Research On Access Modes Of The Broadband In Local Telecommunication Network

With the constant progress and syncretism of the communicationand computer technology,as offering the basic service to the socialinformated,telecommunication networks are developping towardsproviding much more service,much higher system performance and muchpowerful processing ability .The access network , the bridge ofconnecting customer terminals access to the core net of thetelecommunication network,is the key to making the whole networkdigitalized broadbanded and synthesized.With the rapid pace of thebroadband intelligent housing estate in our country, the issue ofbroadband access leads to more and more attention. The question thatSPs(Service Provider) actually use which kind of technology to providebroadband access service to the customer,not only directly influencesthe service quality ,but also has a direct bearing on the investmentcost and long-term development of the telecommunication operatingenterprises.1,Broadband access technology summary and comparisonAccess network belongs to broadband or narrowband is usuallydivided according with rate of user network interface. Generally, themaximum access rate which exceeds 2Mbit/s is called broadband access.At present, the broadband access technology of ShenYang fixed networkmainly includes ADSL,HFC,Ethernet.ADSL(Asymmetric Digital Subscriber Line) is a kind of asymmetriccopper lines access network technology.It adopt frequency-divisionmultiplex to make transmission in a twisted-pair telephone line forup and down line data and phonetic service.Maximum down linetransmission rate can up to 8Mb/s , up line transmission rate can upto 640Kb/s.At present, the wildly used ADSL modulate technology is DMT(Discrete Multi-tone Modulation). The modulation of DMT belongs tomulti-wave modulate technology. It takes the breadth 1.1MHz to bedivided into 256 independent and equal bandwidth sub-channels.According to the performance( such as signal noise ratio, attenuationetc.) of the channel that is the capability of the transmission data ,the input data can be distributed self-adapting into each sub-channel.If some sub-channel can not load data , it will be closed samply. butto those sub-channel which can transmit data ,it will transmit 1-15bits information in each element envelope against its instantaneouscharacteristic. ADSL access's disadvantage is that the actualapplicable speed is influenced easily by the length of telephone lineand line quality which lie between the users and telephone office.AndADSL is used by un-shielded cable in the room and outside which hasless resistance to weather interference .Therefore ADSL is only atransitional technology and can not meet the progressive raterequirements of the broadband access .HFC is Hybrid Fiber Coax cable net which is a new broadband accesstechnology on the basis of the CATV .This net connects fiber back bonecable and coaxial distribution cable by fiber node . Each fiber nodewill serve 200-500 customers by coaxial distribution cable. All theusers which has been connected together will share same cable and sharethe usable capacity and bandwidth in the same time. HFC will realizeinternet access by Cable Modem. The up and down rate is related to themanufacturer. Generally , the maximum of up and down transmission ratecan up to 10M and 40M . The key technology of HFC is reverse channelnoise restrain technology . Because HFC is developed on the basis ofCATV, it not only can provide data transmission business , but alsocan supply traditional boardcasting , TV and FM , etc. which can notbe provided by other access technology. HFC support all available andnew transmission technology, including ATM,frame relay, SONET and SMDS.If HFC is distributed into place, it can expand by SPs convenientlyto meet the day-increase requirements and support new service. But HFCis a share-type net. That means the user will enjoy the net with itsneighbors. So the theory transmission rate of HFC will reduce with theincreasing of users.Ethernet is a technology of computer local area network(LAN) . Asa realization of broadband access network,it is fit to the access ofhigh-speed data services, especially the services on the basis of theIP data supporting. Exchange-type ethernet settle the low efficiencywhich caused by sample shared-transmission mediem of shared ethernet.Fiber improve the limitation of transmission distance greatly. Withthe appearance of Fast Ethernet and Gigabit Ethernet, the transmissionrate has been improved to 100Mbps/1Gbps. The key technology of Ethernetincludes authentication, charge, user administration, user and networksecurity , quality control and etc. Ethernet is all the time the mostfashionable way for enterprise and broadband intelligent block.2, ConclusionThis article takes the engineering project of Shenyangtelecommunications broadband access as the example and analyses thedifferent net situation and source feature of different SPs to providethe referenced evidence for the choice of the settlement of broadbandaccess project. The writer can divide local broadband users into threetypes: enterprise user, un-concentrated residence user, concentratedresidence user according to their spread characteristics. Theirsettlement is as follows:First:enterprise userThe enterprise user is usually an independent business entity whohas the higher requirements for reliable and stable of broadband access,usually they require for access to broadband network of SPs withseparatly route. Ethernet is sutable to the access of high rate dataservices as a computer LAN technology for broadband acces, especiallysupporting the data on the basis of IP. The frame format of Ethernetis the same as IP data packet. There are no any format questions whendata transmits in Ethernet. So it can get united with IP net seamlesslyand it has good expansibility. In additional. Ethernet technologypossesses strong network basis and rich experience. At present, allthe fashion operation system and application can be compatible withEthernet.Based on above reasons, no matter which kind of SPs, Ethernet isthe first choice for broadband access.Second:un-concentrated residence userBecause of the low density of un-concentrated residence user, lowutilization, large line investment and low ARPU value, therefore, howto take advantage of resources and improve economy is the priority toun-concentrated residence user.1). to the operator who own large langurage business user ( suchas Shenyang Net Communication):This SP has been in local place for many years. The Foundationresource (special pipe resource) is sufficient and copper cable israther rich which have been covering all the roads and streets ofShenyang. Furthermore, the quantity of local office is large. Thedistance from the local office to the ends is less than 3 kilometer.SP should provide broadband access with installation of ADSL equipmentat local offices and making use of original copper cable to users.2). To new SP (such as Shenyang Telecom, Shenyang RailwayCommunication) :This kind of SP is lack of resource foundation (especially piperesource). Therefore, they always take fiber into the district (inorder to save pipe resource) . Meanwhile, as the local office is fewand all the distance is more than 3 kilometer, under this situation,they should adopt ADSL with access network equipment inside and circuitboard for a few users.3). to the cable TV operator:In the area of Shenyang ,the cable TV operator have been coveringall the district and further connect the users by coaxialcable ,therefore, to reconstruct original cable TV network and makeit fit to providing broadband access is worth considering.Third :concentrated residence userBecause of the high density for concentrated residence user spread ,high utilization of equipment , concentrated wires investment, thethoughts of broadband access for concentratedand is great differentfrom those for un-concentrated.1). To the SPs who own large users for phonetic service ( such asShenyang Net Communication):SP should adopt different ways to different situations. To ordinaryresidential user, we should utilize ADSL with original copper cables.Tohigh class residential user, we should utilize Ethernet consideringthe add-value space and developing trend of "fible to the table".2). To new SPs (such as Shenyang Telecom, Shenyang RailwayCommunication):As all the fiber has been into the district, we should use Ethernetway for future developing.3). To cable TV operator:To concentrated residence users, the different of reconstructingoriginal cable TV network and utilizing spare cable resource is notbig from re-using Ethernet access technology. SP should pay attentionto the project difficulty of new spread wire of the engineering.At present, the developing of broadband access technology ischanged with each passing day and also different in actual project.When meeting the concrete questions, we should adopt more than twosuitable modes to provide differential service . Only by that, we cantake advantage of network resources and provide satisfactory serviceto customer by maximization.