4 Control Channels
3GPP45.003GSM/EDGE Channel codingRelease 17TS
4.1 Slow associated control channel (SACCH)
4.1.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits {d(0),d(1),…,d(183)}. It is delivered on a burst mode.
4.1.2 Block code
a) Parity bits:
The block of 184 information bits is protected by 40 extra bits used for error correction and detection. These bits are added to the 184 bits according to a shortened binary cyclic code (FIRE code) using the generator polynomial:
g(D) = (D23 + 1)*(D17 + D3 + 1)
The encoding of the cyclic code is performed in a systematic form, which means that, in GF(2), the polynomial:
d(0)D223 + d(1)D222 +…+d(183)D40 + p(0)D39 + p(1)D38 +…+p(38)D + p(39)
where {p(0),p(1),…,p(39)} are the parity bits , when divided by g(D) yields a remainder equal to:
1 + D + D2 +…+ D39.
b) Tail bits
Four tail bits equal to 0 are added to the information and parity bits, the result being a block of 228 bits.
u(k) = d(k) for k= 0,1,…,183
u(k) = p(k‑184) for k = 184,185,…,223
u(k) = 0 for k = 224,225,226,227 (tail bits)
4.1.3 Convolutional encoder
This block of 228 bits is encoded with the ½ rate convolutional code (identical to the one used for TCH/FS) defined by the polynomials:
G0 = 1 + D3 + D4
G1 = 1 + D + D3 + D4
This results in a block of 456 coded bits: {c(0),c(1),…,c(455)} defined by:
c(2k) = u(k) + u(k‑3) + u(k‑4)
c(2k+1) = u(k) + u(k‑1) + u(k‑3) + u(k‑4) for k = 0,1,…,227 ; u(k) = 0 for k < 0
4.1.4 Interleaving
The coded bits are reordered and interleaved according to the following rule:
i(B,j) = c(n,k) for k = 0,1,…,455
n = 0,1,…,N,N+1,…
B = B0 + 4n + (k mod 4)
j = 2((49k) mod 57) + ((k mod 8) div 4)
See table 1. The result of the reordering of bits is the same as given for a TCH/FS (subclause 3.1.3) as can be seen from the evaluation of the bit number‑index j, distributing the 456 bits over 4 blocks on even numbered bits and 4 blocks on odd numbered bits. The resulting 4 blocks are built by putting blocks with even numbered bits and blocks with odd numbered bits together into one block.
The block of coded data is interleaved "block rectangular" where a new data block starts every 4th block and is distributed over 4 blocks.
4.1.5 Mapping on a Burst
The mapping is given by the rule:
e(B,j) = i(B,j) and e(B,59+j) = i(B,57+j) for j = 0,1,…,56
and
e(B,57) = hl(B) and e(B,58) = hu(B)
The two bits labelled hl(B) and hu(B) on burst number B are flags used for indication of control channel signalling. They are set to "1" for a SACCH.
4.2 Fast associated control channel at full rate (FACCH/F)
4.2.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits. It is delivered on a burst mode.
4.2.2 Block code
The block encoding is done as specified for the SACCH in subclause 4.1.2.
4.2.3 Convolutional encoder
The convolutional encoding is done as specified for the SACCH in subclause 4.1.3.
4.2.4 Interleaving
The interleaving is done as specified for the TCH/FS in subclause 3.1.3.
4.2.5 Mapping on a Burst
A FACCH/F frame of 456 coded bits is mapped on 8 consecutive bursts as specified for the TCH/FS in subclause 3.1.4. As a FACCH is transmitted on bits which are stolen in a burst from the traffic channel, the even numbered bits in the first 4 bursts and the odd numbered bits of the last 4 bursts are stolen.
To indicate this to the receiving device the flags hl(B) and hu(B) have to be set according to the following rule:
hu(B) = 1 for the first 4 bursts (even numbered bits are stolen);
hl(B) = 1 for the last 4 bursts (odd numbered bits are stolen).
