CDMA and TDMA Interference

[ChaosThyre81]

Why doesn't CDMA cause my speakers to make noise like a Nextel or Cingular phone does?? They're both producing EM waves so I don't see why TDMA does it and CDMA doesn't.

Are all the conversations coded differently in TDMA (iDEN) or do they all use the same coding (encryption?) where they can interfere with each other, like hearing someone else when I'm on the phone with someone who has Nextel.

Thanks,

M

[Scrumhalf]

The simple explanation is that this is a function of the modulation method used by TDMA vs. CDMA.

TDMA shares bandwidth between mutiple users by splitting up their transmissions into multiple timeslots, i.e. the transmit/receive happens in rapid succession between users, each in their own timeslot.

The buzzing that you hear from any TDMA technology (by the way, GSM is a TDMA technology as well and you can hear the buzzing from both IS-136 and GSM) is related to the frequency related to the timeslot length (frequency is of course inversely proportional to the timeslot length). So basically, it is a function of the nature of the modulation technique of TDMA.