Browsing by Author "Yeh, Chu-Jung"

Now showing 1 - 12 of 12

3-Cell Network MIMO Architectures with Sectorization and Fractional Frequency Reuse
(2011-06-01)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
傳播研究所
;
電機工程學系
;
Institute of Communication Studies
In this paper, we present a 3-cell network multiple-input multiple-output (MIMO) architecture with fractional frequency frequency (FFR) and a novel tri-sector frequency partition scheme. One fundamental question to apply the network MIMO technique in such a high interference environment is: how many base stations should be coordinated together to provide sufficient performance? We will demonstrate that the FFR-based 3-cell network MIMO architecture with the proposed tri-sector frequency partition can not only effectively overcome the inter-group interference, but can avoid executing the complex multibase-station joint processing for a huge number of cluster of cells at all locations. It will be shown that the proposed 3-cell network MIMO with the rearranged tri-sector frequency partition strategy can outperform the 7-cell network MIMO with omni-directional antennas. Various sector antenna architectures and the method for determining the inner region of the FFR cell planning are also discussed and analyzed on top of the network MIMO system. We hope that this study can provide important insights into the design of the network MIMO systems from the perspectives of architecture and deployment.
A closed-form approximation for capacity of multiuser MIMO broadcast systems: A virtual user approach
(2008)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
Li, Chi-Fang
;
交大名義發表
;
National Chiao Tung University
Besides delivering high data rates in a point-to-point scenario, multi-input multi-output (MIMO) antenna techniques can broadcast personalized data to multiple users in the point-to-multipoint scenario. Zero-forcing beamforming (ZFB) is a suboptimal but simple MIMO broadcast technique, which basically decouple the MIMO channel into many parallel single-input single-output (SISO) channels. In this article, we first derive the closed-form expression for the sum rate of the ZFB MIMO broadcast system with random user selection. Secondly, under the condition with finite users, we develop a virtual user approach approximation method for estimating the sum rate of the ZFB MIMO broadcast system with exhaustive user selection. Our results indicate that the proposed analysis method can accurately estimate the optimal sum-rate throughput of ZFB.
A Three-Cell Coordinated Network MIMO with Fractional Frequency Reuse and Directional Antennas
(2010)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
交大名義發表
;
National Chiao Tung University
In this paper, we propose three-cell network multiple-input multiple-output (MIMO) schemes to mitigate the inter-cell interference in a multi-cell system with each cell using the same spectrum. One fundamental question to apply the network MIMO technique in such a high interference environment is: how many cell should coordinate together to provide sufficient signal-to-interference plus noise ratio (SINR)? Consider interferences from the other coordinated groups, we find that on top of the tri-sector directional antenna and fractional frequency reuse (FFR), the network MIMO based on the proposed three-cell coordination strategy can outperform seven-cell based network MIMO with omni-directional antenna. We also consider the effect of different cell sectorings by using 120 degrees and 60 degrees beamwidths directional antennas.
Adaptive Joint Subchannel and Power Allocation for Multi-User MIMO-OFDM Systems
(2008)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
交大名義發表
;
National Chiao Tung University
In this paper, we investigate the resource allocation issue in spatial-multiplexing based downlink multiuser multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The key issue is the allocation of subchannels and power among users to share the system. Previous literature mainly focus on maximizing capacity but ignore the intrinsic coverage shrinkage problem in a MIMO system. Particularly, we formulate a system with larger coverage and link reliability under a proportional rate requirement among users. To alleviate the complexity of jointly optimal subchannel and power allocation, we at first propose two suboptimal subchannel allocation algorithms, namely, user-oriented and subchannel-oriented allocations. We next propose a low-complexity power allocation method.
Cell Grouping and Autonomous Channel Assignment for Cooperative Multi-Cell MIMO Systems
(2009)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
交大名義發表
;
National Chiao Tung University
In this paper, we propose a three-cell network multiple-input multiple-output (MIMO) scheme to mitigate the inter-cell interference in an orthogonal frequency division multiple access (OFDMA) system with each cell using the same spectrum. One fundamental question to apply the network MIMO technique in such a high interference environment is: how many base station should coordinate together to provide sufficient signal-to-interference plus noise ratio (SINR) performance? We find that on top of the tri-sector directional antenna and fractional frequency reuse (FFR), the network MIMO based on the proposed three-cell coordination strategy can already improve SINR performance significantly compared to the 19-cell coordination network MIMO without FFR and tri-sector cellular architecture.
Coverage enhancement for OFDM-based spatial multiplexing systems by scheduling
(2007)
Wang, Li-Chun
;
Chiu, Cheng-Wei
;
Yeh, Chu-Jung
;
Li, Chi-Fang
;
交大名義發表
This paper proposes a low-complexity coverage-oriented subcarriers assignment (COSA) algorithm which can efficiently assign the subchannels to enhance the coverage reliability of the orthogonal frequency division multiplexing (OFDM) based spatial multiplexing systems in the multiuser environment. Motivated by the increasing popularity of OFDM and the multi-input multi-output (MIMO) technique, how to use the multiuser and the frequency diversity simultaneously to improve the coverage reliability of the diversity-deficient multiplexing system is an essential issue. Because the total available transmit power is split uniformly across transmit antennas in the OFDM-based spatial multiplexing systems, increasing the number of transmit antennas leads to a smaller signal-to-noise ratio (SNR) per degree of freedom. Thus we propose the COSA algorithm to enhance the coverage performance of this system. Besides, by means of order statistics and Glivenko-Cantelli Theorem, we develop an analytical expression for the link outage probability and cell coverage reliability of the OFDM-based spatial multiplexing systems when using COSA, respectively.
