PROGRESSIVE PARALLEL INTERFERENCE CANCELLER AND METHOD AND RECEIVER THEREOF

• US 20110013735A1
• Filed: 09/07/2009
• Published: 01/20/2011
• Est. Priority Date: 07/16/2009
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Lai, Jiun-Yo, Huang, Chia-Chi, Huang, Chao-Wang, Ting, Pang-An
• Granted Patent: US 8,331,477 B2
• Time in Patent Office: Days
• US Class Current: 375/349
• CPC Class Codes: H04J 11/004 using regenerative subtractive interference cancellation
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A progressive parallel interference canceller (PPIC) and a method and a receiver thereof are illustrated. The PPIC reconstructs each subchannel interference reconstruction signal through several iterations and subtracts the corresponding subchannel interference reconstruction signal from each subchannel frequency-domain reception signal to obtain a subchannel frequency-domain signal. Thereby, according to the present disclosure, inter-channel interference can be cancelled without re-performing channel coding or estimating the signal to noise ratio (SNR) or frequency offset.

Claims

1. A progressive parallel interference canceller (PPIC), adaptable to a receiver in a multiple input multiple output (MIMO) communication system based on an orthogonal frequency-division multiplexing (OFDM) modulation technique, wherein the receiver performs a plurality of iterations, the PPIC comprising:

a plurality of subchannel interference reconstruction units, wherein the k^th subchannel interference reconstruction unit corresponding to a r^th receiving antenna generates a k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna during the i^th iteration according to (2×

i−

2) subchannel frequency-domain estimation signals Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾, wherein i is an integer greater than 1, the subchannel frequency-domain estimation signal Ŝ

_t,q^(x) represents a q^th subchannel frequency-domain estimation signal corresponding to a t^th transmitting antenna generated during the x^th iteration, and ((•

))_N represents a calculation of dividing by N to obtain a remainder, N is a number of subchannels in the MIMO communication system, k is an integer between 0 and (N−

1), x is an integer between 1 and (i−

1), and q=k−

i+x or q=k+i−

x; and

a plurality of subchannel interference cancellation units, wherein the k^th subchannel interference cancellation unit corresponding to the r^th receiving antenna is coupled to the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna, and the k^th subchannel interference cancellation unit obtains a k^th subchannel frequency-domain signal Y′

_r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to a k^th subchannel frequency-domain reception signal Y_r,k and the k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna during the i^th iteration.

2. The PPIC according to claim 1, wherein during the 1^st iteration, the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna presets a k^th subchannel interference reconstruction signal S_ICI,r,k⁽¹⁾ corresponding to the r^th receiving antenna to 0, and the k^th subchannel interference cancellation unit corresponding to the r^th receiving antenna obtains a k^th subchannel frequency-domain signal Y′

_r,k⁽¹⁾ corresponding to the r^th r,k receiving antenna according to the k^th subchannel frequency-domain reception signal Y_r,k corresponding to the r^th receiving antenna.

3. The PPIC according to claim 1, wherein a k^th subchannel frequency-domain signal Y′

_r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna is equivalent to a k^th subchannel frequency-domain reception signal Y_r,k corresponding to the r^th receiving antenna minus the k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾.

4. The PPIC according to claim 1, wherein the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna has a memory, and the k^th subchannel interference reconstruction unit of the r^th receiving antenna stores the subchannel frequency-domain estimation signals Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾ into the memory, transmits the subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+2))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+3))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

2)</sup>, Ŝ

_t,((k))N<sup>(i−

1)</sup> to the (k+1)^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna, and transmits the subchannel frequency-domain estimation signals Ŝ

<sub>t,((k+i−

2))N</sub>⁽¹⁾, Ŝ

<sub>t,((k+i−

3))N</sub>⁽²⁾, . . . , Ŝ

_t,((k+1))N<sup>(i−

2)</sup>, Ŝ

_t,((k))N<sup>(i−

1)</sup> to the (k−

1)^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna.

5. The PPIC according to claim 1 further comprising a channel estimator, wherein the channel estimator estimates a plurality of channel impulse responses of a wireless channel and calculates a plurality of coefficients according to the channel impulse responses, wherein the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna generates a k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to the (2×

i−

2) subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾ and the coefficients during the i^th iteration.

