Mobile Cellular Networks Cellular principle –Taking this one step further tessellate network coverage area with cell reuse pattern (cluster) Each cell in cluster operates on a different frequency Cluster sizes of 4,7,9 etc are common Result - increase in capacity of network in terms of max number of simultaneous calls the network can support

Mobile Cellular Networks Cellular principle –Cells are hexagonal shape –Base station located in middle –Radius of cell is governed by power of Base Station –Increasing the power increases geographical size of cell –Smaller sizes automatically increase the network capacity but can also increase interference

Mobile Cellular Networks

Cellular principle –Trend is to have sophisticated cell structures essentially overlay large cells on smaller cells –Common cell sizes Pico cells –floor of a building –a few metres Micro cells –Street – metres –Base station mounted below roof level –Street canyons Macro cells –5 kms –special masts erected for Base station –Pico cells give large capacity for a small area –Macro cells give small capacity for a large area

Mobile Cellular Networks Network Components –Mobile Station Mobile Equipment (e.g. phone) –antenna Subscriber Identity Module (SIM) –Smart card –SIM must be inserted into ME before ME will work –Essentially personalises ME –Contains subscription information –Other information - subscriber’s short dialing codes –Can make emergency codes Future is multi-media mobile stations

Mobile Cellular Networks Network Components –Base Station System Base Transceiver Station –Antenna –Interfaces to MS –Able to transmit /receive signals on many channels simultaneously Base Station Controller –Controls a number of Base Transceiver Stations –Essentially a concentrator (multiplexer) Multiplexes Base Transceiver Stations onto high speed link –Undertakes some radio management tasks passes Location Area Code to Base Transceiver Station for broadcasting to MSs – Also translates 13kbps speech from radio channels to 64Kbps PCM for transmission on fixed network

Mobile Cellular Networks Network Components –Mobile Switching Centre (MSC) ISDN switch enhanced to operate in mobile network In addition to switching –manages calls for all MSs within its domain Billing Handover Authentication

Mobile Cellular Networks Network Components –‘Intelligence’ (databases) in Network Home Location Register (HLR) –One logical HLR in network –Contains an entry for every subscriber –Stores fairly static information about subscriber services subscribed to –But also location information to allow mobility Location Area Code where MS is currently operating

Mobile Cellular Networks Network Components –‘Intelligence’ (databases) in Network Visitor Location Register (VLR) –One VLR for every Location Area in network –Typically an Mobile Switching Centre ‘covers’ a location area In this instance VLR is integrated with MSC –VLR contains information on every subscriber (visitor) currently operating in the domain of VLR –Entries are added when visitors enter VLR domain –Entries are deleted when visitors leave VLR domain HLR and VLR jointly facilitate mobility

Mobile Cellular Networks