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Clustering algorithms can balance the power consumption of energy constraint wireless sensor networks. This paper proposes a new clustering protocol called Mean Territorial Energy Based Clustering Protocol (MTEP) for randomly deployed wireless sensor networks. In MTEP, cluster heads are selected according to residual energy and location information of a node in current round as well as mean territorial energy and total base station distance of node’s corresponding cluster territory in previous round. Energy consumption in conventional protocols becomes unbalanced because of clusters having different lengths. Proposed MTEP protocol addresses this problem by setting thresholds on cluster length and node to cluster head distance for producing equal length clusters. Simulation results show that MTEP protocol extends network lifetime and stability with reduction in energy dissipation compared to other clustering protocols such as LEACH and REAC.

An infrastructure required for sensor consisting of sensing, computation, communication and power unit is provided by wireless sensor networks [

In this paper, we propose a Mean Territorial Energy Based Clustering Protocol (MTEP) for randomly deployed WSNs. MTEP rotates the role of being a cluster head among all nodes for uniform energy consumption of each node as that of LEACH. MTEP selects cluster heads according to the threshold consisting of the node’s residual energy; distance from base station; mean territorial energy and total base station distance of all nodes of corresponding cluster territory in previous round unlike LEACH which uses cluster head selection threshold having fixed probability of cluster head selection.

Traditionally, LEACH divides its operations into several rounds. Each round includes cluster head selection, cluster formation and steady state phase. During a cluster head selection phase, each round selects itself as cluster head according to threshold calculated by parameter p, where p is the desired percentage of cluster heads for entire network. Each node selects a random number between 0 and 1 and compares it with cluster head selection threshold. If selected number is less than threshold, then that node becomes a cluster head for current round r. In LEACH [^{th} node is given by

T ( i ) = { p / ( 1 − p ∗ ( r mod 1 / p ) ) if i ∈ G 0 otherwise (1)

where G is the set of nodes which are not selected as cluster heads in the last 1 P

rounds. In above threshold, p = k / N where k is the pre calculated expected number of clusters and N is the total number of nodes in entire network. In LEACH, each node has equal probability p for each cluster head selection process. As all nodes have different residual energies during different rounds, low energy nodes may die quickly compared with high energy nodes. Also all randomly deployed nodes posse uneven residual energy distribution. Condition of the whole network cannot be accurately represented by global average energy for large scale WSNs. Very few existing algorithms consider local energy of nodes in determining cluster heads. Energy can be saved by considering local node’s energy level in deciding probability of a node to become a cluster head. Therefore, in order to extend network lifetime, we propose the MTEP which calculates different probability p for different nodes according to nodes residual energy and distance to base station in current round as well as mean territorial energy and total base station distance of all nodes within a node’s corresponding cluster territory in previous round.

Let a node i is present in cluster a at round r − 1. If E c u r r e n t − i ( r − 1 ) is the residual energy of node i at round r − 1, n_{a} is the number of nodes in a cluster a at round r − 1, then mean territorial energy of node i at round r − 1 is given by,

E m t a − i ( r − 1 ) = ∑ i = 1 n a E c u r r e n t − i ( r − 1 ) n a (2)

We keep desired percentage of cluster heads to be p as that of LEACH. Cluster head selection probability for node i during current round r is given by,

p ( i ) = p ∗ E c u r r e n t − i ( r ) E m t a − i ( r − 1 ) ∗ d t o B S − i ( r ) d t o B S − t o t a l − a ( r − 1 ) (3)

where d t o B S − i ( r ) is the distance of node i to base station at round r and d t o B S − t o t a l − a ( r − 1 ) is the total distance of all nodes present in cluster a to base station at round r − 1. A node i selects itself as cluster head at round r according to following probability threshold.

T ( i ) = { p ( i ) 1 − p ( i ) ∗ ( r mod 1 p ( i ) ) if i ∈ G 0 , otherwise (4)

where G is the set of nodes which are not selected as cluster heads in last 1/p(i) rounds. Once a node i selects itself as cluster head, it broadcasts an advertisement message containing its id and spreading code to reduce inter cluster interference. Each node compares randomly generated number between 0 and 1 with threshold for cluster head selection mentioned above. Node work’s as a current round cluster head if generated number is less that the threshold. Once a node selects itself as a cluster head, it uses CSMA as a MAC protocol to broadcast an advertisement (ADV) message containing its ID, header to indicate it as an announcement message and a spreading code necessary to reduce inter cluster interference.