The consequences of this bitstealing by a FACCH/F is for a:
‑ speech channel (TCH/FS) and data channel (TCH/F2.4):
One full frame of data is stolen by the FACCH.
‑ Data channel (TCH/F14.4):
The bitstealing by a FACCH/F disturbs a maximum of 96 of the 456 coded bits generated from an input data block of 290 bits.
‑ Data channel (TCH/F9.6):
The bitstealing by a FACCH/F disturbs a maximum of 96 coded bits generated from an input frame of four data blocks. A maximum of 24 of the 114 coded bits resulting from one input data block of 60 bits may be disturbed.
‑ Data channel (TCH/F4.8):
The bit stealing by FACCH/F disturbs a maximum of 96 coded bits generated from an input frame of two data blocks. A maximum of 48 of the 228 coded bits resulting from one input data block of 60 bits may be disturbed.
NOTE: In the case of consecutive stolen frames, a number of bursts will have both the even and the odd bits stolen and both flags hu(B) and hl(B) must be set to 1.
4.3 Fast associated control channel at half rate (FACCH/H)
4.3.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits. It is delivered on a burst mode.
4.3.2 Block code
The block encoding is done as specified for the SACCH in subclause 4.1.2.
4.3.3 Convolutional encoder
The convolutional encoding is done as specified for the SACCH in subclause 4.1.3.
4.3.4 Interleaving
The coded bits are reordered and interleaved according to the following rule:
i(B,j) = c(n,k) for k = 0,1,…,455
n = 0,1,…,N,N+1,…
B = B0 + 4n + (k mod 8) ‑ 4((k mod 8) div 6)
j = 2((49k) mod 57) + ((k mod 8) div 4)
See table 1. The result of the reordering of bits is the same as given for a TCH/FS (subclause 3.1.3) as can be seen from the evaluation of the bit number‑index j, distributing the 456 bits over 4 blocks on even numbered bits and 4 blocks on odd numbered bits. The 2 last blocks with even numbered bits and the 2 last blocks with odd numbered bits are put together into 2 full middle blocks.
The block of coded data is interleaved "block diagonal" where a new data block starts every 4th block and is distributed over 6 blocks.
4.3.5 Mapping on a Burst
A FACCH/H frame of 456 coded bits is mapped on 6 consecutive bursts by the rule:
e(B,j) = i(B,j) and e(B,59+j) = i(B,57+j) for j = 0,1,…,56
and
e(B,57) = hl(B) and e(B,58) = hu(B)
As a FACCH/H is transmitted on bits which are stolen from the traffic channel, the even numbered bits of the first 2 bursts, all bits of the middle 2 bursts and the odd numbered bits of the last 2 bursts are stolen.
To indicate this to the receiving device the flags hl(B) and hu(B) have to be set according to the following rule:
hu(B) = 1 for the first 2 bursts (even numbered bits are stolen)
hu(B) = 1 and hl(B) = 1 for the middle 2 bursts (all bits are stolen)
hl(B) = 1 for the last 2 bursts (odd numbered bits are stolen)
The consequences of this bitstealing by a FACCH/H is for a:
‑ speech channel (TCH/HS):
two full consecutive speech frames are stolen by a FACCH/H.
‑ data channel (TCH/H4.8):
The bitstealing by FACCH/H disturbs a maximum of 96 coded bits generated from an input frame of four data blocks. A maximum of 24 out of the 114 coded bits resulting from one input data block of 60 bits may be disturbed.
‑ data channel (TCH/H2.4):
The bitstealing by FACCH/H disturbs a maximum of 96 coded bits generated from an input frame of four data blocks. A maximum of 24 out of the 114 coded bits resulting from one input data block of 36 bits may be disturbed.
NOTE: In the case of consecutive stolen frames, two overlapping bursts will have both the even and the odd numbered bits stolen and both flags hu(B) and hl(B) must be set to 1.
