Z-SEP: Zonal-Stable Election Protocol for Wireless Sensor Networks

1. INTRODUCTION

• WSNs use sensor nodes to sense and process data and communicate it, with protocols requiring self-organization for accurate and efficient operation.Source: §1 · p. 1
• Clock-driven, event-driven, and query-driven communication all raise energy-efficiency concerns tied to extending sensing time and network lifetime.Source: §1 · p. 1
• LEACH gives all nodes the same cluster-head probability and performs poorly in heterogeneous networks, while SEP weights probability by energy but does not efficiently use higher-energy nodes.Source: §1 · p. 1
• Z-SEP combines direct transmission to the base station with clustering to transmit data.Some nodes send data directly, while others use a clustering algorithm.Source: §1 · p. 1
• The paper reports that its hybrid approach enhances stability period, network lifetime, and throughput.Source: §1 · p. 2

2. RELATED WORK AND MOTIVATION

• E-SEP adds an intermediate-energy node level, while DEEC forms cluster heads using residual node energy and average network energy.Source: §2 · p. 2
• TEEN uses hard and soft thresholds to reduce transmissions in time-critical applications, although it was proposed for homogeneous networks.Source: §2 · p. 2
• SEP may consume more energy when most randomly deployed normal nodes are far from the base station, shortening stability and reducing throughput.Source: §2 · p. 2
• Z-SEP places normal nodes near the base station for direct transmission and uses clustering only for higher-energy advance nodes farther away.Source: §2 · p. 2

3. TERMINOLOGIES USED

• Stability period runs from network start until the first sensor node dies, while instability period runs from the first node's death until the last node dies.Source: §3 · p. 2
• Throughput is the total rate of data sent over the network, including cluster-head-to-base-station and node-to-base-station transmissions.Source: §3 · p. 2
• Network lifetime runs from network start until the last alive node dies; an epoch is the number of rounds before a node becomes eligible for cluster head.Source: §3 · p. 2
• Data aggregation suppresses redundant messages from sensors observing common phenomena, and signal-processing suppression is called data fusion.Source: §3 · p. 2

4. PROPOSED Z-SEP

• Z-SEP combines direct transmission with transmission through cluster heads as an extension of SEP.Normal nodes send directly to the base station, while nodes in the head zones use clustering.Source: §4 · p. 2, §4.2 · p. 3

4.1 Network Architecture:

• The network is divided into Zone 0 and Head zones 1 and 2 according to node energy and Y-coordinate.Normal nodes occupy Zone 0; advance nodes are split between the two head zones, positioned at the distant corners of the field.Source: §4.1 · pp. 2–3

4.2 Z-SEP Operation

• Normal nodes in Zone 0 send data directly to the base station, while advance nodes in Head zones 1 and 2 form clusters for transmission.Cluster heads collect and aggregate member data before forwarding it to the base station.Source: §4.2 · pp. 3–4
• Cluster heads are elected using a random draw against a node-specific threshold, with a separate probability and threshold for advance nodes.The cluster-head election probability for advance nodes follows SEP.Source: §4.2 · pp. 3–4
• Nodes join a cluster based on received signal strength, then send data to the cluster head in assigned TDMA slots.Cluster heads aggregate the received data and transmit it to the base station.Source: §4.2 · p. 4
• Normal nodes do not become cluster heads because their lower energy and the head's member-data reception load could shorten the stability period.The protocol confines cluster formation to advance nodes in the head zones.Source: §4.2 · pp. 3, 5

• The simulation uses a 100 m × 100 m field, 100 nodes deployed in zones, a central base station, the first-order radio model, and MATLAB implementation.The paper says additional simulation settings are listed in Table 1.Source: §5 · p. 5
• Twenty percent of nodes are advanced, split evenly between Head zones 1 and 2, with one cluster head in each zone per round.With Popt = 0.1, the setup specifies two cluster heads per round.Source: §5 · p. 5
• Table 1 lists simulation parameters, including data-aggregation energy and transmission/receiving energy values.The supplied parameter passage also names short- and long-distance amplification energy.Source: Table 1 · p. 5, §5 · p. 6

6. RESULT AND DISCUSSION

• In Fig. 5, Z-SEP showed greater stability than LEACH and SEP; normal nodes in Zone 0 communicate directly with the base station, avoiding cluster-head receiving and aggregation costs.The passage attributes LEACH’s faster node deaths to its sensitivity to heterogeneity.Source: §6 · p. 6, Figure 5 · p. 6
• In Fig. 6, Z-SEP throughput was far better than LEACH and SEP because every normal node sends data directly to the base station, while only cluster heads do so in LEACH and SEP.Source: §6 · p. 7
• With m=0.1 and α=2, Z-SEP’s stability period was almost the same as for m=0.2 and α=1, while extra advanced-node energy increased network lifetime.The discussion says LEACH stability decreases because equal cluster-head chances can cause normal nodes to die sooner than advanced nodes.Source: §6 · pp. 7–8, Figure 7 · p. 7
• With m=0.1 and α=2, Z-SEP throughput remained greater than LEACH and SEP despite the increased advanced-node energy.Source: §6 · pp. 7–8, Figure 8 · p. 8
• Z-SEP reached 1584 stability rounds and 2.26×10^5 packets, versus SEP’s 1150 rounds/4.02×10^4 packets and LEACH’s 899 rounds/2.44×10^4 packets.The comparison reports averages; Table 2 and Table 3 cover the two settings.Source: §6 · p. 8, Table 2 · p. 8, Table 3 · p. 8
• Z-SEP’s network lifetime was 5966 rounds, versus 5583 for LEACH and 5078 for SEP; the discussion says it is lower than LEACH’s but higher than SEP’s.Source: §6 · p. 8, Table 2 · p. 8, Table 3 · p. 8

7. CONCLUSION

• Z-SEP divides the field into Zone 0, Head Zone 1, and Head Zone 2 for a two-level heterogeneous network.Source: §7 · p. 9
• Normal nodes are placed only in Zone 0 and send data directly to the base station; advanced nodes are split between the two head zones and use clustering.Source: §7 · p. 9
• The paper reports an approximately 50% stability-period increase and higher throughput than LEACH and SEP.Source: §7 · p. 9