摘要
随着无线移动通信技术的迅猛发展,移动通信给人们的生产、生活方式带来了深刻的变革。现有的无线网络技术,如Wi-Fi、WiMAX、TD-SCDMA、Ad Hoc等,都有各自的特点和适用的环境,任何一种网络都不能独立支持所有业务发展的需要。在未来,网络的发展必然是互补共存,而不是简单的取代,只有融合各种技术优势才能提供更好更全面的服务。
WiMAX是一种宽带无线接入技术,其数据传输速率要高于TD-SCDMA所能提供的速率,基站信号覆盖范围也更广,但WiMAX的缺陷在于移动性受到限制。TD-SCDMA继承了蜂窝网络连续覆盖的能力,能实现无缝漫游要求,支持高速移动,这正是WiMAX所欠缺的。可以说,WiMAX主要提供中低速移动性下的高速率数据业务,而TD-SCDMA主要提供高速移动性下的中低速率语音和数据业务。考虑到WiMAX和TD-SCDMA的互补性,这两种网络的融合将会为用户提供高质量的、多样化的、无处不在的服务。
目前,对同构网络的研究比较成熟。对异构网络的研究虽然在近年来慢慢受到越来越多的关注,但是由于WiMAX和TD-SCDMA这两种技术都是新兴起的技术,国内外对两者融合问题的研究还很少、而且现有的研究也尚处于初级阶段,因此对其进行深入的研究是十分重要和极有意义的。
本文主要对WiMAX/TD-SCDMA异构网络融合及其切换机制进行了研究。对于WiMAX/TD-SCDMA异构网络的融合,文中首先研究了WiMAX技术和TD-SCDMA技术,并比较了两种技术的特点；接着分析了WiMAX与TD-SCDMA融合的可行性,并提出WiMAX与TD-SCDMA网络融合方案,其中包括了紧耦合和松耦合两种方案。
对于WiMAX/TD-SCDMA异构网络的切换机制,文中着重进行了垂直切换判决算法和垂直切换执行算法的研究。本文将切换分成两类：移动节点驱动的切换和基站驱动的切换。针对移动节点驱动的切换,提出了基于模糊控制预判决辅助的WiMAX/TD-SCDMA垂直切换判决算法。与一般的垂直切换判决算法不同,本算法采用了预判决辅助机制,能有效地节省系统开销、提高切换判决效率。而且本算法基于多指标判决模糊控制,一方面能够较为全面地考虑到切换判决的因素；另一方面简化了对切换判决指标的处理,避免建立精确的数学模型,有利于增强算法的适应能力。仿真结果表明,该算法能做出及时准确的切换判决,有效抑制乒乓效应,减少不必要的切换。针对基站驱动的切换,提出了基于代价函数的WiMAX/TD-SCDMA垂直切换判决算法。在该算法中,给出用于计算移动节点切换代价的代价函数,选择切换代价值低的移动节点进行切换,以缓解当前接入网络的重负载,达到平衡整个网络系统负载、最大化网络资源利用率和最小化呼叫阻塞率及呼叫掉线率的目的。鉴于垂直切换执行过程对于垂直切换的性能至关重要,本文提出了基于MIHF的快速层次移动IPv6垂直切换执行算法,同时给出了在WiMAX/TD-SCDMA异构网络下的垂直切换执行过程。该算法的特点在于引入了媒介独立切换功能(MIHF),并且结合了层次型移动IPv6 (HMIPv6)和快速移动IPv6 (FMIPv6)各自的优点,使得该算法相比于MIPv6、HMIPv6和FMIPv6更具优势。仿真结果表明,该算法能明显改善垂直切换的性能,切换延时小、信令开销少、数据丢包率低。
With the rapid development of wireless communication technologies, mobile communications have changed people's life deeply. The existing wireless technologies, such as Wi-Fi, WiMAX, TD-SCDMA and Ad Hoc, have their respective advantages, but any of them cannot support all kinds of services independently. Next generation wireless communication systems are expected to relay on integrated networks consisting of multiple wireless technologies to offer high quality of services to mobile users.