4.4 Broadcast control, Paging, Access grant, Notification and Cell broadcast channels (BCCH, PCH, AGCH, NCH, CBCH), CTS Paging and Access grant channels (CTSPCH, CTSAGCH)
The coding scheme used for the broadcast control , paging, access grant, notification and cell broadcast messages is the same as for the SACCH messages, specified in subclause 4.1. In CTS, the coding scheme used for the paging and access grant messages is also the same as for the SACCH messages, specified in subclause 4.1.
4.5 Stand‑alone dedicated control channel (SDCCH)
The coding scheme used for the dedicated control channel messages is the same as for SACCH messages, specified in subclause 4.1.
4.6 Random access channel (RACH)
Three coding schemes are specified for the burst carrying the random access uplink message:
the access burst containing 8 information bits,
the access burst containing 11 information bits and
the access burst containing 30 information bits.
The encoding of the access burst containing 8 information bits is as defined in subclause 4.6.1.
The encoding of the access burst containing 11 information bits is as defined in sub-clause 5.3.2 for the packet random access channel (PRACH, CPRACH and MPRACH).
The encoding of the access burst containing 30 information bits is as defined in sub-clause 4.6.2. It is used for the Multilateration Timing Advance procedure when the Extended Access Burst method is used (see 3GPP TS 43.059).
4.6.1 RACH carrying 8 information bits
The encoding of the access burst containing 8 information bits is defined as follows. It contains 8 information bits
d(0),d(1),…,d(7).
Six parity bits p(0),p(1),…,p(5) are defined in such a way that in GF(2) the binary polynomial:
d(0)D13 +…+ d(7)D6 + p(0)D5 +…+ p(5), when divided by D6 + D5 + D3 + D2 + D + 1 yields a remainder equal to D5 + D4 + D3 + D2 + D + 1.
The six bits of the BSIC, {B(0),B(1),…,B(5)}, of the BS to which the Random Access is intended, are added bitwise modulo 2 to the six parity bits, {p(0),p(1),…,p(5)}. This results in six colour bits, C(0) to C(5) defined as C(k) = b(k) + p(k) (k = 0 to 5) where:
b(0) = MSB of PLMN colour code
b(5) = LSB of BS colour code.
This defines {u(0),u(1),…, u(17)} by:
u(k) = d(k) for k = 0,1,…,7
u(k) = C(k‑8) for k = 8,9,…,13
u(k) = 0 for k = 14,15,16,17 (tail bits)
The bits {e(0),e(1),…, e(35)} are obtained by the same convolutional code of rate ½ as for TCH/FS, defined by the polynomials:
G0 = 1 + D3 + D4
G1 = 1 + D + D3 + D4
and with:
e(2k) = u(k) + u(k‑3) + u(k‑4)
e(2k+1) = u(k) + u(k‑1) + u(k‑3) + u(k‑4) for k = 0,1,…,17 ; u(k) = 0 for k < 0
4.6.2 (EC-)RACH carrying 30 information bits
In case of the Multilateration Timing Advance procedure when the Extended Access Burst method is used, indicated by the network, the mobile station first sends a random access message carrying 11 information bits, using the encoding for the access burst containing 11 bits, as specified in sub-clause 5.3.2, and after access grant by the network sends a subsequent random access message carrying 30 information bits as soon as possible after receiving the access grant while still using the principles for (EC-)RACH transmission opportunity selection described in 3GPP TS 44.018. The encoding of the 30 information bits is as given in the following sub-clauses.
4.6.2.1 Block constitution
The burst carrying the extended random access uplink message for connectionless Multilateration Positioning contains 30 information bits d(0),d(1),…,d(29). The first 11 bits d(0),…,d(10) are encoded in the same way as specified for the access burst containing 11 information bits in sub-clause 5.3.2 resulting in a block of 36 coded bits {e(0), e(1),…,e(35)}. The encoding of the remaining 19 information bits d(11),…,d(29) is specified in the following sub-clauses.
