Short answer 1. This paper briefly introduces three mainstream access schemes for two-way transformation of radio and television metropolitan area network access network, and compares their advantages

Short answer 1. This paper briefly introduces three mainstream access schemes for two-way transformation of radio and television metropolitan area network access network, and compares their advantages and disadvantages. Three mainstream access schemes: 1, EOC；; 2、CMTS； 3. Lan

Key points:

In the two-way transformation, the primary task facing radio and television is to speed up the digital upgrade of radio and television network. In choosing the technology of two-way transformation, what radio and television network access operators need to do is to find a suitable way among many two-way network transformation schemes. (The one on the right is the best)

Summarize three mainstream access technologies in two-way transformation of radio and television in one sentence: EOC needs standardization, CMTS needs cheaper, and LAN needs access rate.

Specifically, you can see:

The so-called "triple play" means that the telecommunication network, cable TV network and computer communication network penetrate and are compatible with each other, and gradually merge into a unified information communication network all over the world. "Triple play" is to share network resources, avoid low-level redundant construction, and form a high-speed broadband multimedia infrastructure platform with wide adaptability, easy maintenance and low cost. Its performance is that the technology tends to be consistent, the network layer can be interconnected to form seamless coverage, the business layer penetrates and crosses each other, the application layer tends to use a unified IP protocol, the business competes and cooperates with each other, and gradually converges to the same goal of providing diversified, multimedia and personalized services to human beings, and the industry supervision and policies also tend to be unified.

With the start of triple play, the most important task of radio and television is to speed up the digital upgrading of cable TV network and the construction of the next generation radio and television network. In this process, the radio and television network needs to adopt a large number of two-way transformation technologies, so as to ensure that radio and television can gain an advantage in the competition of triple play.

meaning

It not only effectively integrates and interconnects the existing network resources, but also forms a new service and operation mechanism, which is conducive to the optimization of the information industry structure and the corresponding changes in policies and regulations. After the integration, not only the information dissemination mode, content and communication service will change greatly, but also the specific forms of enterprise application and personal information consumption will change qualitatively.

The integration of the three networks will fundamentally change the ways and means of the preservation, management, dissemination and utilization of traditional cultural information resources in China, and create a good environment for knowledge innovation and the construction of two civilizations to absorb cultural information.

Judging from the triple play policy issued by the State Council, from 20 13 to 20 15, the pilot experience was summarized and popularized, the triple play development was fully realized, and the application of converged services was popularized, thus basically forming a moderately competitive network industry pattern.

Two years later, according to the pilot policy of the State Council, the integration of the three networks will be fully promoted throughout the country. How tight will the time be for the digital upgrade of radio and television networks?

At present, on the whole, there are still a large number of HFC networks in China's radio and television network, and most of them have not completed the two-way transformation. This kind of network can only meet the basic transmission of radio and television programs, and can neither carry multimedia interactive services nor effectively realize network, business and user management. Therefore, the first task facing radio and television is to change HFC network from one-way network to two-way network.

HFC is an economical and practical broadband network access technology for integrated digital services. At present, the cable TV network has more than 940 million users worldwide. Since the early 1990s, the national coverage of China cable TV network has reached 50%, with more than 80 million TV households, making it the largest cable TV network in the world. With the rapid development of computer technology, communication technology, network technology, cable TV technology and multimedia technology, especially under the impetus of the Internet, users put forward new requirements for information exchange and network transmission, and the voice of integrating cable TV network, computer network and telecommunication network is getting higher and higher. The scheme of establishing an economical and practical broadband integrated information service network by using HFC network structure also came into being.

This is conducive to enhancing the network value, competitiveness, service quality and income of radio and television in the competition of triple play. The effectiveness of network transformation is also reflected in the improvement of social and economic benefits of the network. Another purpose of network reform is to cope with the increasingly fierce and even cruel competition: to avoid the loss of users and enhance the service ability of multi-service and full-service, so as to improve the social and economic benefits of network services.

So in the current situation of two-way transformation of radio and television networks, which mainstream access technologies do radio and television departments and most services use?

1、EOC

The concept of 1. 1 and EOC

Active EOC

At present, there are many technologies and solutions to transmit Ethernet signals through coaxial cables after complex processing such as modulation and demodulation. Although some people call it "Ethernet? Over Coax ",but it is very different from real EoC (baseband EoC/ passive EoC). The signal transmitted on coaxial cable no longer keeps the frame format of Ethernet signal, so it can't be called "EoC" technically. There are mainly the following technologies: HomePNAover Coax, HomePlug BPL over Coax, HomePlugAV over Coax, WiFi over Coax, moca-multimedia over Coax alliance, which we call "active EoC" or "modulated EoC" for the time being.