WiMAX is a kind of broad band wireless access technology, whose data rate is much faster than that of TD-SCDMA and whose coverage of a base station (BS) is also larger. However, the weakness of WiMAX is its mobility limitation. TD-SCDMA supports seamless access and higher mobility. Given the complementary characteristics of WiMAX (faster data rate, lower-cost, hotspot access, only support lower mobility) and TD-SCDMA (slower data rate, higher-cost, seamless access, support higher mobility), it is significant to combine them to provide multiple services and ubiquitous access for the users.
At present, researches on homogeneous networks are relatively mature. In recent years, researches on heterogeneous networks have been gradually developing, but researches on heterogeneous wireless networks based on WiMAX and TD-SCDMA are still rare and immature at home and abroad because both WiMAX and TD-SCDMA are new emerging technologies. Therefore, studies on WiMAX and TD-SCDMA heterogeneous wireless networks are necessary and meaningful.
In this paper, we have deeply studied network integration and handoff mechanism based on WiMAX and TD-SCDMA. By comparing the respective characteristics of the two technologies, the feasibility of integration between WiMAX and TD-SCDMA was analyzed and their network integration schemes were proposed in this paper. The schemes were including tightly-coupled scheme and loosely-coupled scheme.
For the studies on handoff mechanism of WiMAX and TD-SCDMA, we have laid emphasis on vertical handoff decision algorithm and vertical handoff execution algorithm. In this paper, handoffs were divided into two classes:handoffs initiated by MNs and handoffs initiated by BSs. For the handoffs initiated by MNs, a novel vertical handoff decision algorithm based on fuzzy control in aid of pre-decision method was proposed. Different with the ordinary vertical handoff decision algorithms, this algorithm used pre-decision method which could save system overhead and raise the efficiency of handoff decisions. In addition, fuzzy control was introduced into this algorithm which helped simplify the process on handoff decision criteria and enhanced the adaptability of the algorithm. The simulation results showed that the proposed algorithm could make accurate handoff decisions, reduce unnecessary handoffs and eliminate the ping-pong effect. For the handoffs initiated by BSs, a cost function based vertical handoff decision algorithm was proposed to select the MNs with lower cost values. Then the selected MNs were handed over to relieve heavy load of the current network and decrease the probability of call blocking and dropping. The proposed algorithm took the entire network performance into consideration and balanced the overall load which was more thoughtful than the existing vertical handoff decision algorithms. Vertical handoff execution is critical to the performance of vertical handoffs. In this paper, MIHF based FHMIPv6 vertical handoff execution algorithm was proposed and the WiMAX/TD-SCDMA vertical handoff execution processes were presented. The proposed algorithm introduced MIHF and combined the advantages of HMIPv6 and FMIPv6, which made this algorithm more effective than MIPv6, HMIPv6 and FMIPv6. The simulation results showed that the proposed algorithm could obviously improve the performance of vertical handoffs with lower handoff latency, smaller signal overhead and lower packet loss.
引文
[1]Guerrero J.A., and Barba A.. Policy-based network management reference architecture for an integrated environment WLAN-3G. IEEE Latin America Transactions,2008,6(2):229-235.
[2]Lott M., Siebert M., Bonjour S., Von Hugo D., and Weckerle, M.. Interworking of WLAN and 3G systems. IEEE Proceedings-Communications,2004,151(5): 507-513.
[3]Minghui Shi, Rutagemwa H., Xuemin Shen, Mark J.W., and Saleh A.. A service-agent-based roaming architecture for WLAN/Cellular integrated networks. IEEE Transactions on Vehicular Technology,2007,56(5):3168-3181.
[4]Munasinghe K.S., Rubaiyat K.M., and Jamalipour A.. Designing VoIP session management over interworked WLAN-3G networks. IEEE Wireless Communications,2008,15(4):86-94.
