What is Massive MIMO: A Brief description of the Technologies, Advantages and the Challenges Ahead

What is Massive MIMO? An overview of the latest technological research, innovation, and the advantages and the challenges associated with it.

Transformative new technologies causing disrupting innovation and inducing revolutionizing changes are frequent now than ever before. With the 5G, the new wireless connectivity wave the Massive MIMO, its implication to the new connectivity and the threat landscape that is inherited by the system and emerging security issues that it will bring in the future, must be examined well before springing into the action of implementing the technology extensively. Achieving the of the dream of a hyper-connected world with the gigantic numbers of interconnected devices interacting with the human with super-fast wireless connectivity, as proclaimed by the 5G implementation largely depends on this technology. Only Massive MIMO is capable of facilitating this kind of enormous future need with its enhanced data rates and remarkable spectral and energy efficiency. The smart cars, cities, remote controlling of grids and other critical services, such large scale implementation demands a highly reliable system. Massive MIMO has shown an incredible promise in resolving the current issues with the wireless network reliability, preventing the full realization of the 5G network.

MIMO stands for Multiple Inputs and Multiple Outputs where the signals are propagated through the multiple paths to increase the capacity transmitted and received both by more than one antennas over the same radio channel. The result is a glorious increase in data rates and reliability. MIMO uses many technologies. Using multiplexing it increases wireless bandwidth and the range considerably by cutting down interference, sending the radio signals in additional pathways. There is multi-user MIMO or MU MIMO, which includes multiple accesses with multiple users.

Now the Massive MIMO raise both the magnitude of the benefits and effectiveness increasing the numbers of antennas involved in the signal transfer. In massive MIMO Base Stations (BS) are composed of an array of antennas serving a number of terminals simultaneously providing an increased throughput. The ‘Massive’ does not indicates the size but numbers of the antennas used in the MIMO. Though there is no exact number or the range specified generally at least 16 antennas are believed to be needed at the transmitting and receiving ends to consider it as a Massive MIMO.

Nokia’s AirScale Massive MIMO has adopted a system with 128 antennas broadcasting 64 transmit and 64 receive streams with 16 layers Massive MIMO along with carrier aggregation and 3D Beamforming promising 8 times faster downlink and 5 times more speed in case of uplink facilities. Not only lower the network latency but with the ReefShark chipset, Nokia claimed is reducing the sizes of the antennas to half and the power consumption will be lessened too. Award-winning Ericsson’s AIR 6468 has 64 transmit and 64 receive antennas making it able to support 5G plugins for both the Massive MIMO and the MU MIMO.

Massive MIMO incorporated several technologies. IT increases the spectral efficiency by the special multiplexing without compromising its robustness. Another technology space-time coding improves data reliability by exploiting the multiple streams of data received through different channels. Beamforming and channel diversity help to attain a higher throughput reducing the inter cell as well as intra-cell interferences provisioning a better data transfer within the small cells. The targeted use of the spectrum with Beamforming will lead to better services even in the densely populated areas and the best part is it does not need additional spectrum to increase the wireless connectivity.

It provides a higher data rate, improves the signal to noise ratio, and a better channel hardening opportunities. More robust against the passive and active attacks like eavesdropping and jamming, Massive MIMO offers wireless network connectivity with reduced latency coupled with reduced energy consumption. Creating a win-win situation, the benefits that have transformed this technology into such a promising candidate to support the 5G connectivity within a decade from being a mere research idea confined in the labs of a few academics. The Massive MIMO also claimed to simplify the media access control (MAC) layer.

Though Massive MIMO has been developed keeping sub-6 GHz frequency bands on the mind it also works well in the 30–300 GHz range known as millimeter wave (mmWave). While TDD operation suits well at sub-6 GHz Massive MIMO, FDD is equally effective in mmWave as the angular information describing the channel path is reciprocal over the wide bandwidths. The rich scattering environment enables this technology to offer better connectivity by supporting parallel data streams in indoor or densely populated urban settings.

By far the few tests and field trials that have been done looks promising but believed to be the chief enabler of the 5G networks in future the security concerns over the vulnerabilities like pilot contamination and engineering, hardware, deployment, and several other challenges must be addressed well before the wider adoption of this technology takes into place. The recent research has suggested applying limited training sequences by adopting the simple pilot assignment and channel estimation method to alleviate the pilot contamination. The timeshifted (asynchronous) protocol based method, distributed single-cell precoding method, non-overlapping AOA- based method and Blind Methods exploiting subspace partitioning are the few other leading techniques that have been recently proposed by different researches to mitigate the pilot contamination in Massive MIMO environment.

As summarized by an article other challenges according to the Institute of Electrical and Electronics Engineers (IEEE) includes:

  • Engineering many low-cost low-precision components that will work effectively together,
  • Perfect acquisition and synchronization for newly joined terminals,
  • The exploitation of extra degrees of freedom provided by the excess of service antennas,
  • Searching for new deployment scenarios,
  • Reducing internal power consumption to achieve total energy efficiency reductions,

Multiple industry leaders and independent researchers are investigating the issues related to massive MIMO deployment and searching for more effective ways handling the complexities associated with it. But the bottom line is with the 5G hovering in the horizon, bringing the much anticipated revolutionary changes and the Massive MIMO being one of the key technologies behind it, the technology must be understood and examined carefully to gauge its real implication and capitalize the full potential to determine how it will alter the course of the future for your business and life.

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