LTE Channels

Below are the three types of Channels available in LTE.

LTE Logical Channels :

·??????? Broadcast Control Channel (BCCH): Used for broadcasting system information.

·??????? Paging Control Channel (PCCH): Used for paging.

·??????? Common Control Channel (CCCH): Used when UE is not having RRC connection with the network for sending MSG3

·??????? Multicast Control Channel (MCCH): Used for transmitting MBMS scheduling and control information from the network to the UE.

·??????? Dedicated Control Channel (DCCH): Used to transmit/receive dedicated control information with a UE.

·??????? Dedicated Traffic Channel (DTCH): Used to transmit/receive dedicated traffic with a UE.

·??????? Multicast Traffic Channel (MTCH): Used for transmitting MBMS traffic data from the network to the UE.

LTE Transport Channels :

·??????? Broadcast Channel (BCH): This is a fixed bit rate DL channel mapped to BCCH logical channel and This is broadcast in entire cell and MIB.

·??????? Downlink Shared Channel (DL-SCH): This is a DL channel used to transfer user data, HARQ and link adaptation are used by varying the modulation, coding and transmit power.

·??????? Paging Channel (PCH): This is a DL channel that is broadcasted in the entire cell and carries paging.

·??????? Multicast channel (MCH): This is a DL channel and used as separate transport channel for multicast (MBMS).

·??????? Uplink Shared channel (UL-SCH): This is a DL channel used to transfer user data, HARQ and link adaptation are used by varying the modulation, coding and transmit power.

·??????? Random Access Channel (RACH): This is UL channel and is not mapped to any logical channel, It is used to achieve UP link synchronization between UE and eNB to transmit information needed to obtain scheduling grants. ?

LTE Physical Channels:

·??????? Primary Synchronization Signal (PSS): This is a downlink signal used for radio frame synchronization, it is made up of 62 Zad Off CHU sequence and is transmitted in last symbol of subframe 0 and 5 of every frame.

·??????? Secondary Synchronization Signal (SSS): This is a downlink signal used for radio frame synchronization, it is made up of 62 Scrambling Sequence (based on m-sequence), It is transmitted in second last symbol of subframe 0 and 5 of every frame and is used to identify cell group identity.

·??????? Reference Signal (RS): This is a downlink signal and is transmitted by eNB for coherent demodulation at the UE side and to estimate the CQI.

·??????? Physical Broadcast Channel (PBCH): This is a downlink channel and is used to transmit system information.

·??????? Physical Multicast Channel (PMCH): This is a downlink channel used for transmission of multicast information, its format is similar to the PDSCH but it is used for reception by UE’s.

·??????? ?Physical Downlink Shared Channel (PDSCH): This is a downlink channel and is used to carry user data from eNB to UE.

·??????? Physical Control Format Indicator Channel (PCFICH): This is a downlink channel and is used It carries the number of symbols that can be used for control channels (PDCCH and PHICH).

·??????? Physical Downlink Control Channel (PDCCH): This is a downlink channel and carries the control information about the data being transmitted on the current subframe, PDCCH carry DCI (Downlink Control Information) which includes resource assignments for a UE or group of UE's and information about UL resources.

·??????? Physical Hybrid Indicator Channel (PHICH): This is a downlink channel and is used for sending the feedback of uplink data received on PUSCH. ?

·??????? Physical Uplink Shared channel (PUSCH): This is an uplink channel used to transfer user data and control information (using UCI) and when there is no PUSCH then UCI is transmitted on PUCCH.

·??????? Physical Uplink Control Channel (PUCCH): This is an uplink physical channel and is used to carry control information from UE for which no PUSCH resource is granted in the same subframe. For a UE already granted a PUSCH, control signaling is multiplexed with data onto PUSCH.

·??????? Sounding Reference Signal (SRS): This is an uplink reference signal which helps for eNB to figure out the channel quality of uplink path.

·??????? Physical Random-Access Channel (PRACH): This is an uplink channel and is used to carry RACH request to request an uplink allocation from eNB.

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