들이 있다. 특히 대형셀과 소형셀이 동시에 존재하는 중첩셀 네트워크에서 이웃한 대형셀 및 소형셀로부터 받게되는 동일채널간섭은 차세대 무선통신 시스템의 성능을 저하시키는 주요 제한 요소인데 아직 연구가 미흡한 실정이다. 또한 전이중 중계 네트워크에서 단말기의 송신안테나에서 수신안테나로 들어오는 동일채널 루프간섭은 전이중 중계 네트워크의 성능을 결정하는 중요한 요소로 추가적인 연구가 필요한 실정이다. 본 논문에서는 동일채널간섭을 포함한 양방향 중계 네트워크, 동일채널 루프간섭을 포함한 양방향 전이중 중계 네트워크 및 무선 인지 다중 홉 네트워크의 성능을 분석하며, 주요한 연구결과는 다음과 같다. 첫째, 셀룰러 환경에서 높은 주파수 재사용율로 인해 발생한 동일채널간섭이 존재하는 양방향 중계 네트워크의 성능을 분석한다. 이때 임의의 한 사용자가 불능 사건이 발생하는 시나리오(개별 사용자 불능), 전체 사용자가 동시에 불능 사건이 발생한 시나리오(전체 사용자 불능)의 두 가지에 대해 성능을 분석한다. 여기에서 각 시나리오에 대하여 개별 사용자 불능 확률 및 전체 사용자 불능 확률을 폐형으로 유도한다. 모의실험을 통해 얻어진 불능 확률이 유도한 불능 확률 값과 일치함을 확인한다. 또한 동일채널간섭을 발생하는 인접 셀의 사용자가 늘어날수록 개별 사용자 불능 확률 및 전체 사용자 불능 확률이 증가함을 확인한다. 둘째, 동일채널 루프간섭이 존재하는 전이중 양방향 중계 네트워크를 연구한다. 여기에서 두 전이중 방식의 사용자들이 전이중 방식의 중계기를 이용하여 서로 신호를 교환한다. 이때 각 단말기들은 자신의 수신 신호에서 루프간섭 신호의 추정치를 제거한다. 단말기들이 채널 상태 정보를 정확하게 혹은 부정확하게 알고 있는 경우에 전이중 양방향 중계 네트워크의 불능 확률을 정확한 적분 표현 및 근사적 폐형 표현으로 유도한다. 모의실험을 통해 얻어지 결과가 유도한 수식과 일치함을 확인한다. 셋째, 대형셀과 소형셀이 동시에 존재하는 중첩셀 네트워크를 연구한다. 특히 인접 대형셀 및 소형셀에서 발생한 동일채널간섭이 존재하는 무선 인지 기반 다중 홉 소형셀 네트워크의 불능 확률을 분석한다. 모의실험을 통해 얻어진 불능 확률을 통해 유도한 불능 확률을 검증한다. 유도한 불능 확률 값과 모의실험을 통해 얻어진 불능 확률 값이 일치함을 확인한다. 대형셀의 수가 증가할수록 불능 확률이 증가함을 확인한다.Wireless relay technology is one of the most promising technologies for the future communication systems which provide higher data rate and better quality of service (QoS). Thanks to its advantages, it has been adopted in wireless standards such as IEEE 802.16j and 3GPP LTE-Advanced. However, there are still many challenges to be addressed for developing protocols of wireless relay networks. Especially, in multitier cellular networks (e.g. small cell underlaid macro cell), cochannel interference from multiple interferers in other macro cells and neighboring small cells is one of the major limiting factors due to frequency reuse for high spectrum utilization. In the full-duplex relay networks, cochannel loop interference from a transmit antenna to a receive antenna of a terminal is an important limiting factor to determine the performance of full-duplex relay networks. The dissertation consists of three main results. First, we analyze the performance of a two-way relay network experiencing cochannel interference from multiple interferers due to frequency reuse in cellular networks. In the two-way relay network, two users exchange their information with the help of an amplify-and-forward (AF) relay. We discuss two different scenarios: Outages are declared individually for each user (individual outage) and an outage is declared simultaneously for all users (common outage). We derive the closed-form expression for the individual outage probability and the exact integral expression for the common outage probability of the two-way relay network with multiple interferers. The validity of our analytical results is verified by a comparison with simulation results. It is shown that the analytical results perfectly match the simulation results of the individual and common outage probabilities. Also, it is shown that the individual and common outage probabilities increase as the number of interferers increases. Second, we investigate two-way full-duplex relaying with cochannel loop interference. In the two-way full-duplex relaying, two full-duplex users exchange data with each other via a full-duplex relay and each node attempts to subtract the estimate of the cochannel loop interference from its received signal. We derive the exact integral and approximate closed-form expressions for the outage probability of the two-way full-duplex relaying in case of perfect and imperfect channel state information. Monte Carlo simulation verifies the validity of analytical results. Third, we investigate a cognitive small cell network which is overlaid with a cellular network. We analyze the performance of the cognitive small cell network in the presence of cochannel interference from the cellular network. Analytical results are verified by Monte Carlo simulations. It is shown that the analytical results are in complete agreement with simulation results. It is shown that the outage probability increases as the number of cells increases.Abstract 1 Introduction 1.1 Background and Related Works 1.1.1 Relay Technology 1.1.2 Cognitive Radio 1.2 Outline of Dissertation 1.3 Notations 2 Two-Way Relay Network with Cochannel Interference 2.1 System Model 2.2 Outage Probability Derivation 2.2.1 Moment Generating Functions 2.2.2 Individual Outage Probability 2.2.3 Common Outage Probability 2.3 Numerical Results 2.4 Summary 3 Two-Way Full-Duplex Relaying with Cochannel Loop Interference 3.1 System Model 3.2 Outage Probability Derivation 3.2.1 Signal-to-Interference-plus-Noise Ratio 3.2.2 Cumulative Density Function 3.2.3 Outage Probability 3.3 Numerical Results 3.4 Summary 4 Multi-hop Cognitive Radio Network with Cochannel Interference 4.1 System Model 4.2 Outage Probability Derivation 4.2.1 Signal-to-Interference-plus-Noise Ratio 4.2.2 Cumulative Density Function 4.2.3 Outage Probability 4.3 Numerical Results 4.4 Summary 5 Conclusions 5.1 Summary 5.2 Future Works Bibliography Korean Abstract AcknowledgmentsDocto