How do Turbo codes improve the reliability of LTE signals?

1 What are Turbo codes?

Turbo codes are a type of forward error correction (FEC) codes, which are used to add redundancy to the original data before sending it over a noisy channel. The redundancy helps the receiver to correct any errors that may occur during the transmission, without requiring the sender to retransmit the data. Turbo codes are different from other FEC codes in that they use two or more encoders and an interleaver, which rearranges the data bits in a random or pseudo-random way. The interleaver makes the encoded bits more independent and reduces the correlation between the errors, which enhances the performance of the decoder.

2 How do Turbo codes work?

Turbo codes work by applying two or more encoders to the same data, but with different interleaving patterns. The encoders are usually convolutional codes, which use a sliding window of bits to generate output bits based on a predefined rule. The output bits from each encoder are then multiplexed and sent over the channel, along with some of the original data bits as parity bits. The receiver then uses a soft-in soft-out (SISO) decoder, which takes into account the reliability of each received bit, to decode each encoder output separately. The decoder then exchanges information with the other decoder through an iterative process, which improves the accuracy of the decoding. The process stops when a certain criterion is met, such as a maximum number of iterations, a minimum error rate, or a convergence of the decoded outputs.

3 Why are Turbo codes suitable for LTE?

Turbo codes are suitable for LTE because they offer several advantages over LDPC codes or Reed-Solomon (RS) codes. These include the ability to achieve near-Shannon limit performance, which is the theoretical maximum data rate for a given channel capacity and error probability. Turbo codes can also adapt to different channel conditions and data rates by changing the code rate, which is the ratio of data bits to encoded bits. Furthermore, they can support various modulation schemes and multiple-input multiple-output (MIMO) techniques for achieving high spectral efficiency and diversity. Finally, turbo codes can reduce latency and complexity of decoding by using the max-log-MAP algorithm, which simplifies calculation of the reliability of each bit.

4 What benefits do Turbo codes bring to LTE users and operators?

Turbo codes offer several advantages to LTE network users and operators, such as improving the Quality of Service (QoS) and User Experience (UX) by reducing the Bit Error Rate (BER) and Packet Loss Rate (PLR). This enhances the clarity, fidelity, and continuity of communication. Additionally, turbo codes increase coverage and capacity by allowing more data to be transmitted with less power and bandwidth, which reduces interference and congestion of channels while extending device battery life. Furthermore, turbo codes provide interoperability and compatibility with other standards and technologies, such as 3G, 4G, 5G, Wi-Fi, and satellite through a common coding scheme and a flexible interface.

5 Here’s what else to consider

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