[5]田辉,康桂霞,李亦农,徐海博.3GPP核心网技术.北京：人民邮电出版社,2007.
[6]3GPP TS 23.234 V7.2.0.3GPP system to Wireless Local Area Network (WLAN) interworking, System description (Release 7). Jun.,2006.
[7]Milind M.Buddhikot, Girish Chandranmenon, Seungjae Han, Yui-Wah Lee, Seott Miller, and Luca Salgarelli. Design and implementation of a WLAN/CDMA2000 interworking architeeture. IEEE Communieations Magazine, Nov.,2003.
[8]Sungkwan Jung, Dong-ho Cho, and Osok Song. QoS based vertical handoff method between UMTS systems and wireless LAN networks, IEEE Communieations Magazine, Jul.,2004.
[9]Lim Chaegwon, Kim Dong-Young, Song Osok, and Choi Chong-Ho. SHARE: Seamless handover architecture for 3G-WLAN roaming environment. Wireless Networks,2009,15(3):353-363.
[10]Allan Borges Pontes, Diego dos Passos Silva, Jose Jailton, Otavio Rodrigues, and Kelvin Lopes Dias. Handover management in integrated WLAN and mobile WiMAX networks. IEEE Wireless Communications,2008,15(5):86-95.
[11]Roy J. Jackson Juliet, Vaidehi V., and Srikanth S.. Always Best-Connected QoS integration model for the WLAN, WiMAX heterogeneous network. First International Conference on Industrial and Information Systems,2006:361-166.
[12]Li-Chun Wang, Chen A., and Hung-Hsi Chen. Network selection with joint vertical and horizontal handoff in heterogeneous WLAN and Mobile WiMax systems. IEEE 65th Vehicular Technology Conference,2007:794-798.
[13]Jing Nie, Jiangchuan Wen, and Qi Dong. A seamless handoff in IEEE 802.16a and IEEE 802.11n hybrid Networks. IEEE International Conference on Communications, Circuits and Systems,2008:383-387.
[14]Daehyon Kim, Aura Ganz DePt. Arehiteeture for 3G and 802.16 wireless networks integration with QoS support, Proeeedings of the 2nd International Conference on Quality of Service in Heterogeneous Wired/Wireless Networks, 2008:21-28.
[15]郎为民,刘波.WiMAX技术原理与应用.北京：机械工业出版社,2008.
[16]曾春亮,张宁,王旭莹,俞一鸣.WiMAX/802.16原理与应用.北京：机械工业出版社,2006.
[17]IEEE. "Part 16:Air interface for fixed and mobile broadband wireless access systems". IEEE 802.16e,2005.
[18]董晓鲁,党梅梅,沈嘉,陈洁,龚达宁,张莉.WiMAX技术、标准与应用.北京：人民邮电出版社,2007.
[19]高泽华,赵国安,宁帆,高峰,赵钊.宽带无线城域网——WiMAX技术与应用.北京：人民邮电出版社,2008.
[20]李劫,张勇,王志辉. WiMAX技术、应用及网络规划.北京：电子工业出版社,2009.
[21]佟学俭,罗涛OFDM移动通信技术原理与应用.北京：人民邮电出版社,2005.
[22]田韬,张新程,周晓津,关山WiMAX 16e无线网络技术与应用.北京：人民邮电出版社,2009.
[23]李立华,陶小峰,张平,杨晓辉TD-SCDMA无线网络技术.北京：人民邮电出版社,2007.
[24]朱东照,罗建迪,汪丁鼎,肖清华等TD-SCDMA无线网络规划设计与优化(第2版).北京：人民邮电出版社,2008.
[25]李世鹤TD-SCDMA第三代移动通信系统标准.北京：人民邮电出版社,2003.
[26]段红光,毕敏,肖理兵,郑建宏TD-SCDMA网络规划优化方法与案例.北京：人民邮电出版社,2008.
[27]彭木根,王文博等TD-SCDMA移动通信系统.北京：机械工业出版社.2006.
