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Covert Commissions

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Groups of Subscriber Signals

Supervision Signals (or line signals) are signals sent by subscribers to local exchanges. The forward supervision signals (request-for-service, disconnect by calling party) request the start or end of a connection. The backward supervision signals (answer, disconnect by called party) change the state of a call. Address Signals (also known as digits and selection signals) are forward signals that are sent by the calling subscriber when dialing the called party number. Ringing. A forward signal sent by the exchange to the called subscriber, to indicate the arrival of a call. Tones and Announcements. Audible backward signals (dial-tone, ringingtone, busy-tone, etc.) sent by an exchange to the calling subscriber, and indicating the progress of a call.

Digital Subscriber Line

Globally, the DSL market reached 63.8 million subscribers by March 2003, and future growth is expected to reach 200 million subscribers almost 20 of all phone lines by the end of 2005 (DSL Forum Report, 2003). xDSL refers to all types of DSL technologies, classified into two main categories symmetric (upstream and downstream data rates are equal) and asymmetric (upstream and downstream data rates are different). DSL services include asymmetric DSL (ADSL), rate-adaptive DSL (RADSL), high data-rate DSL (HDSL), symmetric DSL (SDSL), symmetric high data-rate DSL (SHDSL) and very high data-rate DSL (VDSL) with data rates scaling with the distance and specific to each technology. For example, ADSL technology supports downstream data rates from 1.5 Mbps to 9 Mbps and upstream data rates up to 1 Mbps. VDSL technology supports downstream rates up to 55 Mbps. Also, VDSL provides bandwidth performance equal to the optical fiber, but only over distances less than 1,500 meters. SDSL technology...

Subscriber Signaling For Supplementary Services

Up to this point, we have discussed subscriber signaling for POTS (Plain Ordinary Telephone Service) call control. Today, customers in many countries can subscribe to supplementary services, for which they are charged a monthly fee. Every local exchange has a database with entries for each subscriber, listing the supplementary services available to that subscriber. This section examines some of these services, and outlines the additions to subscriber signaling to support them.

Total telephone subscribers per 100 inhabitants

The total number of telephone subscribers per 100 inhabitants (total teledensity) is the sum of fixed lines in operation and cellular mobile subscribers divided by the population of a country, and multiplied by 100. The possibility of double counting is the major drawback of using total teledensity since a subscriber could have both a fixed and mobile telephone. One way to overcome this is to use effective teledensity which may be defined as either fixed telephone subscribers or cellular mobile telephone subscribers per 100 inhabitants, whichever is highest. Effective teledensity is a better measure of total coverage, but Globally, access to telephone networks (fixed and mobile) tripled in the ten-year period 1993-2002 from 11.6 subscribers per 100 inhabitants to 36.4 (Figure 4.2, left). The most rapid growth occurred in the use of mobile phones due to the evolution towards second-generation wireless systems, liberalization of mobile telecommunication markets and introduction of...

Figure 42 Telephone subscribers

Main lines, cellular mobile and total telephone subscribers per 100 inhabitants, 1993-2002, world (left) and annual average growth in mobile cellular subscribers, 1995-2002, world regions, per cent (right) Telephone subscribers per 100 inhabitants, world Telephone subscribers per 100 inhabitants, world Average annual growth rate of mobile subscribers, 1995-02, Average annual growth rate of mobile subscribers, 1995-02,

Subscriber line circuit 461 Line circuit functions

Each subscriber is connected to an individual line circuit in the Central Office. Depending on the type of switching system used there may be different types of line circuits used to handle different types of subscribers line individual, 2-party, multi-party, PBX, DDI and coin box, etc. The line circuit in a modern electronic exchange carries out the following functions described by the mnemonic BORSHT B Battery supply to the subscribers line The line circuit also has a function to identify the calling subscriber for centralized billing purposes. These functions are detailed in the following sections. An outline of a subscriber's line circuit is shown in Figure 4.13.

Subscriber access networks

In the years 1900, emphasis was placed to introduce economical solutions in this network layer. However, the last couple of years witnessed fundamental changes inasmuch as the mechanisation introduced in network development has drastically reduced the building costs. On the other hand, several services required the realization of broadband links reaching the subscriber homes. The most important of these services is the cable television that will reach all homes within a short period. The network structure of cable television is presented in Sec. 4.7. Another novel requirement is the surfing over the world wide web requiring special network structures and broadband accessibility. These topics are detailed in Secs. 4.11 and 4.12. Finally, the technologies applied in diverse network layers have, in the course of times, amalgamated so the principles presented in Secs. 1.9 and 4.3 now cover all aspects that were originally planned to be included in this Chapter. A futher outcome of the...

Subscriber Call Progress Tones and Push Button Codes North America

Table 7.7 shows the audible call progress tones commonly used in North America as presented to a subscriber. Subscriber subsets are either dial or push-button, and they will probably be all push-button in the next 10 years. A push-button actuates two audio tones simultaneously, similar to the multifrequency systems described previously with interregister signaling. However, the tone library used by the subscriber is different than the tone library used with interregister signaling. Table 7.8 compares digital dialed, dial pulses (breaks), and multifrequency (MF) push-button tones.

Signaling In The Subscriber Loop 781 Background and Purpose

In Section 5.4 we described loop-start signaling, although we did not call it that. When a subscriber takes a telephone off-hook (out of its cradle), there is a switch closure at the subset (see the hook-switch in Figure 5.3), current flows in the loop alerting the serving exchange that service is desired on that telephone. As a result, dial tone is returned to the subscriber. This is basic supervisory signaling on the subscriber loop. A problem can arise from this form of signaling. It is called glare. Glare is the result of attempting to seize a particular subscriber loop from each direction. In this case it would be an outgoing call and an incoming call nearly simultaneously. There is a much greater probability of glare with a PABX than with an individual subscriber.

A Subscriber stages digitalISDN and analogue subscriber lines

Figure 3.2.2 shows the functional layout of the Subscriber Access Unit. To meet the requirements of two kinds of subscriber accesses we have two types of subscriber line circuits (ISDN and analogue subscriber line), and two kinds of line boards. The number of line circuits on a board is determined by the exchange type, and also by the manufacturing technology. Typically, boards comprising 4, 8 or 16 line circuits are applied. Figure 3.2.2. Functional layout of a subscriber access unit Figure 3.2.2. Functional layout of a subscriber access unit Data transfer between the ISDN terminal equipment connected to the digital service access points and the subscriber stage takes place via the D-channel of the connection, according to the rules of the DSS1 subscriber signalling system. Communication between the terminal equipment connected to the analogue service access points and the subscriber stage takes place via DC and voice frequency signalling transmitted over the subscriber line. To meet...

Verification of Subscriber Identity

When a subscriber is added to a home network for the first time, a Subscriber Authentication Key (Ki) is assigned in addition to the IMSI to enable the verification of the subscriber identity (also known as authentication). All security functions are based on the secrecy of this key. At the network side, the key Ki is stored in the Authentication Center (AUC) of the home PLMN. At the subscriber side, it is stored on the SIM card of the subscriber. The process of authenticating a subscriber is essentially based on the A3 algorithm, which is performed at the network side as well as at the subscriber side (Figure 6.21). This algorithm calculates independently on both sides (MS and network) the Signature Response (SRES) from the authentication key Ki and a Random Number (RAND) offered by the network. The MS transmits its SRES value to the network which compares it with its calculated value. If both values agree, the authentication was successful. Each execution of the algorithm A3 is...

Subscriber access network

From traffic aspects the subscriber or access network has traditionally star-structure there is one traffic circuit for any one of the subscriber end-points to the subscriber stage, without path-selection. Versions of technical realisation may be found from the copper-line through optical fibre to wireless systems, including combinations of those, as well. In copper-line networks one pair is available for a subscriber. Cost-effectiveness of subscriber network may be improved by applying shared usage elements. Considering specific traffic demands and behaviour of subscribers in a given sub-area, the required grade of service may be reached in certain sections with less number of channels than the number of subscribers by using traffic concentrating devices. Application of electronic devices made possible conveying greater distances economically and thus serving greater areas by one exchange. Important representative of electronic devices performing traffic concentration is the remote...

