The State of Open Source LTE

Open source implementations of pretty much all GSM network and UE components have been available for quite some time now and there are people that do use the software for private and commercial purposes. For many years now, for example, the Chaos Communication Congress has a dedicated private GSM network and, in recent years, a UMTS setup was added. And now, and I am very happy about this, the first successful attempt to also set-up a private LTE network has taken place at this years cccamp#19.

Hardware

LaForge has again set the bar higher a couple of notches by providing an LTE network at the camp. Here is a link to a slidedeck that describes the current state of LTE open source components and the network that was set-up. While he lists open source eNB implementations they don’t seem to be quite ready for prime time yet, so he used 6 (!) Ericsson RBS6402 small cells (the size of a Wifi access point) and connected them to a nextepc core network running on a Lenovo x240 notebook.

Software

He didn’t go into the details of how he managed to setup the IPSec gateway for the small cells nor how he managed to configure them so I have to ‘guess’ how that was done. I assume the IPSec tunnel endpoint handling is off the shelf but I would speculate that configuring the small cells requires understanding of non-standard Ericsson protocols. So I suppose a fair amount of reverse engineering was required. Amazing! In addition he had to come up with some translator code as the EPC uses DIAMETER to communicate with the subscriber database (HLR/HSS) while the OSMOCOM HLR implementation for 2G/3G uses MAP/GSUP.

Radio Stuff

On the RF side, the network started with 5 MHz channels on alternating channels to reduce interference and was then switched to 10 MHz bandwidth on a single channel with an average throughput of 33.6 Mbit/s downlink and 9.1 Mbit/s uplink.

Hat-tip to Laforge, this is fabulous!