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84th IEEE Vehicular Technology Conference (VTC-Fall)

作者： Xiao, Chiyang Zeng, Jie Su, Xin Wang, Jing Xu, Xibin Ge, Lu Zhang, Li Tsinghua Univ Res Inst Informat Technol Tsinghua Natl Lab Informat Sci & Technol Beijing Peoples R China

ISBN: (纸本)9781509017010

Ultra dense network (UDN) is identified as one of the key enablers for 5G since it can provide ultra high spectral reuse factor exploiting proximal transmissions. By densifying the network infrastructure equipments, it's highly possible that each user will have one or more dedicated serving base station antennas, introducing the user-centric virtual cell paradigm. However, due to irregular deployment of large amount of base station antennas, the interference environment becomes rather complex, thus introducing severe interferences among different virtual cells. This paper focuses on the downlink transmission scheme in UDN where a large number of users and base station antennas are uniformly spread over a certain area. An interference graph is first created based on the large-scale fadings. Then, base station antennas and users in the virtual cells within the same maximal connected component are grouped together and merge into one new virtual cell cluster, where users are jointly served via zeroforcing beamforming. A multi-virtual-cell minimum mean square error precoding scheme is further proposed to mitigate the inter-cluster interference. Simulation results show that the proposed interference graph based virtual cell merging approach can attain the average user rate performance of the grouping scheme based on virtual cell overlapping with smaller virtual cell size and reduced signal processing complexity.

关键词： Ultra dense networks virtual cell interference graph zero-forcing precoding multi-virtual-cell minimum mean square error precoding

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Limited feedback scheme based on zero-forcing precoding for Multiuser MIMO-OFDM Downlink Systems

Limited feedback scheme based on Zero-forcing Precoding for ...

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5th Annual ICST Wireless Internet Conference (WICON)

作者： Chen, Zhiyong Wang, Wenbo Peng, Mugen Caot, Fengming Beijing Univ Posts & Telecommun Minist Educ Key Lab Universal Wireless Commun Beijing Peoples R China Toshiba Res Europe Ltd Telecom Res Lab Bristol BS1 4ND Avon England

ISBN: (纸本)9789639799868

Conventional zero-forcing precoding was well investigated, but it hadn't considered the channel quality indicator (CQI) mismatch for practical system with limited feedback. This paper studies a novel zero-forcing precoding with channel quality indicator (CQI) estimation and adjusting, channel directional information(CDI) quantization, user scheduling and link adaptation and then proposes a CQI estimation algorithm for multiuser multiple input multiple output antenna (MU-MIMO) downlink systems with limited feedback. Simulation with 3GPP long term evolution system demonstrates that the scheme with proposed method can significantly improve system performance, compared with conventional zero-forcing precoding and single user MIMO systems.

关键词： zero-forcing precoding CQI CDI MMSE MU-MIMO

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Optimal zero-forcing precoding Design - Oversampled FB Frame Approach

Optimal Zero-Forcing Precoding Design - Oversampled FB Frame...

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2010 IEEE International Conference on Acoustics, Speech, and Signal Processing

作者： Li, Shenpeng Zhang, Jingxin Chai, Li Monash Univ Dept Elect & Comp Syst Engn Clayton Vic 3800 Australia Wuhan Univ Sci & Technol Sch Informat Sci & Engn Wuhan 430081 Peoples R China

ISBN: (纸本)9781424442966

This paper presents a frame analysis of zero forcing (ZF) precoding problem. It shows that from a frame point of view, the filter bank (FB) channel is a synthesis frame and its canonical dual analysis frame is the optimal ZF precoder under total power constraint. Based on this analysis, a new precoder design is presented. The new design removes the minimum phase assumption of polyphase FB channel in the existing methods and gives rise to optimal noncausal (stable) precoder. It provides a general framework for optimal zero-forcing precoding under total power constraint. The numerical results show that the new design outperforms existing causal stable design.

