Reverse Battery Signaling

Reverse-battery signaling employs basic methods (1) and (2) just mentioned, and takes its name from the fact that battery and ground are reversed on the tip and ring to change the signal toward the calling end from on-hook to off-hook. Figure 7.10 shows a typical application of reverse-battery signaling in a common-control path. In the idle or on-hook condition, all relays are unoperated and the switch (SW) contacts are open. Upon seizure of the outgoing trunk by the calling switch (exchange)...

Asynchronous and Synchronous Transmission

In the earlier days of printing telegraphy, start-stop transmission, or asynchronous operation, was developed to overcome the problem of synchronism. Here timing starts at the beginning of a character and stops at the end. Two signal elements are added to each character to signal the receiving device that a character has begun and ended. For example, consider the seven-element ASCII code (see Figure 10.1) configured for start-stop operation with a stop element which is of 2 bits duration. This...

Review of Some Digital Switching Concepts

6.11.3.1 Early Notions and New Ideas. In Section 6.11.2 the reader was probably led to believe that the elemental time-switching stage, the TSI, would have 24 or 30 time-slot capacity to match the North American DS1 rate of the European E1 rate, respectively. That means that a manufacturer would have to develop and produce two distinct switches, one to satisfy the North American market and one for the European market. Most switch manufacturers made just one switch with a common internal...

Network Topologies

The IEEE (Ref. 2) defines topology as the interconnection pattern of nodes on a network. We can say that a telecommunications network consists of a group of interconnected nodes or switching centers. There are a number of different ways we can interconnect switches in a telecommunication network. If every switch in a network is connected to all other switches (or nodes) in the network, we call this pattern a full-mesh network. Such a network is shown in Figure 1.9a. The figure has eight nodes.8...

Introduction to Frame Relay Operation

Frame relay may be considered a cost-effective outgrowth of ISDN, meeting high data rate (e.g., 2 Mbps) and low delay data communications requirements. Frame relay encapsulates data files. These may be considered packets, although they are called frames. Thus frame relay is compared to CCITT Rec. X.25 packet service. Frame relay was designed for current transmission capabilities of the network with its relatively wider bandwidths5 and excellent error performance (e.g., BER better than 1 x...

Bits Bauds and Symbols

There is much confusion among professionals in the telecommunication industry over terminology, especially in differentiating, bits, bauds, and symbols. The bit, a binary digit, has been defined previously. The baud is a unit of transmission rate or modulation rate. It is a measure of transitions per second. A transition is a change of state. In binary systems, bauds and bits per second (bps) are synonymous. In higher-level systems, typically rn-ary systems, bits and bauds have different...

Earth Station Link Engineering

Up to this point we have discussed basic satellite communication topics such as access and coverage. This section covers satellite link engineering with emphasis on the earth station. The approach is used to introduce the reader to essential path engineering. It expands on the basic principles introduced in Section 9.2 dealing with LOS microwave. As we saw in Section 9.3.4, an earth station is a distant RF repeater. By international agreement the satellite transponder's...

Metallic Trunk Signaling 791 Basic Loop Signaling

As mentioned earlier, many trunks serving the local area are metallic-pair trunks. They are actually loops much like the subscriber loop. Some still use dial pulses for address signaling along with some form of supervisory signaling. Loop signaling is commonly used for supervision. As we would expect, it provides two signaling states one when the circuit is opened and one when the circuit is closed. A third signaling state is obtained by reversing the direction or changing the magnitude of the...

Telephone User Part TUP

The core of the signaling information is carried in the SIF (see Figure 14.10). The TUP label was described briefly in Section 14.7.2.1. Several signal message formats and codes are described in the paragraphs below. These follow the TUP label. One typical message of the TUP is the initial address message (IAM). Its format is shown in Figure 14.11. A brief description is given of each subfield, providing further insight on how SS No. 7 operates. Common to all signaling messages are the...

Digital Communication by Satellite

There are three methods to handle digital communication by satellite TDMA, FDMA, and over a VSAT network. TDMA was covered in Section 9.3.5.2 and VSATs will be discussed in Section 9.3.8. Digital access by FDMA is handled in a similar fashion as with an analog FDM FM configuration (Section 9.3.5.1). Several users may share a common transponder and the same backoff rules hold in fact they are even more important when using a digital format because the IM products generated in the satellite TWT...

Causes of Echo and Singing

Echo and singing can generally be attributed to the impedance mismatch between the balancing network of a hybrid and its two-wire connection associated with the subscriber loop. It is at this point that we can expect the most likelihood of impedance mismatch which may set up an echo path. To understand the cause of echo, one of two possible conditions may be expected in the local network 1. There is a two-wire (analog) switch between the two-wire four-wire conversion point and the subscriber...

Very SmallAperture Terminal VSAT Networks

VSATs are defined by their antenna aperture (diameter of the parabolic dish), which can vary from 0.5 m (1.6 ft) to 2.5 m (8.125 ft). Such apertures are considerably smaller than conventional earth stations. A VSAT network consists of one comparatively large hub earth terminal and remote VSAT terminals. Some networks in the United States have more than 5000 outlying VSAT terminals (a large drugstore chain). Many such networks exist. 16R (information bit rate) (coded symbol...

