4.9 Coding for E‑UCCH

25.2223GPPMultiplexing and channel coding (TDD)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

4.9.1 Coding for E-UCCH for the 3.84Mcps and 7.68Mcps TDD options

E-UCCH is coded in two parts, E-UCCH part 1 and E-UCCH part 2. Both parts of the E-UCCH are transmitted on the E-PUCH (see [7]).

The following information is transmitted by means of E-UCCH part 1:

– E-TFCI information: x_tfci,1, x_tfci,2, …, x_tfci,7

The following information is transmitted by means of E-UCCH part 2:

– Retransmission sequence number (RSN): x_rsn,1, x_rsn,2

– HARQ process ID (HARQ_ID): x_harq,1, x_harq,2

4.9.1.1 Overview

Figure 24 below illustrates the overall coding chain for E-UCCH.

Figure 24: Coding chain for E‑UCCH parts 1 and 2

4.9.1.2 E‑UCCH part 1

4.9.1.2.1 Information field mapping of E‑TFCI

The E‑TFCI is mapped such that x_tfci,1 corresponds to the MSB.

4.9.1.2.2 Channel coding for E-UCCH part 1

The E-TFCI bits are zero-padded and coded to produce the bits y₀, y₁,…y₃₁ using a (32,10) sub-code of the second order Reed-Muller code as defined in subclause 4.3.1.1. Bits correspond to bits of subclause 4.3.1.1, and bits of subclause 4.3.1.1 are set to zero.

4.9.1.2.3 Physical channel mapping for E‑UCCH part 1

E-UCCH part 1 is described in [7]. The sequence of bits y₀, y₁, …, y₃₁ output from the E-UCCH part 1 channel coding is mapped to the E-UCCH part 1 indicator field of each E-PUCH of the E-DCH TTI configured to carry E-UCCH. The bits y_i {i=0,1,…31} are mapped in an identical manner to that described for TFCI in subclause 4.3.1.3 such that they are transmitted over the air in ascending order with respect to i.

4.9.1.3 E‑UCCH part 2

4.9.1.3.1 Information field mapping of retransmission sequence number

To indicate the redundancy version (RV) of each HARQ transmission and to assist the Node B soft buffer management a two bit retransmission sequence number (RSN) is signalled from the UE to the Node B. The Node B can avoid soft buffer corruption by flushing the soft buffer associated to one HARQ process in case the last received RSN for that HARQ process is incompatible with the current one.

The RSN is set by higher layers as described in [15]. For a given HARQ process, once the maximum RSN value of 3 is reached, the RSN alternates between the values of 2 and 3 for any further retransmissions. The RSN thus follows the pattern 0,1,2,3,2,3,2,3,2,3,… The RSN is transmitted by the physical layer in E-UCCH part 2.

The bits (x_rsn,1, x_rsn,2) of the RSN field of E-UCCH part 2 are mapped such that x_rsn,1 corresponds to the MSB of the RSN and x_rsn,2 corresponds to the LSB of the RSN.

The applied E-DCH RV index specifying the used RV (s and r parameter) and in the case of 16-QAM, also the used constellation rearrangement parameter (b) both depend only on the values of RSN, and on N_sys / N_e,data,j as shown in table 25 below.

Table 25: Relation between RSN value and E-DCH RV Index

RSN Value	N_sys / N_e,data,j <1/2	1/2 ≤ N_sys / N_e,data,j
RSN Value	E-DCH RV Index	E-DCH RV Index
0	0	0
1	2	3
2	0	2
3	2	1

The UE shall use either:

– an RV index as indicated in Table 25 and according to the value of RSN

– or, if signalled by higher layers only E-DCH RV index 0 independently of the value of RSN.

4.9.1.3.2 Information field mapping of HARQ process ID

The HARQ process ID bits (x_harq,1, x_harq,2) transmitted on E-UCCH part 2 correspond to the two LSBs of the 3-bit HARQ ID indicated by higher layers (the MSB of the higher layer HARQ ID is not transmitted). Thus, with the higher layer HARQ ID represented as h₁, h₂, h₃ (with h₁ as the MSB), bits x_harq,1, x_harq,2 correspond to bits h₂, h₃.

4.9.1.3.3 Multiplexing of E‑UCCH part 2 information

The retransmission sequence number information (x_rsn,1, x_rsn,2) and the HARQ process ID information (x_harq,1, x_harq,2) are multiplexed together to give a sequence of bits x₁, x₂, …, x₄ where:

x_k = x_rsn,k k=1,2

x_k = x_harq,k-2k=3,4

4.9.1.3.4 Channel coding for E-UCCH part 2

The bits are zero-padded and coded to produce the bits z₀, z₁,…z₃₁ using a (32,10) sub-code of the second order Reed-Muller code as defined in subclause 4.3.1.1. Bits correspond to bits of subclause 4.3.1.1, and bits of subclause 4.3.1.1 are set to zero.

