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I am rote-learning 5G NR concepts for a job interview. In 5G NR, we have something called a Physical layer. Wikipedia defines physical layer as:

The physical layer defines the means of transmitting a stream of 
raw bits over a physical data link connecting network nodes.

So a physical layer is related to a "physical" data link. But 5G is wireless communication. There is no physical data link.

There are control and shared channels in 5G NR that too are prefixed with the word "physical". For example, Physical Uplink Control Channel (PUCCH), Physical Downlink Shared Channel (PDSH), etc.

My question is, why in 5G are we using the word "physical", since it is a "wireless" mode of communication. Please try to clarify in simple terms. Thanks!

winny
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MAJID AHMAD
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2 Answers2

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The Physical Layer is the physical means of RX and TX. In this case it's the radio. The terminology has been standardized and is known as the Open Systems Interconnection model or OSI model, and is used across multiple media types, including WiFi and wired ethernet, but can be applied to pretty much any communications, be it lasers, sonic, Radio, or wired.
The physical layer, is layer 1 in the OSI model.

OSI layers:
7. Application layer
6. Presentation layer
5. Session layer
4. Transport layer
3. Network layer
2. Data link layer
_1. Physical layer

The lower the number the simpler the protocols are. At layer (1) you are in the hardware.

Aaron
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The wireless physical layer includes the electromagnetism and the medium between antennas.

It also includes the transmitter hardware and receiver hardware that convert the “wire-bound” signals to the wireless signals.

As well, all the interconnecting wires and cables and the interface electronics that allow access is also part of the physical layer.

In essence, all of the physics required to allow the communication to happen is the physical layer

RussellH
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