軟件無(wú)線電作業(yè)(TURBO編碼)

1、4 Modulation and Coding4.3 Channel Coding4.4 Turbo Coding4.5 Early-Termination Mechanism4.3 Channel CodingMost physical channels are subject to turbo coding, with the exception of the Broadcast Channel (BCH), which is based on convolutional coding.Turbo coding is the basis of channel coding as speci

2、fied in the LTE standard. Although turbo coding has been used in many previous standards, it has always been regarded as an optional component alongside other convolutional coding schemes. However, in LTE turbo coding is the driving component of the channel-coding mechanism.4.4 Turbo Codinga turbo c

3、ode is formed by concatenating two conventional encoders in parallel and separating them by an interleaver.(交織器)The output of the turbo encoder is composed of three streams. The bits of the first stream are usually referred to as Systematic bits. The bits of the second and third streams are usually

4、referred to as Parity 1 and Parity 2 bit streams.LTE uses turbo coding with a base rate of 1/3 as the cornerstone of its channel-coding scheme.Each constituent encoder is independently terminated by tail bits. This means that for an input block size of K bits, the output of a turbo encoder consists

5、of three streams of length K+4 bits, due to trellis termination. This makes the coding rate of the turbo coder slightly less than 1/3. Since the tail bits are multiplexed at the end of each stream, the Systematic and Parity 1 and Parity 2 bit streams all are of size K+4.00.511.522.5310-710-610-510-410-310-210-1100Eb/NoBER Turbo 1/3 Interations=1Turbo 1/3 Interations=3Turbo 1/3 Interations=5Elapsed time is 1.578646 seconds.Elapsed time is 430.585486 seconds.Elapsed time is 121.549628 seconds.00.20.40.60.811.21.410-610-510-410-310-210-1100