Enhanced carrier sense multiple access (CSMA) protocols

摘要

Systems and methods for enhanced carrier sense multiple access (CSMA) protocols are described. In various implementations, these systems and methods may be applicable to Power Line Communications (PLC). For example, a method may include attempting to access a communications channel to transmit a frame after a backoff time proportional to a randomly generated number within a contention window (CW), the CW having an initial value carried over from a previous transmission of a different frame. Additionally or alternatively, some of techniques described herein may facilitate the spreading of the time over which devices attempt to transmit packets, thereby reducing the probability of collisions using, for example, Additive Decrease Multiplicative Increase (ADMI) mechanisms.

主权项

1. A method, comprising:
performing, by the communications device, attempting to access a communications channel to transmit a frame after a backoff time proportional to a randomly generated number (K) within a contention window (CW), the CW having an initial value carried over from a previous transmission of a different frame; in response to: (i) reaching a predetermined number of attempts without having obtained access to the communications channel, or (ii) having transmitted the frame over the communications channel upon the expiration of a backoff time without having received a corresponding acknowledgement,
increasing the CW by doubling the CW up to a value smaller than or equal to a maximum CW value, andattempting to access the communications channel to transmit or re-transmit the frame after another backoff time proportional to another K within the increased CW; anddoubling the maximum CW value in response to an average CW over a predetermined number of previous attempts to access the communications channel being greater than a first threshold; orhalving the maximum CW value in response to the average CW over the predetermined number of previous attempts to access the communications channel being smaller than a second threshold different from the first threshold.