Method for acknowledging uplink frames transmitted from end devices (110, 111, 112) to server equipment in a communication system, the method being implemented by the server equipment, the method comprising the following steps for each said end device (110, 111, 112): - receiving from said end device (110, 111, 112) a message requesting registration with the server equipment; - allocating said end device (110, 111, 112) to a group and, in said group, to a subgroup; - obtaining an address to be used by said end device (110, 111, 112) for subsequently communicating, in the communication system, part of said address identifying said group, another part of said address identifying said subgroup and yet another part of said address identifying said end device (110, 111, 112) in said subgroup; - transmitting to said end device a registration-confirmation message, including the address obtained, as well as information representing an estimated instant of the next transmission of acknowledgement, referred to as mass acknowledgement, common to said group; and the method further comprising the following steps, for each group: - checking, for each subgroup in said group, whether an uplink frame has been received from each end device (110, 111, 112) allocated to said subgroup as from the transmission of the previous mass acknowledgement for said group; - constructing a mass acknowledgement wherein each subgroup of said group is associated with the same information acknowledging said uplink frames received from all the end devices (110, 111, 112) in said subgroup in the case of a positive check, and with the same information not acknowledging any uplink frame received from end devices (110, 111, 112) in said subgroup in the case of a negative check, the mass acknowledgement further including information representing an estimated instant of the next transmission of mass acknowledgement for said group; and - broadcasting the mass acknowledgement, and acknowledging in unicast mode the uplink frames received that have not been acknowledged by the mass acknowledgement. - receiving from said end device (110, 111, 112) a message requesting registration with the server equipment; - allocating said end device (110, 111, 112) to a group and, in said group, to a subgroup; - obtaining an address to be used by said end device (110, 111, 112) for subsequently communicating, in the communication system, part of said address identifying said group, another part of said address identifying said subgroup and yet another part of said address identifying said end device (110, 111, 112) in said subgroup; - transmitting to said end device a registration-confirmation message, including the address obtained, as well as information representing an estimated instant of the next transmission of acknowledgement, referred to as mass acknowledgement, common to said group; - checking, for each subgroup in said group, whether an uplink frame has been received from each end device (110, 111, 112) allocated to said subgroup as from the transmission of the previous mass acknowledgement for said group; - constructing a mass acknowledgement wherein each subgroup of said group is associated with the same information acknowledging said uplink frames received from all the end devices (110, 111, 112) in said subgroup in the case of a positive check, and with the same information not acknowledging any uplink frame received from end devices (110, 111, 112) in said subgroup in the case of a negative check, the mass acknowledgement further including information representing an estimated instant of the next transmission of mass acknowledgement for said group; and - broadcasting the mass acknowledgement, and acknowledging in unicast mode the uplink frames received that have not been acknowledged by the mass acknowledgement.