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An effective solution of ERAB problems in LTE
Conference Paper · October 2019
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International Conference on Engineering Technologies (ICENTE'19)
Konya, Turkey, October 25-27, 2019
___________________________________________________________________________________________________________
An effective solution of ERAB problems in LTE
A.GENC1
1
Isparta University of Applied Science, Isparta/Turkey, abdullahgenc@isparta.edu.tr
Abstract - E-UTRAN Radio Access Bearer (ERAB) is an
important parameter in LTE Key Performance Indicator
improvement on it. This parameter is formed by combining the
S1 bearer and the corresponding radio bearer. It can be noted
that this function is related to the E-RAB ID and Quality Class
Identifier. The E-RAB ID parameter is used to determine the
ERAB on the S1 interface. In a mobile network, there are values
that affect the quality of service, such as Bit Error Rate and the
end to end delay. These values define the QCI in LTE. The
planned improvements are not easy; hence the ERAB parameter
is composed of these different complex parameters. In this paper,
ERAP and parameters related to the Handover are improved by
proposed solutions of the results. As a result for downlink and
uplink, ERAB Call Drop Rate is 0.05 and 72.41, respectively.
Also, SINR Intra Frequency Handover is 337 and 406,
respectively. All of these initiatives were successfully completed.
Keywords - Mobile network, LTE, radio access network,
optimization.
T
I. INTRODUCTION
he completion of 4G technology is calculated at the
earliest in 2015. For this reason, 3G technology is
developed. Then, LTE technology is obtained as a result of
these studies. While this technology is called 3.9G or Pre4G, it
is stated that it is the last step in the field of communication
before 4G [1]. High-definition television service (HD-TV) and
multiplayer comes from interactive gaming service. This
requires an HD-TV 10 - 20Mbit / s communication speed (18
Mbit/s for Blue Ray standards). However, this technology is
well above the capacity of the previous technology, HSPA.
This situation revealed the delay problem. Multi-player
interactive gaming systems have great sensitivity to delay [2].
In this low latency issue, LTE has a 10ms latency for
simultaneous gamers has provided a complete key feature.
Considering that the HSPA has a latency of 60ms, it can be
seen how great it is.
The channel bandwidth increased from 1.25 20 MHz to 100
MHz in LTE. One of the major deficiencies of the
communication systems used is the interruptions in
communication and loss of data transmission while moving at
high speeds. With 100Mbit/s with 4G data transfer rates of
1Gbit/s are expected [3]. Performance in antenna
communications depends on improvements in an antenna
system. Recently for effective communication in the 4G
system, such as high speed, high reliability and long series
communications antenna technologies that affect multiple
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organs are emerging. Nowadays, many transmission programs
can be proposed to meet the increasing data rate needs of data
communication.
Spatial multiplexing has gained importance with bandwidth
conservation and power efficiency in LTE technology. Spatial
multiplexing requires the deployment of a wide range of
antennas in the transmitter and receiver. Independent currents
can be transmitted simultaneously from all antennas [4]. This
increases the speed of the data in a very large number of
different layers with an equal number of transmit and receive
antennas. This is called multi-input multi-output
communications (MIMO). Furthermore, reliability in the
transmission of high-speed data in the power-down channels
can be improved by using more antennas in the transmitter or
receiver. Transmission-reception difference and transmission
spatial multiplexing can be classified into space-time coding
techniques that do not require channel information in
transmission. Another category is closed loop multi-antenna
technology that uses channel information in the transmitter
[5].
In this paper, an effective and fast optimization study is
obtained for solving network quality problems in LTE
network. These have been applied in the area serving a
specific region and the effects of the optimization study on the
sites have been determined.
The rest of the paper is organized as follows: Section 2
describes measurement methods and DT details; Section 3
provides the brief discussion of the results, comparison of
before and after optimization to see performance of this study,
and finally Section 4 provides our conclusions.
II. MEASUREMENT AND DRIVE TEST
TEMS is mobile equipment (ME) to use in mobile and cellular
communications by Ericsson that includes all the field
information on uplink and downlink signals in the Airinterface. It covers all kinds of information about the signal
level and quality between the station and the ME [8]. In order
to determine the performance of the optimization, two separate
drive tests are performed before and after the study. Drive test
(DT) tool is given in Figure 1. It should be noted that the
block diagram is shown instead of the test tool in real time as
it is not allowed by the mobile operator. Here, it can be seen
ME used in active and passive mode, USB Cable for
connection of laptop and ME, GPS receiver, laptop and
charger to determine location and coordinates. Scanner is used
for to obtain all frequencies in operating band.
153
International Conference on Engineering Technologies (ICENTE'19)
Konya, Turkey, October 25-27, 2019
___________________________________________________________________________________________________________
Figure 1: Drive test tool and map
As the DT Methodology, DT is performed using TEMS. There
are 2 different measurement methods. All measurements are
made in Singapore. In Figure 3, the DT route is given. The
problematic points determined during DT in this region are
conducted according to the optimization study of this paper.
Figure 2: Cluster DT route (Planned)
III. RESULTS
E-UTRAN Radio Access Bearer (ERAB) is an important
parameter in LTE KPI analysis. This parameter is formed by
combining the S1 bearer and the corresponding radio bearer. It
can be noted that this function is related to the E-RAB ID and
Quality Class Identifier (QCI). The E-RAB ID parameter is
used to determine the ERAB on the S1 interface. In a mobile
network there are values that affect the quality of service
(QoS), such as Bit Error Rate (BER) and end to end delay.
These values define the QCI in LTE.
