4.11 Coding for E-HICH ACK/NACK

25.2223GPPMultiplexing and channel coding (TDD)Release 17TS

4.11.1 Coding for E-HICH ACK/NACK for the 3.84Mcps and 7.68Mcps options

4.11.1.1 Overview

The ACK/NACK is transmitted on the E‑HICH as described in [7].

The value of a binary HARQ acknowledgement indicator for user h is denoted "a_h" and may assume the value 0 or 1. The value of the indicator is mapped as shown in table 28.

Table 28 – Mapping of HARQ acknowledgement indicator

Command	HARQ acknowledgement indicator value (ah)
NACK	0
ACK	1

A HARQ acknowledgement indicator is mapped to one of 240 signature sequences of length 240 bits and represented by the bit sequence b_h,0, b_h,1, …, b_h,239 for the h^th acknowledgement indicator. The signature sequence number "r" is selected as described in [7].

The signature sequence b_h,0, b_h,1, …, b_h,239 is constructed via coding of a_h followed by bit scrambling. Spare bits are inserted during the physical channel mapping stage to produce the output sequence d_h,0, d_h,1, …, d_h,U,.

4.11.1.2 Coding of the HARQ acknowledgement indicator

Bit a_h is used to form the sequence s_2,v (v=0,1,…,239) via a two-stage serialised binary spreading process as shown in figure 26.

Figure 26

The output of the first spreading stage is , where k=0, 1, 2,…, 19.

The output of the second spreading stage is , where v=0, 1,…, 239 and where and, .

The binary sequences selected for the first (C_1,i,k) and second (C_2,j,m) spreading operations are derived as a function of the HARQ acknowledgement sequence number r (see [7]) such that:

The first orthogonal sequence set (C_1,i,k) is given by table 29 and the second orthogonal sequence set (C_2,j,m) is given by table 30.

Table 29 – Primary code sequences for HARQ acknowledgement indicator

k	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19
C1,0,k	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
C1,1,k	1	0	0	1	1	0	0	0	0	1	0	1	0	1	1	1	1	0	0	1
C1,2,k	1	0	1	1	0	0	0	0	1	0	1	0	1	1	1	1	0	0	1	0
C1,3,k	1	1	1	0	0	0	0	1	0	1	0	1	1	1	1	0	0	1	0	0
C1,4,k	1	1	0	0	0	0	1	0	1	0	1	1	1	1	0	0	1	0	0	1
C1,5,k	1	0	0	0	0	1	0	1	0	1	1	1	1	0	0	1	0	0	1	1
C1,6,k	1	0	0	0	1	0	1	0	1	1	1	1	0	0	1	0	0	1	1	0
C1,7,k	1	0	0	1	0	1	0	1	1	1	1	0	0	1	0	0	1	1	0	0
C1,8,k	1	0	1	0	1	0	1	1	1	1	0	0	1	0	0	1	1	0	0	0
C1,9,k	1	1	0	1	0	1	1	1	1	0	0	1	0	0	1	1	0	0	0	0
C1,10,k	1	0	1	0	1	1	1	1	0	0	1	0	0	1	1	0	0	0	0	1
C1,11,k	1	1	0	1	1	1	1	0	0	1	0	0	1	1	0	0	0	0	1	0
C1,12,k	1	0	1	1	1	1	0	0	1	0	0	1	1	0	0	0	0	1	0	1
C1,13,k	1	1	1	1	1	0	0	1	0	0	1	1	0	0	0	0	1	0	1	0
C1,14,k	1	1	1	1	0	0	1	0	0	1	1	0	0	0	0	1	0	1	0	1
C1,15,k	1	1	1	0	0	1	0	0	1	1	0	0	0	0	1	0	1	0	1	1
C1,16,k	1	1	0	0	1	0	0	1	1	0	0	0	0	1	0	1	0	1	1	1
C1,17,k	1	0	0	1	0	0	1	1	0	0	0	0	1	0	1	0	1	1	1	1
C1,18,k	1	0	1	0	0	1	1	0	0	0	0	1	0	1	0	1	1	1	1	0
C1,19,k	1	1	0	0	1	1	0	0	0	0	1	0	1	0	1	1	1	1	0	0

