# US 5,706,274 A · CSMA with dynamic persistence > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,706,274 A - Document ID: US5706274A - Status: Granted - Kind: A - Application number: 08/525,239 - Filed: 1995-09-07 - Granted: 1998-01-06 - Earliest claimed: 1995-09-07 - Assignees: Tetherless Access Ltd. (TAL) - Inventors: Dean A. Angelico; James A. Hayes - Web page: https://patentgrep.com/patent/US5706274A ## CPC - H04L 12/413: with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD] - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method and apparatus for dynamically determining the persistence value P at a node in a P-persistent CSMA wireless network by determining the number of nodes to which the given node has an established link and which have transmitted within a preceding period of time is provided. The preceding period of time is between 5-60 seconds, preferably approximately 10 seconds. The value of P is set to a value between 1/(0.5N+1) and 1/(2N+1), preferably approximately 1/(N+1). ## Claims ### Claim 1 A method for dynamically determining the persistence value P at a given node in a P-persistent CSMA wireless network, comprising the steps of: monitoring communications over said wireless network; determining a number N of nodes having transmitted within a preceding period of time prior to a request to transmit a given message at said given node; setting P to a value between 1/(0.5N+1) and 1/(2N+1); generating a random number at said given node; comparing said random number to P; and transmitting said given message from said given node if said random number is less than P, otherwise delaying at least a delay period of time before transmitting. ### Claim 2 (depends on 1) The method of claim 1 further comprising the steps of: transmitting to nodes on said wireless network to determine the existence of a two-way communication link; determining a number X of said N nodes in said wireless network having a two-way communication link with said given node; and setting said number N to X for setting said value of P. ### Claim 3 (depends on 1) The method of claim 1 wherein said preceding period of time is between 5 and 60 seconds. ### Claim 4 (depends on 3) The method of claim 3 wherein said preceding period is approximately 10 seconds. ### Claim 5 (depends on 1) The method of claim 1 wherein said value of P is set to 1/(N+1). ### Claim 6 (depends on 1) The method of claim 1 wherein said delay period of time is a slot time, said slot time comprising: a turn-around time equal to the longer of the time required for said node to switch from transmitting to receiving and the time required for said node to switch from receiving to transmitting, plus a one-way propagation delay between said given node and a most distant node determined to have a two-way communication link with said given node, plus a carrier detect time. ### Claim 7 (depends on 6) The method of claim 6 further comprising the step of varying said carrier detect time in accordance with the processing speed of said N nodes. ### Claim 8 (depends on 6) The method of claim 6 further comprising the step of adjusting said one-way propagation delay to a worst case value regardless of the distance of actual links. ### Claim 9 A method for dynamically determining the persistence value P at a given node in a P-persistent CSMA wireless network, comprising the steps of: monitoring communications over said wireless network; transmitting to nodes on said wireless network to determine the existence of a two-way communication link; determining a number X of said nodes in said wireless network having a two-way communication link with said given node; determining a number of N of said X nodes having transmitted within a preceding period of time between 5 and 60 seconds prior to a request to transmit a given message at said given node; setting P to a value between 1/(0.5N+1) and 1/(2N+1); generating a random number at said given node; comparing said random number to P; and transmitting said given message from said given node if said random number is less than P, otherwise delaying at least a delay period of time before transmitting. ### Claim 10 (depends on 9) The method of claim 9 wherein said value of P is set to 1/(N+1). ### Claim 11 An apparatus for dynamically determining the persistence value P at a given node in a P-persistent CSMA wireless network, comprising: means for monitoring communications over said wireless network; means for determining a number of N of nodes having transmitted within a preceding period of time prior to a request to transmit a given message at said given node; means for setting P to a value between 1/(0.5N+1 and 1/(2N+1); means for generating a random number at said given node; means for comparing said random number to P; and means for transmitting said given message from said given node if said random number is less than P, otherwise delaying at least a delay period of time before transmitting. ### Claim 12 (depends on 11) The apparatus of claim 11 further comprising: means for transmitting to nodes on said wireless network to determine the existence of a two-way communication link; means for determining a number X of said N nodes in said wireless network having a two-way communication link with said given node; and means for setting said number N to X for setting said value of P. ### Claim 13 (depends on 12) The apparatus of claim 12 wherein said preceding period of time is between 5 and 60 seconds. ### Claim 14 (depends on 13) The apparatus of claim 13 wherein said preceding period is approximately 10 seconds. ### Claim 15 (depends on 11) The apparatus of claim 11 wherein said value of P is set to 1/(N+1). ### Claim 16 (depends on 11) The apparatus of claim 11 wherein said delay period of time is a slot time, said slot time comprising: a turn-around time equal to the longer of the time required for said node to switch from transmitting to receiving and the time required for said node to switch from receiving to transmitting, plus a one-way propagation delay between said given node and a most distant node determined to have a two-way communication link with said given node, plus a carrier detect time. ### Claim 17 An apparatus for dynamically determining the persistence value P at a given node in a P-persistent CSMA wireless network, comprising: means for monitoring communications over said wireless network; means for transmitting to nodes on said wireless network to determine the existence of a two-way communication link; means for determining a number X of said nodes in said wireless network having a two-way communication link with said given node; means for determining a number of N of said X nodes having transmitted within a preceding period of time between 5 and 60 seconds prior to a request to transmit a given message at said given node; means for setting P to a value between 1/(0.5N+1) and 1/(2N+1); means for generating a random number at said given node; means for comparing said random number to P; and means for transmitting said given message from said given node if said random number is less than P, otherwise delaying at least a delay period of time before transmitting. ### Claim 18 (depends on 17) The apparatus of claim 17 wherein said value of P is set to 1/(N+1).