▁to ▁each ▁user ▁to ▁obtain ▁highest ▁gain ▁in ▁the ▁direction ▁of ▁that ▁user . ▁This ▁is ▁often ▁done ▁using ▁ph ased ▁array ▁techniques . ▁ ▁Use ▁in ▁Cell ular ▁Network s ▁ ▁G SM ▁ ▁In ▁G SM ▁cell ular ▁networks , ▁the ▁base ▁station ▁is ▁aware ▁of ▁the ▁distance ▁( but ▁not ▁direction ) ▁of ▁a ▁mobile ▁phone ▁by ▁use ▁of ▁a ▁technique ▁called ▁" tim ing ▁advance " ▁( TA ). ▁The ▁base ▁trans ce iver ▁station ▁( B TS ) ▁can ▁determine ▁how ▁far ▁the ▁mobile ▁station ▁( MS ) ▁is ▁by ▁interpre ting ▁the ▁reported ▁T A . ▁This ▁information , ▁along ▁with ▁other ▁parameters , ▁can ▁then ▁be ▁used ▁to ▁power ▁down ▁the ▁B TS ▁or ▁MS , ▁if ▁a ▁power ▁control ▁feature ▁is ▁implemented ▁in ▁the ▁network . ▁The ▁power ▁control ▁in ▁either ▁B TS ▁or ▁MS ▁is ▁implemented ▁in ▁most ▁modern ▁networks , ▁especially ▁on ▁the ▁MS , ▁as ▁this ▁ens ures ▁a ▁better ▁battery ▁life ▁for ▁the ▁MS . ▁This ▁is ▁also ▁why ▁having ▁a ▁B TS ▁close ▁to ▁the ▁user ▁results ▁in ▁less ▁expos ure ▁to ▁elect romagnet ic ▁radiation . ▁▁ ▁to ▁have ▁a ▁B TS ▁close ▁to ▁them ▁as ▁their ▁MS ▁will ▁be ▁power ed ▁down ▁as ▁much ▁as ▁possible . ▁For ▁example , ▁there ▁is ▁more ▁power ▁being ▁transm itted ▁from ▁the ▁MS ▁than ▁what ▁one ▁would ▁receive ▁from ▁the ▁B TS ▁even ▁if ▁they ▁were ▁ 6 ▁meters ▁away ▁from ▁a ▁B TS ▁m ast . ▁However , ▁this ▁estimation