|
Yui-Wah (Clement) Lee, PhD |
Member of Technical Staff
Bell Laboratories
High Speed Mobile Data Research Department
600 Mountain Avenue
Murray Hill, New Jersey 07974 USA
Room 2A-338
Wireless intelligent sensor networking (WISN) will enable radically
new ways for an information system to interact directly with the physical
world, and as such it will have widespread and fundamental implications.
It will be key to the next-generation telecommunication systems.
Our research program encompasses the following aspects. The synergy
of WISN and wide-area networking, especially wireless wide-area networking
(WWAN), such as those embodied in CDMA2000 1xRTT, CDMA2000 1xEVDO, and
UMTS. The design and implementation of a reusable framework that
allows fast deployments of WISN in new application situations. The
potential of data-fusion and machine-to-machine (M2M) techniques in WISN.
Topology awareness and its benefits in the design of an energy-efficient
management protocol for WISN.
In a public WLAN hotspot, a roaming mobile terminal (MT) may be
within radio range of more than one access point (AP), each of which may
or may not have roaming agreements with the service providers of the user
of the MT. In this case, the MT may need to discover some service
information before it can make an intelligent network-selection decision.
The most critical is roaming information; while other information such
as security policies, price, AP workload may also be useful. Currently,
roaming information is typically provisioned on the MTs as static roaming
tables or roaming lists. However, this approach may not scale well
when there are millions of hotspots globally. Addressing this shortcoming,
recently several solutions have been proposed by different groups.
We also proposed our own solution called Roaming Information Code (RIC),
which can be transported as SSID or a new Information Element of the 802.11
standard. RIC is scalable and can be fully backward compatible with
existing APs (if transported as SSID). Furthermore, it does not hinder
fast handoffs. We also proposed two other schemes addressing the
other service information: a scheme called RIC-VAP for provider-specific
security information; and a scheme that allows an AP to announce price
and workload information. (paper
in ACM WMASH'2004)
The main goal of the project is to enable a wireless carrier to
provide a combined wireless data service using the two important yet complementary
access technologies: 3G wide-area cellular and Wi-Fi (802.11) local-area
wireless. We have been building two new network elements: a Wi-Fi
gateway appliance and a multi-interface mobility client. The former
is an integrated box to be put in a Wi-Fi hotspot and provides various
services including access control, mobility (Mobile-IP), accounting, QoS,
and web caching. The latter is a Mobile-IP client that can intelligently
switch to use the best available network interfaces based on the signal
strengths and priorities. We have been able to demonstrate
seamless handoffs between a CDMA2000 network and a Wi-Fi network since
early 2002. (paper
in IEEE Communications Magazine)
An important technique for wireless multimedia is content adaptation
-- the on-demand transcoding of multimedia from one format to another or
from one fidelity to another so as to fit the specific needs of bandwidth-
and resource-limited wireless terminals. We designed, implemented,
and evaluated a content-adaptation server called Gamma, which supports
the automatic and transparent transcoding according to pre-configured user
profiles. Gamma has a table-driven architecture and runs on a cluster
of network computers. It is thus very extensible and scalable.
Furthermore, the design of Gamma is novel in two aspects. First,
we emphasize on the incorporation of third-party transcoding programs.
Second, we abstract out content-adaptation as a generic service for wireless
application and decouple the former from the latter. As a result,
Gamma can accommodate a broad spectrum of third-party transcoding utilities
for video, image, audio, presentation, documents, etc, and can support
four different wireless applications that need transcoding services: email
proxy, web proxy, email recomposer, and email outbox. In our experiments
of accessing multimedia web objects over a real 3G1X airlink, Gamma delivered
very significant performance improvement - reduction of access latency
by up to 83% and reduction of network traffic by up to 99%. In another
set of experiments, we found that Gamma is very scalable and has a very
small overhead -- as low as 180 milliseconds per transcoding task.