6
⁢
4

.

The number K_tof bits contained in the to-be-encoded bit sequence in the retransmitted data block may be determined by the bit polarization channel capacity of the first-transmission data block, the bit polarization channel capacity of the retransmitted data block, and the number of bits in the to-be-transmitted information bit sequence. Illustratively, K_tmay be calculated as follows:

K
t

=

C
t

∑

r
=
1

t

C
r

·

K
1

t denotes that the to-be-transmitted data block is a data block transmitted for the tth time (or retransmitted for the (t−1)th time). t is a positive integer. If the current data block is the first-transmission data block, then t=1; and if the current data block is a retransmitted data block, then t≥2. C_rdenotes the capacity value of the data block transmitted for the rth time. The capacity C₁of the first-transmission data block is a function of the modulation order, the length M₁of the first-transmission data block, the length M₂of the retransmitted data block, the bit polarization channel capacity I_iof the first-transmission data block, and I_i⁺. K₁denotes the number of bits in the to-be-transmitted information bit sequence. Illustratively, the capacity C₁of the first-transmission data block may be calculated as follows:

C
1

=

{

M
t

m

⁢

∑

i
=
1

m

I
+

+

M
1

-

M
t

m

⁢

∑

i
=
1

m

I
i

,

if
⁢

M
1

≥

M
t

M
1

m

⁢

∑

i
=
1

m

I
+

,

if
⁢

M
1

<

M
t

Illustratively, the capacity C_t(t≥2) of the retransmitted data block may be calculated as follows:

C
t

=

{

M
t

m

⁢

∑

i
=
1

m

I
i

-

,

if
⁢

M
1

≥

M
t

M
1

m

⁢

∑

i
=
1

m

I
-

+

M
t

-

M
1

m

⁢

∑

i
=
1

m

I
i
′

,

if
⁢

M
1

<

M
t

M_tdenotes the length of the data block transmitted for the tth time. I_iand I′_idenote the polarization channel capacity of the ith group of bits of the first-transmission data block and the polarization channel capacity of the ith group of bits of a retransmitted data block respectively. I_i⁺ and I_i⁻ denote the bit polarization channel capacity of the ith group of polar-coded bits of the first-transmission data block and the bit polarization channel capacity of the ith group of polar-coded bits of a retransmitted data block respectively.

In an embodiment, selecting K_tbits from the to-be-transmitted information bit sequence may include selecting K_tinformation bits having the lowest reliability from the previously transmitted (t−1) data blocks. In this embodiment, the reliability of information bits may be determined in the following two modes: The first mode is to determine the reliability of information bits according to bit polarization channel capacity. That is, the reliability is high when the capacity is high, and the reliability is low when the capacity is low. The second mode is to determine the reliability of information bits according to the positions of bit indexes in a polar code reliability sequence. Illustratively, in 5G New Radio (5G NR), the reliability of information bits may be determined according to a polar sequence. The polar sequence is to sort bit indexes in order of reliability from low to high. That is, the reliability of a bit corresponding to an index value earlier in the polar sequence is lower than the reliability of a bit corresponding to an index value later in the polar sequence.

In this embodiment, if t=2, that is, if the current data block is a data block transmitted for the second time, K₂bits having the lowest reliability are selected from the information bit sequence of the first-transmission data block. The reliability ranking of information bits in the first-transmission data block is indicated by the polar code reliability sequence of the first-transmission data block. If t>2, that is, if the current data block is a data block transmitted for the third time or later, K_j^t-1−K_jⁱbits having the lowest reliability are selected from the information bit sequence of (t−1) transmitted data blocks to form the information bit sequence (whose length is K_tbits) of a data block transmitted for the tth time. j is a positive integer. j=1, 2, . . . , t−1. K_j^tdenotes the number of equivalent information bits of the data block transmitted for the jth time after the data block has been transmitted t times. Illustratively, K_j^tmay be calculated as follows:

