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Genarating the Wireless Channel for Indoor Open Office Terrain

The channel models has been designed to support the following features:

Parameters	Values
Antenna Array	[\(\text{M}_g, \text{N}_g, \text{M}, \text{N}, \text{P}\)]
UE Antenna Array	[1,1,2,2,1]
UE Antenna	Omni
BS Antenna Array	[1,1,4,4,1]
BS Antenna	Parabolic
Carrier Frequency	\(3 \times 10^9\)
Simulation Layout	Rectangular
Subcarrier Spacing	30 kHz
fftsize	512
Terrain	Indoor-Factory (InF-SL)
Mobility	Disabled
Inter-site Distance	20
Number of Sectors Site	3
UE Height	Uniform\((0,1)\) m
UE Drop	Random
UE Height Distribution	Random
BS Height	3m
Ceiling Height	6m
clutter Height	4m
clutter Size	3m
clutter Density	0.4

In this Tutorial, we will generate the Multicell MIMO channel between multiple users and multiple base-stations for Indoor Factory Terrain. THe content of the tutorial is listed below:

Table of Contents

• Import Libraries

  • Python Libraries

  • 5G Toolkit Libraries

• Simulation Parameters

• Generate Antenna Arrays

• Node Mobility/Route

• Generate Simulation Topology

• Generate Channel(LSP/SSPs) Parameters

• Generate Channel Coefficients

• Generate OFDM Channel Generation

  • Frequency Domain: Magnitude Response Plot

  • Time Domain Channel Response

Import Libraries

Import Python Libraries

import os
os.environ["CUDA_VISIBLE_DEVICES"] = "-1"
os.environ['TF_CPP_MIN_LOG_LEVEL'] = '3'

# %matplotlib widget
import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy      as np

Import 5G Toolkit Libraries

import sys
sys.path.append("../../../")

from toolkit5G.ChannelModels import NodeMobility
from toolkit5G.ChannelModels import AntennaArrays
from toolkit5G.ChannelModels import SimulationLayout
from toolkit5G.ChannelModels import ParameterGenerator
from toolkit5G.ChannelModels import ChannelGenerator

Simulation Parameters

The simulation parameters are defined as follows * propTerrain defines propagation scenario or terrain for BS-UE links * carrierFrequency defines carrier frequency in Hz * nBSs defines number of Base Stations (BSs) * nUEs defines number of User Equipments (UEs) * nSnapShots defines number of SnapShots

# Simulation Parameters
propTerrain      = "InH-OO"      # Propagation Scenario or Terrain for BS-UE links
carrierFrequency = 3.6*10**9                   # carrier frequency in Hz
BSgeometry       = np.array([6,2])           # number of BSs along rows and columns
nBSs             = np.product(BSgeometry)    # number of BSs
nUEs             = 50                        # number of UEs
nSnapShots       = 1                         # number of SnapShots

Generate Antenna Arrays

The following steps describe the procedure to simulate AntennaArrays Objects at a single carrier frequency both at Tx and Rx side:

# Antenna Array at UE side
# assuming antenna element type to be "OMNI"
# with 2 panel and 2 single polarized antenna element per panel.

ueAntArray = AntennaArrays(antennaType     = "OMNI",
                           centerFrequency = carrierFrequency,
                           arrayStructure  = np.array([1,1,2,2,1]))
ueAntArray()
# Radiation Pattern of Rx antenna element
fig, ax = ueAntArray.displayAntennaRadiationPattern()

# Antenna Array at BS side
# assuming antenna element type to be "3GPP_38.901", a parabolic antenna
# with 4 panel and 4 single polarized antenna element per panel.


bsAntArray = AntennaArrays(antennaType     = "3GPP_38.901",
                           centerFrequency = carrierFrequency,
                           arrayStructure  = np.array([1,1,4,4,1]))
bsAntArray()
# Radiation Pattern of Tx antenna element
fig, ax = bsAntArray.displayAntennaRadiationPattern()

Generate Simulation Layout

We define the simulation topology parametes:

• ISD: Inter Site Distance

• minDist: Minimum distance between transmitter and receiver.

• bsHt: BS heights

• ueHt: UE heights

• topology: Simulation Topology

• nSectorsPerSite: Number of Sectors Per Site

Furthermore, users can access and update following parameters as per their requirements for channel using the handle simLayoutObj.x where x is:

• The following parameters can be accessed or updated immendiately after object creation

  • UEtracks

  • UELocations

  • ueOrientation

  • UEvelocityVector

  • BStracks

  • BSLocations

  • bsOrientation

  • BSvelocityVector

• The following parameters can be accessed or updated after calling the object

  • linkStateVec

# Layout Parameters
isd                  = 20         # inter site distance in meters
minDist              = 0          # min distance between each UE and BS in meters
ueHt                 = 1          # UE height in meters
ceilingHt            = 6          # height of ceiling in meters
clutterHt            = 4          # height of clutter for indoor factory scenario
clutterSize          = 3         # size of clutter for indoor factory scenario
clutterDen           = 0.4        # density of clutter for indoor factory scenario
bsHt                 = 3   # BS height in meters
bslayoutType         = "Rectangular" # BS layout type
ueDropType           = "Rectangular" # UE drop type
nSectorsPerSite      = 1             # number of sectors per site
indoorUEfract        = 1             # Fraction of UEs located indoor
htDist               = "random"      # UE height distribution
ueDist               = "random"      # UE Distribution per site
lengthOfIndoorObject = 3             # length of indoor object typically having rectangular geometry
widthOfIndoorObject  = 3             # width of indoor object


