• Title, Summary, Keyword: Diversity Technique

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Hybrid Diversity-Beamforming Technique for Outage Probability Minimization in Spatially Correlated Channels

  • Kwon, Ho-Joong;Lee, Byeong-Gi
    • Journal of Communications and Networks
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    • v.9 no.3
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    • pp.274-281
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    • 2007
  • In this paper, we present a hybrid multi-antenna technique that can minimize the outage probability by combining the diversity and beamforming techniques. The hybrid technique clusters the transmission antennas into multiple groups and exploit diversity among different groups and beamforming within each group. We analyze the performance of the resulting hybrid technique for an arbitrary correlation among the transmission antennas. Through the performance analysis, we derive a closed-form expression of the outage probability for the hybrid technique. This enables to optimize the antenna grouping for the given spatial correlation. We show through numerical results that the hybrid technique can balance the trade-offs between diversity and beamforming according to the spatial correlation and that the optimally designed hybrid technique yields a much lower outage probability than the diversity or beamforming technique does in partially correlated fading channels.

Improving the Reception Performance of Legacy T-DMB/DAB Receivers in a Single-Frequency Network with Delay Diversity

  • Baek, Myung-Sun;Lee, Yong-Hoon;Hur, Namho;Kim, Kyung-Seok;Lee, Yong-Tae
    • ETRI Journal
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    • v.36 no.2
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    • pp.188-196
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    • 2014
  • This paper describes a simple delay diversity technique for terrestrial digital multimedia broadcasting (T-DMB) and digital audio broadcasting in a single-frequency network (SFN). For the diversity technique, a delay diversity scheme is adopted. In the delay diversity scheme, a non-delayed signal is transmitted in the first antenna, and delayed versions of the signal are transmitted in each additional antenna. For an SFN environment with multiple transmitters, delay diversity can be executed by controlling the emission times of the transmitters. This SFN delay diversity scheme does not require any hardware changes in either the transmitter or receiver, and perfect backward compatibility can be acquired. To evaluate the performance improvement, laboratory tests are executed with various types of commercial T-DMB receivers as well as a measurement receiver. The improvement in the bit error rate performance is evaluated using a measurement receiver, and an improvement of the threshold of visibility value is evaluated for commercial receivers. Test results show that the T-DMB system can obtain diversity gain using the described technique.

Relay-assisted Multiple Access Channel Protocol for Cooperative Diversity

  • Kim, Dong-Hyun;Kim, Gil;Lee, Kwang-Bok
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.1C
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    • pp.1-8
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    • 2009
  • Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.

Performance Analysis or MC / DS CDMA System with Hybrid SC / MRC Diversity over Multi-path Fading Channels (다중경로 페이딩 채널에서 Hybrid SC/MRC 기법이 적용된 MC / DS CDMA 시스템의 성능분석)

  • 김원섭;박진수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.7A
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    • pp.748-755
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    • 2004
  • In this paper, the hybrid SC/MRC technique was applied to the MC/DS-CDMA system in the Nakagami-m multi-path fading environment. The applied scheme was compared with other cases when the MRC technique was applied and then performances were analyzed. The result of analysis showed that the performance of the applied system, whose number of branches (L) for the input diversity of each carrier wave was 3 and かme selected number of branches ( Lc) was 2, was better than that of the MRC technique when the Lc of the MRC technique was 2. The performance of the applied system was lower than that of the MRC technique, then the Lc of the MRC technique was 3. However, as the fading index was lowered, which means the telecommunication environment deteriorated, the performance of the hybrid SC/MRC-(2/3) diversity technique when Lc of MRC technique was 3, was almost the same as that of the MRC technique. The hybrid SC/MRC-(2/3) diversity technique shows a similar performance to that of the MRC technique, when the Lc of the MRC technique was 4. Therefore, it was confirmed that the MC/DS-CDMA system could reduce complexity and achieve similar performance to that of the MRC by applying the hybrid SC/MRC technique, which utilized the advantages of the SC technique and high performance of the MRC scheme, rather than the MRC diversity technique that requires bit synchronization, frequency of fading, and phase synchronization for every diversity branch.

Comparisons of Diversity Techniques for OFDM Systems in Interference-Limited Environments (간섭 제한적인 환경에서의 OFDM 시스템의 다이버시티 기술의 비교)

  • Rim, Min-Joong;Kim, Hong-Seog
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.11A
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    • pp.1043-1052
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    • 2008
  • This paper compares the performances with space time coding and cyclic delay diversity techniques for OFDM systems in interference-limited environments. While a communication system usually use a diversity technique to improve its own performance, it is also necessary to consider the interference effects to other users as well if the system is operated in interference-limited environments. When there is no interference from or to other users, space time coding technique results in better performance than cyclic delay diversity. However, cyclic delay diversity can be better than space time coding if interferences to other users are considered.