Usernetwork Interface Uni And Architecture

ATM is the underlying packet technology of broadband ISDN (B-ISDN). At times in this section, we will use the terms ATM and B-ISDN interchangeably. Figures 20.2 and 20.3 interrelate the two. Figure 20.2 relates the B-ISDN access reference configuration with the ATM user-network interface (UNI). Note the similarities of this figure with Figure 12.15, the reference model for ISDN. The only difference is that the block nomenclature has a B placed in front to indicate broadband. Figure 20.3 is the...

Diversity and Hot Standby

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 and preferred form of diversity for LOS microwave is space diversity. Such a configuration is illustrated in Figure 9.15....

Ss No 7 Relationship To

SS No. 7 relates to OSI (Section 10.10.2) up to a certain point. During the development of SS No. 7, one group believed that there should be complete compatibility with all seven OSI layers. However, the majority of the CCITT working group responsible for the concept and design of SS No. 7 was concerned with delay, whether for the data, telephone, or ISDN user of the digital PSTN. Recall from Chapter 7 that postdial delay is probably the most important measure of performance of a signaling...

Frequency Planning and Frequency Assignment

To derive optimum performance from an LOS microwave system, the design engineer must set out a frequency-usage plan that may or may not have to be approved by the national regulatory organization. The problem has many aspects. First, the useful RF spectrum is limited from above dc (0 Hz) to about 150 GHz. The upper limit is technology-restricted. To some extent it is also propagation-restricted. The frequency ranges of interest for this discussion cover the bands listed in...

Two Wire and Four Wire Transmission

A telephone conversation inherently requires transmission in both directions. When both directions are carried on the same pair of wires, it is called two-wire transmission. The telephones in our homes and offices are connected to a local switching center (exchange) by means of two-wire circuits. A more proper definition for transmitting and switching purposes is that when oppositely directed portions of a single telephone conversation occur over the same...

Technical Requirements of the Digital Network

6.12.2.1 Network Synchronization Rationale and Essentials. When a PCM bit stream is transmitted over a telecommunication link, there must be synchronization at three different levels (1) bit, (2) time slot, and (3) 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...

Vf Repeaters Amplifiers

Analog Repeater Block Diagram

Voice frequency (VF)9 repeaters (amplifiers) in telephone terminology imply the use of unidirectional amplifiers on VF trunks. With one approach on a two-wire trunk, two 9VF or voice frequency refers to the nominal 4-kHz analog voice channel defined at the beginning of this chapter. Figure 5.6 Simplified block diagram of a VF repeater. Figure 5.6 Simplified block diagram of a VF repeater. amplifiers are used on each pair connected by a hybrid at the input and a hybrid at the output. A...

Signaltogaussiannoise Ratio On Pcm Repeatered Lines

As mentioned earlier, noise accumulation on PCM systems is not a crucial issue. However, this does not mean that Gaussian noise (or crosstalk or impulse noise) is unimportant.7 Indeed, it will affect error performance expressed as error rate. Errors are cumulative, and as we go down a PCM-repeatered line, the error performance degrades. A decision in error, whether a 1 or a 0, made anywhere in the digital system, is not recoverable. Thus such an incorrect decision made by one regenerative...

Data Transmission on the Digital Network

Many data users only have analog access to the digital network. In other words, their connectivity to the network is via a subscriber loop to the local serving exchange. It is commonly at this point where the analog channel enters a PCM channel bank and the signal is converted to the standard digital signal. This class of data users will utilize conventional data modems, as described in Section 10.9.5. Other data users will be within some reasonable distance (some hundreds of feet) from a...

Review Exercises

What is the principal drawback in cellular radio considering its explosive growth over the past decade 2. Why is transmission loss so much greater on a cellular path compared to a LOS microwave path on the same frequency covering the same distance 3. What is the function of the MTSO or MSC in a cellular network 4. What is the channel spacing in kHz of the AMPS system What type of modulation does it employ 5. Why are cell site antennas limited to just sufficient height to cover cell boundaries...

Supervisory Line Signaling

Line signaling on wire trunks was based essentially on the presence or absence of dc current. Such dc signals are incompatible with FDM equipment where the voice channel does not extend to 0 Hz. Remember the analog voice channel occupies the band from 300 to 3400 Hz. So the presence or absence of a dc current was converted to an ac tone for one of the states and no tone for the other state. There were two ways to approach the problem. One was called in-band signaling and...

Contents

Chapter 1 Introductory Concepts 1 1.1 What Is Telecommunication 1 1.2 Telecommunication Will Touch Everybody 1 1.3 Introductory Topics in Telecommunications 2 1.3.1 End-Users, Nodes, and Connectivities 2 1.3.2 Telephone Numbering and Routing 5 1.3.3 The Use of Tandem Switches in a Local Area Connectivity 7 1.3.4 Introduction to the Busy Hour and Grade of 1.3.5 Simplex, Half-Duplex, and Full Duplex 9 1.3.6 One-Way and Two-Way Circuits 9 1.3.7 Network Topologies 10 1.3.8 Variations in Traffic...

