IEEE Consumer Electronics Magazine - March 2018 - 46

Algorithm 1: Ellipse formation
and forwarding node selection.
1. if X max # Ymax
2. vertically partition the sensing area
3. else
4. horizontally partition the sensing area
5. end if
2
1
6. M = 2 * majoraxis and m = 3 * majoraxis
M2- m2
2
2
8. construct ellipse by taking the value from steps 6 and 7
9. if sensor ! data collector neighbor
10. set node as forwarding node
11. include the node in forwarding node list
12. end if
7. linear eccentricity: f =

the position of sensor nodes within or outside the ellipse is
determined. After the ellipse formation, two mobile data collectors are placed in the opposite part of the sensor field. Both
mobile data collectors rotate in their specified path and collect
sensed data from the collector nodes. Algorithm 1 presents
steps for ellipse formation and forwarding node selection.

THE DATA-FORWARDING NODE SELECTION
Data-forwarding nodes are the sensors closer to the mobile
data collector path. These nodes receive data packets from
source sensors through multiple paths. Mobile data collectors
select data-forwarding nodes in the sensing area before collecting the sensed data from the data-forwarding nodes.
Mobile data collectors rotate on the predefined path, send a
beacon message to the neighboring forwarding nodes, and
collect the sensed data from the forwarding nodes. Both of the
mobile data collectors start moving in the elliptical path from
the base station, and, on the first rotation in their assigned
path, they select all of the neighboring sensor nodes within a
one-hop distance of data-forwarding nodes, as shown in Figure 6. The forwarding node reports to the mobile data collec-

Forwarding Node

Normal Node

Data Collector

FIGURE 6. The data-forwarding node selection.
46 IEEE Consumer Electronics Magazine

MARCH 2018

tor node with neighbor information. If the energy level of the
mobile data collector node is lower than a threshold, then it
selects one of the neighboring nonforwarding nodes (or an old
forwarding node) that is within the range of the data collector
as the new forwarding node.

THE NEIGHBOR DETECTION
According to the proposed technique, source sensors transmit
the data packets to the forwarding node, followed by the data
collector retrieving data from them by rotating in the predefined
elliptical path. The sensor node has two main functionalities: 1)
to ascertain the recipient of the data and 2) determine the direction in which the data is to be sent. Therefore, an important task
for source sensors is to determine their neighbors to which they
send sensed data.
Sensors have their own position information at the time of
node deployment. These sensors determine whether they are
within or outside the ellipse using their position information. If
a sensor finds its position outside of the ellipse, then it sends
data toward the ellipse center, whereas sensors send data away
from the ellipse center of that partition if they have found their
own position inside the ellipse. The clear data inward or outward flow is shown in Figure 7. Later, they find their neighbors
after the partition of the sensing area. The neighbor detection
in this technique has two different phases: 1) the set-up phase
and 2) the data collection phase.

THE SET-UP PHASE
This phase consists of the procedures to partition sensor field,
ellipse formation, and forwarding node selection. Data collectors send beacon messages to their one-hop neighbors to get
to the forwarding node. Sensors respond to the collector
node's beacon message if they have enough energy to participate and are also a one-hop neighbor from the elliptic path.

THE DATA COLLECTION PHASE
The source node forwards the sensed data to the nearest collector node based on its position. Forwarding nodes store the data
packets and wait for the data collector's presence to forward

Data Collector
Normal Node

Source
Forwarding Node

FIGURE 7. The data packets toward the forwarding node.

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