5G wireless technologies are predicted to provide groundbreaking accessibility for wireless network users globally. But with this lofty goal, comes many practical challenges. For instance, network providers are seeing an increased need for small cells to be installed in close proximity in urban environments to provide coverage to small and densely trafficked areas, especially those with high-throughput demands. With the help of three types of Multi-Input Multi-Output (MIMO) architectures, system engineers are striving to overcome these challenges.
Smalls Cells are reduced size, range, and infrastructure base stations, that are the first evolutionary step toward extremely dense populated wireless service stations. There are two main types of Small Cells; Hardwired Small Cells and Mesh Network Small Cells.
Hardwired Small Cells are backhauled networks with fiber or copper connections to an established infrastructure. They offer fast connection and limited to zero interference, but are costly and take a long time to deploy. Mesh Network Small Cells offer access points that are lower cost and easily deployed, but are limited in range and are plagued by interference and latency issues. Hence, enhancements of this architecture with lower-cost and lower latency infrastructures are needed to bridge the gap between large area and low throughput macrocells and targeted, high-throughput small cells.
The advancement of millimeter-wave and massive MIMO solutions in response to upcoming 5G expectations, suggests that the development of future small cell networks will include more advanced technologies and a heterogeneous network approach.
Since there is a limitation of bandwidth in sub-6 GHz frequencies, providers are extending the communication spectrum into millimeter-wave technologies to provide a high level of throughput over short ranges. The disadvantages of leveraging frequencies beyond 6 GHz however, is increased atmospheric attenuation, leading to shorter operating range and limited availability of cost-effective hardware solutions. There is also the extremely complex task of engineering wireless routing and handovers with the multiplicity of nodes and paths. Still, millimeter-wave technology does have the ability to provide higher data rates with low power consumption, higher quality connections with lower latency, as well as providing coverage in areas where traditional small cells or macrocells won’t provide the needed throughput or spatial accuracy. Major network providers have already started investigating massive installation of millimeter-wave MIMO-based microcells in preparing to lay the foundation for a 5G infrastructure.
Massive multiple-input multiple-output (MIMO) allows for a large increase in spectral efficiency, or more concurrent transmissions in smaller bandwidths — a major requirement of 5G. Massive MIMO access points are equipped with hundreds of antennas, and can provide an almost one-hundred-fold increase in efficiency without the need for separate base stations distributed throughout a high trafficked area.
Currently, multi-user MIMO (MU-MIMO) is being leveraged, which transmits multiple data streams to multiple devices, as opposed to single-user MIMO that directs multiple antennas streams to a single device. MU-MIMO has the benefits of simple implementation with linear processing techniques and can eliminate the effects of uncorrelated noise and small-scale fading. The number of interconnects, antennas, RF, and signal processing hardware increases considerably with the complexity of a massive MIMO system, however, possibly prohibiting its use in some areas where the costs and infrastructure aren’t justified.
Where are we heading?
It's clear today no MIMO network architecture is one-size-fits all, so 5G technology services are likely to end up relying on a blend of diverse network architectures, each leveraging their distinct advantages.
To learn even more about 5G MIMO Networks, download our tech brief "Insights on Evolving 5G MIMO Networks and Test Methods"
To learn more definitions surrounding the MIMO conversation read our blog on defining the key terms surrounding linear processing and precoding.