K
j
t

=

C
i

∑

r
=
1

t

C
r

·

K
1

Similarly, K_j^t-1denotes the number of equivalent information bits of the data block transmitted for the jth time after the data block has been transmitted (t−1) times. Illustratively, K_j^t-1may be calculated as follows:

K
j

t
-
1

=

C
i

∑

r
=
1

t
-
1

C
r

·

K
1

FIG. 4 is a diagram illustrating polar coding of retransmitted data blocks according to an embodiment of the present application. As shown in FIG. 4, polar-coding the to-be-coded bit sequence of the retransmitted data block includes selecting K_tbit positions having the highest reliability from transmission bit positions of the retransmitted data block to serve as to-be-coded information bit positions of the retransmitted data block; copying the to-be-coded bit sequence composed of the K_tbits to the to-be-coded information bit positions of the retransmitted data block respectively to obtain a to-be-coded bit sequence of the retransmitted data block; and multiplying the to-be-coded bit sequence by the coding matrix of the polar code to obtain the coded bit sequence.

In an embodiment, the transmission bit positions of the retransmitted data block does not include punctured bit positions or shortened bit positions.

In an embodiment, if the length of the coded bit sequence is not equal to M₂, the coded bit sequence is punctured, shortened, or repeated to form a rate-matched bit sequence. FIG. 2 uses the rate matching mode—puncturing. FIG. 3 uses the rate matching mode—shortening.

Illustratively, if t=2, that is, if the current data block is a data block transmitted for the second time, then after the number K₂(that is, the first number) of bits contained in the to-be-coded bit sequence of the retransmitted data block is calculated using the preceding method, the subchannels of the retransmitted data block are sorted using the polar code reliability sequence (that is, the sequence obtained by determination of reliability by using the polar sequence in the previous embodiment) of 5G NR, and K₂bit positions having the highest reliability are selected from the transmission bit positions not including punctured bit positions or shortened bit positions to serve as to-be-coded information bit positions of the retransmitted data block; K₂bit positions having the lowest reliability in the information bit positions of the first-transmission data block are copied to to-be-coded information bit positions (that is, K₂information bit positions) of the retransmitted data block, and other bit positions in the to-be-coded bit sequence are configured as frozen bit positions; and then the to-be-coded bit sequence is multiplied by the coding matrix of the polar code to obtain the coded bit sequence. If the length L₂of the coded bit sequence is not equal to M₂, the coded bit sequence is punctured or shortened by (L₂−M₂) bits to obtain a rate-matched coded sequence.

Illustratively, if t>2, that is, if the current data block is a data block transmitted for the third time or later, then after the number K_t(that is, the first number) of bits contained in the to-be-coded bit sequence of the retransmitted data block is calculated using the preceding method, the subchannels of the retransmitted data block are sorted using the polar code reliability sequence (that is, the sequence obtained by determination of reliability by using the polar sequence in the previous embodiment) of 5G NR, and K_tbit positions having the highest reliability are selected from the transmission bit positions not including punctured bit positions or shortened bit positions to serve as to-be-coded information bit positions of the retransmitted data block; K_j^t-1−K_j^tbits having the lowest reliability in the information bit positions of the (t−1) transmitted data blocks to form K_tinformation bits of the data block transmitted for the tth time, the K_tinformation bits are copied to K_tinformation bit positions of the retransmitted data block, and other bit positions in the to-be-coded bit sequence are configured as frozen bit positions; and then the to-be-coded bit sequence is multiplied by the coding matrix of the polar code to obtain the coded bit sequence. If the length L_tof the coded bit sequence is not equal to M_t, the coded bit sequence is punctured or shortened by (L_t−M_t) bits to obtain a rate-matched coded sequence.

