Interfaces BY B S S Rao SDE GSM Faculty
Sep 12, 2015
InterfacesBYB S S RaoSDE GSM Faculty
Physical ChannelThis is the medium over which the information is carried.
Logical ChannelsThe logical channels consist of the information carried over the physical channel.
Types of Logical ChannelsTraffic ChannelsControl Channels
Traffic ChannelThese Channels carries speech or data information.Full Rate Channel Speech ( 13 Kbps net , 22.8Kbps gross). Half Rate Channel Speech ( 12.2 Kbps/net , 22.8Kbps gross)
Control Channel GroupsBCCH GroupCCCH GroupDCCH Group
BCCH GroupAll BCCH Channels are in downlink onlySCH carries information for frame synchronizationFCCH provides information for carrier synchronization.
BCCHThis channel carries the following information:Location area identityCell identityDTX permittedList of frequencies used in Cell etc.
FCCHFrequency correction channelThis allows the mobile to synchronize its own frequency to that of transmitting BTS
SCHSCH Carries the following info. Frame Number Base station identity code (BSIC)This allows the MS to synchronize to the TDMA frame
CCCHThe Common Control Channel Group works in U/L & D/L
RACH (Random Access Channel)PCH (Paging Channel)CBCH ( Cell Broadcast Channel)
RACHRACH is used by MSs to gain access to the System
PCHPCH is used by the System to call MS
CBCHCBCH is used to transmit messages to be broadcasted to all MSs within Cell. For example., road traffic information , sporting results.
AGCHAccess Grant ChannelThis is used in DownlinkThis is used to assign resources to the MS., such as SDCCH
DCCHDedicated Control Channels.This Group consists of SDCCH , ACCH ( SACCH and FACCH)
SDCCHThis supports the transfer of data to and from MS during call set up and validation.
SACCHSlow associated control channelThis is used for radio link measurement and power control messages.
FACCHFACCH is used to pass event type messages for example Handover Messages
FACCH & SACCHBoth channels are operated in U/L & D/L
Channel combinations and Time Slots
Channel CombinationTim e slotsTrafficAny Time slotBroadcast0,2,4,6 ( 0 first)DedicatedAny Time slotCombined0 only
Channel CombinationChannelsTrafficTCHBroadcastBCCH + CCCHDedicatedDCCHCombinedBCCH + CCCH + SDCCH + SACCH
THANK YOU ALL