LPWAN communication protocol design with turbo codes

1. A method for decoding a message in an analog signal received at a receiver, the message being encoded in Turbo Codes and modulated for transmission as a plurality of analog values in the analog signal, the message being constructed according to an error detection scheme to allow determining from a Turbo Codes-decoded result whether or not the message has been successfully decoded under the error detection scheme, the method comprising:

(i) demodulating the analog signal to recover the Turbo Codes-encoded message;

(ii) iteratively decoding the Turbo Codes-encoded message for a predetermined number of iterations to obtain a current result, wherein the iterative decoding is performed in conjunction with evaluating a probability that the current result corresponds to a correctly received message, the probability relating to the deviation of the analog values in the analog signal received from their corresponding values at transmission, the probability being in substance:

∑

i

=

1

L

log

⁢

P

⁡

(

Y

i

-

X

i

|

X

i

)

P

⁡

(

Y

i

-

X

i

|

X

i

)

+

P

⁡

(

Y

i

-

X

i

_

|

X

i

_

)

where (a) L is a length in number of bits of the Turbo Codes, (b) X i and Y i are one of analog values at transmission and its corresponding analog value in the analog signal received, respectively, and (c) X i is an analog value representing either a mean or a complement of X i ;

(iii) determining from the current result whether or not the message has been successfully decoded under the error detection scheme; and

(iv) returning to step (ii) for further iterative decoding of the Turbo Codes-encoded message when the message is determined not to have been successfully decoded under the error detection scheme.

2. The method of claim 1 , wherein the predetermined number of iterations is one.

3. The method of claim 1 , wherein the message includes an error detection code, the method further comprising, prior to returning to step (ii), examining the error detection code in the current result; and stopping decoding when the error detection code indicates that an error has not occurred during the transmission.

4. The method of claim 3 , wherein a request for retransmission of the message is sent when the error detection code indicates that an error has occurred during the transmission.

5. The method of claim 3 , wherein the error detection code is generated using the error detection scheme, which is part of an error correction scheme.

6. The method of claim 3 , wherein the error detection code is based on cyclic redundancy check.

7. The method of claim 6 , wherein the cyclic redundancy check is based on a generator polynomial given by:

g ( x )= x 10 +x 9 +x 5 +x 4 +x+ 1.

8. The method of claim 1 , wherein the current result is used in a Turbo Code encoder to regenerate the Turbo Codes, and wherein the probability is computed based on the regenerated Turbo Codes.

9. A decoder for decoding a message in an analog signal received at a receiver, the message being encoded in Turbo Codes and modulated for transmission as a plurality of analog values in the analog signal, the message being constructed according to an error detection scheme to allow determining from a Turbo Codes-decoded result whether or not the message has been successfully decoded under the error detection scheme, the decoder comprising:

a demodulator that demodulates the analog signal to recover the Turbo Codes-encoded message; and

an iterative Turbo Code decoder that (i) provides a current result after a predetermined number of iterations of decoding the Turbo Codes-encoded message; (ii) determines from the current result whether or not the message has been successfully decoded under the error detection scheme; and (iii) returns to further iterative decoding of the Turbo Codes-encoded message when the message is determined not to have been successfully decoded under the error detection scheme;

wherein the iterative Turbo Code decoder operates in conjunction with evaluating a probability that the current result corresponds to a correctly received message, the probability relating to the deviation of the analog values in the analog signal received from their corresponding values at transmission, the probability being in substance:

∑

i

=

1

L

log

⁢

P

⁡

(

Y

i

-

X

i

|

X

i

)

P

⁡

(

Y

i

-

X

i

|

X

i

)

+

P

⁡

(

Y

i

-

X

i

_

|

X

i

_

)

where (a) L is a length in number of bits of the Turbo Codes, (b) X i and Y i are one of analog values at transmission and its corresponding analog value in the analog signal received, respectively, and (c) X i is an analog value representing either a mean or a complement of X i .

10. The decoder of claim 9 , wherein the predetermined number of iterations is one.

11. The decoder of claim 9 , wherein the message includes an error detection code, and wherein the iterative Turbo Code decoder, prior to returning to further iterative decoding, examines the error detection code in the current result, and stops further iterative decoding when the error detection code indicates that an error has not occurred during the transmission.

12. The decoder of claim 11 , wherein a request for retransmission of the message is sent when the error detection code indicates an error has occurred during the transmission.

13. The decoder of claim 11 , wherein the further iterative decoding is carried out in the Turbo Code decoder when the error detection code fails to indicate that an error has occurred during transmission.

14. The decoder of claim 11 , wherein the error detection code is generated using the error detection scheme, which is part of an error correction scheme.

15. The decoder of claim 11 , wherein the error detection code is based on cyclic redundancy check.

16. The decoder of claim 15 , wherein the cyclic redundancy check is based on a generator polynomial given by:

g ( x )= x 10 +x 9 +x 5 +x 4 +x+ 1.

17. The decoder of claim 16 , wherein the current result is used in a Turbo Code encoder to regenerate the Turbo Codes, and wherein the probability is computed based on the regenerated Turbo Codes.