在IEEE 802.16e無線都會網路中，若行動台距離基地台較遠或位於通訊不良的涵蓋範圍時，必須使用較強健的調變技術，但是導致資料傳送速率降低。若在基地台的涵蓋範圍內建置中繼站，雖可提高行動台的資料傳送速率，但是卻產生遞交(handover)的問題。
考量建置固定式中繼站的IEEE 802.16j環境下，本論文提出集中式和非集中式遞交機制。集中式遞交機制乃由基地台負責選擇行動台之連線對象並處理行動台遞交的問題。本機制設計為相容於IEEE 802.16e的行動台。若考量配置功能較強的固定式中繼站以及針對IEEE 802.16j行動台的環境時，可以使用非集中式遞交機制，由基地台或固定式中繼站和行動台共同決定行動台連線對象以及處理遞交的問題。
模擬結果顯示在IEEE 802.16j系統中，使用集中式遞交機制時，整體傳輸量比IEEE 802.16e系統的整體傳輸量增加17.5%。若使用非集中式遞交機制，整體傳輸量比IEEE 802.16e系統的整體傳輸量增加9%。但是在IEEE 802.16j系統使用集中式遞交機制時，固定式中繼站必須回傳與行動台的通道情況給基地台，所以每個行動台每秒訊令負擔比使用非集中式遞交機制的每個行動台每秒訊令負擔多約131個，系統使用集中式遞交機制的每個行動台每秒訊令負擔更比IEEE 802.16e系統的每個行動台每秒訊令負擔多約160個。因此吾人建議非集中式遞交機制適用於行動台都是IEEE 802.16j的系統，而存在IEEE 802.16e行動台的系統則可選用集中式遞交機制。

In IEEE 802.16e wireless metropolitan area networks, a mobile station (MS) with low signal-to-noise ratio (SNR) must use more robust modulation scheme to transmit packets at lower data rate. Installing relay stations (RSs) at proper locations can improve the data rate of MSs. However, the connection establishment and handovers among MSs and RSs are challenges.
In this thesis, we propose two handover schemes, i.e., centralized and decentralized handover, to accommodate the need of connection establishment and handovers among MSs and RSs in IEEE 802.16j networks. In the centralized handover, the base station (BS) decides whether to connect directly with an MS, or to connect with an MS via a fixed RS (FRS). Also, this system is backward compatible with the IEEE 802.16e MSs. The decentralized handover, if the FRSs have high capability and all MSs support the IEEE 802.16j system, the BS, FRSs and MS cooperate to decide whether to trigger a handover.
Simulation results show that the centralized handover can improve 17.5% more in throughput than the IEEE 802.16e system. Also, using decentralized handover the throughput improvement is 9%. Since FRSs must send the BS its channel quality measurement with the MS in the centralized handover, the centralized handover uses 131 more messages per MS per second than the decentralized handover, while the centralized handover uses 160 more messages per MS per second than the IEEE 802.16e system. Therefore, the decentralized handover is recommended when all MSs support IEEE 802.16j, otherwise, the centralized handover is recommended.

[1] M. Nohara, K. Saito, K. Sugiyama, H. Shinonaga, J. Cho, J. Son, P. Joo, H. Lee, N. Natarajan, David T, Chen and M. Asa, “Mobile multi-hop relay networking in IEEE 802.16,” IEEE C802.16-05/013, July 2005, http://www.ieee802.org/16/sg/mmr/
[2] K. Suh, J. Cho, K. Han, S. Yoon and J. Cho, “Open problems in mobile multi-hop relay system,” IEEE C802.16mmr-05/028, Nov. 2005, http://www.ieee802.org/16/sg/mmr/
[3] IEEE, “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.
[4] IEEE, “Draft amendment to IEEE standard for local and metropolitan area networks - part 16：air interface for fixed and mobile broadband wireless access systems”, IEEE P802.16e/D12, Oct. 2005.
[5] K. K. Leung, S. Mukherjee and G. E. Rittenhouse, “Mobility support for IEEE 802.16d wireless networks,” In Proc. of the IEEE Wireless Communications and Networking Conference, Vol. 3, Mar. 2005, pp. 1446-1452.
[6] S. Choi, G. Hwang, T. Kwon, A. Lim and D. Cho, “Fast handover scheme for real-time downlink services in IEEE 802.16e BWA system,” In Proc. of the IEEE Vehicular Technology Conference (VTC'05), Vol. 3, Jan. 2005, pp. 2028-2032.
[7] D. H. Lee, K. Kyamakya and J. P. Umondi, “Fast handover algorithm for IEEE802.16e broadband wireless access system”, In Proc. of the Wireless Pervasive Computing, Jan. 2006, pp. 1-6.
