A secret government agency with a project codenamed “InterfereX” does sound a bit like something from “Men in Black”. Fortunately, we’ve avoided the memory wiping beams to report on this unusual research which may be incorporated into femtocells at some time in the future. We spoke to Dr. Mark Reed from NICTA, an Australian research agency, very early one morning.
About NICTA
NICTA is an Australian government funded R&D centre with around 600 staff. It’s designed to spin off startups and unlike some universities has commercialisation support built in. They’ve had some success with a number of startup companies developing products such as providing professional quality Audio over Ethernet, Software virtualisation on mobile phones and fibre backhaul monitoring.
About InterfereX
The InterfereX project is led by Dr. Mark Reed, who has worked in Europe for Ascom and the European Space Agency on various radio projects. He has built up a team, which has developed the femtocell uplink interference cancelling (ULIC) solution.
The invention improves the uplink performance of mobile phones using a femtocell, especially when used concurrently. It cancels out the interference caused when two devices sharing the same femtocell (and the same frequency) interfere with each other. If a non-femtocell user is connected to a macrocell in the same area, then the solution could actively cancel this interference too (If certain parameters are available – which is under consideration by 3GPP currently).
NICTA have filed a number of patents relating to this invention.
Uplink IC (ULIC) techniques are practical and have been realized by ZTE and Qualcomm in macro base station deployments and a June 2009 press release stated that this provided benefits in terms of improving data throughput by up to 60% and voice capacity increase by up to 45%. Up to now, these have been used in the macro network and NICTA have adapted and optimised this technology for use in femtocells.
Limitations
This technique has been demonstrated currently for WCDMA – they’ve not looked at CDMA, LTE or other technologies. Work on HSPA and Interference Cancelation is underway and is a natural extension of the current approach.
Benefits
The range of the femtocell can be increased, uplink data throughput improved and interference to the macrocell reduced (because the mobile handset uplink power is reduced).
These improvements are complementary to the interference avoidance techniques proposed in the 3GPP standards and by the Femto Forum.
To better understand the network benefits of ULIC the InterfereX team have peformed an extensive two-tiered system simulation (ie. Femtocells co-located with a macro cell system) model using 1000’s of users and 100’s of femtocells (and some macrocells). The team had assumed conservative figures of just 2% femtocell penetration in the simulations – Mark believes this is a very conservative figure (some industry estimates are working on interference solutions for penetration as high as 20%). Higher penetrations would make this technique even more valuable.
Implementation
The team have built a hardware prototype of an entire WCDMA modem including the ULIC in RTL/HDL (logic language) with real-time processing of their algorithm. This is running on a standard FPGA chip, using a 3rd Party RF front end and a software driver up to the Iub interface.
To be clear, this isn’t a “bolt on” module, in hardware or software. What they have developed is a complete real-time WCDMA femtocell modem which includes the interference cancellation. Today’s femtocell price point means that a dedicated custom chip with the WCDMA design in logic needs to be used to be commercially viable – FPGA designs won’t achieve this when volumes increase dramatically – so their design is on a roadmap to be productized into an Application Specific Integrated Circuit (ASIC). As the design is entirely in logic this minimizes the cost (die size) and heat dissipation, two key requirements.
Mark believes there are also a significant number of large chip vendors who don’t have a solution today and this could be interesting to them. When incorporated into a custom chip design, he doesn’t forsee any additional cost of the solution compared to currrent products on the market.
Mark has been working with a number of USA based entrepreneurs and talking to several chip/silicon vendors interested in the technology.
Find out more
You can view a YouTube video or just read the text on the project web page project web page
