Signal Theory Essay Example for Free

Signal Theory Essay In this assignment I am going to describes different types of communication devices. For example Switches, Routers, etc. Then I am going to explain the principles of signal theory. After this I will look at In Manchester encoding the signal synchronizes itself. This is an advantage because this will decrease the error rate and optimize the reliability. But on the other hand it is also a disadvantage because the amount of bits sent in the original signal when transmitted has be twice the amount of bits from the original signal. Differential Manchester Also known as Conditioned Diphase (CDP). It is a encoding method which uses data and clock signal as fused to create a self-synchronizing data steam. Similar to Manchester encoding it uses present or absent transitions to represent logical value. Made from Copper, PVC, Plastic Length:100 M Speed:100 Gbit/s Extremely fast and less interference Incredibly expensive and mostly likely be manufactured till 2013 Bluetooth Mostly Copper for the circuitry, Plastic for casing. Length: 100 M Speed:1 Gbit/s Send from cell phones, do not need wires to connect, Most of the phone are equipped with it Open and other people can access your phone if not protected. Quite slow when sending and receiving on a cell phone. Infrared Receiver, Antenna and Transmitter, Copper Plastic Length: 40 km Speed: 4 Mbit/s Shorter wave than microwaves, not as harmful. Less interference. Microwaves Antenna Receiver. Length: 1 M Speed: 300 GHz Good for sending data over longer distances Dangerous, if something that uses microwaves e. g. cell phone for too long. Too much interference Wi-Fi Wi-Fi Signal Transmitter. Length: 95 M Speed: 5 GHz Usable anywhere in the house, can even be used as a hotspot in public places e. g. airports, cafi , etc Other people can also access it so many connections can make it slow. Satellite Dish and a satellite in orbit Length: 22,000 Miles Speed: 40 Mbit/s Connection from anywhere in the world. Delay of up to 500 millisecond due to rain or moisture. Fibre Optic LED/Laser Connector. Glass, Plastic, PVC. Length: 40,000 Speed: 10 Gbit/s Extremely fast speeds can be achieved without the use of switches, hubs, etc over long distances Simply expensive to buy. Radio Transmitter Receiver Length: 100 Miles Speed: 300 GHz Available anywhere in the world. Very limited range and gets easily affected by interference. Name Specification Advantages Disadvantages Coaxial Diameter: 6 mm / Resistance: 85. 2 km Capacity: 70 km at 1KHz Cheap. 500 meters length. It very reliable Expensive and hard to install Fibre Optic Diameter: 2 microns. Good for transmission over long distance because it is immune to magnetic interference. Electrical interference protected. Stretches up to 3000 meters. No noise is generated Very expensive and over time the sent signal will get weaker because of signal reflecting. UTP/Cat. 5 Foiled and uses copper wire. Stretches up to 100 meters. Easy installation and transmission rates reaching up to 1 Gbps. Very open to interferences. STP Foiled and also uses copper wire. Shielded. Length up to 100 meters. Transmission rates between 10-100 Mbps Expensive heavy and big in physical size. Radio Uses antenna to transmit. Signal can be refracted. No wires needed and very long distances capable. Signal gets weaker the more time taken to reach the destination. Security is a problem very open for hackers. LAN This is type of network which covers a small office, home or a school network. A LAN uses either wired Ethernet or wireless RF technology. Using a LAN can be much easier when there is a printer available or sharing a file throughout the network. Updating software is much easier because updating software will automatically update all the other softwares. LAN has much higher transmission rates because it is wired connection rather than wireless. Ethernet and Wi-Fi as most widely used technologies, however many others such as token rings have been used before. This relates to standard IEEE 802. 2. This standard allows two connectionless and one connection orientated operational mode: Type 1 which allows frames to be sent to a single destination or multiple destinations on the same network is a connectionless mode. Type 2 is the oriented operational connection mode. In this mode it uses something called sequence numbering which makes sure that when the data is send it gets to the destination in the correct order and not a single frame has been lost. Type 3 which is also a connectionless service, but only support point to point communication. Infrared is related to this service because in computer infrared network it can receive and transmit data either through the side of the device or the rear side of the device. When connections are made using Microsoft Windows Infrared the same method used for LAN connections can be used. Infrared technology has been extended to allow more than two computers to be connected semi permanent networks. The advantage of a LAN is that the same physical communication path can be shared by multiple devices. For example it there is a printer, a computer and the internet connection the LAN will allow connections to the printer and it will also allow connections to the internet. If a software is loaded onto the file server that all the computers on the network can use it. There are quite a few drawbacks of a LAN network. For example security measures need to be taken so that users cannot access unauthorised areas. It is quite hard to setup the network. Skilled technicians are needed to maintain the network. Yet the biggest disadvantage is that if the file server goes down than all the other computers on the network are affected as well. WAN This type of network covers a wider area. It is used over high speed, long distance communications such as computers in two different areas. A WAN can also be shared. For example two occupants in two buildings can share the wireless connection to a third person, or a business or anyone or anything they wish to do so. Data is safe, secure and quick when it is transmitted between two computers. WAN can also be used to connect different types of networks together for example a WAN