TELECOMMUNICATIONS
The local loop is truly a loop; it is a loop of copper wire that allows current to flow from the tele-phone to the central office and back. It is the dual-wire physical interface that connects a telephone to the central office. The central office, also referred to as the local exchange, serves a group of subscribers (customers) in a local area. Local exchange carriers (LEC) are local telephone companies that provide service along with other LECs within a designated geographical area. The designated geographical area is typically referred to as the local access and transport area (LATA).
In the telephone system, the point where either an LEC or a long-distance carrier meets another long-distance carrier is defined as the point of presence (POP). The POP provides the interconnection to the long-distance carrier or interexchange carrier (IXC).Making a phone call today from a cellular or fixed land-line phone can happen instantaneously. The caller is unaware of how their call is routed to the recipient. The phone system works so well that it is often taken for granted and few customers rarely take the time to learn how the telephone system is organized.
Cellular telephones are wireless telephones that are served by a cellular telephone system. This system is broken into many small geographical areas called cells. Cells are connected to a Mobile
Telephone Switching Office (MTSO). The connection from the cell to the MTSO is typically done over telephone lines. These lines could be copper or fiber optic, and in some applications, micro- waves are used.
A cellular telephone is essentially a two-way radio that carries a full-duplex conversation. Full-
Duplex means that the persons using the telephones can talk and listen at the same time. This is different from a walkie-talkie, where only one person can talk at a time, which is referred to as
Half-duplex.
Typically, the geographical area of a cell is kept small to minimize the amount of radio frequency
(RF) power required for the cell phone to communicate with a cell tower.
The first generation (1G) cell phones transmitted information in an analog format very similar to the way a fixed-line telephone transmits voice information from the subscriber to the central office. However, when the second generation (2G) cell phones entered the market, transmission shifted from analog to digital. Not only do 2G telephones have the ability to transmit and receive voice, but they also have the ability to transmit and receive data.
Data
As 2G technologies matured, it became clear that the cell phone could be used for many appli- cations other than just carrying on a conversation. Many people were using their cell phones to access the Internet. To meet consumer need for data, a third generation (3G) of cell phone technology was introduced. 3G technologies offered higher data rates over 2G, paving the way for multimedia applications. While many cell phones in operation today are 3G, they will eventually all be replaced with fourth generation (4G) technology. 4G networks offer 10 or more times the data transmission rate of a 3G network. The data rates available on a 4G network allow the cell phone to access infor- mation from the Internet as fast as a land-line connection
The demarcation point is the point at which the responsibility of the service provider ends. If there is a problem with inside wiring or equipment beyond the demarcation point, it is the responsibility of the end user or building owner. Inside wiring is the cabling that spans the demarcation point to the phone system, phone set, or computer used by a consumer. The demarcation point is made in the entrance facility portion of the main equipment room in commercial buildings or the ONT (optical network terminal) of FTTH networks or basic telephone termination points inside a home. This cable connection is known as the “drop cable.” The demarcation point may also be at the MPOE (minimum point of entry), which is the first enclosed room inside the building where the telecom providers terminate their cabling, or it can be an extended demarcation point; within the building itself.
The demarcation point includes the tie-in of OSP (outside plant) cable to the customer premise equipment racks and active equipment. In FTTH networks, this connection is made in the customer premises where fiber-optic or copper cabling is connected to the ONT. From the ONT in an FTTH network, the signal is converted to an electrical signal and transmitted over the coaxial cable infrastructure of the home to set-top boxes and modems.
The access network is the part of the network that connects the individual consumer or business to the telecommunications system. Ultimately, it is the gateway to telephone communications, Internet/data, and video- the services offered by telecommunication service providers. It consists of a series of fiber-optic and copper cabling and passive and active equipment that connects homes, schools, hospitals, public and private businesses, and so forth to the local exchange. The