Yesterday I read an interesting article on Massive MIMO. The next generation network beyond 4G could be built with big arrays of tiny antennas, according to Bell Labs scientist Tom Marzetta.

“It’s MIMO to the extreme,” Marzetta said to eWEEK Europe at an open day run by Bell Labs in France.

Before going further lets have a look at MIMO first.

Systems with multiple antennas at the transmitter and receiver – also referred to as Multiple Input Multiple Output (MIMO) systems – offer superior data rates, range and reliability without requiring additional bandwidth or transmit power. By using several antennas at both the transmitter and receiver, MIMO systems create multiple independent channels for sending multiple data streams.

In 3GPP LTE Release 8, Transmission with multiple input and multiple output antennas (MIMO) are supported with configurations in the downlink with two or four transmit antennas and two or four receive antennas, which allow for multi-layer transmissions with up to four streams. Multi-user MIMO i.e. allocation of different streams to different users is supported in both UL and DL. LTE supports 1x2,2x2,4x2,4x4

The peak data rates tend to be proportional to the number of send and receive antennas, so 4X4 MIMO is capable of twice the peak data rates as 2X2 MIMO systems. 

Getting back to Massive MIMO, Marzetta’s idea, tentatively called “large scale MIMO” or “Masive MIMO” uses even more antennas on the base station but “shares” the throughput gains between many terminals.

Using 20MNHz of spectrum, a Massive MIMO base station could have a throughput of 1200Mbps per cell, compared with 74Mbps per cell with LTE, said Marzetta. Each Massive MIMO unit would deliver 60bps per Hz of frequency

Dr Marzetta is hoping to get support from other vendors and operators, and has presented the idea of Massive MIMO in a paper "Beyond LTE: Hundredsof Base Station Antennas!", a slide from same presentation is shown below.