In this paper, a distributed cluster formation technique is used to produce equal length clusters. Let C_{l} is the length of each cluster given by,

C l = N K (5)

where N is the total number of nodes in the network and K is the number of cluster heads. As there are different number of cluster heads in each round, C_{l} is also different for different rounds. In primary cluster establishment phase, each node receives an advertisement message sent by all cluster heads and join cluster head nearest to it only if that cluster head has member nodes less than C_{l}. If selected cluster head has member nodes higher than C_{l} then normal nodes select it as temporary cluster head. Once temporary cluster formation phase is complete, a threshold on node’s distance to cluster head is calculated for final cluster establishment phase. If node j at a location (x_{j}, y_{j}) is the cluster head of node i at location (x_{i}, y_{i}) in temporary cluster establishment phase, then total distance between all nodes and their respective cluster heads is given by,

d t o t a l _ n t o C H = ∑ i = 1 N ∑ j = 1 k ( x i − x j ) 2 + ( y i − y j ) 2 (6)

For final cluster establishment phase, threshold on node to cluster head distance is given by,

d t h − n t o c h = ∑ i = 1 N ∑ j = 1 K ( x i − x j ) 2 + ( y i − y j ) 2 N / K (7)

In final cluster establishment phase, a node who selected temporary cluster head now finds new closest cluster head k which is at a distance less than d t h − n t o c h _{ }( d i t o k ≤ d t h _ n t o c h ) and have cluster length less than C_{l} (If C_{k}_{ }< C_{l}). If normal node is unable to find out such cluster head then it selects its nearest cluster head for data transmission.

In this section, performance of the proposed MTEP protocol is compared with other protocols such as LEACH and REAC using Matlab 7.8. In this test, we assume some initial conditions of network model as shown in

Other parameters such as energy required to run radio electronics (E_{elec}) and radio amplifier (E_{amp}), data aggregation energy (E_{DA}) are taken same as [

and MTEP protocols. From

FDN (First Dead Node), HDN (Half Dead Node) and LDN (Last Dead Node) are the number of rounds after which first node, 50% and 100% of nodes are died respectively.

Parameter | Value |
---|---|

Network size | 100 m × 100 m |

Node number | 100 |

Node distribution | Random |

Sink position | (50 m, 285 m) |

Initial energy/node | 0.5 J |

Dissipated energy of transmitter | 50 nJ/bit |

Data packet length | 800 bytes |

Control packet length | 25 bytes |

Initial probability of cluster head selection (p) | 0.01 |

REAC and MTEP protocols. From

observed that LEACH, REAC and MTEP transmit 1174, 1191 and 1373 packets to base station respectively which clearly shows higher throughput in case of MTEP than LEACH and REAC.

Ideally all packets sent by a sensor node are received at the sink successfully. But practically, some packets are lost due to noise, attenuation, interference and congestion etc.

20% | 40% | 80% | |
---|---|---|---|

LEACH | 767 | 874 | 1376 |

REAC | 999 | 1096 | 1568 |

MTEP | 1180 | 1484 | 2592 |

WSN is formed by sensor nodes and wireless communication between them. Network should have long lifetime, high energy efficiency and stability. MTEP protocol proposed in this paper provides improved cluster head selection method based on node’s residual energy and location information in current round as well as mean territorial energy and total distance to base station of node’s corresponding cluster territory in previous round. Proposed MTEP protocol sets threshold on cluster length and node to cluster head distance for obtaining equal length clusters. Simulation results show that proposed protocol achieves better performance in increasing network lifetime, prolonging stability period, throughput and reducing energy consumption as well as packet drop ratio compared with other protocols such as LEACH and REAC.

Gawade, R.D. and Nalbalwar, S.L. (2017) Mean Territorial Energy Based Clustering Protocol for Randomly Deployed Wireless Sensor Networks. Advances in Internet of Things, 7, 87-96. https://doi.org/10.4236/ait.2017.73006