Articles

Pulse Amplitude Modulation Circuit Diagram

Pulse Amplitude Modulation Circuit

Other larger groups can be formed, for example 6 mastergroups may be combined to form a jumbogroup with 3600 voice channels. To recover the original baseband signals from the various groups, the appropriate number of filtering demodulation processes will have to be carried out. At each stage of the demodulation process, the correct carrier will have to be reinstated for this to be possible. In FDM, voice signals were ''stacked'' in the frequency spectrum so that many such signals could be...

Phase Division Multiplexing

Time Domain Plot Phase 270 Degree

The term phase describes the position of the waveform relative to time zero. If we think of the wave as something that can be shifted backward or forward along the time axis, phase describes the amount of that shift. It indicates the status of the first cycle. Phase is measured in degrees or radians 360 degrees is 2n radians . A phase shift of 360 degrees corresponds to a shift of a complete period a phase shift of 180 degrees corresponds to a shift of half a period and a phase shift of 90...

Location Registration and Location Update

Tmsi Reallocation Procedure

Before a mobile station can be called or gets access to services, the subscriber has to register with the mobile network PLMN . This is usually the home network where the subscriber has a service contract. However, the subscriber can equally register with a foreign network provider in whose service area he or she is currently visiting, provided there is a roaming agreement between the two network operators. Registration is only required if there is a change of networks, and therefore a VLR of...

OMA PoC Talk Burst Control

PoC is a half-duplex, one-way communication method between participants and implies that one party speaks while the other parties listen this requires a talk burst control mechanism, also known as floor control. The talk burst control mechanism in OMA PoC is a confirmed request grant procedure within the PoC server performing the controlling PoC function, insuring that only one user is sending media at a given time. The talk burst control mechanism in OMA PoC forms a second control layer under...

GSM Network Connection to SS7 Networks

The MSC is the Central Switching function of the GSM network. The MSC is connected to a SS7 network for the purpose of signaling and performing database queries. The SS7 network uses a network node called the STP, which is a packet switching node (can be SS7, IP, or X.25). Using a 64 Kbps channel connection between STPs, the network can process its signaling information. Next in a SS7 network is the use of the SCP, which houses the databases congruent to the network. In many cases these...

Source Coding and Speech Processing

Source coding reduces redundancy in the speech signal and thus results in signal compression, which means that a significantly lower bit rate is achieved than needed by the original speech signal. The speech coder decoder is the central part of the GSM speech processing function, both at the transmitter Figure 6.2 as well as at the receiver Figure 6.3 . The functions of the GSM speech coder and decoder are usually combined in one building block called the codec COder DECoder . Figure 6.2...

Teleservices and Bearer Services

Teleservices are defined at the user interfaces but the bearer services at the network interfaces of the terminal equipment as can be seen in figure 5.3.1. teleservices are telecommunication services which provide full communication in between users according to the agreed protocol of network operators including the terminal equipment functions bearer services are telecommunication services providing the signal transmission capabilities in between network access points Fig 5.3.1 Definitions of...

Dms Switch Architecture

Coordinator Processor Ewsd

Hardware architecture of DMS-100. Fig. 6.11. Hardware architecture of DMS-100. Processor Modules. The main components of processor modules are DMS-Core Processor, file processor, Application Processor and LPP. The DMS-core processor supports the call processing, performs control function, down loading DMS super-node software and supports other peripheral controllers. The core processors is a set of central processing units. The file processor provides access to large data files for...

Key Factors In Communication Network Evolution

In the previous section we traced the evolution of communication networks from telegraphy to the emerging integrated services networks. Before proceeding with the technical details of networking, however, we pause to discuss factors that influence the evolution of communication networks. Figure 1.19 shows the three traditional factors technology, regulation, and market. To these we add standards, a set of technical specifications followed by manufacturers or service providers, as a fourth...

Administrative Closure

Phases Telecommunications Project

Performance measurement documentation 2. Documentation of the product oi the project 1. Project archives 2 Formal acceptance Any loose ends are tied, and the project is essentially 'closed'. Although many team members are leaving the project, or maybe even have already left, the PM should get input from each of them on the lessons learned during the project, in order to help the next team to avoid the problems that this one faced. The intent is one of helping future projects - not to cast blame...

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...

Terrestrial Microwave

Waves Hitting Satellite Dish

Microwaves do not follow the curvature of the earth and therefore require line-of-sight transmission and reception equipment. The distance coverable by a line-of-sight signal depends to a large extent on the height of the antenna the taller the antennas, the longer the sight distance. Height allows the signal to travel farther without being stopped by the curvature of the planet and raises the signal above many surface obstacles, such as low hills and tall buildings that would otherwise block...

Subscriber Loop Design

The cables that connect the telephone handsets or other devices to the local switching office or end office is referred as subscriber loop or local loop. Every suscriber has his own pair of wires to the local switching office. Twisted pair local loop is an excellent transmission medium for analog voice signals. But it is limited to low frequency audio signals. The introduction of fiber cable needs a device at subscriber premises to convert electrical energy into light energy and this is the...

