基于802.16系统的跨层QoS保证和调度算法研究
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摘要
下一代无线城域网技术IEEE 802.16 d／e标准定义了一系列相互协作的协议规范，来支持无线接口上的多样化业务的服务质量(QoS)。在媒体接入控制(MAC)层，对QoS调度业务类别、业务流管理、带宽请求、轮询、带宽分配机制及相关信令等进行了详细定义，但却把QoS参数映射、准入控制、流量调节、调度算法等一系列QoS保证问题留待开发者来解决。在物理层，采用自适应编码调制(AMC)等技术，来保证1~*10~(-6)的误码率。由于无线城域网自身多样化业务特性和无线传输信道特征的时变特点，802.16系统端到端的QoS保证需要各层之间相互协作，所以跨层协议研究是未来的重点。
本文基于现有的QoS保证机制和支持QoS的分组调度算法，研究和设计了基于802.16系统的跨层QoS保证和调度算法。在BS端，增加了准入控制模块、上行调度模块、AMC控制模块。在SS端，增加了流量调节模块、下行调度模块和AMC选择模块。调度模块采用了两层的基于优先级的综合调度算法。在第一层，采用逆差公平优先队列(DFPQ)算法，在不同连接类别之间调度，兼顾优先级和公平性。在第二层，根据UGS、rtPS、ertPS、nrtPS、BE业务的不同QoS需求特点和物理层当前信道特性，动态更新调度优先级函数(PRF)，在同一连接类别之间基于优先级进行调度。AMC选择模块周期性地测量无线信道，更新马尔可夫模型转移概率矩阵以跟踪当前的信道特征，动态选择物理层传输模式(包括调制方式和前项纠错编码方式)，在保证系统误包率(PER)要求的同时，最大可能地提高系统频谱效率。
本文的跨层QoS架构中，各功能模块通过协同运作，来增强WiMAX对端到端QoS的支持。其中，AMC控制模块为调度模块提供物理层参数归一化信道质量因子。调度模块为不同的连接分配合理的调度优先级，满足多样化业务的QoS需求，兼顾各类连接之间的调度公平性。在调度算法提供的最小预留速率保证的基础上，采用流量调节模块的令牌桶算法，可以满足平均比特速率的要求。对于对时延和时延抖动非常敏感的实时业务，使用流量调节可以有效地保证时延和时延抖动需求。在网络负荷比较重的情况下，调度算法与准入控制算法结合起来实现对QoS的保证。
基于OPNET 11.0仿真平台，开发了WiMAX系统模块，对本文提出的方案进行了仿真和性能分析，验证了系统在提供多样化QoS支持、调度公平性、频谱效率、可扩展性方面的性能。
The next generation wireless metropolitan access network (WMAN) technology IEEE 802.16 d/e has defined a set of specifications to support quality of service (QoS) for heterogeneous services over wireless air interface. At the media access control (MAC) layer, it specifies scheduling services, service flow management, bandwidth request, polling, grant mechanisms and relevant signaling. However, it doesn't define QoS mapping, admission control, traffic adjustment and scheduling algorithms, which are open for developers. At the physical layer, IEEE 802.16 utilizes advanced techniques such as adaptive modulation and coding (AMC) to guarantee bit error rate (BER) of 1*10~(-6) . Due to the heterogeneous services over WMAN, as well as the dynamic variation of wireless transmission channel, the end-to-end QoS guarantee over 802.16 systems requires cooperation across layers, and consequently cross-layer design becomes critical in the future.
In this article, the author studies the existing QoS guarantee mechanisms and scheduling algorithms with QoS support, and proposes a cross-layer QoS guarantee and scheduling algorithm for 802.16 systems. The proposed scheme includes admission control module, uplink scheduling module, and AMC control module at the base station (BS), as well as traffic adjustment module, downlink scheduling module, and AMC selection module at the subscriber station (SS). The scheduling module adopts a two-layer scheduling algorithm based on priority. At the first layer, deficit fair priority queue (DFPQ) algorithm is utilized to schedule different service classes with fairness. At the second layer, according to the QoS requirements of UGS, rtPS, ertPS, nrtPS and BE services, as well as the current physical channel quality, a priority function (PRF) is assigned to each connection and dynamically updated. Thus, the connection with the highest priority is scheduled each time. AMC selection module periodically measures the wireless channel, updates the state transition matrix of finite-state Markov chain to trace the channel status, and dynamically selects transmission mode (TM), which includes modulation and forward error coding, so as to guarantee packet error rate (PER) performance and improve spectrum efficiency.
