Abstract: With the revenue share of broadband expansion, network operators the choice of broadband access technologies become more and more critical.Proposed principle of selection of broadband access technologies, discusses how the network operator with its own characteristics and the characteristics of target customers to choose their own means of broadband access technologies.
Keywords: ADSL VDSL Ethernet Cable Modem
"Who will come to have a broadband world," is a broadband network operator catch-phrase.Traditional 56 kbit / s dial-up mode can not meet the requirements of multimedia, which gives broadband network operators proposed a "last mile" access problem.Now common broadband access solutions with 3: Cable Modem, xDSL, and Ethernet.
Choose a suitable way of access to its own characteristics, is a broadband network operator's network in the era of fierce competition to win one of the keys.
Comparison of Access Technology
With the rapid development of Internet, network information has become more abundant, thus promoting the rapid development of broadband services, broadband services have become the major operators of new business growth, broadband users are increasingly becoming an important resource for the telecommunications industry, and accessway related to every broadband user, it is particularly important.While most operators have to support multiple access modes, but all operators have their own development process and characteristics, so often dominated in some way the direction of access.If the poor choice of access mode, it will directly affect the development of broadband services.
1.Cable Modem
Cable Modem access method is the use of coaxial cable to transmit data, it's up and down the line rate of up to 48 Mbit / s, but in normal circumstances, our operators only provide 10 Mbit / s downstream and upstream rate.Its main advantage is coverage, the line of low cost, almost every household has cable TV, providing the business does not require re-laying lines, faster service provisioning time, and low cost.But the Cable Modem is a bus-type access, mutual interference between users of the more prominent problems, line failures to the user larger sphere of influence.Users on the same cable to each other to share bandwidth in dense residential areas, due to too many users are generally difficult to achieve a more satisfactory rate.Cable Modem Sharing and because the topology of all the information on the same cable to any one user are visible, no way for the isolation between users, security is an issue can not be ignored, and now basically only by the contentlayer of encryption to protect data security.There are poor anti-interference ability Cable Modem, severe packet loss, route stability is poor, these are also one of the reasons affecting their promotion.
While Cable Modem security and stability exist some shortcomings, but if used in appropriate circumstances, is also a very good access.Cable Modem has been widely used in the United States, and its transfer rate because it has the advantage, but more suitable for the characteristics of U.S. residential layout.Distant intervals between the U.S. home, the user is more sparse, Cable Modem user density is low in this environment, the transmission rate is higher than both xDSL and Ethernet access mode, the pursuit of high-speed, clear, smooth videoAmericans enjoy, Cable Modem for granted as the user's choice.And most of the U.S. broadband users are using video traffic, occasional packet loss has little effect on the quality of service, security, more is not an issue.U.S. network operators in addition to providing access mode other than the Cable Modem, ADSL and other access methods are also available, but its share is much smaller than the Cable Modem.
2.xDSL
xDSL technology is the United States, Bell Communications Research Institute in 1989 as video on demand (VOD) business development in the use of twisted-pair high-speed data transmission technology.xDSL is the most representative of the two kinds of asymmetric DSL technology:
· ADSL, in a twisted pair to provide a downlink rate of 1.5 ~ 8 Mbit / s, upstream rate of 16 ~ 640kbit / s.
· VDSL, twisted pair to provide a downlink rate of 3 ~ 52 Mbit / s, upstream rate of 1.5 ~ 2.3Mbit / s.
ADSL / VDSL use of ordinary telephone lines as the transmission medium, it has wide coverage, low cost line, as long as phones can be quickly opened the place to ADSL / VDSL service.ADSL / VDSL access mode using star topology, between the user and the user is physically isolated from each other, with high security, simplifies endpoint security encryption of customer requirements, reducing the threshold of user skill levels,thereby expanding the scope of the user.Each ADSL / VDSL users are exclusive of a transmission line, the bandwidth management is very easy to do on a flexible, you can easily assign each user different bandwidth, thereby increasing the flexibility of tariffs, user to choose their network bandwidthservices.The quality of the line, ADSL / VDSL are using advanced modulation techniques such as Discrete Multi-Tone (DMT), etc., these technologies can provide a good line detection and self-maintenance functions, automatically according to line quality, environmental interference, transmissionand even send and receive power from a variety of transmission parameters to adjust to meet the predetermined quality of service requirements, the ADSL / VDSL network has a strong self-maintenance and management functions.But ADSL / VDSL because the use of star topology, the relative use of bus-based Cable Modem, the line investment is large.ADSL / VDSL is asymmetric DSL technology is far greater than the rate of uplink downlink rate, generally only the access way as a normal user, not for the basic symmetric flow of Internet business users, the use of video telephony and video conferencing, etc.Users are not suitable.
In Asia, especially in densely populated China, Korea and other countries, ADSL / VDSL has become the dominant access mode, and an absolute advantage.In contrast, Cable Modem and Ethernet access to the share of pathetic.One reason is that most network operators are developed from the traditional telecom operators, they have rich resources and a large number of fixed end-user loyalty, the use of ADSL / VDSL access means, the traditional telecom operators to quicklyto the business expanded from traditional phone service to broadband Internet services to its large fixed-line to inject new vitality.On the other hand, Asia's users browse the Web, download movies and online games as the main demand, the characteristics of these applications are far greater than the upstream flow downstream traffic, using ADSL / VDSL access means just to maximize the full use oftransmission line resources.
