5G Massive MIMO & Beam-forming

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MIMO is one of the key enabling techniques for 5G wireless technology, providing increases in throughput and signal to noise ratio.

MIMO - Multiple Input Multiple Output is well established for mobile communications as well as many other technologies. It is used in Wi-Fi 802.11 and is a central part of 4G LTE as well as many other radio communications technologies.

As a result of the demand, base stations are being installed with 5G massive MIMO antennas and user equipments are also able to accommodate MIMO operation to enhance the overall performance.

Using MIMO antennas and beam-forming techniques, 5G wireless technology is able to offer increased capacity and data speed.

What is MIMO

MIMO is an antenna technology that improves the radio link by using the multiple paths over which signals travel from the transmitter to the receiver, primarily as a result of the many reflections that the signal undergoes and the many paths over which it can travel.

The multiple paths are de-correlated and this provides the opportunity to send multiple data streams over them.

5G MIMO & massive MIMO

The 4G LTE specification allows the use of up to eight spatial layers in the downlink and four spatial layers in the uplink. In reality the deployed 4G LTE networks may use two or four spatial layers to enhance performance.

To develop from the basic MIMO used in 4G LTE to the 5G massive MIMO formats, it is possible to increase the number of antenna elements. For example using 64 cross polarised antennas means that the base station can be defined as a massive MIMO system.

Surprisingly the the significant increase in the number of antenna elements does not increase the number of spatial layers.

Using this large number of elements enables the 5G MIMO antenna to provide MIMO and beam-forming capabilities.

There is actually no definition of where the line is drawn between an ordinary MIMO system and a massive MIMO one. Typically it tends to be applied to systems with a number of tens of antennas or more. 5G massive MIMO antennas with 64, 96 and even 128 antenna systems are available.

Challenges and advantages of 5G massive MIMO

The use of massive MIMO within 5G wireless technology brings many advantages, and indeed it overcomes many of the issues that were present with 4G LTE MIMO approaches. However it brings many new challenges.

The development of the antennas is a key issue. It necessary to develop low cost low precision antennas.

Also it is necessary to be able to undertake meaningful testing. With MIMO and in this instance, massive MIMO having so many permutations and different conditions, it becomes very difficult to test. 5G massive MIMO antennas present many interesting challenges.

Looking at the advantages of 5G massive MIMO, there are significant advantages in terms of the capacity increases. Some estimates have put the improvement at 50 fold, although this could be a little exaggerated.

Previous generations of mobile communications systems have not had the capability to resource manage in the way that 5G is able and this has resulted in networks becoming over loaded. Using massive MIMO and beam-forming technology, the spectrum management is handled much more intelligently and this results in the data rates and latency levels being considerably more uniform across the network.

5G massive MIMO is a key element of the new mobile communications technology. It will enable significant increases in performance and data capacity - this last point being a major requirement for 5G as data usage is increasing significantly, and as a result the network capacity needs to increase. 5G massive MIMO capability will be part of providing the required capacity.

  Written by Ian Poole .
  Experienced electronics engineer and author.

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