Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1998-06-09
2001-08-07
Pham, Chi (Department: 2631)
Pulse or digital communications
Transceivers
Modems
C375S225000
Reexamination Certificate
active
06272169
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to modems and more particularly to software modems that are implemented in microprocessors and that use information about the computing environment to determine the most appropriate data transfer rate.
2. Description of the Relevant Art
As the performance of microprocessors has increased, so have the opportunities to develop software applications. The software applications that have been developed to take advantage of these opportunities have included not only what might be considered more traditional applications, but also applications which emulate or take over functions traditionally implemented in hardware. By taking advantage of the extra processing power, software implementations can reduce the cost of the modem components in computing systems.
A modem is one example of computer system component which can be implemented in software. Software modems may provide various advantages over hardware modems. Software designs may be more easily changed than hardware designs. Likewise, it may be easier to update the software designs and to provide the updates to users. Modem applications may, however, present complications which do not arise from other types of applications. For instance, modem applications must operate in real-time and must operate under particular latency constraints with respect to the analog converter which is used to interface with the telephone line. Further, modem applications generally require a large portion of the processing time available in the system. Therefore, in a heavily loaded system, modem applications may worsen the loading situation by increasing the number of applications and devices competing for scarce system resources.
When a connection is established between a pair of modems, the modems must agree upon a protocol which will be used as the basis for transmitting and interpreting data between them. The modems first negotiate with each other to choose a modem technology within which to operate. This technology is normally the most recent technology which is common to both modems. A given technology generally allows operation within a discrete range of bit rates. Prior art software modems select one of these bit rates based only upon the quality of the telephone line on which the modem connection is established. The higher rates are used when the conditions on the telephone line are good and less fault tolerance is required and the lower rates are used when line conditions are poor and the modem connection needs to be more fault tolerant. Once the technology and bit rate are established, the modems can begin transmitting data.
SUMMARY OF THE INVENTION
The present invention provides a means and method for a modem to select a data transfer protocol based at least in part on conditions of the computing environment. The invention can therefore adapt its operation to more heavily loaded systems while avoiding failure of the connection and unwanted artifacts or behavior which may result from the heavy loading. Certain graphic-intensive applications, for example, may exhibit jerky behavior rather than smooth, continuous motions.
The invention includes means for a modem to monitor the system processing load (referring generally to information on the computing environment such as microprocessor loading and latency characteristics.) Using this information, the modem can select technologies and bit rates which are appropriate for current and anticipated system loading. The modem can determine system loading from measurements of microprocessor utilization in interrupt context, latency of the background scheduler mechanism or microprocessor utilization in process level context. If the system processing load is high, the modem can select a technology which requires less system resources than the most recent common technology, or it can select a bit rate which places less demands on the system than the highest bit rate allowable given a particular technology and certain line characteristics.
REFERENCES:
patent: 4965641 (1990-10-01), Blackwell et al.
patent: 5910970 (1999-06-01), Lu
Glaskowsky, “Soft Take Cheap Shot at DSPs: “Host Signal Processing” May Supplant DSPs in PCs and Consumer Devices,” Microprocessor Report, Dec. 9, 1996, pp. 10-11.
Blalock, “Microprocessors Outperform DSPs 2:1: Unpredictable Execution, Poor Tools Complicate Use in Real-Time Applications,” Microprocessor Report, Dec. 30, 1996, pp. 12-15.
Boswell, Jr. Charles Ray
Cole Terry Lynn
Kaplowitz David Mason
Advanced Micro Devices , Inc.
Conley Rose & Tayon PC
Kivlin B. Noäl
Pham Chi
Phu Phuong
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