Cooperative MIMO in wireless sensor networks with mobile sensors for cooperativeness and data aggregation

Optimality in energy usage of sensors in wireless sensor network (WSN) is a very crucial matter. Long range communications in WSNs are affected by factors like fading of channel, interference and radio irregularity. Cooperative MIMO (Multiple Input Multiple Output) communication in WSNs proves helpful to solve these problems of long range transmission. In this paper we propose a cooperative MISO (Multiple Input Single Output) communication model (A variant of MIMO) with modified LEACH (Low-Energy Adaptive Clustering Hierarchy) protocol where a few mobile sensors (MS) using Alamouti diversity schemes take part in cooperative communication along with the normal sensors. A mobile sensor can move to a specific location of the field to take part in cooperative communication with other sensors. Normal sensors only sense the environment, gather the data, compress and take part in cooperative communication. Mobile sensors (usually do not sense) are responsible for cooperative transmission and reception and they have higher capacity in terms of battery power and communication range than the normal ones. This model of communication helps in achieving both uniform energy expenditures by the nodes and a good average lifetime for the network. By choosing some costly mobile sensors, this modified LEACH MISO model can avoid the problems of energy expenditure in cooperative node selection as well as nonuniformity in sensors death. This model helps in long range communication where many intermediate communication takes place before reaching the base station e.g., WSN in border security navigation, forest river bank for intrusion detection etc. Simulation results demonstrate the working strategy of the proposed model and show how this model can overpower any existing LEACH based MIMO model by avoiding some disadvantages of LEACH protocol.