Heterogeneous networks – hetnets, or WiFi offloading – are all the rage among carriers and equipment vendors, but it generally assumes the WiFi access point has a wired connection.
A group of Greek and UAE researchers has proposed a scheme for using wireless as the backhaul channel. The researchers are particularly looking at how offloading works in home settings, with the growing popularity of femtocells (eNB in the research paper) as ways for providers to stop customers straying off their networks to fixed connections. This is particularly pertinent in places where the fixed infrastructure is running behind mobile network deployment.
The problem is that with three different wireless networks in use (counting the home WiFi), there's a lot of potential for interference. As the Arxiv-hosted paper puts it:
“A UE [user equipment – El Reg] that is directly connected to the eNB, will experience interference caused by adjacent eNBs, which serve other UEs and APs at the same cellular frequencies. On the other hand, considering the eNB→AP→UE scenario, in the ﬁrst phase, the AP will experience interference from adjacent eNBs which serve other UEs and the APs at the same cellular frequencies, while in the second phase the UE experiences the interference from other APs that serve UEs at the same WLAN frequencies.”
So the researchers want to minimise that interference, without demanding any changes to the cellular network.
Their paper suggests that channel selection, and therefore the interference problem, can be handled at the user-side alone.
The user station uses SINR – the signal to interference-plus-noise ratio – to make two selection choices:
- Do I connect to the cellular network, the signal from the femtocell, or a WiFi network?
- How do I select a non-interfering channel?
Choose the right channel to make the hetnet work. Image: http://arxiv.org/pdf/1311.2970v2.pdf
As well as helping performance where the user device has to choose between as many as three signals, the extremely maths-heavy paper suggests the scheme could also help relieve traffic from the cellular network. ®