LTE Emulator

TUCN – Data Transmission Laboratory
The second group of parameters is also considered in the emulation process, i.e. the ones
referring to the cell dimension (the cell is assumed circular, with a given radius), type of cell
(urban/rural, small/large), the noise and/or interference distribution, mobile speed and its motion
law and characteristics of the base station transceiver (carrier frequency, transmission power,
height of the antenna). The value of the SNR0 is computed by using these parameters and tables
with bit error and delay distributions are selected, according to the SNR0 value, out of a group of
tables corresponding to the carrier frequency, multipath propagation profile and the cell carrier
load.
The speed of the user can be set both in the simulation and emulation processes. The two
speeds do not have to be equal, if the synchronization/equalization operations are considered to
be ideal, because the speed does not affect the probability density functions, if the simulation is
performed within a sufficiently large time interval. Therefore, different values of the mobile’s
speed do not require tables with different statistics. The velocity of the user is used in the
simulation process, as well as in the emulation one, for computing the coherence time of the
channel [Rap01] [Skl97], which has to be greater than the TTI interval. The channel
characteristics are considered constant within the coherence time interval and, during this
interval, only a single value is employed both for the instantaneous rate (number of bits/TTI) and
the number of errors/TTI (the error distribution can vary within the data packet).
3.1. Functional blocks of the emulator. Parameters of the functional blocks
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3.1.1. The signal to noise ratio computation block
This block has the purpose of reading the parameters of the cell (the geometry of the cell), of
the base station transceiver and of the user’s mobility and to compute the value of the SNR0.
Meanwhile the block provides the display of the main user’s trajectory within the cell. The
parameters that are processed by this block, divided into 4 groups, are the following (see also fig.
3.2.):
o cell radius (circular cell) expressed in km;
o cell dimension: small cell (radius ≤1km) and large cell (radius > 1km);
o cell type: urban, suburban, rural;
Note: the last two parameters select the formulae used for the computation of the
attenuation, referred to the base station (center of the cell), i.e. the formulae that are
used to compute the large scale fading, which depends on the cell-type.
o channel carrier frequency, expressed in MHz;
o transmission power of the base station, expressed in dBm;
o noise power expressed in dBm;
Note: in this emulator version, the noise spectral power density is considered
constant in the entire cell.
o height of the antenna of the base station transceiver, expressed in m.
Note: height of the user’s antenna is considered constant and equal to 1.5m;
o speed of the user, expressed in km/h;
Note: the speed of the mobile must be chosen such that the coherence time of the
mobile radio channel is greater or equal to the duration of the transport frame. The
computation of the coherence time is made according to relation (2). In the present
version, the emulator does not check the fulfillment of this condition; this task is to
be accomplished by the user, when setting the emulation parameters.
o the mobile’s motion law. It involves the function that describes the position of the
mobile in time, within the cell, as a function of the cell’s dimension and the mobile