光纤同轴混合网上行信道共享技术改进方法研究
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摘要
随着传统有线电视网络及其设备双向改造的完成， HFC（Hybrid fiber coax），即光纤同轴混合网已成为向用户提供双向宽带综合业务的重要途径。为了兼容传统的有线电视传输模式，HFC网络带宽首先被频分为若干个8 MHZ的频道，这些频道被统一划分为下行和上行信道。上行频带位于5-65MHZ之间，这一频带为高频（HF）和甚高频（VHF）的一部分，此频带易受噪声干扰；此外，由于从光节点到用户端为树型分支结构，同一光节点的多个用户共享同一信道，形成了漏斗效应。因此，上行信道具有频带窄，噪声大的特征，这一特征对上行信道的数据传输具有极大的影响。HFC网络下行信道采用一点对多点的广播方式，用户共享下行资源实现比较简单。上行信道是一个多点对一点的媒体共享信道。所以，目前局域网使用的媒体接入控制MAC协议如：CSMA/CD、令牌等，不适用于HFC网。因此，解决上行信道的噪声问题和上行资源共享是HFC网络能否成为一个多媒体业务通信平台的关键技术之一。
目前，很多国际化组织已经针对HFC网络接入双向业务制定了一系列规范。其中最有影响的是IEEE802.14工作组制定的IEEE802.14标准和MCNS提出的DOCSIS规范。前者侧重于ATM信元的传输，提供了完善的QOS支持；后者侧重于变长IP数据包的传输，在DOCSIS V1.1中提出了QOS的概念。无论是IEEE802.14还是DOCSIS两者MAC层协议的设计重点都放在上行信道上，即上行信道的分配，服务调度以及冲突解决等。
本文结合当前HFC网络中主要MAC层协议的设计思想从本质上分析了影响协议性能的关键因素，结合上行信道的利用率和数据传输延时这两方面的性能从理论上分析了 HFC网络上行信道的传输机制，并对分析结果进行了仿真。在此基础上提出基于ALOHA与S-CDMA的HFC网络上行资源共享技术，并在理论上对其①抗干扰能力、②上行信道利用率、③传输延时等方面作了详细的分析。证明了新型的基于ALOHA与S-CDMA上行资源共享技术的HFC网络的性能要优于传统的基于TDMA技术的HFC网络。
With the development of conventional CATV system and the completion of its equipment's tow-direction upgrading， HFC（Hybrid Fiber Coax）has become an important way to provide the two-direction integrating broadband service to users. To make itself compatible the transmission mode of the conventional CATV system, the bandwidth of HFC system is divided into many 8MHz channels, which include downstream and upstream channels. Upstream channels cover in 5～65MHz, which is a part of the bandwidth of high frequency（HF）and very high frequency（VHF）. It is liable to incur noises ingress onto the band. Since HFC system has the tree-and-branch topology between the fiber-node and subscriber units, subscriber units belonging to one fiber-node share the same upstream channel , forming the "noise funneling" effect. So the upstream channel has the character of narrower bandwidth and bigger noise. This character has a big influence on data transmission on the upstream channels. The downstream channel is a point-to-multipoint broadcasting channel with a wider bandwidth, while the upstream one is a multipoint-to-point share medium with a narrow bandwidth. So these popular medium access control protocols as CSMA/CD, Token-ring etc. are not suitable for HFC system. Therefore to solve the noises in the upstream channel and to share the sources of the upstream channels becomes one of the key technologies for HFC system to become a multimedia communication platform.
Up to now, many international organizations have formed some specification to access the tow-direction services of HFC system. What is important is that the IEEE802.14 specification laid down by IEEE802.14 working group and DOCSIS made by MCNS (multimedia cable network system). The former one is related to the transmission of the ATM cell and to offer the perfection QOS(quality of service); the latter is related to the transmission of the length-variable IP data pack. The concept of the QOS appears in the DOCSIS v1.1 . Both IEEE802.14 and DOCSIS, focus in MAC protocol design on the upstream channels, i.e. sharing the upstream channels , dealing the services and resolving the contention.