Associated And Disassociated Channel Signaling

Here we introduce a new concept disassociated channel signaling. Up to now we have only considered associated channel signaling. In other words, the signaling is carried right Figure 7.5 Conventional analog associated channel signaling (upper) versus separate channel signaling (which we call quasi-associated channel signaling) lower . Note Signaling on upper drawing accompanies voice paths signaling on the lower drawing is conveyed on a separate circuit (or time slot). CCS stands for common...

Narrowband Microcell Propagation at PCS Distances

The microcells discussed here have a radial range of < 1 km. One phenomenon is the Fresnel break point, which is illustrated in Figure 18.17. This figure illustrates that signal 18.8 PERSONAL COMMUNICATIONS SERVICES (PCS) 479 18.8 PERSONAL COMMUNICATIONS SERVICES (PCS) 479 Freq. 800. MHz, Tx height 13.4 m, Rx height 1.6 m Figure 18.17 Signal variation on a line-of-sight path in a rural environment. (From Ref. 17, Figure 3.) Freq. 800. MHz, Tx height 13.4 m, Rx height 1.6 m Figure 18.17 Signal...

Basic Concepts Of Cellular Radio

Cellular radio systems connect a mobile terminal to another user, usually through the PSTN. The other user most commonly is a telephone subscriber of the PSTN. However, the other user may be another mobile terminal. Most of the connectivity is extending plain old telephone service (POTS) to mobile users. Data and facsimile services are in various stages of implementation. Some of the terms used in this section have a strictly North American flavor. Figure 18.1 illustrates a conceptual layout of...

Open Systems Interconnection OSI

10.10.2.1 Rationale and Overview of OSI. Data communication systems can be very diverse and complex. These systems involve elaborate software that must run on equipment having ever-increasing processing requirements. Under these conditions, it is desirable to ensure maximum independence among the various software and hardware elements of a system for two reasons To facilitate intercommunication among disparate elements. To eliminate the ripple effect when there is a modification to one software...

The Subset Mouthpiece or Transmitter

The mouthpiece converts acoustic energy (i.e., sound) into equivalent electric energy by means of a carbon granule transmitter. The transmitter requires a direct-current (dc) voltage, a minimum of 3 to 5 volts, across its electrodes. We call this talk battery. In modern systems it is supplied over the subscriber loop and derives from a battery source at the local serving switch as illustrated in Figure 5.3. Current deriving from the local switch supply flows through the carbon grains or...

Time Division Multiple Access TDMA

With TDMA we work in the time domain rather than the frequency domain of FDMA. Each user is assigned a time slot rather than a frequency segment and, during the user's turn, the full frequency bandwidth is available for the duration of the user's assigned time slot. Let's say that there are n users and so there are n time slots. In the case of FDMA, we had n frequency segments and n radio carriers, one for each segment. For the TDMA Figure 18.7 A conceptual drawing of FDMA. case, only one...

What Is Telecommunication

Many people call telecommunication the world's must lucrative industry. In the United States, 110 million households have telephones and 50 of total households in the U.S. have Internet access and there are some 170 million mobile subscribers. Long-distance service annual revenues as of 2004 exceeded 100 x 109 dollars.1 Prior to divestiture (1983), the Bell System was the largest commercial company in the United States. It had the biggest fleet of vehicles, the most employees, and the greatest...

Present North American Loop Design Rules

There are three subscriber loop design methods in this category RRD (revised resistance design), MLRD (modified long route design), and CREG (concentration range extender with gain). 5.4.6.1 Revised Resistance Design (RRD). RRD covers subscriber loop as long as 24 kft. Loop length is broken down into two ranges From 0 to 18,000 ft the maximum loop resistance is 1300 Q, and from 18,000 to 24,000 ft the maximum loop resistance is 1500 Q. H88 loading is used on loops longer than 18,000 ft. Two...

Concepts Of Linkbylink Versus Endtoend Signaling

An important factor to be considered in switching system design that directly affects both signaling and customer satisfaction is postdialing delay. This is the amount of time it takes after the calling subscriber completes dialing until ring-back is received. Ring-back is a backward signal to the calling subscriber indicating that the dialed number is ringing. Postdialing delay must be made as short as possible. Another important consideration is register occupancy time for call setup as the...

Enhancements to DS1

The PCM frame rate is 8000 frames a second. With DS1, each frame has one framing bit. Thus 8000 framing bits are transmitted per second. With modern processor technology, all of the 8000 framing bits are not needed to keep the system frame-aligned. Only one-quarter of the 8000 framing bits per second are actually necessary for framing and the remainder of the bits, 6000 bits per second, can be used for other purposes such as on-line gross error detection and for a maintenance data link. To make...

Logic of Routing

Conceptually, hierarchical routing need not be directly related to a concept of a hierarchy of switching centers, as just described. A routing structure is hierarchical if, for all traffic streams, all calls offered to a given route, at a specific node, overflow to the same set of routes irrespective of the routes already tested.10 The routes in the set will always be tested in the same sequence, although some routes Figure 8.9 A simplified network with circuit groups...

Signaling Techniques 731 Conveying Signaling Information

Signaling information can be conveyed by a number of means from a subscriber to the serving switch and between (among) switches. Signaling information can be transmitted by means such as Duration of pulses (pulse duration bears a specific meaning) Presence or absence of a signal For dc systems, the direction and or level of transmitted current

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...

