Info

One digit is added to ensure that the timing content of the transmitted pattern is maintained Figure 8.9. Eight-level coding of the North American DS1 PCM system. Note that there are actually only 255 quantizing steps because steps 0 and 1 use the same bit sequence, thus avoiding a code sequence with no transitions (i.e., all 0s). One digit is added to ensure that the timing content of the transmitted pattern is maintained Figure 8.9. Eight-level coding of the North American DS1 PCM system....

Introduction

CCITT Signaling System No. 7 (SS No. 7) was developed to meet the advanced signaling requirements of the all-digital network based on the 64 kbits s channel. It operates in a quite different manner than the signaling discussed in Chapter 4. Nevertheless, it must provide supervision of circuits, address signaling, carry call progress signals, and alerting notification to be eventually passed to the called subscriber. These requirements are no different from those of Chapter 4. The difference is...

Quality of a Telephone Speech Connection

Loudness rating is the principal parameter for measuring the quality of a speech connection. CCITT ITU-T Recs. P.11, P.76, P.78, and P.79 provide information on subjective and objective methods for the determination of loudness ratings (LRs). The currently recommended values of loudness loss in terms of loudness ratings are given in ITU-T Recs. G.111 and G.121 25, 26 . In simple terms, loudness rating is a measure of speech level (volume). The term replaces reference...

Catv As A Basic Transport Medium For The Last Mile

For most developed countries there will be an existing cable television system at most population centers. In most instances we can depend on the fact that coaxial cable with drops will be in place. The existing system will also probably be an HFC (hybrid fiber coax) system. Whether the existing system has been optimized for broadband** delivery and transmission may be another matter entirely. The architecture and layout of the serving coaxial cable portion of the CATV system is usually the...

Contents

1 Definition and Concept 1 1.1 Telecommunication Networks 1 2 The Simple Telephone Connection 2 4 Telephone Networks Introductory Terminology 5 5 Essentials of Traffic Engineering 6 5.1 Introduction and Terminology 6 5.2 Measurement of Telephone Traffic 9 5.3 Blockage, Lost Calls, and Grade of Service 10 5.5 Handling of Lost Calls 13 5.6 Infinite and Finite Sources 13 5.7 Probability-Distribution Curves 14 5.8 Smooth, Rough, and Random Traffic 15 6 Erlang and Poisson Traffic Formulas 16 6.1...

Connectionoriented and connectionless 654659

Grade of, 11 observing, 35 provided by SCCP, 706 serving areas, 55, 57, 59 boundaries of, 60f exchange, 60 shapes of, 56 serving circuits, 28 required, 26 serving exchanges, 43 serving node, 442 serving switch, 43 serving time, 26 SES (severely errored second), 347 SESR (severely errored second ratio), 348, 349 session connection, 433 session layer, 433 session protocol definition of, 433 messages via, 433 set successor frame, 529 setup of logical signaling connection, 706 of radio channel...

Where Necessary Sfd Start Frame Delimiter

The data (LLC data) field contains a sequence of octets that is fully transparent in that any arbitrary sequence of octet values may appear in the data field up to the maximum number specified by the implementation of this standard that is used. The maximum size of the data field supplied by the LLC is determined by the maximum frame size and address size parameters of a particular implementation. The frame check sequence (FCS) field contains four octets (32...

Pcm Line Codes

The original design of a PCM system was for application to a wire-pair cable medium. The line code is bipolar in this case as shown in Figure 8.1. The marks or binary 1s have only a 50 duty cycle. There are several advantages to this mode of transmission No dc return is required thus transformer coupling can be used on the line. The power spectrum of the transmitted signal is centered at a frequency equivalent to half the bit rate. It will be noted in bipolar transmission that the 0s are coded...

Kp2

3 Pulsing of digits Is at the rate of about seven digits per second with an interdigital period of 68 7 ms. For intercontinental dialing for CCITT No. 5 code compatibility, the R-1 rate is increased to 10 digits per second. The KP pulse duration is 100 ms 3, 11 . Source Ref. 13. 3 Pulsing of digits Is at the rate of about seven digits per second with an interdigital period of 68 7 ms. For intercontinental dialing for CCITT No. 5 code compatibility, the R-1 rate is increased to 10 digits per...

Routing Scheme

A routing scheme defines how a set of routes is made available for calls between a pair of nodes. There are fixed routing schemes and dynamic routing schemes. Of course, for a fixed routing scheme, the routing pattern is always the same. For a dynamic scheme the set of routes in the routing pattern varies. Figure 6.9. A simplified network with circuit groups connecting pairs of nodes with one-way and both-way (two-way) working. Figure 6.9. A simplified network with circuit groups connecting...

References

Breen, Signaling Systems for Control of Telephone Switching, STJ, 39 (November 1960). 2. BOC Notes on the LEC Networks 1990, BSR-TSV-002275, Issue 1, Bellcore, Pis-cataway, NJ, March, 1991. 3. Signaling, from Telecommunication Planning Documents, ITT Laboratories (Spain), Madrid, November 1974. 4. National Networks for the Automatic Service, CCITT-ITU, Geneva, 1964. 5. M. Den Hertog, Inter-register Multifrequency Signaling for Telephone Switching in Europe, Electr. Commun.,...

