LAN connection using analog modems via telephone wiring

Details LAN connection using analog modems via telephone wiring LAN connection using analog modems via telephone wiring

1998-12-08

2001-05-29

Chan, Wing F. (Department: 2643)

Telephonic communications

Telephone line or system combined with diverse electrical...

Having transmission of a digital message signal over a...

C379S090010, C370S445000

Reexamination Certificate

active

06240166

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention relates to a computer communication system and more particularly to a modem communication system where modems communicate across standard telephone lines within a premises using frequency division multiplexing.
2. Description of the Related Art
Modem communication over telephone lines has gained widespread usage with the growing number of multi-media applications implemented using personal computers. Personal computers (PCs) now perform many different types of data transfers over telephone lines, such as accessing the “Internet,” communicating data files between PCs, sending and receiving facsimiles, and acting as an answering machine by sending and receiving voice information over the telephone lines. Modems are used to convert between a computer's digital signals and analog signals that can be carried on the telephone network's analog transmission lines.
Traditionally, at the core of a modem, is a digital signal processor (DSP) integrated circuit (IC), a memory, a codec, and a data access arrangement (DAA). A codec includes a digital to analog converter (D/A) and an analog to digital converter (A/D). The modem is typically coupled to a host computer bus through standard bus interface circuitry to thereby interact with a host computer. The host computer includes a central processing unit (CPU) that generates data that is to be transmitted through the modem and to receive data that is passed through the modem.
DSP based modems generally operate by processing a relatively small number of samples from the input A/D converter and generating a similarly small number of samples to be output through the D/A converter. These systems are said to work on a “sample by sample” basis or a “symbol by symbol” basis, depending on the particular implementation. Such schemes have the benefit of minimal latency time, since the input is processed almost immediately. These schemes, however, require very high computing power which is typically provided by a dedicated DSP.
In recent years, modems have been developed that operate using DSPs implemented in software. However, although software DSPs enable sampling rates to substantially increase without a corresponding increase in hardware expenses, these software DSPs operate similar to standard hardware DSPs by sampling and transmitting signals at or slightly above the “voice band”. The voice band is approximately 4 kHz and has been recognized as the voice band because telephone lines typically operate with exchange circuitry, e.g., a central office or private branch exchange (PBX), configured with low pass circuitry that cuts off signals that have been transmitted at frequencies above the voice band. Thus, modem signals are typically transmitted in the voice band and DSPs sample the signals at a minimal frequency rate, i.e., twice the rate of the highest freqency of the signal being sampled, or the “Nyquist rate”.
SUMMARY OF THE INVENTION
A communication system according to the present invention includes a first communication device having a first digital signal processor and a first codec and a second communication device having a second digital signal processor and a second codec. The second communication device is communicatively coupled with the first communication device via a communication channel. The first digital signal processor enables frequency division multiplexed sampling of signals from the first codec, and the second digital signal processor enables receipt of the division multiplexed sampling of signals from the first digital signal processor such that the sampling of signals is transmitted to the second codec in a manner so as not to interfere with other communications of the first communication device.
Of particular note, the communication system sometimes creates the communication channel with a telephone wire network that has no exchange circuitry and is completely within a premises. Often, the first communication device and the second communication device each comprise a voice band modem. The communication system also allows the first communication device to communicatively couple with at least one external communication device via another communications channel. In this embodiment, the first communication device communicates with the at least one external communication device transparently to the communications between the first communication device and the second communication device.
In other embodiments, the communication system allows the first communication device to communicate with the second communication device outside of the voice band. The communication system could also include a first processor associated with the first communication device such that the first processor influences, via the communication channel, operation of peripheral devices that are coupled to a second processor associated with the second communication device.
With the communication system herein described, a user can communicate between a first and a second computer system. The first computer system has a first voice-band modem and the second computer system has a second voice-band modem, the first voice-band modem and the second voice-band modem communicatively coupled across a telephone line network. The user communicates between the computer systems by configuring the first voice band modem to transmit and receive signals at frequencies both within and without the voice band, configuring the second voice band modem to transmit and receive signals at frequencies both within and without the voice band, transmitting signals from the first computer system to the second computer system across the telephone line network at a frequency outside of the voice band without interfering with voice band communications of the first computer system, and receiving, from the telephone line network, signals at the second computer system at the frequency outside of the voice band without interfering with voice band communications of the second computer system.
In addition, the user can communicate between systems by transmitting signals from the second computer system to the first computer system across the telephone line network at a frequency outside of the voice band without interfering with voice band communications of the second computer system, and receiving, from the telephone line network, signals at the first computer system at the frequency outside of the voice band without interfering with voice band communications of the first computer system. Further, the user communicates by controlling, with the first computer system and through communications across the telephone line network, peripheral devices attached to the second computer system, the communications passing transparently to other communications on the telephone line network.
In another embodiment according to principles of the present invention, a communication system includes a first voice band modem; a second voice band modem; a telephone wire network within a premises and without exchange circuitry within the premises. The first voice band modem is communicatively coupled to the second voice band modem via the telephone wire network such that the first voice band modem communicates, outside of the voice band, with the second voice band modem.
In the communication system, the first voice band modem may be communicatively coupled across another telephone wire network to another communication device for voice band communications. In addition, communication signals between the first voice band modem and the second voice band modem are multiplexed in the frequency domain as well as communication signals between the first voice band modem and an external communication device being multiplexed in the frequency domain. In addition, the first voice band modem often communicates with an external communication device that is communicatively coupled to the first voice band modem on a communication network external to the telephone wire network within the premises, the communication occurring transparently to the communications be

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