25-09-2013, 03:09 PM
A Method for Improving Data Delivery Efficiency in Vehicular Adhoc Networks
Improving Data Delivery.pdf (Size: 731.78 KB / Downloads: 66)
Abstract
As vehicular networks become popular and many vehicles want to access data through a
roadside unit. In this paper, there was a vehicle to roadside communication and we propose
scheduling schemes for efficient delivery of data packets in vehicular adhoc network. On the
basis of priority scheduling algorithm vehicles can download/upload the data from RSU. In
this paper we can control the congestion and delay of data by assigning the priorities to the
message. The process with highest priority is executed first and highest priority is assign to
those processes which have the smallest data size and this scheme is the smallest data size
first scheduling(SDF) . If the two processes having the same data size then we can assign the
priority on the basis of first come first serve scheduling (FCFS). We can combine these two
algorithms and the new algorithm D*A. is introduced. This algorithm is responsible for only
sending the commercial messages and the safety messages will be send on the different
channel. The emergency messages will be sending through control channel with help of EDF
scheduling. This paper increases the efficiency and throughput of the process and decreases
the turnaround time for the process.
Introduction
VANET is an emerging standard for data communication between moving vehicles and
fixed equipments. It integrates components of WiFi, Bluetooth and other mobile connectivity
protocols to facilitate data transfer between cars and between road side equipment and
automobile traffic. The protocol needs of vehicular communication are unique the
communication occurs32 in a constantly fluctuating environment. The signal must
accommodate multiple signal and traffic densities and work in both urban and rural
environments.
Car-to-roadside communication is based on a WLAN (IEEE 802.11p) platform developed
especially for vehicles, while IEEE 1609 is a higher layer standard on which IEEE 802.11p is
based. IEEE 802.11p is an approved amendment to IEEE 802.11 that adds WAVE. It
therefore defines the enhancements to 802.11 required to support Intelligent Transportation
Systems (ITS) applications, including data exchange between high-speed vehicles and
between those vehicles and the roadside infrastructure in the licensed ITS band of 5.9GHz
(5.85 - 5.925GHz). WAVE standards define architecture and a complementary, standardized
set of services and interfaces that together enable secure vehicle to- vehicle (V2V) and
vehicle-to-infrastructure.
Literature Work
The different variety of services are provided by Vehicular Networks, ranges from safety
and crash avoidance to Internet access and multimedia applications [8] .There is a lot of work
and research is being conducted to study problems related to the vehicular communications.
Different problems that can take place is network architecture, protocols for physical and link
layers, routing algorithms, as well as security issues.
Vehicle-roadside data access is an important issue for data access in vehicular networks.
The authors in [1] illustrated a basic picture of a radio architecture that offers two-way
transmission services essential to Intelligent Vehicle Highway Systems (IVHS) using only a
single (30 kHz) radio channel. This bandwidth can support the multiple communication
services such as data casting, packet switched transmission to and from vehicles, collection of
traffic data from probe vehicles and transmission of emergency messages. The emergency
message are those message that are generated as a result of a dangerous situation or we can
say that, when an abnormal condition is detected such as road accident. The emergency
message is disseminated within a certain area with high priority [2]. Emergency and beacon
messages will send through one single channel known as Control Channel (CCH). The
Federal Communications Commissions (FCC) has allocated the frequency spectrum to
Dedicated Short Range Communication (DSRC) in VANETs. The DSRC spectrum is divided
into seven (7) 10MHz channels range from 3 to 27 Mbps and it contain the central channel
(channel 178) that is the control channel (CCH) which is restricted to emergency
communications only. The function of WAVE is to provide safety messages are delivered
over a dedicated CCH communication channel, while non safety or commercial messages are
delivered over a service channels (SCHs)
Data Delivery in VANET
Communication in VANET take place over wireless link and VANET contains electronics
embedded inside vehicles and installed on RSU. Data communication between the vehicles
and RSU may be unidirectional or bidirectional. When the communication takes place then
the vehicle/car will choose the nearest RSU to send its data or the request [11]. But if at that
time RSU is too busy, the data will get lost and the bandwidth will be wasted. In this paper to
overcome the problem of bandwidth wastage we use the scheduling schemes so that at proper
time the data will send with delay control.
System Model
As shown in the Figure 3 when the vehicles are in the communication range of RSU then
they can upload the data from RSU. The RSU maintain the non-preemptive service cycle. In
non-preemptive scheduling one service can not be interrupted until it finishes. The
communication takes place with the help of wireless channel. If the vehicles want to access
the data from RSU then the vehicle can send the request to RSU. Each request consists of
three tuple: <v-no., d-id, opr> where v-no. is the number of the vehicle, d-id is the identifier
of the requested data item and opr is the operation that vehicle can do i.e. upload or download.
Based on the scheduling algorithm the RSU serves one request and remove it from the queue.
The figure shows the architecture of vehicle roadside service scheduling.
Conclusion and Future Work
In the paper, we addressed some challenges in vehicle roadside data access. We proposed
the framework of the congestion control approach. With the help of congestion control we
efficiently deliver the data in VANET and also the time complexity reduces. As in dense
network, CCH channel is easily congested by the beacon message and also by the emergency
message so, we proposed to adapt priority based EDF scheduling algorithm in our congestion
control. After sending the safety message we will send the commercial message so we
proposed a basic scheduling scheme called D*A which will consider both algorithm i.e. SDF
and FCFS where D is the data size and A is the arrival time of request in the buffer memory
of RSU. This will help in improving the reliability and scalability of a process.
This paper focuses on service scheduling issues in vehicle-roadside data access. With the
help of congestion control approach we should reduce the channel load in order to meet the
QoS requirements of the wireless network performance. This paper increases the efficiency
and throughput of the process and decreases the turnaround time for the process. With the
help of proposed algorithm the time complexity of a process reduces. Therefore, in the future
we plan to improve reliability of D*A by implementing implicit acknowledgement. We also
plan to inspect other improvements in terms of implementing security in the system.