[8] C. M. Chou, T. M. Lin, F. C. Ren, C. C. Tseng and W. H. Sheen, “Handover scenarios for 802.16 MMR,” IEEE C802.16mmr-06/005, Jan. 2006, http://www.ieee802.org/16/sg/mmr/
[9] G. Shen, W. Ni, W. Zou, K. Zhang, J. Liu, S. Jin, T. Fahldieck and R. Muenzner, “Handover schemes in IEEE 802.16j,” IEEE C802.16j-06/005, May 2006, http://www.ieee802.org/16/relay/
[10] G. Shen, W. Ni, W. Zou, S. Jin, “Recommendation on 802.16 MMR with backward compatibility,” IEEE C802.16mmr-05/023, Nov. 2005, http://www.ieee802.org/16/sg/mmr/
[11] F. C. Ren, C. L. Hsiao, Y. C. Hsu and W. H. Sheen, “A recommendation on PMP mode compatible frame structure,” IEEE C80216mmr-05/005, Sep. 2005, http://www.ieee802.org/16/sg/mmr/
[12] T. M. Lin, C. C. Tseng and W. H. Sheen, “Modification for enabling the RS operations,” IEEE C80216mmr-05/029, Nov. 2005, http://www.ieee802.org/16/sg/mmr/
[13] V. S. Abhayawardhana, I. J. Wassell, D. Crosby, M. P. Sellars and M. G. Brown, “Comparison of empirical propagation path loss models for fixed wireless access systems,” In Proc. of the IEEE Vehicular Technology Conference (VTC'05), Vol. 1, Jan. 2005, pp. 73-77.
[14] C. Eklund, R. B. Marks, K. L. Standwood and S. Wang, “IEEE standard 802.16: a technical overview of the wireless MAN air interface for broadband wireless access,” IEEE Communications Magazine, Vol. 40, June 2002, pp. 98-107.
[15] T. S. Rappaport, Wireless Communications Principles and Practice Second Edition, NJ, Prentice Hall, 2002.
[16] T. Kwon, H. Lee, S. Choi, J. Kim, D.-H. Cho, S. Cho, S. Yun, W.-H. Park and K. Kim, “Design and implementation of a simulator based on a cross-layer protocol between MAC and PHY layers in a WiBro compatible IEEE 802.16e OFDMA system,” IEEE Communications Magazine, Vol. 43, Dec. 2005, pp. 136-146.
[17] A. S. Peter and B, Galvin, Operating System Concepts Fifth Edition, NJ, Prentice Hall, 1998.
[18] D. Kitchener, M. Naden, W. Tong and P. Zhu, “Correlated lognormal shadowing mode,” IEEE C802.16j-06/009, May 2006, http://www.ieee802.org/16/relay/
[19] D. Kitchener, M. Naden, W. Tong, P. Zhu, G. Senarnath, H. Zhang, D. Streer, D. Yu, M. Hart and S. Vadgama, “Multihop path loss model,” IEEE C802.16j-06/011, May 2006, http://www.ieee802.org/16/relay/
[20] M. Hart and S. Vadgama, “Factors that affect performance of a mobile multihop relay system,” IEEE C802.16mmr-05/017, Sep. 2005, http://www.ieee802.org/16/sg/mmr/
[21] D. Chen, I-K. FU, M. Hart and W. C. Wong, “Channel models and performance metrics for IEEE 802.16j relay task group,” IEEE C802.16j-06/020, May 2006, http://www.ieee802.org/16/relay/
[22] P.-Y. Kong, H. Wang, Y. Ge, C.-K. Tham, Y.-C. Liang and V. D. Hoang, “PMP tree and hybrid PMP-mesh for multi-hop relay networks,” IEEE C802.16j-06/008, May 2006, http://www.ieee802.org/16/relay/
[23] G. Senarath, W. Tong, P. Zhu, H. Zhang, D. Steer, D. Yu, M. Naden and D. Kitchener, “Multihop system evaluation methodology: traffic models,” IEEE C802.16j-06/024, May 2006, http://www.ieee802.org/16/relay/
[24] C. Cicconetti, L. Lenzini, E. Mingozzi and C. Eklund, “Quality of service support in IEEE 802.16 networks,” IEEE Network, Vol. 20, Mar. 2006, pp. 50-55.
[25] F-C. Ren, C.-L. Hsiao, C.-C. Tseng and W.-Ho Sheen, “Recommendation on PMP mode compatible TDD frame structure,” IEEE C802.16mmr-05/027, Nov. 2005, http://www.ieee802.org/16/sg/mmr/
[26] A. Ghosh, D. R. Wolter, J. G. Andrews and R. Chen, “Broadband wireless access with WiMax/802.16: current performance benchmarks and future potential,” IEEE Communications Magazine, Vol. 43, Feb. 2005, pp. 129-136.
[27] B. S. Manoj, K. J. Kumar, C. Frank D and C. S. R. Murthy, “On the use of multiple hops in next generation wireless systems,” Wireless Networks, Vol. 12, No. 2, Apr. 2006.
[28] J. Cho amd Z. J. Haas, “On the throughput enhancement of the downstream channel in cellular radio networks through multihop relaying,” IEEE Journal on Selected Areas in Communications, Vol. 22, No. 7, Sep. 2004.
[29] R.-G. Cheng, S.-M. Cheng and P. Lin, “Power-efficient routing mechanism for ODMA systems,” IEEE Transactions on Vehicular Technology, Vol. 55, No. 4, July 2006.
[30] T. Ohseki, N. Fuke, O. Maeshima, H. Iwai, K. Sugiyama and M. Nohara, “Multihop mobile communications system using MC-CDMA in forward links,” In Proc. of the IEEE Wireless Communications and Networking Conference (WCNC'05), Vol. 1, Mar. 2005, pp. 189-194.
[31] R. Pabst, B. H. Walke, D. C. Schultz, P. Herhold, H. Yanikomeroglu, S. Mukherjee, H. Viswanathan, M. Lott, W. Zirwas, M. Fohler, H. Aghvami, D. D. Falconer and G. P. Fettweis, “Relay-based deployment concepts for wireless and mobile broadband radio,” IEEE Communications Magazine, Vol. 42, No. 9, Sep. 2004.