Indoor LTE Using MIMO

Perform network planning for long term evolution (LTE) using multiple input multiple output (MIMO) in an indoor scenario.

Model Type

This is an example of an indoor scenario that uses multiple input multiple output technology. The project is a network planning project based on a .wst file for the air interface.

Sites and Antennas

Two antennas are located close to each other at a height of 3.5 m inside the building. Both antennas have an omnidirectional radiation pattern and use the same carrier frequency of 2120 MHz. In this model, the antennas are configured to use MIMO technology. MIMO streams 1 and 2 are assigned to antennas 1 and 2, respectively.
Tip: Click Project > Edit Project Parameter and click the Sites tab to view the sites and antennas.

Air Interface

The LTE air interface is defined in this model with the file, LTE_Sample_Indoor_MIMO_Compact.wst. The modulation scheme, OFDM/SOFDMA (orthogonal frequency-division multiplexing) is selected for multiple access. The duplex separation between uplink and downlink is 190 MHz and is achieved by using frequency division duplex (FDD).
Tip: Click Project > Edit Project Parameter and click the Air Interface tab to view the air interface and MIMO settings.

Overhead and interference associated with having two MIMO streams on the same carrier are specified on the Air Interface tab. In addition, all available carriers and transmission modes are listed on the Air Interface tab.

Computational Method

The computational method used for this model is the dominant path model (DPM). The DPM focuses on the most relevant path, which leads to shorter computation times compared to standard ray tracing model (SRT). In addition, the DPM can include ray paths with more diffractions compared to SRT. For this building, both methods could be used, but for larger buildings, the DPM is usually preferred.
Tip: Click Project > Edit Project Parameter and click the Computation tab to change the model.

Empirical losses are calculated along the propagation path for which material properties are required. Material properties are easier to obtain compared to physical parameters. In addition, the parameters of the empirical model can readily be calibrated with measurements. Therefore it is easier to achieve high accuracy with the empirical model.

Results

Propagation results show, at every location, the power received from the transmitting antenna.

The type of network simulation is a static simulation (homogeneous traffic per cell). The network simulation calculates the following:
  • signal area
  • cell area
  • site area
  • best server
  • maximum data rate
  • maximum throughput
  • MIMO streams for uplink and downlink
For all modulation and coding schemes used in this model, the network simulation calculates the following:
  • minimum required transmitter power
  • maximum receiver power
  • SNIR
  • reception probability
  • maximum number of parallel streams at a pixel
  • throughput at a pixel in transmission mode for uplink and downlink
Figure 1. Propagation results: power of Site 0, Antenna 2.


The power level in the area on the left (Figure 1) is very low. This low power level results in white pixels in the network analysis results since the power level is too low in that specific location for communication with the modulation and coding schemes of this air interface.

The line-of-sight conditions can be viewed by selecting LOS in the result tree.
Figure 2. LOS (line-of-sight) results: Site 0, Antenna 2.


The following line-of-sight conditions are displayed:
  1. Line-of-sight (LOS) condition: a direct line of sight between transmitter and receiver, represented by the green color in Figure 2.
  2. Obstructed-line-of-sight (OLOS) condition: the transmitter and receiver do not have walls between them (the transmitter and the receiver are in the same corridor but without having a direct line of sight - only for indoor scenarios), represented by the red color in Figure 2.
  3. No-line-of-sight (NLOS) condition: the rays from transmitter to receiver have to pass through a wall. This is represented by the blue color in Figure 2.

In most locations the signal strength is high while interference is low, leading to reception of both MIMO streams, see Figure 3. This enables communication at almost twice the rate of a single stream. The maximum data rate is shown in Figure 4.

Figure 3. The number of MIMO streams received in the downlink.


Figure 4. The maximum data rate in the downlink.