The Underlying Coaxial Cable System

The coaxial cable employed in the CATV plant has a nominal characteristic impedance (Zo) of 75 Q. A typical response curve for such cable (7 8-in., air dielectric) is illustrated in Figure 17.5. The frequency response of coaxial cable is called tilt in the CATV industry. This, of course, refers to its exponential increase in loss as frequency increases. For 0.5-in. cable, the loss per 100 ft at 50 MHz is 0.52 dB for 550 MHz, 1.85 dB. Such cable systems require equalization. The objective is to...

Operation Of The Telephone Subset

A telephone subset consists of an earpiece, which we may call the receiver the mouthpiece, which we may call the transmitter and some control circuitry in the telephone cradle-stand. Figure 5.3 illustrates a telephone subset connected all the way through its subscriber loop to the local serving exchange. The control circuits are aptly shown. The hook-switch in Figure 5.3 (there are two) are the two little knobs that pop up out of the cradle when the subset is lifted from its cradle. When the...

Differences Between 80211 and 80215

At first blush, 802.11 and 802.15 seem very similar. Their objectives of operation and method of operation seem very similar. However, we point up three major differences 13.5.1.1 Power Levels and Coverage. RF power levels of 802.15 devices run from 1 mW to 2.5 mW and up to high power of 100 mW. Coverage is roughly in the range of 10 m. Modulation is Gaussian FSK. 13.5.1.2 Control of the Media. Control of a medium usually refers to the allocation of bit rate capacity. The medium can remain...

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 1. Increase conductor diameter (covered above). 2. Use amplifiers and or range extenders.6 4. Use digital subscriber line (DSL) techniques (covered in Chapter 6). 5. Employ remote concentrators or switches (see Section 4.3). Amplifiers in the subscriber loop extend the transmission range. Perhaps...

End Users Nodes and Connectivities

End-users, as the term tells us, provide the inputs to the network and are recipients of network outputs. The end-user employs what is called an I O, standing for input output Figure 1.1 The PSTN consists of local networks interconnected by a long-distance network. Figure 1.1 The PSTN consists of local networks interconnected by a long-distance network. (device). An I O may be a PC, computer, telephone instrument, cellular PCS telephone or combined device, facsimile, or conference TV equipment....

Token Ring and FDDI

Token ring and FDDI fiber distributed data interface are examples of controlled access protocols. Both protocols are now obsolete. We briefly review the concept so the reader can gain some knowledge of controlled or disciplined access. A typical token-passing ring is illustrated in Figure 11.11. A ring is formed by physically folding the medium back on itself. Each LAN station regenerates and repeats each bit and serves as a means of attaching one or more data terminals e.g., workstations, PCs,...

Physical Layer

The physical layer consists of two sublayers. The physical medium PM sublayer includes only physical medium-dependent functions. The transmission convergence TC sublayer performs all functions required to transform a flow of cells into a flow of data units i.e., bits which can be transmitted and received over a physical medium. The service data unit SDU crossing the boundary between the ATM layer and the physical layer is a flow of valid cells. The ATM layer is unique independent of the...

Introduction to Optical Fiber as a Transmission Medium

Optical fiber consists of a core and a cladding, as illustrated in Figure 9.23. At present the most efficient core material is silica SiO2 . The cladding is a dielectric material that surrounds the core of an optical fiber. 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...

Synchronous Signal Structure

SONET is based on a synchronous signal comprised of 8-bit octets, which are organized into a frame structure. The frame can be represented by a two-dimensional map comprising N rows and M columns, where each box so derived contains one octet or byte . The upper left-hand corner of the rectangular map representing a frame contains an identifiable marker to tell the receiver it is the start of frame. SONET consists of a basic, first-level, structure called STS-1, which is discussed in the...

Transmission of Uncompressed Video on CATV Trunks

Uncompressed Video Frame Structure

Video, as we discuss in Chapter 16, is an analog signal. It is converted to a digital format using techniques that are similar to the 8-bit PCM covered in Chapter 6, Section 6.2. A major difference is in the sampling rate. Broadcast quality TV is generally oversampled. Here we mean that the sampling rate is greater than the Nyquist rate. The Nyquist rate, as we will remember, requires that the sampling rate be two times the highest frequency of interest. In this case, for the video, the highest...

Frequency Division Multiplex

Frequency Division Multiplexing Figure

With FDM the available channel bandwidth is divided into a number of nonoverlapping frequency slots. Each frequency slot or bandwidth segment carries a single information-bearing signal such as a voice channel. We can consider an FDM multiplexer as a frequency translator. At the opposite end of the circuit, a demultiplexer filters and translates the frequency slots back into the original information bearing channels. In the case of a telephone channel, a frequency slot is...

Bluetooth WPAN Connectivity Topologies

A piconet is a WPAN formed by a Bluetooth device serving as a master in the piconet and one or more Bluetooth devices serving as slaves. A frequency-hopping channel based on the address of the master defines each piconet. All devices participating in communications in a given piconet are synchronized to the The payload can be fragmented to fit into one, three, or five 625 microsecond slots. 68 - 72 bits______54 bits______0 - 2745 bits The payload can be fragmented to...

