Recently there has been a great interest in how to apply Long Term Evolution (LTE) in Professional Mobile Radio (PMR) context, which is used for public safety work. However, LTE is not yet optimized for low bit rate voice communication. The smallest LTE packet size is still too large in case that low bit rate voice communication is transmitted in high quality channel. This is one of the main challenges for effectively applying LTE in PMR context. Therefore, this paper presents a new architecture for Multi-users Multiplexing Radio Voice Transmission for enhancing voice capacity over LTE in PMR Context. This architecture allows reducing the difference between the LTE packet size and voice payload by multiplexing voice packets from different users into one same LTE packet in the downlink transmission. In this architecture, the multiplexing size can be modified according to the Modulation and Coding Scheme (MCS), the payload of users and the LTE bandwidth. Our simulation results show that in the best case, our proposed method can achieve a gain up to 650 % in the voice capacity gain as compared to the standard LTE