現今的無線通訊應用越來越多，人們對於傳輸速率的要求也急速的上升，本篇論文提出一種適應性子載波分配的演算法,稱為”覆換式”演算法（Iterative Exchange algorithm），靠著反覆交換較好通道狀態的子載波，此演算法可以減少使用的子載波處在嚴重衰落的狀態，經由模擬結果得知，和建設性初始化分配演算法(Constructive initial allocation)和可適性調變演算法(Adaptive Modulation)合作，可以使效能得到顯著的改善；在本篇中，我們使用這三個演算法來達到：最大輸出率和最小符號錯誤率。根據模擬結果得知，當系統使用建設性初始化分配演算法(Constructive initial allocation)和可適性調變演算法(Adaptive Modulation)後，可以使輸出率得到顯著的提升，而使用本篇提出的覆換式演算法（Iterative Exchange algorithm）則能再加的改善符號錯誤率的問題

While more and more wireless application and devices are developed, the demand of transmission rate has been increasing rapidly. In this article, a dynamic subcarrier allocation algorithm called iterative exchange (IE) algorithm is proposed. IE algorithm is designed to avoid deep fading by exchanging the subcarrier with good channel condition. By combining construction initial (CIA) and adaptive modulation (AM) algorithms, the performance can be improved significantly by experiment simulation; These three algorithms are implemented to achieve two goals : maximum throughput (MT) and minimum SER (MSER). As the simulation results, system with CIA and AM algorithms can improve the throughput significantly and then combining the IE algorithm can refine the SER.

[1] J. A. C. Bingham, “Multicarrier modulation for data transmission : an idea whose
time has come, ” IEEE Commun Mag., May 1990.
[2] J. Cioffi, “A multicarrier primer,” Contribution, T1E1.4/91-157, Nov. 1991.
[3] ETS 300 744 rev 1.2.1, (1999-01), “Digital broadcasting systems for television,
sound and data services (DVB-T); framing structure, channel coding and
modulation for digital terrestrial.”
[4] IEEE Std 802.11a-1999, Part 11, “Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) specifications; high-speed physical layer in
the 5 GHz band.”
[5] IEEE 802.11g-2003, “IEEE Standard forInformation technology,
telecommunications and information exchange between systems, local and
metropolitan area networks, specific requirements,Part 11: Wireless LAN
Medium Access Control (MAC) and Physical Layer (PHY) specifications,
Amendment 4: further higher-speed physical layer extension in the 2.4 GHz
band.”
[6] RP-040221, “Feasibility Study for Orthogonal Frequency Division Multiplexing
(OFDM) for UTRAN enhancement”, 3GPP TR 2.8902 v6.0.0, June 2004.
[7] H. Yaghoobi, “Scalable OFDMA physical layer in IEEE 802.16 WirelessMAN,”
Intel Technology Journal, vol. 8, no. 3, Aug. 2004.
[8] T. S. Rappaport, “Wireless Communications Principles & Practice,” Prentice
Hall, 1999.
[9] P. Dent, G. E. Bottomley, and T. Croft, “Jakes fading model revisited,”
Electronics Letters, vol. 29, pp.1162-1163, No.13, June. 1993
[10] W. C. Jakes,1974,”Microwave Mobile Communications”,IEEE PRESS, ISBN
0-7803-1069-1
[11] Guidelines for evaluation of radio transmission technologies for IMT-2000,
ITU-R Recommendation M.1225, Feb. 1997.
[12] G. Song and Y. (G). Li, "Utility-based Resource Allocation and Scheduling in
OFDM-Based Wireless Broadband Networks" IEEE Commun. Mag. July 2005
[13] I. C. Wong, Z. Shen, B. Evans, and J. Andrews, "Adaptive Resource Allocation
in Multiuser OFDM Systems with Proportional Fairness," IEEE Trans. on
Wireless Communications, Available at:
http://www.ece.utexas.edu/bevans/papers/2005/multiuserOFDM/
AdaptResAllMUOFDM.pdf
[14] D. Hughes-Hartogs, “Ensemble modem structure for imperfect
transmissionmedia,” U. S. Patent no. 4,679,227, July 1987.
[15] C. Y. Wong, R. S. Cheng, K. B. Letaief, et al, “Multiuser OFDM with adaptive
subcarrier, bit, and power allocation,” IEEE JSAC, vol. 17, pp.1747-1758, 1999.
[16] C. Y. Wong, C. Y. Tsui, R. S. Cheng, K. B. Letaief, et al, “A Real-time
Sub-carrier Allocation Scheme for Multiple Access Downlink OFDM
Transmission” Proc. IEEE seminar. Vehicular Technology Conf. Fall ’99, pp.
1124-1128, Sept. 1999.
[17] D. Marabissi, D. Tarchi, R. Fantacci, F. Genovese, “Adaptive Modulation
Algorithms Based on Finite State Modeling in Wireless OFDMA Systems,” Proc.
of IEEE PIMRC 2007, Sep. 2007.
[18] D. Marabissi, D. Tarchi, R. Fantacci, F. Genovese, “Adaptive Modulation in
Wireless OFDMA Systems with Finite State Modeling” Proc. of IEEE
Globecom ''07, Nov. 2007
[19] G.992.1 (G. dmt) Draft Recommendation, Working Group T1E1.4, Arlington,
Virginia; 20-23 May 1999.
[20] Moore, Edward F (1956). "Gedanken-experiments on Sequential Machines".
Automata Studies,Annals of Mathematical Studies (34): 129 153. Princeton, N.J.:
Princeton University Press
[21] D. Takeda, Y. C. Chow, P. Strauch, and H. Tsurumi, “Threshold controlling
scheme for adaptive modulation and coding system,” Proc. of IEEE PIMRC
2004, Barcelona, Spain, Sep. 2004.
[22] J. G. Proakis, “Digital Communications,” 3rd ed. McGraw-Hill International,
1995, ch. 12.
[23] P. Viswanath et al., “Opportunistic Beamforming Using Dumb Antennas,” IEEE
Trans. Info. Theory, vol. 48, no. 6, June 2002, pp. 1277–94.
[24] R. Knopp and P. Humblet, “Information Capacity and Power Control in
Single-cell Multiuser Communications,” Proc, ICC, Seattle, WA, June 1995
[25] IEEE Standard for local and metropolitan area networks - Part 16: Air Interface
for Fixed Broadband Wireless Access Systems, IEEE Std. 802.16-2004, Oct.
2004.
[26] Amendment to IEEE Standard for Local and Metropolitan Area Networks - Part
16: Air Interface for Fixed Broadband Wireless Access Systems - Physical and
Medium Access Control Layers for Combined Fixed and Mobile Operation in
Licensed Bands, IEEE Std. 802.16e- 2005, Dec. 2005.