Method, system and device for error detection in OFDM wireless communication networks without full forward error correction decoding

Patent metadata

Field	Value
Publication number	US-10003435-B2
Application number	US-201615361160-A
Country	US
Kind code	B2
Filing date	Nov 25, 2016
Priority date	Nov 25, 2015
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A system, method and device for error detection/estimation in OFDM communications systems is proposed. The disclosed mechanism allows an efficient error prediction in a received packet, without having to perform full FEC decoding of the packet that could impair the overall latency of the system due to the time spent in a complete FEC decoding of the packet. In order to do that, it generates a decision variable with the aim to check whether a received packet has errors or not, after performing only partial FEC decoding of the packet, without either resorting to the use of error-detection codes.

First claim

The invention claimed is:

1. A method for detecting errors in an information packet ( 13 ) received by an OFDM receiver ( 14 ) in an Orthogonal Frequency-Division Multiplexing, OFDM, system, where the information packet is encoded using a Forward Error Correction, FEC, technique, said FEC technique involves at the receiver an iterative decoding process, the method characterized by comprising the following steps performed at the receiver ( 14 ):
a) performing a number of iterations, N iter , of the Forward Error Correction decoding technique on the received packet of length N FEC bits, where N iter is lower than the minimum number of iterations required for full FEC decoding at the intended signal to noise and interference ratio, SINR;
b) obtaining a posteriori log-likelihood ratio, LLR, value for each decoded bit after N iter FEC decoding iterations;
c) obtaining the block error probability for the block of decoded bits after N iter iterations, BLEP 0 Niter , and the probability density function of said block error probability, from said a posteriori LLR values;
d) estimating a block error rate that would correspond to the received packet under full FEC decoding, based on post-detection Signal to Interference and Noise Ratios, SINR, of the received bits;
e) obtaining a decision variable value for block error decisions, Z, as a function of the obtained block error probability BLEP 0 Niter and the probability density function of said block error probability; and
f) determining whether the received packet has errors or not, by comparing said decision variable with a first threshold.

2. A method according to claim 1 , where the LLR values for the decoded bits after N iter FEC decoding iterations are defined as:

L
⁢

⁢
L
⁢

⁢

R
n
Niter

≡

ln
⁢

p
⁡

(

x
n

=

+
1

❘
y

)

p
⁡

(

x
n

=

-
1

❘
y

)

,

n
=
0

,
…
⁢

,

N
-
1

,

where LLR n Niter denotes the a-posteriori log-likelihood ratio of the received n-th bit after N iter iterations, y denotes the decoded signal after N iter iterations, x n is the corresponding n-th transmitted bit, and N is defined by the expression N=r·N FEC , where r is the FEC encoding rate.

3. A method according to claim 1 , wherein the block error probability after N iter iterations, BLEP 0 Niter , is obtained by the expression:

B
⁢

⁢
L
⁢

⁢
E
⁢

⁢

P
0
Niter

=

1
-

∏

n
=
0

N
-
1

⁢

⁢

(

1

1
+

e

-



L
⁢

⁢
L
⁢

⁢

R
n
Niter



)

,

where LLR n Niter is the log-likelihood ratio of the received n-th bit after N iter iterations, and N is defined by the expression N=r·N FEC , where r is the FEC encoding rate.

4. A method according to claim 1 , wherein the probability density function of said block error probability after N iter iterations, BLEP Niter , is calculated as a function of the probability density function of the LLR values, LLR n Niter , by using the following transformation:

ln
⁡

(

1
-

B
⁢

Assignees

• Telefonica Sa

Inventors

• Lorca Hernando Javier

Classifications

• H04L69/22

  Parsing or analysis of headers · CPC title

• H03M13/2957

  Turbo codes and decoding · CPC title

• H04L1/201

  Frame classification, e.g. bad, good or erased (frame indication per se H04L1/0082) · CPC title

• H04L1/005

  Iterative decoding, including iteration between signal detection and decoding operation · CPC title

• H03M13/3738

  with judging correct decoding · CPC title