Sleep mode and contention resolution within a common channel medium access method

• US 5,440,560 A
• Filed: 03/20/1992
• Issued: 08/08/1995
• Est. Priority Date: 12/24/1991
• Status: Expired due to Fees

• Current Assignee: Proxim Wireless Corporation
• Original Assignee: Chandos A. Rypinski
• Inventors: Rypinski, Chandos A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Patel, Ajit
• Application Number:
  US07/854,493
• Time in Patent Office: 1,236 Days
• Field of Search: 370/85.2, 370/95.3, 370/95.1, 370/104.1, 370/85.7, 370/94.1, 370/85.8, 455/53.1, 455/54.1, 455/343, 455/38.3, 455/222, 455/33.1, 455/33.2, 340/825.5, 340/825.08, 340/825.09
• US Class Current: 370/457
• CPC Class Codes: H04L 12/12 Arrangements for remote connection or disconnection of substations or of equipment thereof
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04W 52/0235 where the received signal is a power saving command
• CPC Class Codes: H04W 74/06 using polling
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method of sleep mode and contention resolution provides management of a sleep mode in stations and backup for resolution of contention on request for service messages. This reduces the possibility of excessively delayed access to infrastructure services by providing a backup non-contending POLL for service REQUESTs which are invoked at the Access-point Hub Controller upon indication of possible contention. A fast POLL of Stations registered to that Access-point is made in the following available time with a possibility of carry-over to the next access opportunity. The length of the POLL is minimized by addressing only "awake" Stations and omitting those in sleep mode. A slow POLL is used to transfer Stations in and out of sleep mode, and for other purposes.

Claims

1. A method for sleep mode control for a wireless data communication network that serves battery-powered portable stations having an active mode with full functional capability and a quiescent mode where function is minimized for the purpose of reducing quiescent power drain, and where said stations automatically switch between these modes in response to user needs, and where said data communication network uses a system with a plurality of wireless access-points controlled from a common processor, and having an access method based upon exchange of data messages to manage channel access, said messages including registration, polling and invitation-to-request-service messages, said method for sleep mode control comprising the steps of:

polling each station with periodic asynchronously-timed addressed messages to assign either an active state to be maintained until after the next periodic message is received, thereby enabling an addressed station to receive data transfer messages transmitted from the system, or to assign permission to be inactive for a period of time specified in that message and after which a further periodic message will be received to renew the instruction, thereby reducing power supply to the circuit functions in said addressed station until the indicated inactive time has expired;

transmitting a poll acknowledgement message from said addressed station to the system to confirm the active or inactive status to the system of that addressed station until the next poll; and

transmitting a poll acknowledgement message from said addressed station to the system to advise the system whenever that addressed station will become active for the purpose of initiating data transfer messages to the system.

2. The method of claim 1 further including the step of:

allowing station transition to the active state at any time by response to any invitation-to-request message, and permitting a station once becoming active to remain active until at least the next polling message from the system.

3. The method of claim 1 further including the step of:

providing said stations with communication adapter functions which include a fully functional active state and a minimum power drain quiescent state, which is switched to active state dependent upon a selective indication of impending need for communication depending upon the existence of certain commands or memory access functions on a bus, which are a subset of all commands that may appear on the bus.

4. A method for contention resolution for a wireless data communication network that serves battery-powered portable stations having an active mode with full functional capability and a quiescent mode where function is minimized for the purpose of reducing quiescent power drain, and where said stations automatically switch between these modes in response to user needs, and where said data communication network uses a system with a plurality of wireless access-points controlled from a common processor, and having an access method based upon exchange of data messages to manage channel access, said messages including registration, polling and invitation-to-request-service messages, said method for contention resolution comprising the steps of:

delaying system response following transmission of an invitation message for an interval of time equal to the longest possible request message and propagation delay;

initiating through an access-point one or more addressed invitation-to-request messages successively to those stations which are in active status and associated with that access-point, and excluding stations which are inactive or not associated with that access-point, whenever two or more stations respond simultaneously to an invitation to request service from the system, and where contention is indicated by the receipt of partially valid messages containing errors or by the presence of signal and absence of a correctly decoded message at the system; and

controlling the system to classify as invalid anything other than receipt of a valid data transmission containing a correctly marked message type, where after each addressed invitation-to-request message the system determines there is not a valid request message being received in the shortest possible time before sending a next addressed invitation-to-request message.

5. The method of claim 4 further including the step of:

controlling the system so that if few or no stations are active, currently inactive stations which were previously active are addressed with invitation-to-request messages in sequence or priority lower than that of currently active stations.

6. The method of claim 4 further including the step of:

controlling the system so that station contention is indicated by presence of a signal level which is detectably greater after the expected start time of the request message than it was immediately before the expected start time of the request message, and concurrently an absence of decode of a valid request message, and where absence of that difference in signal level is used to define the shortest possible wait for determining absence of response after an addressed invitation.

7. A method for sleep mode and contention resolution for a wireless data communication network that serves battery-powered portable stations having an active mode with full functional capability and a quiescent mode where function is minimized for the purpose of reducing quiescent power drain, and where said stations automatically switch between these modes in response to user needs, and where said data communication network uses a system with a plurality of wireless access-points controlled from a common processor, and having an access method based upon exchange of data messages to manage channel access, said messages including registration, polling and invitation-to-request-service messages, said method for sleep mode and contention resolution comprising the steps of:

polling each station with periodic asynchronously-timed addressed messages to assign either an active state to be maintained until after the next periodic message is received, thereby enabling an addressed station to receive data transfer messages transmitted from the system, or to assign permission to be inactive for a period of time specified in that message and after which a further periodic message will be received to renew the instruction, thereby reducing power supply to the circuit functions in said addressed station until the indicated inactive time has expired;

transmitting a poll acknowledgement message from said addressed station to the system to confirm the active or inactive status to the system of that addressed station until the next poll;

transmitting a poll acknowledgement message from said addressed station to the system to advise the system whenever that addressed station will become active for the purpose of initiating data transfer messages to the system;

controlling the system following transmission of an invitation-to-request message to wait an interval of time equal to the longest possible request message and propagation delay;

initiating through an access-point one or more addressed invitation-to-request messages successively to those stations which are in active status and associated with that access-point, and excluding stations which are inactive or not associated with that access-point, whenever two or more stations respond simultaneously to an invitation to request service from the system, and where contention is indicated by the receipt of partially valid messages containing errors or by the presence of signal and absence of a correctly decoded message at the system; and

controlling the system to classify as invalid anything other than receipt of a valid data transmission containing a correctly marked message type, where after each addressed invitation-to-request message the system determines there is not a valid request message being received in the shortest possible time before sending a next addressed invitation-to-request message.

8. The method of claim 7 further including the step of:

controlling the system so that if few or no stations are active, currently inactive stations which were active within the last several polls are addressed with invitation messages in sequence or priority lower than that of currently active stations.

9. The method of claim 7 further including the step of:

providing said stations with communication adapter functions which include a fully functional active state and a minimum power drain quiescent state, which is switched to active state dependent upon a selective indication of impending need for communication depending upon the existence of certain commands or memory access functions on a bus, which are a subset of all commands that may appear on the bus.

10. The method of claim 7 further including the step of:

controlling the system so that station contention is indicated by presence of a signal level which is detectably greater after the expected start time of the request message than it was immediately before the expected start time of the message request, and concurrently an absence of decode of a valid request message, and where absence of that difference in signal level is used to define the shortest possible wait for determining absence of response after an addressed invitation.