System and method for optimizing forward error correction according to number of simultaneous users

1. A system for optimizing forward error correction (FEC) code for interfering users in a multiple access communication, the system comprising:

a transmitter apparatus, associated with one of the interfering users, the transmitter apparatus including:

a controller configured to receive an FEC code optimization information, switchable between at least a first value and a second value, to select a first optimized FEC code based at least in part on the first value, and select a second optimized FEC code based at least in part on the second value,

a forward error correction (FEC) encoder configured to receive a source bit stream, and encode bits of the source bit stream according to the selected optimized FEC code, and output a series of FEC encoded bits,

wherein:

a parity check matrix of the first optimized FEC code has a first average information bit node degree, and a parity check matrix of the second optimized FEC code has a second average information bit node degree, and

the first optimized FEC code has an FEC rate, and the second optimized FEC code has the FEC rate.

2. The system of claim 1 , wherein:

the controller is further configured to receive, as the FEC code optimization information, an information indicating a target average number of interfering users, the first value indicating a first target average number, and the second value indicating a second target average number, and

the controller is further configured to select between at least the first optimized FEC code and the second optimized FEC code based, at least in part, on a product of the FEC rate and the target average number of users.

3. The system of claim 2 , wherein:

the parity check matrix of the first optimized FEC code has a first constant information bit node degree, the first constant information bit node degree being the first average information bit node degree, and

the parity check matrix of the second optimized FEC code has a second constant information bit node degree, the second constant information bit node degree being the second average information bit node degree.

4. The system of claim 3 , wherein:

the selected FEC code has a constant information bit node degree of 2 when the product of the FEC code rate and the target average number of users is 0.9 or higher.

5. The system of claim 2 , wherein:

the controller is further configured to detect an average number of interfering users and:

upon the product of the detected average number of interfering users and the FEC code rate being within the first range, to automatically select the first optimized FEC code, and

upon the product of the detected average number of interfering users and the FEC code rate being within the second range, to automatically select the second optimized FEC code.

6. The system of claim 2 , wherein,

the controller is further configured to select the first optimized FEC code based, at least in part, on the product of the FEC rate and the target average number of users being within a first range, and to select the second optimized FEC code based, at least in part, on the product of the FEC rate and the target average number of users being within a second range, and

a relation of the product of the target average number of users and the optimized FEC code rate to the first range and to the second range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/6:

Information Bit

Node Degree

of Optimized

Range (R × λ)

Optimized FEC Code

FEC Code

First, less

First Optimized

3

than 0.6

FEC Code

Second, greater

Second Optimized

2

or equal to 0.6

FEC Code.

7. The system of claim 2 , wherein:

the FEC code optimization information is further switchable between at least the first value, the second value and a third value,

the controller is further configured to select a third optimized FEC code, having a third information bit node degree, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

the information bit node degree of the first optimized FEC code, the second optimized FEC code, and the third optimized FEC code, respectively, and a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/8:

Information Bit

Node Degree

of Optimized

Range (R × λ)

Optimized FEC Code

FEC Code

First, less

First Optimized

4

than 0.3

FEC Code

Second, between

Second Optimized

3

0.3 and 0.7

FEC Code

Third, more

Third Optimized

2

than 0.7

FEC Code.

8. The system of claim 2 , wherein:

the FEC code selection information is further switchable between at least the first value, the second value and a third value,

the controller is further configured to select a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/9:

Information Bit

Node Degree

Optimized

of Optimized

Range (R × λ)

FEC Code

FEC Code

First, less

First Optimized

4

than 0.3

FEC Code

Second, between

Second Optimized

3

0.3 and 0.8

FEC Code

Third, more

Third Optimized

2

than 0.8

FEC Code.

9. The system of claim 2 , wherein:

the FEC code selection information is further switchable between at least the first value, the second value and a third value,

the controller is further configured to select a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/15:

Information Bit

Node Degree

Optimized

of Optimized

Range (R × λ)

FEC Code

FEC Code

First, less

First Optimized

4

than 0.5

FEC Code

Second, between

Second Optimized

3

0.5 and 0.9

FEC Code

Third, more

Third Optimized

2

than 0.9

FEC Code.

10. The system of claim 2 , wherein:

the FEC code selection information is further switchable between at least the first value, the second value and a third value,

the controller is further configured to select a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/16:

Information Bit

Node Degree

Range

Optimized

of Optimized

(R × λ)

FEC Code

FEC Code

less than

First Optimized

4

0.55

FEC Code

between

Second Optimized

3

0.55 and

FEC Code

0.9

more than

Third Optimized

2

0.9

FEC Code.