In the proposed cross-layer QoS architecture, each module collaborates to enhance end-to-end QoS support of WiMAX. AMC control module provides physical layer parameter normalized channel quality factor for scheduling module. Scheduling module assigns priority with fairness for each connection to satisfy diverse QoS requirements. Based on the minimum reserved rate provided by the scheduling algorithm, the token-bucket algorithm in the traffic adjustment module could satisfy the requirement of average bit rate. For real-time services which are sensitive to delay and delay jitter, traffic adjustment could guarantee their delay and delay jitter requirements. In the case of heavy load, scheduling algorithm collaborates with admission control to provide QoS guarantee.
With OPNET 11.0 simulator, WiMAX system modules are developed in order to simulate the schemes and algorithms in this article. The simulation result verifies the system performances on diverse QoS support, scheduling fairness, spectrum efficiency, and scalability.
本文基于现有的QoS保证机制和支持QoS的分组调度算法，研究和设计了基于802.16系统的跨层QoS保证和调度算法。在BS端，增加了准入控制模块、上行调度模块、AMC控制模块。在SS端，增加了流量调节模块、下行调度模块和AMC选择模块。调度模块采用了两层的基于优先级的综合调度算法。在第一层，采用逆差公平优先队列(DFPQ)算法，在不同连接类别之间调度，兼顾优先级和公平性。在第二层，根据UGS、rtPS、ertPS、nrtPS、BE业务的不同QoS需求特点和物理层当前信道特性，动态更新调度优先级函数(PRF)，在同一连接类别之间基于优先级进行调度。AMC选择模块周期性地测量无线信道，更新马尔可夫模型转移概率矩阵以跟踪当前的信道特征，动态选择物理层传输模式(包括调制方式和前项纠错编码方式)，在保证系统误包率(PER)要求的同时，最大可能地提高系统频谱效率。
本文的跨层QoS架构中，各功能模块通过协同运作，来增强WiMAX对端到端QoS的支持。其中，AMC控制模块为调度模块提供物理层参数归一化信道质量因子。调度模块为不同的连接分配合理的调度优先级，满足多样化业务的QoS需求，兼顾各类连接之间的调度公平性。在调度算法提供的最小预留速率保证的基础上，采用流量调节模块的令牌桶算法，可以满足平均比特速率的要求。对于对时延和时延抖动非常敏感的实时业务，使用流量调节可以有效地保证时延和时延抖动需求。在网络负荷比较重的情况下，调度算法与准入控制算法结合起来实现对QoS的保证。
基于OPNET 11.0仿真平台，开发了WiMAX系统模块，对本文提出的方案进行了仿真和性能分析，验证了系统在提供多样化QoS支持、调度公平性、频谱效率、可扩展性方面的性能。
The next generation wireless metropolitan access network (WMAN) technology IEEE 802.16 d/e has defined a set of specifications to support quality of service (QoS) for heterogeneous services over wireless air interface. At the media access control (MAC) layer, it specifies scheduling services, service flow management, bandwidth request, polling, grant mechanisms and relevant signaling. However, it doesn't define QoS mapping, admission control, traffic adjustment and scheduling algorithms, which are open for developers. At the physical layer, IEEE 802.16 utilizes advanced techniques such as adaptive modulation and coding (AMC) to guarantee bit error rate (BER) of 1*10~(-6) . Due to the heterogeneous services over WMAN, as well as the dynamic variation of wireless transmission channel, the end-to-end QoS guarantee over 802.16 systems requires cooperation across layers, and consequently cross-layer design becomes critical in the future.
In this article, the author studies the existing QoS guarantee mechanisms and scheduling algorithms with QoS support, and proposes a cross-layer QoS guarantee and scheduling algorithm for 802.16 systems. The proposed scheme includes admission control module, uplink scheduling module, and AMC control module at the base station (BS), as well as traffic adjustment module, downlink scheduling module, and AMC selection module at the subscriber station (SS). The scheduling module adopts a two-layer scheduling algorithm based on priority. At the first layer, deficit fair priority queue (DFPQ) algorithm is utilized to schedule different service classes with fairness. At the second layer, according to the QoS requirements of UGS, rtPS, ertPS, nrtPS and BE services, as well as the current physical channel quality, a priority function (PRF) is assigned to each connection and dynamically updated. Thus, the connection with the highest priority is scheduled each time. AMC selection module periodically measures the wireless channel, updates the state transition matrix of finite-state Markov chain to trace the channel status, and dynamically selects transmission mode (TM), which includes modulation and forward error coding, so as to guarantee packet error rate (PER) performance and improve spectrum efficiency.