[28]赵绍刚等TD-SCDMA网络部署、运营与优化实践.北京：电子工业出版社,2010.
[29]张同须,李楠,高鹏.TD-SCDMA网络规划与工程.北京：机械工业出版社,2008.
[30]刘敏,李忠诚,徐刚,张冬梅,马建.异构无线网络中的垂直切换仿真评价模型及评价指标.系统仿真学报,2007,19(2)：277-281.
[31]M.Ylianttila, M. Pande, J. Makela, and P. Mahonen. Optimization scheme for mobile users performing vertical handoffs between IEEE 802.11 and GPRS/EDGE networks. Proceedings of IEEE GLOECOM,2006:3439-3443.
[32]Ahmed H. Zahran, Ben Liang, and Aladin Saleh. Signal threshold adaptation for vertical handoff in heterogeneous wireless networks. Mobile Network Applications,2006,11:625-640.
[33]Wang H., Katz R. H., and Giese J.. Policy-enabled handoffs across heterogeneous wireless network. Proceedings of the Second IEEE WMCSA,1999:51-60.
[34]Hasswa A., Nasser N., and Hassanein H.. Generic vertical handoff decision function for heterogeneous wireless networks. Second IFIP International Conference on Wireless and Optical Communications Networks,2005:239-243.
[35]G. Mola. Interactions of vertical handoffs with 802.11b wireless LANs:handoff policy. Masters theses, Department of Microelectronics and Information Technology, Royal Institute of Technology (KTH), Stockholm, Sweden, March 2004.
[36]L. J. Chen, T.Sun, B.Chen, V.Rajendran, and M. Gerla. A smart decision model for vertical handoff. Proc.4th ANWIRE International Workshop on Wireless Internet and Reconfigurability,2004:315-319.
[37]Wei-wei Jiang, Hong-yan Cui, Qiang-jun Yan, Xiao-juan Wang, and Jian-Ya Chen. A novel application-oriented dynamic network selection in an integrated UMTS and WiMAX environment. IEEE Third International Conference on Communications and Networking in China,2008:158-161.
[38]Nkansah-Gyekye Y., and Agbinya J.I.. A vertical handoff decision algorithm for next Generation wireless networks. IEEE Third International Conference on Broadband Communications, Information Technology & Biomedical Applications,2008:358-364.
[39]Pin-Han Ho, Ying Wang, Fen Hou, and Sherman Shen. A study on vertical handoff for integrated WLAN and WWAN with micro-mobility prediction. IEEE 3rd International Conference on Broadband Communications, Networks and Systems,2006:1-11.
[40]Mirmotahhary N., Mafinejad Y, Atbaei F., and Kouzani A.. An adaptive policy-based vertical handoff algorithm for heterogeneous wireless networks. IEEE 8th International Conference on Computer and Information Technology Workshops,2008:188-193.
[41]Kyung-Soo Jang, Jang-Sub Kim, Ho-Jin Shin, and Dong-Ryeol Shin. A novel vertical handoff strategy for Integrated IEEE 802.11 WLAN/CDMA networks. Proceedings of the Fourth Annual ACIS,2005:616-621.
[42]SuKyoung Lee, Sriram K, Kyungsoo Kim, Yoon Hyuk Kim, and Golmie N.. Vertical handoff decision algorithms for providing optimized performance in heterogeneous wireless networks. IEEE Transactions on Vehicular Technology, 2009,58(2):865-881.
[43]Jae-Woo So. Vertical handoff in integrated CDMA and WLAN systems. AEU-International Journal of Electronics and Communications,2008,62(6):478-482.
[44]Chung-Pyo Hong, Charles C. Weems, and Shin-Dug Kim. An effective vertical handoff scheme based on service management for ubiquitous computing. Computer Communications,2008,31(9):1739-1750.
[45]Huong Nguyen Thi Thanh, and Mitsuji Matsumoto. Ontology-based context management agent for vertical handoff use fuzzy logic decision in heterogeneous network. IEEE First International Conference on Complex, Intelligent and Software Intensive Systems,2007:215-220.