Coverage performance analysis of multiuser MIMO broadcast systems
(2008)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
Li, Chi-Fang
;
交大名義發表
;
National Chiao Tung University
We consider the downlink of a multiuser multi-input multi-output (MIMO) broadcast channel under a single cell structure. To study the achievable link coverage performance of zero-forcing beamforming (ZFB) and zero-forcing dirty-paper coding (ZF-DPC) when the channel state information (CSI) is available to the transmitter. First we develop analytical closed-form expressions for the link outage probability and coverage reliability of baseline ZFB and ZF-DPC when no multiuser scheduling involved. We find that the coverage performance of ZFB can only approach to that of the weakest link of ZF-DPC under predetermined required SNR and outage probability. Secondly, for exploring the achievable cell coverage, we discuss the strongest link performance of both broadcast beamforming schemes under multiuser scheduling. Under a framework of analysis for ZF-DPC and simulation for ZFB, we show that a soft coverage enhancement can be easily done by using scheduling techniques without extra hardware power consumption.
Coverage performance analysis of OFDM-based spatial multiplexing systems
(2007)
Wang, Li-Chun
;
Chiu, Cheng-Wei
;
Yeh, Chu-Jung
;
Sheen, Wern-Ho
;
交大名義發表
Combining multi-input multi-output (MIMO) antenna techniques with orthogonal frequency division multiplexing (OFDM) modulation (MIMO-OFDM) becomes an attractive air-interface solution for the next generation high speed wireless systems. Nevertheless, because the total available transmit power is split uniformly across transmit antennas in MIMO-OFDM systems, increasing the number of transmit antennas leads to a smaller signal-to-noise ratio (SNR) per degree of freedom. Thus the coverage performance of this kind of MIMO-OFDM system becomes an essential issue. In this paper by means of order statistics and Glivenko-Cantelli theorem, we develop an analytical expressions for the link outage probability and cell coverage reliability of OFDM-based spatial multiplexing systems in a frequency selective fading channel, respectively.
On the Performance of Receive ZF MIMO Broadcast Systems with Channel Estimation Errors
(2011)
Yeh, Chu-Jung
;
Wang, Li-Chun
;
Wu, Jwo-Yuh
;
交大名義發表
;
National Chiao Tung University
While the zero-forcing (ZF) transmit beamforming is a widely used technique for realizing multiple-input multiple-output (MIMO) broadcast transmissions, the ZF receiver combined with multiuser scheduling is an effective alternative that yields improved robustness against channel state information (CSI) mismatch caused by feedback link errors. In this paper we consider the practical scenario that channels are imperfectly estimated at the receiver. Our goal is to characterize the sum rate performance of the receive ZF MIMO broadcast systems under channel estimation errors. We derive analytic sum-rate expressions for both the uniform transmit power and transmit water-filling cases. Our analytic results characterize the sum-rate floor incurred by channel estimation errors. Numerical simulations are used to confirmed the analytic study.
On the performance of zero-forcing beamforming for MIMO broadcast systems
(2007)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
交大名義發表
;
National Chiao Tung University
RESOURCE ALLOCATION METHOD FOR MULTI-USERS MULTIPLE INPUT MULTIPLE OUTPUT ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM AND APPARAUS THEREOF
(2010-03-11)
Wang, Li-Chun
;
Yeh, Chu-Jung
The present invention is direct to the resource allocation method for MU-MIMO-OFDM system and the apparatus thereof. The MU-MIMO-OFDM system has a plurality of users and a plurality of sub-channels. The sub-channels are assigned to the users according to the capacity ratio constraints and a scheduling rule, and then the power of the user is determined according to the limit power of the MU-MIMO-OFDM system. Wherein the values of power of the sub-channels assigned to the user are the same, the scheduling rule may be Max-Min or Max Sum-Rate rule, and the allocation of the sub-channels may be user-oriented or sub-channel oriented.
Scheduling for Multiuser MIMO Broadcast Systems: Transmit or Receive Beamforming?
(2010-09-01)
Wang, Li-Chun
;
Yeh, Chu-Jung
;
傳播研究所
;
電機工程學系
;
Institute of Communication Studies
In this paper, we present an approximation formula and the close-form expression for the sum rate of the transmit and the receive zero-forcing (ZF) multiple-input multiple-output (MIMO) broadcast systems with user selection, respectively. Instead of assuming a large number of users to obtain a scaling law as most current work, we derive the sum rate formulas of the ZF MIMO broadcast systems with a small number of scheduled users. By analysis and simulations, we find that when taking the variations of feedback channel into account, the receive ZF MIMO broadcast system is more robust to feedback errors and can deliver equal or even higher sum rate than the transmit ZF MIMO broadcast system. We discuss whether a feedback channel is suitable to send channel state information (CSI) for calculating transmit antenna beamforming weights, or suitable to send CSI for selecting users in the receive ZF MIMO broadcast system. Our results show that as the variation of feedback channel errors increases from 0.5 to 1.5, the receive ZF 3 x 3 MIMO broadcast system can provide 36% to 116% higher sum rate than the transmit ZF 3 x 3 MIMO broadcast system in the case of 20 users at signal to noise ratio (SNR) equal to 20 dB. Providing that more feedback bandwidth and an error-free feedback channel are available, the transmit ZF MIMO broadcast system can achieve higher sum rate than the receive ZF MIMO broadcast system.