Another issue that makes ERAB parameter important is its
effect on RRC Success Rate in LTE. Here the RRC is the
Radio Resource Control. RRC Success Rate is required for
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service of the mobile network. And a Bearer can do that. The
bearer is usually defined as Data QCI9 by default and VoLTE
QCI1 as dedicated. As a result, Mostly ERAB is formed by the
addition of the default bearers.
As seen in Figure 3, suspected handover (H/O) failure from
PCI_85 to PCI_437 caused RRC connection reestablishment
request from UE that eNodeB rejected. So that ERAB released
abnormally. As a result of looking after neighbor list, both
sites are neighbor each other and also H/O from PCI_437 to
PCI_85 is preceded correctly. The solution of this problem is
to add site id to neighbor list to increase accessibility of
mobile network in site of PCI_85.
154
International Conference on Engineering Technologies (ICENTE'19)
Konya, Turkey, October 25-27, 2019
___________________________________________________________________________________________________________
Figure 3: ERAB Abnormal Rel. Analysis (DL Point1)
With point 2, also suspected H/O failure from PCI_85 of
site 3161 to PCI_86 in same site caused RRC connection
reestablishment request that eNodeB rejected. So that ERAB
released abnormally. Both sectors are neighbor each other.
These two abnormal release are all related to PIC_85 that
strongly suspected having unknown problem. The redress of
disconnection of RRC connection is increasing the power of
transmitter antenna to remain of received UE data in site 3161.
Figure 4: DL ERAB Abnormal Rel. Analysis (DL Point2)
Point suspected H/O failure from PCI_86 to PCI_404
caused RRC connection reestablishment request from UE that
E-ISBN: 978-605-68537-9-1
155
International Conference on Engineering Technologies (ICENTE'19)
Konya, Turkey, October 25-27, 2019
___________________________________________________________________________________________________________
eNodeB rejected. So that ERAB released abnormally. As a
result of looking after neighbor list, both sites are neighbor
each other and also H/O from PCI_404 to PCI_86 is preceded
correctly. On site of PCI_404 the antenna down tilt is
increased to prevent overshooting problem.
Figure 5: UL ERAB Abnormal Rel. Analysis (UL Point3)
During the UL Test, we faced up frequent UE disconnected
problem. After the HW check, it is observed that there is
connector problem on site. When the connector is changed
with new one, UE disconnected problem is solved for UL
point 4 in Figure 6.
Figure 6: UL ERAB Abnormal Rel. Analysis (UL Point4)
The Key Performance Indicators (KPI) of the mobile
E-ISBN: 978-605-68537-9-1
network is given Table 1. The optimization study by applying
proposed solutions have yielded good results. The statistics
conducted after optimization can be seen and most of the KPIs
156
International Conference on Engineering Technologies (ICENTE'19)
Konya, Turkey, October 25-27, 2019
___________________________________________________________________________________________________________
have improvement. The SINR Intra Freq HO Success Rate,
ERAB Accessibility Rate, Intra Freq HO Success Rate and
ERAB Accessibility Rate have the 100% success rate.
Therefore, it is seen that these parameters have high and good
results in the sites where optimization changes are made. Also
for downlink and uplink ERAB Call Drop Rate is 0.05 and
72.41, respectively.
Table 1: Performance results overview after optimization
Statistics
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KPI
Inter FreqHO Success Rate
SINRIntra FreqHO Success Rate
ERAB Accessiblity Rate
Inter FreqHO Success Rate
Intra FreqHO Success Rate
ERAB Accessiblity Rate
Performance
ERAB Call Drop Rate
ERAB Call Drop Rate
Mobile operators attach importance to the work of the
different departments listed in Figure 7 to achieve KPI goals
for network quality. Although the regions and methods in
which these various departments study are different, they can
directly affect each other's performance. For this, each unit
should study efficiently within the boundary and communicate
instantly with other units. However, they should work
productively and result-oriented. This provides ease of work,
power and time. Mobile technologies start with Design
process. In this process, simulation software related to radio
planning and wave propagation is used. Thus, what kind of
station can be applied to which region is determined. Then, in
the planning stage, the location of the stations according to the
target average signal level is determined from the map of
simulation. In the third stage of implementation the mobile
vendors make implementation of devices and components to
site. Then optimization engineers check the performance of
making optimization to improve the quality of related sites.
Last they inform mobile operator the process is done or not.
[2]
[5]
[6]
Figure 7: DT route
[7]
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Percentage
337
34
406
29
ERAB
Abnormal
Release
2
21
337
34
406
29
ERAB
Setup
Success
34
29
100
100
100
100
Rate
0.05
72.41
REFERENCES
[1]
[4]
E-UTRAN Radio Access Bearer (ERAB) is an important
parameter in LTE KPI analysis. Also, it directly effect of the
Success
RRC Success Rate of the mobile network. So, optimization
engineers work with RF planners to improve this parameter.
However, this improvement is not always easy, and not
immediately. Therefore, the optimization method to be applied
to the network should be as accurate and effective as possible.
In this study, the solutions proposed in the results section is
found to provide improvements in ERAB value and HO
parameters. As a result The SINR Intra Freq HO Success Rate,
ERAB Accessibility Rate, Intra Freq HO Success Rate and
ERAB Accessibility Rate have the 100% success rate.
Therefore, it is seen that these parameters have high and good
results in the sites where optimization changes are made. Also
for downlink and uplink ERAB Call Drop Rate is 0.05 and
72.41, respectively.
[3]
IV. CONCLUSION
Attempt
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Konya, Turkey, October 25-27, 2019
___________________________________________________________________________________________________________
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