We propose a statistical multiplexing-based hybrid frequency-hopping orthogonal frequency-division multiple-access (HFH-OFDMA) system to increase the downlink user capacity of orthogonal frequency-division multiplexing (OFDM)-based ultra-wideband (UWB) indoor radio access networks (RANs). The downlink user capacity is here defined as the maximum allowable number of users served with a given data rate in a piconet. Statistical multiplexing, as noted by Walrand and Varaiya in 2000, is a method in which multiple users with intermittent transmissions efficiently share a link. The adoption of a statistical multiplexing concept enables the HFH-OFDMA system to accommodate many more users than the conventional FH-OFDMA system can. In OFDM-based UWB indoor RANs, the downlink user capacity of the HFH-OFDMA system is limited by either the total number of available subcarriers in a piconet (resource-limited) or the FCC UWB emission limit (power-limited). We analyze the downlink user capacity of the proposed HFH-OFDMA system in both single-piconet and multipiconet environments. In the single-piconet environment, the proposed HFH-OFDMA system which operates in 3.168-3.696-GHz band accommodates 256 users with a data rate of 532.5 kb/s in an OFDM-based UWB indoor RAN, while the proposed HFH-OFDMA system in the multipiconet environment, under the same conditions of the single-piconet environment, accommodates 110 users with a data rate of 532.5 kb/s.