3g overview - part6 dedicated physical channels

8/13/2019 3G Overview - Part6 Dedicated Physical Channels

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Part VI

Dedicated Physical

Channels

120

Company Confidential


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121


Downlink Dedicated Physical Channel (DPCH)

The downlink DPCH is used to transmit the DCH data. Control information and user

data are time multiplexed. The control data is associated with the Dedicated

Physical Control Channel (DPCCH), while the user data is associated with theDedicated Physical Data Channel (DPDCH).

The transmission is organised in 10 ms radio frames, which are divided into 15

timeslots. The timeslot length is 2560 chips. Within each timeslot, following fields

can be found: Data field 1 and data field 2, which carry DPDCH information

Transmission Power Control (TPC) bit field

Transport Format Combination Indicator (TFCI) field, which is optional

Pilot bits

The exact length of the fields depends on the slot format, which is determined byhigher layers. The TFCI is optional, because it is not required for services with fixed

data rates. Slot format are also defined for the compressed mode; hereby different

slot formats are in used, when compression is archived by a changed spreading

factor or a changed puncturing scheme.The pilot sequence is used for channel estimation as well as for the SIR ratio

determination within the inner loop power control. The number of the pilot bits can

be 2, 4, 8 and 16 it is adjusted with the spreading factor. A similar adjustment is

done for the TPC value; its bit numbers range between 2, 4 and 8.

The spreading factor for a DPCH can range between 4 and 512. The spreading factor

can be changed every TTI period.

Superframes last 720 ms and were introduced for GSM-UMTS handover support.


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Superframe = 720 ms

Radio Frame

0

Radio Frame

1

Radio Frame

2

Radio Frame

71

10 ms Frame

Slot 0 Slot 1 Slot 2 Slot 14

TPC

bits

Pilot bitsTFCI

bits

(optional)

Data 2 bitsData 1 bits

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DPDCHDPDCH DPCCH DPCCH

17 different slot formats

Compressed mode slotformat for changed SF

& changed puncturing

2,4,8,16 bits (SIR estimation)2,4,8 bits


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Following features are supported in the downlink:

Blind rate detection, and Discontinuous transmission.

Rate matching is done to the maximum bit rate of the connection. Lower bit rates are

possible, including the option of discontinuous transmission. Please note, that

audible interference imposes no problem in the downlink, since Common Channelshave continuous transmission.

Multicode usage:Several physical channels can be allocated in the downlink to one UE. This can

occur, when several DPCH are combined in one CCTrCH in the PHY layer, and the

data rate of the CCTrCH exceeds the maximum data rates allowed for the physical

channels. Then, on all downlink DPCHs, the same spreading factor is used. Also

the downlink transmission of the DPCHs takes place synchronous. One DPCH

carries DPDCH and DPCCH information, while on the remaining DPCHs, noDPCCH information is transmitted.

But also in the case, when several DPCHs with different spreading factors are in use,

the first DPCH carries the DPCCH information, while in the remaining DPCHs, this

information is omitted (discontinuous transmission).

Multicode usage is not implemented in RAN1.


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Physical Layer Bit Rates (Downlink)

Spreading

factor

Channel

symbol

rate(ksps)

Channel

bit rate

(kbps)

DPDCH

channel bit

rate range(kbps)

Maximum user

data rate with -

rate coding(approx.)

512 7.5 15 36 13 kbps256 15 30 1224 612 kbps

128 30 60 4251 2024 kbps

64 60 120 90 45 kbps

32 120 240 210 105 kbps16 240 480 432 215 kbps

8 480 960 912 456 kbps

4 960 1920 1872 936 kbps

4, with 3

parallelcodes

2880 5760 5616 2.8 Mbps

The number of orthogonal channelization codes = Spreading factor

Half rate speech

Full rate speech

128 kbps

384 kbps

2 Mbps

124



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TS TS

maximum bit rate

TS TS TS

discontinuous transmission with lower bit rate

Multicode usage:

TS TS TS

125


TS TS TS

DPCH 1

DPCH 2

DPCH 3


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Power Offsets for the DPCH

Node B RNC

DCH Data Frame

Iub

UE

Uu

PO1

NBAP: RADIO LINK SETUP REQUEST

TPC

bitsPilot bits

TFCI

bits(optional) Data 2 bitsData 1 bits

PO3PO2

Power offsets

TFCS

DL DPCH slot

format

FDD DL TPCstep size

P0x: 0..6 dB

step size: 0.25dB


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Nokia Parameters Related to DPCHs

RNC: PowerOffsetDLdpcchPilot

The parameter defines the power offset for the pilot symbols in relative tothe data symbols in dedicated downlink physical channel[0 6 dB]; step size 0.25 dB; default: 3 dB for 12.2 kbps

