PCH in Idle Mode

7/31/2019 PCH in Idle Mode

http://slidepdf.com/reader/full/pch-in-idle-mode 1/19

Paging in idle modeDanny 2003/5/5



AgendaPage behavior (UE)

Timing among PICH, P-CCPCH and SCCPCHReceive parameters via SIB1 and SIB5

Paging Channel selectionCompute and get selected SCCPCH and PICH info.

Compute Paging OccasionGet and Parse Page IndicatorGet Page message and Process

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Timing among PICH, P-CCPCHand SCCPCH

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k:th S-CCPCH

AICH accessslots

SecondarySCH

PrimarySCH

S-CCPCH,k

10 ms

PICH

#0 #1 #2 #3 #14#13#12#11#10#9#8#7#6#5#4

Radio frame with (SFN modulo 2) = 0 Radio frame with (SFN modulo 2) = 1

DPCH,n

P-CCPCH

Any CPICH

PICH for k:thS-CCPCH

Any PDSCH

n:th DPCH

10 ms



Timing among PICH, P-CCPCHand SCCPCH

The S-CCPCH timing may be different for different S-CCPCHs, but the offset from the P-CCPCH frame timingis a multiple of 256 chips, i.e. S-CCPCH,k = T k 256 chip,Tk {0, 1, …, 149}. [Extra ref 25.331 10.3.6.71]The PICH timing is PICH = 7680 chips prior to itscorresponding S-CCPCH frame timing, i.e. the timing of the S-CCPCH carrying the PCH transport channel with thecorresponding paging information.A paging indicator set in a PICH frame means that thepaging message is transmitted on the PCH in the S-CCPCH frame starting PICH chips after the transmittedPICH frame.

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Page Channel SelectionAfter camping normally or camp on any cell, theUE will select and monitor the indicated PICHand PCH of the cell.

The UE get the indicated PICH and PCHinformation via SIB5.

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Receive parameters via SIB1and SIB5

SIB 1 procedure.Get IE ”DRX cycle length coefficient” store the value of the IE "CN domain specific DRXcycle length coefficient" for use in connected mode

SIB 5 procedure.Select a S-CCPCH as specified in 25.304 and in8.5.19, and start to receive PICH associated with the

PCH by the selected S-CCPCH using the parametersgiven by the IE "PICH info"

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Index of selected SCCPCH (IDLEmode)

The UE shall select a SCCPCH from the ones listed inSIB 5 based on IMSI as follows:

"Index of selected SCCPCH" = IMSI mod K,

where K is equal to the number of listed SCCPCHs whichcarry a PCH (i.e. SCCPCHs carrying FACH only shall not becounted). These SCCPCHs shall be indexed in the order of theiroccurrence in SIB 5 from 0 to K-1.

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Index of selected SCCPCH(Connected mode)

When entering Connected mode from Idle mode bysending an RRC CONNECTION REQUEST message, theUE shall select the S-CCPCH which carries an FACH tobe used for reception of the RRC CONNECTION SETUP

message according to the following rule:

- the UE shall select an SCCPCH from the SCCPCHs listed inSystem Information Block type 5 (SIB 5) based on "Initial UEIdentity" as follows:

"Index of selected SCCPCH" = "Initial UE Identity" mod K,

where K is equal to the number of listed SCCPCHs which carry aFACH (i.e. SCCPCHs carrying PCH only shall not be counted ).

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Index of selected SCCPCHIf the UE has no IMSI, for instance when making anemergency call without USIM, the UE shall use asdefault number IMSI = 0.

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Compute Paging Occasion-DRX

The UE may use Discontinuous Reception (DRX) inidle mode in order to reduce power consumption.When DRX is used the UE needs only to monitor onePage Indicator, PI, in one Paging Occasion per DRXcycle.UE may attached to different CN domains. But UEshall store all different DRX cycle length and usesshortest of them.The DRX cycle length shall be MAX(2 k , PBP) frames,where k is an integer and PBP is the Paging Block Periodicity. PBP is only applicable for TDD and is equal tothe PICH repetition period that is broadcast in systeminformation. For FDD, PBP=1.

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Compute Paging OccasionIn FDD the UE shall monitor its paging indicator inPICH frame with SFN given by the Paging Occasion.The value of the Paging Occasion is determined asfollows:

Paging Occasion= {(IMSI div K) mod (DRX cycle length divPBP)} * PBP + n * DRX cycle length + Frame Offset

Where n = 0,1,2… as long as SFN is below its maximumvalue.

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Compute Paging Occasion

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1, k+1, 2k+1,...

2, k+2, 2k+2, ...

3, k+3, 2k+3, ...

k, 2k, 3k, ...

k

DRX Cycle



Compute Paging Occasion-PIThe actual Page Indicator within a Paging Occasion thatthe UE shall read is similarly determined based on IMSI.The page indicator to use is calculated by usingfollowing formula:

PI = DRX Index mod Np

where DRX Index = IMSI div 8192 Np (for FDD, Np is the number of page indicators within a frame )

Ps. DRX Index = (IMSI div K) div (DRX cycle length div PBP)

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Get and Parse Page Indicator-PICH format

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b1b0

288 bits for paging indication12 bits (transmission

off)

One radio frame (10 ms)

b287 b288 b299

Number of paging indicators per frame(Np)

P q = 1 P q = 0

Np=18 {b 16q , …, b 16q+15 } = {-1,-1,…, -1} {b16q , …, b 16q+15 } = {+1,+1,…,+1} Np=36 {b 8q , …, b 8q+7 } = {-1,-1,…, -1} {b8q , …, b 8q+7 } = {+1,+1,…,+1} Np=72 {b 4q , …, b 4q+3 } = {-1, -1,…, -1} {b4q , …, b 4q+3 } = {+1, +1,…,+1}

Np=144 {b 2q , b 2q+1 } = {-1,-1} {b2q , b 2q+1 } = {+1,+1}



Get and Parse Page Indicator

The PI calculated by higher layers for use for a certain UE,is associated to the paging indicator P q, where q iscomputed as a function of the PI computed by higherlayers, the SFN of the P-CCPCH radio frame during whichthe start of the PICH radio frame occurs, and the numberof paging indicators per frame (Np):

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Np NpSFN SFN SFN SFN PI q mod144

144mod512 / 64 / 8 / 18



Get and Parse Page Indicator-Pq (DRX = 64)

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Get and Parse Page Indicator-Pq (DRX = 128)

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Q & A

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PCH in Idle Mode

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