Switching A Network

Route or connection between exchanges. We could say we are dimensioning the route. To dimension the route correctly we must have some idea of its usage that is, how many people will wish to talk at once over the route. The usage of a transmission route or switch brings us into the realm of traffic engineering and usage may be defined by two parameters 1 calling rate, or the number of times a route or traffic path is used per unit time period or more properly defined, the call intensity per...

Pcm System Operation

PCM channel banks operate on a four-wire basis. Voice channel inputs and outputs to and from a PCM multiplex channel bank are four-wire, or must be converted to four-wire in the channel bank equipment. Another term commonly used for channel bank is codec, which is a contraction for coder-decoder even though the equipment carries out more functions than just coding and decoding. A block diagram of a typical codec PCM channel bank is shown in Figure 6.9. A codec accepts 24 or 30 voice channels,...

Color Transmission

Three color transmission standards exist NTSC National Television System Committee North America, Japan, and many Latin American countries SECAM Sequential color and memory Europe PAL Phase alternation line Europe The systems are similar in that they separate the luminance and chrominance information and transmit the chrominance information in the form of two color difference signals, which modulate a color subcarrier transmitted within the video band of the luminance signal. The systems vary...

The Composite Signal

The word composite is confusing in the TV industry. On one hand, composite may mean the combination of the full video signal plus the audio subcarrier the meaning here is narrower. Composite in this case deals with the transmission of video information as well as the necessary synchronizing information. Consider Figure 16.3. An image that is made up of two black squares is scanned. The total time for the scan line is 63.5 sec, of which 53.3 sec is available for the transmission of actual video...

An Appreciation Of Video Transmission

A video transmission system must deal with four factors when transmitting images of moving objects 1. Perception of the distribution of luminance or simply the distribution of light and shade 2. Perception of depth or a three-dimensional perspective 3. Perception of motion relating to the first two factors above 4. Perception of color hues and tints Monochrome TV deals with the first three factors. Color TV includes all four factors. A video transmission system must convert these three or four...

European Cordless Telephones

The first-generation European cordless telephone provided for eight channel pairs near 1.7 MHz base unit transmit and 47.5 MHz handset transmit . Most of these units could only access one or two channel pairs. Some called this standard CT0. This was followed by another analog cordless telephone based on a standard known as CEPT CT1. CT1 has 40 25-kHz duplex channel pairs operating in the bands 914-915 MHz and 959-960 MHz. There is also a CT1 in the bands 885-887 MHz and 930-932 MHz, which do...

Diversity A Technique to Mitigate the Effects of Fading and Dispersion

We discuss diversity to reduce the effects of fading and to mitigate dispersion. Diversity was briefly covered in Section 9.2.5 where we dealt with LOS microwave. In that section we discussed frequency and space diversity. In principle, such techniques can be employed either at the base station and or at the mobile unit, although different problems have to be solved for each. The basic concept behind diversity is that two or more radio paths carrying the same information are...

The Human Voice

Frequency Range Human Voice

Human voice communication depends on the voice-generating mechanism of mouth and throat being the initial transmitter, with the acuity of the ear being the receiver. Frequency components of the human voice extend down to some 20 Hz and as high as 32,000 Hz. The lower frequency components carry the voice energy and the higher frequency components carry emotion. Figure 5.1 shows a distribution of energy and emotion of the typical human voice. The human ear and many devices and components of the...

Coding

Older PCM systems used a 7-bit code, and modern systems use an 8-bit code with its improved quantizing distortion performance. The companding and coding are carried out together, simultaneously. The compression and later expansion functions are logarithmic. A pseudologarithmic curve made up of linear segments imparts finer granularity to low-level signals and less granularity to the higher-level signals. The logarithmic curve follows one of two laws, the A-law and the -law pronounced mu-law ....

An Overview of the MPEG2 Compression Technique

This section is based on the ATSC Advanced Television System Committee version of MPEG-2, which is used primarily for terrestrial broadcasting and cable TV. The objective of the ATSC standard Refs. 16, 17 is to specify a system for the transmission of high-quality video, audio, and ancillary services over a single 6-MHz channel.8 The ATSC system delivers 19 Mbps of throughput on a 6-MHz broadcasting channel and 38 Mbps on a 6-MHz CATV channel. The video source, which is encoded, can have a...

Approaches to PCM Switching

Tst Switch With Block Diagram

A digital switch's architecture is made up of two elements, called T and S, for time-division switching T and space-division switching S , and can be made up of sequences of T and S. For example, the AT amp T No. 4 ESS is a TSSSST switch No. 3 EAX is an SSTSS and the classic Northern Telecom DMS-100 is TSTS-folded. Many of these switches e.g., DMS-100 are still available. One thing these switches have in common is that they had multiple space S stages. This has now changed....

Fades Fading and Fade Margins

In Section 9.2.3.4.2 we showed how path loss can be calculated. This was a fixed loss that can be simulated in the laboratory with an attenuator. On very short radio paths below about 10 GHz, the signal level impinging on the distant-end receiving antenna, assuming full LOS conditions, can be calculated to less than 1 dB. If the transmitter continues to give the same output, the RSL will remain uniformly the same over long periods of time, for years. As the path is extended, the measured RSL...

