Cutting-edge Technologies
Software Defined Radio Technology —Reconfigurable
Multimode Radio Terminal through Changes in Software
Probabilistic Dual-Cost Method for Conveying
Information to the User in a Short Spoken Dialogue
Software defined radio (SDR) technology enables a wireless terminal to support various kinds of wireless systems and services,
such as second- and third-generation mobile systems (PDC*1,
PHS, W-CDMA*2, GSM*3, etc.) and wireless LANs. By simply
changing the software to reconfigure the terminal, users will be able
to enjoy various wireless services in a seamless manner.
NTT Laboratories have developed an SDR prototype that supports both PHS and IEEE*4 802.11 wireless LANs and a direct-conversion multi-band MMIC*5. Conventional SDR prototypes can
support only narrow-bandwidth (up to a few 100 kHz) systems such
as PHS, but not wideband systems like wireless LANs that use
direct sequence spread spectrum (DSSS) techniques due to the
limited performance of the processor. To overcome this limitation,
we have developed wideband flexible-rate pre-/post-processors
(FR-PPPs) that enable the prototype SDR to support both PHS and
wireless LANs.
We are continuing our research with the objective of developing
a hand-held SDR mobile terminal that is as small as current mobile
terminals and has the same low power consumption.
(Network Innovation Laboratories)
Spoken dialogue systems perform tasks like information retrieval
and reservation through spoken conversations with users. While
speech communication is easy for human users, it is difficult for
computer systems to recognize users' speech correctly. An ordinary way for a system to deal with speech recognition errors is to
confirm the user's request and determine the contents of the
request when receiving acknowledgements from the user. Once
the request has been determined, the system tells the user what he
or she wants to know. While confirmation is required when there is
a speech recognition error, omitting avoidable confirmations would
make the dialogue smoother.
Conventional spoken dialogue systems tend to promote a
lengthy dialogue because they focus only on the length of the
exchanges for confirmation and do not allow for the length of the
system's response for conveying information to the user. The
length of the exchanges for confirmation has a trade-off relationship
with the length of the system's response, and the total length of the
dialogue cannot be reduced without considering both portions of
the dialogue. To overcome this problem, NTT Laboratories have
developed a novel dialogue control method called "probabilistic
dual-cost". It controls a dialogue so as to minimize the sum of the
length of the exchanges for confirmation (the confirmation cost) and
the length of the system's response (the information transfer cost).
The confirmation cost depends on the speech recognition accuracy,
and the information transfer cost depends on the contents of the
system's database. By minimizing the sum of these two costs, the
probabilistic dual-cost method avoids the unnecessary exchanges
that are inevitable with conventional methods and conveys information to the user in a shorter dialogue. We will improve our proposed
method by enhancing the accuracy of the cost estimation.
(Communication Science Laboratories)
*1 PDC: Personal Digital Cellular
*2 W-CDMA: Wideband Code Division Multiple Access
*3 GSM: Global System for Mobile Communications
*4 IEEE: The Institute of Electrical and Electronics Engineers Inc.
*5 MMIC: Monolithic Microwave Integrated Circuit
Service image
W-CDMA,
PDC...
Home
SDR Terminals
IEEE802.11a,
W-1394...
AP*2
Conveying information to the user with shorter dialogue
Probabilistic dual-cost method avoids
this portion if no current warnings
for anywhere in Japan.
Upgrade by
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*1
HiSWANa...
AP
Kanagawa...
IEEE802.11b...
Public Service Area
System
User
Office
Yes
*1HiSWANa: High Speed Wireless Access Network type a
Kanagawa?
*2AP: Access Point
Weather or warning?
SDR prototype and direct-conversion multi-band MMIC
Weather
database
Confirmation
Warning
Warning?
Yes
Conveying
information
No current
warnings
anywhere
in Japan
There are no current
warnings for anywhere.
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