4.9 Coding for E‑DPCCH
25.2123GPPMultiplexing and channel coding (FDD)Release 17TS
The following information is transmitted by means of the E-DPCCH:
– Retransmission sequence number (RSN): xrsn,1, xrsn,2
– E-TFCI: xtfci,1, xtfci,2, …, xtfci,7
– "Happy" bit: xh,1
4.9.1 Overview
The figure below illustrates the overall coding chain for E-DPCCH.
Figure 23: Coding chain for E‑DPCCH
4.9.2 E‑DPCCH information field mapping
4.9.2.1 Information field mapping of E‑TFCI
The E‑TFCI is mapped such that xtfci,1 corresponds to the MSB.
4.9.2.2 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 more than 3 consecutive E‑DPCCH transmissions on that HARQ process can not be decoded or the last received RSN is incompatible with the current one.
The RSN is set by higher layers as described in [16]. The RSN is mapped such that xrsn,1 corresponds to the MSB.
The applied E-DCH RV index specifying the used RV (s and r parameter) depends on the RSN, on Nsys / Ne,data,j, and if RSN=3 also on the TTIN (TTI number). For 10 ms TTI the TTI number is equal to the CFN, for 2 ms TTI
TTIN = 5*CFN + subframe number
where the subframe number counts the five TTIs which are within a given CFN, starting from 0 for the first TTI to 4 for the last TTI. NARQ is the number of Hybrid ARQ processes.
Table 16: Relation between RSN value and E-DCH RV Index
|
RSN Value |
Nsys / Ne,data,j <1/2 |
1/2 ≤ Nsys / Ne,data,j |
|
E-DCH RV Index |
E-DCH RV Index |
|
|
0 |
0 |
0 |
|
1 |
2 |
3 |
|
2 |
0 |
2 |
|
3 |
[ TTIN/NARQ mod 2 ] x 2 |
TTIN/NARQ mod 4 |
The UE shall use either
– an RV index as indicated in Table 16 and according to the RSN
– or, if signalled by higher layers only E-DCH RV index 0 independently of the RSN.
4.9.2.3 Information field mapping of the "Happy" bit
The UE shall set xh,1 as specified in Table 16A.
Table 16A: Mapping of "Happy" bit
|
"Happy" bit |
xh,1 |
|
Happy |
1 |
|
Not happy |
0 |
4.9.3 Multiplexing of E‑DPCCH information
The E‑TFCI xtfci,1, xtfci,2, …, xtfci,7, the retransmission sequence number xrsn,1, xrsn,2 and the "happy" bit xh,1 are multiplexed together. This gives a sequence of bits x1, x2, …, x10 where
xk = xh,1 k=1
xk = xrsn,4-k k=2,3
xk = xtfci,11-k k=4,5,…,10
4.9.4 Channel coding for E‑DPCCH
Channel coding of the E‑DPCCH is done using a sub-code of the second order Reed-Muller code. Coding is applied to the output x1, x2, …, x10 from the E-DPCCH multiplexing, resulting in:
i=0, 1, …, 29
The basis sequences are as described in 4.3.3 for i=0, 1, …, 29.
4.9.5 Physical channel mapping for E‑DPCCH
The E-DPCCH is described in [2]. The sequence of bits z0, z1, …, z29 output from the E-DPCCH channel coding is mapped to the corresponding E-DPCCH sub frame. The bits are mapped so that they are transmitted over the air in ascending order with respect to i. If the E‑DCH TTI is equal to 10 ms the sequence of bits is transmitted in all the E‑DPCCH sub frames of the E‑DPCCH radio frame.
For compressed frames in the uplink and the case when E‑DCH TTI length is 10 ms, the bits mapped to the E‑DPCCH idle slots specified in 4.4.5.3 shall not be transmitted.