Definitions

Sdh Container Analogy

An STM is the information structure used to support section layer connections in the SDH. It is analogous to STS in the SONET regime. STM consists of information payload and section overhead SOH information fields organized in a block frame structure that repeats every 125 sec. The information is suitably conditioned for serial transmission on selected media at a rate that is synchronized to the network. A basic STM STM-1 is defined at 155,520 kbps....

IEEE 80216 MAC Requirements

Ieee 802 Mac Protocol

The 802.16 MAC design addresses network access in the wireless environment affording very efficient use of the spectrum. Its broadband services support high bit rates and a n PS Symbol Rate x Frame Length 4 n PS Symbol Rate x Frame Length 4 Figure 13.7 Atypical IEEE 802.16 TDD frame, 10-66 GHz. Figure 13.7 Atypical IEEE 802.16 TDD frame, 10-66 GHz. Figure 13.8 TDD downlink subframe. DIUC, downlink interval usage code. broad range of QoS requirements. Its broadband services include IPV4, IPV6,...

CSMA and Csmacd Access Techniques

Network Interface Controller Aui Mau Mdi

Carrier sense multiple access CSMA is an early LAN access technical, which some simplistically call listen before transmit. This listen before transmit idea gives insight into the control mechanism. Essentially, if user No. 2 is transmitting, user No. 1 and all others hear that the medium is occupied and refrain from using it. The technique was prone to collisions due to propagation and processing delays to detect that the line is busy. In that open period before carrier detection, user No. 1,...

Discussion of the Erlang and Poisson Traffic Formulas

When dimensioning a route, we want to find the optimum number of circuits to serve the route. There are several formulas at our disposal to determine that number of circuits based on the BH traffic load. In Section 4.2.1.2, 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 holding-time distributions, 2 number of traffic sources, 3 availability full or limited ,...

Setup and Release of VCCs

The setup and release of VCCs at the user-network interface UNI can be performed in various ways Without using signaling procedures. Circuits are set up at subscription with permanent or semipermanent connections. By meta-signaling procedures, where a special VCC is used to establish or release a VCC used for signaling. Meta-signaling is a simple protocol used to establish and remove signaling channels. All information interchanges in meta-signaling are carried out via single cell messages....

The Virtual Path Level

The virtual path VP is a generic term for a bundle of virtual channel links all the links in a bundle have the same endpoints. A VPI identifies a group of VC links, at a given reference point, that share the same VPC. A specific value of VPI is assigned each time a VP is switched in the network. A VP link is a unidirectional capability for the transport Figure 20.13 Relationship between VC and VP, and the transmission path. 11 VC cross-connect A network element which connects VC links. It...

LAN Bridges

Encapsulation Bridge

Whereas repeaters have no intelligence, bridges do. Bridges can connect two LANs, at the data-link or MAC protocol level. There are several varieties of bridges, depending on the intelligence incorporated. There is the transparent bridge that builds a list of nodes the bridge sees transmitting on either side. It isolates traffic and will not forward traffic that it knows is destined to another station on the same side of the bridge as the sending station. The bridge is able to isolate traffic...

In the DS3 Frame

Stm4 Frame Structure

One of the most popular high-speed digital transmission systems in North America is DS3 operating at a nominal transmission rate of 45 Mbps. It is also being widely implemented for transport of SMDS. The system used to map ATM cells into the DS3 format is the same that is used for SMDS. To map ATM cells into a DS3 bit stream, the physical layer convergence protocol PLCP is employed. A DS3 PLCP frame is shown in Figure 20.16. Figure 20.16 Format of DS3 PLCP frame. From Ref 1, courtesy of...

Telecommunication Will Touch Everybody

In industrialized nations, the telephone is accepted as a way of life. The telephone is connected to the public switched telecommunications network PSTN for local, national, and international voice communications. These same telephone connections may also 'The source for the data in this paragraph is the US FCC Study on Telephone Trends 2004. Fundamentals of Telecommunications, Second Edition, by Roger L. Freeman ISBN 0-471-71045-8 Copyright 2005 by Roger L. Freeman carry data and image...

Introduction to the Busy Hour and Grade of Service

Minutes Use Busy Hour Usage Voice

This inefficiency stems from the number of circuits and the revenue received per circuit. The PSTN would approach 100 efficiency if all the circuits were used all the time. The facts are that the PSTN approaches total capacity utilization for only several hours during the working day. After 10 P.M. and before 7 A.M., capacity utilization may be 2 or 3 . The network is dimensioned sized to meet the period of maximum usage demand. This period is called the busy hour...

The Electrical Telegraph An Early Form of Long Distance Communications

Telegraph Morse Code

Let's connect a battery terminal or electrode with a length of copper wire looping it back to the other electrode. A buzzer or other sound-generating device is inserted into that loop at the farthest end of the wire before looping back we now have the essentials of a telegraph circuit. This concept is shown in Figure 2.2. The loop has a certain resistance, which is a function of its length and the diameter of the wire. The longer we make the loop, the greater the resistance. As the length...

