Table 1

Hypothesised explanatory variables included in the regression models and hypotheses regarding their influence on output power levels

VariableLevel of aggregation of informationCategoriesHypothesis
Network/study area characteristics
    Study centreIndividual12 centres (including one repeat study)Characteristics of the study location influence output power levels
    Network operatorIndividual36 operatorsTechnical characteristics of a network influence the efficiency of APC
    Time period of SMP studyIndividual2001–2002, 2003, 2004–2005Use of APC may have changed over time
Phone characteristics
    SMP modelIndividual4 SMP modelsDownregulation of output power under APC may depend on handset design
Call characteristics
    Duration of callPhone call<5, 5–10, 10–30, 30–60, ⩾60 sVery short calls may have higher average power due to the initial connection at high power level
    Time of dayPhone callDay 8:00–19:00, evening 19:00–23:00, night 23:00–8:00Calls during busy time of the day may have higher power levels as more handovers are expected when base stations are full
Phone use circumstances
    Frequency of use in urban/rural areasIndividualMainly urban, mainly rural, bothPower levels may be higher in areas with lower densities of base stations (ie, rural areas)
    Frequency of use in city centre/suburban areas (if urban)IndividualMainly centre, mainly suburb, bothIdem
    Frequency of use in a moving vehicleIndividualNever, less than half time, about half, more than half, nearly alwaysPower levels may be higher if phone is used often in moving vehicle due to frequent handovers
    Frequency of use inside buildingsIndividualNever, less than half time, about half, more than half, nearly alwaysPower levels may be higher inside buildings due to shielding of walls
User characteristics
    AgeIndividual⩽30, 31–40, 41–50, ⩾51 yearsPower levels may vary between age groups due to other, unmeasured factors
    GenderIndividualMale, femalePower levels may vary between genders due to other, unmeasured factors
  • APC, adaptive power control; SMP, software-modified phone.