Cellular Network Infrastructure

h1. Accelerate3g5 -- theresa

h2. Summary

We will integrate Osmocom 3G into our research testbed as one of multiple access networks that an end device can choose between as a data carrier.

The goal is to gather information on current network performance, e.g. cell load or congestion within the core network.

This information should be made available through a suitable API, e.g. for monitoring or to help clients choose between available access networks (Details TBD).

h3. Participants

* Theresa Enghardt (email: theresa@inet.tu-berlin.de, jabber: tenghardt@inet.tu-berlin.de)

h2. Details

Part of ongoing research at "INET":http://www.inet.tu-berlin.de/menue/internet_network_architectures/ (TU Berlin) on choosing between multiple access networks, related to the Socket Intents prototype (see "paper":http://conferences.sigcomm.org/co-next/2013/program/p295.pdf and "research prototype code":https://github.com/fg-inet/socket-intents).

The main research question is how to choose between different available access networks, such as 802.11 and 3G/4G, to optimize performance for the client. As opposed to current carrier's "offloading" approaches, we propose a solution controlled by the end device. Our prototype gathers statistics on the performance of the available access networks and aims to make better decisions on when to use which network. 

For this, it would be useful to get information about the current load of the network, e.g. of the cell or of the congestion within the core network. However, in proprietary cellular networks, this kind of information is usually not available to user devices. 

We want to investigate how to make it available within the network (e.g. for monitoring) and possibly to the user device.

More details TBD.

Also, we will carry out performance tests of the 3G data service under different load conditions.

h2. Journal

_2017-03-07_

Start. Set up wiki page.

_2017-03-16_

Inquiring about frequency regulations and how to obtain an experimental license.

_2017-03-28_

Request for Experimental radio license has been sent off.

_2017-04-24_

Request for Experimental radio license has been granted.

_2017-05-23_

First attempt to get the core network running with the example config with adjusted IP addresses. 

All components start up properly except the HNBGW which fails with "unable to bind socket: (null):0: Protocol not supported". Apparently it fails to set a local address/port before trying to connect IuPS/IuCS.

Will investigate further.

_2017-05-24_

Got the core network running. Apparently SCTP was not supported on my machine, now it is.

Configured the nano3G, but its NTP isn't working yet (85.10.199.217 does not answer). Looking for how to configure a different NTP server.

_2017-06-02_

The NTP server eventually worked without being reconfigured, so the HNBGW connection could be established. Connected a smartphone to the femtocell for the first time. Data service works.

h2. Conclusions

* In March 2017 in Germany it was possible to get a license for "Experimental Radio":https://www.bundesnetzagentur.de/EN/Areas/Telecommunications/Companies/FrequencyManagement/FrequencyAssignment/ExperimentalRadio/experimentalradio_node.html for the femtocell on UMTS band 5 (824-829 MHz and 869-874 MHz). 

** Granted for 24.04.2017 until 31.03.2018

h3. Performance measurements

*Setup*: Smartphone (LG K10 Android 5.1.1 Lollipop) -- Femtocell -- Core network VM -- Web server VM

*Workload*: Static web page, 32 objects of 200 KB each, downloaded via Chrome mobile browser

* about 30 concurrent TCP connections, each with an average throughput of 82 - 186 kBit/s

* total throughput varies between ~200 kBit/s and ~1.5 Mbit/s, moving average (8 seconds): ~1 Mbit/s

* RTT averages are between 90 and 500 ms per TCP connection (according to tcptrace), minimum values around 70 ms, maximum values around 800 ms

* see also graph "throughput-without-gtp.png"