simLayoutObj = SimulationLayout(numOfBS = BSgeometry,
                                numOfUE = nUEs,
                                heightOfBS = bsHt,
                                heightOfUE = ueHt,
                                ISD = isd,
                                layoutType = bslayoutType,
                                ueDropMethod = ueDropType,
                                UEdistibution = ueDist,
                                UEheightDistribution = htDist,
                                numOfSectorsPerSite = nSectorsPerSite,
                                minUEBSDistance = minDist)
simLayoutObj(terrain = propTerrain,
             carrierFreq = carrierFrequency,
             ueAntennaArray = ueAntArray,
             bsAntennaArray = bsAntArray,
             indoorUEfraction = indoorUEfract,
             heightOfRoom = ceilingHt,
             clutterHeight = clutterHt,
             clutterSize = clutterSize,
             clutterDensity = clutterDen)
# displaying the topology of simulation layout
fig, ax = simLayoutObj.display2DTopology(refBS=0)
ax.set_xlabel("x-coordinates (m)")
ax.set_ylabel("y-coordinates (m)")
ax.set_title("Simulation Topology")
ax.legend()

<matplotlib.legend.Legend at 0x7f73c2c5ea10>

Generate Channel Parameters

• This subsection provides the steps to obtain all the cluster level channel parameters, which includes both Large Scale Parameters (LSPs) and Small Scale Parameters (SSPs).

• LSPs includes Path Loss (PL), Delay Spread (DS) and Angular Spreads both in Azimuth and Zenith directions, and cluster powers (Pn) comes under SSPs.

• LSPs/SSPs: paramGenObj.x where x is

  • linkStateVec

  • delaySpread

  • phiAoA_LoS, phiAoA_mn, phiAoA_spread

  • thetaAoA_LoS, thetaAoA_mn, thetaAoA_spread

  • phiAoD_LoS, phiAoD_mn, phiAoD_spread

  • thetaAoD_LoS, thetaAoD_mn, thetaAoD_spread

  • xpr

  • pathloss, pathDelay, pathPower

  • shadowFading

# channel parameters
paramGenObj = simLayoutObj.getParameterGenerator()

Generate Channel Coefficients

Cluster level channel coefficients can be simulated using the following code snippet.

• channel.coefficients with shape: (number of carrier frequencies, number of snapshots, number of BSs, number of UEs, numCluster/numPaths, number of Rx antennas, number of Tx antennas)

• channel.delays with shape: (number of carrier frequencies, number of snapshots, number of BSs, number of UEs, numCluster/numPaths)

channel = paramGenObj.getChannel(applyPathLoss = True)
channel.coefficients.shape

(1, 1, 12, 50, 23, 4, 16)

Generate OFDM Channel

• Shape of OFDM Channel:

  • Hf is of shape : (number of carrier frequencies, number of snapshots, number of BSs, number of UEs, fftsize, number of Rx antennas, number of Tx antennas)

fftsize = 1024
Hf = channel.ofdm(30*10**3, fftsize, simLayoutObj.carrierFrequency)
Hf.shape

(1, 1, 12, 50, 1024, 4, 16)

Frequency Domain : Magnitude Response Plot

• The frequency domain magnitude plots (frequency responses) helps demonstate the order of frequency selectivity

  • Frequency selectivity is low for LOS Channel

  • frequency selectivity is high for NLOS Channels

• Wireless channel at high frequency

  • has higher path-loss

  • less frequency selective (due to lower delay spread and weak distance paths)

scaleFig = 1
fig, ax = plt.subplots(1, 2, figsize=(17.5/scaleFig,7.5/scaleFig))

i = 0
ax[0].plot(np.arange(-channel.fftSize/2, channel.fftSize/2)*channel.subCarrierSpacing + channel.fc[0],
           np.abs(Hf[0,0,0,i,:,0,0]), "g", label = "$f_c$="+str(channel.fc[0]/10**9)+" GHz")


ax[0].legend()
ax[0].set_xlabel("Frequency (Hz)")
ax[0].set_ylabel("Magnitude Response")
ax[0].set_title("Channel Magnitude Response")
ax[0].grid()

ax[1].plot(np.arange(-channel.fftSize/2, channel.fftSize/2)*channel.subCarrierSpacing + channel.fc[0],
           np.angle(Hf[0,0,0,i,:,0,0]), "g", label = "$f_c$="+str(channel.fc[0]/10**9)+" GHz")


ax[1].legend()
ax[1].set_xlabel("Frequency (Hz)")
ax[1].set_ylabel("Phase Response")
ax[1].grid()
ax[1].set_title("Channel Phase Response")

fig.suptitle("Channel Frequency Response: Phase and Magnitude")

plt.show()

Time Domain Channel response

• Practical wireless channel are bandlimited which results in:

  • impulses widening:

    • higher for lower frequency channels

  • time spread

These effects can be observed in following plots.

ht = np.fft.ifft(Hf, fftsize, axis = -3, norm = "ortho")

scaleFig = 2
fig, ax = plt.subplots(figsize=(17.5/scaleFig,7.5/scaleFig))
i = 0
ax.stem(channel.delays[0,0,0,i], np.abs(channel.coefficients[0,0,0,i,:,0,0]), "r", label = "Ideal Channel")
ax.stem(np.arange(channel.fftSize)/(channel.fftSize*channel.subCarrierSpacing), np.abs(ht[0,0,0,i,:,0,0]), "g", label = "Practical Channel")
ax.legend()
ax.set_xlim([0, 0.2*10**-5])
ax.set_xlabel("delays (s)")
ax.set_ylabel("Power")
ax.grid()


fig.suptitle("Power Delay Profile for the Different Carrier Frequencies")
plt.show()