T-Mobile's UMA technology 

Make or receive mobile phone calls without utilizing my minutes? Browse the internet or send wireless e-mails without worrying about the amount the data I will use? All of this while receiving near flawless voice reception? Yes, this is all possible and the technology is readily available and easy to begin using today.

It has been over a year since T-Mobile has released its UMA (Unlicensed Mobile Access) technology for mobile phones and mobile users have yet to truly take advantage of this amazing technology. Very simply, mobile phones with UMA, like the BlackBerry Curve and 8900, allow the user to send and receive phone calls over a WiFi network. Data transactions including e-mail access, WAP and internet browsing can also occur. This gives the user the unique ability to receive near flawless reception while not utilizing minutes or data from their wireless plan. As long as as you have access to a WiFi network, you can begin taking advantage of this technology with a few, easy setting adjustments. This can take place at home, at work or anyplace where you can access a wireless network regardless of the quality of the cellular signal. The mobile device will even remember previous networks and automatically connect your mobile device as long as the settings have not changed.

Unlike wireless SIP, VoIP or Skype smartphone applications - UMA allows a user to seamlessly transition back to the GSM network when talking out of WiFi range.  This allows a user to start a phone conversation at the workplace or home where a 802.11 b/g  network is available and continue the conversation, uninterrupted, when walking or driving out of range.

Want to learn more? Contact a RACO Wireless sales representative to learn about T-Mobile's UMA technology and how it can improve your mobile needs.

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.

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