Communication in only one direction.
Head office sends sales advisors updates using pagers. Pagers can only receive data and cannot send data, therefore this is simplex communication.
A channel that can carry data in both directions but not at the same time.
When sales advisors are working in pairs going door to door they use walkie talkies to communicate with each other, this is half duplex communication.
This is when communication can take place in both directions at the same time.
Within the company e-mail is used as a communication tool. This is duplex communication.
This is when multiple bits of data are sent at once and each bit uses a separate wire. This is suitable for short distances.
Because parallel transmission is used within very short distances it would be used within the company’s computer system. E.g. buses.
Serial communication is when data is sent over a single wire and timing information is required. This is slower than parallel but is suited to long distances.
The company uses serial transmission to communicate with their brokers all around the world.
Situation Where Used
Explanation of Suitability
Thin wire coaxial cable
This is a copper based cable; there is a core of copper in the middle with a metal shielding and an outer sleeve, the metal shielding reduces interference. There are two types of coaxial cable, these are thick and thin wire. Thick wire is rigid and not easy to work with, this used to be used for large computing facilities (mainframes). The most commonly used wire now is thin coaxial, this wire is more flexible and easier to work with, and it is also cheap.
At the Head Office of the parent company, a minicomputer (installed in 1989) is still used for actuarial applications.
A minicomputer is a computer that is a multiprocessing system that can support up to 200 nodes simultaneously. This wire is suitable because the shielding and insulation keep electromagnetic interference to a minimum.
Unshielded Twisted Pair (UTP)
UTP consists of pairs of wires twisted around each other, there are six categories of UTP, the most commonly used being category 5 which can transmit up to 100Mbps. Because data is transmitted on pairs of wires there is less interference, this is because there is a signal transmitted on each of the wires and the signal retrieved is the difference, e.g. if one wire increased by 2V the other one will as well and therefore the difference will be the same and the data will not be affected. The disadvantage of UTP is that if there is a kink in the cable then the symmetry will be lost.
The main insurance office desktops are connected to the servers.
There is no heavy electronic equipment therefore it is not likely that there will be lots of crosstalk or interference, therefore UTP would be suitable.
Shielded Twisted Pair (STP)
The same as UTP but the wires are insulated; this prevents crosstalk or electromagnetic interference.
In the Post Room, heavy duty electronic processing equipment for mail sorting is installed and the desktops in this area are connected to the servers.
Because there is heavy duty electronic processing equipment in the post room it is appropriate to use STP as the shielding will reduce the amount of interference.
This is tiny strands of glass; a signal is transmitted as light through the glass. The strands of glass are coated which prevents interference (light escaping). Optical fibre can transmit up to 64 colours at one time; this means that 160Gbps can be transmitted. The main disadvantage of optical fibre is that it is very expensive.
The insurance company’s network has an optical fibre backbone.
The optical fibre backbone connects all devices and handles the major traffic. Optical fibre back bone is fast (up to 160Gbps) and effective because there is little to no interference.
Bluetooth uses a short range, low power radio frequency to connect devices wirelessly. The Bluetooth range is from 10 to 100 metres. It can only transmit 720Kbps which is a lot less than WiFi and therefore would not be able to be used as a replacement for WiFi.
The insurance mobile sales representatives synchronize their desktop and mobile phone calendars.
This would not involve large amounts of data transfer and therefore Bluetooth would be adequate for this job.
Microwave transmission uses satellites to transmit data. There is an uplink from a ground station to the satellite and then a downlink to another ground station. Compared to wire microwave can transmit large amounts of data over long distances. However line of sight is required. Microwave can be used as an alternative to glass fibre when it is not possible to lay wires.
The insurance company is connected to its brokers all over the UK.
Microwave is cheaper and easier than long distance optical fibre and although not as much data can be transmitted at once, it is adequate for what the insurance company needs.
WiFi stand for Wireless Fidelity. The purpose of WiFi is to connect devices to a network without the use of wires. There are currently three standards of WiFi being used, these are; 802.11a, 802.11b and 802.11g both 802.11b and g transmit data using the 2.4GHz range therefore they are compatible; the difference between them is that 802.11b transmits 11Mbps and 802.11g transmits 54Mbps. 802.11a transmits on a 5GHz range and therefore is not compatible with the other two standards, it also transmits 54Mbps.
Insurance mobile sales representatives connect their laptops to the office network.
If not transmitting large amounts of data, using WiFi is ideal as there is no hassle of connecting with wires. Users can also connect anywhere that is within range of the WiFi.