4.6.2.2 Parity bits
Six parity bits p(0),p(1),…,p(5) are defined in such a way that in GF(2) the binary polynomial:
d(11)D24 +…+ d(29)D6 + p(0)D5 +…+ p(5), when divided by D6 + D5 + D3 + D2 + D + 1 yields a remainder equal to D5 + D4 + D3 + D2 + D + 1.
4.6.2.3 Tail bits
Four tail bits are added to information bits and parity bits defining the bit sequence{u(0),u(1),…, u(28)} as follows:
u(k-11) = d(k) for k = 11,12,…,29
u(k+19) = p(k) for k = 0,…,5
u(k+25) = 0 for k = 0,1,2,3 (tail bits)
4.6.2.4 Convolutional code
The coded bits {c(0),c(1),…, c(57)} are obtained by the same convolutional code of rate ½ as for TCH/FS, defined by the polynomials:
G0 = 1 + D3 + D4
G1 = 1 + D + D3 + D4
and with:
c(2k) = u(k) + u(k‑3) + u(k‑4)
c(2k+1) = u(k) + u(k‑1) + u(k‑3) + u(k‑4) for k = 0,1,…,28 ; u(k) = 0 for k < 0
The code is punctured in such a way that the following coded bit:
c(57) is not transmitted.
This results in a block of 57 coded bits, {e(36),…,e(92)} with
e(k+36) = c(k) for k = 0,1,…,56
4.6.2.5 Burst mapping
Both data blocks {e(0),…,e(35)} and {e(36),…,e(92)} are mapped onto the Extended Access burst as specified in 3GPP TS 45.002.
4.7 Synchronization channel (SCH), Compact synchronization channel (CSCH), CTS Beacon and Access request channels (CTSBCH-SB, CTSARCH)
The burst carrying the synchronization information on the downlink BCCH, the downlink CPBCCH for Compact, and in CTS the information of the CTSBCH-SB and the access request message of the CTSARCH, has a different structure. It contains 25 information bits {d(0),d(1),…, d(24)}, 10 parity bits {p(0),p(1),…, p(9)} and 4 tail bits. The precise ordering of the information bits is given in 3GPP TS 44.018.
The ten parity bits {p(0),p(1),,…,p(9)} are defined in such a way that in GF(2) the binary polynomial:
d(0)D34 +…+ d(24)D10 + p(0)D9 +…+ p(9), when divided by:
D10 + D8 + D6 + D5 + D4 + D2 + 1, yields a remainder equal to:
D9 + D8 + D7 + D6 + D5 + D4 + D3 + D2 + D+ 1.
Thus the encoded bits {u(0),u(1),…,u(38)} are:
u(k) = d(k) for k = 0,1,…,24
u(k) = p(k‑25) for k = 25,26,…,34
u(k) = 0 for k = 35,36,37,38 (tail bits)
The bits {e(0),e(1),…, e(77)} are obtained by the same convolutional code of rate ½ as for TCH/FS, defined by the polynomials:
G0 = 1 + D3 + D4
G1 = 1 + D + D3 + D4
and with:
e(2k) = u(k) + u(k‑3) + u(k‑4)
e(2k+1) = u(k) + u(k‑1) + u(k‑3) + u(k‑4) for k = 0,1,….,38 ; u(k) = 0 for k < 0
4.7a Extended Coverage Synchronization channel (EC-SCH)
4.7a.1 Block constitution
The burst carrying the synchronization information on the downlink EC-SCH contains 30 information bits {d(0),d(1),…, d(29)}.
