Media access control protocol with priority and contention-free intervals

In a network of stations interconnected by a transmission medium, a method of carrier sense multiple access (CSMA) communication in which a plurality of stations desiring to transmit a frame may contend for access to the medium during a contention period, the method characterized by

• including a contention control field in at least some transmitted frames, the contention control field including contention control information indicating whether stations have permission to contend during a following contention period;
• having a first station establish a contention-free access interval for transmission of a plurality of frames, wherein the contention-free access interval is established by
• having the first station contend for access during a contention period and successfully gain access to the medium,
• transmitting the plurality of frames with contention control information that informs at least some other stations that they are not permitted to contend during contention periods within the contention-free access interval;
• having at least a second station that receives the transmitted frames determine from the contention control information whether the second station is permitted to contend during a contention period within the contention-free access interval,
• wherein if the contention control information indicates a contention-free access, determining if a channel access priority level associated with the frame to be transmitted by the second station is higher than a channel access priority level associated with a last transmitted frame, and further comprising:
• if the contention control information indicates a contention-free status and the channel access priority level associated with the frame to be transmitted is determined to be higher than the channel access priority level of the last transmitted frame, or the contention control information does not indicate a contention-free status, detecting whether any station in the network of stations intends to contend for access to the medium at a channel access priority level that is higher than the channel access priority level associated with the frame to be transmitted,
• wherein detecting whether any station in the network of stations intends to contend for access to the medium at a channel access priority level that is higher than the channel access priority level associated with the frame to be transmitted occurs in a priority resolution period immediately prior to the contention period and wherein detecting whether any station in the network of stations intends to contend for access to the medium at a channel access priority level that is higher than the channel access priority level associated with the frame to be transmitted comprises:
• detecting signaling from at least one other station during the priority resolution period, the detected signaling indicating a channel access priority level of a frame to be transmitted by the at least one other station.