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Abstract—The Long Term Evolution (LTE) is the latest step
in an advancing series of mobile telecommunications systems.
In this paper, authors show interest on the link budgeting the
information presented here will help readers understand how
the budgeting will be done in LTE. This paper provides
dimensioning of LTE for particular city. This will provides the
number of cell count. Here we tell about a GUI MATLAB
System for calculation of no. of resources required to provide
services in particular area with optimum cost and better
quality.
INTRODUCTION
Driving the evolution of wireless broadband technology is
user’s increasing expectations for speed, bandwidth, and
global access. For wireless carriers to achieve greater speeds
and pervasive connectedness, their networks need to start
behaving more like landline IP-based networks. This line of
thinking represents a fundamental shift in perspective from
mobile services to broadband connections for users and
service providers alike to enter the fourth-generation
(4G).Unlike earlier wireless standards, 4G technology is
based on TCP/IP, the core protocol of the Internet. TCP/IP
enables wireless networks to deliver higher-level services,
such as video and multimedia, while supporting the devices
and applications of the future. This point of time, there are
two technologies which can provides such user experience
IEEE’s WiMAX and 3GPP LTE. The service provider
believes that make LTE offers a number of significant
technological and business advantages over WiMAX that
make it a superior networking standard. Long Term Evolution
(LTE) has been designed to support only packet-switched
services. It aims to provide seamless Internet Protocol (IP)
connectivity between User Equipment (UE) and the packet
data network (PDN), without any disruption to the end user’s
applications during mobility
The term “Long Term Evolution” encompasses the evolution
of the Universal Mobile Telecommunications System
(UMTS) radio access through the Evolved UTRAN
(E-UTRAN) it is accompanied by an evolution of the
non-radio (Core Network) aspects under the term “System
Architecture Evolution” (SAE), which includes the Evolved
Packet Core (EPC) network.
At a high level, the network is comprised of the Core Network
(EPC) and the access network E-UTRAN. The Core Network
consists of many logical nodes. The core network in LTE is
called Evolved Packet Core (EPC) which is responsible for
the overall control of the UE and establishment of the bearers.
The main logical nodes of the EPC are PDN Gateway (PGW),
Serving Gateway (S-GW), Mobility Management Entity
(MME), Home Subscriber Server (HSS), Policy Control and
Charging Rules Function (PCRF) The access network is made
up of essentially just one node, the evolved NodeB (eNodeB),
through which Connects UE to the network. Each of these
network elements is interconnected by means of interfaces
that are standardized in order to allow multi-vendor
interoperability. This gives the possibility to source different
network elements from different vendors.
II. OBJECTIVES AND APPROACH
This work describes the dimensioning process of 3GPP LTE
access network, its models, methods and the tool developed to
dimension the network.
The main objectives are listed below:
• To identify the level of throughput for optimum
cost and acceptance quality.
• Introduction of LTE features relevant for the
dimensioning
• Definition of the basic models for Access
Network Dimensioning
• Coverage Estimation for LTE using 2.3 GHz.
frequency
• Network Element Count(cell count) Estimation
for any particular area
EVOLUTION: 1G AMPS TO 4G LTE
The various communications systems looking in the past
revolutionized the way people Communicate, joining together
communications and mobility. Evolution of wireless access
technologies is about to reach its fourth generation (4G).
Looking past, wireless access technologies have followed
different evolutionary paths aimed at unified target:
performance and efficiency in high mobile environment. The
first generation (1G) AMPS has fulfilled the basic mobile
voice, while the second generation (2G) GSM (3GPP),
CDMA one (3GPP2) has introduced capacity and coverage.
This is followed by the third generation (3G), UMTS,
WCDMA (3GPP) and EV-DO (3GPP2) which has quest for
data at higher speeds to open the gates for truly “mobile
broadband” experience, which will be further realized by the
fourth generation (4G).
KEY FEATURES OF LTE
The 4 G Long Term Evolution has following key feature
which make this technology superior than other
technologies.
1. Peak Through put: -Peak download rates up to
300 Mbps and upload rates up to 75.Mbps depending on the
user equipment category (with 4x4 antennas using 20 MHz
of spectrum).
2. Low Latency: -Low data transfer latencies (sub-5ms
latency for small IP packets in optimal conditions), lower
latencies for handover and connection setup time than with
previous radio access technologies.
3. Mobility Support:-Improved support for mobility,
exemplified by support for terminals moving at up to
350 km/h (220 mph) or 500 km/h (310 mph) depending on
the frequency band.
4. Access Technologies:-OFDMA for the downlink,
SC-FDMA for the uplink to conserve power.
5. Duplexing Support:-Support for both FDD and TDD
communication systems as well as half-duplex FDD with the
same radio access technology
6. Flexible Bandwidths: - 1.4 MHz, 3 MHz, 5 MHz,
10 MHz, 15 MHz and 20 MHz
7. Large Cell Size Support:-Support for cell sizes from tens
of meters radius (Femto and Pico cells) up to 100 km radius
microcells. In the lower frequency bands to be used in rural
areas, 5 km is the optimal cell size, 30 km having reasonable
performance, and up to 100 km cell sizes supported.