This dissertation gives theoretical analysis of the main factors that affect these performances of a MAC protocol, based on most popular designs. This dissertation presents a new technology that based on ALOHA and S-CDMA and theoretically analyzed the character of HFC system which use the new technology, such as the
capacity of interference resisting, improving the bandwidth utility and lowering the access time delay. finally this dissertation gives demonstration that HFC system which use the new technology, is better than that using the conventional TDMA technology.
目前，很多国际化组织已经针对HFC网络接入双向业务制定了一系列规范。其中最有影响的是IEEE802.14工作组制定的IEEE802.14标准和MCNS提出的DOCSIS规范。前者侧重于ATM信元的传输，提供了完善的QOS支持；后者侧重于变长IP数据包的传输，在DOCSIS V1.1中提出了QOS的概念。无论是IEEE802.14还是DOCSIS两者MAC层协议的设计重点都放在上行信道上，即上行信道的分配，服务调度以及冲突解决等。
本文结合当前HFC网络中主要MAC层协议的设计思想从本质上分析了影响协议性能的关键因素，结合上行信道的利用率和数据传输延时这两方面的性能从理论上分析了 HFC网络上行信道的传输机制，并对分析结果进行了仿真。在此基础上提出基于ALOHA与S-CDMA的HFC网络上行资源共享技术，并在理论上对其①抗干扰能力、②上行信道利用率、③传输延时等方面作了详细的分析。证明了新型的基于ALOHA与S-CDMA上行资源共享技术的HFC网络的性能要优于传统的基于TDMA技术的HFC网络。
With the development of conventional CATV system and the completion of its equipment's tow-direction upgrading， HFC（Hybrid Fiber Coax）has become an important way to provide the two-direction integrating broadband service to users. To make itself compatible the transmission mode of the conventional CATV system, the bandwidth of HFC system is divided into many 8MHz channels, which include downstream and upstream channels. Upstream channels cover in 5～65MHz, which is a part of the bandwidth of high frequency（HF）and very high frequency（VHF）. It is liable to incur noises ingress onto the band. Since HFC system has the tree-and-branch topology between the fiber-node and subscriber units, subscriber units belonging to one fiber-node share the same upstream channel , forming the "noise funneling" effect. So the upstream channel has the character of narrower bandwidth and bigger noise. This character has a big influence on data transmission on the upstream channels. The downstream channel is a point-to-multipoint broadcasting channel with a wider bandwidth, while the upstream one is a multipoint-to-point share medium with a narrow bandwidth. So these popular medium access control protocols as CSMA/CD, Token-ring etc. are not suitable for HFC system. Therefore to solve the noises in the upstream channel and to share the sources of the upstream channels becomes one of the key technologies for HFC system to become a multimedia communication platform.
Up to now, many international organizations have formed some specification to access the tow-direction services of HFC system. What is important is that the IEEE802.14 specification laid down by IEEE802.14 working group and DOCSIS made by MCNS (multimedia cable network system). The former one is related to the transmission of the ATM cell and to offer the perfection QOS(quality of service); the latter is related to the transmission of the length-variable IP data pack. The concept of the QOS appears in the DOCSIS v1.1 . Both IEEE802.14 and DOCSIS, focus in MAC protocol design on the upstream channels, i.e. sharing the upstream channels , dealing the services and resolving the contention.
This dissertation gives theoretical analysis of the main factors that affect these performances of a MAC protocol, based on most popular designs. This dissertation presents a new technology that based on ALOHA and S-CDMA and theoretically analyzed the character of HFC system which use the new technology, such as the
capacity of interference resisting, improving the bandwidth utility and lowering the access time delay. finally this dissertation gives demonstration that HFC system which use the new technology, is better than that using the conventional TDMA technology.
