Many antennas[1] is a smart antenna technique which overcomes the performance limitation of single user multiple-input multiple-output (MIMO) techniques.
In cellular communication, the maximum number of considered antennas for downlink is 2 and 4 to support 3GPP Long Term Evolution (LTE) and IMT Advanced requirements, respectively.
Since the available spectrum band will probably be limited while the data rate requirement will continuously increase beyond IMT-A to support the mobile multimedia services, it is highly probable that the number of transmit antennas at the base station must be increased to 8–64 or more.
The installation of many antennas at single base stations introduced many challenges and required development of several high technologies: a new SDMA engine, a new beamforming algorithm and a new antenna array.
The table summarizes the recent history of multiple antenna techniques in cellular communications.