Radio Frequency Bands for Pagers

All three ITU regions have some or all of the following frequency bands allocated to mobile services 26.1-50 MHz 68-88 MHz 146-174 MHz 450-470 MHz 806-960 MHz TABLE 18.5 Propagation Loss Suffered by Signals in Penetrating Buildings Frequency 150 MH 250 MHz 400 MHz 800 MHz Building penetration lossa 22 dB 18 dB 18 dB 17 dBb aThe loss is given as the ratio between the median value of the field strengths measured over the lower floors of buildings and the median value of the field strengths...

Mtie

Link status signal unit lowest two-way channel low-voltage differential signaling managed (or management) application function(s) a media gateway standard, also called ITU-T Rec. H.248 micro-electromechanical systems medium earth orbit medium frequency (signaling) medium frequency (RF) management information base message identification management information tree multilink procedures modified long route design microwave multipoint distribution system managed object MTP2 peer-to-peer adaptation...

Tandem Routing

The local-area trunking scheme evolutionally has been the mesh connection of exchanges, and in many areas of the world it remains full mesh. We said initially that mesh connection is desirable and viable for heavy traffic flows. As traffic flows reduce, going from one situation to another, the use of tandem routing in the local area becomes an interesting, economical alternative. Furthermore, it can be shown that a local trunk network can be optimized, under certain circumstances, with a mix of...

Crosstalk

Crosstalk is a major impairment in PCM wire-pair systems, particularly when go and return channels are carried in the same cable sheath. The major offender of single-cable operation is near-end crosstalk (NEXT). When the two directions of transmission are carried in separate cables or use shielded pairs in a common cable, far-end crosstalk (FEXT) becomes dominant. One characteristic has been found to be a major contributor to poor crosstalk coupling loss. This is the capacitance imbalance...

Biv

E1 multiframe, CRC-4 structure. Notes E CRC-4 error indication bits Sa4 to Sa8 spare bits. These bits may be used for a network management (maintenance) link. C1 to C4 CRC-4 bits. A remote alarm indication. From Table 4b G.704, page 81, CCITT Rec. G.704, 1988 10 . Figure 21.2. E1 multiframe, CRC-4 structure. Notes E CRC-4 error indication bits Sa4 to Sa8 spare bits. These bits may be used for a network management (maintenance) link. C1 to C4 CRC-4 bits. A remote alarm indication....

The Asynchronous Transfer Mode Atm And Broadband Isdn

Frame relay (Chapter 15) was the beginning of the march toward an optimized* format for multimedia transmission (voice, data, video, facsimile). There were new concepts in frame relay. There was a trend toward simplicity where the header was notably shortened. The header was pure overhead, so it was cut back as much as practically possible. The header also implied processing. By reducing the processing, delivery time could be speeded up. In the effort to speed up delivery, operation was...

Lkjihgfedcba

Initial address message format. From Figure 3 Q.723, page 23, CCITT Rec. Q.723, 1988 21 . Figure 17.16. Initial address message format. From Figure 3 Q.723, page 23, CCITT Rec. Q.723, 1988 21 . Unsuccessful backward setup messages 0101 H1 contains a signal code or identifies the format of more complex messages. For instance, there are four types of address message identified by H0 0001, and H1 identifies the type of message, such as Address Message Type H0 H1 Initial address...

Optical Switching

The optical switch is one of the most important fiber-optic components that seamlessly maintains network survivability and is a flexible platform for signal routing. Today's switching in telecommunication systems is done electronically (in the electrical domain) however, as modern photonic networks evolve, routing of fiber-optic signals will be carried out completely in the optical realm. The most common form of optical switches found off-the-shelf today are either electro-optical or...

Introduction to Optical Fiber as a Transmission Medium

Optical fiber consists of a core and a cladding as shown in Figure 7.24. At present the most efficient core material is silica SiO2. The practical propagation of light through an optical fiber may best be explained using ray theory and Snell's law. Simply stated, we can say that when light passes from a medium of higher refractive index (n1) into a medium of lower refractive index (n2), the refractive ray is bent away from the normal. For instance, a ray traveling in water and passing into an...

Dimensioning Of Trunks

A primary effort for the system engineer in the design of the local trunk network is the dimensioning of the trunks of that network. Here we simply wish to establish the economic optimum number of trunk circuits between exchanges X and Y. If we are given the traffic (in erlangs) between the two exchanges and the grade of service, we can assign the number of trunk circuits between X and Y. As discussed in Chapter 1, it is assumed that all traffic values are BH values. Once given this input...

Review Questions

What transmission medium should be considered as a principal candidate for a digital waveform that would carry more than 10,000 full-duplex telephone circuits at the end of the forecast period 2. What are the advantages of using the RF bands from 2 GHz to 10 GHz for trunk telephony Name at least two. 3. Frequencies above 10 GHz have an additional major impairment that must be taken into account in radiolink design. What is the cause of this impairment 4. Discuss the problem of delay in speech...

Compelled Signaling

In many of the signaling systems discussed thus far, signal element duration is an important parameter. For instance, in a call setup an initiating exchange sends a 100-ms seizure signal. Once this signal is received at the distant end, the distant exchange sends a proceed to send signal back to the originating exchange in the case of the R-1 system, this signal is 140 ms or more in duration. Then, on receipt of proceed to send the initiating exchange spills all digits forward. In the case of...

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...

K

If the factor K is greater than 1, the ray beam is bent toward the earth and the radio horizon is greater than the optical horizon. If K is less than 1, the radio horizon is less than the optical horizon. For general system planning purposes, K may be used. However, for specific path engineering, K must be selected with care. The value of h or earth curvature corrected for K from equation 7.3 must be added to obstacle height in the path-profile exercise for each obstacle. Still another factor...

