MIMO And Array Design For 5G

Source: Remcom
Four possible beams for a 28 GHz array

Antenna engineers favor advanced antenna systems capable of beam steering and multiple data stream transmission in order to meet 5G throughput requirements.  Designing such a device is a difficult task because many factors are involved a device’s performance:

  • Antenna coupling within a device’s case
  • Effects of multipath propagation
  • Data transfer schemes

XFdtd and Wireless InSite ensure a comprehensive device design process, from simulating the initial antenna pattern to computing throughput performance in a multipath channel model. Together the products ensure a device will work well in its intended environment.

Standalone Device Performance

Laptop with a four element MIMO antenna
Remcom’s time-domain electromagnetic simulation software, XFdtd, enables in-depth analysis of a device’s stand alone performance.  Detailed CAD models of the antennas, PCB, and device assembly are imported from Pro Engineer, Allegro, and other software packages.  The following results are available from a single finite-difference time-domain (FDTD) simulation:

  • Antenna isolation
  • Envelope cross correlation
  • Antenna efficiency
  • Radiation patterns

An RF engineer needs to go beyond standalone antenna performance in order to ensure sufficient 5G device performance.  Results from an XFdtd simulation that characterize the performance of an antenna are easily exported to Wireless InSite where the device is analyzed in its intended environment.

3D Channel Model

Office layout with access point (AP) and single laptop location
3D propagation scenarios can be modeled in Remcom’s wireless prediction software, Wireless InSite.  Site-specific and generic test environments are created by importing terrain, defining building floor plans, specifying base station or access point locations, and providing material information.  Antenna designs from XFdtd are then tested in applications including:

  • City blocks for small cell base station deployment
  • Outdoor-to-indoor for fixed wireless access scenarios
  • Office buildings for WiFi access planning

Location of AP in corner of office
Wireless InSite uses high-fidelity ray-tracing models to determine multipath propagation through the 3D environment.  These industry leading capabilities include the ability to analyze:

  • 3D terrain, buildings, and floor plans
  • Fine structural details including curbs, window frames, chairs, and desks
  • Diffuse scattering at millimeter waves
  • Attenuation from trees, shrubs, and other foliage

Propagation paths between AP and single laptop location
Transmitters and receivers are comprised of one or more antenna elements.  Wireless InSite computes the link between each antenna element on the transmitter and receiver and reports results including:

  • Complex impulse response at each receiver
  • Received power
  • Coverage maps
  • Power delay profiles
  • H-matrices connecting each antenna element on a base station or access point to those on a UE or device

Once the 3D propagation scenario has been characterized, communication systems can be overlayed to determine throughput and capacity metrics.

Communication System Metrics

Given the antenna design and 3D channel model, Wireless InSite’s Communication Systems Analyzer allows the RF engineer to evaluate a 5G device’s operation in the intended scenario.

Throughput coverage for all laptop locations
To start, a MIMO technique is applied to each transmitter and receiver.  This will improve a system’s performance by increasing the signal-to-interference-plus-noise ratio (SINR), providing multiple parallel data streams, or both.  Wireless InSite models the following MIMO techniques:

  • Antenna diversity
  • Spatial multiplexing
  • Beamforming

MIMO techniques determine how data is transmitted through the 3D environment.  Once that is known, Wireless InSite determines how much data can be transmitted.  The following metrics are accessed for each data stream and point-to-point link:

  • Throughput and capacity
  • Bit error rate (BER)
  • Noise, interference, and SINR

This results in a powerful tool that engineers use to determine if their device will meet 5G performance requirements in a realistic operating environment.

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