Optimization of LTE Network for Addis Ababa Light Railway
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Date
2019-10
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Addis Ababa University
Abstract
To meet railway communication demand, conventional railway mobile communication systems including
Global System for Mobile Communication-Railway and Terrestrial Trunked Radio have been
challenged in terms of capacity, coverage and quality. To address the capacity, coverage and quality
challenges, Long Term Evolution (LTE) has been emerged as an alternative important wireless
technology for railway.
Addis Ababa Light Rail Transit Service (AALRTS) has been operational since September 2015 serving
an average of 130,000 users daily with its two lines extended from east to west (Line 1) and
north to south (Line 2) of Addis Ababa. To AALRTS communication demand, LTE network has
been planned and deployed at 400 MHz carrier frequency. The network consists of 4 sites of 9 LTE
cells operating with 3MHz bandwidth and planned antenna and other configurations. Although the
network provides quality service for current rail voice/data service in most parts of both rail lines,
there are coverage challenge in some parts of the lines and it needs to be enhanced for the increasing
multimedia service demand.
The objective of this thesis is to quantitatively articulate aforementioned coverage challenge of the
LTE network for AALRTS and then to perform optimization campaign to address the challenge. To
articulate the coverage challenge, data is collected using drive test around challenged parts of the rail
lines beside data obtained from management system of the network. Drive test is undertaken using
Huawei EP680 LTE terminal and obtained data is analyzed using Matlab. Optimization is performed
for antenna parameters of existing network cells and location of a newly added cell using search
method from potential values. For the optimization, network simulation is performed using Win-
Prop network simulation tool and for propagation computation deterministic dominant path model
is applied. For performance analysis, signal-to-interference-plus-noise-ratio (SINR) is used as a key
metric.
Drive test result shows that 17% and 6% parts of Lines 1 and 2 SINR results are less than 7dB, respectively.
Independent and combined antenna height and power optimization provides significant
coverage improvement while antenna tilt and azimuth optimization present negligible performance
gains. Furthermore, adding a new LTE cell and optimizing its location presents excellent SINR improvement.
Description
Keywords
LTE, Railway, Coverage, Capacity, Quality, Optimization, Drive Test, Antenna Parameters