Table 30 – Secondary code sequences for HARQ acknowledgement indicator

m	0	1	2	3	4	5	6	7	8	9	10	11
C2,0,m	1	1	1	1	1	1	1	1	1	1	1	1
C2,1,m	1	0	1	0	1	1	1	0	0	0	1	0
C2,2,m	0	1	1	0	1	0	0	0	1	1	1	0
C2,3,m	1	1	0	0	1	0	1	1	1	0	0	0
C2,4,m	1	0	1	0	0	1	0	1	1	1	0	0
C2,5,m	0	1	1	0	1	1	0	1	0	0	0	1
C2,6,m	0	1	1	1	0	1	1	0	1	0	0	0
C2,7,m	0	0	1	1	1	0	1	1	0	1	0	0
C2,8,m	1	1	1	0	0	0	1	0	0	1	0	1
C2,9,m	0	0	0	0	1	1	1	0	1	1	0	1
C2,10,m	0	1	0	0	0	1	1	1	0	1	1	0
C2,11,m	1	1	0	1	1	1	0	0	0	1	0	0

4.11.1.3 Bit scrambling of the E-HICH

The bit sequence b_h,0,b_h,1,…,b_h,239 is formed by applying bit scrambling (as defined in subclause 4.2.9) to the sequence s_2,v.

4.11.1.4 Physical channel mapping of the E-HICH

The bit sequence b_h,0,b_h,1,…,b_h,239 is segmented into two halves, b_h,0,, …, b_h,119, and b_h,120,…,b_h,239. A sequence of U spare bits z_u (u=0…U-1) are inserted between the first and second half of the sequence to form:

d_h = {b_h,0, b_h,1, … , b_h,119, z₀, z₁, … z_U-1, b_h,120, b_h,121, … , b_h,239}

U is equal to 4 or 36 dependant on the burst type (see [7]). The spare bit sequence z_u is not defined.

4.11.2 Coding for E-HICH for the1.28Mcps option only

4.11.2.1 Overview

The scheduled and non-Scheduled transmissions on different E‑HICHs are described in [7]. The acknowledgement indicators for the E-DCH semi-persistent scheduling operation can be transmitted on the same E-HICH carrying indicators for scheduled traffic or the E-HICH carrying indicators for non-scheduled traffic as described in [7].

For 1.28Mcps TDD multi-carrier E-DCH transmission, the acknowledgement indicators for the E-PUCH on one carrier is associated with the E-HICHs on the same carrier. The E-HICHs on the different carriers are coded independently.

The value of a binary HARQ acknowledgement indicator for user h is denoted "a_h" and may assume the value 0 or 1. The value of the indicator is mapped as same as that of 3.84Mcps shown in subclause 4.11.1.1.

Construction of the bit sequence for the h^th acknowledgement indicator is achieved via a spreading process using an orthogonal sequence which is the row of an orthogonal matrix of order 80. This orthogonal matrix (C₈₀) is Kronecker tensor product of one Hadamard matrix of order 20 (C₂₀) and another Hadamard matrix of order 4 (C₄),

is Kronecker tensor product. (note: Kronecker product is not commutative, i.e. ). The element "0" in Hadamard C₂₀ and C₄ shall be replaced by "-1" before the Kronecker tensor product operation. And after the operation the elements "-1" in C₈₀ should be converted back into "0".

These two Hadamard matrices are given by table 31 and table 32.

