Prof. Chetana V. Samundre
, Rajshri Suryavanshi,
Abstract-Wireless sensor network(WSN)
consist of compact distributed self-organizing wireless nodes with small amount
of CPU memory, low processing power and low battery capacity. The wireless
nodes generates different types of data packets such as real time and non-real
time data packets because it sense environmental situations.
WSN uses most existing packets
scheduling system i.e. First come first serve(FCFS).In FCFS concept the data
packets which enter the node first will leave the node first. In this process
there might be starvation of real time data packets because data packets are
processed according to the time but they are not processed according to
Scheduling different type of package
in WSN is highly important since it ensure deliver of different type of packets
based on their priority and fairness with minimum latency.
Disha Kathane, Tejashree Pandit
Wireless sensor networks (WSN)
consist of more than hundreds of small spatially distributed autonomous devices
using sensors called sensor nodes to monitor the physical and environmental
situations such as sound vibration, temperature, pressure, motion and intensity
of light. WSN has gained a great value and importance due to flexibility,
cheaper implementation cost, mobility etc. The sensor networks are expected to
play increasingly important role in future especially in monitoring and
military applications on large scales and it consists of small and inexpensive
sensor nodes that have limited memory, limited computing power, and that
operate using batteries.
Scheduling of different packets at
the sensor nodes is very important as ensures the delivery of the data packet
on the priority basis. The sensed data may be real time or non-real time.
Highest priority should be given to real time data sense by the node compare to
non-real time data packet. Sometime the nodes may be put to sleep mode, when
there is no data packet available and as soon as the data packet arrives at the
node is putted into wake mode. This reduce the sensor node energy consumption.
Fig.1: Diagram of energy efficient multilevel
priority packet scheduling scheme for
Sensor nodes are smart, small in size
light weight that monitor physical and environmental situations. The data
sensed at the wireless sensor nodes is to be sent to a base station nodes via
LAN connection that connects all the nodes of WSN that uses very less bandwidth
base station collect the data from various nodes using single hope transmission
and sometimes multi hope transmission.
The packet scheduling scheme for WSN, in which
overcome all drawback occurred in existing scheduling algorithm. The DMP packet
scheduling scheme for WSN, in which sensor nodes are virtually organized
hierarchical structure. In DMP packet scheduling scheme for WSN, where each node maintains three level into
its queue for three different types of data packets. This is because we
classify data packets as (1) real time (highest or priority1), (2) non real
time remote packets i.e., packet that arrive from the sensors nodes at lower
level (priority 2), and (3) non real time local packet(lowest priority 3).
Non-real time data packets are classified based on the location on sensor nodes
to balance to end-to-end delay of data packets that are generated at different
locations. Non-real time data traffic with the same priority are processed
using the shortest job first (SJF) scheduler scheme since it is very efficient
in turns of average task waiting time.
this section, we define the following
terminologies and factors that are used in packet scheduling scheme.
Deadline First (EDF): -Whenever
a number of data packets are available at the node and each packet has a
deadline within which it should be sent to base station. The data packet which
has the earliest deadline is sent first.
Data that have travelled the longest distance from the source node to
base station and have the shortest deadline, are given highest priority. If the
deadline of a particular data packet expires, the most suitable data packets
are send at an intermediate node.
First Come First Serve (FCFS):- The
first come, first served scheduling system is the simplest scheduling system in
which packets are processed as they come.
It is the method that was used to support real-time communication. In
this scheduling system it might be possible that the data packet that should
reach base station as early as possible take time. Therefore to avoid time
consumption the data packets are prioritized. Packet Type Packet scheduling schemes can be classified based on
the types of data packets, which are as follows.
data packets: – Packets
at sensor nodes should be scheduled based on their types and priorities.
