移动WiMAX网络的小区切换方案研究
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摘要
IEEE 802.16e移动宽带无线接入标准的出现推进了多媒体业务与无线移动融合,也引发了对于移动宽带无线接入技术问题的思考,其中包括小区切换问题。移动用户的日益增加,大量高速多媒体数据业务的出现都对WiMAX系统容量提出挑战。如何设计合理的切换方案,引导移动用户及时并智能地进行WiMAX小区切换成为一项值得研究的课题。
针对这一问题,本文提出了一种新型的基于容量估计和邻居广播技术的WiMAX切换方案,该方案适用于多WiMAX小区覆盖的网络场景,在移动用户数多,数据流量大的易拥塞网络环境下,该方案具有比较明显的网络优化作用。
根据研究过程,本文首先对WiMAX协议标准以及现有的小区切换方案中的算法、策略、控制模式以及切换技术做了基础研究和介绍。在各小区切换方案中,本文深入研究了适用于移动WiMAX网络的802.16g快速切换技术,对该技术的系统性能进行了理论分析和网络仿真验证,并得到结论,即快速切换技术能够降低切换丢包率,但并不能有效解决网络拥塞环境造成的持续丢包问题,具有一定局限性。
通过总结现有小区切换方案与WiMAX网络特性相结合的难点与问题,本文随之提出新型的基于容量的小区切换方案。其中的创新点包括:方案基于WiMAX小区容量估计和邻居广播技术,以小区有效空闲容量为策略触发切换,从而达到基站间流量均衡;方案系统模型中根据IEEE 802.16标准中OFDM物理层定义提出了一种准确估算WiMAX基站有效容量的理论公式;方案同时设计了一项原创的全局切换概率参数,能够简单有效地控制小区切换问题中的“切换同步效应”。
本文研究工作量中一个重要部分在于实现移动WiMAX网络小区切换的仿真。由于NS-2仿真软件本身不提供WiMAX网络和WiMAX小区切换的支持,研究过程中对NS-2和NIST移动扩展包的数据结构进行了深入研究,并通过修改不同类文件中的大量源代码构架了NS-2下支持WiMAX小区切换的仿真环境,实现了本文提出的切换方案。通过对提出的切换方案进行仿真,证实该方案可以有效降低网络拥塞,快速显著地提升系统吞吐量。
The elaboration of IEEE 802.16e specification for mobile broadband wireless access has driven the convergence of multimedia service and mobile wireless technology, but has also arise discussions on issues surrounding mobile BWA technology, among which stands out the handover problem. With the increasing number of mobile subscribers and myriad type of high-speed multimedia applications, the system capacity of WiMAX system is under challenge. How to design an appropriate handover method which helps users to promptly and smartly switch between WiMAX cells has become an interesting subject.
Regarding this problem, this thesis proposes a novel WiMAX handover method based on capacity estimation and neighbor advertisement. The method is suitable and has evident enhancement for a network with multiple WiMAX cell coverage with large number of mobile subscribers and heavy data traffic.
This thesis presented the WiMAX standards and current handover methods including the handover algorithms, strategy, control mode and techniques in the first place. Among those handover methods, this thesis further studies the 802.16g fast handover technique for mobile WiMAX network, analyses the performance of this technique, verifies with a network simulation and reaches to a conclusion that the fast handover technique could decrease the packet loss due to handover, yet it fails to effectively solve the continuous packet loss due to network congestions.
By summarizing the problems and difficulties on applying the current handover methods to WiMAX network, this thesis proposes a novel handover method based on capacity. Innovations of the proposed method include: the method bases itself on WiMAX cell capacity estimation and neighbor advertisement technology, uses effective idle capacity as a trigger metric in order to achieve traffic load balance; in the system model, we proposes a theoretical calculation method which accurately estimates the effective capacity of WiMAX cell inline with the OFDM PHY specifications in the 802.16 standard; the proposed method also originally introduces a global handover probability factor which effectively controls the“handover synchronization effect”problem during cell handover.
