project deals with the implementation of Vehicle to Vehicle (V2V) communication
by using cellular technology known as Long Term Evolution (LTE). This section
defines this technique and explains advantages and disadvantage of implementing
V2V communication with LTE.
Long Term Evolution (LTE) is a cellular standard which is
developed by 3G Partnership Project (3GPP). LTE is based on the principles of
pre-existing cellular technologies like Global System for Mobile
communication(GSM) which is a 2nd generation cellular network and
Enhanced Data rate for GSM Evolution (EDGE). LTE is developed to improve the
overall standards of communication devices in order to provide high speed
cellular services and to compete with different cellular techniques like WiMAX.
As number of users that are using cellular system in increasing day by day, LTE
comes with a technique known as UMTS Terrestrial Radio Access Network which is
described in 28P1 .
This technology helps LTE to improve the latency of the data packets,
throughput to end user which in turn increases the user experience. LTE works
on a network architecture called Evolved Packet Core (EPC) architecture which
provides which supports E-UTRAN. EPC architecture uses TCP/IP network protocols
which allow LTE to support all services that uses IP addresses to work. These
services include voice over IP, video sharing like conference and application
for transmitting rich media etc. This architecture makes it easy to perform
handover (vertical handover) from one cellular technology to other whether it
is wired or wireless. This allows network operator to provide uninterrupted
services to the users. Physical layer of Long Term Evolution cellular technique
implements different technologies like Orthogonal Frequency Division Multiple
Access (OFDMA) which is used in downlink between base station and mobile node,
Single Carrier Frequency Division Multiple Access(SC-FDMA) which is used in
uplink and Multiple Input Multiple Output.
2.3.2 Features of LTE
2.3.2.a Use of OFDMA and SC-FDMA
release of 3GPP, a RAN is introduced which uses OFDMA technique and modulation
for downlink and SC-FDMA for uplink. OFDMA scheme divides the available channel
into various carriers which can transmits different parts of signal. At
receiver the output of every carrier can be combined to form complete signal.
This is known as multiple carrier transmission. Modulation techniques like 64-bit
Quadratic Amplitude Modulation and FEC are supported in LTE to increase the
efficiency OFDMA scheme. Techniques like MIMO and beam forming are integrated.
Each station can use maximum of four antennas. Due to using these techniques in
LTE, the rate of data exchange for downlink goes up to 30Mbps for every 20Mz
frequency. For uplink, rate of data exchange goes up to 75Mbps for every 20Mhz
2.3.2.b Optimized network Architecture
Evolution’s architecture is based on all-IP network. This results in reduction
of latency, improve the efficiency of system and enables operations between
technologies that are 3GPP standardized or non-3GPP standardized.
2.3.2.c Use of Advance Antennas
like Multiple Input Multiple Output, Spatial-Division Multiple Access (SDMA),
beam forming etc. are used to increase the efficiency of LTE. These techniques
also provide control over various aspects that results in much better user
Architecture of LTE
Following figure gives the network
architecture which is supported by Long Term Evolution.
Figure 2.3 Architecture of LTE
Different elements of LTE’s
architecture are defined as follows: –
1. Evolved Radio Access Network
This element consists of
advanced base station node (eNode B). This node communicates with mobile user. This
node supports physical layer, Media Access Control (MAC), RLC and PDCP.
2. Serving Gateway
The function of Serving
Gateway (SGW) is to forward the data to or from users. SWG acts like a medium
between two mobile nodes during handover. It helps in vertical handovers- when
handover occurs from one cellular technology to another. Serving Gateway
terminates the connection of base station with node when there is no
transmission for some time. When data arrives for that node, it sends a paging
message in order to reinitiate the connection between node and base station.
3. Mobility Management Entity
Mobility Management Entity is
responsible for handling control information for mobility of nodes. When a node
is not transmitting or receiving and is in idle state MME keeps the track of
paging signal for node. MME also controls activation ad deactivation of
to Vehicle Communication via. LTE
Vehicle to Vehicle communication is
implemented in order to increase the road safety by supporting various active
road safety applications. These application works in the favour of reducing the
number of car accidents and the major requirement for these applications are
availability and reliability. In 29P2 , two safety messages are defined which are transmitted periodically or
are event triggered and are called cooperative awareness messages (CAMs) and
decentralized environmental notification messages (DENMs). CAMs are short
messages which are send by each vehicle to every other nearby vehicle to tell
about its location, status, position etc. DENMs messages that are send whenever
some event occurs. These are short messages that are sent to inform other
vehicles about events like accident.
In Vehicular Ad hoc Networks, IEEE
802.11p standard is used to provide various vehicle applications that are
defined by International Transport System (ITS). IEEE 802.11p provides various
advantages to VANETs which includes easy installation, cost effective,
developed technologies and ability to support vehicle to vehicle communication.
However, this technique faces the problem of scalability, unknown delays and
low Quality of Service (QoS) 30P3 . Because of low available bandwidth, it connections between nodes are
short lived. These drawbacks of IEEE 802.11p, shifts the focus towards usage of
latest cellular technique, Long Term Evolution (LTE), as a solution. LTE can be
a better option for implementing vehicular to vehicular communication because
it provides high rates at which packets are sent and improved latency. LTE can
operate over a large area with ability of penetration and can support to highly
dynamic. Extending its use to also support vehicular applications would
open new market opportunities to telco operators and service providers 30P4 .
2.4.1 Features of LTE
are several properties or features of Long Term Evolution (LTE) that makes it a
suitable technique for implementing vehicular networks. Some of them are
discussed as follows: –
2.4.1.a Coverage and
will be based on the installation of enhanced base station that is operated in
cellular network infrastructure that offers coverage over a large area. This
will provide solution to the problem of short-lived or poor connectivity
between nodes which is faced in IEEE 802.11p technique. LTE could also connect
fragments of network and creates connectivities in the areas where vehicle to
vehicle communication cannot be made difficult communication conditions or due
to low density of nodes.
High Penetration Rate
The penetration rate achieved by IEEE
208.11p is much less that what will be achieved by LTE. High penetration rate
will be achieved in LTE as this technique can be deployed in various smart
phones which will keep users connected to internet even when they are mobile.
Capacity in LTE
As discussed earlier, very high
capacity of transmitting data using LTE can be achieved. For downlink it could
go up to 300Mbps and for uplink it can go up to 75Mbps. This can also reach at
1Gbps if an advanced version of LTE is used (LTE-A). This shows that LTE
enables channels to support large number of vehicle as compared to 802.11p
because its capacity is only limited up to 27Mbps.