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- Sistema de modulació que permet la transmissió de dos fluxos de dades diferents (alta prioritat i baixa prioritat) en un únic flux d'un canal (principalment usat en l'estàndard DVB-T). Les dades d'alta prioritat es destinen als receptors mòbils i/o portàtils, i a les zones allunyades del transmissor on el SNR és menor. Les de baixa prioritat estan destinades a les zones properes al transmissor per a receptors fixes. (ca)
- Hierarchical modulation, also called layered modulation, is one of the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are synchronously overplayed before transmission. Hierarchical modulation is particularly used to mitigate the cliff effect in digital television broadcast, particularly mobile TV, by providing a (lower quality) fallback signal in case of weak signals, allowing graceful degradation instead of complete signal loss. It has been widely proven and included in various standards, such as DVB-T, MediaFLO, UMB (Ultra Mobile Broadband, a new 3.5th generation mobile network standard developed by 3GPP2), and is under study for DVB-H. Hierarchical modulation is also taken as one of the practical implementations of superposition precoding, which can help achieve the maximum sum rate of broadcast channels. When hierarchical-modulated signals are transmitted, users with good reception and advanced receivers can demodulate multiple layers. For a user with a conventional receiver or poor reception, it may only demodulate the data stream embedded in the base layer. With hierarchical modulation, a network operator can target users of different types with different services or QoS. However, traditional hierarchical modulation suffers from serious inter-layer interference (ILI) with impact on the achievable symbol rate. (en)
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- 4966 (xsd:nonNegativeInteger)
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- Hierarchical Modulation Explained (en)
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- Sistema de modulació que permet la transmissió de dos fluxos de dades diferents (alta prioritat i baixa prioritat) en un únic flux d'un canal (principalment usat en l'estàndard DVB-T). Les dades d'alta prioritat es destinen als receptors mòbils i/o portàtils, i a les zones allunyades del transmissor on el SNR és menor. Les de baixa prioritat estan destinades a les zones properes al transmissor per a receptors fixes. (ca)
- Hierarchical modulation, also called layered modulation, is one of the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are synchronously overplayed before transmission. However, traditional hierarchical modulation suffers from serious inter-layer interference (ILI) with impact on the achievable symbol rate. (en)
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- Modulació jeràrquica (ca)
- Hierarchical modulation (en)
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