As shown in FIG. 2, combining the coded retransmitted data block with the coded first-transmission data block includes bit-interleaving the polar-coded bit sequence (including the rate-matched bit sequence) of the first-transmission data block and the polar-coded bit sequence (including the rate-matched bit sequence) of the retransmitted data block separately to obtain an interleaved bit sequence; splitting the interleaved bit sequence into m bit subsequences each having a length of/Wm; and combining the m bit subsequences of the retransmitted data block with the m bit subsequences of the first-transmission data block separately to obtain the current to-be-transmitted data block.

m denotes the number of groups of bit polarization channels. m may be equal to the modulation order or half of the modulation order of the digital baseband modulation of the first transmission or retransmission.

Bit interleaving refers to changing the sort order of some or all bits in the first-transmission data block and the retransmitted data block. In this embodiment, different bit interleaving patterns may be used for the first-transmission data block and the retransmitted data block.

Combining m bit subsequences of the retransmitted data block with m bit subsequences of the first-transmission data block means that when M₁≥M_t, bitwise exclusive OR (or modulo-two addition) of corresponding bits is performed on m bit subsequences having a length of M_t/m in the retransmitted data block and the last M_t/m bits in m bit subsequences having a length of M_t/m in the first-transmission data block; and when M₁<M_t, bitwise exclusive OR (or modulo-two addition) of corresponding bits is performed on the last M_t/m bits in m bit subsequences having a length of M_t/m in the retransmitted data block and m bit subsequences having a length of M₁/m in the first-transmission data block. M₁is the length of the first-transmission data block. M_tis the length of the retransmitted data block.

In an embodiment, performing digital baseband modulation on the current to-be-transmitted data block means that when the number m of groups of bit polarization channels is equal to the modulation order, one bit is taken from each of the m bit subsequences of the current to-be-transmitted data block to form M_t/m bit groups composed of m bits, and m-order digital baseband modulation is performed on the bit groups to obtain M_t/m digital baseband modulated symbols; and when the number m of groups of bit polarization channels is equal to half of the modulation order, two bits are taken from each of the m bit subsequences of the current to-be-transmitted data block to form M_t/(2*m) bit groups composed of 2*m bits, and 2*m-order digital baseband modulation is performed on the bit groups to obtain M_t/(2*m) digital baseband modulated symbols.

Commonly used digital baseband modulation modes include, but are not limited to, binary phase-shift keying (BPSK), QPSK, 16 quadrature amplitude modulation (QAM), 64 QAM, 256 QAM, and 1024 QAM, whose modulation orders are 1, 2, 4, 6, 8 and 10 respectively.

In an embodiment, the BIPCM-HARQ scheme in this embodiment of the present application and the polar-coded HARQ scheme in the related art are different in terms of structure, coding, and modulation. In the BIPCM framework, each modulated symbol corresponds to m bit channels having different reliabilities after being demodulated, where m is S-ary high-order modulation order. The BIPCM-HARQ scheme in this embodiment of the present application can change different mother code lengths and any rate matching scheme in each transmission. For the tth transmission, polar coding is performed independently. Then the coded block of the tth time is rate-adapted to obtain a rate-adapted binary bit vector having a length of M_t, and the rate-adapted binary vector is bit-interleaved, where M_tis the code length of the tth transmission. Then in the (S=2m) high-order modulation, the tth randomly-interleaved binary bit vector is divided into m groups of bit vectors having a length of M_t/m according to different reliabilities of demodulated bit channels. Finally, modulo-two addition is performed on the m groups of bit vectors each having a length of M₁/m in the tth transmission and the last M_t/m bits of the randomly-interleaved m groups of bit vectors each having a length of M₁/m in the first transmission separately so that inter-block polarization is completed to obtain binary code words of the tth-transmission M_tbits; and modulation is performed to obtain the tth-transmission M_tcode words.

FIG. 2 and FIG. 3 illustrates a puncturing-based-BIPCM-HARQ scheme in two transmissions and a shortening-based-BIPCM-HARQ scheme in two transmissions respectively.