关键词： zero-forcing precoding oversampled filter banks dual frame state space approach

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Low-high SNR transition in multiuser MIMO

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ELECTRONICS LETTERS 2015年第3期51卷 296-U98页

作者： Egan, M. Czech Tech Univ Fac Elect Engn CR-16635 Prague Czech Republic

Multiuser multiple-input-multiple-out (MU-MIMO) plays a key role in the widely adopted 3GPP LTE standard for wireless cellular networks. Although exact and asymptotic sum-rate results are well known, the problem of obtaining intuitive analytical results for medium signal-to-noise ratios (SNRs) is still not solved. As a result of the present reported work, the bend point is proposed, which quantifies the transition between low and high SNR, i.e. the beginning of the high SNR region. The bend point is derived for MU-MIMO with zero-forcing precoding and is obtained, that it is intimately related to the intercept of the high SNR asymptote with the zero sum-rate line. Using this result, a new approximation of the sum-rate at the bend point it is shown providing a useful rule of thumb for the effect of increasing the number of antennas at medium SNR.

关键词： 3G mobile communication Long Term Evolution MIMO communication cellular radio precoding 3GPP LTE standard MU MIMO antennas asymptotic sum-rate bend point exact sum-rate low-high SNR transition medium signal-to-noise ratios multiuser multiple-input and multiple-out system wireless cellular networks zero sum-rate line zero-forcing precoding

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Optimal zero-forcing precoding Design - Oversampled FB Frame Approach

Optimal Zero-Forcing Precoding Design - Oversampled FB Frame...

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IEEE International Conference on Acoustics, Speech, and Signal Processing

作者： Shenpeng Li Jingxin Zhang Li Chai Department of Electrical and Computer Systems Engineering Monash University Clayton Vic 3800 Australia School of Information Science and Engineering Wuhan University of Science and Technology Wuhan 430081 P.R. China

ISBN: (纸本)9781424442959

关键词： zero-forcing precoding oversampled filter banks dual frame state space approach

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zero-forcing Beamforming in Multiuser MISO Downlink Systems Under Per-Antenna Power Constraint and Equal-Rate Metric

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第1期12卷 228-236页

作者： Lee, Sang-Rim Kim, Jin-Sung Moon, Sung-Hyun Kong, Han-Bae Lee, Inkyu Korea Univ Sch Elect Engn Seoul South Korea

In this paper, we analyze the average sum rate of downlink multi-antenna systems with zero-forcing beamforming (ZFBF). In practical implementations, each antenna is equipped with its own power amplifier and is limited individually by linearity of the amplifier. Thus, this paper adopts a more realistic per-antenna power constraint instead of conventional sum-power constraint on transmit antennas. To this end, we first show that a distribution of the received signal-to-noise ratio (SNR) of the ZFBF scheme with per-antenna power constraint and equal-rate metric can be approximated as a minimum of chi-square random variables. Based on this result, we present an accurate formula of the average sum rate in a closed form. Furthermore, employing extreme value theory, an expression of the asymptotic average sum rate with large numbers of transmit antennas and users is derived from the limiting distribution of the received SNR. Simulation results verify the validity of our analysis even with not so large numbers of transmit antennas and users.

关键词： Broadcast channel zero-forcing precoding per-antenna power constraints

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zero-forcing precoding and generalized inverses

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2008年第9期56卷 4409-4418页

作者： Wiesel, Ami Eldar, Yonina C. Shamai (Shitz), Shlomo Technion Israel Inst Technol IL-32000 Haifa Israel Univ Michigan Coll Engn Dept Elect Engn & Comp Sci Ann Arbor MI 48109 USA

We consider the problem of linear zero-forcing precoding design and discuss its relation to the theory of generalized inverses in linear algebra. Special attention is given to a specific generalized inverse known as the pseudo-inverse. We begin with the standard design under the assumption of a total power constraint and prove that precoders based on the pseudo-inverse are optimal among the generalized inverses in this setting. Then, we proceed to examine individual per-antenna power constraints. In this case, the pseudo-inverse is not necessarily the optimal inverse. In fact, finding the optimal matrix is nontrivial and depends on the specific performance measure. We address two common criteria, fairness and throughput, and show that the optimal generalized inverses may be found using standard convex optimization methods. We demonstrate the improved performance offered by our approach using computer simulations.

关键词： beamforming generalized inverses per-antenna constraints semidefinite relaxation zero-forcing precoding

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Performance of Limited Feedback MU-MIMO in Distributed Antenna Systems with Different Schedulers

Performance of Limited Feedback MU-MIMO in Distributed Anten...