8. Simplified architecture: LTE architecture is FLAT IP
Based. The access side of LTE is composed only of eNodeB.
Support for inter-operation and co-existence with legacy
standards like GSM/EDGE, UMTS and CDMA2000.
V. BENEFITS OF LTE
• Provides a global ecosystem with inherent mobility
• Offers easier access and use with greater security and
privacy
• Dramatically improves speed and latency
• Delivers enhanced real-time video and multimedia for
a better overall experience
• Enables high-performance mobile computing
• Supports real-time applications due to its low latency
• Creates a platform upon which to build and deploy the
products and services of today and those of
tomorrow
• Reduces cost per bit through improved spectral
efficiency.
VI. TECHNICAL DIFFERENCES BETWEEN LTE
AND WiMAX
There are so many number of technical differences exists
between LTE and WiMAX. These differences shows that
LTE have so many advantages over WiMAX.
LTE DIMENSIONING PROCESS
LTE Dimensioning process starts with the Radio Link Budget
Calculations, used to determine the maximum path loss. The
result of this step depends upon the propagation models used.
The estimated cell size, obtained in this step, leads to the
maximum allowed size of the cells. This parameter is used to
calculate the number of cells in the area of interest. Thus, a
rough estimate of the required number of eNBs is obtained.
This paper work focus is on Radio Link Budget, cell coverage
estimates and tools and case studies for LTE dimensioning.
Figure depicts LTE dimensioning exercise in detail. Coverage
Planning is the first step in the process of dimensioning. It
gives an estimate of there sources needed to provide service in
the deployment area with the given system parameters,
without any capacity concern. Therefore, it gives an
assessment of the resources needed to cover the area under
consideration, so that the transmitters and receivers can listen
to each other. In other words, there are no QoS concerns
involved in this process. Coverage planning consists of
evaluation of DL and UL radio link budgets. The maximum
path loss is calculated based on the required SINR level at the
receiver.The minimum of the maximum path losses in UL and
DL directions is converted into cell radius, by using a
propagation model appropriate to the deployment area. Radio
Link Budget is the most prominent component of coverage
planning exercise
. RADIO LINK BUDGET
A link budget is the accounting of all of the gains and losses
from the transmitter, through the medium (free space, cable,
waveguide, fiber, etc.) to the receiver in
a telecommunication system. It accounts for the attenuation
of the transmitted signal due to propagation, as well as
the antenna gains, feed line and miscellaneous losses.
Randomly varying channel gains such as fading are taken into
account by adding some margin depending on the anticipated
severity of its effects.
A simple link budget equation looks like this:
Received Power (dBm) = Transmitted Power
(dBm) + Gains (dB) − Losses (dB)
The link budget calculations estimate the maximum
allowed signal attenuation between the mobile and the base
station antenna. The maximum path loss allows the
maximum cell range to be estimated with a suitable
propagation model. The cell range gives the number of base
station sites required to cover the target geographical area.
As we know LTE is a packet network and most of the
services are data service. So the Link Budget is for LTE is
made on the base of cell edge throughput. The limiting Link
is the Uplink Link due the low transmit power of User
devices generally 23dBm.
Principle of Link Budget
Maximum allowed path loss (MAPL) = Transmit power -
Receiver Sensitivity - Losses - Margins + Gains
Cell radius:
MAPL = Intercept + 10 *Slope *Log10 (Cell Radius)
Cell Radius = 10(MAPL – Intercept) / (10 *Slope)
All above parameters can be used to calculate the Max.
Allowable path loss (MAPL).
Next step is to find out the cell radius, to calculate cell radius
which have to use propagation model. There are different
propagation models like Cost Hata model, Log Normal
Propagation model. After getting cell radius we will find out
the area covered by a single cell site. If we consider a
hexagonal cell site design then area cover by a cell can be
calculated by below formula.
Let X be the area covered by a cell site and Y is the area of a
city to be covered.
Then no. of cell site Z to cover the city is:
Z = Y / X
Further we can find out the cost of the project by simply
multiplying the total cost of one site expenses. Let R is the
expense for one cell site then total cost for the project for a
city will be
Total cost of project of the city = R * Z
IX. DIMENSIONING TOOL
Matlab GUI is used to dimension the wireless system. In
Matlab a system is constructing in which different inputs are
given and their corresponding output is analyzed in GUI
system. MATLAB is well known for its numerical problem
solving power. Traditionally programs written by engineers
have very simple interfaces, and often only the author is the
one who uses the program once it is completed. There are
occasions where a more polished user interface, specifically a
graphical user interface (GUI) is desired:
• You wish to have a nontechnical, yet computer
literate, person use your programs to perform