4.7a.2 Coding
The 30 information bits {d(0),d(1),…, d(29)} are encoded as follows:
a) Parity bits:
Ten parity bits {p(0),p(1),,…,p(9)} are defined in such a way that in GF(2) the binary polynomial:
d(0)D39 +…+ d(29)D10 + p(0)D9 +…+ p(9), when divided by:
D10 + D8 + D6 + D5 + D4 + D2 + 1, yields a remainder equal to:
D9 + D8 + D7 + D6 + D5 + D4 + D3 + D2 + D+ 1.
b) Tail bits:
Four tail bits equal to 0 are added to the information and parity bits, the results being a block of 44 bits {u(0),u(1),…,u(43)}:
u(k) = d(k) for k = 0,1,…,29
u(k) = p(k‑30) for k = 30,31,…,39
u(k) = 0 for k = 40,41,42,43 (tail bits)
c) Convolutional encoder:
This block of 44 bits {u(0),u(1),…,u(43)} is encoded with the same convolutional code of rate ½ as for TCH/FS, defined by the polynomials:
G0 = 1 + D3 + D4
G1 = 1 + D + D3 + D4
This results in a block of 88 coded bits {C(0),C(1),…,C(87)} defined by:
C(2k) = u(k) + u(k‑3) + u(k‑4)
C(2k+1) = u(k) + u(k‑1) + u(k‑3) + u(k‑4) for k = 0,1,….,43 ; u(k) = 0 for k < 0
The block is punctured such that the bits C(k), k=[0,10,19,29,39,48,58,68,77,87] are not transmitted, resulting in a block of 78 encoded bits {e(0),e(1),…, e(77)}.
4.7a.3 Blind physical layer transmission
The encoded bits e(j), j=0,…,77 are transmitted 28 times, generating the repeated bursts R(m,B,j)=e(j), m=0,…,27, B=0, j=0,…,77.
4.7a.4 Cyclic shift
The repeated bursts are cyclically shifted as:
R’(m,B,j) = R(m,B,(j + T2”) mod 78)
where T2” = (FN div 51) mod 4, i.e. it refers to the specific 51-multiframe FN, in which the burst will be sent in the set of four contiguous 51-multiframes as defined in TS 45.002 [8].
4.7a.5 Mapping onto a physical channel
Burst R’(m,B,j), is mapped onto burst B’ of the timeslot carrying the EC-SCH, where
B’ = m
NOTE: The burst number B’ denotes the relative transmission order of the bursts on the timeslot. The mapping to absolute TDMA frame number is specified in 3GPP TS 45.002 [8].
4.8 Access Burst on circuit switched channels other than RACH
The encoding of this burst is as defined in subclause 4.6 for the 8 bits access burst on the random access channel (RACH). The BSIC used shall be the BSIC of the BTS to which the burst is intended.
4.9 Access Bursts for uplink access on a channel used for VGCS or VBS
The encoding of this burst is as defined in subclause 4.6 for the 8 bits access burst on the RACH. The BSIC used by the Mobile Station shall be the BSIC indicated by network signalling, or if not thus provided, the last received BSIC on the SCH of the current cell.
4.10a Fast associated control channel at ECSD E-TCH/F (E-FACCH/F)
4.10a.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits. It is delivered on a burst mode.
4.10a.2 Block code
The block encoding is done as specified for the SACCH in subclause 4.1.2.
4.10a.3 Convolutional encoder
The convolutional encoding is done as specified for the SACCH in subclause 4.1.3.
4.10a.4 Interleaving
The interleaving is done as specified for the SACCH in subclause 4.1.4.
4.10a.5 Mapping on a Burst
A E-FACCH/F frame of 456 coded bits is mapped on 4 full consecutive bursts. As a E-FACCH/F is transmitted on bits, which are stolen in a burst from the ECSD traffic channel, the four full bursts are stolen.
The mapping on is given by the rule:
e(B,j)=i(B,j) and e(B,59+j)=i(B,57+j) for j=0,1,…,56
and
e(B,57)=hl(B) and e(B,58)=hu(B).
To indicate to the receiving device the flags hl(B) and hu(B) have to be set according to the following rule:
hu(B)=1 and hl(B)=1 for the all 4 bursts (4 full bursts are stolen).
The consequences of this bitstealing by a E-FACCH/F is for a:
– Data channel (E-TCH/F43.2)
The bitstealing by a E-FACCH/F disturbs a maximum of 288 of the 1368 coded bits generated from an input data block of 870 bits.
