Fujitsu promises to double cell-edge throughput in LTE networks

Stuart Corner
Thursday, 19 May 2011 11:54

Business IT - Technology

Fujitsu has developed technology that it claims will double the effective bandwidth at the cell edge in LTE networks by co-ordinating cells' frequencies to minimise interference in boundary areas with high usage at the expense of increased interference in low usage areas.

Fujitsu presented details at the 2011 IEEE 73rd Vehicular Technology Conference in Budapest earlier this month, saying "By deploying this technology to base stations, it is possible to double throughput at cell-edge areas, which would otherwise experience reduced transmission speeds due to signal interference." It plans to incorporate the technology into LTE base stations with the goal of commercialising it in two to three years.

As defined by 3GPP, LTE uses a number of techniques to minimise interference between neighbouring cells, so called inter cell interference control (ICIC). As Fujitsu explains it, without any ICIC all cells use the full spectrum available and, inevitably, interference reduces throughput at the boundaries of the cells where their signal strengths are comparable.

One ICIC option is to use reduce power over the full range of the spectrum so that there is no overlap and have cells that are close to each other transmit at full power using different portions of the available spectrum so that there are no spectrum conflicts at the edges of the cells.

However with only a portion of the spectrum available at the cell edge, throughput is reduced. Furthermore it is impossible to construct a perfect scheme because propagation from base stations depends on many factors such as antenna height, topography, etc.

Fujitsu claims that its proprietary ICIC technique overcomes these limitations by allowing adjacent base stations to recognise each other's circumstances and change the frequency used to serve the cell-edge area and thereby reduce inter-cell interference for users in that location.

Such a change might well reduce interference between cell edges in one location at the expense of increasing it in other areas, by creating a new frequency conflict. Fujitsu, however, says its technique takes into account the distribution of users in cell edge zones in order to minimise interference - and hence increase throughput - in areas of highest demand.

It claims that "In the future, amid increasing volumes of mobile communications traffic, technologies for reducing signal interference at cell-edge areas will be crucial in allowing users to enjoy seamless mobile broadband services from any location," and that its ICIC technology will "make it possible for users to enjoy services - such as high-quality video content delivery - from any location without interruption."