Calls Involving Analog Subscribers

At present, the number of ISDN users is still very small, and the majority of calls carried on ISUP trunks are between two analog subscribers. This section explores ISUP signaling for calls in which one or both parties are subscribers. 11.4.1 Call between Two Subscribers Figure 11.4-1 shows a call between subscribers, in which trunks T, and T2have ISUP signaling. Set-up of Connection. Subscriber S, has originated a call. We first examine the IAM sent by originating exchange P see Table 11.2-2. Par.5 holds the called party number dialed by S,. Par.l (access transport) and Par.24 (user service information) are absent because subscriber signaling does not provide bearer capability, subaddresses, and compatibility information. Subscriber Local Exchange

Subscriber Authentication Authorization and Accounting

NavisRadius will be used for subscriber Authorization, Authentication and Accounting (AAA) to prevent unauthorized use of the (ORiNOCO Wireless Client) wireless network. All users will be required to authenticate before being allowed entry to the network. Non-subscribers that happen to be in possession of an 802.11b compliant network card will be prevented from using the service by the same authentication process.

Digital Subscriber Lines

This section examines the final high-speed Internet access area, DSLs. DSL network components and architecture are presented and contrasted with cable modem networks for delivering high-speed digital communications to residential subscribers. DSL is just a pair of modems running over existing telephone wiring in a broader range of frequencies than is used for voice communications alone. Thus, DSL signifies a modem pair, and not a type of telephone line. This means that two modems attached to a line create a DSL. When a telephone company buys xDSL, it buys modems and attaches them to the lines they already own. Thus, DSL is really a new type of modem and not a line. ADSL (Asymmetric Digital Subscriber Line) HDSL (High-bit-rate Digital Subscriber Line) SDSL (Single-line Digital Subscriber Line) VDSL (Very-high-bit-rate Digital Subscriber Line) IDSL (ISDN Digital Subscriber Line) RADSL (Rate-Adaptive Digital Subscriber Line) UDSL (Universal Digital Subscriber Line) (Also called...

Telephone Subscriber Services

The customer oriented definitions of subscriber services are the offered possibilities, capabilities, functions or operations provided by the telecom companies. The public telephone services described in point 5.2.2 above can be used by the customers on the bases of customer contract except the usage of public phones. The general conditions of the subscriber contract contain the subscriber services, the mode of usage and the fees. The subscriber might be a natural person or legal entity or enterprise without legal personality in a contractual relationship with a service provider. The subscriber pays the bill. The user is the person who uses the telephone service and might be different from the telephone subscriber. One part of the services is included in the subscriber contract so the subscriber can use them without extra procedure. The supplementary services have to be ordered from the service provider.

Subscriber supplementary services

The set of public telephone services provided on the request of the subscriber concerning call set-up, charging and operation and characterized by the following items The operational services like transfer the location of service, the change of subscriber on the same location, modification of contract cover mostly administrative task and less technical part. The subscriber supplementary services concerning call set-up are discussed The set of subscriber supplementary services may show high level of variety for different reasons. The set of services extended continuously by the development of technology and the market driven demands but their implementation in networks might be in different time-schedule and mode. A subscriber in a given moment is connected to the telecom network by a well-defined mode. The available set of supplementary services is influenced by The network capabilities and the technology of the subscriber access (e.g. access to analog or digital network, or access to...

Calls Originated by Subscribers ISUP Signaling All the

If the calling party is a subscriber, the procedures at the terminating exchange R are, with minor exceptions, as described above for speech or 3.1 kHz audio calls. On calls where the calling subscriber should hear busy-tone or reorder-tone, exchange R initiates the release of the connection. Exchange P provides the tone according to the information in Par.8 (cause) of the received REL message, releases trunk Tj (as in Fig. 11.7-1), and awaits the disconnect signal from the calling subscriber. If the subscriber should hear ringing-tone or an announcement, it is provided by terminating exchange R (as in Fig. 11.7-2). When exchange P receives the subscriber's disconnect signal, it initiates the release of the connection.

Calls between a User and a Subscriber

We now consider calls between a user and a subscriber. The call configuration is as in Fig. 11.4-1, except that one party is a subscriber, and the other party is a user. Since the connection has ISUP signaling all the way, terminating exchange R always knows whether the remote (calling) party is a subscriber or ISDN user, from bit I of Par.12 (forward call indicators) in the IAM message. Likewise, originating exchange P knows the type of the remote (called) party from bit M of Par.3 (backward call indicators) in the ACM message. Since some user actions depend on whether the distant party is a user or a subscriber, a local exchange always informs its user if the distant party is nonISDN. This is done by including an IE. 11 (progress indicator), in the CONN message to the TE of a calling user, or in the SETUP message to the DSL of the called user. The TE then presents this information to its user. In calls from a subscriber to a user, the IAMs do not include a Par.l (access transport),...

Digital Subscriber Line Components

DSL has several key components installed at the telephone company CO and in the subscriber residence. These components are shown in Figure 9-19. At the subscriber residence, an ADSL or DSL Network Interface Device (NID) is installed. This device is essentially the bandwidth splitter that splits off a voice-grade analog channel from the DSL channel that runs over the telephone wire into the telephone company CO. Connected to it are an analog telephone and an ADSL Network Termination (ANT) device. The network termination device is the DSL modem that converts the DSL data signal into 10-Base T Ethernet. The DSL signals travel over the telephone lines into the CO where they terminate in a Digital Subscriber Line Access Module (or Multiplexer), or DSLAM. The DSLAM is or contains the DSL modem at the telephone company CO. It splits the analog telephone channel from the signal and routes it to the telephone company CO switch. It also converts the data signal to 10-Base T Ethernet and routes...

Highdatarate digital subscriber line

High-data-rate digital subscriber line (HDSL) is essentially a method of providing T1 or E1 service access and is not really a customer access technology. As such it is mentioned here for completeness only. HDSL is defined by ITU-T G.991.1 and ANSI T1E1.4 Tech Report 28. It provides symmetric transmission at speeds of up to 2.048 Mbps of the distances up to 5 km without repeaters or 12 km using repeaters. It operates with two cable pairs per system and utilizes 2 binary, 1 quaternary carrierless amplitude modulation (2B1Q CAP) line coding, with 80 or 240 kHz modems.

Symmetric digital subscriber line

Symmetrical digital subscriber line (SDSL) service provides single pair HDSL service over the existing copper circuit between and the Central Office and the customer's premises. Speeds of up to 768 kbps are achievable in both directions for distances up to 12 000 ft or 3.6 km. Some SDSL implementations, such as Lucent's AscendTM, allow two SDSL ports to be combined over two pairs to give a full symmetrical T1 channel capacity of 1.544 Mbps. Figure 7.3 illustrates a full-duplex T1 SDSL configuration.

Digital Subscriber Line Technology

Local loop configurations vary tremendously worldwide. In some places, 18,000 feet covers virtually every subscriber, while in the U.S., 18,000 feet may cover less than 80 of local loops. Most local loops have loading coils that must be removed to install any DSL service as well as ISDN. Telephone companies have programs to shrink average loop length largely to

Veryhighspeed digital subscriber line

Very-high-speed digital subscriber line (VDSL) transmits high-speed data over a short twisted-pair copper telephone line. The maximum downstream rate being considered is up to 55 Mbps over lines up to 1000 ft or 300 m. Upstream data rates under consideration range from 1.6 Mbps, 19.2 Mbps through to the full downstream rates. Like ADSL, both the data channels will be separated in frequency from the POTS and or ISDN circuits, to enable service provision on existing cable plant. VDSL is an enabling technology for FTTC installations as discussed in Section 7.9.

Presence and List Management

Presence and list management are service enablers that aim to facilitate communication and to support communication services like Multimedia Telephony and OMA PoC. Both service enablers are specified by the PAG group in OMA. OMA actually specifies two different presence solutions. The one discussed here is the presence solution based on SIP, which is often referred to as OMA Presence Simple. The set of SIP-based presence specifications contains the OMA Presence Simple requirements document 138 , the OMA Presence Simple architecture document 146 and the OMA Presence Simple technical specifications 147, 148, 151 . The list management is referred to as XML Document Management (XDM). The set of OMA XDM specifications include the OMA XDM requirement document 154 , the OMA XDM architecture document 153 and the OMA XDM technical specifications 155, 152, 141 .