– Data channel (E-TCH/F32.0)
The bitstealing by a E-FACCH/F disturbs 464 of the 1392 coded bits generated from an input data block of 640 bits.
– Data channel (E-TCH/F28.8)
The bitstealing by a E-FACCH/F disturbs a maximum of 288 of the 1368 coded bits generated from an input data block of 580 bits.
4.10b Octal fast associated control channel at half rate (O-FACCH/H)
4.10b.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits. It is delivered on a burst mode.
4.10b.2 Block code
a) Parity bits:
The block of 184 information bits is protected by 40 extra bits used for error correction and detection. These bits are added to the 184 bits according to a shortened binary cyclic code (FIRE code) using the generator polynomial:
G(D)=(D23 + 1)(D17 + D3 + 1)
The encoding of the cyclic code is performed in a systematic form, which means that, in GF(2), the polynomial:
D(0)D223 + d(1)D222 +…+ d(183)D40 + p(0)D39 + p(1)D38 +…+ p(38)D + p(39)
where {p(0),p(1),…,p(39)} are the parity bits, when divided by g(D) yields a remainder equal to:
1 + D + D2 +… +D39.
b) Tail bits
Six tail bits equal to zero are added to the information and parity bits, the result being a block of 230 bits.
u(k) = d(k) for k = 0,1,…,183
u(k) = p(k-184) for k = 184,185,…,223
u(k) = 0 for k = 224,225,226,227,228,229 (tail bits)
4.10b.3 Convolutional encoder
This block of 230 bits is encoded with the rate 1/6 convolutional code defined by the polynomials:
G4 = 1 + D2 + D3 + D5 + D6
G4 = 1 + D2 + D3 + D5 + D6
G5 = 1 + D + D4 + D6
G5 = 1 + D + D4 + D6
G6 = 1 + D + D2 + D3 + D4 + D6
G7 = 1 + D + D2 + D3 + D6
This results in a block of 1380 encoded bits {C(0),C(1),…C(1379)} defined by
C(6k) = u(k) + u(k‑2) + u(k-3) + u(k‑5) + u(k-6)
C(6k+1) = u(k) + u(k‑2) + u(k-3) + u(k‑5) + u(k-6)
C(6k+2) = u(k) + u(k‑1) + u(k‑4) + u(k‑6)
C(6k+3) = u(k) + u(k‑1) + u(k‑4) + u(k‑6)
C(6k+4) = u(k) + u(k-1) + u(k-2) + u(k-3) + u(k-4) + u(k-6)
C(6k+5) = u(k) + u(k-1) + u(k-2) + u(k-3) + u(k-6) for k = 0,1,…,229 ; u(k) = 0 for k < 0
The code is punctured in such a way that the following coded bits:
{C(21+114k) for k=0,1,..,11} are not transmitted.
The result is a block of 1368 coded bits {c(0),c(1),…,c(1367)}.
4.10b.4 Reordering
The coded bits are reordered according to the following rule:
r(j) = c(k), for k = 0,1,…,1367
j = k div 36 + 38*(k mod 36)
NOTE: The reordering is a simple block interleaver: a 38 rows x 36 columns matrix which is filled in by row and read out by column.
4.10b.5 Interleaving
Before interleaving the reordered coded bits {r(0),r(1),…,r(1367)} are converted into 3-bit symbols {Rs(0),Rs(1),…,Rs(455)} according to Table 1 in 3GPP TS 45.004, the symbol Rs(k) depends on r(3k+2), r(3k+1), and r(3k) for k=0,1,…,455. The interleaving is done as specified for the FACCH at half rate in subclause 4.3.4. The difference is that the interleaving is done by symbols instead of single bits, reusing the existing interleaving tables.
4.10b.6 Mapping on a burst
As an O-FACCH is transmitted on symbols which are stolen in a burst from the traffic channel, the even numbered symbols in the first 2 bursts, all symbols in the middle 2 bursts, and the odd numbered symbols in the last 2 bursts are stolen.
