Method for transmitting data and method for receiving data

A method for transmitting data to a parent node by one of a plurality of child nodes in a sensor network including the parent node and the plurality of child nodes, comprising:

• attempting occupation of a contention interval of a first period;
• transmitting reservation information that includes node identification information and size information of data to be transmitted to the parent node in the contention interval of the first period, when the child node occupies the contention interval of the first period;
• receiving control information that includes the node identification information and channel allocation information from the parent node in the control interval of the first period;
• maintaining a sleep mode of the first period from the receiving of the control information to a time when the first period ends;
• and
• transmitting first data to the parent node in a transmission interval of a second period according to the channel allocation information.