Head exposure to cellular telephones: A system-level study

This work is aimed at quantifying the effects of a number of system-level parameters and conditions on the amount of non-ionizing radiation dissipated in the head of cell phone users in the 850 MHz band. The three major cellular technologies of today, namely, GSM, CDMA2000 1X and UMTS, are evaluated. Five randomly chosen commercial products from each technology are investigated in terms of their Specific Absorption Rate (SAR) and maximum transmit power, as reported by the US Federal Communications Commission (FCC). A statistical system model for urban and suburban cells is used to calculate, with the help of the uplink power budget and the corresponding power control mechanisms, the statistics of the phone transmit power via Monte Carlo simulations. A linear model relating SAR and transmitted power is then used to obtain SAR statistics over the entire cell. Results show some minor differences among the technologies considered, and also between urban and suburban environments, but more importantly, they show a strong correlation between SAR levels and the percentage of cell area that is covered, which in turn depends on key system design parameters such as cell density, cell tower height, and the use of certain RF techniques.