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ABSTRACT: This paper presents a performance analysis of reuse partitioning (RUP)-based subchannelized orthogonal frequency-division multiple-access (OFDMA) uplink systems in multicell environments. The cochannel interference (CCI) statistic is calculated for OFDMA uplink systems. The derived statistic is then used to analyze the performance of subchannelized OFDMA systems based on RUP. Analysis and simulation results show that the performance of a subchannelized OFDMA system in multicell environments is noticeably dependent on the CCI, and the effect of CCI can be reduced by the RUP scheme. Finally, the results of the analysis yield the optimum RUP area for achieving the maximum system throughput.
IEEE Transactions on Vehicular Technology 08/2008; · 1.92 Impact Factor
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ABSTRACT: Opportunistic scheduling algorithms with link adaptation can increase system throughput, but have the drawback of requiring the channel quality information (CQI) to be transmitted from all the candidate users. In order to alleviate this problem, we propose a new feedback reduction scheme that preserves CQIs over all channels. The proposed scheme binds similar CQIs in groups to represent them more effectively, and uses a simple method for fast grouping. Simulation results show that the proposed scheme with this simple grouping achieves close to perfect feedback performance with respect to the original CQIs under reasonable feedback loads.
IEEE Transactions on Wireless Communications 07/2008; · 2.59 Impact Factor
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WCNC 2008, IEEE Wireless Communications & Networking Conference, March 31 2008 - April 3 2008, Las Vegas, Nevada, USA, Conference Proceedings; 01/2008
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ABSTRACT: An opportunistic scheduling is adopted to improve the capacity of the system by exploiting the multiuser diversity of multiuser MIMO (MU-MIMO)systems. However, it requires a large amount of feedback carrying the channel quality information (CQI) of each user to the transmitter. The considered per user unitary and rate control (PU<sup>2</sup>RC) needs to feedback the preferred precoding index and its CQIs, and it has a defect in scheduling the streams for the grouped user. In order to overcome these drawbacks, a novel feedback reduction scheme is proposed and is modified for OFDMA systems in this paper. It employs transmitter controlled precoding and opportunistic feedback (TCP-OFB) in conjunction with frequency scheduling. The simulation results demonstrate that TCP-OFB/OFDMA shows comparable performance to PU<sup>2</sup>RC while it only requires far reduced feedback load.
Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007
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ABSTRACT: A novel feedback reduction scheme is proposed for dynamic channel allocation (DCA) in OFDMA systems. Applying this delta-modulation (DM)-based scheme to the channel gain of adjacent subcarriers reduces the feedback information to 1 bit per subcarrier. Since this reduced feedback information can lead to performance degradation in a bit error rate (BER), a modified amplitude craving greedy (ACG) method and improved DM are jointly adopted to minimize the loss. Simulation results verify that the proposed scheme can decrease feedback information by a factor of 1/M while retaining performance comparable to the full feedback case, which requires M bits per subcarrier
IEEE Transactions on Wireless Communications 02/2007; · 2.59 Impact Factor
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IEICE Transactions. 01/2006; 89-A:1566-1570.
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IEICE Transactions. 01/2006; 89-B:1907-1910.
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Vehicular Technology Conference, 2005. VTC-2005-Fall. 2005 IEEE 62nd; 10/2005
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ABSTRACT: A novel feedback-reduction scheme is proposed for dynamic channel allocation (DCA) in OFDMA systems. Applying this delta-modulation (DM)-based scheme to the channel gain of adjacent subcarriers reduces the feedback information to 1 bit per subcarrier. Since this reduced feedback information can lead to performance degradation in the form of an increased bit error rate (BER), a modified amplitude craving greedy (ACG) method and improved DM are jointly adopted to minimize the loss. Simulation results verify that the proposed scheme can decrease feedback information by a factor of 1/M while retaining performance comparable to the full feedback case, which requires M bits per subcarrier as feedback information
Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on; 10/2005
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ABSTRACT: Information of the maximum Doppler frequency enable to optimize many channel-adaptive techniques and radio resource management methods for mobile radio communication systems. In this paper, we propose four maximum Doppler frequency estimators which are based on the level crossing rate (LCR), the zero crossing rate (ZCR), the covariance function (COV) and the autocorrelation function (ACF). To eliminate the influence of additive noise, we analyze the conditions for the estimators independent of the signal-to-noise ratio (SNR) and implement the conditions with a downsampling process in the time domain. The proposed methods achieve good SNR-independent performance in the Rayleigh fading channels
Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on; 10/2005
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ABSTRACT: An opportunistic scheduling is adopted to improve the capacity of the system by exploiting the multiuser diversity of multiuser MIMO (MU-MIMO) systems. However, it requires a large amount of feedback carrying the channel quality information (CQI) of each user to the transmitter. The considered per user unitary and rate control (PU<sup>2</sup>RC) needs to feedback the preferred preceding index and its CQIs, and it has a defect in scheduling the streams for the grouped user. In order to overcome these drawbacks, a novel feedback reduction scheme is proposed and is modified for OFDMA systems in this paper. It employs transmitter controlled preceding and opportunistic feedback (TCP-OFB) in conjunction with frequency scheduling. The simulation results demonstrate that TCP-OFB/OFDMA shows comparable performance to PU<sup>2</sup>RC while it only requires far reduced feedback load.
Vehicular Technology Conference, 2007. VTC-2007 Fall. 2007 IEEE 66th;
