In terms of two-way radio, “Seamless Roaming” or “Cellular Roaming” refers to capability of a two-way radio and a multi-site base station network to maintain continuous and perceivably uninterrupted connection and communications to the network and call traffic.

This roaming facility allows the two-way radio device to autonomously travel throughout a multi-site network without base station connection or communication dropout, ensuring that a traveling two-way radio device maintains continuous connection to the multi-site network and continuous communications to other users on the network.

For “Seamless” Inter-base-site roaming or call handovers to occur, there must be a perceivably uninterrupted communication in any current voice or data communications during the handover process… thus handovers must occur in milli-seconds, ensuring the users can make and receive PTT group calls, duplex voice calls, send and receive SDS messages and establish and maintain a Packet Data session without any input or awareness to the user.

The TETRA ETSI Standard specifications has extensively defined the requirements for both Base Stations and mobile terminals to cater for cellular roaming in multiple scenarios, including “Type I Seamless Roaming”. The Air Interface techniques employed have been proven in both the GSM cellular phone technology and the TETRA technology for many years now. Seamless roaming in TETRA has been tested at high speed on European rail networks with trains travelling in excess of 300km/h.

TETRA’s seamless roaming functionality proves once again that it is the only true multi-vendor open standard for business or mission critical digital 2-way radio solution available today, providing uncompromising network reliability, availability and robustness, even on a multi-site network.