Wpan

TH3B-2

Millimeter-wave OFDM WPAN system
applying adaptive modulation for grouped sub-carriers
Yozo Shoji, Chang-Soon Choi, and Hiroyo Ogawa

National Institute of Information and Communications Technology (NICT),
Incorporative Administrative Agency, 3-4 Hikarino-oka, Yokosuka, Kanagawa, 239-0847, Japan
Tel: +81-46-847-5075, Fax: +81-46-847-5440, E-mail: y
ie g
microwave systems. Theconventional mmW systems which
have been targeted so far were point-to-point application
systems, such as fixed wireless access systems, wireless
IEEE1394 system, and so on. The designing of these systems
was based on the assumption of employing high-gain antenna
and it means the wireless channel becomes less sensitive to
multipath interference. On the other hand, the mmW WPAN
systems can notavoid to use a low gain and broad beam width
antenna to support a wide angle of signal arrival excepting the
cases introducing a very narrow beam antenna or applying the
advanced adaptive beam forming technology. Therefore, the
received signal is usually supposed to suffer from severe
multipath interference.
The use of orthogonal frequency-division multiplexing
(OFDM) transmission schemeis known as an effective way to
mitigate selective multipath fading effects in wireless channels.
Furthermore, it is also well-known that the use of OFDM is
suitable and effective way if an adaptive modulation technique
is required under the frequency selective fading channel
because the OFDM system can easily apply the adaptive
modulation with respect to each subcarrier independently.
Wehave measured the channel characteristics in 60 GHz
and 70 GHz band indoor so far by using comparatively broad
beam width antennas, and already demonstrated the channel
become frequency selective even if the signal bandwidth was
less than 100 MHz [2]. In such selective channel environment,
we demonstrated the OFDM signal transmission, and we were
able to obtain the experimental results whichmade us
anticipate that applying adaptive modulation in mmW WPAN
system improves the throughput performance [2]. Therefore,
we newly developed mmW OFDM WPAN system which
implemented adaptive modulation function.
For developers of mmW OFDM WPAN systems, the costeffectiveness, tolerability to the phase-noise, and the solution
to the flat signal fading are also important issues besides thesubject of immunity to the selective multipath fading.
To overcome these problems, we have developed 70-GHzband RF transceivers equipped with combining receiver
diversity based on the millimeter-wave self-heterodyne

Abstract - Millimeter-wave OFDM wireless personal area
network system applying adaptive modulation for grouped subcarriers was newly developed. It is composed of 100MHz
samplingspeed OFDM modems which can employ adaptive
modulation for every 8 neighbored subcarriers, and 70-GHz
band self-heterodyne transceivers equipped with receiver space
diversity. The detailed specifications and the expected maximum
throughput performance are described. The operational
principle of the developed system under selective multipath
channel environment is also discussed. The fundamentaltest
results demonstrate the use of developed adaptive modulation for
millimeter-wave OFDM WPAN system has the possibility to
improve the throughput performance under multipath channel
environment.
Index Terms -millimeter-wave, wireless personal area
network, OFDM, adaptive modulation, grouped subcarriers
I. INTRODUCTION

Millimeter-wave band wireless communication systems
have beenexpected to enable very high-capacity wireless
transmissions and device miniaturization because of their
available broad bandwidth and shorter wavelengths compared
to the conventional microwave systems. In particular, the
formation of task group in IEEE for the standard of
millimeter-wave personal area network (mmW WPAN),
IEEE802.15.3c[1], has created an explosion of interest in
technologies...