An important part of the work load during our study is to construct the simulation environment for WiMAX handovers. Since the NS-2 simulation software does not provide native support for WiMAX network and WiMAX handovers, we have studied the structure of NS-2 and NIST mobility package and modified many source codes within different classes to construct the simulation environment under NS-2 with WiMAX handover support and realized the proposed method. The simulation result shows that the proposed handover method could effectively solve network congestions and enhance system throughput in a fast and obvious manner.
针对这一问题,本文提出了一种新型的基于容量估计和邻居广播技术的WiMAX切换方案,该方案适用于多WiMAX小区覆盖的网络场景,在移动用户数多,数据流量大的易拥塞网络环境下,该方案具有比较明显的网络优化作用。
根据研究过程,本文首先对WiMAX协议标准以及现有的小区切换方案中的算法、策略、控制模式以及切换技术做了基础研究和介绍。在各小区切换方案中,本文深入研究了适用于移动WiMAX网络的802.16g快速切换技术,对该技术的系统性能进行了理论分析和网络仿真验证,并得到结论,即快速切换技术能够降低切换丢包率,但并不能有效解决网络拥塞环境造成的持续丢包问题,具有一定局限性。
通过总结现有小区切换方案与WiMAX网络特性相结合的难点与问题,本文随之提出新型的基于容量的小区切换方案。其中的创新点包括:方案基于WiMAX小区容量估计和邻居广播技术,以小区有效空闲容量为策略触发切换,从而达到基站间流量均衡;方案系统模型中根据IEEE 802.16标准中OFDM物理层定义提出了一种准确估算WiMAX基站有效容量的理论公式;方案同时设计了一项原创的全局切换概率参数,能够简单有效地控制小区切换问题中的“切换同步效应”。
本文研究工作量中一个重要部分在于实现移动WiMAX网络小区切换的仿真。由于NS-2仿真软件本身不提供WiMAX网络和WiMAX小区切换的支持,研究过程中对NS-2和NIST移动扩展包的数据结构进行了深入研究,并通过修改不同类文件中的大量源代码构架了NS-2下支持WiMAX小区切换的仿真环境,实现了本文提出的切换方案。通过对提出的切换方案进行仿真,证实该方案可以有效降低网络拥塞,快速显著地提升系统吞吐量。
The elaboration of IEEE 802.16e specification for mobile broadband wireless access has driven the convergence of multimedia service and mobile wireless technology, but has also arise discussions on issues surrounding mobile BWA technology, among which stands out the handover problem. With the increasing number of mobile subscribers and myriad type of high-speed multimedia applications, the system capacity of WiMAX system is under challenge. How to design an appropriate handover method which helps users to promptly and smartly switch between WiMAX cells has become an interesting subject.
Regarding this problem, this thesis proposes a novel WiMAX handover method based on capacity estimation and neighbor advertisement. The method is suitable and has evident enhancement for a network with multiple WiMAX cell coverage with large number of mobile subscribers and heavy data traffic.
This thesis presented the WiMAX standards and current handover methods including the handover algorithms, strategy, control mode and techniques in the first place. Among those handover methods, this thesis further studies the 802.16g fast handover technique for mobile WiMAX network, analyses the performance of this technique, verifies with a network simulation and reaches to a conclusion that the fast handover technique could decrease the packet loss due to handover, yet it fails to effectively solve the continuous packet loss due to network congestions.
By summarizing the problems and difficulties on applying the current handover methods to WiMAX network, this thesis proposes a novel handover method based on capacity. Innovations of the proposed method include: the method bases itself on WiMAX cell capacity estimation and neighbor advertisement technology, uses effective idle capacity as a trigger metric in order to achieve traffic load balance; in the system model, we proposes a theoretical calculation method which accurately estimates the effective capacity of WiMAX cell inline with the OFDM PHY specifications in the 802.16 standard; the proposed method also originally introduces a global handover probability factor which effectively controls the“handover synchronization effect”problem during cell handover.
