Most municipal wireless RFPs and requirements state the need for “seamless” roaming. I don’t know about you, but I always find the term “seamless” vague and a bit marketing-oriented. Also, I’ve seen municipalities and system integrators argue and shout at each other over the actual meaning of “seamless” during a time when the network is in the process of being installed. That’s not a good situation for either side of the deployment effort.
So, what’s the best way to interpret the meaning of seamless roaming? The definition I find most useful iswhere users can utilize their applications over the wireless network without any noticeable interruption as they move throughout the signal coverage area.
For example, someone should be able to talk over a wireless IP phone while walking through a city without experiencing a dropped call or substantial hiccup in the conversation. Additionally, a city employee downloading an inspection report while driving a car should be able to do so in a timely manner without having to restart the download process.
Roaming delays don’t have as much impact when downloading files as compared to using wireless IP phones. A five or ten second roaming delay with a file download will likely go unnoticed, but that level of delay during a telephone call will lead to a dropped call and furious users. Thus, the actual applications intended for use over the wireless network impacts how we should interpret the term “seamless.” Just be sure to get that straight when writing the RFP and defining requirements for the network. You’ll avoid a lot of grief.
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Jim Geier is an independent consultant and founder of Wireless-Nets, Ltd (www.wireless-nets.com), a consulting firm assisting municipalities, enterprises, hospitals, airports, and equipment providers with the development and deployment of wireless networks. Jim is the author of several books, including Deploying Voice over Wireless LANs (Cisco Press), Wireless LANs (SAMS), Wireless Networks ‚Äö?Ñ?¨ First Step (Cisco Press), Wireless Networking Handbook (Macmillan), and Network Reengineering (McGraw-Hill).
Esme/Jim
I agree with Jim’s comments re the definition of mobility. This is a critical piece of the puzzle that is often misunderstood or “fudged”.
For a presentation on achieving seamless hand-off and mobility on a metro Wi-Fi network, please see this mobility workshop presentation that was given at a recent the MuniWirless conference in MN: http://www.roamad.com/roamad/node/70
Martyn Levy
There seem to be multiple contenders reaching for the golden apple of seemless roaming, with big biz leading the way. Current contenders for the broadband wireless crown seem to be 802.20 and 802.16e, which are bogged down in a bit of a battle. See Guy Kewney’s article in the register (http://www.theregister.co.uk/2006/12/27/wimax_poliltics/) for an intersting take on the situation. I can envision an alternative solution coming from the grassroots movements, perhaps incorporating modified CuWin nodes.
I refer to Kewney’s article in reference to dropped voice packets vs. dropped data packets. Also, I have a data bias, where I tend to present more information via comments like these, while I mostly grunt and say “OK” on the phone.