在OFDMA系統下，為了提高頻譜使用效率(spectrum efficiency)，系統資源分配機制盡可能重複使用OFDMA的每一個子載波，亦即同一個子載波有可能會被多個細胞以及多個用戶使用到。這些情況會造成使用同一個子載波的用戶互相干擾，要如何有效降低相互干擾效應以提高系統通訊量並達到公平原則是本論文非常重要的議題之一。

本論文探討多細胞多用戶蜂巢式系統的下行鏈路中基地台與行動用戶間具多對一天線(multi input single output)架構的有效降低用戶間干擾的技術。在此系統中本研究強調基地台的分散式(distributed)運作，亦即基地台間可以不用交換任何資訊(減少overhead)。

另外，在多細胞多用戶的環境，細胞邊緣(cell edge)用戶的訊息容量(capacity)會因為干擾較嚴重而降低很多，因此本論文在分散式系統下並提出功率控制以及用戶篩選的方法以有效提升細胞邊緣用戶的訊息容量以及提升整體用戶的公平性。

In order to increase spectrum efficiency, the resource allocation mechanism of OFDMA system reuses every subcarrier to the best of its ability, which means the same subcarrier would be applied to multi-cell and multi-user. The situations will cause the interferences between the users which were using the same subcarrier. To decrease the interferences effectively is one of the important issues in the thesis.

A technology with MISO(multi input single output) to decrease the interferences between users effectively in multi-cell multi-user downlink system had been proposed in the thesis. The system emphasizes how the distributed operations work at the base stations, which means there are no information exchanges between the base stations.

Since under multi-cell and multi-user environment, the capacity of cell-edged users reduce conspicuously because of the interferences. Hence, the thesis proposed the idea of power control and user selection under distributed system to increase the information capacity of cell-edged users and to elevate the fairness of the users’ information capacity.