[46]Liu Xia, Ling-ge Jiang, and Chen He. A novel fuzzy logic vertical handoff algorithm with aid of differential prediction and pre-decision Method. IEEE International Conference on Communications,2007:5665-5670.
[47]Majlesi A., and Khalaj B.H.. An adaptive fuzzy logic based handoff algorithm for hybrid networks. Proceedings of ICSP,2002:1223-1228.
[48]Reza M., Nezhad H., Zukarnain Z.A., Udzir N.I., and Othman M.. A connection selection method for vertical handoff in hybrid wireless environment. IEEE First International Symposium on Applied Sciences on Biomedical and Communication Technologies,2008:1-5.
[49]谢胜东,吴蒙.基于模糊控制的垂直切换决定算法.南京邮电大学学报(自然科学版),2007,27(5)：6-10.
[50]Hongwei Liao, Ling Tie, and Zhao Du. A vertical handover decision algorithm based on fuzzy control theory. IEEE First International Multi-Symposiums on Computer and Computational Sciences,2006:309-313.
[51]Yaw Nkansah-Gykekye, and Johnson I. Agbinya, "Vertical handoff between WWAN and WLAN", Proc. International Conference on Networking, International Conference on Systems and International Conference on Mobile Communications and Learning Technologies,2006:132-136.
[52]胡中栋,黎平国,夏冬梅.一种无线异构网络的自适应垂直切换算法.计算机工程与应用,2007,43(31)：145-147.
[53]http://www.ietf.org/rfc/rfc2002.txt
[54]http://tools.ietf.org/html/rfc2003
[55]http://tools.ietf.org/html/rfc2004
[56]http://www.faqs.org/rfcs/rfc1701.html
[57]杨丰瑞,李方伟等.移动IP.北京：人民邮电出版社,2003.
[58]李晓辉,顾华玺,党岚君.移动IP技术与网络移动性.北京：国防工业出版社,2009.
[59]孙利民,阚志刚,郑健平,王在方,廖勇.移动IP技术.北京：电子工业出版社,2003.
[60]http://www.rfc-editor.org/rfc/rfc5380.txt
[61]http://www.ietf.org/rfc/rfc4068.txt
[62]Altaf A, Iqbal F, Javed M.Y.. S3H:A secure seamless and soft handover between WiMax and 3G Networks. IEEE International Conference on Convergence and Hybrid Information Technology,2008:530-534.
[63]黎平国.异构网络环境下的无缝垂直切换机制研究.江西省赣州市：江西理工大学计算机应用技术,2008.
[64]靳淑娴.异构无线网络垂直切换机制的性能分析.北京：北京邮电大学计算机科学与技术,2008.
[65]叶磊UMTS/WLAN网络间基于移动IP和移动SCTP垂直切换的研究.北京：北京邮电大学计算机科学与技术,2007.
[66]Rajeev Koodli, Charles E. Perkins.. Fast handovers and context transfers in mobile networks. ACM SIGCOMM Computer Communication Review,31(5): 116-123.
[67]刘会玉.基于SIP的WWANs和WLANs之间的垂直切换.电信快报,2009,1：42-45.
[68]Haijie Huang, Jianfei Cai. Improving TCP performance during soft vertical handoff. IEEE 19th International Conference on Advanced Information Networking and Applications,2005:329-332.
[69]Seol Jae-Han, Chung Jong-Moon. IEEE 802.21 MIH based handover for next generation mobile communication systems.4th International Conference on Innovations in Information Technology,2008:431-435.
[70]Griffith David, Rouil Richard, Golmie Nada. Performance metrics for IEEE 802.21 media independent handover (MIH) signaling. Wireless Personal Communications,2010,52(3):537-567.
[71]Piri Esa, Sutinen Tiia, Vehkapera Janne. Cross-layer architecture for adaptive real-time multimedia in heterogeneous network environment.2009 European Wireless Conference,2009:293-297.