Method for Mitigating Adverse Processor Loading in a Personal Computer Implementation of a Wireless Local Area Network Adapter
A personal computer's (PC) microprocessor is used to provide both the physical layer (PHY) and media access control (MAC) processing functions required to implement a wireless local area network (WLAN) adapter. This technique uses the polling mechanism associated with the power save (PS) functionality of WLAN protocol to relieve networking stress on the host processing system. It does this while maintaining networking integrity and packet delivery. The WLAN protocol polling mechanism is used to briefly inhibit the transfer of packets from the WLAN access point (AP) during peak periods of network traffic and/or host processor loading. Because the modulation, demodulation, and MAC functions, typically implemented in dedicated hardware on existing adapters are implemented in software running on the host PC microprocessor, other host system processes and applications can interfere with these time critical functions. Conversely, latency introduced by WLAN specific processing tasks during peak periods of network traffic may cause unacceptable delays to the other processes and applications requiring microprocessor attention. In addition to its primary stated purpose of allowing WLAN mobile stations to save power, this technique will use power save polling as a method for controlling delivery of network packets when the host is heavily loaded or when peak interrupt latencies make reliable packet delivery difficult or impossible.
1 . A method for reducing CPU loading in a software based receiver for a packet based communications system comprising the steps of:
measuring the current CPU load,
determining that the CPU load has exceeded a predetermined threshold,
signaling the communications system transmitter to inhibit packet transmission when the threshold is exceeded,
monitoring the CPU load while the transmitter is inhibited,
determining that the CPU load has fallen below a predetermined threshold, and
signaling the communications system transmitter to begin transmitting packets once the CPU load has fallen below the predetermined threshold.
2 . A method as in claim 1 , wherein the measurement of CPU loading is made by an operating system background task.
3 . A method as in claim 1 , wherein the CPU load measurement is based on the response time of the host CPU to a request for interrupt.
4 . A method as in claim 1 , wherein the transmitter signaling is done through a power save mode.
5 . A method as in claim 1 , in which the communications system is wireless.
6 . A method as in claim 1 , in which the communications system is IEEE 802.11 wireless local area network (WLAN).
7 . A method as in claim 1 , in which the communications system is Bluetooth.
8 . A method as in claim 1 , in which the communications system is IEEE 802.15 wireless personal area network (PAN).
9 . A method for reducing CPU loading in a software based receiver for a packet based communications system comprising the steps of:
measuring the current packet traffic loading,
determining that the traffic load has exceeded a predetermined threshold,
signaling the communications system transmitter to inhibit packet transmission when the threshold is exceeded,
monitoring the traffic load while the transmitter is inhibited,
determining that the traffic load has fallen below a predetermined threshold, and
signaling the communications system transmitter to begin transmitting packets once the traffic load has fallen below the predetermined threshold.
10 . A method as in claim 9 wherein the traffic load is measured using packet reception rate.
11 . A method as in claim 9 , in which the communications system is wireless.
12 . A method as in claim 9 , in which the communications system is IEEE 802.11 wireless local area network (WLAN).
13 . A method as in claim 9 , in which the communications system is Bluetooth
14 . A method as in claim 9 , in which the communications system is IEEE 802.15 wireless personal area network (PAN).