QoS Parameter Descriptions

In addition to the normal delay through network elements and lines, extra delay is added to an ATM network at an ATM switch. The cause of the delay at this point is the statistical asynchronous multiplexing. Using this method, two cells can be directed toward the same output of an ATM switch or cross-connect resulting in output contention. The result is that one cell or more is held in a buffer until the next available opportunity to continue transmission. We can see...

Stream control transport protocol SCTP

729-732.See also SCTP entries streaming-mode service, ATM, 653 Strowger switch, 73 STS-1 overhead, 300f STS-1s, linking, 299 STS-1 signal, 294 STS-1 synchronous payload envelope (SPE), 295f STS envelope capacity, 303 STS-Nc SPE, 299f STS-N frame, 296f STS payload pointer (H1, H2) coding, 303f STS POH, 299 STS switching, 326 stuffing, 285, 383 to meet line bit rate requirements, 402 stuffing and justification, 285, 285f stuffing bits, 285, 286, 298 stuff position, 288 subdivided cells, 740...

Basic Signal Unit Format

Signaling and other information originating from a user part is transferred over the signaling link by means of signal units. There are three types of signal units used in SS No. 7 2. Link status signal unit (LSSU) These units are differentiated by means of the length indicator. MSUs are retransmitted in case of error LSSUs and FISUs are not. The MSU carries signaling information the LSSU provides link status information, and the FISU is used during the link idle state they fill in. The...

Thermal Noise

As in any electrical communication system, thermal noise, impulse noise, and crosstalk affect system design. Because of the nature of a digital system, these impairments need only be considered on a per-repeater-section basis because noise does not accumulate due to the regenerative process carried out at repeaters and nodes. Bit errors do accumulate, and this impairment family is one of several that create these errors. One way to limit error accumulation is to specify a stringent BER for each...

Frequency Division Multiple Access FDMA

With FDMA, our band of frequencies is divided into segments and each segment is available for one user access at a time. Half of contiguous segments are assigned cell site outbound to mobile users and the other half inbound. A guard band is usually provided between outbound and inbound contiguous channels. This concept is shown in Figure 18.17. Because of our concern to optimize the number of users per unit bandwidth, the key question is the actual width of one user segment. The North American...

Plcp

Optical bidirectional line-switched rings optical carrier optical cross-connect system(s) optical-electrical-optical Optical Internetworking Forum overall loudness rating operation and maintenance operation and maintenance centers optical network unit originating point code outside plant module optical remote module open systems interconnection operation systems function optical signal-to-noise ratio open shortest path first operations support subsystem organizationally unique identifier...

Moffett

(NOTE THIS MAP DOES NOT SHOW ARPA'S EXPERIMENTAL SATELLITE CONNECTIONS)' NAMES SHOWN ARE IMP NAMES, NOT (NECESSARILY) HOST NAMES Figure 11.1. The ARPANET geographic map. An example of a very large data network (ca. 1989). Figure 11.2. Elemental point-to-point data connectivity. The DTE, described in Chapter 10, consists of the DPTE and I O combined. The DCE is the modem. DPTE, data processing terminal equipment I O, input output device. Figure 11.2. Elemental point-to-point data connectivity....

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...

Advantages And Issues Of Pcm Switching When Compared To Its Analog Counterpart

There are both economic and technical advantages to digital switching in this context we refer to PCM switching (or course, most of these same arguments hold for delta CVSD switching as well). The economic advantages of time-division PCM switching include the following There are notably fewer equivalent cross-points for a given number of lines and trunks than in a space-division switch. A PCM switch is of considerably smaller size. It has more common circuitry (i.e., common modules). It is...

Evolutionary Stored Program Control and Distributed Processing

The presently installed switching plant represents an extremely large investment yet to be fully amortized. The small amount of plant that remains consists of crossbar equipment that is quickly being replaced by digital switches. It was estimated that in 1973, SPC served less than 10 of Bell System subscribers (North America). SPC was just one small step behind a full digital switch. To accelerate SPC implementation, it was common practice to adapt existing plant by...

Concentrators Outside Plant Modules Remote Switching And Satellites

Concentrators or line concentrators consolidate subscriber loops, are remotely operated and are a part of or the complete concentration (and expansion) portion of a local switch placed at a remote location. They consolidate subscriber lines but do not switch among them. A typical crossbar type of concentrator is illustrated in Figure 3.16, where 100 subscriber loops are consolidated to 20 trunks plus 2 trunks for control from the nearby mother exchange. Concentrators are used in sparsely...

Digital Data Waveforms

Digital symbols may be represented in many different ways by electrical signals to facilitate data transmission. All these methods for representing (or coding) digital symbols assign electrical parameter values to the digital symbols. In binary coding, of course, these digital symbols are restricted to two states, space (0) and mark (1). The electrical parameters used to code digital signals are levels (or amplitudes), transitions between different levels, phases (normally 0 and 180 for binary...

ATM adaptation layer AAL 648654

Also AAL entries over AAL1 AAL2, 487 header structure for, 637f, 642 introduction to, 631-633 routing and switching via, 659-660 service classes with, 658t service quality review of, 663-664 switch cross-connect in, 654 switching in, 654 ATM and user-network interfaces (ATM UNI) configuration equipment implementing ILMI and, 906f management information base for, 904 reference model for, 634f ATM cell headers, 646 SDH-based UNI, 674f 622.080 Mbps frame structure for SDH-based UNI, 675f into DS3...

