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PHY, L1, Baseband

Started by Sharan123 2 years ago2 replieslatest reply 2 years ago173 views

I am often confused between PHY, L1 and Baseband processing.

Are they same? if not, can anyone help with some explanation please.

Thanks,

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Reply by SuryaParuchuriOctober 25, 2018

From my understanding, this is what I would say,


PHY Layer and L-1 are the identical, 

     -they deal with the transmission format on Actual medium- how 0,1's are organized for Tx on PHY medium including the wireless, wired, fiber, etc. 

     -this includes any protocol specifications that include header information, etc, channel sensing or handling collision detection or avoidance etc. Essentially it tells how 0 and 1's from above layer (this includes 0, and 1's from L-2/MAC's header and data) are packed into say frames on say 802.15.4 protocol. 

      -In addition, it also defines (NOTE: ONLY DEFINES the SPECS, THIS IS NOT THE WORKER) the levels at which and what physical signals are to be transmitted on PHY medium and what modulations/waveforms are allowed and such mappings.


BaseBand Processing: (THIS IS THE WORKER, that I was referring to in the above note)

      -This begins with sensing the physical signal on transducer, processing it and ends with returning the symbols based on Rxd waveform to some process in say processor or viceversa if communication is otherwise.

      -BaseBand Processing doesn't delineate weather a set of 0 and 1's is part of control plane or data plane (sorry for the Wireless jargon), where as PHY clearly delineates between control and data planes by reading through header information etc, re-arranging any fragmented packets before delivering to the above layer, error checking etc.

      -BaseBand Processing mainly deals with the -- You have a signal that is conditioned through Front-End (RF/Optical/...,) and then digitized and then extract the bits from modulated symbol's waveform. Period.



Hope this helps. Please correct me if I am wrong.

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Reply by Y(J)SOctober 26, 2018

The term "PHY" is frequently used in Ethernet to distinguish the physical layer of Ethernet from the MAC layer (since Ethernet straddles both layer 1 and layer 2 of the OSI model).

Layer 1 is the general term in the OSI 7-layer model for any physical layer communications (wireline, optic, radio, etc.).

Baseband processing is a term used most often in cellular systems for the DSP processing to generate or demodulate the radio signal. It is less frequently used for the same functions other radio systems.

Y(J)S