Review of fairness and graph coloring methods for data collection in wireless sensor networks

Data collection is the most basic application of sensor networks. Sensors are deployed in a given region of interest. They sense some physical phenomenon and store the readings. All the sensors send stored data to sink. Sink is a central node which may be connected to the Internet. Sensor nodes may use either CSMA/CA or TDMA at the MAC layer. TDMA prevents collisions. Packets need not be retransmitted. This results in energy-saving and reduction in data delivery delay. We have mainly focused on TDMA based scheduling schemes. TDMA scheduling schemes are aimed to meet one or more of the following objectives: (i) minimizing schedule length (ii) maximizing fairness (iii) minimizing Latency (iv) meeting deadlines (v) minimizing energy consumption. Existing literature covers a detailed survey of schemes aimed to minimize schedule lengths. In present work, we have surveyed some mechanisms trying to maximize fairness. Often scheduling problems are mapped to graph coloring problem. We have also surveyed methods of TDMA scheduling using graph coloring. For each category i.e. fairness and graph coloring, some open issues are also mentioned.