Cooperative Diversity Performance Using Duo-Binary Turbo Codes (Duo-Binary 터보 부호를 이용한 협동 다이버시티 성능 분석)

  • Yeo, Sung-Moon;Kim, Soo-Young
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.2
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    • pp.38-45
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    • 2009
  • In this paper, we propose an efficient cooperative diversity technique, which partition the codewords of each mobile and transmit portions of each codeword through independent fading channels using duo-binary turbo codes. A coded diversity technique can achieve high cooperative diversity gain by decoding and transmitting of the re-encoded signal, while this can also cause high performance degradation due to failure of the decoding. In this paper, we introduce various coded diversity technique using duo-binary turbo codes which are defined as channel coding schemes in the IEEE WiMax specification, and also demonstrate performance simulation results with the analysis. We also propose a cooperative diversity technique using rate-compatible duo-binary turbo codes, where user terminals with different parity symbols cooperate each other. Simulation results investigated in this paper reveal that the proposed scheme show high diversity gain at a reasonal SNR range.

Bandwidth-efficient Cooperative Diversity with Rotated Constellations and Its Performance Analysis

  • Lei, Weijia;Xie, Xianzhong;Li, Xiangming
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.4 no.6
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    • pp.989-1005
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    • 2010
  • Cooperative diversity is a technique with which a virtual multiple antenna array is established among the single antenna users of the wireless network to realize space diversity. Signal space diversity (SSD) is a bandwidth-efficient diversity technique, which uses constellation rotation and interleaving techniques to achieve diversity gain. A new cooperative diversity scheme with rotated constellations (RCCD) is proposed in this paper. In this scheme, data are modulated by using a rotated constellation, and the source and the relays transmit different components of the modulated symbols. Since any one of the components contains full information of the symbols, the destination can obtain multiple signals conveying the same information from different users. In this way, space diversity is achieved. The RCCD scheme inherits the advantage of SSD - being bandwidth-efficient but without the delay problem of SSD brought by interleaving. The symbol error rate of the RCCD scheme is analyzed and simulated. The analysis and simulation results show that the RCCD scheme can achieve full diversity order of two when the inter-user channel is good enough, and, with the same bandwidth efficiency, has a better performance than amplify-and-forward and detect-and-forward methods.

Blocking Effect Compensation using Diversity Technique (Diversity기법을 활용한 Blocking영향 보상)

  • Lee, Huikyu
    • Journal of Satellite, Information and Communications
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    • v.12 no.2
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    • pp.38-41
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    • 2017
  • Reception performance in land mobile satellite is decreased by obstacle. It is compensated with Diversity technique. In this paper, performances are analyzed with two type of method Equal Gain Combining(EGC) and Selcetive Combining(SC). To analyze, measured data using On-The-Move(OTM) terminal are used. In conclusion, SC method can increase performance. However, EGC method can improve perforamance only in rural region, but performance are decreased in urban region.

A Novel Transmit Diversity Technique for IS-2000 Systems (IS-2000 시스템을 위한 SS-OTD에 관한 연구)

  • Yoon, Hyun-Goo;Yook Jong-Gwan;Park, Han-Kyu
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.1B
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    • pp.56-65
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    • 2002
  • This paper proposes a novel transmit diversity technique, namely symbol split orthogonal transmit diversity (SS-OTD). In this technique, full path diversity and temporal diversity are achieved by combining orthogonal transmit diversity technique (OTD) technique with the symbol splitting method proposed by Meyer. Its performances is simulated for fundamental channels associated with the forward link of the IS-2000 system, and then compared with those of OTD and space-time spreading (STS). Our proposed method offers a 0.5-7.7dB performance improvement over OTD under various simulation environments and its performance is similar to STS. Moreover, compares with that of STS, the peak-to-average power ratio (PAR) of transmitted signals in SS-OTD is reduced by a maximal 1.35dB, which decreases the complexity of base station RF devices, such as power amplifiers. Thus, SS-OTD is comparable to STS in performance and superior to STS in the cost and efficiency of base station RF devices.

MIMO Ad Hoc Networks: Medium Access Control, Saturation Throughput, and Optimal Hop Distance

  • Hu, Ming;Zhang, Junshan
    • Journal of Communications and Networks
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    • v.6 no.4
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    • pp.317-330
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    • 2004
  • In this paper, we explore the utility of recently discovered multiple-antenna techniques (namely MIMO techniques) for medium access control (MAC) design and routing in mobile ad hoc networks. Specifically, we focus on ad hoc networks where the spatial diversity technique is used to combat fading and achieve robustness in the presence of user mobility. We first examine the impact of spatial diversity on the MAC design, and devise a MIMO MAC protocol accordingly. We then develop analytical methods to characterize the corresponding saturation throughput for MIMO multi-hop networks. Building on the throughout analysis, we study the impact of MIMO MAC on routing. We characterize the optimal hop distance that minimizes the end-to-end delay in a large network. For completeness, we also study MAC design using directional antennas for the case where the channel has a strong line of sight (LOS) component. Our results show that the spatial diversity technique and the directional antenna technique can enhance the performance of mobile ad hoc networks significantly.