B. VoiceAs mentioned in Section II

B. Voice
As mentioned in Section II the battery duration of mobile phones highly depends whether they are connected to GSM or 3G networks. In Table I are shown the values for power consumption on a Nokia N95 for both GSM and UMTS using the voice service, carried out with the testbed described in Section III. The power values for the calls have been obtained by making and receiving a phone call of five minutes duration and calculating the average of the power levels. The power consumption during the idle time has been calculating averaging the power levels over eight hours of idle mode. All these tests have been performed using a SIM card from Sonofon in Aalborg, Denmark. The results show that making a call using GSM costs 46% less energy and receiving a call costs 50% less energy than using UMTS. Being idle while connected to a GSM network costs 41% less than UMTS. To give an idea of the amount of energy that can be saved by using GSM instead of UMTS for voice services, in Table II some examples are given. They show the substantial amount of energy that could be saved and used for other tasks. For example making a one hour voice call with GSM instead of UMTS, would allow to send more than 1000 text messages of 100 bytes.