6. The PPIC according to claim 2 further comprising:

a MIMO detector, coupled to the subchannel interference reconstruction units and the subchannel interference cancellation units, for determining a plurality of bits b₀, b₁, . . . , and b<sub>MT−

1</sub> corresponding to k^th subchannels of the transmitting antennas according to the k^th subchannel frequency-domain signals Y′

_1,k⁽ⁱ⁾, Y′

_2,k⁽ⁱ⁾, . . . , and Y′

_R,k⁽ⁱ⁾ of the receiving antennas when the PPIC performs the i^th iteration, wherein M is a bit modulation order, R is a number of the receiving antennas, T is a number of the transmitting antennas, and the bits b<sub>M(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> corresponding to the k^th subchannel of the t^th transmitting antenna are used for determining the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾.

7. The PPIC according to claim 6, wherein the MIMO detector is a MIMO detector using a message passing algorithm (MPA).

8. The PPIC according to claim 6, wherein the MIMO detector performs a plurality of sub iterations during the i^th iteration, and during each of the sub iterations, the MIMO detector generates a probability message for the bit b_n according to the subchannel frequency-domain signal Y′

_r,k⁽ⁱ⁾ and generates a probability message for the subchannel frequency-domain signal Y′

_p,k⁽ⁱ⁾ according to the bit b_a, and during the last sub iteration, the MIMO detector generates probabilities of the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> according to the probability messages, wherein p is an integer between 1 and T, and a and n are integers between 0 and (MT−

1).

9. The PPIC according to claim 8, wherein if the i^th iteration is the last iteration, the MIMO detector makes a hard decision according to the probabilities of the bits b₀, b₁, . . . , and b_MT−

1 to determine the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> and if the i^th iteration is not the last iteration, the MIMO detector makes a soft decision according to the probabilities of the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> to determine the bits b₀, b₁, . . . , and b<sub>MT−

1</sub>.

10. The PPIC according to claim 6 further comprising a channel decoder coupled to the MIMO detector, wherein the channel decoder determines the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾ according to the bits b<sub>m(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> of the k^th subchannel of the t^th transmitting antenna.

11. The PPIC according to claim 6, wherein the MIMO detector determines the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾ according to the bits b<sub>M(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> of the k^th subchannel of the t^th transmitting antenna.

12. A receiver, adaptable to a MIMO communication system based on an OFDM modulation technique, wherein the receiver performs a plurality of iterations and comprises:

a plurality of receiving antennas;

a plurality of OFDM demodulators, wherein each of the OFDM demodulators is coupled to one of the receiving antennas;

a PPIC, coupled to the OFDM demodulators, the PPIC comprising;

a plurality of subchannel interference reconstruction units, wherein the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna generates a k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to (2×

i−

2) subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾ during the i^th iteration, wherein i is an integer greater than 1, the subchannel frequency-domain estimation signal represents the q^th subchannel frequency-domain estimation signal corresponding to a t^th transmitting antenna generated during the x^th iteration, ((•

))_N represents a calculation of dividing by N to obtain a remainder, N is a number of subchannels in the MIMO communication system, k is an integer between 0 and (N−

1), x is an integer between 1 and (i−

1), and q=k−

i+x or q=k+i−

x; and

a plurality of subchannel interference cancellation units, wherein the k^th subchannel interference cancellation unit corresponding to the r^th receiving antenna is coupled to the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna, and the k^th subchannel interference cancellation unit obtains a k^th subchannel frequency-domain signal Y_r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to a k^th subchannel frequency-domain reception signal Y_r,k and the k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna during the i^th iteration; and

a MIMO detector, coupled to the subchannel interference reconstruction units and the subchannel interference cancellation units, for determining a plurality of bits b₀, b₁, . . . , and b<sub>MT−

1</sub> corresponding to k^th subchannels of the transmitting antennas according to the k^th subchannel frequency-domain signals Y′

_1,k⁽ⁱ⁾, Y′

_2,k⁽ⁱ⁾, . . . , and Y′

_R,k⁽ⁱ⁾ of the receiving antennas when the PPIC performs the i^th iteration, wherein M is a bit modulation order, R is a number of the receiving antennas, T is a number of the transmitting antennas, and the bits b<sub>M(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> corresponding to the k^th subchannel of the t^th transmitting antenna are used for determining the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾.