How LAN Protocols Relate to OSI

LAN protocols utilize only OSI layers 1 and 2, the physical and data-link layers, respectively. The data-link layer is split into two sublayers medium access control (MAC) and logical link control. These relationships are shown in Figure 13.3. Stallings 3 presents an interesting and rational argument on the reasoning for limiting the layering to the first two OSI layers. There is no question that the functions of OSI layers 1 and 2 must be incorporated in a LAN architecture. We now ask, Why not...

Running a Path Site Survey

This can turn out to be the most important step in the design of an LOS microwave link (or hop). We have found through experience that mountains move (i.e., map error), buildings grow, grain elevators appear where none were before, east of Madrid a whole high-rise community goes up, and so forth. Another point from experience If someone says line-of-sight conditions exist on a certain path, don't believe it Line of sight must be precisely defined. We reiterate that for each obstacle in the LOS...

Classification of Fading

We consider three types of channels to place bounds on radio system performance. These are 5.2.1 The Gaussian Channel. The Gaussian channel can be considered the ideal channel, and it is only impaired by additive white Gaussian noise (AWGN) developed internally by the receiver. We hope to achieve a BER typical of a Gaussian channel when we have done everything we can to mitigate fading and its results. These measures we take could be diversity, equalization, FEC coding with interleaving, and so...

Availability

Availability was discussed in Chapter 1, Section 5.4. We now consider availability to introduce grading. At a switching array, availability describes the number of outlets that a free inlet is able to reach and test for a busy condition. (A) Full Availability k> N IB) limited Availability k < .V Figure 3.8. Full and limited availability. i number of inlets per switching matrix (grading group), m number of switching matrices (grading groups) (4, in A and B), N number of outlets (three in A...

Sonet

SONET's higher-level digital format was originally intended for transmission over optical fiber facilities. It can, however, be accommodated on any transmission medium that meets the bandwidth requirements. Figure 8.19 is a functional diagram depicting SONET section, line, and path for the purpose of definition. Figure 8.19. SONET section, line and path definitions 14,16 . Figure 8.19. SONET section, line and path definitions 14,16 . 13.2.1 SONET Rates and Formats. SONET was designed to have a...

Access Techniques

Inbound refers to traffic from VSAT(s) to hub, and outbound refers to traffic from hub to VSAT(s). The outbound link is commonly a time-division multiplex (TDM) serial bit stream, often 56 kbps, and some high-capacity systems reach 1.544 or 2.048 Mbits s. The inbound links can take on any one of a number of flavors, typically 9600 bits s. More frequently VSAT systems support interactive data transactions, which are very short in duration. Thus, we can expect bursty...

The Simple Telephone Connection

The common telephone as we know it today is a device connected to the outside world by a pair of wires. It consists of a handset and its cradle with a signaling device, consisting of either a dial or push buttons. The handset is made up of two electroacoustic transducers, the earpiece or receiver and the mouthpiece or transmitter. There is also a sidetone circuit that allows some of the transmitted energy to be fed back to the receiver. The transmitter or mouthpiece converts acoustic energy...

Ss No 7 Relationship To

CCITT SS No. 7 relates to OSI (Chapter 11, Section 6.2.2) up to a certain point. One group believes that SS No. 7 should be fully compatible with the seven layers of OSI. However, the CCITT working groups responsible for the SS No. 7 concept and design were concerned with delay, whether for the data or telephone user of the digital PSN or ISDN. Recall from Chapter 4 that postdial delay is one of the principal measures of performance of a signaling system. To minimize delay, the seven layers of...

Erlang And Poisson Traffic Formulas

When dimensioning a route, we want to find the number of circuits that serve the route. There are several formulas at our disposal to determine that number of circuits based on the BH traffic load. In Section 5.3 four factors were discussed that will help us to determine which traffic formula to use given a particular set of circumstances. These factors primarily dealt with (1) call arrivals and holdingtime distribution, (2) number of traffic sources, (3) availability, and (4) handling of lost...

Modulation Demodulation Schemes

A modem modulates and demodulates a carrier signal with digital data signals. The types of modulation used by present-day modems may be one or a combination of the following Amplitude modulation, double sideband (DSB). Amplitude modulation, vestigial sideband (VSB). Frequency shift modulation, commonly called frequency shift keying (FSK). Phase shift modulation, commonly called phase shift keying (PSK). 9.2.1 Amplitude Modulation Double Sideband. With the double-sideband (DSB) modulation...

Digital Loop Carrier

Digital loop carrier (DLC) has evolved from subscriber carrier, which has a long history in the telephone plant. Subscriber carrier was one way we could make two loops out of one, then three or four or more, by stacking FDM carriers one on top of the other where each carrier provided a usable bandwidth of at least 4 kHz 7 . In the 1980s, next-generation digital loop carriers (NGDLC) began to appear. They solved two problems. First, new services could be offered the customer through NGDLC....

Low Frequency AC Signaling Systems

An ac signaling system operating below the limits of the conventional voice channel (i.e., < 300 Hz) are termed low frequency. Low-frequency signaling systems are one-frequency systems, typically 50 Hz, 80 Hz, 135 Hz, or 200 Hz. It is impossible to operate such systems over carrier-derived channels (see Chapter 5) because of the excessive distortion and band limitation introduced. Thus low-frequency signaling is limited to metallic-pair transmission systems. Even on these systems, cumulative...

