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

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