An important part of the work load during our study is to construct the simulation environment for WiMAX handovers. Since the NS-2 simulation software does not provide native support for WiMAX network and WiMAX handovers, we have studied the structure of NS-2 and NIST mobility package and modified many source codes within different classes to construct the simulation environment under NS-2 with WiMAX handover support and realized the proposed method. The simulation result shows that the proposed handover method could effectively solve network congestions and enhance system throughput in a fast and obvious manner.
引文
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[4]张东英、田红心,WiMAX与3G及其LTE技术研究,西安电子科技大学ISN国家重点实验室,无线通信技术,2007年第4期
[5] IEEE-SA Standards Board. IEEE Std 802.16g TM/D4, 2006, Draft IEEE Standard for Local and metropolitan area networks, Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems - Management Plane Procedures and Services. 2006.
[6] IEEE-SA Standards Board. IEEE Std 802.21 TM/D01.00, March 2006,Draft IEEE Standard for Local and Metropolitan Area Networks: Media Independent Handover Services. 2006.
[7] Makelainen A, Analysis of Handoff Performance in Mobile WiMAX Networks, in Department of Electrical and Communications Engineering, HELSINKI UNIVERSITY OF TECHNOLOGY. 2007.
[8]余娟、陈贤亮,基于IEEE802.16eMAC层切换技术的研究,广东通信技术,2008年2月
[9] Lee D H, Kyamakya K, and Umondi J P, Fast handover algorithm for IEEE 802.16e broadband wireless access system, in 2006 1st International Symposium on Wireless Pervasive Computing. Jan. 2006.
[10]李沛、靳浩、张斌、朱映忱,WiMAX跨层切换技术的研究与仿真,现代电信科技,2008年2月
[11]张斌、靳浩、李国强、张巍巍,WiMAX网络快速切换技术研究,中国无线电,2007
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[21] Ormond O, Perry P, and Murphy J. Network selection decision in wireless heterogeneous networks. in Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on, p. 2680-2684 Vol. 4, 2005.
[22] Perez-Romero J, Sallent O, Agusti R etc. Network-controlled cell-breathing for capacity improvement in heterogeneous CDMA/TDMA scenarios. in Wireless Communications and Networking Conference, 2006. WCNC 2006. IEEE, p. 36-41, 2006.
[23] Ylianttila M, Pande M, Makela J etc. Optimization scheme for mobile users performing vertical handoffs between IEEE 802.11 and GPRS/EDGE networks. in Global Telecommunications Conference, 2001. GLOBECOM '01. IEEE, p. 3439-3443 vol.6, 2001.
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[27] Calvagna A and Modica G D, A user-centric analysis of vertical handovers, in Proceedings of the 2nd ACM international workshop on Wireless mobile applications and services on WLAN hotspots, ACM: Philadelphia, PA, USA. 2004.
[28] Park H S, Yoon S H, Kim T H etc. Vertical handoff procedure and algorithm between IEEE 802.11 WLAN and CDMA cellular network. in Proceedings of CDMA InternationalConference'2002, p. 103-112, 2002.
[29] McNair J and Fang Z, Vertical handoffs in fourth-generation multinetwork environments. Wireless Communications, IEEE 11(3): p. 8-15, 2004.
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[31] Pahlavan K, Krishnamurthy P, Hatami A etc., Handoff in hybrid mobile data networks. Personal Communications, IEEE [see also IEEE Wireless Communications] 7(2): p. 34-47, 2000.
[32] Senarath G N and Everitt D. Comparison of alternative handoff strategies for micro-cellular mobile communication systems. in Vehicular Technology Conference, 1994 IEEE 44th, p. 1465-1469 vol.3, 1994.