引文
[1] 李杰，HFC技术及宽带接入中的应用，工程设计CAD及智能建筑，2002年5月 第5期
[2] 张瑞武，智能建筑的系统集成及工程实施，北京，清华大学出版社，2000年8月
[3] D.Rauschmayer，ADSL/VDSL Principles：A practical and precise study of Digital subscriber Lines and Very High Speed Digital Subscriber Lines，Macmmillan technical publishing(1998)
[4] Albert Azzam，文爱军（译），宽带接入技术，北京，电子工业出版社，2001年7月
[5] 陈惠芳，HFC上行资源预约申请多址接入的性能分析，通信学报，2001年第8期
[6] 刘思亮，电缆电视技术，北京，建筑工业出版社，1998年5月
[7] 有线电视广播系统规范GY/T106－1999
[8] 陕西省广播电视局，现代广播电视网络技术及其应用，西安，西安电子科技大学出版社，2001年11月
[9] 李鉴增，有线电视综合信息网技术，北京，人民邮电出版社，1999
[10] C.A.Eldering, N.Himayat and F.C.Gardner，CATV Return Path Characterization for Reliable
Communications，IEEE Communications Magazione 8，1995
[11] CableLabs，Data-Over-Cable Service Interface Specifications(DOCSIS)：Radio Frequency Interface Specification，version 1.0 ,1997
[12] 黄孝建，有线电视、交互电视与多媒体宽带接入，北京，人民邮电出版社，1999
[13] 刘政林，HFC网络上行信道噪声对通信的影响及其对策，电视技术，2001年第5期
[14] CableLabs，Data-Over-Cable Service Interface Specifications(DOCSIS)：Radio Frequency Interface Specification，SP-RFI v1.1-I02-990731，1999
[15] Stephen Perkins，Tow-ways Broadband CATV-HFC networks：state-of-the-art and future trends，Computer Networks 31(1999)313-326
[16] 石进，HFC网中的信道共享技术，重庆大学学报（自然科学版），2002年第3期
[17] Albert Azzam（美），高速电缆调制解调器，北京，电子工业出版社，1999
[18] 周明天，TCP/IP网络原理与技术，北京，清华大学出版社，1993
[19] IEEE 802.14 Working Group，IEEE Standard 802.14，Draft 3 Revision 1[s]，1998
[20] Yin W M，Lin Y D，Statistically Optionizaed minislot allocation for initial and collision resolution in fiber coaxial networks[J]，IEEE Journal on Selected Areas in Communications，2000，18（9）
[21] Lin Y D，Allocation and Scheduling algorithm for IEEE 802.14 and MCNS in hybrid fiber coaxial networks[J]，IEEE Transactions on Broadcasting，1998，44（4）:427-435
[22] Golmie N，Saintillan Y，A Review of contention resolution algorithms for IEEE802.14 networks[DB/OL]，http://www.comsoc.org/pub/survey
[23] Sala D，Limb J O，Comparison of contention resolution algorithms for a cable modem MAC Protocol[R]，International Lurich Seminar on Broadband Communications，Inrich，Switzerland，1998
[24] J O Limb，D Sala，A Protocol for efficient transfer of data over fiber coax system[J]，IEEE Trans on networking，December 1997
[25] 张跷学，计算机网络与Internet教程，北京，清华大学出版社，1999
[26] Digital Audio-Visual council.，Lower Layer Protocol and Physical Interface，DAVIC 1.2 Specification part 8(1999)
[27] 刘锦德，计算机网络大全，北京，电子工业出版社，1997
[28] 扬东生，码分多址在HFC网中的应用，电视技术，2000年第11期
[29] 郭梯云，数字移动通信，北京，人民邮电出版社，1995
[30] R P C Wolter，An initialization Protocol for a CDMA based communications scheme for HFC networks[J]，IEEE.Trans，september 1997，43（3）：329-338
[31] Andrew J Viter，CDMA：Principles of spread Spectrum Communication[M]，Addison-Wesley Publish Company，1995
[32] Y.L.C de Jong，A CDMA based bi-directional Communication System for hybrid-coax CATV networks[J]，IEEE Trans on Broadcasting，1997，43（6）：127-135
[33] B.Sklar，Digital Communications Fundamentals an Applications，PTR Prentice Hall，Engle wood Cliffs（1998）