Designing a Subscriber Loop

Figure 5.4 is a simplified model of a subscriber loop. Distance D in the figure is the length of the loop. As we mentioned above, D must be limited in length owing to (1) attenuation of the voice signal on the loop and (2) dc resistance of the loop for signaling. Figure 5.4 Subscriber loop model. Figure 5.4 Subscriber loop model. This, then, is the signaling limit for 26-gauge (copper) subscriber loop. It is not the loss (attenuation) limit, or what some call the transmission limit. Another guideline in the design of subscriber loops is the minimum loop current offhook for effective subset operation. For example, the North American 500-type subset requires at least 20 mA for efficient operation. Calculating the Loss Limit. For our discussion here, the loss at 1000 Hz of a subscriber loop varies with diameter of the wire and the length of the loop. Table 5.2 gives values of loss (attenuation) per unit length for typical subscriber low-capacitance wire pair. Loss per Unit Length...

Communication Diversion Communication Forwarding on Mobile Subscriber Not Reachable

Call Forward Not Reachable

Figure 4.21 shows an example of call forwarding using the Communication Forwarding on Mobile Subscriber Not Reachable method. In this case the Multimedia Telephony user B Figure 4.21 Signaling flow for call forwarding using the Communication Forwarding on Mobile Subscriber Not Reachable method. Figure 4.21 Signaling flow for call forwarding using the Communication Forwarding on Mobile Subscriber Not Reachable method. 6. After a while without any response to the SIP INVITE request a timer expires in IMS core B. Then the TAS B decides that Multimedia Telephony client B1 is not reachable and executes the Communication Forwarding on Mobile Subscriber Not Reachable logic.

Cookbook Design Methods for Subscriber Loops

Resistance design (RD) dates back to the 1960s and has since been revised. It was basic North American practice. Our inclusion of resistance design helps understand the cookbook design concept. At the time of its inception, nearly all local serving area switches could handle loops up to 1300 Q resistance. In virtually every case, if the RD rules were followed, the attenuation limit of 8 dB would be complied with. The maximum resistance limit defines a perimeter around a local switch which is called the resistance design boundary. For subscribers outside of this boundary served by the switch, long route design (LRD) rules were imposed. LRD is briefly covered in Section 4. The design loop is the subscriber loop under study for a given distribution area to which the switch design limit is applied to determine conductor sizes (i.e., gauges or diameters). It is normally the longest loop in the cable of interest. 5. The theoretical design is the...

Subscriber Loop Design

The cables that connect the telephone handsets or other devices to the local switching office or end office is referred as subscriber loop or local loop. Every suscriber has his own pair of wires to the local switching office. Twisted pair local loop is an excellent transmission medium for analog voice signals. But it is limited to low frequency audio signals. The introduction of fiber cable needs a device at subscriber premises to convert electrical energy into light energy and this is the additional cost to the customer. But for high speed data transmission, switched cable TV, videophone, teleconferencing the fiber optic local loop has become essential. One end of each subscriber loop is terminated on a Main Distribution Frame (MDF) at the exchange. The drop wires (DW) from the telephones are connected to the distribution point (DP) which is located near the subscriber's premises. The distribution points at various locations are connected together by a distribution cables (DC) and...

Home Subscriber Server

The Home Subscriber Server (HSS) is the main data storage for all subscriber and service-related data of the IMS. The main data stored in the HSS include user identities, registration information, access parameters and service-triggering information 3GPP TS 23.002 . HLR functionality is required to provide support to PS domain entities, such as SGSN and GGSN. This enables subscriber access to PS domain services. In similar fashion the HLR provides support for CS domain entities like MSC MSC servers. This enables subscriber access to CS domain services and supports roaming to GSM UMTS CS domain networks. The AUC stores a secret key for each mobile subscriber, which is used to generate dynamic security data for each mobile subscriber. Data are used for mutual authentication of the International Mobile Subscriber Identity (IMSI) and the network. Security data are also used to provide integrity protection and ciphering of the communication over the radio path between the UE and the...

Digital Subscriber Line Dsl Technology

XDSL is a generic abbreviation for the many variations of digital subscriber line technology. DSL refers to the technology used between a customer premises and the telephone company enabling more bandwidth over the already installed copper cabling. Thus XDSL is a technology backed by telephone companies to provide next generation high bandwidth services to the home and business using the existing telephone cabling infrastructure. This technology accomplishes high speed delivery of data, voice, video and multimedia. The G.992.1(G.dmt), G992.2 (G.lite) Sandards by ITU, ANSI T1.413-1998 from ANSI, ADSL metallic interface from universal ADSL working group are the important standards provided by the standards organization. Other standards group for XDSL are European Telecommunication Standards Institute (ETSI), Internet Engineering Task Force (IETF), ADSL MIB work group and ATM Forum. In this section, the comparison of XDSL over other existing technologies, Types of XDSL technologies are...

Subscriber Data in GSM

Imsi Msisdn Sim

Besides data of the address type, which is the most important subscriber data of any communication network, a whole series of other service- and contract-specific data exists in GSM networks. Addresses serve to identify, authenticate, and localize subscribers, or switch connections to subscribers. Service-specific data is used to parameterize and personalize supplementary services. Finally, contracts with subscribers can define different service levels, e.g. booking of special supplementary services or subscriptions to data or teleservices. The contents of such contracts are stored in appropriate data structures in order to enable correct realization or provision of these services. The association of the most important identifiers and their storage locations is summarized in Figure 3.7. Subscriber-related addresses are stored on the SIM and in the HLR and VLR as well. These data (IMSI, MSISDN, TMSI, MSRN) serve to address, identify, and localize a subscriber or a mobile station....

The Home Subscriber Server and the Subscription Location Function

The Home Subscriber Server (HSS) is a database that stores the profile of all the users of a domain. A user's profile includes security-related information such as cryptographic keys, service-related information such as to which services the user is subscribed, and other information such as the S-CSCF that has been allocated to the user or the user's location.

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 use of derived feeder circuits, such as radio, a fiber-optic cable or a digital subscriber line, in order to meet the objective attenuation limits as set out in the national transmission plan. Some alternative RSU configurations are shown in Figure 4.5.

Digital Subscriber Signaling

Adsl Network Architecture

The public switched telecommunication networks in some countries have been converted (often only partially) into Integrated Services Digital Networks (ISDNs) 2,9,10 . An ISDN serves conventional (analog) subscribers and ISDN users. Digital ISDN users can communicate with each other in two modes. In circuit mode, the network sets up a dedicated connection for the call, which can be used for voice and data communication. In packet-mode communication (Chapter 20), the users communicate with short bursts of data, called packets. There are 64-kb s ISDN terminals (terminal equipment TE) of several types, for example, digital telephones, high-speed facsimile terminals, and high-speed computer modems (Fig. 2.1-4). A digital subscriber line (DSL) connects the user's TE to the local exchange. ISDN DSLs are two-wire or four-wire circuits that allow simultaneous information transmission at 144 kb s in both directions, although, due to overhead bits, the total transmission rate is somewhat higher....

Analog Subscriber Lines [45

Figure 1.4-3 shows a connection between two subscribers served by an analog local exchange. The subscriber lines (SLs) and the path (P) across the exchange are two-wire circuits. The characteristics of microphones and receivers are such that a listener receives a sufficiently strong acoustical signal when at least 1 of the electrical signal power produced by the talker's microphone reaches the listener's receiver. This corresponds to the attenuation in a circuit of about 15 miles. Most subscriber

Subscribers loop design limits

This section will consider the design limits of the subscriber's loop using twisted-pair cable, since this is the only reason for using such cable in a telecommunication network. The maximum attenuation allowed in the subscriber's loop is set in the national transmission plan. This is typically 8 dB measured at 1000 Hz. Using the values of attenuation for the low-capacitance cable (40 nF km) given in Table 3.1 for the different conductor sizes, we can derive the corresponding maximum cable distances to meet the 8 dB limit as given in Table 3.3. The loop resistance limit or signaling limit is based on the requirement for a minimum current flow in the subscriber's loop to activate both the telephone instrument and the loop detector at the local switch. This minimum loop current is generally 20 mA. Using a - 48 V exchange battery this equates to 2400 Q. From this we need to deduct the resistance of the feed bridge in the exchange, typically 400 Q, and the resistance of the subscriber's...

