▁the ▁glo be . ▁▁ ▁Communic ations ▁( wire less ) ▁Communic ation ▁can ▁be ▁defined ▁as ▁the ▁process ▁of ▁ex ch anging ▁of ▁information ▁between ▁two ▁or ▁more ▁parties . ▁The ▁last ▁two ▁dec ades ▁witness ed ▁a ▁rapid ▁growth ▁of ▁wireless ▁communication ▁systems . ▁This ▁success ▁is ▁a ▁result ▁of ▁adv ances ▁in ▁communication ▁theory ▁and ▁low ▁power ▁diss ip ation ▁design ▁process . ▁In ▁general , ▁communication ▁( tele communic ation ) ▁can ▁be ▁done ▁by ▁techn ological ▁means ▁through ▁either ▁elect rical ▁signals ▁( w ired ▁communication ) ▁or ▁elect romagnet ic ▁waves ▁( wire less ▁communication ). ▁An ten na ▁arrays ▁have ▁emer ged ▁as ▁a ▁support ▁technology ▁to ▁increase ▁the ▁usage ▁efficiency ▁of ▁spectral ▁and ▁enh ance ▁the ▁accuracy ▁of ▁wireless ▁communication ▁systems ▁by ▁util izing ▁spatial ▁dimension ▁in ▁addition ▁to ▁the ▁classical ▁time ▁and ▁frequency ▁dimensions . ▁Array ▁processing ▁and ▁estimation ▁techniques ▁have ▁been ▁used ▁in ▁wireless ▁communication . ▁During ▁the ▁last ▁de cade ▁these ▁techniques ▁were ▁re - expl ored ▁as ▁ideal ▁candidates ▁to ▁be ▁the ▁solution ▁for ▁numerous ▁problems ▁in ▁wireless ▁communication . ▁In ▁wireless ▁communication , ▁problems ▁that ▁affect ▁quality ▁and ▁performance ▁of ▁the ▁system ▁may ▁come ▁from ▁different ▁sources . ▁The ▁multi user ▁– medium ▁multiple ▁access - ▁and ▁multip ath ▁- signal ▁propag ation ▁over ▁multiple ▁scatter ing ▁paths ▁in ▁wireless ▁channels - ▁communication ▁model ▁is ▁one ▁of ▁the ▁most ▁w ides p read ▁communication ▁models ▁in ▁wireless ▁communication ▁( mobile ▁communication ). ▁▁ ▁In ▁the ▁case ▁of ▁multi user ▁communication