OFDM Cyclic Prefixer

Adds a cyclic prefix and performs pulse shaping on OFDM symbols.

Input

OFDM symbols (in the time domain, i.e. after the IFFT). Optionally, entire frames can be processed. In this case, Length Tag Key must be specified which holds the key of the tag that denotes how many OFDM symbols are in a frame.

Output

A stream of (scalar) complex symbols, which include the cyclic prefix and the pulse shaping.

Note: If complete frames are processed, and Rolloff is greater than zero, the final OFDM symbol is followed by the delay line of the pulse shaping.

The pulse shape is a raised cosine in the time domain.

Parameters

FFT Length

FFT Length (i.e. length of the OFDM symbols)

CP Length

Cyclic prefix length (in samples)

Rolloff

Length of the rolloff flank (in samples). That parameter can sometimes be found described as a percentage of the FFT Length, so that would be Rolloff (%) = (Rolloff (samples)/ FFT_len) * 100.

An explanation of this parameter can be found here

Length Tag Key

For framed processing, the key of the length tag

Example Flowgraph

This flowgraph can be found at [1].

Source Files

C++ files

[2]

Header files

[3]

Public header files

[4]

Block definition

[5]