Читать книгу Industry 4.0 Vision for the Supply of Energy and Materials - Группа авторов - Страница 64

The combination of scheduled- and contention-based techniques is adopted in the so-called hybrid MAC schemes. In this class of schemes, time is divided into two periods, and, based on the requirements, it cooperatively switches between contention- or scheduled-based techniques to serve both modes. During contention period, nodes access to the medium and utilize contention approaches to broadcast in a common broadcast frequency. Then, during schedule-based period, each node performs reliable unicast transmission. Random–distributed scheduling algorithms are exploited in base stations to allocate the schedule of each node. For IoT use cases, some hybrid schemes jointly integrate FDMA with contention-based protocols and TDMA. Several MAC protocols are proposed in the literature based on such hybrid schemes [203, 204].