HomePNA, HomePlug BPL, HomePlugAV and WiFi (wireless local area network, wireless fidelity) are all mature home networking technologies, which have been developed for several years. MoCA is a networking technology based on coaxial cable introduced by coaxial cable multimedia alliance, and it is the youngest of the four technologies. HiNOC is a new standard EOC technology in China market recently, and it is also a technology specifically for coaxial cable, but there is no commercial chip yet.

Passive EoC

Passive EoC (Ethernetover Coax) technology is based on a series of protocols related to IEEE 802.3, and it is a transmission technology for transmitting Ethernet signals on coaxial cables. The frame format and MAC layer of the original Ethernet signal have not changed, but it will be converted from differential balanced signal (twisted pair medium) to unbalanced signal (coaxial cable medium). Its biggest feature is that the client is a passive device. Baseband coaxial transmission system occupies 0-65MHz frequency band and provides users with 10M bandwidth. Using high-low pass filtering, all passive devices are used to realize coaxial transmission of data and CATV signals. The system needs to change the original balanced Ethernet signal into unbalanced transmission, and combine the Ethernet transceiver signals into one signal to complete the impedance transformation of100Ω/75Ω. Baseband EOC technology is to combine Ethernet data signal, IP data and cable TV signal? Radio frequency adopts frequency division multiplexing technology, so that these two signals can be transmitted on the same coaxial cable. According to the old national standard of cable TV network frequency division in China, IP data signals can be transmitted in the frequency band below 35MHz, and TV radio frequency signals can be transmitted in the frequency band above 48MHz, which can realize * * * wired transmission of the two signals without affecting each other, or according to the division point of the new national standard 65/87, EOC built-in filter is easy to mass-produce. In the building, the mixed signal of IP data and TV radio frequency is directly transmitted to the user by using the coaxial cable of HFC network, and then the passive separation of the mixed signal is realized at the user. Passive EOC needs to combine Ethernet signals with CATV signals above 86MHz through a duplex filter, and needs high isolation, high return loss and as low insertion loss as possible to effectively suppress the stray signals generated by Ethernet. At the same time, the filter will produce phase nonlinearity, so it is necessary to equalize the group delay. Therefore, the requirements for signal indicators and product technology are very high, otherwise the signal will be easily blocked. Because the energy of passive EOC is mainly concentrated in 0 to 20MHz, and the bandwidth of branch distributor is generally 5 to 1000MHz, passive EOC cannot pass through the branch distributor.

EoC (Ethernet over coax) is a technology used to transmit Ethernet data signals over coaxial cables. The broadband data signal transmitted from the computer room to the community or building is mainly transmitted to users through cables to meet the high bandwidth demand brought by the development of multi-service at the user end.

According to DVBCN, EoC can be divided into baseband and modulation transmission modes according to data signals, namely baseband EoC and modulation EoC.

Baseband EoC is usually a passive device. Based on a series of protocols related to IEEE 802.3, it uses frequency division multiplexing technology to transmit data signals and cable TV signals on the same coaxial cable. Suitable for concentrated distribution in residential areas. Generally speaking, data signals must go to the corridor. Therefore, baseband EoC technology can not be applied to the ubiquitous tree network in the network.

Modulation EoC modulates the Ethernet signal to a certain frequency band at the head end by using orthogonal frequency division multiplexing (OFDM) and other technologies, and then couples it to the coaxial cable for transmission. At the user end, the signal modulated on the coaxial cable is demodulated and restored to baseband signal to provide services to users through Ethernet interface. At the same time, the user's return signal is modulated and loaded on the wired network and transmitted to the head end, that is, the process of transmitting Ethernet signals through coaxial cable is realized. Due to the advanced and efficient modulation method and error detection technology, the physical layer rate far exceeds the bandwidth that passive EoC can provide, which will provide strong support for the high-bandwidth access needs of future users. Modulated EoC system can overcome the shortcomings of baseband EoC, and has the advantages of long transmission distance, spanning amplifiers and branch distributors, high bandwidth, supporting QoS and centralized network management. The modulation EoC can be subdivided into many technologies, such as MoCA, HomePNA, HomePlug, Wi-Fi and so on.

1.2, EOC standard has not been established.

