Subject: [NEXTEL-1] Padcom's Intelligent Modem Querying reduces congestion on W-WAN's

From: Marcel <[email-masked]>
Date: Sun, 15 Dec 2002 13:50:01 -0500

Reducing Congestion
on Wireless WANs
By Chris Bogdon
 and Mark Ferguson, Padcom Inc.

The wireless marketplace in the United States is in the midst of
unprecedented growth. While the introduction of new technologies
will further contribute to the expansion of this market, the
challenge will be to ensure that networks are used efficiently. If
this does not happen, networks will become oversaturated with
packets, resulting in decreased application response time and
increased packet loss. For wireline networks, Ethernet switches
are usually a viable means of keeping network congestion in check.
Congestion on a wireless network, however, is more complex. To
maximize the usefulness of the wireless network and keep customers
satisfied, congestion must be kept to a minimum.

Since many wireless networks are migrating from proprietary
interfaces to IP standards, users can now employ wireline
applications in a wireless environment. Although this is great for
application developers and end users, it can have a damaging
effect on the network. Many applications, like web browsers, are
the standard interface for applications. While the applications
work well with 100MB Ethernet networks, wireless infrastructures
are not suited to handle the increasing amounts of web content.
This leads to network bottlenecks that slow user productivity and
increase user frustration.

      Wireless Network
     Speed Range

      Satellite
     2,400 Bps - 9,600 Bps

      Mobitex  (Blackberry)
     8,000 Bps

      CDPD
     9,600 Bps - 19,200 Bps

      Private RF Technologies
     4,800 Bps - 19,200 Bps

      Motorola RD-LAP
     9,600 Bps - 19,200 Bps

      DataRadio
     9,600 Bps - 32,000 Bps

      M/A-Com OpenSky
     19,200 Bps

      GPRS
     56KBps

      CDMA 1xRTT
     144KBps

      Wireless LAN
     1 MBps - 54 MBps

As the above chart shows, the majority of wireless networks are
still less than 19,200 Bps. Although 3G wireless networks are
becoming faster, they are still slower than most wireline
networks. One means of easing the complexity of wireless networks
and reducing the possibility of congestion is to combine a
lower-speed cellular network with a higher speed alternative, like
wireless LAN, creating a single virtual network. When mobile users
are within range of a specified wireless LAN, applications will be
offloaded to this network, thereby reducing congestion on the
cellular network.

While middleware companies have been creating intelligent multiple
network solutions since the mid 1990s, carriers and other service
providers are just now starting to realize the need for this type
of solution. Cellular carriers are embracing wireless LANs to
reduce network congestion and wireless data users are taking
advantage of the benefits of using multiple technologies. With the
growth of wireless communication, solutions of this nature can
reduce network congestion.

An important factor when developing a multiple network solution is
the strength of the out-of-range detection algorithm. Switching
between two types of networks requires an action that predicates
the physical switch in networks to occur. In most cases, the
switch will be initiated any time the user goes out of range of
one wireless network. However, how does the roaming algorithm
detect the moment the transceiver has left the coverage? Also, how
can a multiple network roaming solution use other types of
criteria than just plain network coverage?

One approach to solving the problem of wireless roaming is to
apply the solutions used on wireline networks. One such solution
is to run server applications that can determine if a client's
computer is actively communicating with the server. The server (or
client) will send end-to-end keep-alive packets or broadcasts to
detect when the user is no longer communicating. If the user doesn
't respond to this keep-alive message, it can be assumed that user
is no longer using the network. The downside of this solution,
however, is that it creates unnecessary packets on the network:
the more keep-alive messages being sent, the more congested the
network becomes.

As mentioned earlier, Ethernet switches are another way to reduce
congestion on wireline networks. The switches are placed between
client and server computers to provide dedicated bandwidth.
Unfortunately, a solution like this cannot work on a wireless
network, since all users are, in effect, sharing the frequencies
used during communication sessions. There is no method of
allocating a single channel to give a user a virtual bandwidth
pipe without affecting the other users on that frequency.

For wireless networks, a better solution is to address the problem
of the roaming detection algorithm. One way to do this is to
intelligently query the transceiver to determine if a user should
roam into a different network. Normally, this process requires a
close coupling between the application and the transceiver used to
access the network. One of the benefits of querying the modem is
that the application can determine critical status information
without incurring network overhead. In the minimal configuration,
an application would be able to determine the received signal
strength of the current base station. Collecting information this
way does not produce any network overhead. Therefore, the
application can determine instantly whether the user is in range.
In other advanced uses, signal strength can be used to provide
input to advanced algorithms to approximate when a user will lose
connectivity. Applications can be written to statistically
determine when that user will be out of range based upon his
current behavior.

The ability of some modems to determine the network registration
status -- in other words, if a user is in a home or roaming
state - further enhances the ability of this solution. These
parameters create improved roaming algorithms, resulting in a
better experience for the end user. A case in point is setting the
parameters to allow mobile users to automatically switch to a less
expensive network when possible.

Due to the unique characteristics of wireless networks,
specialized solutions like modem querying must be developed to
address the problem of network congestion. These solutions will
ensure the scalability of wireless networks as the industry
continues to grow.

Chris Bogdon is Chief Technical Strategist at Padcom, Inc. He is
responsible for helping determine the future direction of Padcom
products, and helps to identify synergies between Padcom's
products and other companies in the industry. He has been with
Padcom for over seven years and has a B.S. in Computer Science
from the University of Pittsburgh. He can be reached at
[email-masked].

Mark Ferguson is Director of Marketing & Strategic Planning at
Padcom, Inc. and is responsible for forging business relationships
and maintaining the company's media and advertising presence. He
has been with Padcom for two years and has a M.A. from Lehigh
University. He can be reached at [email-masked].

WirelessDesignMag.com

http://www.WirelessDesignMag.com/scripts/ShowPR.asp?PUBCODE=055&ACCT=0000100&ISSUE=0212&RELTYPE=WEF&PRODCODE=00000&PRODLETT=B

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/