Ultra WideBand (UWB) transmissions are attractive for low power, baseband asynchronous multiple access and peer-to-peer wireless communications. Multiple Input Multiple Output (MIMO) technology is useful in combating against multipath and at the same time improves system performance by using multielement antennas at both transmitter and receiver.This letter proposes a time hopping M-ary UWB systems using V-BLAST algorithm, and power control is considered for better performance. Simulations are provided to compare performance with different antennas.