Hierarchical modulation

<h2 id="example">Example</h2>

<p>For example, the figure depicts a layering scheme with <a href="/facts/Phase-shift_keying/TFnpYe64">QPSK</a> base layer, and a <a href="/facts/Quadrature_amplitude_modulation/02j52SWG">64QAM</a> enhancement layer.  The first layer is 2 bits (represented by the green circles).  The signal detector only needs to establish which quadrant the signal is in, to recover the value (which is '10', the green circle in the lower right corner).  In better signal conditions, the detector can establish the phase and amplitude more precisely, to recover four more bits of data ('1101').  Thus, the base layer carries '10', and the enhancement layer carries '1101'.
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<h2 id="inter-layer-interference">Inter-layer interference</h2>

<p>For a hierarchically-modulated symbol with QPSK base layer and 16QAM enhancement layer, the base-layer throughput loss is up to about 1.5 bits/symbol with the total receive <a href="/facts/Signal-to-noise_ratio/qohClhyG">signal-to-noise ratio</a> (SNR) at about 23 <a href="/facts/Decibel/0LyxAPXh">dB</a>, about the minimum needed for the comparable non-hierarchical modulation, 64QAM. But unlayered 16QAM with the same SNR would approach full throughput. This means, due to ILI, about 1.5/4 = 37.5% loss of the base-layer achievable throughput. Furthermore, due to ILI and the imperfect demodulation of base-layer symbols, the demodulation error rate of higher-layer symbols increases too.
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Link_adaptation/vegwIxN8">Link adaptation</a></li>
<li>H.264 Scalable Video Coding</li>
<li><a href="/facts/High_Efficiency_Video_Coding/6gp7DC1a">H.265</a> scalability extensions (SHVC)</li>
<li><a href="/facts/AV1/d07UxHgf">AV1 Scalable video coding</a></li>
<li><a href="/facts/MPEG-4_SLS/0hcHB4NH">MPEG-4 SLS</a></li>
<li><a href="/facts/LCEVC/7MShExc7">MPEG-5 Part 2 / Low Complexity Enhancement Video Coding / LC EVC</a></li>
<li><a href="/facts/DTS-HD_Master_Audio/zprgCEGx">DTS-HD MA</a></li>
<li><a href="/facts/Bitrate_peeling/txmjt80K">Ogg Vorbis bitrate peeling</a></li>
<li><a href="/facts/WavPack/MN8nT9Gj">WavPack hybrid mode</a></li>
<li><a href="/facts/JPEG_2000/GAzXdHI2">JPEG 2000 SNR scalability</a></li></ul>

<ul><li>H. Méric, J. Lacan, F. Arnal, G. Lesthievent, M.-L. Boucheret, <a href="https://dx.doi.org/10.1109/TBC.2013.2268694">Combining Adaptive Coding and Modulation With Hierarchical Modulation in Satcom Systems</a>, <i>IEEE Transactions on Broadcasting</i>, Vol. 59, No. 4 (2013), pp 627-637.</li>
<li>Shu Wang, Soonyil Kwon and Yi, B.K., <a href="https://dx.doi.org/10.1109/ISBMSB.2008.4536685">On enhancing hierarchical modulation</a>, <i>IEEE International Symposium on Broadband Multimedia Systems and Broadcasting</i>, March 31 2008-April 2 2008, Las Vegas, NV, (2008), pp. 1-6.</li>
<li>Seamus O Leary, '<a href="https://ieeexplore.ieee.org/document/598365/metrics#metrics">Hierarchical transmission and COFDM systems</a>', Published in: IEEE Transactions on Broadcasting ( Volume: 43, Issue: 2, Jun 1997)Page(s): 166 - 174</li></ul>
<h2 id="external-links">External links</h2>
<ul><li><a href="https://web.archive.org/web/20120325094437/http://www.broadcastpapers.com/whitepapers/Hierarchical.pdf">Hierarchical Modulation Explained</a> at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a> (archived 2012-03-25)</li>
<li><a href="http://www.dvb.org/technology/fact_sheets/WP01_DVB-T%20Hierarchical.pdf">Hierarchical Modulation under DVB</a></li></ul>

Hierarchical modulation open-in-new

Hierarchical modulation