Real-time data packets are considered as the highest priority packets among all
data packets that are present at the node. Hence, they are processed with the
highest priority and delivered to the base station with a minimum possible
data packets:- Non-real time data packets have lower priority than
real-time data packets. They are hence delivered to BS either using first come
first serve or shortest job first basis when no real-time packet exist sensor
This section, we define some of the Terminologies and genera assumptions which
are used in designing the Dynamic Multilevel priority (DMP) Packet
We make some of the following
assumptions to design and implement DMP packet Scheduling Scheme.Only real time data packets and
non-real time data packets are present in the data traffic medium for e.g.
non-real –time data sensed by temperature data and real-time data body sensors.Both types of data packets are of same
size i.e. real-time and non-real –time.In the network all sensors node are
time synchronized.For real- time data there is no data
aggregation is performed at intermediate nodes.Depending upon the Number of hop counts
nodes are considered located at different levels.By Using TDMA scheme timeslots are
located to nodes.Each sensor nodes have ready queue
which is divided into three individual queues only (For real –time data pr1,
For non-real-time data pr2 and
non-real-time local data pr3.The length is variable for data queues
in sensor nodes. For instant pr1 length is smaller than pr2 and pr3 queues are
this section, we described the following factors and terminologies which are
important in designing the DMP packet Scheduling scheme.
protocol in which network is a virtually arrange into a hierarchical structure,
considering base station act as the root node, and the sensor nodes that are
adjacent to the base station are deem to be at level and nodes in zone with hop
distance of 1 from base node are refer to be at level1 and so on, and nodes
which are situated at the boundry are called as leaf nodes. To avoid complete
depletion of Energy of a sensors node, a Zone-based Routing protocol is
or Task Scheduling at every nodal level is done using a Time Division Multiple
Access(TDMA) scheme. Every level in the Routing protocol is distributed with a
time slot. There is a variation of time slots. In the design of DMP scheduling
variable time slots are used because nodes at lower levels have more number of
packets as compared to the nodes which are far from the base station.
Considering the Observation, the length of time slots at upper-level nodes is
set to a higher value.
Fig.2: Proposed dynamic multilevel
priority (DMP) packet scheduling scheme
scheduling within the Queue-Depending
on the scheduling the DMP packet scheduling, Data packets i.e. real-time and
non-real time data packets are scheduled among the multiple queues. Existing
scheduling technique are SJF and FCFS scheduling within in queue of these
scheduling techniques of starvation free, so we propose a round robin
scheduling neither round robin approach. In this approach the ready queue is
performed as circular queue.
are some observations of Round robin:
default it is preemptive algorithm rather than non-preemptive.
processing at least once it allocates CPU to a packets in a row.
As we discussed before, there are two types of data packets, in which real-time
data packets and emergency data should have highest priority and non-real-time
data packets is transfer the priority depending on the sensed location and size
of data. The data packets that are received by node n from the lower level are
given highest priority. however, If it
is noted that the lower priority non-real timer local data cannot be
transmitted due to continuous coming up of higher priority and non-real-time
remote data, they are preempted to allow low-priority data packets to be
preserve after a inescapable waiting period.
metric convince hat packets of extraneous priorities find out with a minimum
waiting time at the ready queue based on the priority of tasks or packets. For
instance, if any lower-priority packets waits for a long period of time for the
continuous reach of greater-priority packets, fairness defines a constraint
that permit the lower-priority packets to attain processed after a secure
waiting time. Location
on sensor nodes to balance to end-to-end delay of data packets that are
generated at different locations. Non-real time data traffic with the same
priority are processed using the shortest job first (SJF) scheduler scheme
since it is very efficient in turns of average task waiting time
An energy efficient multilevel priority task
scheduler has better than FCFS, and multilevel queue scheduler in terms of
average task waiting time, both for real-time tasks, and all types of tasks.
Using the concept of three level priority queues at each node, the proposed DMP
task scheduling scheme allow different types of data packets to be processed
base on their priorities. Dynamic Multilevel Priority (DMP) packet scheduling
scheme, its prerequisites and the factors that are being considered in the
algorithm. This paper deals with issues such as – how the starvation of both
types of data packets is avoided, how the processing overload, average
end-to-end delay is reduced for the delivery of both real-time and
non-real-time data packets. We studied the DMP packets scheduling scheme that
improves the overall performance of scheduling in a WSN.
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