[33] Tripathi N D, Reed J H, and VanLandinoham H F, Handoff in cellular systems. Personal Communications, IEEE [see also IEEE Wireless Communications] 5(6): p. 26-37, 1998.
[34]李波,蜂窝移动通信系统中越区切换算法的研究,西安电子科技大学,2001年12月
[35] Mande W R. Evaluation of a proposed handover algorithm for the GSM cellular system. in Vehicular Technology Conference, 1990 IEEE 40th, p. 264-269, 1990.
[36] Cornett K G and Wicker S B. Bit error rate estimation techniques for digital land mobile radios. in Vehicular Technology Conference, 1991. Gateway to the Future Technology in Motion., 41st IEEE, p. 543-548, 1991.
[37] Murase A, Symington I, and Green E. Handover criterion for macro and microcellular systems. in Vehicular Technology Conference, 1991. Gateway to the Future Technology in Motion., 41st IEEE, p. 524-530, 1991.
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[2] IEEE-SA Standards Board. IEEE Std 802.16d TM-2004 (Revision of IEEE Std 802-16-2001). IEEE Standard for Local and Metropolitan Area Networks Part 16:Air Interface for Fixed Broadband Wireless Access Systems. 2004.
[3] IEEE-SA Standards Board. IEEE Std 802.16e TM-2005. IEEE Standard for Local and Metropolitan Area 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 Corrigendum 1. 2005.
[4]张东英、田红心,WiMAX与3G及其LTE技术研究,西安电子科技大学ISN国家重点实验室,无线通信技术,2007年第4期
[5] IEEE-SA Standards Board. IEEE Std 802.16g TM/D4, 2006, Draft IEEE Standard for Local and metropolitan area networks, Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems - Management Plane Procedures and Services. 2006.
[6] IEEE-SA Standards Board. IEEE Std 802.21 TM/D01.00, March 2006,Draft IEEE Standard for Local and Metropolitan Area Networks: Media Independent Handover Services. 2006.
[7] Makelainen A, Analysis of Handoff Performance in Mobile WiMAX Networks, in Department of Electrical and Communications Engineering, HELSINKI UNIVERSITY OF TECHNOLOGY. 2007.
[8]余娟、陈贤亮,基于IEEE802.16eMAC层切换技术的研究,广东通信技术,2008年2月
[9] Lee D H, Kyamakya K, and Umondi J P, Fast handover algorithm for IEEE 802.16e broadband wireless access system, in 2006 1st International Symposium on Wireless Pervasive Computing. Jan. 2006.
[10]李沛、靳浩、张斌、朱映忱,WiMAX跨层切换技术的研究与仿真,现代电信科技,2008年2月
[11]张斌、靳浩、李国强、张巍巍,WiMAX网络快速切换技术研究,中国无线电,2007
[12] Antonio I, Antonella M, Claudia C etc. An Access Network Selection Algorithm Dynamically Adapted to User Needs and Preferences. in Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on, p. 1-5, 2006.
[13] Yilmaz O, Furuskar A, Pettersson J etc. Access selection in WCDMA and WLAN multi-access networks. in Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, p. 2220-2224 Vol. 4, 2005.
[14] Sousa V A d, Neto R A d O, Chaves F d S etc. Access Selection with Anticipatory Vertical Handover for Multi-Access Networks. in Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on, p. 1-5, 2006.
[15] Gwon Y, Funato D, and Takeshita A. Adaptive approach for locally optimized IP handoffs across heterogeneous wireless networks. in Mobile and Wireless Communications Network, 2002. 4th International Workshop on, p. 475-479, 2002.
[16] Hongbo L, Bhaskaran H, Raychaudhuri D etc. Capacity analysis of a cellular data system with 3G/WLAN interworking. in Vehicular Technology Conference, 2003. VTC 2003-Fall. 2003 IEEE 58th, p. 1817-1821 Vol.3, 2003.
