IJSRD - International Journal for Scientific Research & Development| Vol. 1, Issue 9, 2013 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 1955 I. INTRODUCTION A. Wireless sensor networks Efficient design, performance and implementation of wireless sensor networks have become a hot area of research in recent years, due to the vast potential of sensor networks to enable applications that connect the physical world to the virtual world. By networking large numbers of tiny sensor nodes, it is possible to obtain data about physical phenomena that was difficult or impossible to obtain in more conventional ways. In the coming years, as advances in micro-fabrication technology allow the cost of manufacturing sensor nodes to continue to drop, increasing deployments of wireless sensor networks are expected, with the networks eventually growing to large numbers of nodes. Potential applications for such large-scale wireless sensor networks exist in a variety of fields, including medical monitoring, environmental monitoring, surveillance, home security, military operations, and industrial machine monitoring. Fig. 1 Sensor nodes scattered in a sensor field And the Components of a single sensor node (Source [1]). B. Network model 1) The single hierarchy network model identical with the one of LEACH with assumptions as follow [21]: 2) All nodes are the same, static, and have enough computing capacity to support different MAC protocols and data processing. 3) The radio signal has identical energy attenuation in all directions, and the wireless channel is symmetric. 4) All nodes can communicate with each other and the sink in single hop mode. 5) All nodes can be aware of their own residual energy and adapt transmission power according to communication distances. 6) Sinks are static, and with enough power supply. 7) Each node transmits data at given time slot. The data sensed by adjacent nodes are correlative, so the cluster head can fuse the collective data. Fig. 2: Network Model C. Energy model Heinzelman et al. [1] used the first order radio model. To transmit a k-bit data to a distance d, the radio hardware energy consumption is: Where E elec is the factor of electronics energy consumption. ε fs and ε mp are identical to the ones in receiver. d 0 is the reference distance between transmitter and receiver, which is given by To receive a k-bit data, the radio expends: It is assumed that the sensed information is correlated, thus cluster-head can always aggregate the data gathered from its members into a single length-fixed packet. Cluster- head aggregates k-bit data from n members to expend: Where EDA is the factor of data aggregation Based on Heterogeneity and Electing Probability of Nodes Improvement in LEACH Zaki Anwer 1 Amandeep Kaur Brar 2 1, 2 Punjabi University, Patiala