Method for handover between heterogeneous communications networks

A method of maintaining communication between a first unit and a second unit where said first unit is comprised of a geographically mobile unit, where said first unit includes a first protocol stack adapted to act between a first communications hardware used for communication via a first communications network and one or more first software components, and where said second unit includes a second protocol stack adapted to act between a second communications hardware used for communication via a second communications network and one or more second software components, characterised in that said first unit includes a first session layer which is adapted to act as an interface between said first protocol stack and said first software components;

• in that said second unit includes a second session layer which is adapted to act as an interface between said second protocol stack and said second software components;
• in that said first session layer indicates a first identity for said second unit and software components belonging thereto;
• in that said second session layer indicates a second identity for said first unit and software components belonging thereto;
• in that said first and said second session layers ensure between themselves that traffic belonging to respective sockets in said first software components are corresponded by traffic intended for respective software components and belonging to a unique socket in said second software components, and vice versa;
• in that said first unit includes one or more first communications hardware with associated drive routines adapted to different communications networks;
• in that in the event of said first unit switching from said first communications network to a third communications network said first session layer functions to maintain said communication by selecting necessary first communications hardware and drive routines for said third communications network;
• and in that said identities are retained during switching of communications networks on the part of said first unit.