Construction of a polar coding HARQ scheme in the related art is based on GA. In view that construction based on GA incurs rather complex online real-time calculation that is not suitable for a practical communication system, the present application proposes a BIPCM-HARQ scheme. The BIPCM-HARQ scheme of the present application may use a 5G NR polar code bit channel reliability sequence. The 5G NR polar code bit channel reliability sequence is a construction sequence independent of a channel parameter. The 5G NR polar code bit channel reliability sequence is a fixed sequence that can be used in sorting bit channels as long as the code length of a polar code is provided, omitting problems including channel type and channel quality.

In a BIPCM framework, a multi-ary input channel is decomposed into m parallel modulated bit subchannels having different reliabilities. I_i(1≤i≤m) denotes the channel capacity of m parallel modulated bit subchannels having different reliabilities. I_i⁻ and I_i⁺ are the channel capacity of the polar-coded retransmitted code block and the channel capacity of the polar-coded first-transmission code block respectively. If the channel is a binary erasure channel (BEC), I_i⁻ and I_i⁺ are calculated as follows:

{

I
i
-

=

I
i
2

I
i
+

=

2
·

I
i

-

I
i
2

If the channel is an additive white Gaussian noise (AWGN) channel, I_i⁻ and I_i⁺ are calculated as follows:

{

I
i
-

=

I
i
2

+
δ

I
i
+

=

2
·

I
i

-

I
i
2

-
δ

Here

δ
=

-

|

I
i

-
0.5

|

3
⁢
2

+

1

6
⁢
4

.

It is assumed that K₁denotes the information bit length of the first-transmission code block at the time of the first transmission, K₁²and K₂denote the information bit length of the first-transmission code block and the information bit length of the retransmitted code block respectively after retransmission, and M₁and M₂denote the transmission bit length of the first-transmission code block and the transmission bit length of the retransmitted code block respectively. Here M₁≥M₂. Under the condition that a code length is limited, the information bit lengths of the two transmitted code blocks are allocated proportionally according to the channel capacity. More information bits should be allocated to the transmitted block having a larger channel capacity. After one time of block polarization, the total channel capacity of the first-transmission code block is

C
1

=

M
2

m

⁢

∑

i
=
1

m

I
i
+

+

M
1

-

M
2

m

⁢

∑

i
=
1

m

I
i

,

and the total channel capacity of the retransmitted code block is

C
2

=

M
2

m

⁢

∑

i
=
1

m

I
i
-

.

The ratio of C1 to C2 varies with I_i. For the sake of the generality of a HARQ general structure, it is set that

1
m

⁢

∑

i
=
1

m

I
i

=

K
1

M
1

+

M
2

.

The total information bit length K₁is allocated proportionally.

K
1
2

=

C
1

C
1

+

C
2

·

K
1

,

K
2

=

C
2

C
1

+

C
2

·

K
1

.

The information bit length of the retransmitted code block

K
2

=

M
2

m

⁢

∑

i
=
1

m

I
i
-

can be obtained. Here

1
m

⁢

∑

i
=
1

m

I
i

=

K
1

M
1

+

M
2

.

The information bit length K₁²=K₁−K₂of the first-transmission code block after retransmission can be obtained.

If the number of transmissions is t (t>2), the total channel capacity of each transmitted code block is calculated according to the inter-block polarization of multiple transmitted code blocks. K₁information bits are allocated proportionally to each transmitted block according to the channel capacity of each transmitted code block. It is assumed that K_i^t(i≤t) denotes the information bit length of the ith transmitted code block in the tth transmission, and M_i(i≤t) denotes the transmission bit length of the ith transmitted code block. Here M_i≥M_j(i≤j). In the tth transmission, the information bit length K_i^t(i≤t) of each transmitted code block can be calculated. When i=t, it is defined that K_t^t=K_t. For the sake of the generality of a HARQ general structure, it is set that

1
m

⁢

∑

i
=
1

m

I
i

=

K
1

∑

i
=
1

t

⁢

M
i

.

In this embodiment of the present application, when the code rate is K₁/M₁≤7/16, a puncturing-based-BIPCM-HARQ scheme is used; and when the code rate is K₁/M₁≤, 7/16, a shortening-based-BIPCM-HARQ scheme is used.