In the proposed cross-layer QoS architecture, each module collaborates to enhance end-to-end QoS support of WiMAX. AMC control module provides physical layer parameter normalized channel quality factor for scheduling module. Scheduling module assigns priority with fairness for each connection to satisfy diverse QoS requirements. Based on the minimum reserved rate provided by the scheduling algorithm, the token-bucket algorithm in the traffic adjustment module could satisfy the requirement of average bit rate. For real-time services which are sensitive to delay and delay jitter, traffic adjustment could guarantee their delay and delay jitter requirements. In the case of heavy load, scheduling algorithm collaborates with admission control to provide QoS guarantee.
With OPNET 11.0 simulator, WiMAX system modules are developed in order to simulate the schemes and algorithms in this article. The simulation result verifies the system performances on diverse QoS support, scheduling fairness, spectrum efficiency, and scalability.
引文
[1] IEEE 802.16-2001, "IEEE Standard for Local and Metropolitan Area Networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems," Apr. 8, 2002.
[2] IEEE 802.16a-2003, "IEEE Standard for Local and Metropolitan Area Networks, Partl6: Air Interface for Fixed Broadband Wireless Access Systems - Amendment 2: Medium Access Control Modifications and Additional Physical Layer Specifications for 2-11 GHz," Apr. 1, 2003.
[3] IEEE Std 802.16~(TM)-2004, "IEEE Standard for Local and Metropolitan Area Networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems," Jun. 24, 2004.
[4] IEEE Std 802.16e~(TM)-2005 and IEEE Std 802.16~(TM)-2004/Cor1-2005, "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," Feb. 28, 2006.
[5] C. Eklund, R. B. Marks, K. L. Stanwood, and S. Wang, "IEEE standard 802.16: a technical overview of the wireless MAN~(TM) air interface for broadband wireless access," IEEE Communications Magazine, vol. 40, no. 6, pp. 98-107, Jun. 2002.
[6] 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, pp. 129-136, Feb. 2005.
[7] D-H. Cho, et al., "Performance analysis of the IEEE 802.16 wireless metropolitan area network," Proe. of the First International Conference on DFMA '05, pp. 130-137, 2005.
[8] M. Andrews, K. Kumaran, K. Ramanan, A. Stolyar, P. Whiting, and R. Vijayakumar, "Providing quality of service over a shared wireless link," IEEE Commun. Mag., vol. 39, no. 2, pp. 150-154, Feb. 2001.
[9] Taesoo Kwon, Howon Lee, Sik Choi, et al., "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 Commun. Mag,, pp. 136-146, Dec. 2005.
[10] Q. Liu, S. Zhou, and G. B. Giannakis, "Cross-layer combining of adaptive modulation and coding with truncated ARQ over wireless links," IEEE Trans. Wireless Commun., vol. 3, no. 5, pp. 1746-1755, Sep. 2004.
[11] Q. Liu, S. Zhou, and G. B. Giannakis, "Cross-layer modeling of adaptive wireless links for QoS support in multimedia networks," in Proc. 1st Int. Conf QShine, Dallas, TX,, Oct. 18-20, 2004, pp. 65-75.
[12] Q. Liu, S. Zhou, and G. B. Giannakis, "Queuing with adaptive modulation and coding over wireless links: cross-layer analysis and design," IEEE Trans. on Wireless Commun., 2005.
[13] K. Wongthavarawat and A. Ganz, "IEEE 802.16 based Last Mile Broadband Wireless Military Networks with Quality of Service Support," Proc. of MILCOM 2003, vol. 2, pp. 779-784, Oct. 2003.
[14] Jianfeng Chen, Wenhua Jiao, Qian Guo, "An Integrated QoS Control Architecture for IEEE 802.16 Broadband Wireless Access Systems," IEEE Globecom 2005, pp. 3330-3335, 2005.
[15] CuoSong Chu, Deng Wang, Shunliang Mei, "A QoS architecture for the MAC protocol of IEEE 802.16 BWA system," IEEE Communications, pp. 435-439, Jul. 2002.
[16] Qing Huang and Geng-sheng (G.S.) Kuo, "IEEE 802.16 Based QoS Architecture for Future Fixed Broadband Wireless Access System," WWRF 12, Toronto; Canada, Nov. 4-5, 2004.
[17] Yaxin Cao and Victor O. K. LI, "Scheduling algorithms in broad-band wireless networks," IEEE Proc. of the IEEE, vol. 89, no.1, pp. 76-87, Jan. 2001.
[18] H. Fattah and C. Leung, "An Overview of Scheduling Algorithms in Wireless Multimedia Networks," IEEE Wireless Communications, vol. 9, no. 5, pp. 76-83, Oct. 2002.
