## 5.3a Extended coverage random access channel (EC-RACH/M)

3GPP45.003GSM/EDGE Channel codingRelease 17TS

### 5.3a.0 General

Channel encoding for the random access message in EC operation containing 11 information bits is depicted in the following sub-clauses 5.3a.1 to 5.3a.4, except for EC-RACH/66 (for ESAB format) and EC-RACH/132 (for EDAB format) the channel encoding are specified in clause 5.3a.6 and 5.3a.7. Sub-clause 5.3a.5 deals with the channel encoding for the random access message in EC operation containing 30 information bits.

### 5.3a.1 Block constitution

The message delivered to the encoder has a fixed size of 11 information bits {d(0),d(1),…,d(10)}.

### 5.3a.2 Coding

The message is encoded as for the 11 information bit access defined in subclause 5.3.2, resulting in a block of 36 coded bits {e(0), e(1),…,e(35)}.

### 5.3a.3 Blind physical layer transmissions

The block is transmitted M times, where M=1, 4, 16 or 48 for 1 TS EC-RACH and M=4, 16 or 48 for 2 TS EC-RACH, resulting in the repeated bursts R(m,B,j)=e(j) for m=0,…,M-1, B=0 and j=0,…,35.

### 5.3a.4 Mapping onto physical channel(s)

#### 5.3a.4.1 1 TS EC-RACH

Burst R(m,B,j), B=0, j=0…,35, is mapped onto burst B’ of the timeslot carrying the EC-RACH, 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].

#### 5.3a.4.2 2 TS EC-RACH

Burst R(m,B,j), B=0, j=0…,35, is mapped onto burst B’ of timeslot number tn of the timeslots carrying the EC-RACH, where

B’ = m div 2

tn = m mod 2

NOTE 1: 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].

NOTE 2: tn denotes the relative timeslot number within the timeslot pair on which the EC-RACH is mapped. The absolute timeslot number depends on the configuration, see 3GPP TS 44.018 [4].

### 5.3a.5 EC-RACH carrying 30 information bits

In case of performing the Multilateration Timing Advance procedure using the Extended Access Burst method in EC operation, i.e. the mobile station has selected Coverage Class 1 for the uplink and the downlink, the MS sends a random access message carrying 11 information bits using the encoding according to the above sub-clauses, and after access grant by the network sends a subsequent random access message carrying 30 information bits. The encoding of the 30 information bits follows the one for (EC-)RACH specified in subclause 4.6.2.

### 5.3a.6 Extended coverage random access channel (EC-RACH/66)

#### 5.3a.6.0 General

If ESAB format (see 3GPP TS 45.002) is used for EC-RACH in CC5 operation the channel coding, blind physical layer transmissions and mapping onto physical channels are depicted in the subclause 5.3a.6.

Channel encoding, blind physical layer transmissions and mapping onto physical channels for the random access channel EC-RACH/66 used for CC5 in EC operation is depicted in the following sub-clauses 5.3a.6.1 to 5.3a.6.6.

#### 5.3a.6.1 Block constitution

The message delivered to the encoder has a fixed size of 11 information bits {d(0),d(1),…,d(10)}.

#### 5.3a.6.2 Parity bits

Six parity bits are added as defined in subclause 5.3.2.2

#### 5.3a.6.3 Addition of BSIC

The first six bits of the BSIC, {b(0),b(1),…,b(5)}, are added bitwise modulo 2 to the six parity bits while the last three bits of the BSIC {b(6),b(7),b(8)} are added bitwise modulo 2 to the three last information bits d(8), d(9) and d(10). The bitwise modulo 2 operation results in nine colour bits, C(0) to C(8), defined as C(k) = b(k) + p(k) (for k = 0 to 5) and C(k) = b(k) + d(k+2) (for k = 6 to 8) where:

b(0) = MSB of PLMN colour code

b(8) = LSB of Radio frequency colour code.

This defines a block of 17 bits {u(0),u(1),…, u(16)} by:

u(k) = d(k) for k = 0,1,…,7

u(k) = C(k-2) for k = 8,9,10

u(k) = C(k‑11) for k = 11,12,…,16

#### 5.3a.6.4 Tail biting Convolutional code

The six last bits are added before the block of 17 bits, the result being a block of 23 bits {c(‑6),…,c(0),c(1),…,c(17-1)} with six negative indices:

c(k) = u(23+k) for k = -6,…,-1

c(k) = u(k) for k = 0, 1,…,17-1

The block of 23 bits is encoded with 1/6 rate convolutional mother code defined by the polynomials:

