 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Access network" – news ·newspapers ·books ·scholar ·JSTOR(February 2008) (Learn how and when to remove this message) |
Anaccess network is a type oftelecommunicationsnetwork which connects subscribers to their immediateservice provider. It is contrasted with thecore network, which connects local providers to one another. The access network may be further divided between feeder plant or distribution network, and drop plant or edge network.
An access network, also referred to as anoutside plant, refers to the series of wires, cables and equipment lying between a consumer/business telephone termination point (the point at which a telephone connection reaches the customer) and the localtelephone exchange. The local exchange contains banks of automated switching equipment which direct a call or connection to the consumer. The access network is perhaps one of the oldest assets a telecoms operator would own.
In 2007–2008 many telecommunication operators experienced increasing problems maintaining the quality of the records which describe the network.[citation needed] In 2006, according to an independentYankee Group report, globally operators experience profit leakage in excess of $17 billion each year.[citation needed]
The access network is also perhaps the most valuable asset an operator owns since this is what physically allows them to offer a service.
Access networks consist largely of pairs ofcopper wires, each traveling in a direct path between the exchange and the customer. In some instances, these wires may even consist ofaluminum, which was commonly used in the 1960s and 1970s following a massive increase in the cost of copper. The price increase was temporary, but the effects of this decision are still felt today aselectromigration within the aluminum wires can cause an increase in on-state resistance. This resistance causes degradation which can eventually lead to the complete failure of the wire to transport data.
Access is essential to the future profitability of operators who are experiencing massive reductions in revenue fromplain old telephone services, due in part to the opening of historically nationalized companies to competition, and in part to increased use ofmobile phones andvoice over IP (VoIP) services. Operators offered additional services such asxDSL based broadband and IPTV (Internet Protocol television) to guarantee profit. The access network is again the main barrier to achieving these profits since operators worldwide have accurate records of only 40% to 60% of the network. Without understanding or even knowing the characteristics of these enormous copper spider webs, it is very difficult, and expensive to 'provision' (connect) new customers and assure the data rates required to receive next-generation services.[citation needed]
Access networks around the world evolved to include more and more optical fiber technology. Optical fiber already makes up the majority of core networks and will start to creep closer and closer to the customer, until a full transition is achieved, delivering value-added services overfiber to the home (FTTH).
The process of communicating with a network begins with anaccess attempt, in which one or more users interact with a communications system to enable initiation of user information transfer. An access attempt itself begins with issuance of anaccess request by anaccess originator.
An access attempt ends either in successful access or inaccess failure - an unsuccessful access that results in termination of the attempt in any manner other than initiation ofuserinformation transfer between the intended source and destination (sink) within the specified maximum access time.
Access time is the time delay orlatency between a requestedaccess attempt and successful access being completed. In atelecommunications system, access time values are measured only on access attempts that result in successful access.
Access failure can be the result of access outage, userblocking, incorrect access, oraccess denial. Access denial (system blocking) can include:
Anaccess charge is a charge made by alocal exchange carrier for use of its local exchange facilities for a purpose such as the origination or termination of network traffic that is carried to or from a distant exchange by aninterexchange carrier.
Although some access charges are billed directly to interexchange carriers, a significant percentage of all access charges are paid by the local end users.
Apassive optical distribution network (PON) usessingle-mode optical fiber in theoutside plant,optical splitters andoptical distribution frames, duplexed so that both upstream and downstream signals share the same fiber on separate wavelengths. Faster PON standards generally support a higher split ratio of users per PON, but may also use reach extenders/amplifiers where extra coverage is needed.Optical splitters creating apoint to multipoint topology are also the same technology regardless of the type of PON system, making any PON network upgradable by changing the optical network terminals (ONT) and optical line terminal (OLT) terminals at each end, with minimal change to the physical network.[1]
Access networks usually also must supportpoint-to-point technologies such asEthernet, which bypasses anyoutside plant splitter to achieve a dedicated link to thetelephone exchange. Some PON networks use a "home run" topology where roadside cabinets only containpatch panels so that all splitters are located centrally. While a 20% higher capital cost could be expected, home run networks may encourage a more competitive wholesale market since providers' equipment can achieve higher use.[2]
