Fujitsu Laboratories has developed a proprietary inter-cell
interference coordination (ICIC) technology that eliminates signal
interference at cell-edge areas covered by LTE base stations. The
technology autonomously allocates frequency bands in order to reduce
radio-wave interference in accordance with user distribution around
cell-edge areas of overlapping cells of each adjacent base station. The
solution will enable operators to double throughput at mobile-edge
areas, making it possible for users to access bandwidth intensive
services, such as video content delivery.
Fujitsu Laboratories Ltd. today announced the development of a
proprietary inter-cell interference coordination (ICIC) technology that
eliminates signal interference at cell-edge areas covered by base
stations of the cutting-edge long-term evolution (LTE) mobile phone
system. The new technology is able to autonomously allocate frequency
bands in order to reduce radio-wave interference in accordance with
user distribution around cell-edge areas of overlapping cells of each
adjacent base station. 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
This improvement in throughput will make it possible for users to
enjoy services—such as high-quality video content delivery—from any
location without interruption.
Details of this technology were presented at the 2011 IEEE 73rd
Vehicular Technology Conference (VTC2011 Spring), held in Budapest,
Hungary from May 15, 2011.
In recent years, there has been enormous growth in mobile
telecommunications traffic in line with the rapid spread of
smartphones. LTE, the latest wireless communications standard that
enables high-speed data communications of up to 150Mbps, is anticipated
to support the ever-increasing demand for mobile broadband services.
Even with LTE, however, in overlapping areas (cells) covered by
adjacent base stations, inter-cell interference can lead to a
significant degradation in user throughput and possible interruptions
to video delivery and other mobile services.
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.
As seen in Figure 1(a), signal interference becomes an issue at
cell-edge areas when other overlapping base stations utilize the same
frequencies. Figure 1(b) shows that by employing the frequency reuse
(FR) technique, in which each of the adjacent cells utilize different
frequencies, it is possible to reduce inter-cell interference. As a
result, however, the frequency bandwidth available to each cell narrows
and actually leads to lower throughput.
One way to overcome this issue is the fractional frequency reuse
(FFR) method (Figure 1(c)), in which only overlapping parts of the
cells undergo frequency reuse. This method allocates frequencies
between areas close to a base station (cell-center areas) and areas far
away from a base station (cell-edge areas). For cell-center areas,
transmission power is lowered and the same frequencies are used in all
of the cells. On the other hand, cell-edge bands have higher
transmission power and undergo frequency reuse.
However, the ICIC method in Figure 1(c) assumes that all areas are
equal. In actuality, however, inter-cell interference can still occur
for the following reasons:
- Signal propagation characteristics of areas differ due to topography and buildings
- Different areas with base stations that have varying transmission power and antenna heights
- Distance between base stations is uneven due to space constraints
Newly Developed Technology
To address these issues, Fujitsu Laboratories developed an ICIC
method for LTE that controls inter-cell interference by taking into
account the impact of cell configuration and user distribution.
As conventional ICIC methods did not adjust for imbalances in the
configuration of cells and the distribution of users, but instead
allocated frequency bands of cell-edge area according to a geographical
distribution of cells, adjacent cells could actually be using the same
frequency (left, Figure 2). This newly developed technology, however,
allows adjacent base stations to recognize each other's circumstances
and change the frequency bands of cell-edge area in order to reduce
inter-cell interference on users in the cell-edge areas.
In an evaluation of simulation results achieved using the newly
developed ICIC technology for LTE, when the configuration of cells was
not uniform and the distribution of users was imbalanced, transmission
speeds in the cell-edge areas roughly doubled compared to methods that
did not control interference. As a result, even if many users
congregate in the cell-edge areas, they can enjoy services, such as
transmission of high-quality video content, without interruption.
Fujitsu Laboratories will plan how best to incorporate the newly
developed ICIC into LTE base stations with the goal of commercializing
the technology in 2-3 years.
About Fujitsu Laboratories
Founded in 1968 as a wholly owned subsidiary of Fujitsu Limited,
Fujitsu Laboratories Limited is one of the premier research centers in
the world. With a global network of laboratories in Japan, China, the
United States and Europe, the organization conducts a wide range of
basic and applied research in the areas of Next-generation Services,
Computer Servers, Networks, Electronic Devices and Advanced Materials.