
Show HN: End-to-end LTE example with Docker and emulated radio - pgorczak
https://github.com/pgorczak/srslte-docker-emulated
======
pgorczak
If you wonder about real world use cases for open source LTE stacks like
srsLTE: They’re great for deploying small ad-hoc cells e.g. in vehicular and
rescue scenarios like in our work from earlier this year:
[https://arxiv.org/abs/1802.09262](https://arxiv.org/abs/1802.09262)

~~~
danellis
In an ad hoc situation like a rescue, what would the backhaul be?

~~~
fyfy18
I used to volunteer for a first aid organisation and often we would be
providing support for large events like county shows or sports events.

The radios we used were simple VHF radios on licensed frequencies. There was
no encryption which meant anyone could listen in, so obviously we weren't
allowed to discuss personal details over the radio. Depending on the actual
event we may be covering a large area or uneven terrain, so the radios may not
always work.

For backhaul we'd either use our phone if we needed to call the emergency
services or for larger events we'd have them onsite so they would forward the
message on - for example to warn a hospital of an incoming patient (often it
was in remote areas where the nearest hospital had limited A&E facilities) or
to call an air ambulance.

------
bronco21016
Perhaps I’m missing something but what is the benefit of LTE over 802.11ac? I
know that traditionally LTE is only on licensed bands and 802.11ac mostly on
unlicensed. However, it seems 802.11ac gear is significantly cheaper. Both
technologies can be run across whatever spectrum you’d like.

What characteristics does LTE have that makes it better than 802.11ac for some
of the applications mentioned?

~~~
person_of_color
Distance?

~~~
bronco21016
I thought distance was more tied to effective radiated power, installation,
and frequency selections. Off the shelf 2.4 GHz 802.11ac gear can easily do
30+ mi.

~~~
steve19
With ultra high gain antennas right? So 30+ miles is only good for point to
point applications.

------
md224
Side question: there's no way to get low-level access to the WiFi adapter in a
MacBook Pro, right? It would be nice if I could do SDR stuff with the radio
antenna that came with my computer... though I'm guessing it's not the right
type of antenna anyway.

~~~
freedomben
Yes, the wifi antennas are very specifically sized for the 802.11 frequency
ranges. They also often have band pass filters built in to prevent
transmissions outside of those bands, as required by FCC regulations and such.
That said, if you are really interested in that kind of thing, and you are
willing to switch to Linux, the wireless card drivers are very hackable.

Source: I forked the driver for my wireless card many years ago and still
maintain it, tho these days it's mostly the upstream kernel driver plus a few
hacks to get the most out of the hardware:
[https://github.com/FreedomBen/rtl8188ce-linux-
driver](https://github.com/FreedomBen/rtl8188ce-linux-driver)

~~~
tuxxy
Damn, this is really cool. Great work!

Small question: how much does this affect power on the laptops you've used
this on?

~~~
freedomben
Thank you! I'm sorry I'm not totally sure what you are asking. Are you asking
how much does it drain the laptop battery? To be honest I've never really
tested that, but I'm curious now :-) If you are asking how much the driver
affects the transmit power of the wireless card, it takes it from 20 dB up to
33 dB, and each 3 dB is a doubling of power, so it cranks it up by a
significant amount.

~~~
tuxxy
Yes, I was curious about how much this affects battery drain. It seems like it
would be a considerable amount.

------
peter_retief
I have started development for low power IOT devices and am very keen to use
LTE bands from 450 MHz to 2.7 GHz LTE Cat-M1/NB1/NB2 protocol layers L1-L3 to
leverage the low power modems that are being developed on chip. I want to know
if there is a way to make a local transmitter, there is no LTE-M cellular
spectrum where I work from

------
pedrocr
So a fully open-source phone is now feasible given friendly hardware? I
thought replacing the baseband was much farther away.

~~~
pabs3
The Osmocom project created a GSM baseband codebase already (but it isn't
useful for end-users):

[https://osmocom.org/projects/baseband/](https://osmocom.org/projects/baseband/)

There are LTE modems that run Linux, theoretically the code that runs on them
could be rewritten from scratch:

[https://osmocom.org/projects/quectel-
modems/](https://osmocom.org/projects/quectel-modems/)

In addition there have been many baseband exploits over the years, those could
be used to gain access to basebands and reverse engineer everything.

------
fest
Does anyone have experience with private LTE networks and iOS devices? Do they
generally work in networks like this?

------
nimbius
these are interesting PoC's but the biggest hurdle for me is the price of the
hardware. ~700-1000 USD for a radio?

are there better alternatives anyone knows of?

~~~
pgorczak
The [https://github.com/srsLTE/srsLTE/](https://github.com/srsLTE/srsLTE/)
readme says they’ve tested LimeSDR too (I don’t know how well the smaller
versions of Lime would work though)