Space TimeSpace Switch

A space-time-space (STS) switch reverses the architecture of a TST switch. The STS switch consists of a space cross-point matrix at the input followed by an array of time-slot interchangers whose ports feed another cross-point matrix at the output. Such a switch is shown in Figure 9.6. Consider this operational example with an STS. Suppose that an incoming time slot 5 on port No. 1 must be connected to an output slot 12 at outgoing port 4. This can be accomplished by time-slot interchanger No....

Voicefrequency Repeaters

A voice frequency (VF) repeater is an audio amplifier used on a subscriber loop to extend it or on a VF trunk to meet certain loss or gain requirements. There are two types of VF repeaters used in the industry a four-wire repeater or a two-wire negative impedance repeater. Their application as we describe it is for two-wire operation. For the four-wire repeater a hybrid is used on the input and another on the output to convert two-wire operation to four-wire operation and back again. An example...

Shape Of A Serving Area

The shape of a serving area has considerable effect on optimum exchange size. If a serving area has sharply angular contours, the exchange size may have to be reduced to avoid excessively long loops (e.g., revert to the use of more exchanges in a given local geographical area of coverage). There is an optimum trade-off between exchange size, and we mean here the economies of large exchanges (centralization) and the high cost of long subscriber loops. An equation that can assist in determining...

Multiple Access of a Satellite

Multiple access is defined as the ability of a number of earth stations to interconnect their respective communication links through a common satellite. Satellite access is classified (1) by assignment, whether quasi-permanent or temporary, namely, (a) preassigned multiple access or (b) demand-assigned multiple access (DAMA), and (2) according to whether the assignment is in the frequency domain or the time domain, namely, (a) frequency-division multiple access (FDMA) or (b) time-division...

Digital Extension to the Subscriber

The argument in this section from the third edition of this book has been bypassed, overrun. Much of these bypassing technologies are described in Chapter 19 on last mile connectivity. The great majority of customers, at least in North America, have a CATV cable running near their residence or business. Besides entertainment TV, the CATV cable system can and will provide digital telephony and megabit downstream internet. LMDS (see Chapter 19) and some satellite systems (direct broadcast...

Bip8

Source Table B.1 G.828, page 12, ITU-T Rec. G.828, March 2000 22 . Source Table B.1 G.828, page 12, ITU-T Rec. G.828, March 2000 22 . THE DIGITAL NETWORK 353 TABLE 9.7A Maximum Permissible Jitter at 2.048-Mbits s Traffic Interfaces Measurement Bandwidth, -3-dB Frequencies (Hz) Peak-to-Peak Amplitude (Ulpp) (Note 3)

Switching in the Telephone Network

A network of telephones consists of pathways connecting switching nodes so that each telephone in the network can connect with any other telephone for which the network provides service. Today there are hundreds of millions of telephones in the world, and nearly each and every one can communicate with any other one. Chapter 1 discussed the two basic technologies in the engineering of a telephone network, namely, transmission and switching. Transmission allows any two subscribers in the network...

TST Compared to STS

Both TST and STS switches can be designed with identical call-carrying capacities and blocking probabilities. It can be shown that a direct one-to-one mapping exists between time-division and space-division networks 2 . The architecture of TST switching is more complex than STS switching with space concentration. The TST switch becomes more cost-effective because time expansion can be achieved at less cost than space expansion. Such expansion is required as link utilization increases because...

Attenuation Distortion

A signal transmitted over a voice channel suffers various forms of distortion. That is, the output signal from the channel is distorted in some manner such that it is not an exact replica of the input. One form of distortion is called attenuation distortion and is the result of imperfect amplitude-frequency response. Attenuation distortion can be avoided if all frequencies within the passband are subjected to exactly the same loss (or gain). Whatever the transmission medium, however, some...

TIAEIA644 Low Voltage Differential Signaling LVDS

LVDS has been designed for point-to-point data circuits where the signaling rates exceed 100 Mbits s. LVDS power supplies are available at 5 V, 3.3 V, and 2.5 V. Signaling is carried out with voltage swings to about 300 mV. Noise margins and noise immunity are increased even further by the use of differential data transmission. Such differential signals are immune to common mode noise, which is the primary source of system noise. LVDS changes signal voltage levels without a fast slew rate. The...

Traditional Breakout By Tasks

There are five tasks traditionally involved with network management This is a facility that provides information on the status of the network and subnetworks. The information on the status should not only display faults (meaning failures) and their location, but should also provide information on deteriorated performance. One cause of deteriorated performance is congestion. Thus, ideally, we would also like to isolate the cause of the problem. Fault management should include the means to bypass...

InBand Signaling

In-band signaling refers to signaling systems using an audio tone, or tones inside the conventional voice channel, to convey signaling information. In-band signaling is broken down into three categories (1) one frequency (SF or single frequency), (2) two frequency (2VF), and (3) multifrequency (MF). As the term implies, in-band signaling is where signaling is carried out directly in the voice channel. As the reader is aware, the conventional voice channel as defined by the CCITT occupies the...

Digital Network Synchronization

When a PCM bit stream is transmitted over a telecommunication link, there must be synchronization at three different levels bit, time slot, and frame. Bit synchronization refers to the need for the transmitter (coder) and receiver (decoder) to operate at the same bit rate. It also refers to the requirement that the receiver decision point be exactly at the mid-position of the incoming bit. Bit synchronization assures that the bits will not be misread by the...

