Mobile communication methods

Core knowledge • international mobile equipment identity (IMEI) • cells, base stations, roaming • subscriber Identity Module (SIM), typical data stored in a SIM eg: • IMSI • PIN • PUK • SIM form factors eg: • mini-SIMs • micro-SIMs • nano-SIMs. Mobile standards and key features. Global System for Mobile (GSM/2G). General Packet Radio Service (GPRS/2.5G). Third Generation/3G. Fourth Generation/4G.

How do mobile phones work? A mobile phone is little more than a radio walky talky, In the most basic terms… Your phone connects to a mast using radio waves The radio mask connects to a physical connection (or satalite) The receiving radio mask is connected to a physical connection The receiving mobile phone is connected using radio waves

Makeup of a mobile phone Older mobile phones were actually more powerful. They are all esencally made up of the same components. A power source A CPU and software An areal A SIM which uniquely identifies the device

The problems with phones In order to remain portable, mobile phones need to have relatively compact antennas and use a small amount of power. This means that mobile phones can send a signal over only a very short range, just like a wakie-talkie.

The power of a cellular network Cellular netowrks allow people to connect over vast distances. You phone must only connect to the local mast in your area. This mast is then connected to the internet which allows you to connect over vast distances.

Cell site / cell tower A cell site is the site of an antennae and electronic communication. A typical mast will contain various communication devices. In GSM networks (Global System for Mobile Communications) the correct term is Bast Transceiver Station (BTS). There are issues surrounding BTS’ and in many locations they must be hidden or cannot be in close proximity to certain businesses as it may effect sensitive equipment (although there has yet to be a study which reports any negative effects of mobile phone masts on health. )

Mobile phone cells Mobile phone masts work in cells. Each cell knows the mobile phones that are within it. It keeps track of the phones within its cell. It uses the details found on your SIM card to uniquely identify your phone.

Cell Range The maximum distance between a phone and a mobile phone tower can be effected by many different factors. This can include… The technology used The power of the transmitter in the tower The size of the cell size The capacity of the network cell (how many phones it can keep track of) Sometimes mobile phone cells are deliberately set to a low power so that it doesn’t interfere with neighbouring cells. Trees or building interfere with transmission as well as any sources of electrical noise. A mobile phone’s range can be anything from up to 45 miles (rare) but is more likely to be anything up a maximum of 22 miles. Large distances are unlikely as the sensitive timing equipment required for transmission is likely to be out of date by the time the device receives the signal.

1G / 2G / 3G / 4G There are multiple phone technologies that work in parallel. As mobile phone networks increase their speed, generally the phone cells must be much smaller and their needs to be more of them. This is for two reasons. + There is likely to be more phones to keep track of + Data being sent faster is likely to contain more errors. 1G – Simple phone with no data (possibly analogue) 2G – Digital signals with speeds up to 250Kbps 3G – at least 200Kbps and up to 3Mbps 4G – up to 100Mbps and up to 1Gbps

Task – Find BTS Find 3 towers that work together. Create a document that details how these masks work in the following situation. A phone call between two people who re within range of the same mast A phone call between two people who are within range of different masts A phone call between one perdon who is static and another who moves from mast to mast A phone call from a person on the extreme range of one of the masts to a person within range of that same mast www.cellmapper.ne

SIM cards There are various types of SIM cards. They all perform the same function but come in different sizes. These include

Subscriber identify module This SIM is a small integrated circuit that is intended to securely store the IMSI number and its related key. It is used to authenticate and identify a device on the network. Most SIM cards also allow you to stare data on the SIM card such as contact details although this is less commonly used.

international mobile equipment identity (IMEI) An IMEI is a 15-17 digit code that uniquely identified a mobile phone. This data is not part of the SIM. If you change the SIM the IMEI will stay the same. To find your IMEI type in *#06# It can also be found in the battery compartment of your mobile phone. It can be used to blacklist your phone if it is stolen. This is generally done by calling your service provider. If this is done the phone effectively becomes useless.

PIN Mobile phones can allow for them only to work if the correct PIN has been entered. If the wrong PIN is entered then they will be blocked and will required the PUK code.

PUK If a SIM card is locked you will require an 8 diick PUK code to unlock it. A PUK cocde is a Personal Unlocking Key. Typically you will only need a PUK code when you SIM PIN has been entered incorrectly

IMSI International mobile subscriber identity The IMSI a 64 bit code that is used to identify a particular mobile phone mast mast. It is the code that mobile networks use to identify you on a network and is used to look up which network you belong to . An IMSI- Catcher is a device for eaves dropping or intercepting mobile phone signals. Essentially it is a fake mobile phone mast which a person connects to. Obviously mobile phone companies are not keen for you to find the IMSI codes these are closely guarded (rarely sent out unencrypted).