[19] S. Shakkottai and R. Srikant, "Scheduling real-time Traffic with Deadlines over a Wireless Channel," Proc. of ACM WOWMOM '99, Seattle, WA, pp. 35-42, 1999.
[20] Sun, J., Yanling Yao, Hongfei Zhu, "Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems," VTC 2006-Spring, vol. 3, pp. 1221-1225.
[21] M. Ergen, S. Coleri, P. Varaiya, "QoS Aware Adaptive Resource Allocation Techniques for Fair Scheduling in OFDMA Based Broadband Wireless Access Systems," IEEE Transactions on Broadcasting, vol. 49, Dec. 2003.
[22] K. Wongthavarawat, and A. Ganz, "Packet Scheduling for QoS Support in IEEE 802.16 Broadband Wireless Access Systems," International Journal of Communication Systems, vol. 16, pp. 81-96, 2003.
[23] Jianfeng Chen, Wenhua Jiao, Hongxi Wang, "A Service Flow Management Strategy for IEEE 802.16 Broadband Wireless Access Systems in TDD Mode," ICC 2005, vol. 5, pp. 3422-3426, May 16-20, 2005.
[24] D. Niyato, J. Diamond and E. Hossain, "On optimizing token bucket parameters at the network edge under generalized processor sharing (GPS) scheduling," IEEE GLOBECOM2005, vol. 2, pp. 683-687, Nov. 2005.
[25] Puqi Perry Tang and T. Y. C Tai, "Network traffic characterization using token bucket model," INFOCOM 99, vol. 1, pp. 51-62, Mar. 1999.
[26] S. Falahati, A. Svensson, T. Ekman, and M. Stemad, "Adaptive modulation systems for predicted wireless channels," IEEE Trans. Commun., vol. 52, no. 2, pp. 307-316, Feb. 2004.
[27] Lei Ming, Zhang Ping, H. Haas and E. Costa, "Performance analysis of an adaptive modulation system over Nakagami-m fading Channels," VTC Spring 2002, vol. 3, pp. 1527-1531, May. 2002.
[28] R. Kwan and C. Leung, "Adaptive modulation and coding with multicodes over Nakagami fading channels," WCNC 2005, vol. 2, pp. 927-932, Mar. 2005.
[29] M.S. Alouini, X.Tang and A.Goldsmith, "An adaptive modulation scheme for simultaneous voice and data transmission over fading channels," VTC 98, vol. 2, pp. 939-943, May. 1998.
[30] H. S. Wang and N. Moayeri, "Finite-state Markov Channel - A useful model for radio communication channels," IEEE Trans. Veh. Technol., vol. 44, no. 1, pp. 163-171, Feb. 1995.
[2] IEEE 802.16a-2003, "IEEE Standard for Local and Metropolitan Area Networks, Partl6: Air Interface for Fixed Broadband Wireless Access Systems - Amendment 2: Medium Access Control Modifications and Additional Physical Layer Specifications for 2-11 GHz," Apr. 1, 2003.
[3] IEEE Std 802.16~(TM)-2004, "IEEE Standard for Local and Metropolitan Area Networks, Part 16: Air Interface for Fixed Broadband Wireless Access Systems," Jun. 24, 2004.
[4] IEEE Std 802.16e~(TM)-2005 and IEEE Std 802.16~(TM)-2004/Cor1-2005, "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," Feb. 28, 2006.
[5] C. Eklund, R. B. Marks, K. L. Stanwood, and S. Wang, "IEEE standard 802.16: a technical overview of the wireless MAN~(TM) air interface for broadband wireless access," IEEE Communications Magazine, vol. 40, no. 6, pp. 98-107, Jun. 2002.
[6] 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, pp. 129-136, Feb. 2005.
[7] D-H. Cho, et al., "Performance analysis of the IEEE 802.16 wireless metropolitan area network," Proe. of the First International Conference on DFMA '05, pp. 130-137, 2005.
[8] M. Andrews, K. Kumaran, K. Ramanan, A. Stolyar, P. Whiting, and R. Vijayakumar, "Providing quality of service over a shared wireless link," IEEE Commun. Mag., vol. 39, no. 2, pp. 150-154, Feb. 2001.
[9] Taesoo Kwon, Howon Lee, Sik Choi, et al., "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 Commun. Mag,, pp. 136-146, Dec. 2005.
[10] Q. Liu, S. Zhou, and G. B. Giannakis, "Cross-layer combining of adaptive modulation and coding with truncated ARQ over wireless links," IEEE Trans. Wireless Commun., vol. 3, no. 5, pp. 1746-1755, Sep. 2004.
