In this paper we evaluate the system performance and capacity of single carrier ultra-wideband (UWB) networks over 60GHz wireless personal area network (WPAN) channel. Symbol error rate is derived for both single user and multiple access scenario with a general system capacity and performance evaluation approach based on moment generation function. System outage probability and network throughput performance are also studied. Based on the current IEEE 802.15.3 WPAN standard work, different transmission scenarios have been explored and the performances with RAKE reception has been obtained. The channel model is also based on the recent work of IEEE 802.15 WPAN group. Numerical results are given to illustrate the system performance.