Method and protocol for a medium access control layer for local area networks with multiple-priority traffic
View Patent ↗A Medium Access Control (“MAC”) Layer protocol and a method for contention resolution using the protocol is provided for networks with multiple priority traffic. The protocol is used where a physical layer connected to a transmission medium uses a carrier modulation scheme with multiple frequencies. Stations on the network that desire access to the transmission medium use a carrier modulation scheme with multiple frequencies. Stations that desire access simultaneously transmit a single frequency selected at random from a set of physical layer frequencies during an open-contention-interval. At the same time, the stations listen to a combined frequency signal and analyzes it for frequency content. The station whose own frequency matches the highest frequency signal in the combined signal gains access to a transmission medium. In the event of a collision, a restricted-contention-interval is used only for the colliding stations. The probability of successful contention resolution increases very rapidly using the restricted-contention-interval. By partitioning the set of frequencies in contiguous ranges, multiple priority classes can be used with the contention method and the MAC layer protocol.
1. In a network system with a plurality of stations, the plurality of stations having a medium access control layer above a physical layer, a method of providing multiple priority classes with a medium-access-control-layer protocol connecting the stations to a transmission medium, the method comprising the following steps:
selecting on a first station a signal frequency for a desired priority class from N-number of priority classes to be used for contending stations, wherein the N-number of priority classes are created by partitioning a set of signal frequencies available for the physical layer into M-number of partitions, wherein each partition includes a contiguous range of signal frequencies from the set of signal frequencies and each frequency in the contiguous range of signal frequencies represents a priority class;
broadcasting the selected signal frequency for the desired priority class in an intent-to-transmit-signal with a medium-access-control-layer protocol from the first station to other stations on the network during a medium access control protocol open-contention-interval;
receiving on the first station with the medium access control protocol a combined-contention-signal including a plurality of priority class intent-to-transmit-signals, wherein the combined contention signal is a superposition of a plurality of priority class intent-to-transmit-signals from others stations in the network system;
decoding a plurality of priority class intent-to-transmit-signal frequencies from the combined-contention-signal;
determining whether the first station has selected the highest signal frequency for the desired priority class from the plurality of priority class signal frequencies in the combined-contention-signal, and if so,
transmitting data from the first station to the transmission medium as data for the desired priority class.
2. A computer readable medium having stored therein instructions for a causing a central processing unit on a station to execute the method of claim 1 .
3. The method of claim 1 wherein the transmission medium is a coaxial cable.
4. The method of claim 1 further comprising:
determining whether the first station has selected the highest signal frequency for the desired priority class from the plurality of priority class signal frequencies in the combined-contention-signal, and if not,
waiting for a next medium access control protocol open-contention-interval before sending the selected signal frequency during the next medium-access-control-layer protocol open-contention-interval.
5. The method of claim 1 wherein each priority class includes at least two signal frequencies.
6. The method of claim 1 wherein a wherein a mix of priority classes during the open-contention interval represents at least one signal frequency from each of the priority classes.
7. The method of claim 1 wherein a mix of priority classes during the open-contention interval does not represent a signal frequency from each of the priority classes.
8. The method of claim 1 wherein the N-number of priority classes each include an equal number of signal frequencies.
9. The method of claim 1 wherein selected ones of the N-number of priority classes include X-number of signal frequencies and other selected ones of the N-number of priority classes include Y-number of signal frequencies, wherein X is not equal to Y.
10. The method of claim 1 wherein the N-number of priority classes is equal to the M-number of partitions.
11. The method of claim 1 wherein the step of determining whether the first station has selected the highest priority class signal frequency from the plurality of priority class signal frequencies in the combined-contention-signal includes determining whether the first station is the only station that has selected a priority class signal frequency with a highest frequency during the open-contention interval.
12. In a network system with a plurality of stations, the plurality of stations having a medium access control layer above a physical layer, a method of providing multiple priority classes with a medium-access-control-layer protocol connecting the stations to a transmission medium, the method comprising the following steps:
selecting on a first station a signal frequency for a highest priority class from N-number of priority classes to be used for contending stations, wherein the N-number of priority classes are created by partitioning a set of signal frequencies available for the physical layer into M-number of partitions, wherein each partition includes a contiguous range of signal frequencies from the set of signal frequencies and each frequency in the contiguous range of signal frequencies represents a priority class;
broadcasting the first signal frequency for the highest priority class in an intent-to-transmit-signal with a medium-access-control-layer protocol from the first station to other stations on the network during a medium access control protocol open-contention-interval;
receiving on the first station with the medium access control protocol a combined-contention-signal including a plurality of priority class intent-to-transmit-signals, wherein the combined contention signal is a superposition of a plurality of priority class intent-to-transmit-signals from others stations in the network system;
decoding a plurality of priority class intent-to-transmit-signal frequencies from the combined-contention-signal, wherein the plurality of priority class intent-to-transmit signal frequencies includes a plurality of signal frequencies for the highest priority class and a plurality of signal frequencies from selected ones of other priority classes;
determining whether the first station has selected the highest signal frequency for the highest priority class from a plurality of priority class signal frequencies in the combined-contention-signal for the highest priority class, and if so,
transmitting data from the first station to the transmission medium as data for the highest priority class.
13. A computer readable medium having stored therein instructions for a causing a central processing unit on a station to execute the method of claim 12 .
14. The method of claim 12 wherein the transmission medium is a coaxial cable.
15. The method of claim 12 wherein the highest priority class includes at least two signal frequencies.