Error floor
Encyclopedia
The error floor is a phenomenon encountered in modern iterated sparse graph
-based error correcting codes like LDPC codes and turbo codes. When the bit error ratio
(BER) curve is plotted for conventional codes like Reed Solomon codes under algebraic decoding or for convolutional codes under Viterbi decoding
, the curve steadily decreases as the SNR
condition becomes better. For LDPC codes and turbo codes there is a point after which the curve does not fall as quickly as before, in other words, there is a region in which performance flattens. This region is called the error floor region. The region just before the sudden drop in performance is called the waterfall region.
Error floors are usually attributed to low-weight codewords (in the case of Turbo codes) and trapping sets or near-codewords (in the case of LDPC codes).
Sparse graph code
A Sparse graph code is a code which is represented by a sparse graph.Any linear code can be represented as a graph, where there are two sets of nodes - a set representing the transmitted bits and another set representing the constraints that the transmitted bits have to satisfy...
-based error correcting codes like LDPC codes and turbo codes. When the bit error ratio
Bit error ratio
In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors....
(BER) curve is plotted for conventional codes like Reed Solomon codes under algebraic decoding or for convolutional codes under Viterbi decoding
Viterbi decoder
A Viterbi decoder uses the Viterbi algorithm for decoding a bitstream that has beenencoded using forward error correction based on a convolutional code....
, the curve steadily decreases as the SNR
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
condition becomes better. For LDPC codes and turbo codes there is a point after which the curve does not fall as quickly as before, in other words, there is a region in which performance flattens. This region is called the error floor region. The region just before the sudden drop in performance is called the waterfall region.
Error floors are usually attributed to low-weight codewords (in the case of Turbo codes) and trapping sets or near-codewords (in the case of LDPC codes).