EoC system, as the last wired transmission technology of FTTC, FTTB or FTTX, can use the optical transceiver and terminal ONU of PON as uplink convergence devices. From the networking mode, it is similar to the application of CMTS in CATV network, except that the head-end equipment of CMTS is adopted below the community to conform to the network development trend of "light enters copper and retreats". Moreover, from an economic point of view, the price of modulation EoC technology is much lower than that of CMTS technology.

However, one of the problems existing in EoC at present is that its technology is still developing, and there are still many technologies competing in the market, and the price is still relatively high. What kind of technology is leading needs to be judged in practice.

In the view of DVBCN reporters, baseband EOC can only be used for centralized distribution networks. When the 4\\2 line conversion circuit is empty, the switch will loop back and collapse, leaving only a few dB for the network card; EOC-like modulation technology has low maturity and the market is extremely chaotic. The disadvantage of low frequency modulation class is that it is greatly affected by noise. The disadvantage of high frequency modulation is high transmission loss and high sensitivity, but the signal-to-noise ratio is poor when the level is too small, and the throughput will decrease. In addition, due to the bandwidth sharing mechanism, it is not suitable for high-bandwidth services such as IPTV.

There are still some problems in the application of 1.3 and EOC.

In the application of EOC, Dr. Yu, a radio and television expert, replied to the DVBCN reporter that there are still some problems in the application of EOC in China:

First of all, many EOC application scenarios are either used for broadband Internet access or video transmission through IPQAM, so there is no requirement for EOC delay and jitter. Therefore, the present application cannot fully reflect NGB's future demand for the Equal Opportunities Commission.

Second, the application evaluation of EOC can not be judged only by quantity. It should be judged from the actual application scenario. What is our application scenario? What do we need? These are the same as the establishment of the HINOC standard, which requires establishing a model first and then judging. It is suggested that the science and technology department or the planning institute find some suitable people to participate in the model establishment. Without demand, there is no standard for judging, and without model, there is no basis for judging. Without systematic judgment, there is no correct judgment.

Third, the investigation and evaluation of EOC demand model. It is also necessary to establish actual test specifications or determine actual indicators. With NGB, we know what kind of bandwidth is needed, 20m = = 40m. So, what kind of delay and jitter do we need to transmit video? Therefore, the establishment of the model is the key to establish the test specification in the future. Is the basis of correct judgment.

1.4, application of EOC+EPON technical scheme

At present, there are two mainstream schemes for two-way network transformation, one is the two-way transformation scheme based on HFC network (CM scheme), and the other is a new scheme proposed in recent two years, namely EPON to the building++EoC technical scheme.

Triple play, with the deepening of the transformation of radio and television two-way network, according to DVBCN, most radio and television operators in the industry are more respectful of EPON+EOC technical solutions.

From the investment cost of two-way transformation: Dr. Hu of Wuhan Changguang told DVBCN that when EPON+EOC is selected as two-way transformation, this technology has certain advantages in terms of home bandwidth and average home coverage cost, compared with EPON+LAN and EPON+EoC(EoC takes HomePlug AV as an example). For example, with 30% access rate and 2M access bandwidth, the average coverage cost of CMTS is 9 1 1 yuan, EPON+LAN is 128 yuan, and EPON+EoC is only in 54 yuan; 10% access rate, 1M access bandwidth, average coverage cost of CMTS 16 1 yuan, EPON+LAN 128 yuan, EPON+EoC only in 29 yuan.

Judging from the speed and difficulty of two-way transformation, Dr. Hu believes that it is difficult, fast and low in cost to use this technology in EPON+EoC two-way network transformation; And "CMTS technology is mature but the bandwidth cost is high; EPON+LAN faces many problems, such as difficult network transformation, high coverage cost when the access rate is low, corridor switch management and so on.

From the perspective of effective utilization of two-way transformation resources, Alcatel-Lucent, in an interview with DVCBN, believes that EPON+EOC scheme can be adopted in the process of triple play to NGB, which can effectively utilize the rich HFC resources of radio and television operators, reduce the investment in network transformation, and realize efficient comprehensive bearing of video, data and voice. Mainstream technologies such as HomePlug AV/BPL and HomePNA adopted in EPON+EOC scheme have also been widely used.