Table 31: Hadamard matrix of order 4

m	0	1	2	3
C4,0,m	1	1	1	1
C4,1,m	1	0	1	0
C4,2,m	1	1	0	0
C4,3,m	0	1	1	0

Table 32: Hadamard matrix of order 20

k	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19
C20,0,k	1	0	0	0	0	1	0	0	0	0	1	1	0	0	1	1	0	1	1	0
C20,1,k	0	1	0	0	0	0	1	0	0	0	1	1	1	0	0	0	1	0	1	1
C20,2,k	0	0	1	0	0	0	0	1	0	0	0	1	1	1	0	1	0	1	0	1
C20,3,k	0	0	0	1	0	0	0	0	1	0	0	0	1	1	1	1	1	0	1	0
C20,4,k	0	0	0	0	1	0	0	0	0	1	1	0	0	1	1	0	1	1	0	1
C20,5,k	0	1	1	1	1	1	0	0	0	0	0	1	0	0	1	1	1	0	0	1
C20,6,k	1	0	1	1	1	0	1	0	0	0	1	0	1	0	0	1	1	1	0	0
C20,7,k	1	1	0	1	1	0	0	1	0	0	0	1	0	1	0	0	1	1	1	0
C20,8,k	1	1	1	0	1	0	0	0	1	0	0	0	1	0	1	0	0	1	1	1
C20,9,k	1	1	1	1	0	0	0	0	0	1	1	0	0	1	0	1	0	0	1	1
C20,10,k	0	0	1	1	0	1	0	1	1	0	1	0	0	0	0	0	1	1	1	1
C20,11,k	0	0	0	1	1	0	1	0	1	1	0	1	0	0	0	1	0	1	1	1
C20,12,k	1	0	0	0	1	1	0	1	0	1	0	0	1	0	0	1	1	0	1	1
C20,13,k	1	1	0	0	0	1	1	0	1	0	0	0	0	1	0	1	1	1	0	1
C20,14,k	0	1	1	0	0	0	1	1	0	1	0	0	0	0	1	1	1	1	1	0
C20,15,k	0	1	0	0	1	0	0	1	1	0	1	0	0	0	0	1	0	0	0	0
C20,16,k	1	0	1	0	0	0	0	0	1	1	0	1	0	0	0	0	1	0	0	0
C20,17,k	0	1	0	1	0	1	0	0	0	1	0	0	1	0	0	0	0	1	0	0
C20,18,k	0	0	1	0	1	1	1	0	0	0	0	0	0	1	0	0	0	0	1	0
C20,19,k	1	0	0	1	0	0	1	1	0	0	0	0	0	0	1	0	0	0	0	1

The binary orthogonal sequence (C_80,r,n) used for spreading operation is selected from the r^th row of the orthogonal matrix of order 80 (C₈₀). A HARQ acknowledgement indicator is synchronously linked with the E-DCH TTI transmission to which it relates. There is thus a one-to-one association between an E-DCH TTI transmission and its respective HARQ acknowledgement indicator.

4.11.2.2 Coding of the HARQ acknowledgement indicator and TPC/SS

For scheduled transmissions, E-HICHs carry HARQ acknowledgement indicators only.

When the special default midamble allocation scheme is not used for E-PUCH, a logical allocation resource tag ID "r" (r=0, 1, 2,…, 79) is calculated first for the E-DCH resource allocation associated with the HARQ acknowledgement indicator.

where:

t₀ is the last (highest-numbered) allocated timeslot (1,2,..,5)

q₀ is the lowest-numbered channelisation code index allocated in timeslot t₀ (1,2,…, Q₀)

Q₀ is the spreading factor of the lowest-numbered channelisation code index allocated in timeslot t₀

When the special default midamble allocation scheme is used for E-PUCH, a logical allocation resource tag ID "r" (r=0, 1, 2,…, 79) is calculated first associated with the HARQ acknowledgement indicator.

where:

t₀, q₀ and Q₀ have the same definition as above .

Offset is decided by the special default midamble pattern indicator on E-AGCH and the mapping in Table33 below applies.