network connected to a LAN networks. The reason behind this is that it is AppleTalk. It is a cheap LAN architecture which is a standard model built for all Apple Macintosh computers and laser printers. It also supports Apple LocalTalk cabling scheme as well as Ethernet and IBM token ring. AppleTalk can connect to standard computers which do not have AppleTalk. This all relates to FDDI standard which stands for Fibre Distributed Data Interface. It is a backbone of a wide area network. It uses fibre optic cable to transmit data up to supported rate of 100 Mbps. An advantage of a WAN it allows secure and fast transmission between two computers. Data transmission is inexpensive and reliable. Sharing a connection is easy as well because it allows direct connectivity. A WAN also allows sharing of software and resources to other workstations connected on the network. Disadvantage of a WAN network is that the signal strong all the time so anyone trying to hitchhike a connection can use the WAN connection it is not protected. WAN are slow and expensive to set-up. They also need a good firewall to stop intruders using the connection. Networking Mediums Different types of medium are used for different types of topologies. Coaxial Cable It is normally used to connect telecommunication devices which used for broadband connection which use high transmission rates to transfer data. The cable is insulated using a braided shield which is also known as a screen. It protects the cable from electromagnetic interference. It has higher capacity than a standard copper wire. Therefore it allows radio frequencies and television signals to be transmitted. Various types of coaxial cables are available which can be used for thin Ethernet which are used for networking 10Mbps connections lengthening up to 200 meters. There is also thick Ethernet cable is also used for 10Mbps connections but stretching up to 500 meters. Unshielded Twisted Pair (UTP) coaxial cable has been used in the past when building networking using thick or thin Ethernet. Ethernet cables quite expensive but they are still used because they carry more data then a telephone wire and it is less susceptible to interference. Optical Fibre Optical fibre also known as a fibre optic cable uses light to transmit data. Light is made using a laser or LED is sent down a fibre which is thin strand of glass. Fibre optic is about 2 microns in diameter which is 15 times thinner than a single human hair. Optic fibre is not affected by electromagnetic interference. It is cable of higher than data transmission rates, ideal for broadband usage. Fibre optics are manufactured in two different types the single mode and multi mode. The difference between the two is quite obvious single mode uses one beam of light to transmit data to longer distance of around 3 km but the multimode uses multiple beams of light to transmit data but only to shorter distance of 2 km. This allows more data to be sent simultaneously. It is normally used for broadband transmission as mentioned before because it is faster at transmission than any other cable currently available. Fibre optic also has an advantage of long distance transmission because light propagates through the fibre with little attenuation compared to electric cables. Not many repeaters are needed for long distance. Data travelling using the fibre can reach rates of unto 111 Gbps. Fibre optics also restrict high voltages travelling from end to end of a fibre to another end. It also restricts cross talk and environmental noise between signals transmitting to different cables. UTP (Unshielded Twisted Pair) STP (Shielded Twisted Pair) UTP and STP both use copper wires which are known to man as one of the oldest types of transmission media methods. STP is insulated with a metallic plastic foil which is all under the plastic sheath. This insulating is expensive to make thats why it is more expensive than normal cable. Even though STP cable is shielded there is still crosstalk. It cannot be eliminated. Both UTP STP individual wires are twisted together so it creates there is less crosstalk. Core of each of the type of cable is a very good conductor and easy to work with. Media which can be used with UTP is internet, because it is easy to install, maintain, less expensive and allows higher transmission rates. The media used with STP is also internet, but it is more expensive and difficult to install. The advantage is that there is less interference. It is difficult to install because it has to be grounded at both ends. Improper grounding will result I metallic shielding acting as a antenna and it will pick up unwanted signals. Due to the cost and difficult to install and maintain it is hardly used in Ethernet networks. It is mainly used in Europe. Crosstalk Crosstalk means that signal that are transmitting in different circuits interfering with each other. Crosstalk happens because unwanted signals interfere with another channel transmitting undesirably. Electrical Noise Noise is when an electrical signal is transmitted across a wire which is not the sent signal by the user, but it is another signal which has been picked up randomly. Twisted pair cables eliminate the interference because they are twisted with each other so they cancel out each other. The thickness and varied insulation of a cable and its capacitance of the wires will cause noise. For example when there is communication on a telephone and either person cannot hear the message clearly this is caused by noise affecting the signal. This is known as crosstalk, as mentioned before crosstalk is when signal is affected by electromagnetic field around a wire. Electric noise cannot be eliminated but can be minimized by taking caution. Keep cables away from electrical equipments and shield the cable weather it is a fibre optic or a STP. Checksum It is a method used for error-checking the received data against a calculated checksum. For example when a data is received by the designated node the checksum error detection method will create a new calculation and check it against the old calculation to check weather the same result it received. This makes sure the data has not been altered in any way when it was transmitting.