Presenter: Gurjot Singh Energy Conservation and Collision Avoidance by Controlled Access Protocol in WSN Presenter: Gurjot Singh

CHALLENGES There is a huge significance noticed for WSN since its inception. It is due to the variety of applications that WSN support. But WSN primarily suffers from less battery capability of nodes. Replacing the battery is not feasible. Due to this problem, the research fraternity, is trying to adopt the techniques which can minimize its consumption.

CHALLENGES Contd. Proper utilization of allocated bandwidth. No coordination can lead to use of same channel by two nodes. It will result in collisions due to data transmission in same channel leading to: (a) Collisions (b) Wastage of Bandwidth (c) Loss of Energy at node end due to retransmissions

NEED A mechanism through which they can coordinate themselves to avoid collisions. A mechanism to conserve energy at node end.

MAC PROTOCOL The role of MAC protocol is to provide media access to various devices. Variety of MAC PROTOCOLS: Random Access Protocols Controlled Access Protocols

PRIME FOCUS Energy Conservation during MAC operation helps significantly to increase the node and network lifetime.

Limitations of Existing MAC Protocols In random access protocols (CSMA etc.) problems like hidden node and exposed node problem exists. These issues results in great loss of energy due to collisions and also disrupt the operation. Back off slots are used in CSMA/CA to avoid collisions but it leads to more delay and possibility of data loss.

Fig. 1. Low power slotted CSMA/CA operation [1] Fig. 2. Working Principle of ‘Poll’ mechanism [8]

Fig. 3. Operation of ‘MACA - BI’ Protocol [9] PROPOSED TECHNIQUE: Receiver Initiated MAC Protocol is suggested. MACA-BI (Multiple Access with Collision Avoidance – By Invitation) is proposed. It is controlled access protocol where nodes can transmit data only by invitation. Fig. 3. Operation of ‘MACA - BI’ Protocol [9]

Challenges in the implementation Threat: When secondary has data to transmit but primary is not initiating the communication. Every node has limited memory capability if delay in transmission will increase probability of losing the data will also increase.

Fig. 4. Operation of ‘MACA’ Protocol [9] Solution advised MACA can be used to resolve this issue. It is a sender Initiated MAC protocol. Proposed protocol by author says: Hybrid technique = MACA(BI) + MACA (But one at a time) Fig. 4. Operation of ‘MACA’ Protocol [9]

Switching from MACA-BI to MACA Whenever the transmitting node queue length increases or packet delay exceeds certain acceptance threshold.

Fig. 6. Flow Chart of Controlled Access Protocol using MACA-BI & MACA

TABLE I. Current & Power Consumption of node [4] Fig. 9. Comparison of Energy consumption Fig. 8. Collisions in Controlled Access Protocol while MACA-BI in use

TABLE II. Lifetime (WSN) using Controlled & Random Access Protocol Fig. 10. Lifetime Comparison TABLE II. Lifetime (WSN) using Controlled & Random Access Protocol

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