Extending the Subscriber Loop

In many situations, subscribers will reside outside of the maximum subscriber loop lengths described above. There are five generally accepted methods that can be used to extend these maximums. They are 4. Use digital subscriber line (DSL) techniques (covered in Chapter 6). Amplifiers in the subscriber loop extend the transmission range. Perhaps better said, they compensate for loop loss. Commonly such amplifiers are set for about 7-dB gain. Care must be used to assure that dc signaling is not lost. Inductive Loading. Inductive loading of a subscriber loop (or metallic VF trunk) tends to reduce the transmission loss at the expense of amplitude-frequency response beyond 3000-3400 Hz, depending on the loading technique employed. Loading a particular subscriber loop (or metallic pair trunk) consists of inserting series inductances (loading coils) into the loop at fixed distance intervals. Adding load coils tends to

Maximum Subscriber Loop Formula

The cable sizes of 19, 22, 24 and 26 gauge are the most commonly used cable for different dc resistance of various subscribers. The higher the gauge number the smaller the wire diameter. With 26-gauge wire a loop distance of only about 6.4372 Km (4 miles) is possible. With 19-gauge wire the loop distance might be extended to as much as about 28.96 Km (18 miles). Maximum permissible loop length. The method of determing the maximum subscriber loop length using the attenuation or loop loss is called the basic transmission design, the maximum loop length is calculated from the formula Attenuation limits arise from the ac response of the loop and refers to loop loss in decibels. The amplifiers loop extenders or inductive loading coil methods are used to admit the loop length to increase beyond the limit. Inductive loading is the process of inserting series inductances (loading coils) into the loop at fixed intervals. These will reduce the transmission loss on subscriber loops. This methods...

Subscriber Loop Design 541 Basic Design Considerations

We speak of the telephone subscriber as the user of the subset. As we mention in Section 1.3, telephone subscribers are connected via a subscriber loop to a local serving switch that can connect a call to another subscriber served by that same switch or via other switches through the PSTN to a distant called subscriber. The conventional subscriber loop is a wire pair. Present commercial telephone service provides for both transmission and reception on the same pair of wires that connect the subscriber to her his local serving switch. In other words, it is two-wire operation. The subscriber loop is a dc loop in that it is a wire pair supplying a metallic path2 for the following The typical subscriber loop is supplied its battery voltage by means of a battery feed circuit illustrated in Figure 5.3. Battery voltages have been standardized at -48 Vdc. It is a negative voltage to minimize cathodic reaction. This is a form of corrosion that can be a thermal noise source.

Subscriber Access to the ISDN

To allow flexibility, digital pipes between customers and the ISDN office (the subscriber loops) are organized into multiple channels of different sizes. The ISDN standard defines three channel types, each with a different transmission rate bearer channels, data channels, and hybrid channels (see Table 10.3-1).

Subscriber Identity Confidentiality

As in GSM, the identity of the subscriber is held confidential. This is done by using temporary identities on the radio channel. In particular, the user's IMSI is not transmitted unencrypted, but a Packet Temporary Mobile Subscriber Identity (P-TMSI) is assigned to each user by the SGSN. This address is temporary and is only valid and unique in the service area of this SGSN. From the P-TMSI, a Temporary Logical Link Identity (TLLI) can be derived. The mapping between these temporary identities and the IMSI is stored only in the MS and in the SGSN.

Protection of Subscriber Identity

The intent of this function is to prevent disclosing which subscriber is using which resources in the network, by listening to the signaling traffic on the radio channel. On one hand this should ensure the confidentiality of user data and signaling traffic, on the other hand it should also prevent localizing and tracking of a mobile station. This means above all that the International Mobile Subscriber Identity (IMSI) should not be transmitted as clear text, i.e. unencrypted. Instead of the IMSI, one uses a Temporary Mobile Subscriber Identity (TMSI) on the radio channel for identification of subscribers. The TMSI is temporary and has only local validity, which means that a subscriber can only be uniquely identified by TMSI and the Location Area ID (LAI). The association between IMSI and TMSI is stored in the VLR. Figure 6.19 Encrypted transmission of the temporary subscriber identity Figure 6.19 Encrypted transmission of the temporary subscriber identity The subscriber identity is...

Subscriber Loop Design Techniques

Consider the following drawing of a simplified subscriber loop Of course it will follow that the greater the wire diameter of the loop pair, the less resistance there is per unit length also, the less attenuation there is per unit length. On a particular subscriber loop we must set an attenuation limit and a minimum current flow. The current flow is usually stated as a resistance in ohms. We expect a common battery voltage of -48 V. This is what a high-impedance voltmeter will read anywhere in the loop when no current is drawn, such as a telephone instrument off hook. When designing a subscriber loop, we would be vitally interested on what its maximum length would be. There are two variables that must be established (1) The maximum loop resistance. This value is a function of the circuit in the switch where the loop terminates. One current value that comes to mind is 2400 Q. (2) The maximum loss or attenuation on the loop. This will be taken from the national...

Digital Subscriber Line Offerings

Asymmetric Digital Subscriber Lines ADSL transmits an asymmetric data stream, with higher speed downstream to the subscriber and much lower speed upstream. The reason for this has to do with the installed cable. Twisted pair telephone wires are bundled together in 50-pair cables. Cables coming out of a CO have hundreds to thousands of pairs bundled together. Thus, individual lines from a CO to a subscriber are spliced together from several cable sections as they spread out from the CO. Bellcore claimed the average telephone subscriber had 22 splices in their line. Twisted pair wiring is designed to minimize interference between signals caused by radiation or capacitive coupling. The process is not perfect and signals do couple. The coupling effect increases as frequencies and the length of line increase. This requires ending the DSL assigned local loop at the customer premise. (Analog local loops are usually run through a neighborhood, and then tapped into to deliver analog telephone...

Copper subscriber loop plant

The conventional subscriber distribution plant is made up of twisted-pair copper. The diameter of the copper wire determines its resistance and distribution networks commonly comprise either 0.5 mm (24 AWG) or 0.63 mm (22 AWG) conductors. Access points are designed into the network in the form of cross connection cabinets to give more flexibility in the network and provide cost-effective circuit provision. The dedicated distribution cable to the customer's premises is generously provisioned to allow for future growth and maintenance spares. This distribution cable terminates at the cross connection cabinet where it is connected by means of a jumper wire to a feeder cable back to the Central Office. This is illustrated in Figure 4.2. Conventional subscriber loop plant configuration Conventional subscriber loop plant configuration The distribution cable can be dedicated for individual subscribers, and is frequently designed on the basis of two cable pairs per residence. The distribution...

Signals on Analog Subscriber Loop

Traditionally the analog subscriber loop is a twisted pair of copper wires so this loop is suitable for transmission of voice band (300-3400 Hz), DC and out of band signalling. Out of band signalling Ringing the bell the telephone switch provide ringing current on the loop. The frequency of ringing current is usually 25 Hz. Different cadences can be used for supplementary services differentiate calls, e.g. call-back, held calls, and identification of call number at multiple subscriber number service. Out of band signal is used to indicate the start of charging in the form of 12 kHz pulses. signal. The display can show the number of the calling subscriber, signal for indicating waiting messages in the Voice Mail System and even short messages like SMS in the GSM system.

Size Of An Exchange Area Based On Number Of Subscribers Served

The size of an exchange area (also called a serving area) obviously will depend largely on subscriber (or potential subscriber) density and distribution. Subscriber traffic is another factor to be considered. If statistics on subscriber traffic intensity are not available, use Table 2.8 based on ITU-T data. Exchange sizes are often in units of 10,000 lines. Although the number of subscribers initially connected should be considerably smaller than when an exchange is installed, 10,000 is the number of subscribers that may be connected when an exchange reaches exhaust, where it is filled and no more subscribers can be connected. Ten thousand is not a magic number, but it is a convenient one. It lends itself to crossbar (switch) unit size and is a mean unit for subscriber densities in suburban areas and mid-sized towns in fairly well developed countries. More important, though, is its significance in telephone numbering (the assignment of telephone numbers). Consider a seven-digit...

Signaling In The Subscriber Loop 91 Background and Purpose

Figure Ground Interface

In Chapter 2 we described loop start signaling, although we didn't call it that. When a subscriber takes a telephone off hook (i.e., out of its cradle), there is a switch closure in the subset (see Figure 4.2 and Section 2 of this chapter) current flows in the loop, alerting the serving exchange that service is desired on that telephone. As a result, dial tone is returned to the subscriber. This is basic supervisory signaling on the subscriber loop. A problem can arise from this form of signaling. It is called glare. Glare is the result of attempting to seize a particular subscriber loop from each direction. In this case it would be an outgoing call and an incoming call nearly simultaneously. There is a much greater probability of glare with a PABX than with an individual subscriber.