VoIP Gateway

Voip Gateway Block Diagram

Gateways are defined in different ways by different people. In our context here a gateway is a server it may also be called a media gateway. Figure 15.4 illustrates a typical gateway. It sits on the edge of the network and carries out a switching function of a local, tandem, or toll-connecting PSTN switch described in Chapters 3 and 6. Media gateways are part Figure 15.4 A media gateway from one perspective. API, application programs interface. From IEC on-line Jan. 2003 . of the physical...

Site Selection and Preparation of a Path Profile

Microwave Relay Towers

In this step we will select operational site 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...

Correlation Key Concept in Direct Sequence Spread Spectrum In

Direct sequence DS spread spectrum systems, the chip rate is equivalent to the code generator clock rate. Simplistically, a chip can be considered an element of RF energy with a certain recognizable binary phase characteristic. A chip or chips is are a result of direct sequence spreading by biphase modulating an RF carrier. Being that each chip has a biphase modulated characteristic, we can identify each one with a binary 1 or binary 0. These chips derive from biphase PSK modulating a carrier...

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 e.g., a physical gateway node needs to be a member of more than one network , a physical network node may be logically divided into more than...

Modem Selection Considerations

4ary Fsk Signal Space

The critical parameters that affect data transmission have been discussed these are amplitude-frequency response sometimes called amplitude distortion , envelope delay distortion, and noise. Now we relate these parameters to the design of data modems to Figure 10.13 Pulse response through a Gaussian band-limited channel GBLC . Gaussian refers to a channel limited by thermal noise that has a Gaussian distribution. See Ref. 1. Figure 10.13 Pulse response through a Gaussian band-limited channel...

References

Telecommunications Transmission Engineering, 3rd ed., Bellcore, Piscataway, NJ, 1989. 2. Raymond Steele, ed., Mobile Radio Communications, IEEE Press, New York, and Pentech Press, London, 1992. 3. Y. Okumura et al., Field Strength and Its Variability in VHF and UHF Land Mobile Service, Rec. Electr. Commun. Lab., 16, Tokyo, 1968. 4. M. Hata, Empirical Formula for Propagation Loss in Land-Mobile Radio Services, IEEE Trans. Vehicular Technology, VT-20, 1980. 5. F. C. Owen and C. D. Pudney,...

Frequency Reuse

Because of the limited bandwidth allocated in the 800-MHz band for cellular radio communications, frequency reuse is crucial for its successful operation. A certain level of interference has to be tolerated. The major source of interference is cochannel interference from a nearby cell using the same frequency group as the cell of interest. For the 30-kHz bandwidth AMPS system, Ref. 5 suggests that C I be at least 18 dB. The primary isolation derives from the distance between the two cells with...

The Atm Cell Key To Operation 2041 ATM Cell Structure

Bit Error Control Hec Atm

As we mentioned earlier, the ATM cell consists of 53 octets, 5 of which make up the header and 48 make up the payload or info portion of the cell.5 Figure 20.4 shows an ATM cell stream, delineating the 5-octet header and 48-octet information field of each cell. Figure 20.5 shows the detailed structure of cell headers at the user-network interface UNI Figure 20.5a and at the network-node interface NNI 6 Figure 20.5b . We digress a moment to discuss why a cell was standardized at 53 octets. The...

Call Progress Audible Visual

This type of signaling we categorize in the forward direction and in the backward direction. In the forward direction there is alerting. This provides some sort of audible-visual means of informing the called subscriber that there is a telephone call waiting. This is often done by ringing a telephone's bell. A buzzer, chime, or light may also be used for alerting. The remainder of the techniques we will discuss are used in the backward direction. Among these are audible tones or voice...

Voice Transmission

3.2.2.1 Loudness Rating and Its Predecessors. Historically, on telephone connections, the complaint has been that at the receiving telephone the distant talker's voice was not loud enough. Hearing sufficiently well on a telephone connection is a subjective matter. This is a major element of quality of service QoS . Various methods have been derived over the years to rate telephone connections regarding customer satisfaction. The underlying cause of low signal level is loss across the network....

The Essential Functions of a Local Switch

As we mentioned above, means are provided in a local switch to connect each subscriber line to any other in the same exchange. In addition, any incoming trunk must be able to connect to any subscriber line and any subscriber to any outgoing trunk.7 These switching functions are remotely controlled by the calling subscriber, whether she he is a local subscriber or long-distance subscriber. These remote instructions are transmitted to the switch exchange by off-hook, on-hook,8 and dial...

Cable Characteristics

Coaxial Cable Characteristic

When employed in the long-distance telecommunication plant, standard coaxial cable sizes are as follows The fractions express the outside diameter of the inner conductor over the inside diameter of the outer conductor. For instance, for the large bore cable, the outside diameter of the inner conductor is 0.104 in. and the inside diameter of the outer conductor is 0.375 in. This is illustrated in Figure 9.35. As can be seen from Eq. 9.27 in Figure 9.35, the ratio of the diameters of the inner...

Subscriber Loop Length Limits

It is desirable from an economic standpoint to permit subscriber loop lengths to be as long as possible. Thus the subscriber serving area could become very large. This, in turn, would reduce the number of serving switches required per unit area affording greater centralization, less land to buy, fewer buildings, simpler maintenance, and so forth. Unfortunately, there are other tradeoffs forcing the urban suburban telecommunication system designer to smaller serving areas and more switches. The...

