A key radio system decision to be made is whether a multisite system should be built using a Simulcast or Multicast approach.
There is some argument over the meaning of these terms but to keep it simple, Simulcast systems simultaneously transmit the same signal, on the same frequency, at the same time from different radio sites. This makes it easy for the user to roam from one tower site coverage area to the neighboring one, but the systems are more costly, more prone to self-interference and use up more frequency channels.
A multicast system will also transmit the same information simultaneously from different sites, but do so using a different frequency for each site. The operator or intelligence built into the radio will have to switch channels as the user moves from one area to the next.