Stuffing and Justification

Stuffing ( justification) is common to all higher-level multiplexers that we describe below. Consider the DS2 higher-level multiplex. It derives from an M12 multiplexer, taking inputs from four 24-channel channel banks. The clocks in these channel banks are free running. The transmission rate output of each channel bank is nominally 1,544,000 bits s. However, there is a tolerance of 50 ppm ( 77 bits s). Suppose all four DS1 inputs were operating on the high side of the tolerance or at 1,544,077...

Causes of Echo and Singing

Echo and singing can generally be attributed to the mismatch between the balancing network of the hybrid and its two-wire connection associated with the subscriber loop. In older, more conventional networks, two-wire operation was carried to the toll-connecting switch or a tandem exchange just preceding this switch. In this type of network there was at least one two-wire switch between the subscriber and the hybrid. A typical model of the two-wire four-wire conversion points is shown in Figure...

The Signaling Link Level

This section deals with the transfer of signaling messages over one signaling link directly connecting two signaling points. Signaling messages delivered by superior hierarchical levels are transferred over the signaling link in variable-length signal units. The signal units include transfer control information for proper operation of the signaling link in addition to the signaling information. The signaling link (level 2) functions include (a) Signaling unit delimitation (f) Signal link error...

Introduction to Transmission Loss Engineering

One major aspect of transmission system design for a telephone network is to establish a transmission-loss plan. Such a plan, when implemented, is formulated to accomplish three goals 1. Control singing (stability). 2. Keep echo levels within limits tolerable to the subscriber. 3. Provide an acceptable overall loudness rating value to the subscriber. Transmission loss engineering of a telephone network is based on the following three guidelines 1. A certain minimum loss must be maintained in...

Definitions Degeneration Availability And Grading 81 Degeneration

Degeneration can be expressed by the following ratio Degeneration is a measure of the extent to which the traffic on a given link varies from pure random traffic. For pure random traffic, degeneration (the preceding ratio) equals 1. For overflow traffic, the variance is equal to or, in the majority of cases, greater than the mean. The more degenerate the traffic, the heavier the demand during peak periods and the greater the number of transmission facilities required.

Subscriber Loop Design Techniques

Consider the following drawing of a simplified subscriber loop The distance D, the loop length, is a critical parameter. The greater the value of D, the greater the attenuation that the loop suffers, and signal level drops as a result. Likewise, there is a limit to D due to dc resistance, so signaling the local switch can be affected. When we lift the telephone off hook, there f Note The terms on hook and off hook derive from old-fashioned telephones. This type of telephone...

Critical Parameters

The effect of the various telephone-circuit impairments on the capability of a circuit to transmit data is a most important consideration. These impairments are In Chapter 5 there was a detailed discussion of these parameters. The following is a rule of thumb for phase distortion (group delay) The group delay distortion (envelope delay distortion) should be kept under the period of the bit (or baud) of the bit stream of interest. For the analog voice channel, the frequency band of interest is...

Regenerative Repeaters

As the reader is probably aware, pulses passing down a digital transmission line suffer attenuation and are badly distorted by the frequency characteristic of the line. A regenerative repeater amplifies and reconstructs such a badly distorted digital signal and develops a nearly perfect replica of the original at its output. Regenerative repeaters are an essential key to digital transmission in that we could say that the noise stops at the repeater. Figure 8.14 is a simplified block diagram of...

Advantages and Disadvantages of a Low Earth Orbit

The low earth orbit (LEO) offers a number of advantages over the geostationary orbit, and at least one serious disadvantage. Delay. One-way delay to a GEO satellite is budgeted at 125 ms one-way up and down is double this value of 250 ms. Round-trip delay is about 0.5 s. Delay to a typical LEO is 2.67 ms and round-trip delay is 4 x 2.67 ms or about 10.66 ms. Calls to from mobile users of such systems may be relayed still again by conventional satellite services. Data services do not have to be...

Broadband Transmission Considerations

Broadband transmission permits multiple users to access the medium without collision. Broadband means that we take advantage of the medium's wide bandwidth. This wide bandwidth is broken down into smaller bandwidth segments in an analogous fashion to FDM. Each of these segments is assigned to a family of users. The statement regarding collision is correct if there are no more than two accesses per frequency segment connected on a point-to-point basis, where one access receives while the other...

The Effects Of Numbering On Signaling

Numbering, the assignment and use of telephone numbers, affects signaling as well as switching. It is the number or the translated number, as we found out in Chapter 3, that routes the call. There is uniform numbering and nonuniform numbering. How does each affect signaling Uniform numbering can simplify a signaling system. Most uniform systems in the nontoll or local-area case are based on seven digits, although some are based on six. The last four digits identify the subscriber. The first...

Ed Fs

DA Destination Address (4 or 12 symbols) SA Source Address (4 or 12 symbols) Rl Routing information 0-15)x4 symbols) INFO Information (> 0 symbol pairs) FCS Frame Check Sequence (8 symbols) EFS End of Frame Sequence ED Ending Delimiter (1 symbol) FS Frame Status 3 symbols) Figure 13.22. The FDDI frame format.

Data Interface The Physical Layer

When we wish to transmit data over a conventional analog network, the electrical representation of the data signal is essentially direct current. As such it is incompatible with that network that accepts information channels in the band 300 to 3400 Hz.* A data modem is a device that brings about this compatibility. It translates the electrical data signal into a modulated frequency tone in the range of 300 to 3400 Hz, often 1800 Hz. Also, more often than not, the digital network (described in...