[17] Katz R H and Brewer E A. The case for wireless overlay networks. in Proceedings of SPIE Multimedia and Networking Conference (MMNC'1996), p. 77-88, Jan. 1996.
[18] Tabbane S. Evaluation of handover target cell determination algorithms for heterogeneous cellular environments. in Communications, 1997. ICC 97 Montreal, 'Towards the Knowledge Millennium'. 1997 IEEE International Conference on, p. 396-400 vol.1, 1997.
[19] Final report on the evaluation of RRM/CRRM algorithms. EVEREST IST-2002-001858. Oct. 2005.
[20] Al-Gizawi T, Peppas K, Axiotis D I etc., Interoperability criteria, mechanisms, and evaluation of system performance for transparently interoperating WLAN and UMTS-HSDPA networks. Network, IEEE 19(4): p. 66-72, 2005.
[21] Ormond O, Perry P, and Murphy J. Network selection decision in wireless heterogeneous networks. in Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on, p. 2680-2684 Vol. 4, 2005.
[22] Perez-Romero J, Sallent O, Agusti R etc. Network-controlled cell-breathing for capacity improvement in heterogeneous CDMA/TDMA scenarios. in Wireless Communications and Networking Conference, 2006. WCNC 2006. IEEE, p. 36-41, 2006.
[23] Ylianttila M, Pande M, Makela J etc. Optimization scheme for mobile users performing vertical handoffs between IEEE 802.11 and GPRS/EDGE networks. in Global Telecommunications Conference, 2001. GLOBECOM '01. IEEE, p. 3439-3443 vol.6, 2001.
[24] Wang H J, Katz R H, and Giese J. Policy-enabled handoffs across heterogeneous wireless networks. in Mobile Computing Systems and Applications, 1999. Proceedings. WMCSA '99. Second IEEE Workshop on, p. 51-60, 1999.
[25] Wei S, Hai J, Weihua Z etc., Resource management for QoS support in cellular/WLAN interworking. Network, IEEE 19(5): p. 12-18, 2005.
[26] Chen L J, Sun T, Chen B etc. A smart decision model for vertical handoff. in Proceedings of 4th International Workshop on Wireless Internet and Reconfigurability, p. 1-5. Athens, Greece, May 2004.
[27] Calvagna A and Modica G D, A user-centric analysis of vertical handovers, in Proceedings of the 2nd ACM international workshop on Wireless mobile applications and services on WLAN hotspots, ACM: Philadelphia, PA, USA. 2004.
[28] Park H S, Yoon S H, Kim T H etc. Vertical handoff procedure and algorithm between IEEE 802.11 WLAN and CDMA cellular network. in Proceedings of CDMA InternationalConference'2002, p. 103-112, 2002.
[29] McNair J and Fang Z, Vertical handoffs in fourth-generation multinetwork environments. Wireless Communications, IEEE 11(3): p. 8-15, 2004.
[30] http://www.cww.net.cn/WiMAX/html/2007/7/16/2007721116183518_1.htm
[31] Pahlavan K, Krishnamurthy P, Hatami A etc., Handoff in hybrid mobile data networks. Personal Communications, IEEE [see also IEEE Wireless Communications] 7(2): p. 34-47, 2000.
[32] Senarath G N and Everitt D. Comparison of alternative handoff strategies for micro-cellular mobile communication systems. in Vehicular Technology Conference, 1994 IEEE 44th, p. 1465-1469 vol.3, 1994.
[33] Tripathi N D, Reed J H, and VanLandinoham H F, Handoff in cellular systems. Personal Communications, IEEE [see also IEEE Wireless Communications] 5(6): p. 26-37, 1998.
[34]李波,蜂窝移动通信系统中越区切换算法的研究,西安电子科技大学,2001年12月
[35] Mande W R. Evaluation of a proposed handover algorithm for the GSM cellular system. in Vehicular Technology Conference, 1990 IEEE 40th, p. 264-269, 1990.
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