13. The receiver according to claim 12, wherein when the PPIC performs the 1^st iteration, the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna presets a k^th subchannel interference reconstruction signal S_ICI,r,k⁽¹⁾ corresponding to the r^th receiving antenna to 0, and the k^th subchannel interference cancellation unit corresponding to the r^th receiving antenna obtains a k^th subchannel frequency-domain signal Y′

_r,k⁽¹⁾ corresponding to the r^th receiving antenna according to the k^th subchannel frequency-domain reception signal Y_r,k corresponding to the r^th receiving antenna.

14. The receiver according to claim 12, wherein a k^th subchannel frequency-domain signal Y′

_r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna is equivalent to a k^th subchannel frequency-domain reception signal Y_r,k corresponding to the r^th receiving antenna minus the k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾.

15. The receiver according to claim 12, wherein the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna has a memory, and the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna stores the subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k))N<sup>(i−

1)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, . . . , Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾ into the memory, transmits the subchannel frequency-domain estimation signals Ŝ

<sub>t((k−

i+2))N</sub>⁽¹⁾, Ŝ

<sub>t((k−

i+3))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

2)</sup>, Ŝ

((k))_N<sup>(i−

1)</sup> to the (k+1)^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna, and transmits the subchannel frequency-domain estimation signals Ŝ

<sub>t((k+i−

2))N</sub>⁽¹⁾, Ŝ

<sub>t((k+i−

3))N</sub>⁽²⁾, . . . , Ŝ

_t,((k+1))N<sup>(i−

2)</sup>, Ŝ

((k))_N<sup>(i−

1)</sup> to the (k−

1)^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna.

16. The receiver according to claim 12 further comprising a channel estimator, wherein the channel estimator estimates a plurality of channel impulse responses of a wireless channel and calculates a plurality of coefficients according to the channel impulse responses, wherein the k^th subchannel interference reconstruction unit corresponding to the r^th receiving antenna generates a k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to (2×

i−

2) subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾, and the coefficients during the i^th iteration.

17. The receiver according to claim 12, wherein the MIMO detector is a MIMO detector using a MPA.

18. The receiver according to claim 12, wherein the MIMO detector performs a plurality of sub iterations during the i^th iteration, and during each of the sub iterations, the MIMO detector generates a probability message for the bit b_n according to the subchannel frequency-domain signal Y′

_r,k⁽ⁱ⁾ and then generates a probability message for the subchannel frequency-domain signal Y′

_p,k⁽ⁱ⁾ according to the bit b_a, and during the last sub iteration, the MIMO detector generates probabilities of the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> according to the probability messages, wherein p is an integer between 1 and T, and a and n are integers between 0 and (MT−

1).

19. The receiver according to claim 18, wherein if the i^th iteration is the last iteration, the MIMO detector makes a hard decision according to the probabilities of the bits b₀, b₁, . . . , and b_MT−

1 to determine the bits b₀, b₁, . . . , and b<sub>MT−

1</sub>, and if the i^th iteration is not the last iteration, the MIMO detector makes a soft decision according to the probabilities of the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> to determine the bits b₀, b₁, . . . , and b<sub>MT−

1</sub>.

20. The receiver according to claim 12 further comprising a channel decoder coupled to the MIMO detector, wherein the channel decoder determines the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾ according to the bits b<sub>M(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> of the k^th subchannel of the t^th transmitting antenna.

21. The receiver according to claim 12, wherein the MIMO detector determines the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾ according to the bits b<sub>M(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> of the k^th subchannel of the t^th transmitting antenna.

22. A progressive parallel interference cancellation method, adaptable to a receiver in a MIMO communication system based on an OFDM modulation technique, wherein the receiver performs a plurality of iterations, the progressive parallel interference cancellation method comprising:

generating a k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to (2×

i−

1) subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾, during the i^th iteration, wherein i is an integer greater than 1, the subchannel frequency-domain estimation signal Ŝ

_1,q^(x) represents the q^th subchannel frequency-domain estimation signal corresponding to a t^th transmitting antenna generated during the x^th iteration, ((•

))_N represents a calculation of dividing by N to obtain a remainder, N is a number of subchannels in the MIMO communication system, k is an integer between 0 and (N−

1), x is an integer between 1 and (i−

1), q=k−

i+x or q=k+i−

x; and

obtaining a k^th sub channel frequency-domain signal Y′

_r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna according to a k^th subchannel frequency-domain reception signal Y_r,k and the k^th subchannel interference reconstruction signal S_ICI,r,k^{(i) corresponding to the rth} receiving antenna during the i^th iteration.

