Page 54 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum

ITU Journal: ICT Discoveries, Vol. 2(1), December 2019

lowed by the simulation results in section 6. In section 7 proposed model, the clustered DOA features are extracted
and 8, we present a guideline for the model implementa- independently from the delay or other channel parame-
tion and model veri ication, and we conclude the paper in ters. Therefore, our model is in a relatively compact form
section 9. and focuses on the azimuth DOA domain.

2. LITERATURE REVIEW 3. SYSTEM MODEL
In the existing literature, standard models draw great at- In this section, we present the transmitter and the re-
tention since they are regulated and agreed on by organi- ceiver system model considering only one base station
zations across the world [8, 9, 10]. Among all the standard (BS), and multiple mobile stations (MS). Additionally, we
models, cooperation in science and technology (COST) illustrate the virtual city models used in the RTS.
models are widely accepted. The different COST channel
models e.g. COST 207, COST231, COST 259, COST 273 and 3.1 Transmitter and receiver system model
COST 2100 were developed to address speci ic objectives
in various application ields [8, 9, 10, 11, 12]. A basic system layout model is shown in Fig. 1. We con-
sider an omnidirectional transmitter as the BS, located at
COST 259 has a three-layered framework structure, spec- L BS = [x , y ] and MS randomly and uniformly placed

ifying 13 radio propagation environments considered in within the area, located at ixed positions L MS = [x , y ],

the analysis of performance in wireless systems [8, 13]. It = 1, ..., . The height of the BS is ℎ , and all the MS
BS
clusters MPCs in the delay domain and models the chan- have an identical height of ℎ . Such a system layout is
MS
nel by distance-dependent path loss, shadowing fading, able to capture the propagation features from 360° at var-
and power-delay-angular-pro ile. Adopting the hierarchy ious distances. We also propose a local coordinate system
of modeling concepts similar to COST 259, the COST 273 for each MS in section 4, and the electromagnetic proper-
model provides two signi icant achievements: 1) New ties of the simulated BS and MS can be found in section
scenarios for multiple-input multiple-output (MIMO) are 6.
de ined; and 2) the clusters are considered differently i.e.,
apart from local clusters and single clusters, twin clusters
are introduced to simulate multiple-bounce interactions
[9]. Moreover, the COST 2100 model extended the COST
273 model by the novel developments of the polarization
of the channel, dense multipath components and multi-
link aspects [10].
Apart from the aforementioned standard models, some
other directional models widely adopted by researchers
include analytical models, stochastic models and ray trac-
ing models [14]. Analytical models mathematically de-
scribe the channel without considering the speci ic geog-
raphy of the environment, such as the independent and
identically distributed (i.i.d.) model [15] and the Kro-
necker model [16]. Stochastic models characterize the
radio propagation between transmitters and receivers
by using stochastic scatterings [3, 17]. Most of them
Fig. 1 – System model. The station at the center in red is the base station,
are geometry-based models but are not limited to a spe- and the devices in blue are the mobile stations.
ci ic site. The COST models mentioned above are also
stochastic models. The last classi ication, ray tracing
models, highly depend on the radio propagation environ- 3.2 Virtual urban scenario
ment with a limited range of validity. However, ray trac-
ing models can extract the propagation parameters (path Different types of environments have a signi icant impact
loss, DOD, DOA, and so forth) accurately [18, 19]. on the channel model. For the typical urban scenario we
are interested in, it has dense buildings with a relatively
Although there are plenty of directional channel mod- small number of large open areas like lakes and parks. Al-
els characterizing the propagation from various perspec- though there is some afforestation in the urban environ-
tives, some papers focused on the delay or delay-DOA ment, it is out of proportion with buildings. Apart from
domain [3, 8, 9], while some papers considered a non- these aforementioned urban features associated with the
clustering DOA domain [20, 21]. However, the number of building layout, another key factor taken into considera-
papers focusing on the azimuth DOA clusters and the clus- tion is the materials of the buildings. The reason is that
ter power pro ile are limited. By contrast, our paper cap- the materials affect the electrical conductivity and resis-
tures the features of the azimuth DOA in clusters. In our tivity, leading to a signi icant impact on the electromag-

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