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rradina
join:2000-08-08
Chesterfield, MO | reply to patcat88
Re: Throttling? said by patcat88:Thats GSM TDMA for you (not sure if an iPhone and ATT do voice calls over WCDMA). CDMA2000 does very good Radio Resource Management, the phone can tune to multiple towers and use their bitstreams for error correcting each other. If I interpret this correctly, multiple cells are getting my packets and transmitting them and my phone can pick and choose which one to use. This is a good strategy to keep a stream flowing consistently but it seems very wasteful in crowded cells -- especially as cells get smaller and have to handle relatively fast moving mobile users. In that scenario, it seems likely that one mobile connection might consume bandwidth on half a dozen micro cells to make the hand offs work smoothly.
As I mentioned before, adding more and smaller cells seems to work for relatively stationary mobile users but there seem to be ever increasing complexities as cell counts, simultaneous connections and hand offs rise.
Is this a case of most mobile calls are relatively stationary and therefore not that many calls have to consume bandwidth on multiple, adjacent cells? | |
patcat88
join:2002-04-05
Jamaica, NY
kudos:1 | said by rradina:As I mentioned before, adding more and smaller cells seems to work for relatively stationary mobile users but there seem to be ever increasing complexities as cell counts, simultaneous connections and hand offs rise. Is this a case of most mobile calls are relatively stationary and therefore not that many calls have to consume bandwidth on multiple, adjacent cells? Not necessarily,
quote:
again in non-CDMA networks when the user behaviour changes, e.g. when a fast-travelling user, connected to a large, umbrella-type of cell, stops then the call may be transferred to a smaller macro cell or even to a micro cell in order to free capacity on the umbrella cell for other fast-travelling users and to reduce the potential interference to other cells or users (this works in reverse too, when a user is detected to be moving faster than a certain threshold, the call can be transferred to a larger umbrella-type of cell in order to minimise the frequency of the handoffs due to this movement);
»en.wikipedia.org/wiki/Handoff | |
rradina
join:2000-08-08
Chesterfield, MO | That's a good idea. If the micro cells are on a different piece of spectrum, that would work really well.
The only thorn in this strategy is how well do "large cells" work in a city with lots of tall buildings? It's pretty easy to imagine how the every-street-corner micro cells work...there's always one within line-of-sight. Of course given the traffic in a big city, we need a definition of "fast travelling" user. | |
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