Instant Messaging(IM) on Windows Mobile(WM) seems like it would be simple to implement with four major IM providers offering solutions.   However, when it comes to WM, not all solutions are created equal. GoogleTalk and Yahoo! only offer web browser based IM.    AIM has an application client which looks and works very well.   However, the overall winner is the Windows Live Messenger (formally known as MSN Messenger) client.  A nice advantage of the Windows Live Messenger is that the application comes embedded into WM and a login is the only setup step required.  Live Messenger sets itself apart further by offering one other feature; let’s call it ‘Push-toTalk’ IM.   Any microphone equipped WM device can record a message with just a single click to record and another click to send.  The voice clips are transmitted nearly as fast as any IM message and can be replayed multiple times or saved.   I was very impressed with the sound quality through such a simple connection.  All IM conversations can be archived and viewed at a later date.

Alternatively there are several 3rd party IM programs such as Fring or Agile for example, which facilitate the use of multiple simultaneous  IM carriers.  www.fring.com    www.agilemobile.com
While researching the Google solution I did find an application that showed much potential - Google Latitude.  With this free and easy to use application you can see the current location of all your contacts.  In the mobile arena or DSD, it is a great way to be able to see the location of all mobile assets. 
And for headquarters there is an iGoogle plug-in that integrates easily and allows for asset tracking.  Tracking is accomplished via assisted GPS and is therefore accurate within 1600 meters.  A GPS enabled device is not required.

Wireless Guru,

My company has twelve 802.11b/g wireless access points installed throughout a 185,000 square foot facility.  We recently deployed a large number of WiFi enabled mobile computers running the Windows Mobile 6.0 operating system.  We've encountered issues where devices freeze up regularly and lose their IP address.  Many times, the devices require a restart in order to reconnect to the WLAN.  We've verified that the signal stregnth is adequate throughout the building and all devices are configured correctly, what could be causing this?  Please Help.

Initially here is the problem that I think you are running into with your wireless infrastructure.  Though it may seem like a converged network, the stand alone access points/wireless routers will not communicate together and will therefore never negotiate a handoff or roam from one access point to another.  Each access point is broadcasting the same SSID and quite possiblly the same channel, and know nothing about each other.  Therefore there is a huge disconnect between what the handheld expects and what the multiple networks can deliver.  Bottom line, if a device ever roams correctly it is not by design but by chance and luck.  Whenever a device does have to roam it will have to disconnect from the network and then reconnect again, and that will only work if every access point is setup exactly the same.  And even if they are setup correctly you will still not be able to effectively roam.  In this setup each access point is a completely separate network.       Now you did not mention DHCP, but each of these units could be acting as a DHCP server, however in practice you never want to have more than one DHCP server and one in this scenario, will not work.

The solution to the problem is a converged network, a central controller which then controls all of the access points.  The controller has all of the network configuration and it manages all of the access points.  The controller will also manage all of the roaming and ensure that devices are always connected to the wireless network.    

To avoid the problems you are experiencing, centrally controlled or mesh is the only way to go in a multiple access point environment.  These type of networks are something we do have a lot of experience with, either troubleshooting or design and installation.

If you intend to design an Enterprise Wireless Network that performs well, detailed planning is critical.  Today I'm going to examine 5 key things to consider before moving forward with an Enterprise WiFi installation.

Site Survey      Do I need to get a site survey?   The answer depends on the expected use and performance of the WLAN. A site survey involves two different things - spectrum analysis and coverage mapping.  The spectrum analysis checks to see if there is any interference with other frequencies.  The coverage mapping simulates the access point placement to ensure proper coverage requirements.   Can a wireless system be installed without a site survey?   Yes, however proper coverage and optimal functionality can never be guaranteed.  Imagine building a model car in a dark room, it is going to take longer and you really don’t know what it looks like until the light is turned on.  A proper site survey allows you to see what you’re working with before, during and after the installation.  Also, it is important that a site survey be conducted during a normal working environment - with machines, forklifts and or people moving around - to ensure the operation will be properly scrutinized. 

Usage   What type of data will be going through the wireless network:  small data collection transactions, phone calls (VOIP/SIP), and or large file transfers?  Will users require the use of the wireless network while moving from one area to another?  Each of these types of questions corresponds to important design requirements.   For instance, if users will be moving around then 100% coverage will be required to and from each of these areas and the system must be capable of roaming users between access points.

