# TC-PAM

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{{Short description|Modulation format used in HDSL2 and G.SHDSL}}
{{More citations needed|date=August 2009}}
{{Modulation techniques}}
'''Trellis-coded pulse-amplitude modulation''' ('''TC-PAM''') is the [modulation](/source/modulation) format that is used in [HDSL2](/source/HDSL2) and [G.SHDSL](/source/G.SHDSL). It is a variant of [trellis coded modulation](/source/trellis_coded_modulation) (TCM) which uses a one-dimensional [pulse-amplitude modulation](/source/pulse-amplitude_modulation) (PAM) symbol space, as opposed to a two-dimensional [quadrature amplitude modulation](/source/quadrature_amplitude_modulation) (QAM) symbol space.<ref>Johannes Huber. [https://web.archive.org/web/20160304035913/http://www.lit.eei.uni-erlangen.de/papers/itg_hub_94.pdf "Multilevel-Codes: Distance Profiles and Channel Capacity"].</ref> Compared to the [2B1Q](/source/2B1Q) scheme used in the older [HDSL](/source/HDSL) and [SDSL](/source/Symmetric_digital_subscriber_line) standards, TC-PAM improves range at a given bit-rate and provides enhanced spectral compatibility with [ADSL](/source/ADSL).

TC-PAM is also known as '''4B1H''', because it uses 16 levels to represents a 4 digit binary, 4 [Binary](/source/Binary_code) 1 [Hexadecimal](/source/Hexadecimal).

==References==
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{{Bit-encoding}}

{{DEFAULTSORT:Tc-Pam}}
Category:Quantized radio modulation modes

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