A MAJOR ISSUE IN 4G SYSTEMS IS TO MAKE THE HIGH BIT RATES AVAILABLE IN A LARGER PORTION OF THE CELL, ESPECIALLY TO USERS IN AN EXPOSED POSITION IN BETWEEN SEVERAL BASE STATIONS. IN CURRENT RESEARCH, THIS ISSUE IS ADDRESSED BY MACRO-DIVERSITY TECHNIQUES, ALSO KNOWN AS GROUP COOPERATIVE RELAY, AND ALSO BY BEAM-DIVISION MULTIPLE ACCESS (BDMA).
4G CELLS INTERLINKED BETWEEN CELLS INTERLINKED BETWEEN BASE STATIONS INTERLINKED BY GROUP CO-OP RELAY.