[1]ITU-R M.[IMT-TECH] “Requirements related to technical performance for IMT-Advanced radio interference(s),” August 2008
[2]3GPP TR 36.913 V8.0.0 (2008-6) Requirements for Further
Advancements of E-UTRA (LTE-Advance)
[3]3GPP TSG RAN Tdoc RP-070466
[4]Moray Rumney, “LTE and the Evolution to 4G Wireless : Design and Measurement Challenges,” Agilent Technologies, June 2009
[5]R.G. Gallager, Information Theory and Reliable Communication. Wiley, New York, NY, 1968.
[6]D. Huges-Hartogs, “Emsemble Modem Structure for Imperfect
Transmission Media.” US. Patens Nos. 4,679,227 (July 1987),
4,731816 (March 1988), and 4,833,706 (May 1989).
[7]P. S. Chow, J. M. Cioffi, and T. A.C. Bingham, “A Practical Discrete Multitone Transceiver Loading Algorithm for Data Transmission over Spectrally Shaped Channels,” IEEE Trans. On Commun, Vol. 43, pp.773-775, Feb./March/April 1995
[8]R.F.H. Fischer and T.B. Huber, “A New Loading Algorithm for Discrete Multitone Transmission,” in Proc. IEEE GLOBECOM’96,Vol. 1, pp. 724-728, London, November 1996
[9]A. Leke and J.M. Cioffi, “A Maximum Rate Loading Algorithm for Discrete Multitone Modulation,” in Proc. IEEE GLOBECOM’97, Vol. 3, pp.1514-1518, Nov. 1997
[10]J. Jang, K. B. Lee, and Y.-H. Lee, “Transmit Power and Bit Allocations for OFDM Systems in Fading Channel,” in Proc. IEEE GLOBECOM’03, pp.858-862, 2003
[11]Y. Li and G. Su, “An Adaptive Modulation and Power-allocation Algorithm in OFDM System, ” in Proc. IEEE ICCCAS’04, Vol. 1, pp.339-343, June 2004
[12]K. Liu, F. Yin, W. Wang, and Y. Liu, “Efficient Adaptive Loading Algorithm with Simplified Bandwidth Optimization Method for OFDM Systems,” in Proc. IEEE GLOBECOM’05, Vol. 5, pp. 2793-2797, 2005
[13]C. W. Lee and G. J. Jeon, “An Efficient Adaptive Modulation Scheme for Wireless OFDM Systems,” ETRI Journal, Vol. 29, No. 4, August 2007
[14]C. Y. Wong, et al., “Multiuser OFDM with Adaptive Subcarrier, Bit, and Power Allocation,” IEEE J. on Selected in Commun., vol. 17, no. 10, pp. 1747-1758, Oct.1999.
[15]C. Y. Wong, et al., “A real-time sub-carrier allocation scheme for multiple access downlink OFDM transmission,” in Proc. IEEE VTC’99, vol. 2, pp. 1124-1128, 1999
[16]H. Yin and L. Hui, “An efficient multiuser loading algorithm for OFDM-based broadband wireless systems” in Proc. IEEE GLOBECOM’00, vol. 1, 27 Nov. – 1 Dec. 2000, pp. 103-107
[17]D. Kivanc, G.. Li, H. Liu, “Computationally Efficient Bandwidth Allocation and Power Control for OFDMA,” IEEE Trans. on wireless commun., vol. 2, no. 6, pp.1150-1158, 2003
[18]H. Kim, Y. Han, “Optimal Subchannel Allocation Scheme in
Multicell OFDMA Systems,” in Proc. VTC’04, vol. 3, pp.1821-1825, May 2004
[19]Y. J. Zhang, and K. B. Letaief, “Multiuser Adaptive
Subcarrier-and-Bit Allocation With Adaptive Cell Selection for OFDM Systems,” IEEE Trans. on Wireless Commun. Vol. 3, no. 5, pp. 1566-1575, Sept. 2004.
[20]S. Pietrzyk and G. J.M. Tanssen, “Radio Resource Allocation for Cellular Networks Based on OFDMA with QoS Guarantees,” in Proc.IEEE GLOCOM’04,Vol. 4, 29 Nov. – 3 Dec. 2004, pp. 2694-2699
[21]G. Li and H. Liu, “Downlink Radio Resource Allocation for Multi-cell OFDMA System” IEEE Trans. on Commun. Vol. 5, No.12, pp. 3451-3459, December 2006
[22]J. Heo, I. Cha and K. Chang, “A Novel Transmit Power allocation Algorithm Combined with Dynamic Channel Allocation in Reuse Partition-based OFDMA/FDD System,” in Proc. IEEE ICC’06, Vol. 12, pp.5654-5659, June 2006
[23]S. Gault, W. Hachem, P. Ciblat, “Performance Analysis of an OFDMA Transmission　System in a Multicell Environment,” IEEE Trans. On commun., Vol. 55, no. 4, 740-751,Apr. 2007.
[24]L. Venturina, N. Prasad, and X. Wang, “An Improved iterative Water-Filling Algorithm for Multi-Cell Interference Mitigation in Downlink OFDMA Networks,” in Proc. IEEE ACSSC’07, pp.1718-1722, Nov. 2007
[25]S. C. Chen, N. Bambos, and G. J. Pottie, “Admission Control Schemes for Wireless Communication Networks with Adjustable Transmitter Powers,” in Proc. IEEE INFCOM’94, Vol.1, pp.21-28, June 1994
[26]Y.-J. Chang et al., “A graph-based Approach to Multi-Cell OFDMA Downlink Resource Allocation,” in Proc. IEEE GLOCOM’08, pp.1-6, 2008
[27]C.-S. Chiu and C.-C. Huang, “Combined Partial Reuse and Soft Handover in OFDMA Downlink Transmission,” in Proc. IEEE
VTC’08, pp.1707-1711, 2008
[28]R. Y. Chang, et al., “A graph approach to dynamic fractional Frequency reuse (FFR) in multi-cell OFDMA Networks” in Proc. IEEE ICC’09, pp.1-6, June 2009
[29]R. Giuliano, C. Monti and P. Loreti, “WiMAX fractional frequency Reuse for rural environments” IEEE Wireless Commun., Vol. 15, No. 3, pp. 60-65, June 2008
[30]H. Claussen, “Performance of Macro-and Co-Channel Femtocells in a Hierarchical cell structure,” in Proc. IEEE PIMRC’07, pp.1-5, Sept. 2007
[31]L.T.W. Ho, H. Claussen, “Effects of User-Deployed, Co-channel Femtocells on the Call Drop Probability in a Residential Scenario,” in Proc. IEEE PIMRC’07, pp. 1-5, Sept. 2007
[32]V. Chandrasekhar, J. G. Andrews, “Femtocell Networks: A Survey” IEEE Communication Magazine, Vol. 46, No. 9, pp. 59-67, September 2008
[33]S.-P. Yeh, S. Talwar,; S.-C. Lee; H. Kim;“WiMax Femtocells: A Perspective on Network Architecture, Capacity, and Coverage,” IEEE Communication Magazine, Vol. 46, No. 10, pp.58-65, October 2008
[34]X. Li, L. Qian, and D. Kataria, “Downlink Power Control in Co-Channel Macrocell Femtocell Overlay,” in Proc. IEEE CISS’09, pp.383-388, March 2009
[35] A. Tarighat, M. Sadek,A.H. Sayed, “A Leakage-Based Precoding Scheme for Downlink Multi-User MIMO Channels”IEEE
Transactions on Wireless Communications, vol.6. No.5,
pp.1711-1721, 2007.
[36] M. Amin,M. Nafie, M. Fikri,M. Abdallah, “An Interference Mitigation Scheme for Multi-user Multi-cell MIMO Systems” IEEE Computer Engineering Conference, pp. 40 - 43 ,2010
[37] Q. H. Spencer, A. L. Swindlehurst, and M. Haardt, “Zero-forcing Methods for downlink spatial multiplexing in multi-user MIMO channels,” IEEE Trans. Signal Processing, vol. 52, pp. 461–471, Feb.2004.
[38] M. Schubert and H. Boche, “Solution of the multiuser downlink Beamforming problem with individual SINR constraints,” IEEE Trans. Veh. Technol., vol. 53, no. 1, pp. 18–28, Jan. 2004.
[39] A. Bourdoux and N. Khaled, “Joint TX-RX optimisation for MIMOSDMA based on a null-space constraint,” in Proc. IEEE 56th Vehicular Technology Conference, Vancouver, Canada, Sept. 2002, pp. 171–174