From cc7d726ac3fb3683999f01f2881b6931e645c4d6 Mon Sep 17 00:00:00 2001 From: "Matthias P. Braendli" Date: Sat, 18 Nov 2017 03:20:36 +0100 Subject: Correct TII power --- src/TII.cpp | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) (limited to 'src') diff --git a/src/TII.cpp b/src/TII.cpp index 4ed1a91..4710ed4 100644 --- a/src/TII.cpp +++ b/src/TII.cpp @@ -197,16 +197,30 @@ int TII::process(Buffer* dataIn, Buffer* dataOut) complexf* in = reinterpret_cast(dataIn->getData()); complexf* out = reinterpret_cast(dataOut->getData()); + if ((m_enabled_carriers.size() % 2) != 0) { + throw std::logic_error("odd number of enabled carriers"); + } + + /* Normalise the TII carrier power according to ETSI TR 101 496-3 + * Clause 5.4.2.2 Paragraph 7: + * + * > The ratio of carriers in a TII symbol to a normal DAB symbol + * > is 1:48 for all Modes, so that the signal power in a TII symbol is + * > 16 dB below the signal power of the other symbols. + * + * We need to normalise to the square root of 48 because we touch I and + * Q separately. + */ + const float normalise_factor = 0.14433756729740644112f; // = 1/sqrt(48) + for (size_t i = 0; i < m_enabled_carriers.size(); i+=2) { - //BAD implementation: - // setting exactly the same phase of the signal for lower adjacent - // frequency + // See header file for an explanation of the old variant if (m_enabled_carriers[i]) { - out[i] = (m_conf.old_variant ? in[i+1] : in[i])/((float)48.0); + out[i] = normalise_factor * (m_conf.old_variant ? in[i+1] : in[i]); } if (m_enabled_carriers[i+1]) { - out[i+1] = in[i+1]/((float)48.0); + out[i+1] = normalise_factor * in[i+1]; } } } -- cgit v1.2.3