[11] Q. Liu, S. Zhou, and G. B. Giannakis, "Cross-layer modeling of adaptive wireless links for QoS support in multimedia networks," in Proc. 1st Int. Conf QShine, Dallas, TX,, Oct. 18-20, 2004, pp. 65-75.
[12] Q. Liu, S. Zhou, and G. B. Giannakis, "Queuing with adaptive modulation and coding over wireless links: cross-layer analysis and design," IEEE Trans. on Wireless Commun., 2005.
[13] K. Wongthavarawat and A. Ganz, "IEEE 802.16 based Last Mile Broadband Wireless Military Networks with Quality of Service Support," Proc. of MILCOM 2003, vol. 2, pp. 779-784, Oct. 2003.
[14] Jianfeng Chen, Wenhua Jiao, Qian Guo, "An Integrated QoS Control Architecture for IEEE 802.16 Broadband Wireless Access Systems," IEEE Globecom 2005, pp. 3330-3335, 2005.
[15] CuoSong Chu, Deng Wang, Shunliang Mei, "A QoS architecture for the MAC protocol of IEEE 802.16 BWA system," IEEE Communications, pp. 435-439, Jul. 2002.
[16] Qing Huang and Geng-sheng (G.S.) Kuo, "IEEE 802.16 Based QoS Architecture for Future Fixed Broadband Wireless Access System," WWRF 12, Toronto; Canada, Nov. 4-5, 2004.
[17] Yaxin Cao and Victor O. K. LI, "Scheduling algorithms in broad-band wireless networks," IEEE Proc. of the IEEE, vol. 89, no.1, pp. 76-87, Jan. 2001.
[18] H. Fattah and C. Leung, "An Overview of Scheduling Algorithms in Wireless Multimedia Networks," IEEE Wireless Communications, vol. 9, no. 5, pp. 76-83, Oct. 2002.
[19] S. Shakkottai and R. Srikant, "Scheduling real-time Traffic with Deadlines over a Wireless Channel," Proc. of ACM WOWMOM '99, Seattle, WA, pp. 35-42, 1999.
[20] Sun, J., Yanling Yao, Hongfei Zhu, "Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems," VTC 2006-Spring, vol. 3, pp. 1221-1225.
[21] M. Ergen, S. Coleri, P. Varaiya, "QoS Aware Adaptive Resource Allocation Techniques for Fair Scheduling in OFDMA Based Broadband Wireless Access Systems," IEEE Transactions on Broadcasting, vol. 49, Dec. 2003.
[22] K. Wongthavarawat, and A. Ganz, "Packet Scheduling for QoS Support in IEEE 802.16 Broadband Wireless Access Systems," International Journal of Communication Systems, vol. 16, pp. 81-96, 2003.
[23] Jianfeng Chen, Wenhua Jiao, Hongxi Wang, "A Service Flow Management Strategy for IEEE 802.16 Broadband Wireless Access Systems in TDD Mode," ICC 2005, vol. 5, pp. 3422-3426, May 16-20, 2005.
[24] D. Niyato, J. Diamond and E. Hossain, "On optimizing token bucket parameters at the network edge under generalized processor sharing (GPS) scheduling," IEEE GLOBECOM2005, vol. 2, pp. 683-687, Nov. 2005.
[25] Puqi Perry Tang and T. Y. C Tai, "Network traffic characterization using token bucket model," INFOCOM 99, vol. 1, pp. 51-62, Mar. 1999.
[26] S. Falahati, A. Svensson, T. Ekman, and M. Stemad, "Adaptive modulation systems for predicted wireless channels," IEEE Trans. Commun., vol. 52, no. 2, pp. 307-316, Feb. 2004.
[27] Lei Ming, Zhang Ping, H. Haas and E. Costa, "Performance analysis of an adaptive modulation system over Nakagami-m fading Channels," VTC Spring 2002, vol. 3, pp. 1527-1531, May. 2002.
[28] R. Kwan and C. Leung, "Adaptive modulation and coding with multicodes over Nakagami fading channels," WCNC 2005, vol. 2, pp. 927-932, Mar. 2005.
[29] M.S. Alouini, X.Tang and A.Goldsmith, "An adaptive modulation scheme for simultaneous voice and data transmission over fading channels," VTC 98, vol. 2, pp. 939-943, May. 1998.
[30] H. S. Wang and N. Moayeri, "Finite-state Markov Channel - A useful model for radio communication channels," IEEE Trans. Veh. Technol., vol. 44, no. 1, pp. 163-171, Feb. 1995.