Table 33: Offset mapping table

offset	xmpi,1	xmpi,2
0	0	0
1	0	1
2	1	0
3	1	1

The logical resource tag ID r is then mapped to a physical allocation resource tag ID r’,

,

where P is a permutation function depends on the logical signature index r, system sub-frame number SFN’ of E-HICH and the cell specific basic midamble code sequence. A 7-tap linear feedback shift register (LFSR) is used to generate pseudo-random numbers which are then used to generate the pseudo-random permutation P. The generator polynomial of the 7-tap LFSR is , as shown in Figure 27.

Figure 27: Structure of PN register

The pseudo-random permutation is generated according to the following procedures:

1. Initialization

(a) Initialize M = 80, initialize P as P(m) = m, m = 0, 1, …, M-1;

(b) Initialize N = 7;

(c) Initialize PN register with seed s, where s = LSB(SFN’, N)⊕LSB(MidambleCode, N) and s₆, s₅, … s₀ are put into the register in the order as shown in figure 27;

(d) Initialize i = 0.

2. Repeat the following steps while i <= M – 3.

(a) Find the smallest p such that M – i – 1 < 2^p;

(b) Clock the PN register N times to obtain an N-bit pseudorandom number x. Set k = LSB(x, p);

(c) If k > M – i – 1, set k = k – (M – i);

(d) Swap the i-th and the (k+i)-th element of P, i.e., tmp = P(i), P(i) = P(k+i), P(k+i) = tmp;

(e) Increment i by 1.

where "LSB(x, n)" means the right most n bits of x, "⊕" means modulo 2 addition, and the first output bit from the PN register is the MSB, while the final output bit is the LSB . The resulting P is the output permutation and the physical signature sequence index is given by .

The output of the spreading stage is equal to , where n=0,1,…,79 and is the Xor operation.

For Non-Scheduled transmissions and E-DCH semi-persistent scheduling operation,, E-HICHs carry HARQ acknowledgement indicators and TPC/SS commands. The 80 orthogonal sequences are divided into 20 groups while each group includes 4 sequences of contiguous logical resource tag ID. The mapping between the logical resource tag ID and the physical tag ID is same as scheduled transmissions. Each non-scheduled user is assigned one group by higher layer to indicate the HARQ acknowledgement indicator and TPC/SS command. The first one of the four sequences is used for the acknowledgement indicator’s spreading operation and one of the other three is used to indicate TPC/SS command implicitly. The mapping relations between them are described in [7].

The HARQ acknowledgement indicator is spread by the assigned orthogonal sequence (C_80,s’,n), where s’ is the physical resource tag ID. The output of the spreading stage is equal to, where n=0,1,…,79. The sequence chosen to indicate TPC/SS command is denoted as "e_h,n", , where is the same as the parameter B defined in [7].

4.11.2.3 Bit scrambling and Physical channel mapping of the E-HICH

For scheduled transmission, the bit sequence b_h,0,b_h,1,…,b_h,79 is segmented into two halves, b_h,0,, …, b_h,39, and b_h,40,…,b_h,79. 8 spare bits z_u (u=0…7) are inserted between the first and second half of the sequence to form:

d_h = {b_h,0, b_h,1, … , b_h,39, z₀, z₁, … z₇, b_h,40, b_h,41, … , b_h,79}

The spare bit sequence z_u is not defined.For Non-Scheduled transmission, the corresponding output bit sequences are:

d_h1 = {c_h,0, c_h,1, … , c_h,39, z₀, z₁, … z₇, c_h,40, c_h,41, … , c_h,79}

d_h2 = {e_h,0, e_h,1, … , e_h,39, z₀, z₁, … z₇, e_h,40, e_h,41, … , e_h,79}

Then the corresponding bit sequence d_h or d_h1/d_h2 is formed by applying bit scrambling (as defined in subclause 4.2.9) to the sequence s_h,n or s_h1,n/s_h2,n, n= 0,1,…,87.