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Communications Systems Analysis

Wireless InSite’s Communications Systems Analyzer uses the results from ray-tracing channel modeling simulations and applies post-processing calculations to predict a number of different communications metrics.  These include SINR, throughput and capacity, bit error rate, and summary results that identify the best-performing base stations for each receiver point and provide the overall coverage from the system as a whole.  Users with a MIMO license can additionally select from a number of MIMO techniques that can be applied to enhance the channel or create multiple data streams prior to performing the communications analysis (see below). 

Setting up a Communications System for Analysis

In Wireless InSite, a Communication System is a collection of transmitters and receiver sets.  A transmitter represents a base station, while a receiver set can represent a field map grid, user equipment (UE) at individual points, or positions along a route.  The system can also include interferers, generally used to represent base stations from neighboring cells that are not part of the network being analyzed but that may impact its performance through adjacent cell interference.

Once a communications system is set up, a user can choose from three general types of analysis to assess its performance:

  • Throughput and Capacity

  • Bit Error Rate (BER)

  • Noise and Interference Analysis

For users with a MIMO license, there are additional calculations performed to apply MIMO techniques prior to beginning the communications analysis.

Interference and Noise Analysis

The first step in any analysis is to use channel data and noise specifications to determine signal power, interference, and noise.  Noise power is determined from noise power density, signal bandwidth, and each receiver’s noise figure and threshold.  Interference is determined using the received power from base stations within the system as well as any interferers (neighboring base stations outside the defined system).  From these inputs, the analyzer determines quantities such as the total noise and interference power at each receiver point in the study, the signal-to-noise-ratio (SNR), the signal-to-interference-plus-noise ratio (SINR), and a number of other related quantities.  Summary data is also collected, for example, determining the best SINR at each point and the base station from which that SINR was achieved.

Throughput

Wireless InSite can predict the throughput and capacity (theoretical maximum data rate) for a channel from the bandwidth and SINR.  It supports a number of different wireless access methods, including:

  • LTE

  • WiMax

  • 802.11n, ac

  • User-defined table

User-defined tables can be used to define other access methods or to customize the selection of modulation and coding scheme as a function of SINR (often a vendor-specific relationship).  

Wireless InSite throughput calculations for 3 different LTE bandwidths. Route through scene (red line) shows additional details of throughput reduction in areas where there are dropouts in coverage

Once the wireless access method is selected, the user chooses from allowed bandwidths for carriers, and the analyzer computes the throughput based on data from literature, specifications from communications standards, and the calculated SINR for each channel in the communications analysis.

Bit Error Rate

Wireless InSite offers three methods for bit error rate analysis: 

  • AWGN: assumes an additive white Gaussian noise (AWGN) channel

  • Theoretical Fading: assumes a Rayleigh or Rician fading channel

  • Semi-Analytic: determined based on an analysis of the complex impulse response of the channel

The bit error rate calculation is heavily dependent on the selection of the modulation and coding scheme (e.g., quadrature amplitude modulation, or QAM) and the alphabet size (e.g., 64).  It is also dependent on the SINR, the bandwidth, and for some of the methods, additional details about the channel characteristics, derived from the complex impulse response. 

Comparison of Bit Error Rate for 4-QAM (left) and 256-QAM (right) shows high BER in a larger proportion of the coverage area when higher-order modulation is used.

MIMO Beamforming, Spatial Multiplexing and Diversity

When a user has a MIMO license, a number of MIMO techniques are offered as options for any MIMO base station or UE that is present in the communications system.  For base stations in the system that have MIMO antennas, the user can choose one of following options:

  • Adaptive beamforming using MRT

  • Precoding table (supports beamforming or diversity techniques)

  • No beamforming/precoding

  • Spatial multiplexing using singular value decomposition (SVD)

For receivers (UEs) that have MIMO antennas, the user can choose from these options:

  • Selection combining (SC)

  • Equal gain combining (EGC)

  • Maximum ratio combining (MRC)

  • Spatial multiplexing using singular value decomposition (SVD)

Each of these options takes advantage of spatial diversity in the MIMO antennas at the transmitter and receiver for each point-to-point link and attempts to enhance the performance using the specified techniques at each end, or in the case of SVD, coordinating from both ends of the link.  The result will generally increase the SINR through beamforming or diversity, or it will provide multiple parallel data streams through spatial multiplexing.  Throughput and BER calculations will then be applied to each of the resultant data streams for each point-to-point link in order to determine the results.  See MIMO Beamforming, Multiplexing and Diversity in Wireless InSite for more information.