Design of the Fiber Optic Portion of an HFC System

Www Fibercoax Net

Before proceeding with this section, it is recommended that the reader turn back to Chapter 9 for a review of the principles of fiber-optic transmission. There are two approaches to fiber-optic transmission of analog CATV signals. Both approaches take advantage of the intensity modulation characteristics of the fiber-optic source. Instead of digital modulation of the source, amplitude modulation analog is employed. The most common method takes the entire CATV spectrum as it would appear Figure...

Structure of the SCCP

Diagram Sccp

The basic structure of the SCCP is illustrated in Figure 14.9. It consists of four functional 1. SCCP Connection-Oriented Control. This controls the establishment and release of signaling connections for data transfer on signaling connections. 2. SCCP Connectionless Control. This provides the connectionless transfer of data units. 3. SCCP Management. This functional block provides the capability, in addition to the signal route management and lower control functions of the MTP, to handle the...

What Is Frequency

360 Degrees Radians Per Second

To understand more advanced telecommunication concepts, we need a firm knowledge of frequency and related parameters such as band and bandwidth, wavelength, period, and phase. Let us first define frequency and relate it to everyday life. The IEEE defines frequency as the number of complete cycles of sinusoidal variation per unit time. The time unit we will use is the second. For those readers with a mathematical bent, if we plot y sin x, where x is expressed in radians, a sine wave is developed...

Multiple Access to a Communication Satellite

Frame And Burst Format Tdma

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 multiple access TDMA ....

Quality Of Service Voice Data And Image 321 Signalto Noise Ratio

Signal-to-noise ratio S N or SNR is the most widely used parameter for measurement of signal quality in the field of transmission. Signal-to-noise ratio expresses in decibels the amount that signal level exceeds the noise level in a specified bandwidth. As we review the several types of material to be transmitted on a network, each will require a minimum S N to satisfy the user or to make a receiving instrument function within certain specified criteria. The following are S N guidelines at the...

Phase Distortion

Attenuation Distortion

We can look at a voice channel as a bandpass filter. A signal takes a finite time to pass through the telecommunication network. This time is a function of the velocity of Figure 3.3 Typical attenuation distortion across a voice channel bandpass filter. Crosshatched areas are response specifications, whereas the wavy line is the measured response. Figure 3.3 Typical attenuation distortion across a voice channel bandpass filter. Crosshatched areas are response specifications, whereas the wavy...

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...

Telephone Numbering and Routing

Every subscriber in the world is identified by a number, which is geographically tied to a physical location.4 This is the telephone number. The telephone number, as we used it 4This wiH change. At least in North America, we expect to have telephone number portability. Thus, whenever one moves to a new location, she he takes their telephone number with them. Will we see a day when telephone numbers are issued at birth, much like social security numbers above, is seven digits long. For example...

Critical Impairments to the Transmission of Data

Attenuation Distortion

The effect of various telephone circuit parameters on the capability of a circuit to transmit data is a most important consideration. The following discussion is intended to familiarize the reader with problems most likely to be encountered in the transmission of data over analog or mixed analog-digital circuits. We make certain generalizations in some cases, which can be used to facilitate planning the implementation of data systems. 10.9.3.1 Phase Distortion. Phase distortion constitutes the...

Signalto Noise Ratio SN Versus Carrierto Noise Ratio CN in CATV Systems

We have been using S N and C N many times in previous chapters. In CATV systems S N has a slightly different definition as follows Ref. 2 This relationship is expressed by the signal-to-noise ratio, which is the difference between the signal level measured in dBmV, and the noise level, also measured in dBmV, both levels being measured at the same point in the system. S N can be related to C N on CATV systems as This is based on Carson Ref. 4 , where the premise is noise just perceptible by a...

Digital Data Waveforms

Polar Line Coding

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 coding...

Thermal Noise in CATV Systems

We remember from Section 3.3.3 that thermal noise is the most common type of noise encountered in telecommunication systems. In most cases, it is thermal noise that sets the sensitivity of a system, its lowest operating threshold. In the case of a CATV system, the lowest noise levels permissible are set by the thermal noise level at the antenna output terminals, at repeater amplifier inputs, or at a subscriber's TV set without producing snowy pictures. Consider the following, remembering we are...

Satellite Communications Receiving System Figure of Merit GT

Figure Merit Satellite

Figure of merit of a satellite communications receiving system, G T, has been introduced into the technology to describe the capability of an earth station or a satellite to receive a signal. It is also a convenient tool in the link budget analysis.14 A link budget is used by the system engineer to size components of earth stations and satellites, such as RF output power, antenna gain and directivity, and receiver front-end characteristics. G T can be written as a mathematical identity G T GdB...

Lineof Sight Microwave

Los Microwave Picture

Line-of-sight LOS microwave provides a comparative broadband connectivity over a single link or a series of links in tandem. We must be careful on the use of language here. First a link, in the sense we use it, connects one radio terminal to another or to a repeater site. The term link was used in Figure 9.1 in the network sense. Figure 9.2 illustrates the meaning of a link in line-of-sight microwave. Care must also be taken with the use of the expression line-of-sight....

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 it fills in. The signaling...