The mapping is given by the rule:
E(B,j) = I(B,j) and E(B,59+j) = I(B,57+j) for j=0,1,…,56
and
E(B,57) = HL(B) and E(B,58) = HU(B).
To indicate the stealing to the receiving device the symbols HL(B) and HU(B) have to be set according to the following rule:
HU(B) = {1,1,1} for the first two bursts (even numbered symbols are stolen)
HU(B) = {1,1,1} and HL(B) = {1,1,1} for the middle two bursts (all symbols are stolen)
HL(B) = {1,1,1} for the last two burts (odd numbered symbols are stolen).
As a consequence, two full consecutive speech frames of an O-TCH/AHS are stolen by an O-FACCH/H.
4.10c Octal fast associated control channel at full rate (O-FACCH/F)
4.10c.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits. It is delivered on a burst mode.
4.10c.2 Block code
The block encoding is done as specified for the O-FACCH/H in subclause 4.10b.2
4.10c.3 Convolutional encoder
The convolutional encoding is done as specified for the O-FACCH/H in subclause 4.10b.3.
4.10c.4 Reordering
The reordering is done as specified for the O-FACCH/H in subclause 4.10b.4.
4.10c.5 Interleaving
Before interleaving the reordered coded bits {r(0),r(1),…,r(1367)} are converted into 3-bit symbols {Rs(0),Rs(1),…,Rs(455)} according to Table 1 in 3GPP TS 45.004, the symbol Rs(k) depends on r(3k+2), r(3k+1), and r(3k) for k=0,1,…,455. The interleaving is done as specified for the FACCH at full rate in subclause 4.2.4. The difference is that the interleaving is done by symbols instead of single bits, reusing the existing interleaving tables.
4.10c.6 Mapping on a burst
As an O-FACCH is transmitted on symbols which are stolen in a burst from the traffic channel, the even numbered symbols in the first four bursts and the odd numbered symbols in the last four bursts are stolen.
The mapping is given by the rule:
E(B,j) = I(B,j) and E(B,59+j) = I(B,57+j) for j=0,1,…,56
and
E(B,57) = HL(B) and E(B,58) = HU(B).
To indicate the stealing to the receiving device the symbols HL(B) and HU(B) have to be set according to the following rule:
HU(B) = {1,1,1} for the first four bursts (even numbered symbols are stolen)
HL(B) = {1,1,1} for the last four burts (odd numbered symbols are stolen).
As a consequence, one speech frame of an O-TCH/F is stolen by an O-FACCH/F.
4.11 Slow associated control channel with embedded enhanced power control (SACCH/TP)
4.11.1 Block constitution
The message delivered to the encoder has a fixed size of 184 information bits {d(0),d(1),…,d(183)}. It is delivered on a burst mode.
4.11.2 Block code
a) Parity bits:
Eighteen parity bits p(0),p(1),…,p(17) are defined in such a way that in GF(2) the binary polynomial:
d(0)D201 +…+ d(183)D18 + p(0)D17+…+ p(17), when divided by:
D18 + D17 + D14 + D13 + D11 + D10 + D8 + D7 + D6 + D3 + D2 + 1, yields a remainder equal to:
D17 + D16 + D15 + D14 + D13 + D12 + D11 + D10 + D9 + D8 + D7 + D6 + D5 + D4 + D3 + D2 + D+1.
b) Tail bits
Six tail bits equal to 0 are added to the information and parity bits, the result being a block of 208 bits.