Design Of Local Area Analog Trunks Junctions

Exchanges in a common local area are interconnected by trunks. In countries where the telecommunication infrastructure is more developed, these trunks are DESIGN OF LOCAL AREA ANALOG TRUNKS (JUNCTIONS) 63 liable to be digital based on E1 or T1 techniques which we will discuss in Chapter 8. Where the infrastructure of telecommunications is less developed, these trunks and their connected exchanges are analog. In either case there will be a relatively small number of these trunks compared to the...

In data transmission 372378 nature of 373374

On PCM repeatered line, 280 error status, SNMP, 892 ES (errored seconds), 347, 349. See also errored second (ES) ESF (extended superframe), 877, 880 ESR (errored second ratio), 263, 348, 349 Ethernet, 505 PDU size and, 453 Ethernet bus, competitors for, 554 Ethernet LAN, 10 Mbps, 505 Ethernet RMON MIB, 894 ethertype assignments, 451t European E1, 320 European E1 digital hierarchy, 288-290 European E1 framing, 281 even odd parity, 374 event-dependent routing, 171 example of, 174-175 events, ATM,...

Metallic Trunk Signaling 101 Basic Loop Signaling

Many trunks serving the local area are metallic-pair trunks, although in more developed nations they may carry a digital format such as T1 or E1. In other situations they are DC loops much like the subscriber loop. A few of these trunks still use dial pulses for address signaling as well as some sort of supervisory signaling. Of course these loop-signaling circuits provide two signaling states one when the circuit is opened and the other when the circuit is closed. A third signaling state is...

Rf

Public land mobile network physical layer signaling peripheral module physical medium attachment pseudo-noise plain old telephone service pulse position modulation parts per million public switched telecommunications network public telecommunication operator(s) quadrature amplitude modulation quality of service quadrature phase-shift keying remote authentication dial-in user service residual excited linear predictive (coder) radiofrequency

Basic Functions of Stored Program Control

There are four basic functional elements of an SPC switching system (1) switching matrix, (2) call-store (memory), (3) program store (memory), and (4) central processor. These four basic elements are shown in a functional block diagram in Figure 3.13. * This important concept is the basis for the argument set forth in Chapter 9 regarding the rationale for digital switching. Figure 3.13. A simplified functional block diagram of an SPC exchange. Figure 3.13. A simplified functional block diagram...

Cell Delineation And Scrambling

5.1 Delineation and Scrambling Objectives Cell delineation allows identification of the cell boundaries. The cell header error control (HEC) field achieves cell delineation. Keep in mind that the ATM signal must be self-supporting in that it has to be transparently transported on every network interface without any constraints from the transmission systems used. Scrambling is used to improve security and robustness of the HEC cell delineation mechanism discussed below. In addition, it helps the...

Terrestrial Interface

NOTE THIS FUNCTIONAL BLOCK DIAGRAM IS INTENOED FOR ILLUSTRATION PURPOSES ONLY, ANO IS NOT INTENDED TO PORTRAY ANY PARTICULAR PHYSICAL EQUIPMENT ARRANGEMENT OR THE TYPE OF TERRESTRIAL INTERFACE. FOR EXAMPLE, THE BUFFER COULD 8E PART OF THE CHANNEL UNIT. THE MULT -TIPIEX EQUIPMENT COULD ALSO BE ON THE TERRESTRIAL SIOE OF INTERFACES AND d. Figure 7.18. Illustration of atypical INTELSAT multidestinational QPSK IDR application. From Figure 20, page 66, INTELSAT IESS-308 (Rev. 10), 10 . Figure 7.19....

Diversity and Hot Standby Operation

Diversity reception means the simultaneous reception of the same radio signal over two or more paths. Each path is handled by a separate receiver chain and then combined by predetection or postdetection combiners in the radio equipment so that effects of fading are mitigated. The separate diversity paths can be based on space, frequency, and or time diversity. The simplest form of diversity is space diversity. Such a configuration is shown in Figure 7.13. The two diversity paths in space...

Summary of Limiting Conditions Transmission and Signaling

We should be aware that the physical size of an exchange serving area is limited by factors of economy involving signaling and transmission. Signaling limitations are a function of the type of exchange and the diameter of the subscriber pairs and their conductivity, whereas transmission is influenced by pair characteristics. Both limiting factors can be extended, but that extension costs money, particularly when there may be many thousands of pairs involved. The decision boils down to the...

Phase Distortion

A voice channel may be regarded as a band-pass filter. A signal takes a finite time to pass through a telecommunication network. This time is a function of the velocity of propagation, which varies with the media involved. The velocity of propagation also tends to vary with frequency because of the electrical characteristics associated with the network. Considering the voice channel, therefore, the velocity of propagation tends to increase toward band center and decrease toward band edge. This...

Higher Level Multiplex Structures Internal to a Digital Switch

We pictured a simple time-slot interchanger switch with 24 8-bit time slots to satisfy DS1 requirements. It would meet the needs of a population of 24 subscribers without blocking. There is no reason why we couldn't build a TSI with greater capacity. Suppose that instead of the DS1 rate, we built the TSI with a DS3 rate. The basic TSI then could handle 672 subscribers (i.e., 672 time slots). If we built a concentrator in front of it for 4 1 concentration, then it could handle 4 x 672 or 2688...

