Performance of an Impulse Radio-Ultra Wide Band (IR-UWB) transmission system largely depends on the characteristics of UWB pulses such as rise time, pulse width and pulse repetitive frequency (PRF). This paper studies the IR-UWB pulse generation using direct modulation method for low-power sensor network applications. Effect of important pulse properties on the output transmit spectrum is discussed in detail. A multi node transmission system consisting of IR- UWB transmitters, receivers and a propagation channel is developed. Effect of various parameters such as PRF and channel noise in a multi node transmission environment is discussed by means of analyzing bit error rate performance of the system.