4.6A Coding for HS-SCCH type 2

25.2123GPPMultiplexing and channel coding (FDD)Release 17TS

4.6A.1 Overview

HS-SCCH type 2 is used for HS-SCCH-less operation. HS-SCCH type 2 is not used when the UE is configured in MIMO mode or in MIMO mode with four transmit antennas. During second and third transmission, the following information is transmitted by means of the HS-SCCH type 2 physical channel.

– Channelization-code-set information (7 bits): x_ccs,1, x_ccs,2, …, x_ccs,7

– Modulation scheme information (1 bit): x_ms,1

– Special Information type (6 bits): x_type,1, x_type,2, …, x_type,6

– Special Information (7 bits): x_info,1, x_info,2, x_info,3, x_info,4, x_info,5, x_info,6, x_info,7

– UE identity (16 bits): x_ue,1, x_ue,2, …, x_ue,16

Figure 19A below illustrates the overall coding chain for HS-SCCH type 2.

Figure 19A: Coding chain for HS-SCCH type 2

4.6A.2 HS-SCCH Type 2 information field mapping

4.6A.2.1 The first transmission

When HS-SCCH_less_mode=1 for a UE (as defined in [4]), the first transmission of an HS-DSCH transport block using CRC attachment method 2 shall be sent without an associated HS-SCCH. In this case, the UE shall use the following signalling values in order to attempt to decode the transport block:

– Channelization-code-set information: Configured by higher layers

– Modulation scheme information: QPSK

– Transport-block size information: Each of four possible sizes configured by higher layers

– Redundancy and constellation version: X_rv =0 (see 4.6.2.1)

– UE identity: Configured by higher layers

4.6A.2.2 The second and the third transmissions

For HS-SCCH_less_mode=1 there are at maximum 3 transmissions for a HS-DSCH transport block using CRC attachment method 2. The 2^nd and 3^rd transmissions of a transport block that was sent without an associated HS-SCCH in the first transmission, as described in subclause 4.6A.2.1.1, are associated with an HS-SCCH of type 2.

4.6A.2.2.1 Special Information mapping

The Special Information type x_type,1, x_type,2, …, x_type,6 shall be set to ”111110’ to indicate HS-SCCH less operation.

The Special Information bits x_info,1, x_info,2, …, x_info,7 are comprised of:

– Transport-block size information (2 bits): x_info,1, x_info,2 = x_tbs,1, x_tbs,2

– Pointer to the previous transmission (3 bits): x_info,3, x_info,4, x_info,5 = x_ptr,1, x_ptr,2, x_ptr,3

– Second or third transmission (1 bit): x_info,6 = x_sec,1

– Reserved (1 bit): x_info,7 = x_res,1

4.6A.2.2.1.1 Transport-block size information mapping

The Transport-block size information (2 bits) x_tbs,1, x_tbs,2 is the unsigned binary representation of a reference to one of the four Transport-block sizes and the associated number of HS-PDSCH codes for the first transmission configured by higher layers.

xtbs,1, xtbs,2	Entry in “Transport Block size list” as signalled in the HS-SCCH-less Information of HS_SCCH_LESS_PARAMS [13]
”00’	1st entry
”01’	2nd entry
”10’	3rd entry
”11’	4th entry

4.6A.2.2.1.2 Pointer to the previous transmission mapping

Pointer to the previous transmission (3 bits) x_ptr,1, x_ptr,2, x_ptr,3 is the unsigned binary representation of s, such that the previous transmission of the same transport block started (6+s) subframes before the start of this transmission.

4.6A.2.2.1.3 Second or third transmission mapping

Second or Third transmission (1 bit) indicates whether this is the second or third transmission.

If x_sec,1= ”0’, this is a second transmission.

If x_sec,1= ”1’, this is a third transmission.

4.6A.2.2.2 Redundancy and Constellation Version mapping

The redundancy version X_rv for the second and third transmissions shall be equal to 3 and 4 respectively, as defined in Table 13.

4.6A.2.2.3 Modulation scheme mapping

The value of x_ms,1 shall be set to ”0’ (QPSK).

4.6A.2.2.4 Channelization code-set mapping

The channelization code-set bits x_ccs,1, x_ccs,2, …, x_ccs,7 are coded as per clause 4.6.2.3 where the value of P shall be set to either 1 or 2.

4.6A.2.2.5 UE identity mapping

The UE identity is encoded as per clause 4.6.2.4.

4.6A.3 Multiplexing of HS-SCCH Type 2 information

The channelization-code-set information x_ccs,1, x_ccs,2, …, x_ccs,7 and modulation-scheme information x_ms,1 are multiplexed together. This gives a sequence of bits x_1,1, x_1,2, …, x_1,8 where

x_1,i = x_ccs,i i=1,2,…,7

x_1,i = x_ms,i-7 i=8

The Special Information type x_type,1, x_type,2, …, x_type,6, and Special Information x_info,1, x_info,2, x_info,3, x_info,4, x_info,5, x_info,6, x_info,7 are multiplexed together. This gives a sequence of bits x_2,1, x_2,2, …, x_2,13 where

x_2,i = x_type,i i=1,2,…,6

x_2,i = x_info,i-6 i=7,8,…,13

4.6A.4 CRC attachment for HS-SCCH Type 2

The sequence of bits y₁, y₂, …, y₂₉, is calculated according to Clause 4.6.4.

4.6A.5 Channel coding for HS-SCCH Type 2

Channel coding is performed according to Clause 4.6.5.

4.6A.6 Rate matching for HS-SCCH Type 2

Rate matching is performed according to Clause 4.6.6.

4.6A.7 UE specific masking for HS-SCCH Type 2

The mask output bits s_1,1,s_1,2…s_1,40 are calculated according to Clause 4.6.7.

4.6A.8 Physical channel mapping for HS-SCCH Type 2

Physical channel mapping is performed according to Clause 4.6.8.