mounir34
2017-06-11, 03:34 AM
dear
find below small description about LTE Channel,
LTE Channel Dimensioning is one of the most important subjects during LTE Network design, Rollout and optimization phases.
Along with data a large number of other information is sent, which becomes the overhead to the data being sent, effecting the user perception and throughput. This overhead information is mostly the control information, which can be dimension-ed in to occupy less number of LTE RE Symbols , resulting in more user data transfer per user per TTI, or more control information can be sent, resulting in less user data transfer per user per TTI.
The decision to send more or less control information depends upon the radio conditions ,network plan and priorities set by the operator based on different radio conditions. In this article We will discuss DL channels in Detail
LTE Technology has the following channels in Downlink and Uplink.
(DL) Downlink Channels:
PBCCH
PHICH
PCFICH
PDCCH
PDSCH
PBCCH:
======
Physical Boradcast channel comprises of MIB ( Master Information Block) and is carried in the centre of the bandwidth, occupying 4 symbols of slot 1, of radio frame, transmitted over 4 radio frames, with a total duration of 40msecs. Once the UE synchronizes with the CELL, it reads MIB. MIB carries information about system Bandwidth, PHICH Configuration Ng and SFN. Based on MIB the UE is able to decode PCFICH, which inform UE about the control Region.
PCFICH Channel:
==============
PCFICH Channel is used to inform the UE about the number of OFDM symbols used by PDCCH in a subframe.
PCFICH occupies 4REGs , which are distributed over channel bandwidth, the location depends upon System Bandwidth and Ncell-ID. PCFICH carries CFI(control Format Indicator) codewords, which can change every TTI ms.
PHICH Channel :
==============
PHICH channel is used to Carry Ack/Nack( Hybrid ARQ data) , the information is carried in the form of PHICH groups with each group carrying 8 ACk/NACK processes at max. PHICH carries ACK/NACK in response to the ULSCH transmissions. PHICH occupies 1st symbol of every subframe, it occupies 3REG equivalent to 12 REs. Each PHICH within a PHICH is orthogonally separated.
Two frame formats are present for PHICH
Frame Format 1: The number of PHICH are fixed and donot change
Frame Format2: The number of PHICH groups may change as per requirement of ACK/NACK process
PDCCH Channel:
==============
Physical Downlink control Channel, carries control information(DCI) like scheduling and other control information. Its area is given by PCFICH. The size of downlink control information can vary per subframe. PDCCH is carried over a number of consecutive Control Channel Elements (CCEs). Each CCE is composed of 9 REGs or 9X4=36 REs(Resource Elements)
PDCCH Carries the following control information:
Downlink Grant
It contains
(a) PDSCH Resource Indicator
(b) Modulation and Coding Scheme
(c) HARQ info
(d) PUCCH PC commands
1, 1A, 1B, 1C, 1D, 2, and 2A are the formats of this DCI
Uplink Grant:
It Contains
(a) PUSCH resource indicator
(b) MSC and HARQ info
(c) PUSCH Power control commands
It has format Zero only.
Power Control Command:
it contains
(a) PUSCH Power control Commands for UE
It has format 3 and 3A
If the number of REG not assigned to PHICH or PFICH is Nreg, then the CCE available in the system are number as , 0 …. Ncce-1, where Ncce= Nreg/9
The PDCCH support multiple formats
Format 0: Contains 1 CCE
Format 1: Contains 2 CCE
Format 2: Contains 4 CCE
format 3: Contains 8 CCE
Each CCE carries UL or DL scheduling Control information for one C-RNTI/MAC. It is encoded with CRC.
.
PDSCH:
======
PDSCH carries a of PCH and and DL-SCH, This Channel is the actual medium where everything/user data is carried, after other control channels a transmitted.
find below small description about LTE Channel,
LTE Channel Dimensioning is one of the most important subjects during LTE Network design, Rollout and optimization phases.
Along with data a large number of other information is sent, which becomes the overhead to the data being sent, effecting the user perception and throughput. This overhead information is mostly the control information, which can be dimension-ed in to occupy less number of LTE RE Symbols , resulting in more user data transfer per user per TTI, or more control information can be sent, resulting in less user data transfer per user per TTI.
The decision to send more or less control information depends upon the radio conditions ,network plan and priorities set by the operator based on different radio conditions. In this article We will discuss DL channels in Detail
LTE Technology has the following channels in Downlink and Uplink.
(DL) Downlink Channels:
PBCCH
PHICH
PCFICH
PDCCH
PDSCH
PBCCH:
======
Physical Boradcast channel comprises of MIB ( Master Information Block) and is carried in the centre of the bandwidth, occupying 4 symbols of slot 1, of radio frame, transmitted over 4 radio frames, with a total duration of 40msecs. Once the UE synchronizes with the CELL, it reads MIB. MIB carries information about system Bandwidth, PHICH Configuration Ng and SFN. Based on MIB the UE is able to decode PCFICH, which inform UE about the control Region.
PCFICH Channel:
==============
PCFICH Channel is used to inform the UE about the number of OFDM symbols used by PDCCH in a subframe.
PCFICH occupies 4REGs , which are distributed over channel bandwidth, the location depends upon System Bandwidth and Ncell-ID. PCFICH carries CFI(control Format Indicator) codewords, which can change every TTI ms.
PHICH Channel :
==============
PHICH channel is used to Carry Ack/Nack( Hybrid ARQ data) , the information is carried in the form of PHICH groups with each group carrying 8 ACk/NACK processes at max. PHICH carries ACK/NACK in response to the ULSCH transmissions. PHICH occupies 1st symbol of every subframe, it occupies 3REG equivalent to 12 REs. Each PHICH within a PHICH is orthogonally separated.
Two frame formats are present for PHICH
Frame Format 1: The number of PHICH are fixed and donot change
Frame Format2: The number of PHICH groups may change as per requirement of ACK/NACK process
PDCCH Channel:
==============
Physical Downlink control Channel, carries control information(DCI) like scheduling and other control information. Its area is given by PCFICH. The size of downlink control information can vary per subframe. PDCCH is carried over a number of consecutive Control Channel Elements (CCEs). Each CCE is composed of 9 REGs or 9X4=36 REs(Resource Elements)
PDCCH Carries the following control information:
Downlink Grant
It contains
(a) PDSCH Resource Indicator
(b) Modulation and Coding Scheme
(c) HARQ info
(d) PUCCH PC commands
1, 1A, 1B, 1C, 1D, 2, and 2A are the formats of this DCI
Uplink Grant:
It Contains
(a) PUSCH resource indicator
(b) MSC and HARQ info
(c) PUSCH Power control commands
It has format Zero only.
Power Control Command:
it contains
(a) PUSCH Power control Commands for UE
It has format 3 and 3A
If the number of REG not assigned to PHICH or PFICH is Nreg, then the CCE available in the system are number as , 0 …. Ncce-1, where Ncce= Nreg/9
The PDCCH support multiple formats
Format 0: Contains 1 CCE
Format 1: Contains 2 CCE
Format 2: Contains 4 CCE
format 3: Contains 8 CCE
Each CCE carries UL or DL scheduling Control information for one C-RNTI/MAC. It is encoded with CRC.
.
PDSCH:
======
PDSCH carries a of PCH and and DL-SCH, This Channel is the actual medium where everything/user data is carried, after other control channels a transmitted.