G4 = 1 + D2 + D3 + D5 + D6

G4 = 1 + D2 + D3 + D5 + D6

G7= 1 + D + D2 + D3 + D6

G5 = 1 + D + D4 + D6

G6 = 1 + D + D2 + D3 + D4 + D6

G6 = 1 + D + D2 + D3 + D4 + D6

This results in a block of 17*6 coded bits {e(0), e(1),…,e(101)} defined by:

e(6k) = c(k) + c(k‑2) + c(k‑3) + c(k‑5) + c(k‑6)

e(6k+1) = c(k) + c(k‑2) + c(k‑3) + c(k‑5) + c(k‑6)

e(6k+2) = c(k) + c(k‑1) + c(k‑2) + c(k‑3) + c(k‑6)

e(6k+3) = c(k) + c(k‑1) + c(k‑4) + c(k‑6)

e(6k+4) = c(k) + c(k‑1) + c(k‑2) + c(k‑3) + c(k‑4) + c(k‑6)

e(6k+5) = c(k) + c(k‑1) + c(k‑2) + c(k‑3) + c(k‑4) + c(k‑6) for k = 0,1,…,16

#### 5.3a.6.5 Blind physical layer transmissions

The block is transmitted M times, where M=1, 4, 16 or 48 for 1 TS EC-RACH, M=4, 16 or 48 for 2 TS EC-RACH, resulting in the repeated bursts R(m,B,j)=e(j) for m=0,…,M-1, B=0 and j=0,…,35, and M=66 for EC-RACH CC5 using ESAB burst, resulting in the repeated ESAB bursts R(m,B,j)=e(j) for m=0,…,65, B=0 and j=0,…,101.

#### 5.3a.6.6 Mapping onto physical channel(s)

For EC-RACH CC5/66, burst R(m,B,j), B=0, j=0…,101, is mapped onto ESAB burst B’’ on timeslot pair tn’ carrying the EC-RACH CC5, where

B’’ = m

NOTE 3: The burst number B’’ denotes the relative transmission order of the ESAB bursts on 2 timeslots. The mapping to absolute TDMA frame number is specified in 3GPP TS 45.002 [8].

NOTE 4: tn’ denotes the relative timeslot pair number on which the EC-RACH CC5 is mapped. The absolute timeslot pair depends on the configuration, see 3GPP TS 44.018 [4].

### 5.3a.7 Extended coverage random access channel (EC-RACH/132)

#### 5.3a.7.0 General

If EDAB format (see 3GPP TS 45.002) is used for EC-RACH in CC5 operation the channel coding, blind physical layer transmissions and mapping onto physical channels are depicted in the subclause 5.3a.7.

Channel encoding, blind physical layer transmissions and mapping onto physical channels for the random access channel EC-RACH/132 used for CC5 in EC operation is depicted in the following sub-clauses 5.3a.6.1 to 5.3a.6.6.

#### 5.3a.7.1 Block constitution

The message delivered to the encoder has a fixed size of 11 information bits {d(0),d(1),…,d(10)}.

#### 5.3a.7.2 Parity bits

Six parity bits are added as defined in subclause 5.3.2.2

#### 5.3a.7.3 Addition of BSIC

9 bits of BSIC information is added over 6 parity bits and 3 data bits as defined in subclause 5.3.2.3.

#### 5.3a.7.4 Convolutional code

The coded bits {c(0),c(1),…, c(41)} 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,…,20 ; u(k) = 0 for k < 0

The code is punctured in such a way that the following coded bits:

[c(0), c(3), c(7), c(12), c(14), c(17), c(24), c(27), c(31), c(34), c(39), c(41)] are not transmitted.

This results in a block of 30 coded bits, {e(0), e(1),…,e(29)}.

#### 5.3a.7.5 Blind physical layer transmissions

The block of encoded data is transmitted 264 times using the Segmented AB for the 2 TS EC-RACH format (see 3GPP TS 45.002[8]). The first burst with normal burst size carries 3 instances of the encoded data block and the second burst with access burst size carries one instance of the encoded data block. The bursts are transmitted in a timeslot pair which is repeated over 66 TDMA frames forming 132 bursts in total.

#### 5.3a.7.6 Mapping onto physical channel(s)

The data block {e(0),…,e(29)} is mapped onto the Segmented AB, repeated over 66 TDMA frames in total, as specified in 3GPP TS 45.002[8].

For tn = TN mod 2 = 0, the data block {e(0), e(1),…,e(29)} is mapped 3 times on the burst with normal burst size.

For tn = TN mod 2 = 1, the data block {e(0), e(1),…,e(29)} is mapped once on the burst with access burst size.

NOTE : tn denotes the relative timeslot number within the timeslot pair on which the EC-RACH is mapped. The absolute timeslot number depends on the configuration, see 3GPP TS 44.018 [4].