Pstn

Graphic illustration of the functional operation of an MSS connectivity. mobile service providers, the mobile platform terminals can be fairly large and sophisticated depending largely on the type of service offered. With a mobile platform the antenna subsystem is the principal limiting factor to performance and bit rate supported. Typical antenna gains used in MSS vary between 0 dBi (a hand-held terminal, for example) to +21 dBi (85-cm reflector antenna). Receiver system...

Fcs

Frame format for multiprotocol over a frame relay frame. Q.922 address two-octet address field containing the 10-bit DLCI field. Under a certain situation, the address field may be optionally 3 or 4 octets long. Control Q.922 control field. The UI value 0 x 03 is used unless negotiated otherwise. The use of XID (0 x AF or 0 x BF) is permitted. Pad used to align the remainder of the frame on a two-octet boundary. There may be 0 or 1 pad octet within the pad field. The value is...

Introductory Switching Concepts

All telephone switches have, as a minimum, three functional elements concentration, distribution, and expansion. Concentration (and expansion) was briefly introduced in Chapter 1, Section 2, to explain the basic rationale of switching. Viewing a switch another way, we can say that it has originating line appearances and terminating line appearances. These are shown in the simplified conceptual drawing in Figure 3.2. Figure 3.2 shows the three different call possibilities of a typical local...

Isdn Protocols And Protocol Issues

ISDN was originally designed for both circuit-switching and packet-switching. In most countries packet-switching did not mature. Circuit-switching is available in a number of telephone companies and administrations, particularly in Europe. In all cases, the B-channel is fully transparent to the network, permitting the user to utilize any protocol or bit sequence so there is end-to-end agreement on the protocol utilized. Of course, the protocol itself, in the body of the info field, should be...

Wire Pair Equipped With Dsl Modems

A digital subscriber line (DSL) modem allows better use of the available bandwidth of a subscriber line. It is assumed in every case that the wire line so equipped will be transporting a digital configuration of binary 1s and 0s. There are a number of approaches to the design of a DSL modem. Because of space limitations of this text, only four designs will be discussed here 1. Asymmetric digital subscriber line (ADSL) 1-4 . 2. High bit rate digital subscriber line (HDSL) 5 . * POTS, plain old...

Shaping Of A Voice Channel And Its Meaning In Noise Measurement Units

This section deals with attenuation distortion or frequency response of a voice channel. Such a channel may be flat or weighted. Weighting means favoring some portion of the frequency spectrum over some other portion or portions. It is simply that we impart more gain or loss for that part of the spectrum which we are favoring. Flat response just means that there is no weighting. If, for instance, we measure the attenuation distortion (frequency response) of the voice channel input on multiplex...

Error Detection and Error Correction

Error detection just identifies that a bit (or bits) has been received in error. Error correction corrects errors at a far-end receiver. Both require a certain amount of redundancy to carry out the respective function. Redundancy, in this context, means those added bits or symbols that carry out no other function than as an aid in the error detection or error correction process. One of the earliest methods of error detection was the parity check. With the 7-bit ASCII code, a bit was added for...

Overview Of Ss No 7 Architecture

The SS No. 7 network model consists of network nodes, termed signaling points (SPs), interconnected by point-to-point signaling links, with all the links between two SPs called a link set. When the model is applied to a physical network, most commonly there is a one-to-one correspondence between physical nodes and logical entities. But when there is a need (for example, a physical gateway node needs to be a member of more than one network), a physical network node may be logically divided into...

Signaling Connection Control Part Sccp 121 Introduction

The signaling connection control part (SCCP) provides additional functions to the message transfer part (MTP) for both connectionless and connection-oriented network services to transfer circuit-related and non-circuit-related signaling information between switches and specialized centers in telecommunication networks (such as for management and maintenance purposes) via a Signaling System No. 7 network. Turn now to Figure 17.3 to see where the SCCP appears in a functional block diagram of an...

Site Selection and Preparation of a Path Profile

In this step we will select operational sites where we will install and operate radio equipment. After site selection, we will prepare a path profile of each link to determine the heights of radio towers to achieve line of sight. Sites are selected using large topographical maps. If we are dealing with a long system crossing a distance of hundreds of miles or kilometers, we should minimize the number of sites involved. There will be two terminal sites, where the system...

Satellite EPIRBs

EPIRBs (emergency position indicating radio beacons) have been in use since World War II. Satellite EPIRBs are comparatively recent, and the concept has evolved considerably. Their principal purpose is to notify authorities of ship or aircraft distress. The latest position of the vessel or aircraft is taken from GPS and relayed along with the distress message. There are two satellite-based EPIRB systems that are operational. The first is operated by COSPAS-SARSAT. This system supports a range...

Isotropic Receive Level

We can directly relate the desired performance to the receive signal level (RSL) at the first active stage of the far-end receiver and the receiver's noise characteristics. A reference RSL is established. Next, we calculate the free-space loss between the transmit antenna and receive antenna. This is a function of distance and frequency (i.e., the microwave transmitter operational frequency). We then calculate the EIRP (effective isotropically radiated power) at the transmit...

Definitions

There are four elements to an international telephone number. CCITT Rec. E.163 recommends that not more than 12 digits make up an international number. These 12 digits exclude the international prefix, which is that combination of digits used by a calling subscriber to a subscriber in another country to obtain access to the automatic outgoing international equipment thus we have 12 digits maximum made up of 4 elements. For example, dialing from Madrid to a specific subscriber in Brussels...