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IEEE 11th Malaysia International Conference on Communications (MICC)

作者： Behjati, Mehran Ismail, Mahamod Ibrahim, Muhammad Univ Kebangsaan Malaysia Dept Elect Elect & Syst Engn Ukm Bangi 43600 Selangor Malaysia Univ Teknol MARA Fac Elect Engn Shah Alam 40450 Selangor Malaysia

ISBN: (纸本)9781479915323

Distributed antenna system (DAS) acts as an effective solution to mitigating interference and path-loss by decreasing the access distance for users, and increases the cell coverage and system capacity as well. This study evaluates performance of scheduling methods on the DAS where practical system constraints are considered, such as path-loss, out-of-cell interference and limited feedback. zero-forcing multiuser MIMO precoding is utilized as downlink transmission strategy, when imperfect channel state information is available at the transmitter. System performance is evaluated by empirical cumulative density functions of the cell throughput, where a long-term evolution advanced (LTE-A) standard compliant simulator is utilized for simulation. It is demonstrated that by spreading the transmit antennas throughout the cell more cell throughput is achievable. Moreover, by utilizing an appropriate scheduling algorithm, more potential of DAS can be extracted and leads to substantial cell throughput.

关键词： distributed antenna system limited feedback zero-forcing precoding user scheduling

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QoS Guaranteed Resource Allocation in Cooperative Cellular Network With MIMO-Based Relays

QoS Guaranteed Resource Allocation in Cooperative Cellular N...

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IEEE International Conference on Communications (ICC)

作者： Phuyal, Umesh Jha, Satish C. Bhargava, Vijay K. Univ British Columbia Vancouver BC V5Z 1M9 Canada

ISBN: (纸本)9781612842332

Relay-based cooperative transmission in cellular wireless networks has been an area of tremendous research recently. Since multiple-input multiple-output (MIMO) technique has been shown to increase the spectral efficiency significantly, relays with MIMO antennas seem to be potential candidates for future cooperative cellular system in order to achieve reliable transmission, high system throughput and extended network coverage. In this paper, we study a cellular system scenario where quality of service of multiple data streams originating from a base station (BS) targeted to multiple mobile stations (MSs) is guaranteed by using pre-installed relay stations (RSs) with MIMO antennas. We propose a low-complexity algorithm to design precoder matrices at BS and RS by using joint zero-forcing strategy to avoid multiuser interference in the signal received at the MSs via both the direct path (BS-MS) and the relay path (BS-RS-MS). The proposed algorithm guarantees a predefined signal-to-noise ratio at each user within the transmit power constraint at BS and with the minimal sum transmit power of BS and RS. Simulation results show that proposed algorithm outperforms the singular value decomposition (SVD)-based scheme existing in the literature by keeping the outage probability lower. Moreover, the performance of proposed algorithm compared to that of SVD-based scheme is further improved when the RS is not situated directly between the BS and the MSs.

关键词： Cellular network cooperative communication MIMO relay power allocation quality of service system outage zero-forcing precoding

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Imperfect Channel Knowledge for Interference Avoidance

Imperfect Channel Knowledge for Interference Avoidance

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作者： Lajevardi, Saina University of Alberta

学位级别：master

This thesis examines various signal processing techniques that are required for establishing efficient (near optimal) communications in multiuser multiple-input multiple-output (MIMO) environments. The central part of this thesis is dedicated to acquisition of information about the MIMO channel state - at both the receiver and the transmitter. This information is required to organize a communication set up which utilizes all the available channel resources. Realistic channel model, i.e., the spatial channel model (SCM), has been used in this study, together with modern long-term evolution (LTE) standard. The work consists of three major themes: (a) estimation of the channel at the receiver, also known as tracking; (b) quantization of the channel information and its feedback from receiver to the transmitter (feedback quantization); and (c) reconstruction of the channel knowledge at the transmitter, and its use for data precoding during communication transmission

关键词： Channel Knowledge Feedback Quantization ChannelEstimation LTE Systems MIMO Multipath Channel Reconstruction zero-forcing precoding Multiuser Interference

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