Coverage    What are my coverage needs?  Do I need to cover the entire building/facility?  Can this change in the future? This will answer how large the wireless system needs to be initially and does it need to be scalable enough to facilitate the rest of the building or another building entirely in the future. Planning in the beginning will save future costs in time, performance and money.  

Area Layout and Obstacles   The thing to remember here is that metal is the enemy; it can completely block signals as well as create multipath, which can confuse access points.  Special considerations need to be taken when looking to install wireless infrastructure in an environment that contains a lot of metal – including the building’s construction.  Water and other liquids can present problems as well. Since the human body is composed of mostly water, people can also obstruct wireless signals and limit the utilization of a WLAN.

If you are looking for additional assistance, contact RACO's Advanced Solutions Group (ASG).  RACO's team of network engineers are certified in both Motorola and Cisco wireless networking technologies and have integrated these components into a multitude of corporate networks.

To encode the tags we are using a Zebra R110Xi RFID printer. 

The configuration is for vendor compliance in a 3PL or third party distribution center.  The tags will be read as the SKUs are moved through the dock doors and read again as they enter their vendor destination.

Setting up the reader

The XR400 has 4 possible antenna pairs.  Two antennas, a Tx and Rx.  Each pair can be one choke point or portal.  A shipping dock door for instance would be a good choke point.  Using epcSolutions software simplifies the setup process since it is designed for vendor RFID compliance.   There were three main troubleshooting issues we ran into while configuring the software to start the reader polling and setting the proper RFID tag type.

The first problem was actually finding the reader on the network in order to enable us to log into the Administrative Console via its IP address a web browser.  The “default” IP address was not correct and even after resetting the XR400 it did not take on the default IP.  By plugging the XR400 into a switched network and running Wireshark on another computer, we were able to see broadcast packets coming from a 192.168.0.73 address. Putting that address into a web browser got us into the Administrative Console.  The default user name is admin with a password of change. 

The second problem was that the epcSolutions software was unable to “start the reader”. Through some trial and error we discovered that the XR400’s polling was the issue and had to be disabled in the Administrative Console in order to let the software start the polling itself.  With polling enabled the software is unable to start the reader and gives an error that says, “Symbol reader returning error status 0x80”.  The polling option is under the “Scan Control” menu item.

Next the tags we needed to read were Generation-2, Class-1 (G-2, C-1). 

This is setup within the XR400 Administrative Console, under the “Read Point Class” menu option.  Then assigned to an antenna pair/portal.

After clearing those hurdles the tags are now being read and all the lights are green.  One of the major problems that must be dealt with when configuring RFID is that tags are automatically read and will continue to be read every 1 or 2 seconds for as long as the tag remains within the polling area.  Therefore, whatever data collection software is used as an RFID manager it must be ready to manage multiple reads.  

The little screencast Video shows how often or quickly the tags are read and reread.

http://www.screencast.com/t/nQ3TyCV82

Here are the five most common factors overlooked in wireless networks.

   ·         Wireless Infrastructure – What works at home is not intended to work commercially.  Production environments require much greater levels of dependability, availability, and mobility.  The basic rule is anything available at the department or office supply stores, is not intended for commercial use.  What they lack is a more rugged dependability, roaming capability, and a single point of configuration.

  ·         Placement of Access Ports – Take the high ground.  Whether 802.11b/g(2.4 GHz) or 802.11a (5.0 GHz), antennas need a good vantage point to effectively ensure Wi-Fi coverage.   Depending on the environment that a Wi-Fi network is in the signals will propagate differently.  For instance liquids and dense paper products will soak in and dampen radio signals, where metals will block and reflect.  Simply placing access points in the middle of each open area may well not be adequate.  

 ·         Channel Separation – A case of selective hearing.   If you turned on a radio and instead of hearing your favorite station, found yourself listening to all of the stations at once, it would be very difficult to filter out just the programming that you intended to hear.  In a multi access port environment, mobile devices can filter out anything sent from neighboring access ports through channel separation.   Below is a diagram of 802.11b/g channel separation.

Only three channels (represented in red) are able to be simultaneously used and remain completely separated.  These frequencies correspond to channels 1, 6, and 11.        

·         Antenna Selection – Fitting a square into a round hole.  Omni-directional antennas are the simplest to plan and deploy.

With a limited number of channels however, omni antennas can be difficult to deploy in environments that are more complex than a simple four wall rectangular shaped building.  When dealing with troublesome Wi-Fi elements, (metal, liquid) directional or patch antennas offer coverage that is far more dependable.

Clean Wi-Fi Network