Subscriber plant 431 Subscriber loop

The subscriber plant has conventionally used twisted-pair copper. This provides the DC power to operate the basic telephone instrument from the Central Office, conveys the AC ringing voltage used to operate the telephone bell to indicate incoming calls and conveys loop signaling to the Central Office so as to indicate when the telephone is on- or offhook. This is used to indicate when the customer wishes to initiate a call, by going offhook or to terminate a call by replacing the telephone handset that is going on-hook. The metallic circuit can also be used to convey loop pulsing from the old style rotary telephone dial. As the telephone dial rotated it caused the DC current in the subscribers loop to be made and broken at about 10 pulses per second to indicate the number of the required called party. This is called loop decadic signaling, but has largely been replaced by the use of touch-tone signaling in which two-tones are simultaneously transmitted for each key pressed on the...

Battery supply for subscribers line

The line circuit uses a feed-bridge to supply the exchange battery voltage to the subscriber's line. This battery voltage is used to operate the conventional telephone instruments, and is used for the subscriber line signaling to identify whether the telephone instrument is 'on-hook' or 'off-hook'. The battery supply needs to be coupled through a high-impedance to the line, to prevent the low impedance of the battery shunting the speech. This task is done by means of a feed-bridge and usually involves two high impedance relay coils, providing supervision of the subscriber's loop. The relay will be operated by a low line impedance and released by a high impedance from the subscriber. This is illustrated in Figure 4.14. Outline of subscriber's line circuit Outline of subscriber's line circuit Subscriber's line feed-bridge

Subscriber Signaling

The vast majority of the customers of telecommunication networks are subscribers who are attached to their local exchanges by analog subscriber lines. The signaling between subscriber and local exchange is known as subscriber signaling 1-4 . The original, and still predominant, application of subscriber signaling is plain old telephony service (POTS) calling. However, subscriber signaling today also supports supplementary services such as call waiting, call forwarding, caller identification, etc. 3.1 BASIC SUBSCRIBER SIGNALING 3.1.1 Signaling for an Intraexchange Call Figure 3.1-1 shows the signaling for an intraexchange call between subscribers S, and S2. The directory number of called subscriber S2 is 347-9654. Calling subscriber Sj starts by going off-hook (lifting the handset of the telephone from its cradle). The off-hook is interpreted by the exchange as a request-for-service (a call origination, or the activation deactivation of a subscriber service). In response, the exchange...

Mailing lists

Several mailing lists might be of interest to anyone who maintains a firewall instructions for subscribing to them are included in Appendix A. The most important list for folks interested in firewalls is the Firewalls mailing list. This list hosts discussions of the design, installation, configuration, maintenance, and philosophy of Internet firewalls of all types. The main drawback of the list is that it can be very busy sometimes more than 100 messages per day are posted to the list. To address the problem of volume, a Firewalls-Digest version of the list is also available Firewalls-Digest subscribers receive all of the same messages that subscribers to the main Firewalls list receive, but the messages are bundled into digest format (usually 10 to 20 messages are in a digest). Another list you should almost certainly subscribe to is the CERT-Advisory mailing list. This is the list to which CERT-CC posts its new security advisories. If you are served by a response team other than...

Subscriber interface

Different kinds of terminal equipment are connected to the exchange via subscriber interface. The main circuitry functions of subscriber interfaces can be summarised by BORSCHT , where the meaning of these letters is the following B Battery supply, Battery Feed Supply of the subscriber loop R Ringing Ringing signal applied to subscriber line S Supervision, Signalling Checking Monitoring of the status of subscriber T Testing Testing of the subscriber interface Feeding of the subscriber loop Feeding bridge supplies terminal equipment with direct current via subscriber line. The feeding impedance is sufficiently high to Because of traditional reasons the DC parameters of conventional resistance feeding bridges can differ for each country 5.6.1 , moreover for the different types of telephone exchanges established in the same country. The most frequent DC parameters of telephone exchanges in Hungary are 48V, 2x250 ohms, 48V, 2x300 ohms and 56 V, 2x220ohms. Depending on the parameters of...

Preface To The Second Edition

Access systems (Chapter 8) have become a part of the local network architecture. Several access systems (AS) surround a local exchange, each one serving the analog and digital lines of a group of nearby subscribers. Such systems, once called 'remote line concentrators', used to have proprietary interfaces to the local exchanges. Interfaces and signaling have now been standardized, allowing a telecom to purchase access and switching hardware equipment from different product suppliers.

Introduction To Telecommunications

Figure 1.1-1 shows a small part of a telecommunication network. It consists of exchanges, trunks, and subscriber lines. Trunks are circuits between exchanges, and the group of trunks between a pair of exchanges is known as a trunk group (TG). Subscriber lines (SL) are circuits between a subscriber S and his local exchange (A, B, C). Exchanges D and E do not have subscriber lines, and are known as intermediate, tandem, toll, or transit exchanges. Calls. A call requires a communication circuit (connection) between two subscribers. Figure 1.1-2 shows a number of connections in the network of Fig. 1.1-1 that involve subscriber Sp. In Fig. l.l-2(a), Sp is on a call with Sq who is attached to the same exchange. Calls of this type are known as intraexchange calls. The circuit for the call consists of the subscriber lines SLP and SLq, and a temporary path in exchange A. Cases (b) and (c) are calls between Sp and

Telecommunication Networks 111 Introduction

Figure 1.1-1 shows a small part of a telecommunication network. It consists of exchanges, trunks, and subscriber lines. Trunks are circuits between exchanges, and the group of trunks between a pair of exchanges is known as a trunk group (TG). Subscriber lines (SLs) are circuits between a subscriber S and the local exchange (A, B, C). Exchanges D and E do not have subscriber lines and are known as intermediate, tandem, toll, or transit exchanges. Calls. A call requires a communication circuit (connection) between two subscribers. Figure 1.1-2 shows a number of connections in the network of Fig. 1.1-1 that involve subscriber Sp. In Fig. 1.1-2(a), Sp is on a call with Sq who is attached to the same exchange. Calls of this type are known as intraexchange calls. The circuit for the call consists of the subscriber lines SLp and SLq and a temporary path in exchange A. Cases (b) and (c) are calls between Sp and subscribers attached to other local exchanges (interexchange calls). The circuit...

Acknowledgments for the First Edition

Brent says I would like to extend personal thanks to my friends and family, for keeping me going for a year and a half while I worked on the book to my staff at Great Circle Associates, for keeping my business going to the many hundreds of folks who've attended my Internet Security Firewalls Tutorial, for providing the impetus for this whole endeavor (and for keeping my bills paid ) and to the many thousands of subscribers to the Firewalls mailing list on the Internet, for providing a stimulating environment to develop many of the ideas found in this book. I also owe a lot of thanks to Debby Russell, our editor at O'Reilly & Associates, for all her help and guidance, and to our technical reviewers, for all their wonderful comments and suggestions. Most of all, though, I'd like to thank my very good friend and coauthor, Elizabeth Zwicky, without whose collaboration and encouragement this book probably never would have been finished, and certainly wouldn't have been as good.

Preface for Second Edition

GSM - the story goes on is the new title of the last chapter of this book - and GSM is indeed an ongoing success story. Since the release of the first edition of this book (2 years ago), the number of GSM subscribers has grown from 100 to 380 million worldwide. Nobody expected such an enormous number when the first GSM networks started their operation in 1991 In some countries the number of cellular phones is already higher than the number of fixed phones. Not only are the subscriber numbers experiencing a tremendous growth, but the technological evolution of GSM is also continuing. Many new services and applications have been developed and standardized during the last few years and are now being implemented in GSM networks and terminals.

The Costs of Telephony

In the 1930s in the United States, local telephone service cost between 18 and 24 per year, depending on the region. The more urbanized Northeast had lower rates than the more isolated Midwest and Far West, at least outside the cities. This cost does not sound like much, but the amount must be put in perspective. The average farm worker in 1930 made less than 200 per month, for an annual salary of under 2400. A half-gallon of milk cost 28 cents, and a pound of bacon went for 40 cents. In 1929, three hot dogs could be bought for a dime, and a soft drink to go with it cost 3 cents. Looked at this way, 20 a year for a telephone could buy at least 160 meals, or enough food to live on for about 3 months. This is one reason that right before the United States entered World War II in 1941, only some 40 percent of Americans saw fit to have a telephone in their homes. And that was only because of extraordinary efforts by the telephone companies to keep subscribers during the dark days of the...

Figure 12 Wireless Home Entertainment

In 2002 the number of cellular phone subscribers reached one billion worldwide. The cellular phone offers not only voice service but also data services in the current 2.5G system and the upcoming 3G system. These systems allow users to surf the net or check email using their cellular phones.

