為改善距離基地台較遠或通道狀況較差的使用者傳輸速率，IEEE 802.16j草案中提出了多躍中繼的功能，透過中繼站的轉傳，除了可以提升系統的流通量，另外也可以擴張基地台涵蓋範圍。由於透過中繼站轉傳資料，需要花費多段無線電資源，降低頻率的使用效率。透過資源再利用可以提升頻率的使用效率，然而，在具資源再利用的環境下，流量的不均衡會降低資源的利用率，而導致連線阻塞機率與連線捨棄機上升。
在具資源再利用的IEEE 802.16j的環境下，本論文提出具通道感知資源再利用(Channel-Aware Resource Reuse, CARR)法則。當系統資源不足時，考量同群組中繼站的資源再利用率做為允入控制決策的參考，稱為具通道感知資源再利用之允入控制(Channel-Aware Resource Reuse-Call Admission Control, CARR-CAC)法則。當行動台透過中繼站與基地台建立連線時，基地台根據群組的資源再利用率來決定由哪個中繼站來幫行動台轉傳資料，藉以提升資源再利用率。而行動台在移動的過程中，所造成通道狀況的改變與交遞，都會影響資源再利用率，為了改善在系統的連線阻斷機率與連線捨棄機率，因此提出了具通道感知資源再利用最佳化(Channel-Aware Resource Reuse-Optimal Resource Reuse, CARR-ORR)，當系統資源可能不足以滿足下個訊框所提出要求時，藉由調整使用者的服務站，以提升資源再利用率。經由模擬比較我們所提出的CARR法則與具資源再利用的IEEE 802.16j相比，最多可降低87.93%的連線阻斷機率與78.53%的連線捨棄機率。

In order to provide higher data rates for mobile stations that suffer from lower channel quality due to the longer distances between the mobile stations and the base station, the IEEE 802.16j multi-hop relay specification hence has been proposed. The use of relay stations can help improve the overall system throughput and extend the cell coverage of WiMAX systems. However, the introduction of multi-hop relay may degrade the efficiency of radio resource utilization because the radio resource is shared among the base station and relay stations in general.
The reuse resource is considered in this thesis to improve frequency efficiency. In a resource-reusable environment, the unbalance of traffic load will decrease resource utilization, and then increase blocking probability and dropping probability, so we propose the Channel-Aware Resource Reuse (CARR) scheme to deal with the problem. When available system bandwidth is not enough, the admission control scheme will take the group utilization of resource reuse into account, which is called CARR-CAC (Channel-Aware Resource Reuse Call Admission Control) scheme. When a mobile station wants to establish a connection via relay stations, the base station will select a serving relay station for it, based on the group utilization of resource reuse, to enhance the overall utilization of resource reuse. Moreover, the mobility of mobile station and the handover process can degrade the channel quality and affect the utilization of resource reuse. To reduce call blocking probability and dropping probability, we propose the CARR-ORR (Channel-Aware Resource Reuse, Optimal Resource Reuse) scheme to improve utilization of resource reuse by reassigning new serving stations, when the available system bandwidth is not enough for the next request. Simulation results show that the proposed CARR scheme can reduce 87.93% of blocking probability and 78.53% of dropping probability, compared with the existing resource-reuse-enabled IEEE 802.16j systems.

[1] 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.
[2] IEEE 802.16e-2005, “Local and Metropolitan Networks — Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems, Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum1,” 2006. 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.
[3] IEEE 802.16j-Draft1, “IEEE Standard for Local and Metropolitan Area Networks Part 16 : Air Interface for Fixed Broadband Wireless Access Systems Multihop Relay Specification,” IEEE Std. 802.16j/D1, Aug. 2007.
[4] IEEE 802.16j-Draft2, “IEEE Standard for Local and Metropolitan Area Networks Part 16 : Air Interface for Fixed Broadband Wireless Access Systems Multihop Relay Specification,” IEEE Std. 802.16j/D2, Dec. 2007.
[5] IEEE 802.16j-Draft3, “IEEE Standard for Local and Metropolitan Area Networks Part 16 : Air Interface for Fixed Broadband Wireless Access Systems Multihop Relay Specification,” IEEE Std. 802.16j/D3, Dec. 2007.
[6] Haruki Izumikawa et al., “MAP Multiplexing in IEEE 802.16 Mobile Multi-Hop Relay,” Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on, 2006, pp. 1-5.
[7] Shiang-Jiun Lin et al., “Resource scheduling with directional antennas for multi-hop relay networks in Manhattan-like environment,” Mobile WiMAX Symposium, 2007. IEEE, 2007, pp. 108-113.
[8] R. Pabst et al., “Relay-based deployment concepts for wireless and mobile broadband radio,” Communications Magazine, IEEE, vol. 42, 2004, pp. 80-89.
[9] Hongyi Wu et al., “Integrated cellular and ad hoc relaying systems: iCAR,” Selected Areas in Communications, IEEE Journal on, vol. 19, 2001, pp. 2105-2115.
[10] Chunming Qiao and Hongyi Wu, “iCAR: an integrated cellular and ad-hoc relay system,” Computer Communications and Networks, 2000. Proceedings. Ninth International Conference on, 2000, pp. 154-161.
[11] R. Housley et al., “Internet X.509 Public Key Infrastructure Certificate and CRL Profile,” RFC 2459, Jan. 1999.
[12] Chingyao Huang et al., “Radio resource management of heterogeneous services in mobile WiMAX systems [Radio Resource Management and Protocol Engineering for IEEE 802.16],” Wireless Communications, IEEE [see also IEEE Personal Communications], vol. 14, 2007, pp. 20-26.
[13] Y. Sun et al., “Study of radio resource sharing for future mobile WiMAX applications with relays,” Mobile WiMAX Symposium, 2007. IEEE, 2007, pp. 91-97.
[14] D. Soldani and S. Dixit, “Wireless relays for broadband access [radio communications series],” Communications Magazine, IEEE, vol. 46, 2008, pp. 58-66.
[15] L. Erwu et al., “Performance Evaluation of Bandwidth Allocation in 802.16j Mobile Multi-Hop Relay Networks,” Vehicular Technology Conference, 2007. VTC2007-Spring. IEEE 65th, 2007, pp. 939-943.
[16] David Chen et al., “Channel Models and Performance Metrics for IEEE 802.16j Relay Task Group,” IEEE C802.16j-06/020, May 2007.
[17] Bo Li et al., “A Survey on Mobile WiMAX,” Communications Magazine, IEEE, vol. 45, 2007, pp. 70-75.
[18] Jinfang Zhang, J. Mark, and Xuemin Shen, “An adaptive handoff priority scheme for wireless MC-CDMA cellular networks supporting multimedia applications,” Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE, 2004, pp. 3088-3092 Vol.5.
[19] Haitang Wang, Bing He, and D. Agrawal, “Admission control and bandwidth allocation above packet level for IEEE 802.16 wireless MAN,” Parallel and Distributed Systems, 2006. ICPADS 2006. 12th International Conference on, 2006, p. 60-66.
[20] Haitang Wang, Bing He, and D. Agrawal, “Admission control and bandwidth allocation above packet level for IEEE 802.16 wireless MAN,” Parallel and Distributed Systems, 2006. ICPADS 2006. 12th International Conference on, vol.1, 12-15 July 2006.
[21] Kuan-Chung Chen, “A Cross-Layer Dynamic Radio Resource Allocation and Admission Control in IEEE 802.16j Systems,” Master Degree Thesis at NTUST, 2007.