Статьи 6 семестр / Работы / What advantages can a digital system provide for the analog customer

What advantages can a digital system provide for the analog customer?

An increasing majority of applications in electronics, as well as in most other technologies, use digital techniques to perform operations that were once performed using analog methods. The chief reasons for the shift to digital technology are:

Digital systems are generally easier to design. This is because the circuits that are used are switching circuits, where exact values of voltage or current are not important, only the range (HIGH or LOW) in which they fall.

Information storage is easy. This is accomplished by special switching circuits that can latch onto information and hold it for as long as necessary.

Accuracy and precision are greater. Digital systems can handle as many digits of precision as you need simply by adding more switching circuits. In analog systems, precision is usually limited to three or four digits because the values of voltage and current are directly dependent on the circuit component values.

Operation can be programmed. It is fairly easy to design digital systems whose operation is controlled by a set of stored instructions called a program. As technology progresses, this is becoming even easier. Analog systems can also be programmed, but the variety and complexity of the available operations is severely limited.

Digital circuits are less affected by noise. Spurious fluctuations in voltage (noise) are not as critical in digital systems because the exact value of a voltage is not important, as long as the noise is not large enough to prevent us from distinguishing a HIGH from a LOW.

More digital circuitry can be fabricated on IC chips. It is true that analog circuitry has also benefited from the tremendous development of IC technology, but its relative complexity and its use of devices that cannot be economically integrated (high-value capacitors, precision resistors, inductors, transformer) have prevented analog systems from achieving the same high degree of integration.

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Definition of Digital – A method of storing, processing and transmitting information through the use of distinct electronic or optical pulses that represent the binary digits 0 and 1.

Advantages of Digital: Less expensive, More reliable, Easy to manipulate, Flexible, Compatibility with other digital systems, Only digitised information can be transported through a noisy channel without degradation, Integrated networks

Disadvantages of Digital: Sampling Error, Digital communications require greater bandwidth than analogue to transmit the same information, The detection of digital signals requires the communications system to be synchronised, whereas generally speaking this is not the case with analogue systems.

Definition of Analogue – Analogue is a transmission standard that uses electrical impulses to emulate the audio waveform of sound. When you use a phone, the variations in your voice are transformed by a microphone into similar variations in an electrical signal and carried down the line to the exchange.

Advantages of Analogue: Uses less bandwidth, More accurate, Disadvantages of Analogue, The effects of random noise can make signal loss and distortion impossible to recover.

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Analog communication systems, amplitude modulation (AM) radio being a typifying example, can inexpensively communicate a bandlimited analog signal from one location to another (point-to-point communication) or from one point to many (broadcast). Although it is not shown here, the coherent receiver provides the largest possible signal-to-noise ratio for the demodulated message. An analysis of this receiver thus indicates that some residual error will always be present in an analog system's output.

Although analog systems are less expensive in many cases than digital ones for the same application, digital systems offer much more efficiency, better performance, and much greater flexibility.

Efficiency: The Source Coding Theorem allows quantification of just how complex a given message source is and allows us to exploit that complexity by source coding (compression). In analog communication, the only parameters of interest are message bandwidth and amplitude. We cannot exploit signal structure to achieve a more efficient communication system.

Performance: Because of the Noisy Channel Coding Theorem, we have a specific criterion by which to formulate error-correcting codes that can bring us as close to error-free transmission as we might want. Even though we may send information by way of a noisy channel, digital schemes are capable of error-free transmission while analog ones cannot overcome channel disturbances; see this problem for a comparison.

Flexibility: Digital communication systems can transmit real-valued discrete-time signals, which could be analog ones obtained by analog-to-digital conversion, and symbolic-valued ones (computer data, for example). Any signal that can be transmitted by analog means can be sent by digital means, with the only issue being the number of bits used in A/D conversion (how accurately do we need to represent signal amplitude). Images can be sent by analog means (commercial television), but better communication performance occurs when we use digital systems (HDTV). In addition to digital communication's ability to transmit a wider variety of signals than analog systems, point-to-point digital systems can be organized into global (and beyond as well) systems that provide efficient and flexible information transmission. Computer networks, explored in the next section, are what we call such systems today. Even analog-based networks, such as the telephone system, employ modern computer networking ideas rather than the purely analog systems of the past.

Consequently, with the increased speed of digital computers, the development of increasingly efficient algorithms, and the ability to interconnect computers to form a communications infrastructure, digital communication is now the best choice for many situations.