u(k) = d(k) for k= 0,1,…,183
u(k) = p(k‑184) for k = 184,185,…,201
u(k) = 0 for k = 202,203,204,205,206,207 (tail bits)
4.11.3 Convolutional encoder
This block of 208 bits is encoded with the ½ rate convolutional code defined by the polynomials:
G4 = 1 + D2 + D3 + D5 + D6
G7= 1 + D + D2 + D3 + D6
This results in a block of 416 coded bits: {c'(0),c'(1),…,c'(415)} defined by:
c'(2k) = u(k) + u(k-2) + u(k‑3) + u(k-5) + u(k-6)
c'(2k+1) = u(k) + u(k‑1) + u(k-2) + u(k‑3) + u(k-6) for k = 0,1,…,207 ; u(k) = 0 for k < 0
4.11.4 Dummy bits insertion
Forty dummy bits are first inserted to the coded bits according to the following rule:
c(k) = c'(k) for k = 0,1,2
c(k) = c'(k-1) for k = 4,…,31
c(k) = c'(k-2) for k = 33,…,39
c(k) = c'(k-3) for k = 41,…,45
c(k) = c'(k-5) for k = 48,…,67
c(k) = c'(k-6) for k = 69,…,88
c(k) = c'(k-7) for k = 90,…,95
c(k) = c'(k-9) for k = 98,…,102
c(k) = c'(k-10) for k = 104,…,123
c(k) = c'(k-12) for k = 126,…,131
c(k) = c'(k-13) for k = 133,…,145
c(k) = c'(k-14) for k = 147,…,152
c(k) = c'(k-16) for k = 155,…,180
c(k) = c'(k-18) for k = 183,…,188
c(k) = c'(k-19) for k = 190,…,202
c(k) = c'(k-20) for k = 204,…,209
c(k) = c'(k-22) for k = 212,…,231
c(k) = c'(k-23) for k = 233,…,237
c(k) = c'(k-25) for k = 240,…,245
c(k) = c'(k-26) for k = 247,…,266
c(k) = c'(k-27) for k = 268,…,287
c(k) = c'(k-29) for k = 290,…,294
c(k) = c'(k-30) for k = 296,…,302
c(k) = c'(k-31) for k = 304,…,331
c(k) = c'(k-32) for k = 333,…,344
c(k) = c'(k-34) for k = 347,…,387
c(k) = c'(k-36) for k = 390,…,401
c(k) = c'(k-38) for k = 404,…,444
c(k) = c'(k-40) for k = 447,…,455
c(k) = 0 for k = 3, 32, 40, 46 , 47, 68, 89, 96, 97, 103, 124, 125, 132, 146, 153, 154, 181, 182, 189, 203, 210, 211, 232, 238, 239, 246, 267, 288, 289, 295, 303, 332, 345, 346, 388, 389, 402, 403, 445, 446
4.11.5 Interleaving
The interleaving is done as specified for the SACCH in subclause 4.1.4.
4.11.6 Mapping on a Burst
The mapping is given by the rule:
e(B,j) = i(B,j) and e(B,59+j) = i(B,57+j) for j = 0,1,…,56
NOTE: The bits e(B,57) and e(B,58) on burst number B do not need to be set as they are used by the EPCCH (see subclause 4.12).
4.12 Enhanced power control channel (EPCCH)
4.12.1 Block code
The EPCCH message delivered to the encoder on every 120ms, and has a fixed size of 3 information bits {pm(0), pm(1), pm(2)}. The contents of the bits are defined in 3GPP TS 45.008 for both uplink and downlink.
The EPCCH information bits {pm(n,0),pm(n,1),pm(n,2)} are coded into 12 bits
pb(B,k), k = 0,1,…11 according to the following table (identical to the one used for USF in section 5.1.4.2):
|
pm(n,0),pm(n,1),pm(n,2) |
pb(B,0),…, pb(B,11) |
|
000 |
000 000 000 000 |
|
001 |
000 011 011 101 |
|
010 |
001 101 110 110 |
|
011 |
001 110 101 011 |
|
100 |
110 100 001 011 |
|
101 |
110 111 010 110 |
|
110 |
111 001 111 101 |
|
111 |
111 010 100 000 |
4.12.2 Mapping on a Burst
The EPCCH message is mapped on the SACCH/TP burst.
The mapping is given by the rule:
e(B,j) = pb(B,k) for respectively j = 44, 47, 50, 53, 55, 57, 58, 60, 62, 65, 68, 71, and k= 0,1, …, 11