An assessment of potential bioeffects from exposure to cellular phone RF signals using TDMA, in particular GSM-type RF signals

The rapid proliferation of personal wireless communications devices, in particular handheld cellular phones, has raised concerns regarding potential bioeffects from exposure to the radiation emitted by these devices. Numerous experimental studies have been conducted in the quest for answers to the question of possible biological effects, but often the RF signals used have not been fully representative of all aspects of typical RF fields transmitted by cellular phones in actual use. There is now considerable experimental evidence which shows that ELF amplitude modulated RF signals can produce biological effects. This includes continuous, constant power TDMA/GSM type signals. But amplitude modulation of the wireless RF signals in actual use can be considerably more complex. For instance, in the GSM system the transmitted power can increase or decrease in stepwise fashion to minimize power consumption while maintaining an acceptable connection. In addition transmissions can be voice activated if Discontinuous Transmission (DTX) is allowed by the network operator. In this paper we investigate how the response to RF GSM using DTX and power regulation might be expected to change relative to the previously observed response to continuous burst modulated TDMA/GSM RF. Our analysis makes use of two standard data sets of transcribed two party telephone conversations, SWITCHBOARD and CALLHOME, to predict the distribution of transmit ON and transmit OFF times. Bio-effectiveness of TDMA/GSM type transmissions having ON/OFF times specified by these distributions is determined by comparison with our previous experimental results describing the variation of the bio-response to exposure with signals which are periodically turned ON and OFF, as a function of the ON time interval. We conclude that transmissions from TDMA/GSM cell phones in which DTX implementation can be represented by ON/OFF distributions derived from CALLHOME and SWITCHBOARD, can still be significantly bio-effective regardless of whether or not power regulation is implemented.