The millimeter wave WLAN standard can be used for joint communication-radar by exploiting the waveform preamble as a radar pulse. The velocity estimation accuracy with this approach, however, is limited due to the short integration time. A physical increase in the radar pulse integration duration, however, leads to a decrease in the communication data rate. In this paper, a coprime-based pulse design approach for IEEE 802.11ad-based radar is proposed that uses only a few non-uniformly placed preambles to construct several virtual pulses for enhancing the velocity estimation accuracy/resolution as compared to the conventional approach without sacrificing the communication data rate. The simulation results demonstrate that the coprime-based virtual pulse design improves the velocity estimation resolution by a factor of about 60x at a vehicle separation distance of 10 m and by a factor of about 20x at a distance of 100 m, while simultaneously achieving 7 Gbps data rate.