RNC: PowerOffsetDLdpcchTpc,The parameter defines the power offset for the TPC symbols relative to thedata symbols in dedicated downlink physical channel[0 6 dB]; step size 0.25 dB; default: 3 dB for 12.2 kbps

RNC: PowerOffsetDLdpcchTfci,The parameter defines the power offset for the TFCI symbols relative to thedata symbols in dedicated downlink physical channel.[0 6 dB], step size 0.25 dB; default: 3 dB for 12.2 kbps

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Superframe = 720 ms

Slot 0 Slot 1 Slot 2 Slot 14

10 ms Frame

TPC

bits

Pilot bitsTFCI bits(optional)

Data 1 bits

Radio Frame

0

Radio Frame

1

Radio Frame

2

Radio Frame

71

DPDCH

129


DPCCH FBI bits

7

differentslot

formats

6 different slotformats

Compressed mode

slot format for

changed SF &

changed puncturing

Feedback Indicator for

Closed loop mode transmit

diversity, & Site selection diversity

transmission (SSDT)

Uplink Dedicated Physical Channels


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130


Discontinuous Transmission and Power OffsetsDiscontinuous transmission (DTX) is supported for the DCH both uplink and

downlink. If DTX is applied in the downlink as it is done with speech then 3000

bursts are generated in one second. (1500 times the pilot sequence, 1500 times the

TPC bits) This causes two problems:

Inter-frequency interference, caused by the burst generation. At the Node B, the

problem can be overcome with exquisite filter equipment. This filter equipment is

expensive and heavy. Therefore it cannot be applied in the UE. The UEs solution isI/Q code multiplexing, with a continuous transmission for the DPCCH. DPDCH

changes can still occur, but they are limited to the TTI period. The minimum TTI

period is 10 ms. The same effects can be observed, then the DPDCH data rate and

with it its output power is changing. 3000 bursts causes audible interference with other equipment just see for

example GSM. By reducing the changes to the TTI period, the audible interference

is reduced, too.

Determination of the power difference between the DPCCH and DPDCHI/Q code multiplexing is done in the uplink, i.e. the DPCCH and DPDCH are transmitted with

different codes (and possible with different spreading factors). Gain factors are specified: c is

the gain factor for the DPCCH, while d is the gain factor for the DPDCH. The gain factors

may vary for each TFC. There are two ways, how the UE may learn about the gain factors:

The gain factors are signalled for each TFC.

If so, the nominal power relationAj between the DPDCH and DPCCH is d/c. The gain factor is calculated based on reference TFCs.


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DPCCH

DPDCH

DPCCH

DPDCH

DPCCH

DPDCH

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TTI TTI TTI

UL DPDCH/DPCH Power Difference:

DPCCH

DPDCH

=dc

=Nominal Power RelationAj

two methods to determine the gain factors:

signalled for each TFCs

calculation based on reference TFCs

Discontinuous Transmission and Power Offsets


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Initial Uplink DCH Transmission

When we look to the PRACH, we can see, that a preambles were used to avoid UEs

to access UTRAN with a too high initial transmission power. The same principle isapplied for the DPCH.After PRACH procedure the UE transmits between 0 to 7

radio frames only the DPCCH uplink (the period is called DPCCH power control

Preamble), before the DPDCH is code multiplexed. The number of radio frames is

set by the higher layers (RRC resp. the operator).Also for this period of time, onlyDPCCH can be found in the downlink.

The UE can be also informed about a delay regarding RRC signalling this is

called SRB delay, which can also last 0 to 7 radio frames. The SRB delay follows

after the DPCCH preamble.

How to set the the transmission power of the first UL DPCCH preamble? Its powerlevel is

DPCCH_Initial_power = CPICH_RSCP + DPCCH_Power_offset

The DPCCH Power Offset is retrieved from RRC messages. Its value ranges

between 164 and 6 dB (step size 2 dB). CPICH_RSCP is the received signalcode power on the P-CPICH, measured by the UE.


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Initial Uplink DCH Transmission

T0

DPCCH only DPCCH & DPDCH

reception

at UE

trans-

mission

at UE

0 to 7 frames for

power control preamble

DPCCH only,

always based on PCA1

DPCCH & DPDCH

PCA based on RRC

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DPCCH_Init ial_power = CPICH_RSCP + DPCCH_Power_offset


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Radio frame timing and access slot timing of downlink physical channels

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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 framewith (SFN modulo 2) = 0 Radio framewith (SFN modulo 2) = 1

DPCH,n

P-CCPCH

Any CPICH

PICH for k:thS-CCPCH

Any PDSCH

n:th DPCH

10 ms

Subframe#0

HS-SCCHSubframes

Subframe#1

Subframe#2

Subframe#3

Subframe#4

3g overview - part6 dedicated physical channels

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