3. Ethernet
Ethernet is a layer of the media access control technology, the common transmission medium is a five twisted pair, it is the most widely used LAN technology, more than 85% of the network using Ethernet technology.Since Ethernet has a simple, low cost, extensible, high speed interface, features, and its applications are from the internal network to the public telecom network into the field.Although the Ethernet in the LAN has made great success, even a computer terminal Ethernet interfaces are standard, but as a commercial network access, it has obvious limitations.It is too much investment in the line, the transmission distance is too short, a large number of access devices require users cloth on the left a distance of less than 100 M, low resource utilization equipment Ethernet access mode is a major difficulty.Ethernet transmission medium used is different from the traditional five categories of twisted pair telephone lines, broadband services need to re-opening of laying lines, this aspect of the business opening hours, on the other hand the exclusion of vulnerable households.Ethernet access method in the operation and maintenance are also many problems, such as manageability and control for business recognition is not strong, it is difficult to achieve flexible bandwidth control, security, lack of consideration, these characteristics have hindered the Ethernetpromote the use of access methods.
The Ethernet access method as the leading network operators much, usually there is no fixed telephone network that are both, and no new cable network, network operators, they tend to large customers, the group targeted users and residential areasusers.These users have one thing in common, that is, a high concentration of users, they can be understood as a large local area network, so that Ethernet can give full play to their technical superiority.
Although the use of small Ethernet access, Ethernet technology itself but the application of broadband access can be said to be everywhere.It depends on the terminal device.General terminal interface transfer rate low, only Ethernet interfaces can provide 10, 100 Mbit / s transfer rate, regardless of network operators use ADSL / VDSL, or Cable Modem, Ethernet interface will eventually be converted into the terminaldevice interconnection.Therefore, the final choice of access mode, or depending on the terminal device.
Wireless Ethernet (WLAN) access mode is a kind of Ethernet access.WLAN is becoming the global number of users rapidly growing trend, WLAN is likely in the near future become a means of access can not be ignored.Although China Telecom in 2003 to promote the WLAN business is not obvious, but if the office and wireless Internet access within the family to promote the WLAN business, rather than hot spots to drive, WLAN business development in China will have a new world.
The principle of access technology selection
Each technology has its advantages and disadvantages, have their application environment.For network operators, in the choice of means of broadband access technologies can not on the technology, but should be market-and efficiency as the center.Only to meet the needs of users, adapt to market needs, cost-effective technical vitality.Therefore, operators in the development of broadband services should be combined with its own characteristics, give full play to existing strengths, to increase costs, but much lower quality of service and premise, trying to find technology, marketing and efficiency as well as functionality, performance and cost balancepoint.
Cable Modem access mode for the traditional cable company, low cost, functionality and performance are not entirely satisfied, but if for some IP TV, video telephony, video conferencing and online viewing of a number of multimedia services is also a very goodchoice.Of course, with Cable Modem access methods need to be considered a problem is that users can not be too concentrated, or the bandwidth of each user no way guaranteed.
xDSL access mode on the traditional phone company, low cost, broadband users in China, but also more compatible with their habits, although the rate of asymmetric uplink and downlink, but it can make maximum use of transmission line resources.Even for video calls and video conferencing traffic symmetrical multimedia services, the uplink rate of 640kbit / s can also provide satisfactory results, and this traffic accounts for a symmetrical network of video services is not a large proportion of the total flow, that is,Regular users of the use of such video services are not many, so China's broadband users, xDSL is a very appropriate access.Building can be operational, management, broadband access networks must address a range of technical issues, including user management, user and network security, quality of service control, network management.Cable Modem to meet all these requirements appeared to be inadequate, and only use xDSL access mode of star topology, To solve the above problem provided the necessary foundation.
The use of Ethernet access method is costly, and it originated in the internal network, all network users are trusted, and did not consider security issues.Use it to build a distrust of the public network, also need to address user management, user and network security, service quality control and other issues, which in turn increased the cost of network construction.Ethernet network for a number of new operators, they do not have cable TV networks and telephone networks, business must be re-laying lines.Such operators are often the target user group of commercial buildings and residential quarters, the user is very concentrated, so that can fully reflect the benefits of the Ethernet in the LAN.Therefore, the Ethernet access method for large customers, the Group remains the user is a good choice.WLAN as well as the increase in mobile users and mobile habits become formed, but also a means of access can not be ignored.
China's national conditions, the broadband data communications services are still mainly on the line quality and network security requirements are higher, and the bandwidth requirements are not harsh, together with China's large population density, Cable Modem speedadvantage is more difficult to play, so the use of Cable Modem to develop broadband services is not a good option.ChinaNet carriers from China's experience, the broadband users during the break of the game, hanging dead and so is very sensitive to frequent complaints, and these phenomena because the transmission quality is often poor and are therefore used to develop broadband services Cable Modemin China is not a wise move.