[2] 张瑞武，智能建筑的系统集成及工程实施，北京，清华大学出版社，2000年8月
[3] D.Rauschmayer，ADSL/VDSL Principles：A practical and precise study of Digital subscriber Lines and Very High Speed Digital Subscriber Lines，Macmmillan technical publishing(1998)
[4] Albert Azzam，文爱军（译），宽带接入技术，北京，电子工业出版社，2001年7月
[5] 陈惠芳，HFC上行资源预约申请多址接入的性能分析，通信学报，2001年第8期
[6] 刘思亮，电缆电视技术，北京，建筑工业出版社，1998年5月
[7] 有线电视广播系统规范GY/T106－1999
[8] 陕西省广播电视局，现代广播电视网络技术及其应用，西安，西安电子科技大学出版社，2001年11月
[9] 李鉴增，有线电视综合信息网技术，北京，人民邮电出版社，1999
[10] C.A.Eldering, N.Himayat and F.C.Gardner，CATV Return Path Characterization for Reliable
Communications，IEEE Communications Magazione 8，1995
[11] CableLabs，Data-Over-Cable Service Interface Specifications(DOCSIS)：Radio Frequency Interface Specification，version 1.0 ,1997
[12] 黄孝建，有线电视、交互电视与多媒体宽带接入，北京，人民邮电出版社，1999
[13] 刘政林，HFC网络上行信道噪声对通信的影响及其对策，电视技术，2001年第5期
[14] CableLabs，Data-Over-Cable Service Interface Specifications(DOCSIS)：Radio Frequency Interface Specification，SP-RFI v1.1-I02-990731，1999
[15] Stephen Perkins，Tow-ways Broadband CATV-HFC networks：state-of-the-art and future trends，Computer Networks 31(1999)313-326
[16] 石进，HFC网中的信道共享技术，重庆大学学报（自然科学版），2002年第3期
[17] Albert Azzam（美），高速电缆调制解调器，北京，电子工业出版社，1999
[18] 周明天，TCP/IP网络原理与技术，北京，清华大学出版社，1993
[19] IEEE 802.14 Working Group，IEEE Standard 802.14，Draft 3 Revision 1[s]，1998
[20] Yin W M，Lin Y D，Statistically Optionizaed minislot allocation for initial and collision resolution in fiber coaxial networks[J]，IEEE Journal on Selected Areas in Communications，2000，18（9）
[21] Lin Y D，Allocation and Scheduling algorithm for IEEE 802.14 and MCNS in hybrid fiber coaxial networks[J]，IEEE Transactions on Broadcasting，1998，44（4）:427-435
[22] Golmie N，Saintillan Y，A Review of contention resolution algorithms for IEEE802.14 networks[DB/OL]，http://www.comsoc.org/pub/survey
[23] Sala D，Limb J O，Comparison of contention resolution algorithms for a cable modem MAC Protocol[R]，International Lurich Seminar on Broadband Communications，Inrich，Switzerland，1998
[24] J O Limb，D Sala，A Protocol for efficient transfer of data over fiber coax system[J]，IEEE Trans on networking，December 1997
[25] 张跷学，计算机网络与Internet教程，北京，清华大学出版社，1999
[26] Digital Audio-Visual council.，Lower Layer Protocol and Physical Interface，DAVIC 1.2 Specification part 8(1999)
[27] 刘锦德，计算机网络大全，北京，电子工业出版社，1997
[28] 扬东生，码分多址在HFC网中的应用，电视技术，2000年第11期
[29] 郭梯云，数字移动通信，北京，人民邮电出版社，1995
[30] R P C Wolter，An initialization Protocol for a CDMA based communications scheme for HFC networks[J]，IEEE.Trans，september 1997，43（3）：329-338
[31] Andrew J Viter，CDMA：Principles of spread Spectrum Communication[M]，Addison-Wesley Publish Company，1995
[32] Y.L.C de Jong，A CDMA based bi-directional Communication System for hybrid-coax CATV networks[J]，IEEE Trans on Broadcasting，1997，43（6）：127-135
[33] B.Sklar，Digital Communications Fundamentals an Applications，PTR Prentice Hall，Engle wood Cliffs（1998）