11. A method for optimizing forward error correction (FEC) code for interfering users in a multiple access communication, the method comprising:

receiving an FEC code optimization information, switchable between at least a first value and a second value, and

selecting a first FEC code based at least in part on the FEC code optimization information being at the first value, and

selecting a second FEC code based at least in part on the FEC code optimization information being at the second value; and

receiving a source bit stream, and encoding bits of the source bit stream according to the selected optimized FEC code into a series of FEC encoded bits,

wherein:

a parity check matrix of the first FEC code has a first average information bit node degree, and a parity check matrix of the second FEC code has a second average information bit node degree, and

the first optimized FEC code has an FEC rate, and the second optimized FEC code has the FEC rate.

12. The method of claim 11 , wherein:

receiving the FEC code optimization information includes receiving an information indicating a target average number of interfering users, the first value indicating a first target average number, and the second value indicating a second target average number, and

selecting between at least the first optimized FEC code and the second optimized FEC code is based, at least in part, on a product of the FEC rate and the target average number of users.

13. The method of claim 12 , wherein:

the parity check matrix of the first optimized FEC code has a first constant information bit node degree, the first constant information bit node degree being the first average information bit node degree, and

the parity check matrix of the second optimized FEC code has a second constant information bit node degree, the second constant information bit node degree being the second average information bit node degree.

14. The method of claim 13 , wherein

the selected FEC code has a constant information bit node degree of 2 when the product of the FEC code rate and the target average number of users is 0.9 or higher.

15. The method of claim 12 , wherein the method further includes:

detecting an average number of interfering users, and

upon the product of the detected average number of interfering users and the FEC code rate being within the first range, automatically selecting the first optimized FEC code,

upon the product of the detected average number of interfering users and the FEC code rate being within the second range, automatically selecting the second optimized FEC code.

16. The method of claim 12 , wherein,

selecting the first optimized FEC code is based, at least in part, on the product of the FEC rate and the target average number of users being within a first range,

selecting the second optimized FEC code is based, at least in part, on the product of the FEC rate and the target average number of users being within a second range, and

a relation of the product of the target average number of users and the FEC code rate to the first range and to the second range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/6:

Information Bit

Node Degree

Range

Optimized

of Optimized

(R × λ)

FEC Code

FEC Code

First, less

First Optimized

3

than 0.6

FEC Code

Second, greater

Second Optimized

2

or equal to 0.6

FEC Code.

17. The method of claim 12 , wherein the FEC code optimization information is further switchable between at least the first value, the second value and a third value, and wherein the method further includes:

selecting a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/8:

Information Bit

Node Degree

Range

Optimized

of Optimized

(R × λ)

FEC Code

FEC Code

First, less

First Optimized

4

than 0.3

FEC Code

Second, between

Second Optimized

3

0.3 and 0.7

FEC Code

Third, more

Third Optimized

2

than 0.7

FEC Code.

18. The method of claim 12 , wherein the FEC code optimization information is further switchable between at least the first value, the second value and a third value, and wherein the method further includes:

selecting a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/9:

Information Bit

Node Degree

Range

Optimized

of Optimized

(R × λ)

FEC Code

FEC Code

First, less

First Optimized

4

than 0.3

FEC Code

Second, between

Second Optimized

3

0.3 and 0.8

FEC Code

Third, more

Third Optimized

2

than 0.8

FEC Code.

19. The method of claim 12 , wherein the FEC code optimization information is further switchable between at least the first value, the second value and a third value, and wherein the method further includes:

selecting a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/15:

Information Bit

Node Degree

Range

Optimized

of Optimized

(R × λ)

FEC Code

FEC Code

First, less

First Optimized

4

than 0.5

FEC Code

Second, between

Second Optimized

3

0.5 and 0.9

FEC Code

Third, more

Third Optimized

2

than 0.9

FEC Code.

20. The method of claim 12 , wherein the FEC code optimization information is further switchable between at least the first value, the second value and a third value, and wherein the method further includes:

selecting a third optimized FEC code, based at least in part on a product of the FEC code rate and the target average number of users being within a third range, and

a relation of the product of the target average number of users and the FEC code rate to the first range, the second range, and the third range is according to the table below, where λ is the target average number of interfering users, R is the FEC code rate and R is equal to 1/16:

Information Bit

Node Degree

Range

Optimized

of Optimized

(R × λ)

FEC Code

FEC Code

less than

First Optimized

4

0.55

FEC Code

between

Second

3

0.55 and

Optimized

0.9

FEC Code

more than

Third

2

0.9

Optimized

FEC Code.