23. The progressive parallel interference cancellation method according to claim 22 further comprising:

during the first iteration, presetting a k^th subchannel interference reconstruction signal S_ICI,r,k⁽¹⁾ corresponding to the r^th receiving antenna to 0, and obtaining a k^th subchannel frequency-domain signal Y′

_r,k⁽¹⁾ corresponding to the r^th receiving antenna according to the k^th subchannel frequency-domain reception signal Y_r,k corresponding to the r^th receiving antenna.

24. The progressive parallel interference cancellation method according to claim 22, wherein a k^th subchannel frequency-domain signal Y′

_r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna is equivalent to a k^th subchannel frequency-domain reception signal Y_r,k corresponding to the r^th receiving antenna minus the k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾.

25. The progressive parallel interference cancellation method according to claim 22 further comprising:

estimating a plurality of channel impulse responses of a wireless channel, and calculating a plurality of coefficient according to the channel impulse responses,

wherein a k^th subchannel interference reconstruction signal S_ICI,r,k⁽ⁱ⁾ corresponding to the r^th receiving antenna is generated according to (2×

i−

2) subchannel frequency-domain estimation signals Ŝ

<sub>t,((k−

i+1))N</sub>⁽¹⁾, Ŝ

<sub>t,((k−

i+2))N</sub>⁽²⁾, . . . , Ŝ

<sub>t,((k−

2))N</sub><sup>(i−

2)</sup>, Ŝ

<sub>t,((k−

1))N</sub><sup>(i−

1)</sup>, Ŝ

_t,((k+2))N<sup>(i−

2)</sup>, Ŝ

_t,((k+1))N<sup>(i−

1)</sup>, . . . , Ŝ

<sub>t,((k+i−

2))N</sub>⁽²⁾, Ŝ

<sub>t,((k+i−

1))N</sub>⁽¹⁾ and the coefficients during the i^th iteration.

26. The progressive parallel interference cancellation method according to claim 22 further comprising:

determining a plurality of bits b₀, b₁, . . . , and b<sub>MT−

1</sub> corresponding to the k^th subchannels of the transmitting antennas according to the k^th subchannel frequency-domain signals Y′

_1,k⁽ⁱ⁾, Y′

_2,k⁽ⁱ⁾, . . . , and Y′

_R,k⁽ⁱ⁾ of the receiving antennas during the i^th iteration, wherein M is a bit modulation order, R is a number of the receiving antennas, T is a number of the transmitting antennas, and the bits b<sub>M(t−

1)</sub>, b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> corresponding to the k^th subchannel of the t^th transmitting antenna are used for determining the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾.

27. The progressive parallel interference cancellation method according to claim 26, wherein a plurality of sub iterations is performed during the i^th iteration, and during each of the sub iteration, a probability message is generated for the bit b_n according to the subchannel frequency-domain signal Y′

r,k⁽ⁱ⁾, and a probability message is then generated according to the bit b_a for the subchannel frequency-domain signal Y′

_p,k⁽ⁱ⁾, and during the last sub iteration, probabilities of the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> are generated according to the probability messages, wherein p is an integer between 1 and T, and a and n are integers between 0 and (MT−

1).

28. The progressive parallel interference cancellation method according to claim 27, wherein if the i^th iteration is the last iteration, a hard decision is made according to the probabilities of the bits b₀, b₁, . . . , and b_MT−

1 to determine the bits b₀, b₁, . . . , and b<sub>MT−

1</sub>, and if the i^th iteration is not the last sub iteration, a soft decision is made according to the bits b₀, b₁, . . . , and b<sub>MT−

1</sub> to determine the bits b₀, b₁, . . . , and b<sub>MT−

1</sub>.

29. The progressive parallel interference cancellation method according to claim 26 further comprising:

determining the subchannel frequency-domain estimation signal Ŝ

_t,k⁽ⁱ⁾ according to the bits b<sub>M(t−

1</sub>), b<sub>M(t−

1)+1</sub>, . . . , and b<sub>Mt−

1</sub> of the k^th subchannel of the t^th transmitting antenna.