Friday, October 03, 2008

zBoost Cell Extender: Refinement Post

This is a refinement, or follow-up, to my first post about cell signal boosting with zBoost:

While the base station allows decent communication over a specific area once a data or voice call is established, it seems to have little or no ability to propagate the signaling part of the GSM protocols when there is no connection established.

This symptom means that the network is unaware of a handset, and a handset thinks there is no service. As a result, it often will not even try to make a call.

Once the handset decides there's a network -- usually by picking up a very faint signal from a real tower -- it will attempt the call and then discovers a near-perfect connection.

zBoost may not be responsible for this behavior -- the product docs specifically say that you have to have some real signal level in order to use the repeater. I had imagined this restriction was solely due to the zBoost device needing a tower to talk to (it cannot bridge to another backhaul) -- but in fact it may also be due to zBoost's inability to simulate the idle signaling between the handset and the tower. That is, you need a tower to make or get a call, but the zBoost can boost the data in the call stream.

So what does this all mean?

Well basically that if your RF visibility to a tower is marginal, as mine is, zBoost may still be able to help. But you don't want to rely on this to reach 911 or make any other kind of need it right now phone call, as it might take you a few minutes of moving around or monkeying with the phone to get it to realize there's any service.

Likewise, if you absolutely positively cannot miss an incoming call, this may not be the solution for you, although, interestingly, incoming signaling (calls and SMS) seems to be stronger/prioritized traffic from the tower than idle updates, and so gets to the handset more frequently, without any kind of booster present.

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