Dimensioning And Efficiency

By definition, if we were to dimension a route or estimate the required number of servicing channels, where the number of trunks (or servicing channels) just equaled the erlang load, we would attain 100 efficiency. All trunks would be busy with calls all the time or at least for the entire BH. This would not even allow several moments for a trunk to be idle while the switch decided the next call to service. In practice, if we engineered our trunks, trunk routes, or switches this way, there would be many unhappy subscribers. On the other hand, we do, indeed, want to size our routes (and switches) to have a high efficiency and still keep our customers relatively happy. The goal of our previous exercises in traffic engineering was just that. The grade of service is one measure of subscriber satisfaction. As an example, let us assume that between cities X and Y there are 100 trunks on the interconnecting telephone route. The tariffs, from which the telephone company derives revenue, are a...

Digital Mobile Global Evolution of Networks

The largest technological and organizational challenge is, however, the support of subscriber mobility. It can be distinguished between two kinds of mobility terminal mobility and personal mobility. In the case of terminal mobility, the subscriber is connected to the network in a wireless way - via radio or light waves - and can move with his or her terminal freely, even during a communication connection. The degree of mobility depends on the type of mobile radio network. The requirements for a cordless in-house telephone are much less critical than for a mobile telephone that can be used in a car or train. If mobility is to be supported across the whole network (or country) or even beyond the network (or national) boundaries, additional switching technology and administrative functions are required, to enable the subscribers to communicate in wireless mode outside of their home areas.

Other National Numbering Plans

Some countries have open numbering plans, in which subscriber numbers and area codes (sometimes called trunk or city codes) are not of fixed length. In these plans, the numbering areas usually have comparable geographical sizes. Heavily populated areas need subscriber numbers with six or seven digits, while four or five digits are sufficient in lightly populated areas. To limit the differences in length of national numbers, the area codes for areas with long subscriber numbers are usually shorter than those for areas with short subscriber numbers. An example of national numbers in an open numbering plan is shown below

Stupidity and Accidents

Denial of service incidents, for example, frequently aren't attacks at all. Apple's corporate electronic mail was rendered nonfunctional for several days (and their network provider was severely inconvenienced) by an accident involving a single mail message sent from a buggy mail server to a large mailing list. The mail resulted in a cascade of hundreds of thousands of error messages. The only hostile person involved was the system administrator, who wasn't hostile until he had to clean up the resulting mess.

Digital Transfer Systems

The switching and multiplexing techniques characteristic of the transmission systems within the network are all digital. Currently, the network employs a Synchronous Transfer Mode (STM) technique for switching and multiplexing these digital signals. The broadband networks of the future will continue to utilize a synchronous transmission hierarchy using the SONET standards defined by the International Telecommunications Union (ITU). SONET describes a family of broadband digital transport signals operating in 50 Mbps increments. As a result, wherever SONET equipment is used, the standard interfaces at the central office, remote nodes, or subscriber premises will be multiples of these rates. What distinguishes ATM from a synchronous approach is that subscribers have the ability to customize their use of the bandwidth without being constrained to the channel data rates.

Status of TelecommunicationICT development

By the end of 2004, the telecommunication industry had experienced continuous growth, as well as rapid progress in policy and technology development, resulting in an increasingly competitive and networked world. It is true and encouraging that overall, the digital divide has been reduced and continues to shrink. ITU statistics show that over the last 10 years, the digital divide between the developing and the developed countries has been narrowing in terms of fixed telephone lines, mobile subscribers and Internet users. In contrast to the slow fixed line growth, phenomenal growth rates in the mobile sector particularly, have been able to reduce the gap that separates the developed from the developing countries from 27 in 1994, to 4 in 2004. The fixed line gap has been reduced from 11 to 4 during the same period (Figure 1.1). While on average almost one out of three of the world's citizens is a mobile subscriber, there are major regional differences. Indeed, despite the rapid growth in...

Outline of the Thesis

In Part B Nyquist-Rate Digital-to-Analog Converters for VDSL Applications the wideband DAC is presented. For very high data rate digital subscriber line (VDSL) and wideband radio, wideband converters are needed. The simplest way to construct this type of DAC is to use a binary weighted source structure - a structure without feedback. However, to meet high performance specifications, certain improvement techniques, e.g., calibration, digital correction, etc., may be needed. This implies a certain redundancy and feedback. These issues are discussed in this part. The design of a 1.5V - 5V CMOS DAC chipset for VDSL and wideband radio applications is presented. It has been done in cooperation with Nianxiong Tan (GlobeSpan Semiconductor, Red Bank, NJ, USA, formerly Ericsson Components, Kista, Sweden). Important contributions concerning work on modeling and simulation on behavioral-level of the binary converter structure are presented. The results may be used to understand fundamental...

Current Loop Design Techniques Used In North America

Conventional analog trunk plant often uses heavier-gauge cable, say 22 AWG (American Wire Gauge), where the characteristic impedance (Z0) approaches 600 Q at 1000 Hz (Table 2.7, item d). Loaded subscriber loops have a Z0 approaching 1200 Q (Table 2.7, item f). Table 2.7, item g, shows impedance values of 135-150 Q. These lower values were selected because the impedance of the loop may go as low as 100 Q at the higher frequencies on higher-speed data circuits. (See also Refs. 13, 14, 15, and 16)

Signaling Components In Telephones

This section presents an overview of the circuitry in a telephone, focusing on the components for subscriber signaling. The major components in a telephone are shown in Fig. 3.2-1. The telephone is connected to a line circuit LC in the local exchange by a subscriber line that transfers the subscriber's speech and the subscriber signaling. The signaling functions of a telephone are the generation (controlled by the subscriber) of supervision signals and digits the conversion of received electrical tone, and announcement signals into acoustic signals, and -the conversion of the electrical ringing signal into a high-level acoustic signal that can be heard at some distance from the telephone.

Evolution Of Telecommunications And Networks

Why these two countries As discussed above the networking infrastructure is the critical factor for ubiquitous networking. According to the ITU, South Korea is the world's broadband leader by a significant margin along with a high number of mobile subscribers that even outnumbers fixed line subscribers (ITU, 2005b). Similar statistics apply to Japan (ITU, 2005c). The high penetration rate of broadband and the widely use of wireless technologies around the country allows facilitates the implementation of anywhere, anytime by anything, anyone ubiquitous networking. The success factors for these two countries are explained in detail in the ITU's case studies (ITU, 2005a ITU, 2005b). In South Korea, the Ministry of Information and Communication has the intention of realising their digital home plan , in which digital home appliances with communications capabilities are installed in apartment houses as a total, integrated system (Murakami, 2004). In the private sector, plans for ubiquitous...

Signaling Equipment At The Local Exchange

This section gives an example of the equipment for subscriber signaling at local exchanges. We consider a local SPC (stored program control) exchange with a digital switchblock (see Figs. 1.7-4 and 1.7-5). Figure 3.3-1 shows the local exchange and a number of subscriber lines. The lines are two-wire bidirectional analog circuits (c). They pass through their line Subscriber Lines Multiplex Digital Switchblock Circuits Subscriber Lines Multiplex Digital Switchblock Circuits Figure 3.3-1 Equipment for subscriber signaling at a local exchange with a digital switchblock. LC line circuits. H hybrid circuits. DMP digital multiplex port. TAC tone and announcement circuits. DRC DTMF receiver circuits. Figure 3.3-1 Equipment for subscriber signaling at a local exchange with a digital switchblock. LC line circuits. H hybrid circuits. DMP digital multiplex port. TAC tone and announcement circuits. DRC DTMF receiver circuits. The switchblock provides temporary 64 kb s digital paths between a...

Figure 41 A decade of ICT progress

Total telephone subscribers per 100 inhabitants Of all the MDG targets, number 18 is perhaps where the most progress was made during the 1990s. As shown in Figure 4.1, all of the developing regions of the world have grown their fixed and mobile telephone networks at a faster rate since 1992 than in the entire period before that date. In the exceptional case of East Asia (which includes China), the number of telephone subscribers per 100 inhabitants (i.e. total teledensity) in 2002 was 24 times higher than in 1992. In all cases except in the developing Pacific, total teledensity was at least three times higher in 2002 than it was in 1992.

