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Also known as: Parallel Concatenated Convolutional Codes
Concatenated convolutional codes with interleaving and iterative decoding that achieve near-Shannon-limit error performance.
DESCRIPTION
Turbo codes combine two or more convolutional encoders via an interleaver and decode them iteratively using soft information. Introduced in the 1990s, they revolutionized coding by approaching Shannon limits at practical complexity. Widely used in 3G/4G cellular standards, they deliver strong performance at moderate block lengths. Decoders rely on MAP or log-MAP algorithms exchanging extrinsic information. Interleaver design and termination affect performance and latency. While LDPC and Polar codes dominate newer standards, Turbo codes remain a milestone and are still deployed.
ALTERNATIVE DEFINITIONS
Wikipedia
Turbo codes are a class of high-performance error correction codes developed in 1993 that are built from the parallel concatenation of two or more convolutional codes.
Stresses parallel concatenation and high performance near capacity.
Wolfram MathWorld
A turbo code is a concatenated code employing iterative decoding that achieves performance near the Shannon limit.
Highlights iterative decoding and near-limit performance.
RELATED TERMS
Convolutional Code Interleaver Iterative Decoding MAP Decoder Viterbi Algorithm Error-Correcting Code LTE CDMA2000 Bit Error Rate Rate Matching
COMPETING TERMS
KNOWLEDGE AREAS
Infrastructure IoT & Edge Data Real-time & Streaming Data Mathematics
TARGET AUDIENCE
Hardware Engineer Software Developer Data Engineer
EXTERNAL SOURCES
- Wikipedia - Turbo code
- 3GPP - LTE channel coding (Turbo)
- ETSI - LTE multiplexing and channel coding
- NASA JPL - Modem design with Turbo decoding
TOP QUESTIONS
How do Turbo Codes approach Shannon limits?
By iteratively exchanging soft information between concatenated decoders, they refine estimates and reduce errors toward capacity performance.
Category: Concept
What is the role of interleavers in Turbo Codes?
Interleavers decorrelate error patterns and spread information, enabling iterative decoding gains.
Category: Concept
Where are Turbo Codes used in practice?
They are used in 3G/4G cellular systems and various communication standards requiring strong error correction at moderate block lengths.
Category: Application
How do Turbo Codes compare to LDPC Codes?
Turbo codes excel at moderate lengths; LDPC often provide higher throughput and better scaling in modern systems.
Category: Comparison
What algorithms decode Turbo Codes?
MAP, log-MAP, and max-log-MAP algorithms compute soft decisions and extrinsic information iteratively.
Category: Overview
What are common pitfalls with Turbo decoding?
Poor interleaver design, insufficient iterations, and numerical issues can cause error floors and degraded performance.
Category: Mistakes
Are Turbo Codes outdated?
They remain relevant in deployed systems, though newer standards often prefer LDPC or Polar codes for performance and implementation reasons.
Category: Opinion
How can I tune Turbo decoders?
Adjust iteration count, use normalization or scaling for log-likelihood ratios, and select robust interleavers.
Category: HowTo
What is a striking analogy for Turbo decoding?
It’s like two experts iteratively cross-checking their opinions until they converge on a shared conclusion.
Category: Example