Channel access method for powerline carrier based media access control protocol

A method of accessing a channel in a communication transceiver coupled to a communications channel in a network including a plurality of stations, said method comprising the steps of:

• dividing contention for access to said channel into one or more contention windows each contention window assigned a priority and subdivided into a plurality of backoff time slots;
• deferring zero or more contention windows until arrival of a contention window whose priority corresponds to the priority of a particular transmission;
• each station wishing to transmit, initializing a backoff counter with a backoff count equal to a random number of backoff time slots;
• decrementing said backoff counter while said channel is idle;
• and
• attempting to reserve said channel upon expiration of said backoff counter.

A carrier sense multiple access (CSMA) based communications system wherein transmissions are preceded by a contention phase during which one or more transmitters compete for access to a channel, comprising:

• means for establishing one or more contention windows, each contention window assigned a priority;
• means for dividing each contention window into a plurality of backoff time slots wherein detection of a carrier sense signal during a time slot potentially indicates that said channel is busy;
• backoff means adapted to count using a backoff timer a randomly selected backoff time equal to a multiple of said backoff time slots;
• and
• reservation means adapted to attempt reservation of said channel upon expiration of said backoff timer and to enable transmission upon successful reservation of said channel.

A communications transceiver for transmitting and receiving over a carrier sense multiple access (CSMA) frame based communications network wherein frame transmissions are separated by a contention interframe space (CIFS) during which one or more nodes compete for access to said network, comprising:

• a coupling circuit for generating a receive signal received over said network and for outputting a transmit signal onto said network;
• a transmitter adapted to modulate data to be transmitted in accordance with a modulation scheme so as to generate said transmit signal therefrom;
• a receiver adapted to demodulate said receive signal in accordance with said modulation scheme so as to generate a receive data signal therefrom and adapted to generate carrier sense signals including a fast carrier detect (FCD) signal having a high false alarm rate and predicting early on when a transmission may be starting and a carrier detect (CD) signal having a low false alarm rate and indicating that a transmission is starting;
• a media access control (MAC) comprising means adapted to;
• establish one or more contention windows wherein each contention window is assigned a priority and subdivided into a plurality of backoff time slots;
• defer zero or more contention windows until arrival of a contention window whose priority corresponds to the priority of a particular transmission;
• initialize a backoff counter with a backoff count equal to a random number of backoff time slots;
• decrement said backoff counter while said channel is idle;
• attempt to reserve said channel upon expiration of said backoff counter;
• transmit onto said channel upon successfully reserving said channel;
• and
• a processor adapted to control the operation of said transmitter, receiver and MAC and to provide an interface between said MAC and an external host.

A computer readable storage medium having a computer program embodied thereon for causing a suitably programmed system to access a channel in a carrier sense multiple access (CSMA) frame based communications system wherein frame transmissions are separated by a contention interframe space (CIFS) during which one or more transmitters compete for access to said channel by performing the following steps when such program is executed on said system:

• establishing one or more contention windows, wherein each contention window is assigned a priority and subdivided into a plurality of backoff time slots;
• deferring zero or more contention windows until arrival of a contention window whose priority corresponds to the priority of a particular transmission;
• initializing a backoff counter with a backoff count equal to a random number of backoff time slots;
• decrementing said backoff counter while said channel is idle;
• attempting to reserve said channel upon expiration of said backoff counter;
• and
• transmitting onto said channel upon successful reservation of said channel.

A method of accessing a communications channel in a network including a plurality of stations, said method comprising the steps of:

• establishing one or more contention windows in which said plurality of stations compete for access to said communications channel;
• assigning a different priority to each of said one or more contention windows;
• each station wishing to transmit, initializing a backoff counter with a backoff count equal to a random number of backoff time slots;
• waiting until the arrival of a contention window having a priority corresponding to the priority of transmission of a particular station and upon the arrival thereof decrementing said backoff counter while said channel is idle;
• and
• attempting to reserve said communications channel upon expiration of said backoff counter.

A method of accessing a communications channel in a network including a plurality of stations, said method comprising the steps of:

• establishing one or more contention windows during which said plurality of stations compete for access to said communications channel;
• assigning a priority to each of said one or more contention windows;
• each station wishing to transmit, initializing a backoff counter with a backoff count equal to a random number of backoff time slots;
• waiting until the arrival of a contention window having a priority corresponding to the priority of transmission of a particular station and upon the arrival thereof decrementing said backoff counter while said channel is idle;
• attempting to reserve said channel upon expiration of said backoff counter;
• and adjusting the size of a contention window as a function of a number of said plurality of stations contending for said communications channel in said contention window.

A method of accessing a communications channel in a power line carrier based network including a plurality of stations, said method comprising the steps of:

• establishing one or more contention windows in which said plurality of stations compete for access to said communications channel;
• assigning a different priority to each of said one or more contention windows;
• each station sensing said communication channel for the presence of carrier signal;
• each station wishing to transmit, selecting a random backoff time and initializing a backoff counter with said backoff time;
• each station waiting until the arrival of a contention window having a priority associated therewith corresponding to the priority of transmission of a particular station;
• within the contention window having matching priority, waiting a random backoff time;
• upon expiration of said backoff counter, attempting to reserve said communications channel;
• and
• suspending countdown of said backoff counter if presence of carrier signal is detected.

A method of accessing a communications channel in a network including a plurality of stations, said method comprising the steps of:

• establishing one or more contention windows in which said plurality of stations compete for access to said communications channel, each contention window corresponding to a different priority level;
• each station wishing to transmit, initializing a backoff counter with a backoff count equal to a random number of backoff time slots;
• waiting until the arrival of a contention window corresponding to a particular transmission priority, and upon the arrival thereof˜decrementing said backoff counter while said channel is idle;
• attempting to reserve said channel upon expiration of said backoff counter;
• declaring the existence of a hidden station after a predetermined number of failed attempts to reserve said communications channel;
• and in accordance therewith, increasing the width of said backoff time slot and repeating said steps of initializing, waiting and attempting to reserve said communications channel.

A method of accessing a communications channel in a network including a plurality of stations, said method comprising the steps of:

• segmenting a transmission session into a plurality of frames;
• establishing one or more contention windows in which said plurality of stations compete for access to said communications channel, each contention window corresponding to a different priority level;
• initializing a backoff counter with a backoff count equal to a random number of backoff time slots;
• waiting until the arrival of a contention window corresponding to a particular transmission priority and, upon the arrival thereof, decrementing said backoff counter while said channel is idle;
• attempting to reserve said channel, upon expiration of said backoff counter, for a duration sufficient to transmit said plurality of frames;
• transmitting said plurality of frames from a transmitting station to a receiving station;
• and
• said receiving station transmitting an acknowledgement (ACK) reply to said transmitting station containing a plurality of ACK bits, each ACK bit indicating whether one of said frames is to be retransmitted.

A method of accessing a network channel by a station, said method comprising the steps of:

• providing a fast carrier detect (FCD) signal generated by a receive circuit, said FCD signal having a high false alarm rate to predict the staff of packet transmissions from other stations on said channel;
• dividing contention for channel access into a plurality of N windows, each window corresponding to one of N priority levels, wherein N is a positive integer greater than zero, and wherein each window is further divided into a plurality of time slots, each time slot having a width of said FCD signal;
• and
• contending for access to said channel only during a window whose priority is less than or equal to that of a packet awaiting transmission.