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Communication Technology

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Introduction

Communications Technology Assignment 1 5 April 2003 Write a report on the initial stages in designing a network The following are the definitions including diagrams of the types of topology that can be used to create a network within a business; The shape of a local-area network (LAN) can be varied depending on the required use! These network topologies can be either physical or logical. The type of networks that I will be discussing here are all physical, as they require different methods of physical connections using cable. There are four main topologies used in LAN's Bus All devices are connected to a central cable, called the bus or backbone. Bus networks are relatively inexpensive and easy to install for small networks. Ethernet systems use a bus topology. Advantages Disadvantages Cheap Possible 'collisions' Easy to Install Ring All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Ring topologies are relatively expensive and difficult to install, but they offer high bandwidth and can span large distances. Advantages Disadvantages Wide connection Expensive High bandwidth Difficult to install Star All devices are connected to a central hub. Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub. Advantages Disadvantages Cheap to maintain Possible 'bottlenecks' Easy to Install Tree (Hierarchical) ...read more.

Middle

It is very easy to install, which is one of the main factors to why it is cheap overall. However, because of the outer copper jacket in the cable the electrical materials must be kept grounded or poor signals will occur. For this reason Coaxial is not used very much in networks! The difference between Thicknet and Thinnet is that Thicknet is physically larger and thicker in shape than Thinnet. This can enable larger amounts of copper wire to pass through the coaxial cable. Coaxial cable consists of a hollow outer cylinder that surrounds a single inner wire made of copper for the centre and a metallic foil to cover and act as a shield to prevent outside interference. Main Uses TV Aerial signals Fibre optical cable This medium is capable of conducting modulated light signals. But with this relatively new technology comes the extra cost, in both installation and maintenance. This form of cable is by far the most efficient as it cannot lose signal strength as it doesn't consist of electrical transmissions; instead the signals are sent in bits and converted into beams of light. This form isn't considered as wireless as light fibres are still needed to guide the transmissions. Main Uses Digital sounds Telephone Companies Science behind the transmission of data across different types of network Analogue Signals - The principal feature of analogue signals is that they are continuous. Signal transmission over wires or through the air in which information is conveyed through variation of some combination of signal amplitude, frequency and phase. ...read more.

Conclusion

Manchester encoding is a digital coding scheme, used by such standards as IEEE 802.3 and Ethernet. The encoding is used and a 1 is denoted by a high level during the first half of the bit time. Manchester encoding is more immune to noise and is better at remaining synchronized. In Manchester encoding the voltage that is on the copper wire or whatever form it is, has the bits encoded as transitions. Non return to zero (NRZ) - These signals maintain constant voltage levels with no signal transitions (no return to a zero-voltage level) during a bit interval. However, Non return to zero inverted (NRZI) signals maintain constant voltage levels with no signal transitions (no return to a zero-voltage level), which is the same but interpret the presence of data at the beginning of a bit interval as a signal transition and the absence of data as no transition. Discuss the following encoding and definitions Amplitude Modulation - The amplitude is the maximum value of an analogue or a digital waveform. This is normally seen on a graph and can be identified as the distance the line is compared from one point to another. This modulation technique is where information is conveyed through the amplitude of the carrier signal. Frequency Modulation - This is the modulation technique in which signals of different frequencies represent different data values. Phase Modulation - Process by which the characteristics of electrical signals are transformed to represent information. As the name suggests the phase, or beginning and ending points of the wave is varied to carry the message ?? ?? ?? ?? Unit 5 Sam McCullough ...read more.

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