The present document is a specification of the lower layers and the lower layer signalling system for the two-way satellite network variants defined by ETSI TS 101 545-3 [i.16]. The present document constitutes a complete specification of the lower layers for a transparent star satellite network, a transparent mesh overlay satellite network and a regenerative re-multiplexing satellite network. Also, components required for a satellite network with a TRANSEC system are included. The present document is normative for the consumer terminal profile in a transparent star satellite network as defined by ETSI TS 101 545-3 [i.16], and does also include normative components specific to the other terminal profiles and satellite network variants defined by ETSI TS 101 545-3 [i.16].