The insurance company are extending their premises and the engineers will need to install additional networking facilities for both desktops and laptops.
> There will be 300 employees using the extension, 200 of these will be using the extension five days a week between 9am and 5pm, 100 employees will be working mostly off site but will need to use the extension as and when needed. All users will need to access the company’s main network.
> Large amounts of data will need to be transmitted at high speeds (approximately 30Gbps).
> The extension is a permanent fixture to the company and will be used for the foreseeable future.
> There is no heavy duty electronic processing equipment so interference is not a major problem.
> Security is a concern.
Wired solution – UTP could be used. The advantages of using this are that it is used by lots of people and therefore it is cheap, it is also easy to terminate. If using category 5 up to 100Mbps can be transmitted. The disadvantages are that this type of wire is very noisy (leaks signal) and suffers from interference (allows signals to leak in). UTP would be a better choice than STP because it is not necessary to have extra shielding on the wires as there is no heavy duty electronic processing equipment to interfere with the signal. Although UTP is suitable for the job if small amounts of data were needed to be transmitted. However, UTP cannot transmit adequate amounts of data fast enough for this extension, therefore, the obvious choice would be to extend the company’s optical fibre backbone. Using optical fibre means that there is not a problem with interference (even if heavy duty equipment were needed in the future). Because the optical fibre allows 64 colours to be transmitted simultaneously up to 160Gbps can be transmitted which is sufficient for the needs of the company. The main disadvantage of using this solution is that it is very expensive compared to UTP; however, as this extension is a permanent fixture within the company it is worth investing in a solution that will serve the company’s requirements adequately.
Wireless solution – WiFi could be used. This would enable all the computers to be connected to the main network without the use of wires. The standard used for most WiFi connections is currently 802.11g which can transmit up to 54Mbps; there is however a new standard 802.11n which can transmit up to 300Mbps, it does this by using MIMO (Multiple Input Multiple Output) to improve system performance. This standard is currently only a draft standard and publication is not expected until September 2008. Even using the new standard this would not be suitable to use as a main solution as there is too much data to be transmitted and the WiFi solution would not be able to cope with the traffic. Another wireless solution that could be used which could cope with the traffic is microwave; this uses satellites to transmit data, the advantages of this are that large amounts of data can be transmitted over long distances but line of sight is required. Microwave is not used within LANs and unlike WiFi, does not connect an entire network. Microwave is usually only used as part of the network, the company already uses microwave in this way to connect to their brokers around the world.
Effectiveness of Wired and Wireless Solutions
> Both wired and wireless solutions allow sharing of resources, and connect systems together.
> Wired solutions are suitable for high volumes of traffic and generally have faster data rates than WiFi. Currently WiFi solutions can only transmit 54Mbps of data whereas wired solutions, depending on which one used, can transmit up to 160Gbps which is a considerable difference.
> There are few security concerns when using wired solutions, whereas many companies do not have secure wireless networks, this means that anyone can access confidential information.
> A major advantage of using wireless is that there are no wires to be installed and therefore can be used in less accessible areas or terrain where it is not possible to install wires. This also means that computers can be moved around easily and computers can be added to a network easily.
> When using a wireless network it is much easier to expand the network than it is when using a wired one.
> Wireless connection rates are not usually as fast as advertised. When speed is advertised as 54Mbps this is the maximum speed not actual speed. This is not the case when using wires.
> Wires are susceptible to crosstalk and interference, however if the correct wires are used for the workplace this would not be a major problem, e.g. STP in post room where interference is probable.
> Wireless solutions (such as satellites) are easier to use when transmitting data over very long distances.
> Wired networks are more established than wireless and are very reliable; therefore they tend to be more trusted than wireless.
Depending on the company situation and requirements depends on which solution is more effective. In this case it is more effective to use a wired solution (optical fibre) rather than a wireless one (WiFi). This is because:
> The company needs to transmit high volumes of data that the WiFi could not cope with, whereas optical fibre can.
> There will be 200 people using the extension at all times that will all need a reliable and fast network connection and a further 100 that will need the same when they are at the office. Optical fibre would be able to deal with this amount of traffic.
> This extension is a permanent fixture and is being used for the foreseeable future so there is no reason not to lay wires if it is possible to do so. If this were a temporary extension a wireless solution would be preferred as the company would not want the hassle of laying wires that are only going to be used temporarily.
> Wired solutions are more secure than wireless ones and as the company has stated that security is a concern a wired solution would meet their needs.
> Wired connections have a reliable and fast connection of a consistent quality, whereas the quality of a wireless connection varies.