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I'm new to telecommunication, and from what I understand, an user equipement is either connected to a LAN router or an eNodeB, and a LAN router is connected to a WAN router, and routers send the packets to the correct destination with a routing table. The part that I don't understand is how does all this work with IP/TCP? Let's say UE1 is a stationary device connected to a LAN router and sends a message to UE2, which is a mobile device connected to an eNodeB, how would that work? As far as I understand :

  1. UE1 sends a message to the LAN router
  2. the LAN router sees that the message is not intended for the local network, and sends the message to the corresponding WAN router.
  3. the WAN router sends that message to the corresponding eNodeB
  4. the eNodeB sends the message to UE2

Is this correct? Also, is I understand correctly, an eNodeB is basically a bounch of antennas with some software that can send/receive data from UEs in it's covered area, and a router does pretty much the same thing, so what are the differences between the 2 in terms of functionality (except that the eNodeB covers a wider area)?

Thanks

qwerty_99
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    *I'm new to telecommunication* OK, then I suggest that if you really want to understand all this then you cannot avoid learning about the OSI model: https://en.wikipedia.org/wiki/OSI_model yes, that's boring, I know. But it shows that everything is divided into separate layers. The "bunch of antenna's" (these will need transceivers as well though) is the "physical layer", an ethernet cable is also "physical layer". TCP/IP is part of the protocol layer, it has nothing to do with antennas for example. – Bimpelrekkie Jun 15 '20 at 19:18
  • The OSI model does not reflect reality – user253751 Jun 15 '20 at 19:50
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    @user253751 I think your statement is odd and possibly wrong. But please show an example that supports your claim with an example from reality that doesn't adhere to the OSI model in any way. I'm curcious what such a device would be as I cannot imagine what it could be. – Bimpelrekkie Jun 15 '20 at 20:11
  • @Bimpelrekkie I have read that before, it's just that I'm not sure how exactly sure about what applies to LTE and what applies to wifi – qwerty_99 Jun 15 '20 at 21:01
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    I’m voting to close this question because it is about network topologies or routing rather than Electrical Engineering. If you were building one of these devices, there might be specific implementation questions which would be on topic here, but general questions about how complex computer networks interact are off-topic here. You could ask on Network SE meta if it would be on topic there, but generally speaking broad questions which cannot be specifically answered are not welcome in the SE network, which is rather reserved only for highly specific ones. – Chris Stratton Jun 16 '20 at 00:09
  • *I'm not sure how exactly sure about what applies to LTE and what applies to wifi* All of the OSI model applies to both. The differences between Wifi and LTE are partly in the Physical and Datalink layers as they use slightly different ways (like different frequencies and modulation) to transmit the data through the air. Also the network layer is different as an LTE will be different from you home's local Wifi network. But I agree with Chris, your question is too broad. I suggest you learn more about each network and the similarities and differences will become clear eventually. – Bimpelrekkie Jun 16 '20 at 08:04

1 Answers1

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I'm neither an IP Guru, but think i have a solid understanding of it and I just started working in mobile telecommunications. So I will try to help you here.

The problem in your understanding might be the fact, that the eNodeB is not directly connected to the Internet.

You probably should follow @Bimpelrekkie advice and have a look at the OSI Model to understand how this all works together.

Directly jumping into a mixture of Ethernet and mobile communications is hard. Maybe you should have a look at the EUTRAN=LTE basics, e.g. see https://en.wikipedia.org/wiki/System_Architecture_Evolution.

You simplified the eNodeB pretty much to some antennas and software. That might be true if you simplify it really much. I'll simplify as well, maybe it helps you.

The (simplified) task of the eNodeB is to transmit Data over the Air interface while making sure that each user gets a fair share of the air interface.

What Data is transferred must be differentiated between Userplane Data (Data that is actually "useful") and Control Plane data (data that is used to control the connection).

the eNodeB (simplified) transfers the Userplane data to the Packet Gateway and from the Packet Gateway to the UE. The Packet Gateway is between the eNodeB and the Internet.

Have a look at this figure (you will understand it easier, if you have understood the OSI model): https://www.slideshare.net/sofianonline/ip-concept-in-lte/7 (You can also search for "LTE Stack OSI model" or similar to get some other diagrams).

If you understand Ethernet or "LAN" a bit better, you should maybe compare the eNodeB to a WiFi Access Point. The WiFi Access Point does not directly "talk" IP. It gets IP packets from somewhere and is just (simplified) an Antenna which will put the IP Packet on the Air...

hope that helps

aslmx
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