Wireless Sensor Network (WSN) is deployed in number of scenarios and in most cases, the data collection rate and the reliability of the data collected plays the crucial role. The key application scenario of wireless sensor networks is data gathering: sensor nodes transmit data, possibly in a multi-hop fashion, to an information sink. The performance of sensor networks is thus characterized by the rate at which information can be aggregated to the sink. A number of techniques are concerned so far using realistic simulation models to address the speed of data collection. One technique is by considering TDMA scheduling on a single channel, reducing the original problem to minimizing the number of time slots needed to schedule each link of the aggregation tree.