MULTIPLE ACCESS PROTOCOL FOR ULTRALOW POWERED DEVICES

摘要

The invention is related to scheduling communication in a system comprising:- communicating devices (D#0, D#1, ... , D#n) having a power battery and being configured for awaking in view to receive/transmit data within a predefined timeslot dedicated to said each device, and then going to a sleep mode so as to save battery power,- and a cell controller (CC) transmitting repetitively a beacon to the communicating devices to announce to the devices whether future timeslots are intended or not to be allocated to said devices, and eventually moments when said future timeslots are scheduled to be allocated,The cell controller, before sending a current beacon, calculates, for each device a maximum time offset Max(t) supported by the device, taking into account the energy consumption due to go-to-sleep and wake-up phases until the moment when the device can use its timeslot. It ranks further a first list of devices intended to have a dedicated timeslot indicated in the current beacon, according to their maximum supported time offset Max(t). It picks the device at the head of the list and inserts it at the end. It calculates, for this device, a time offset tbetween a moment when the current beacon is transmitted and the moment when the dedicated timeslot is allocated and determines whether the time offset tof this device is greater than its maximum supported time offset Max(t,). If yes, it moves the device (D#n) upper in the first list, and determines a new time offset tfor this device. Finally, the current beacon is corrected according to the updated list data, and especially the device has its new time offset t.