Mobile Communication Systems PDF

Mobile communication systems What are mobile networks? A mobile network also called a cellular network is a wireless WAN that uses radio waves to transmit and receive communications from portable devices such as smartphones. What are cellular networks? cellular network is a wireless WAN...

Mobile communication systems What are mobile networks? A mobile network also called a cellular network is a wireless WAN that uses radio waves to transmit and receive communications from portable devices such as smartphones. What are cellular networks? cellular network is a wireless WAN that uses radio waves to transmit and receive communications from portable devices such as smartphones. What is the structure of a cellular network? Base stations (in a cell/cellular subsystem) for (wireless) connection to end user Core/central switched network for handling voice calls/text messages Packet switched network for handling (mobile) data/internet traffic Public switched telecommunications/telephone network for connection into the global telephone networks What are characteristics of mobile networks? Mobile networks are broken down into small areas called cells which is the geographical area covered by a radio transmitter. At the heart of each cell is a radio base station that transmits and receives messages. The base stations connection to public telecommunication services allowing access to the internet. There have been several generation of mobile networks each providing faster access speeds and greater reliability. (1G, 2G, 3G, 4G, 5G) 1G: first generation of mobile networks uses analogue signals. It’s also largely limited to voice and text message communications 2G: second gen which uses digital transmission, improving signal quality. It is able to connect with each other, allowing a phone to use other networks. What are characteristics of mobile networks? 3G: it increased data transmission speeds up to to 2 Mbps, allowing mobile internet access, video transmission and online gaming. 4G: allows data transmission speeds of up to 1Gbps, allowing greater use of high quality video streaming facilities and advanced mobile services and online gaming. 5G: latest generation offering the fastest and most reliable connections available. It supports technologies like augmented reality, virtual reality and the internet of things (IoT). They have tested speeds up to 1.5 Gbps at present but could be even faster. Very large capacity for connection of devices/up to a million devices per km2. Very high bandwidth for transferring data between multiple devices. Very low latency in the connections for fast/instant responses. Seamless handover between base stations. Use of ‘beam-forming’ techniques (by base stations) to direct signal/improve connections to (specific) devices. What are the uses of mobile networks? Individuals use mobile networks to enable them to use their computing, devices away from a fixed point. Users can make voice calls, exchange data, use social media, connect into their employer networks and access the internet while moving, around. A user can walk around cities or travel in cars, trains or buses between cities and still be able to access internet services and voice calls because base stations and devices automatically hand over connections from one to the next. Customers can receive updates on delivery times from drivers of delivery vehicles and the vehicles can be tracked by the owners of the delivery company. Satellite navigation systems in vehicles that use GPS to locate What are the uses of mobile networks? (continued) The traffic information is transmitted over data connections on the mobile network and is received by the satellite navigation device either by using its own connection (SIM) card or by a Bluetooth connection to a smartphone. By combining the GPS travel route information with the traffic and weather reports, alternative routes can be calculated automatically or the driver can be shown a choice of routes. What are protocols used in mobile networks? General packet radio services (GPRS) Second (2G) and third (3G) generation mobile networks use general packet radio services (GPRS), a wireless technology, to send data in packets. GPRS can provide data transfer speeds of up to 114 kbps, but the speeds are dependent on the amount of network traffic. If the amount of traffic on the network increases, speeds drop considerably due to congestion. Internet Protocols (IP) Fourth (4G) and fifth (5G) generation mobile networks use Internet Protocols (IP) to transfer data. What are advantages of mobile networks? Mobile networks have enabled users to communicate with others and access the internet while on the move, often through the use of smartphones. Breaking the network down into cells allows for lower power radio transmitters to be used, bringing energy and cost savings. There are only so many radio frequencies that can be used for mobile communications. These frequencies can be split among neighboring cells and reused in more distant cells, thereby increasing the number of communications that can take place at the same time. Larger geographical areas can be covered than by using a single transmitter. Even high power transmitters are limited in range. By using several low power transmitters, a wider area can be covered. What are disadvantages of mobile networks? Quality of reception can vary and can be poor towards the edge of a cell, leading to interrupted or delayed transmissions. The use of frequency must be carefully planned to avoid interference between cells. The technology for 5G technology is limited at present and it could take a while and be costly to make the technology full usable. Explain how cellular networks allow large numbers of mobile (cell) phones to connect without interference from other mobile (cell) phones? (sample question) Connections use (frequency/time/code) multiplex division to share frequencies Spread spectrum technology is used to allow multiple connections on same (set of) frequencies Multiple input and multiple output(MIMO) using multiple transmit/receive antenna to increase capacity/use of transmission channels/increased data flow Antennae from base stations/towers can be/are directional to avoid interference from other towers/reflections Adjacent cells use different frequencies from neighboring cells Connection/wireless frequencies are reused by cells distant from each other to increase capacity (where ranges of frequencies are limited) Explain how 4G cellular networks provide a better service than 3G networks for smartphone users accessing internet services. (sample question) Increased rate of data transfer/higher bandwidth Provides faster download/more buffering capacity/less waiting for data to download Web pages/content loads faster Due to use of higher range of frequencies Due to use of Multiple input and multiple output (MIMO) using multiple transmit/receive antenna to increase capacity/use of transmission channels Connections use (frequency/time/code) multiplex division to share Explain how 4G cellular networks provide a better service than 3G networks for smartphone users accessing internet services. (sample question) (continued) Due to use of spread spectrum technology to allow multiple connections on same (set of) frequencies Handovers between base stations are ‘smoother’/less subject to interruptions/loss of connection Use (only) packet switching technology instead of circuit switching (as in 3G) so IP packets can be carried/based on IP packet switched technology Packet switching allows data/voice packets to be multiplexed/interleaved with other packets (give increased rates of data flow)