PLMN Configurations and Interfaces

Plmn Interface Gsm

The fixed connections for transport of signaling and user data in a GSM PLMN Figure 3.8 are standard transmission lines. Within the SMSS, lines with a transmission rate of 2 Mbit s or 1.544 Mbit s in North America are typically used fixed lines, mostly microwave links or leased lines . The BSS uses mostly 64 kbit s lines. Signaling has two fundamentally different parts GSM-specific signaling within the BSS, including the air interface, and signaling within the SMSS and with other PLMN in...

Pulse Amplitude Modulation PAM

Modulateur Pam

The first step in analog-to-digital encoding is called pulse amplitude modulation PAM . This technique takes analog information, samples it, and generates a series of pulses based on the results of the sampling. The term sampling means measuring the amplitude of the signal at equal intervals. The method of sampling used in PAM is more useful to other areas of engineering than it is to data communication. However, PAM is the foundation of an important analog-to-digital encoding method called...

Regenerative Repeaters

Regenerative Repeater Block Diagram

As we are 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 6.11 is a simplified block diagram of a...

Digital Switching Systems

Various facilities of digital switching and transmission is the reason why the analog switching is slowly getting replaced by digital switching. The incorporation of digital switching and transmission technique into telecommunications altered the whole telecommunication industries setup. The reliability of digital switching system is becoming increasingly important for users of telephone services. Voice and or data can be represented using digital signals efficiently than analog signals. A...

Microstrip Directional Couplers

Let us consider two parallel microstrip lines that are placed so close to each other that the fields of the lines couple to each other. Then a wave propagating in one line can excite a wave in the other line. The fields of a coupled line can be presented as a superposition of an even mode and an odd mode, shown in Figure 6.9. In case of the even mode the currents of the lines are equal and in the same direction in case of the odd mode they are equal but in the opposite directions. A coupled...

Definition of Echo and Singing

As the name implies, echo in telephone systems is the return of a talker's voice. It is most apparent to the talker himself or herself. Secondarily, it can also be an annoyance to the listener. To be an impairment, the returned voice must suffer some noticeable delay. Thus we can say that echo is a reflection of the voice. The cause of echo is impedance mismatches that might be present any place in the electrical telephone connection. Echo is a major annoyance to the telephone user....

Classification and Comparison of MAC Protocols

Classification Mac Protocols

In general, wireless communication has a variety of MAC protocols, which can be classified into distinct groups according to different criteria. Based on whether a central controller is involved in coordination, WSNs' MAC protocols can be categorized as centralized, distributed (decentralized), and hybrid. Actually, hybrid protocols attempt to combine the advantages of centralized and distributed schemes, but can be more complex. Figure 18.3 shows such classification 97 . Centralized MAC...

The Strowger Step By Step Switching System

Several electromechanical switching system were developed around 1880-1890 to eliminate the limitations of manual exchanges and to establish automatic exchanges to improve the speed and carry more leads subscribers . Among those electromechanical automatic switches, strowger's step by step switching system was the most pupular and widely used and even now in some part of the world, it is in use. The history of this switching system is described briefly in the following paragraph. The first...

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...

Quadrature Detector Circuit

Quadrature Detector Circuit

Figure 5.4. a The phasor diagram when signal frequency is lower than carrier frequency. b The phasor diagram when signal frequency is higher than carrier frequency. Figure 5.4. a The phasor diagram when signal frequency is lower than carrier frequency. b The phasor diagram when signal frequency is higher than carrier frequency. Replacing R2 in Equation 5.2.7 by Z2 gives It is evident that V1 and V2 are no longer at right angles to each other. The angle between them depends on the magnitude and...

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...

Continuous Variable Slope Delta Modulation

Adaptive Delta Modulation

Continuous Variable Slope Delta Modulation was first proposed by Greefkes and Riemes in 1970. CVSD requires a 1-bit sample length compared to the 8 bits used in PCM, so more samples can be sent in the same bandwidth. As a result, CVSD is more tolerant of communications errors. Because of its error tolerance, CVSD performs well in noisy channels, and for this reason, it has been widely used in military communications systems.The ability to tolerate errors is also what makes CVSD attractive for...

Building Penetration Loss Models

Diffracted Building

The building penetration loss is defined as the power loss that an electromagnetic wave undergoes as it propagates from outside a building towards one or several places inside this building. This parameter is determined from the comparison between the external field and the field present in different parts of the building where the receiver is located. Penetration loss models, being integrated into the coverage prediction tools, must take into account the environment around the buildings which...

Reflection and Transmission at a Dielectric Interface

Oblique Incidence Parallel Polarization

Let us consider a plane wave that is incident at a planar interface of two lossless media, as illustrated in Figure 2.7. The wave comes from medium 1, which is characterized by 1 and 1, to medium 2 with 2 and 2. The planar interface is at z 0. The angle of incidence is d1 and the propagation vector k 1 is in the xz-plane. Part E from the incident field is reflected at an angle d and part E2 is transmitted through the interface and leaves at an angle of 62. Figure 2.7 Reflection and transmission...

Conclusion And Future Work

Through a series of experiments and measurements made at various locations of the AUT's WY office building, we gained an insight into the performance of Wi-Fi links in an office environment. This project involves both literature review and practical investigation regarding the IEEE 802.11b protocol known as Wi-Fi. A number of conclusions can be drawn from the findings of this study. The use of electromagnetic waves as the medium instead of cables presents many technical challenges. To begin...