Reception of Address Signals

On receipt of a request-for-service from a subscriber line, the processor marks the line as dialing, selects an idle digit receiver (DRC), orders the switchblock to set up a path between DRC and the line, and commands the DRC to send dial-tone. If the calling subscriber is using a telephone with dial-pulse address signaling, she rotates the dial, and this generates the digits as strings of break and make pulses that are detected by current detector (CD) in the line circuit (Fig. 3.3-2), and reported to the processor. On receipt of the first break, the path between the line and DRC is released. If the calling subscriber is using a telephone with DTMF signaling, she depresses the keys on the keypad. This generates DTMF digits that are received by DRC, and reported to the processor. On receipt of the first digit, the dial-tone is turned off. The path between the subscriber line and the DRC is released when the complete called number has been received. Digit receivers have...

Growth of the Global Telecommunications Market

Explosive expansion driven by internal growth and acquisition is forcing telecommunications providers to increase the productivity of their current support systems. Growth and acquisition mean that the number of subscribers grows for existing services, new services are provisioned on existing intrastructures, and completely new services on new infrastructures are deployed or acquired. Several support systems vendors have worked to capitalize on this opportunity with solutions that reduce complexity. These support systems vendors do not usually replace existing systems, but add functionality to accommodate new services, such as

Broadband Access Solutions

The circuit between a business or home and the local telephone company's end office is called a local loop. Originally, local-loop service carried only telephone service to subscribers. But today, several local-loop connection options are available from carriers. These include dial-up circuits, Integrated Services Digital Network (ISDN) and broadband. Last mile refers to the telecommunication technology that connects a subscriber's home directly to the cable or telephone company. Broadband transmission is a form of data transmission in which a single medium can carry several channels at once. The carrying capacity medium is divided into a number of subchannels each subchannel transports traffic such as video, low-speed data, high-speed data and voice (Stamper & Case, 2003). The broadband access options include Digital Subscriber Line (DSL), cable modems, broadband integrated services digital network (B-ISDN) line, broadband power line and broadband wireless, with a data rate varying...

Special Transmission Equipment

Figure 1.6-1 shows the transmission circuit (omitting the exchanges) for a typical long-distance connection with analog four-wire trunks. It consists of three parts. Parts 1 and 3 are two-wire circuits, containing the subscriber loops, and possibly two-wire trunks. Part 3 is a four-wire trunk. Hybrids Hj and H2 convert two-wire transmission into four-wire transmission. When subscriber Si speaks, the speech signal leaves Hj at port P, reaches port Q of H2, and then travels on the two-wire circuit to listener S2. However, a small part of the signal received at Q leaks to R, and thus returns to S1, who hears an echo of his speech. The leakage occurs because hybrid circuits are balancing circuits. For leak-free operation, the impedance presented by the two-wire circuit (at port T of hybrid H2) would have to match the design impedance of the hybrid for all voice-band frequencies. In each call, H2 is connected to a different two-wire circuit, and impedances of these circuits (which vary...

Broadband Wireless Access

WLL systems are based on a range of radio technologies such as satellite, cellular cordless and many narrowband and broadband technologies. One WLL approach is placing an antenna on a utility pole (or another structure) in a neighborhood. Each antenna is capable of serving up to 2,000 homes. Subscribers must have an 18-inch antenna installed on their homes.

Real Time Conferencing Services

A number of different real-time conferencing services are available on the Internet, including talk, IRC, web chat rooms, and the various services provided over the Multicast Backbone (MBONE). All of these services provide a way for people to interact with other people, as opposed to interacting with databases or information archives. Electronic mail and Usenet news are designed to facilitate asynchronous communications they work even if the participants aren't currently logged in. The next time they log in, the email messages or news postings will be waiting for them. Real-time conferencing services, on the other hand, are designed for interactive use by online participants.

Custom Calling Services

Custom calling services do not require special signaling hardware in telephone sets. Subscribers have to invoke some of these services by dialing special digit sequences called feature access codes. These codes are distinguishable from called numbers because their initial digits include a * (asterisk) or a (pound sign) when dialed from DTMF telephones, or special digit sequences (for example, 11) when dialed from dial-pulse telephones. Some services require the subscriber to send hookswitch flashes during the call. The local exchanges on which these services are offered have to be equipped with tone announcement circuits (TAC) that can provide a number of additional audible signals and messages to the subscriber. Call Waiting Service. Suppose that subscriber Sx is marked at his local exchange for call waiting service. When S is engaged in a call with subscriber S2 and is called by another subscriber S3, he is alerted by his local exchange with a call waiting tone. By sending a...

IMS and the IMS Multimedia Telephony Service

For enterprise users, Multimedia Telephony will also offer integration of email, support for remote workers, conferencing and collaboration features. Another important property of Multimedia Telephony is personal mobility. Professional users want to use the telephony and data communication services in the same way while traveling as when being in the office. A third important feature for enterprise users is the possibility to control what calls and sessions should be allowed at any given point in time. For example, when attending a business meeting or a conference, the users may want to allow only the most important calls or sessions to reach the receiver. Other, less important, calls may be routed to an answering machine where the sound is recorded and attached in an e-mail to the subscriber's e-mail address.

Other Applications Of Dtmf Signaling

DTMF address signaling was designed as a convenience feature for subscribers, providing a faster and more convenient way to send called numbers to their local exchanges. Another aspect of DTMF signaling, which was not considered at the time, is that the frequency pairs of DTMF digits are in the voiceband range (300-3400 Hz), and enable a calling subscriber to send DTMF signal to other exchanges along the connection. This is not possible with dial-pulse signaling because most of the energy of dial-pulse signals is concentrated at frequencies below 300 Hz, and these signals cannot be transferred reliably across the network. If the caller is using a pushbutton phone, he then sends the appropriate DTMF digit, and the PBX processor sets up a connection to an agent who is qualified to handle the requested service. This arrangement has become quite popular with business organizations, because it reduces the need for PBX attendants. Calling subscribers are less enthusiastic, especially when...

Figure 11 Overall the digital divide is shrinking

Mobile telephone subscribers per 100 inhabitants, 1994-2004 (left) and fixed telephone lines per 100 inhabitants, 1994-2004 (right) Mobile telephone subscribers per 100 inhabitants 3G technologies, which promise a wide range of innovative applications for users and a new source of revenues for operators, are unlikely to make a dramatic change for the world's poorest in the next couple of years. The majority of low-income countries has not yet deployed Third Generation services and the distribution of 3G subscribers worldwide highlights a stark 3G divide. Given the nascent state and low revenues of 3G services in most developed countries, operators are unsure about the potential and opportunities of 3G in developing markets and have been reluctant to invest in this sector. In contrast to its leading position in (second generation) mobile network availability and subscriber rates, Europe is not a leader in the area of 3G. Ninety-three percent of 3G subscribers are in Asia-Pacific and...

Numbering One Basis Of Switching

A telephone subscriber looking into a telecommunication network sees a repeatedly branching tree of links. At each branch point there are multiple choices. Assume that a calling subscriber wishes to contact one particular distant subscriber. To reach that distant subscriber, a connection is built up utilizing one choice at each branch point. Of course, some choices lead to the desired end point, and others lead away from it. Alternative paths are also presented. A call is directed through this maze, which we call a telephone network, by a telephone number. It is this number that activates the switch or switches at the maze branch point(s). Actually, a telephone number performs two important functions (1) It routes the call, and (2) it activates the necessary equipment for proper call charging. Each telephone subscriber is assigned a distinct number, which is cross-referenced in the telephone directory with the subscriber's name and address in the local serving exchange (switch), this...

Emergency numberUSA 3 Concentration And Expansion

Let us dwell on the term concentration a bit more. Concentration reduces the number of switching paths or links within the exchange and the number of trunks connecting the local exchange to other exchanges. A switch also performs the function of expansion to provide all subscribers served by the exchange with access to incoming trunks and local switching paths.

Access Networks And Line Concentrators

An access network (AN) is the part of the telephone network that connects the subscriber premises to the local exchange (LE). Initially, access networks consisted of subscriber lines (copper wire pairs) that terminated at the individual subscriber premises on one side and at the local exchange on the other side. Because of the cost involved in deploying the massive volume of copper wires needed to connect all local users to the LE, remote line concentrators (RLCs), sometimes known as pair gain systems or loop carriers, are often interposed between the subscriber premises and the LE. Concentrators, located close to the subscriber premises, collect a large number of line loops and reduce the volume of wires that go all the way from subscribers to the LE. Various techniques are used for concentration, all taking advantage of the fact that not all subscribers are involved in a call at the same time. The earliest types of RLCs were simple devices that served N subscriber lines with a pool...