2、CMTS

2. 1, the concept of CMTS

CMTS (cable modem? Terminal system), CMTS is the equipment for managing and controlling Cable Modem, and its configuration can be completed through Consol interface or Ethernet interface. Its configuration contents mainly include: downlink frequency, downlink modulation mode, downlink level, etc. Downlink frequency can be set arbitrarily within the specified frequency range, but in order not to interfere with the signals of other channels, we should refer to the channel division table of cable TV and choose at the specified frequency point. The selection of modulation mode should consider the transmission quality of the channel. In addition, you must set the IP addresses of DHCP, TFTP server and CMTS. After the above settings are completed, if there is no fault in the intermediate line and the signal level attenuation meets the requirements, start the DHCP and TFTP servers, and a normal communication channel can be established between the front end and the Cable Modem.

At present, although the access technology of CMTS is relatively mature, with the emergence of EPON+EOC technical scheme, radio and television departments and equipment vendors are gradually inclined to the technical route of "EPON+EOC". The main reasons are as follows: ① the average cost of ①EOC is lower than that of Cable Modem, which benefits from the rapid price reduction of optical communication equipment; ② obvious technical advantages, less interference, long service life and low operation and maintenance cost; ③ Better bandwidth experience; ④ High safety.

2.2. Advantages and disadvantages of CMTS

At present, there are two mainstream schemes for two-way network transformation. In addition to a new scheme proposed in recent two years (EPON to Building++EoC technical scheme), the other is a two-way transformation scheme based on HFC network (CM scheme).

The biggest advantage of two-way transformation scheme based on HFC network (CMTS+CM scheme);

First of all, it is highly centralized, and there are no other active data network devices except front-end (front-end) CMTS and user-side CM, which is convenient for management and maintenance. Another advantage of CMTS is its low time cost: once deployed, users can open at any time like telecom ADSL, which is very important for competition.

Secondly, the coverage is large. Considering broadband access services only, CMTS can invest in stages and expand gradually.

In addition, the standardization and maturity of CM are unmatched by other schemes. DOCSIS standard has the highest bandwidth utilization and the highest throughput. By using channel bundling technology, DOCSIS3.0 can greatly improve the rate, even reaching the level of downlink 1Gbps and uplink 500Mbps, which is beyond the reach of all other copper cable access technologies at present.

In the era when coaxial cable accounts for a large proportion of HFC network, CMTS is almost the only alternative two-way transformation scheme based on coaxial cable.

The biggest defect of the two-way transformation scheme based on HFC network (CMTS+CM scheme);

First of all, the high cost per unit bandwidth of CMTS is the fatal weakness of this scheme. In a short period of time, if only broadband access and Internet access are used, the actual access service of each channel is less than 200 households (covering less than 2,000 households). Due to * * * access and non-simultaneous application, the Internet access rate can reach 200 k-2 m. If you use streaming media services (IPTV, VOD and other popular new services), each user needs to occupy the network and throughput data for a long time, and each channel can only serve less than 40 households, which is too expensive. Unless CMTS can reduce the price by more than 90%, this may be a cost-effective solution.

Secondly, the convergence of reverse noise is also a difficult problem in engineering and maintenance. The reverse design and construction technology control of HFC network is still difficult to implement in most areas of China (especially in small and medium-sized cities), and the technical support needed for maintenance and operation troubleshooting is also difficult to be properly solved in most areas of China in a short time.

2.3. The transformation of two-way network is still mainly based on CMTS, and the application of EPON+EOC is gradually expanding.

By the end of June, 20 10, according to the Quarterly Monitoring Report of Digital TV Operation in China, there were more than 46 million users covered by wired two-way networks in China. The transformation of two-line network will be one of the important tasks of China's digital development in the next stage.

Glenn research tells DVBCN that in the current two-way transformation of radio and television networks, less than 20% of cable operators have completed the two-way network transformation of all network users, and 35.3% of cable operators have basically completed the transformation of urban networks, such as Nanjing, Suzhou and Harbin in Jiangsu Province. There are 27. 1% cable operators in Hunan, Hubei, Anhui, Jilin, Shenyang, etc. who are promoting the network transformation in their own regions, actively promoting the transformation of two-line networks, promoting the development of two-way interactive services, and improving their competitive advantage in the triple play. The task of cable operators' two-way network transformation is still arduous.

At the same time, the information provided by Glen Research to DVBCN reporters shows that CMTS and EPON+EOC are the main network transformation technologies of cable operators at present. With the gradual improvement of EPON+EOC technology, the equipment cost is gradually decreasing. At present, more and more cable operators choose EPON+EOC technical scheme, which can effectively reduce the capital investment of two-way network transformation and alleviate some financial pressure.