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The article “Wireless networks” provides us the facility for application of wireless networks in telephony. Well, let us consider this side of getting convenience from the new state-of-the-art technology.

More and more wireless service providers are shifting from analog to digital. Even though analog technology was the foundation of many of today's large networks, newer more advanced digital networks are fast replacing it. Let us look at the reason behind this evolution/revolution. Many wireless service providers "upgrading" to digital networks citing (ссылаясь) the benefits that digital networks offer. Some of these advantages are better quality of service, more security and privacy for customers, and ability to support next-generation services. Next-generation services, which are the buzzword (модный термин) nowadays, include wireless Internet applications, voice/video conferencing etc.

Another reason is that a digital channel can cover a lot more transmissions than an analog channel, meaning an operator can fit more information into each transmission. The underlying implication is more return on investment. Digital networks enable service providers to give to their customers a whole compliment of additional services which include call waiting, voice mail, text messages, answering machines etc.

Digital networks do offer better sound quality but that comes with its limitations (mentioned later in the article). As far as security is concerned digital networks are a step ahead (немного впереди). Since digital networks scramble (шифруют, передают) transmissions into small burst there is less danger of scanning and cloning. Cloning can be termed as the cellular version of hacking. Cloning can be very disruptive/destructive if the account information falls into the wrong hands. Another thing is that digital transmissions consumer less battery power giving not only longer standby and talk times but also smaller, sleek (гладкий, приятный) looking battery packs and ultimately aesthetically better phones.

On the other hand we have analog networks. Other than the obvious advantages of digital networks mentioned above there are some features in analog networks that can counter the digital benefits. Starting from the basics, analog is cheaper. It is cheaper for the wireless service provider to install the systems and subsequently it is cheaper for the consumer to use it. Secondly digital mobile sets, because of their sleek looks and cutting edge technology, are expensive as compared to the analogs.

Roaming has always been a problem in the digital world as the industry standard has yet to become widespread. But as GSM has now become the worldwide standard, this problem has lost its teeth. One major advantage with analog is that they have already established huge networks. This gives greater accessibility to the customer, which is a great comparative advantage that the analogs have over digital networks.

Now let us look at the GSM (Global System for Mobile Communications) and see what it has to offer.

GSM gives its customers the latest, most advanced digital technology available in the market today. GSM offers a wider range of additional value added services which the analog-based technologies can never hope to offer. GSM simplifies data transmission between laptop and palmtop computers and allows them to be connected to GSM phones from where on the possibilities are end less. GSM provides integrated voice mail, high-speed data fax, paging and short message services capabilities.

GSM has the best security and privacy features available. GSM offers unrivaled call privacy and fraud prevention. In GSM networks, an encryption algorithm scrambles the digitized voice transmission between the handset and the GSM transmission site. This scrambles information is firstly hard to trace and secondly nearly impossible to unscramble without the encryption code stored in the smart card of the transmitting phone.

All GSM phones contain a SIM. The SIM (Subscriber Information Module) card - a.k.a. "smart card" holds All the phone settings, and the subscribers information, phone number, personal security key (PIN) and other data necessary for the handset to function. The greatest advantage of the SIM is that, since most service providers and mobile set manufacturers follow industry standards, it can be switched from phone set to phone set without any problem.

The SIM card also acts as a security device as it contains the decoding information necessary to decode the encrypted signals sent by the phone to the transmission tower. This makes it virtually impossible to scan or clone a GSM set. The SIM (smart card) is housed inside each handset, and is the brain of the set. It tells the set what to look for, where to look for it and what to do once the network is found. The SIM contains information about the service provider, the rate package, services features applicable and your personal information such as preferences, contact numbers, reminders etc.

Smart cards are available in two shapes. One is the chip itself which is currently being used by most mobile phone manufacturers or the bigger credit card style card. The larger card actually is a housing to hold the chip and goes directly into some sets. Other sets require that you remove the chip from the card and place it directly into the space provided inside the phone.

The biggest advantage of a GSM phone, in addition to the ones mentioned above, is national as well as international roaming. Since many wireless service providers are operating globally a GSM set registered in one country can be used any where in the world provided that the service provider has operations there or that the service provider has a contract with other service providers operating in the area to share customers.

As can be clearly seen, digital networks are the word of the day. GSM is taking over the cellular world and with the development of third generation GSM networks analogs will just have to go.