WLAN Adapter Software Processing Host CPU Load Management
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Solution Overview
Problem
The high processing requirements of wireless local area network (WLAN) adapters pose a significant load on the host microprocessor of personal computers, potentially impacting other applications, especially during peak loading conditions, making it challenging to implement MODEM functions without dedicated hardware.
Innovation Solution
The WLAN protocol's power save mode is utilized to defer packet reception and transmission until the host CPU is no longer heavily loaded, allowing the host processor to manage network packets through the polling mechanism, thereby minimizing processing load and enabling simultaneous operation with other desktop applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the host processor performs MODEM processing for WLAN communications, then the cost of wireless hardware is greatly reduced, but the processing load on the host processor increases significantly
Solution Approach 1:
The system uses periodic polling mechanisms where the host processor periodically checks for buffered packets at the access point rather than continuously processing incoming data. This allows the processor to operate in periodic bursts rather than continuous mode, reducing overall processing load while maintaining cost-effectiveness by using software-based MODEM functions.
Solution Approach 2:
The access point buffers incoming packets before the host processor needs to process them. This preliminary buffering action allows the processor to handle data at its own pace rather than being forced to process real-time incoming data streams, thereby reducing processing pressure while maintaining the low-cost software-based approach.
2Reliability
If the host processor processes all incoming packets in real-time, then packet delivery reliability is maintained, but other applications on the host processor are adversely affected during peak loading
Solution Approach 1:
The access point acts as an intermediary that buffers packets and manages their delivery timing. This mediator allows the host processor to process packets at controlled intervals rather than real-time, ensuring reliable delivery while reducing impact on other applications by decoupling the timing of packet arrival from packet processing.
Solution Approach 2:
The system dynamically adjusts packet processing timing based on host processor availability. Rather than rigid real-time processing, the system flexibly schedules packet processing when the processor is available, maintaining reliability through adaptive timing while minimizing impact on other dynamic applications.
3Reliability
If the mobile station remains in active state to receive packets continuously, then real-time packet reception is ensured, but power consumption increases
Solution Approach 1:
The mobile station uses periodic wake-up cycles instead of continuous active reception. It periodically wakes up to check for buffered packets at the access point and returns to sleep mode otherwise, ensuring packet reception reliability while dramatically reducing power consumption compared to continuous active state.
Solution Approach 2:
The access point performs preliminary packet buffering before the mobile station needs to retrieve them. This allows the mobile station to sleep knowing packets are already buffered and ready for retrieval during periodic wake-up cycles, ensuring reliable reception while minimizing active time and power consumption.
Data Source
AI summary
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.