Judging from the current situation, Wuhan Changguang, Alcatel-Lucent and Glen Research all told DVBCN reporters that "EPON+EOC" will be the main technical solution for the two-way network transformation of cable operators in the future.

3. Lan

3. 1, the concept of local area network

A local area network (LAN) is a local geographical area (such as schools, factories and offices) connecting various computers. A computer communication network composed of external devices and databases. It can be connected with remote LAN, database or processing center through data communication network or special data circuit to form a large-scale information processing system. The abbreviation of local area network refers to a group of computers interconnected in a certain area. "A certain area" refers to the same office, the same building, the same company, the same school, etc. , generally within a few kilometers of Fiona Fang. LAN can realize file management, application software sharing, printer sharing, scanner sharing, workgroup scheduling, e-mail and fax communication services. LAN is a closed type, which can be composed of two computers in an office or thousands of computers in a company.

Local area network (LAN) is an information network that provides interconnection for various data communication devices in a small area. Among them, the main technologies that determine the characteristics of LAN are: first, the transmission medium used to transmit data; The second is the topological structure used to connect various devices; The third is the media access control mode of * * * enjoying resources.

LAN technology mainly includes Ethernet series technology and token network technology. Ethernet technology has the characteristics of low cost, simple technology and convenient use and management. Ethernet series technologies mainly include Ethernet, fast Ethernet, Gigabit Ethernet and 10G Ethernet.

In this technology, five lines are used to access the two-way network to transform the family and complete the access function of two-way data services, and the cable TV network is still realized by HFC network.

The five-line access mode has the characteristics of high access bandwidth, scalability and multi-service operation. In the later maintenance, five types of wiring modes meet the requirements of integrated wiring system. The interaction between users is small, and maintenance and fault handling are convenient.

There is a problem that the five-category line needs to be rebuilt in the access mode of the five-category line, and the construction quantity and difficulty are great. Therefore, the five-category line access mode is mainly suitable for areas with dense network users such as newly built residential embedded lines or office buildings.

3.2. Advantages and disadvantages of LAN

Because LAN is a local area network, other advantages are that after the two-way transformation is completed, the unit users who choose EPON to building++EoC technical scheme monopolize the line resources, so there is no problem of mutual interference, and there is no need for new users' terminal investment to carry out on-demand services, which can effectively save the opening cost. In terms of storage bandwidth planning, EPON+LAN technical scheme is 1000M to the community, 100M to the corridor, and 100 m to the home, which can meet the needs of users for high bandwidth and multi-service access in the future.

However, LAN also has a big disadvantage: it can't be laid outside the building, and it is vulnerable to lightning. If the registration rate is too low, the investment of the whole store is too large, the utilization rate is too low, and the investment payback period is longer.

In addition, the DVBCN reporter believes that the construction of local area network is difficult only in new residential areas, which does not conform to the concept that upgrading needs to protect existing investment as much as possible. In fact, LAN is an indoor product, which is simple to set up, but it has the characteristics of high requirements in all aspects and high maintenance cost.

3.3 Application of EPON+LAN technical scheme

As for the technical scheme of EPON+LAN, Dr. Yu Shaobo thinks that EPON+LAN is actually two networks, which is suitable for Great Wall Broadband without its own network. It is actually a misunderstanding not to understand EPON+LAN as cheaper. Because in the case of full service and fine management, QINQ is needed. If QINQ mode is adopted, the corridor switch is required to have QINQ function, not a simple HUB, but a real switch, and the price is about 100 yuan/port. For example, to cover 64 users, it costs about 6400 yuan, which is about four times more expensive than the general EOC office. In addition to other installation costs, the cost is actually more expensive than EPON+EOC.

In an interview with DVBCN, Dr. Hu of Wuhan Changguang thinks that although the cost of EPON+LAN may be cheaper than EPON+EOC according to the existing calculation, comprehensive cost comparison is needed. The general calculation method of EPON+LAN does not calculate the home gateway or switch of the user's home, and with the unification of EOC standards, the market of EPON+EoC may be more competitive in the future.

However, in the application of business circle, Dr. Hu thinks it is also feasible to adopt EPON+LAN model in business buildings, hotels and other market segments.

summary

Under the convergence of the three networks, the primary task facing radio and television is to speed up the digital upgrading of radio and television networks. In choosing the technology of two-way transformation, what radio and television network access operators need to do is to find a suitable road among many two-way network transformation schemes; Summarize three mainstream access technologies in two-way transformation of radio and television in one sentence: EOC needs standardization, CMTS needs cheaper, and LAN needs access rate.