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Source coding in WiFi or LTE

Started by Sharan123 3 years ago7 replieslatest reply 3 years ago513 views

Hi,

I am interested to know what source coding method is used in case of #WiFi or #LTE. I assume Turbo coding or LDPC are used for channel coding.

Thanks,

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Reply by SlartibartfastDecember 31, 2016

There often isn't any, since the "source" of the data is usually not known to the modem, or even the network.  That makes it hard to apply source coding since the nature of the data is unknown.  In order to transport data (which in many cases as far as the system knows may already be compressed) any compression used must be lossless, which may result in a system that offers little gain for much effort.

Voice or video traffic will already be coded by whatever standard is in use by the end devices, so, again, the modem generally doesn't do any source coding since it can't make assumptions about the source.

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Reply by Sharan123December 31, 2016

Makes perfect sense. I forget that entities like Basestations are just conduits for ends users data.

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Reply by rrlagicDecember 31, 2016

In LTE several coding schemes are used forddifferent channels. Particularly, Turbo coding in shared channels and convolutional in control ones and that is not full list.

In OFDM variants of modern WiFi convolutional is used in coding of the signal field.

However, as both specs are open, I would suggest to download a copy and have them for the further details.

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Reply by Sharan123December 31, 2016

Sorry, rrlagic. I am asking about source coding and not channel coding. In digital communication, Huffman or RLC are examples of source coding ...

I have been working on the PHY part of LTE but haven't come across any source coding. Hence my question ...

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Reply by mukulJanuary 1, 2017

Hello rrlagic,

These are channel coding scheme and not source coding.

In source coding you compress data for bandwidth saving, whereas in channel coding you add redundant data to combat wireless channel impairments.

Better brush up basics before putting incorrect replies.

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Reply by fpgaplayerJanuary 16, 2017

speech code : e.g. : AMR for 2G, 3G , 4G; AMR-WB for 4G(VoLTE)

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Reply by Sharan123January 16, 2017

Thanks, fpgaplayer ...