Remote subscriber unit
The remote subscriber unit RSU is increasingly being used to connect the distribution cable to the Central Office. It provides the subscriber line interface card SLIC for conventional plain old telephone service POTS . This is discussed in Section 4.5. The RSU can also carry out a concentrator function with an optional local switching capacity. The RSU may also provide independent interfaces for high-speed data circuits. The RSU is particularly useful for remote customers who would require the...
Broadcast vs pointtopoint topologies
Networks consist of several nodes workstations, printers, PLCs, etc. interconnected via some sort of medium. The way the nodes are interconnected is known as the topology. There are many possible topologies but they all form in one of two categories, broadcast and point-to-point. Broadcast topologies are those where the messages ripple out from the transmitter to reach all nodes. There is no active regeneration of the signal by the nodes and thus signal propagation is independent of the...
RTCP packet format
This specification defines several RTCP packet types to carry a variety of control information, namely SR A sender report, for transmission and reception statistics from participants that are active senders RR A receiver report, for reception statistics from participants that are not active senders SDES Source description items, including CNAME BYE Indicates end of participation APP Application specific functions. Each RTCP packet begins with a fixed part similar to that of RTP data packets,...
Twistedpair cable parameters Loop resistance
The resistance of a copper cable pair depends on the diameter of the conductors. Loop resistance is the total resistance in the conductors between the Central Office switch and the subscriber, that is twice the resistance of one individual conductor of that length. Cable diameters are normally measured either on millimeters or American wire gage AWG . A comparison of these different conductor sizes and their corresponding loop resistances is shown in Table 3.1. Typical twisted-pair cable...
Common channel signaling
With modern stored program controlled exchanges it is inefficient for the digital processor to handle channel associated signaling. A much more efficient method is to transfer all the signaling information between the processors over a high-speed data link. This is called common channel signaling CCS . This has many advantages including having a signaling path which is entirely separate from the switched speech paths, very fast signaling is possible because of the wide bandwidth 64 kbps of the...
Switched 56
Switched 56 or global switched digital services is a digitally switched or dial-up service, used primarily in North America, that has the capacity to provide a single data channel of 56 kbps on demand. Different telecommunications companies call the service by different names some of these are listed in Table 6.6. Switched 56 access lines were some of the first digital circuits installed by the telecommunication carriers. The low cost of switched 56 service relative to digital leased lines...
Star hub topology
In a physical star topology multiple nodes are connected to a central component, generally known as a hub. The hub usually is just a wiring center, that is, a common termination point for the nodes. In some cases, the hub may actually be a file server a central computer that contains a centralized file and control system , with all the nodes attached directly to the server. As a wiring center, a hub may in turn be connected to a file server or to another hub. All packets going to and from each...
European TDM multiplex hierarchy
Higher level TDM multiplexing is used to combine E1 systems by interleaving bits from the various E1 inputs. For example, the E2 transmission system combines four E1 inputs into an 8.448 Mbps data stream byte interleaving. Additional bits are required for framing and control purposes. Table 6.5 illustrates the various ITU-T circuit designations and their corresponding bit rates.
Objectives Bia
When you have completed study of this chapter you should be able to List the main technologies available for broadband customer access Explain how ADSL systems operate Discuss the applications of the various xDSL systems Describe the operation of VDSL systems Compare the operation of ADSL and G.lite systems Describe the application of Ethernet to customer access systems Discuss high-speed data access for HFC and FTTC systems Discuss the limiting factors in LMDS system design Explain suitable...
First party call control
In the first party configuration a call is controlled by the call parties. First party or phone oriented call control involves a direct interface between the user's PC and the telephone switch by intercepting line signaling between the telephone and the switch as shown in Figure 5.2. Because of this approach, it limits itself to conventional signaling conditions used in PSTN telephones. The telephone-to-computer interface is usually a phone line connection. This connection can be via RJ-11...
Local vs remote bridges
Local bridges are devices that have two network ports and hence interconnect two adjacent networks at one point. Nowadays this function is usually performed by switches as they are basically multiport bridges, and are available with as few as two ports Figure 8.11 . A useful type of local bridge is a 10 100 Mbps Ethernet bridge, which allows interconnection of 10BaseT, 100BaseTX and 100BaseFX networks, thereby performing the required speed translation. These bridges typically provide...
IEEE 8025 Token ring
As in 802.4, data transmission can only occur when a station holds a token. The logical structure of the network wiring is in the form of a ring, and each message must cycle through each station connected to the ring. This standard is the ratified version of the IBM token ring LAN. However, where IBM token ring supports speed of 4 and 16 Mbps, IEEE 802.5 supports 1 and 4 Mbps. The physical media for the token ring can be either unshielded twisted pair, coaxial cable or optical fiber. The...
Radio path profile
The next step involves identification of the appropriate transmitting and receiving sites. Terminal sites need to be located close to the equipment they will serve, whereas intermediate repeaters are not constrained. The main site selection criteria will be Proximity of road access and above all Feasibility of the radio path. Preliminary site selection is often done from examination of topographical maps of the area, having a scale of at least 1 50 000. The next step is to draw a straight line...
The application programing interface
The second component of the CTI architecture is the application programing interface API . This is an interface that enables software developers to create new applications. Three standards will be discussed namely TAPI, TSAPI and JTAPI. Microsoft's telephony application programing interface TAPI enables Windows programmers to develop telephony applications in software. The current version is TAPI 3.0. The TAPI 3.0 component object model allows programmers to write TAPI applications in, for...
Local switches 451 Local switch overview
A local exchange or Central Office switch has inlets to serve incoming calls and outlets to serve outgoing calls. A call from the calling subscriber enters the switch via an inlet and is then connected to the calling subscriber on the outlet side of the switch. The switching function can be space-switched or time-switched or use combinations of the two. The switching function is initiated by the calling subscriber using line signaling conditions of either 'off-hook' or 'on-hook' together with...