This paper investigates the communication range and interference range of millimeter-wave wireless personal area networks (WPAN) based on realistic system design. Firstly, the effective communication range of the millimeter-wave networks are calculated based on realistic physical (PHY) layer design and 60GHz channel obtained from actual measurements. Secondly, an interference model is developed to facilitate the analysis of the impact of interferer-to-victim range on the victim link performance. It is found that system with BPSK modulation is able to support use cases with higher number of portable devices within a 3m range, while system with 16QAM modulation is more suitable for fixed high speed data streaming devices within a shorter range of 1m. Also, the interferer-to-victim range that causes no interference in all conditions is found to be approximately 40m, while a 25m range causes a typical bit error rate (BER) degradation of 1-digit (e.g. BER = 10^-6 to 10^-5).