In the first transmission, subchannels of the first-transmission code block are sorted using a 5G NR standard sequence, and K_tbits having the highest reliability are selected from the transmission bits not including punctured bits or shortened bits to serve as information bits for coding. If decoding failure occurs on the code blocks transmitted for the first time, the code blocks need to be retransmitted. At the time of retransmission, if the length of the retransmitted code block is M₂, the retransmission information bit length M₂is determined using the preceding method. After the information bit length M₂of the retransmitted code block is obtained, subchannels of the retransmitted code block are sorted using a 5G NR standard sequence, and K₂bits having the highest reliability are selected from the transmission bits not including punctured bits or shortened bits to serve as information bits of the retransmitted code block. Finally, K₂information bits having the lowest reliability in the information bits of the first-transmission code block are copied to K₂bits having the highest reliability of the second code block. They serve as dynamic frozen bits and information bits of the retransmitted code block respectively. A one-to-one parity check relationship is established between them.

If the number of transmissions is t(t>2), the information bit length K_i^t(i≤t) of each code block in the tth transmission is calculated using the preceding scheme. Then subchannels of the tth-transmission code block are sorted using a 5G NR standard sequence, and subchannel indicators of K_iⁱbits having the highest reliability are selected from the transmission bits of the tth transmitted code block not including punctured bits or shortened bits to serve as the information bit set A_tof the tth transmitted code block. In the ith transmitted code block, subchannel indicators of K_i^t-1−K_i^t(i≤t−1) bits having the lowest reliability are selected from the remaining K_i^t-1(i≤t−1) information bits to serve as the dynamic frozen bit set D_i^tof the ith transmitted code block in the tth transmission. Information about the dynamic frozen bit set D_i^tof the ith transmitted code block is copied to the information bit set A_tof the tth transmitted code block. A one-to-one parity check relationship is established between them.

If the number of transmissions is t (t>2), the information bit length K_i^t(i≤t) of each code block in the tth transmission is calculated using the preceding scheme. Then subchannels of the tth-transmission code block are sorted using a 5G NR standard sequence, and subchannel indicators of K_i^tbits having the highest reliability are selected from the transmission bits of the tth transmitted code block not including punctured bits or shortened bits to serve as the information bit set A_tof the tth transmitted code block. In the ith transmitted code block, subchannel indicators of K_i^t-1−K_i^t(i≤t−1) bits having the lowest reliability are selected from the remaining K_i^t-1(i≤t−1) information bits to serve as the dynamic frozen bit set D_i^tof the ith transmitted code block in the tth transmission. Information about the dynamic frozen bit set D_i^tof the ith transmitted code block is copied to the information bit set A_tof the tth transmitted code block. A one-to-one parity check relationship is established between them.

In an embodiment, FIG. 5 is a block diagram of a data transmission apparatus according to an embodiment of the present application. This embodiment is applied to a data transmission device. As shown in FIG. 5, the data transmission apparatus of this embodiment includes a bit selection module 510, a polar-coding module 520, a combiner 530, and a modulator 540.

The bit selection module 510 is configured to select a first number of bits from a to-be-transmitted information bit sequence to form a to-be-coded bit sequence of a retransmitted data block.

The polar-coding module 520 is configured to polar-code the to-be-coded bit sequence of the retransmitted data block to obtain a coded bit sequence.

The combiner 530 is configured to combine the coded bit sequence with a coded first-transmission data block to obtain the current to-be-transmitted data block.

The modulator 540 is configured to perform digital baseband modulation on the current to-be-transmitted data block and then send the modulated current to-be-transmitted data block to a second communication node.

In an embodiment, the first number is determined by one of a first parameter set or a second parameter set.

The first parameter set contains a physical channel resource parameter of the retransmitted data block and a spectrum efficiency parameter of the retransmitted data block. The second parameter set contains a parallel-polarization-channel-related parameter.