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Call Proccess!

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Muhammad89

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How is the cellular phone call is actually done?



Muhammad89:D
 
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Dial the number and press SEND. :p
 
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Here is a basic introduction to the process for GSM systems:

**broken link removed**


It is different for CDMA systems, but the GSM information will give you a basic understanding.
 
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All phone MA's have the same basic scheme.

The primary principle is phone battery saving strobing and ring back time.

When you turn on your phone it registers with the system, letting the system know what cell tower you are near. Phone call addressing will be sent out to this area. As you move, say in a car, the phone detects it is no longer in one cell area and lets the system know it is under another cell site coverage area. The phone is always searching and evaluating neighbor cell sites for handover potential.

Phones are randomly divided into groups. Based on system set parameter, the phone wakes up periodically to see if their group is being paged. The battery saving strobe time is set by infrastructure system and can be anything from about a tenth of a second to over 5 seconds in cycle interval. The longer the time interval between wakeup's the better the phone's standby battery life. The longer the time interval the longer the possible ring back gap might be that could cause the originator to hang up prematurely. For example, if the battery saver cycle gap is 5 seconds, the call originator may get several fake system generated ringbacks before the recepient's phone is even woken up. So the phone may only ring once or twice where the call originator thinks it has rung 4 or 5 times.

Most systems use a setting of about 0.7 to 1.25 seconds for battery saver cycle.

Once the phone wakes up, it searches for its group address. If it detects its group then receiver stays on and looks for its complete ring address (ESN number association) in another time slot within a few milliseconds. If it does not detect its paging group the receiver goes back to battery saving strobe cycling.

About 20% of the time the phone gets wake up for its paging group but not its final address call. The false group wake up hurts the battery life only slightly.

If phone receives its final address, the system sets up to allocate a call channel to the phone, user answers, and call proceeds. The 'call channel' is different for different types of phone MA's. There is physical RF frequency, time slot, and in case of CDMA, a psuedo-code channel involved in call channel. So there is physical channel and virtual channel involved in definition of call channel.
 
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