Basic Switching Functions

In a local exchange, means are provided to connect each subscriber line to any other in the same exchange. In addition, any incoming trunk can connect to any subscriber line and any subscriber to any outgoing trunk. The switching functions are remotely controlled by the calling subscriber, whether he is a local or longdistance subscriber. These remote instructions are transmitted to the exchange by off hook, on hook, and dial information. There are eight basic functions of a conventional switch or exchange

Introductory Switching Concepts

End of the cord into the proper terminating jack and alerting the called subscriber by ring-down. Concentration is the ratio of the field of incoming jacks to cord positions. Expansion is the number of cord positions to outgoing (terminating) jacks. The terminating jacks and originating jacks can be interchangeable. The called subscriber at another moment in time may become a calling subscriber. On the other hand, incoming and outgoing trunks may be separated. In this case they would be one-way circuits. If not separated, they would be both-way circuits, accepting both incoming and outgoing traffic 2-4, 6 .

The Analog Telephone Network

More details about the rise and fall of the Bell System in 1984, and what it all means to VoIP, will be given in Chapter 3. It is enough to point out here that not every telephone in the United States belonged to AT&T. There were many independent telephone companies that offered services mainly in rural and less populated areas, since the Bell System deployed first in major metropolitan areas of the northeastern United States. Chief among the independents were GTE and, later, portions of Sprint. Sprint can trace its roots as a local telephone company back to the Brown Telephone Company in Kansas in 1899. Just like AT&T, GTE and Sprint had their own longdistance networks independent of AT&T Long Lines. But many independents continue to operate with as few as 200 or 300 subscribers. All independents, large and small alike, are now interconnected into one huge national network grid, if not directly, then through long-distance carriers such as AT&T, MCI, and Sprint. In fact, the last...

Advanced Intelligent Networks AINs

AIN is a collection of components performing together to deliver complex call-switching and handling services. The SSP is the CO that provides robust, call-switching capabilities. When switching decisions require complex call processing, the SSP relies on the SCP, a subscriber database, and it executes service logic. The SSP uses SS7 signaling, specifically Transaction Capabilities Application Part (TCAP) messages, requesting the SCP to determine the best way to handle the call. The process supports telephony features, including 800 (888 877) and 900 calling, credit debit card calling, call forwarding, and virtual private networks (VPNs). AIN has promised an architecture that is amenable to the rapid development and deployment of new services. How to maintain the stringent performance requirements of a CO service within this rapidly changing environment is a major challenge in the advancement of AIN.

Common Control Hard Wired

Whereas the register provides the dialed exchange number to the marker, the translator provides the marker information on access to the proper trunk group. Of course, the translator may also provide other information, such as the type of signaling required on that trunk group. The reader must bear in mind that modern common-control switches, particularly grid-type switches, use a control code that differs from the numerical dialed code. The dialed code is the directory number (DN) of the called subscriber. The equipment number (EN) is the number the equipment uses and is often a series of five one- or two-digit numbers to indicate location on the grid matrix of the speech-path network. The equipment codes are arbitrary and require changes from time to time to accommodate changes in number assignments. The changes are done on a patch field associated with the translator. One equipment number code is the two out of five code, which has ten possibilities to...

Call Charging European Versus North American Approaches

In Europe and in countries following European practice, telephone-call charging is simple and straightforward. Each subscriber line is equipped with a meter with a stepping motor at the local exchange. Calls are metered on a time basis. The number of pulses per second actuating the meter are derived from the exchange code or the area code of the dialed number. A local call to a neighbor (same exchange) may be 1 pulse (one step) per minute, a call to a nearby city 3 pulses, or a call to a distant city 10 pulses per minute. International direct-dial calls require checking the digits of the country code that will then set the meter to pulse at an even higher rate. All completed calls are charged thus the metering circuitry must also sense call supervision to respond to call completion that is, when the called subscriber goes off hook (which starts the meter pulses) and also to respond to call termination (i.e., when either subscriber goes on hook ) to stop meter pulses. Many...

Transmission Factors In Switching 141 Discussion

One more impairment which deserves consideration is return loss at input and output ports. This is especially true where a switch interfaces with subscriber loops. Here is the principal source of echo and singing. A digital switch with an analog input and A D conversion isolates the line and return loss, in general, is not really of major importance. In Chapter 9 we will present a major discussion of transmission factors in digital switching.

Figure 12 but major disparities remain

Mobile cellular penetration, by region, 1994-2004 (top left) and distribution of the 160 million 3G subscribers at the end of2004, by region (top right) Internet penetration by region, 2004 (bottom left) and distribution of broadband subscribers by region, 2004 (bottom right) Number of 3G subscribers, by subscribers at the end of 2004 160 million Nevertheless, by the end of 2004, the vast majority of broadband users were in the developed world and globally, Asia, Europe and the Americas represented no less than 99 percent of all broadband subscribers. Africa is home to a fraction of all broadband subscribers, and many African countries have not yet launched high-speed Internet services (Figure 1.2, bottom right).

Local Access And Transport Areas

Local Access and Transport Areas (LATAs) were established after divestiture to permit telephone companies to charge subscribers for access to local or regional exchanges and to the inter-exchange toll telephone network for sending and receiving intra-LATA and interstate calls. LATAs are geographic areas generally smaller than a state, but bigger than a county. A LATA is also smaller than an area code and bigger than a local exchange. LATAs follow telephone boundaries (not state boundaries).

Introduction To Switching

A local switch has an area of responsibility. We call this its serving area. All subscriber loops in a serving area connect to that switch responsible for the area. Many calls in a local area traverse no more than one switch. These are calls to neighbors. Other calls, destined for subscribers outside of that serving area, may traverse a tandem switch from there to another local serving switch if there is no direct route available. If there is a direct route, the tandem is eliminated for that traffic relation. It is unnecessary. To carry out these functions, a switch had to have some sort of intelligence. In a manually operated exchange, the intelligence was human, namely, the telephone operator. The operator was replaced by an automatic switch. Prior to the computer age, a switch's intelligence was hard-wired and its capabilities were somewhat limited. Today, all modern switches are computer-based and have a wide selection of capabilities and services. Our interest here is in the...

Applications for twistedpair cable

Twisted-pair cable is almost exclusively used for connection of the subscriber to the local switch. A major part of the investment in the telephone network is in the provision of the subscriber loop plant. Clearly the most cost-effective option needs to be taken in this area. By utilizing digital feeder systems using either PCM over the existing copper, or for new work fiber-optic cables, it is possible to utilize smaller diameter copper distribution cables. Consideration should also be given to the provision of high-speed data circuits for residential customers, particularly for Internet access.

Basic Switching Requirements

Conceptually, consider that a switch has inlets and outlets. Inlets serve incoming calls outlets serve outgoing calls. A call from a calling subscriber enters an exchange through an inlet. It connects to a called subscriber through an outlet. There are three basic switching requirements Let's differentiate local and tandem transit exchanges. A local exchange connects lines (subscriber loops) to other lines or to trunks. A tandem transit exchange switches trunks. Local exchanges concentrate and expand. Tandem and transit exchanges do not.

Dialservice Observation

Traditionally, service observation has been done manually, requiring the presence of an observer. Service observation positions have some forms of automation, such as automatic recording of a calling number and or the mark sensing or keypunching to be employed for computer-processing input. Tape recorders may be placed at exchanges to automatically record calls on selected lines. The tapes are then periodically sent to the service observation desk. Tapes usually have a time hack to record the time and the duration of calls. A service observation desk usually serves many exchanges or an entire local area. Tandem exchanges are good candidates because they concentrate the service function. The results of service observation are intended to represent average service thus care should be taken to ensure that subscribers selected represent the average customer. The following is one list of data to be collected per line observed Ineffective calls due to calling subscriber incomplete call,...

Concentration and Expansion

Ideally, there should be one trunk available for every subscriber line (loop). Then there never would be a chance of blockage. Thus, whenever a subscriber wished to connect to a distant subscriber, there would be a trunk facility available for that call. Our knowledge of telephone calling habits of subscribers tells us that during the busy hour, on the order of 30 of subscriber lines will be required to connect to trunks for business customers and some 10 for residential customers. Of course, these values are rough estimates. We'd have to apply the appropriate traffic formula based on a grade of service, as described in Section 4.2.1, for refined estimates. Based on these arguments, a local exchange serving residential customers might have 10,000 lines, and only 1000 trunks would be required. This is concentration. Consider that those 1000 incoming trunks to that exchange must expand out to 10,000 subscribers. This is expansion. It provides all subscribers...

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