4.9.1.3.5 Physical channel mapping for E‑UCCH part 2

E-UCCH part 2 is described in [7]. The sequence of bits z₀, z₁, …, z₃₁ output from the E-UCCH part 2 channel coding is mapped to the E-UCCH part 2 indicator field of each E-PUCH of the E-DCH TTI configured to carry E-UCCH. The bits z_i {i=0,1,…31} are mapped such that they are transmitted over the air in ascending order with respect to i.

4.9.2 Coding for E-UCCH for the 1.28Mcps TDD option

The E-UCCH on one carrier is used to convey the following information for the E-DCH on the same carrier:

– The modulation type of the selected E-TFC – 0 bits (see note 1)

– The transport block size of the selected E-TFC – 6 bits

– The retransmission sequence number (RSN) – 2 bits

– The HARQ process ID – 2 bits

Note 1: The occupied modulation type is not explicitly signaled, which is inferred from the transport block size.

The E-UCCHs on the different carriers are coded independently. The E-UCCH on one carrier is transmitted on the E-PUCH on the same carrier and is coded using a (32, 10) sub code of the second order Reed Muller code as defined in subclause 4.3.1.1

Figure 24A below illustrates the overall coding chain for E-UCCH on one carrier.

Figure 24A: Coding chain for E-UCCH

4.9.2.1 E-UCCH information field mapping

4.9.2.1.1 Information field mapping of E-TFCI

The E-TFCI is mapped such that x_tfci,1corresponds to the MSB.

4.9.2.1.2 RSN information mapping

The bits (x_rsn,1, x_rsn,2) of the RSN field are mapped such that x_rsn,1 corresponds to the MSB of the RSN and x_rsn,2 corresponds to the LSB of the RSN.

The used RV is implicitly linked to the transmitted RSN, as such the Node-B is always able to determine the correct RV if the RSN information is correctly obtained.

The constellation rearrangement parameter linkage with RSN is shown in Table 25A below

Table 25A: mapping between RSN and b parameters for CoRe

RSN	N_sys / N_e,data,j <1/2	1/2 ≤ N_sys / N_e,data,j
RSN	b	b
0	0	0
1	2	3
2	3	0
3	1	1

In addition to being associated with the value of RSN, the redundancy version (RV) of the E-DCH transmission is also associated with the coding rate of the E-DCH transmission according to Table 25B and Table 25C below.

Table 25B: Relation between RSN and E-DCH RV index for QPSK

RSN	N_sys / N_e,data,j <1/2	1/2 ≤ N_sys / N_e,data,j
RSN	E-DCH RV Index	E-DCH RV Index
0	0	0
1	2	3
2	0	2
3	2	1

Table 25C: Relation between RSN and E-DCH RV index for 16QAM

RSN	N_sys / N_e,data,j <1/2	1/2 ≤ N_sys / N_e,data,j
RSN	E-DCH RV Index	E-DCH RV Index
0	0	0
1	0	3
2	2	1
3	2	2

The UE shall use either:

– an RV index as indicated in Table 25A, 25B, 25C and according to the value of RSN

– or, if signalled by higher layers only E-DCH RV index 0 independently of the value of RSN.

4.9.2.1.3 HARQ information mapping

The bits (x_harq,1, x_harq,2) of the HARQ field are mapped such that x_harq,1 corresponds to the MSB of the HARQ process ID and x_harq,2 corresponds to the LSB of the HARQ process ID.

4.9.2.2 Multiplexing for E-UCCH

The transport block size information (x_tbs,1,…, x_tbs,6), retransmission sequence number information (x_rsn,1, x_rsn,2) and the HARQ process ID information (x_harq,1, x_harq,2) are multiplexed together to give a sequence of bits x₁, x₂, …, x₁₀ where:

x_k = x_tbs,k k=1,2,3,4,5,6

x_k = x_rsn,k-6k=7,8

x_k = x_harq,k-8k=9,10

4.9.2.3 Coding for E-UCCH

The bits are coded to produce the bits z₀, z₁,…z₃₁ using a (32,10) sub-code of the second order Reed-Muller code as defined in subclause 4.3.1.1.

4.9.2.4 Physical channel mapping for E-UCCH

The E-UCCH is described in [7]. The sequence of bits z₀, z₁, …, z₃₁ output from the E-UCCH channel coding is mapped with E-DCH to E-PUCH of the E-DCH TTI configured to carry E-UCCH.