Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1998-04-03
2001-06-05
Chin, Stephen (Department: 2634)
Pulse or digital communications
Transceivers
Modems
C375S220000, C375S140000, C370S311000, C455S432300
Reexamination Certificate
active
06243413
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to system and methods for providing modular home-networking communication and, more specifically, to a modular home network communications system which employs a common physical layer modulation and a common media access protocol which are compatible with disparate communication channels such as radio frequency (RF) and powerline communication channels, and a method for implementing the same.
2. Description of Related Art
Currently, one of the newest trends in the personal computer (PC) industry involves Home Networking. Specifically, the ability to inexpensively and reliably interconnect multiple computers, peripherals, and/or appliances within a home without having to install ethernet or twisted pair backbone wiring is a strongly desired goal for home networking device OEMs. In furtherance of this goal, both wireless solutions and powerline solutions have been considered as the physical layer backbone for the home network system.
Conventional powerline networks generally operate with data rates ranging from about 10 kbps to 350 kbps. For example, one such system, which is disclosed in U.S. Pat. No. 4,815,106 to Propp, et al. entitled “Powerline Communication Apparatus”, operates at a data rate of 100 kbps using a complicated equalizer/coding scheme. The disadvantage with this system, however, is its low data rate and its high implementation complexity which results in excessive costs. It has recently been determined that a 350 kbps powerline network system based on traditional frequency modulation (FM) methods such as binary frequency shift keying (BFSK) may be achieved. However, system performance will degrade as the data rate increases past 350 kbps in a time dispersive
oisy communication channel such as the powerline channel. Indeed, for applications such as remote printing and file sharing, it is desirable to operate with a data rate of at least 1 Mbps. Consequently, a modulation system for use in a powerline communication channel which is inexpensive and can easily be implemented, and which operates with a data rate in the range of 1 Mbps, is highly desirable.
Next, although conventional wireless network communication systems generally operate at a maximum data rate of around 2 Mbps in the 2.4 GHz ISM (Industrial, Scientific and Medical) frequency band, these systems can be very costly. Notwithstanding its potentially high cost, a wireless network communication system advantageously provide mobility to the network device and as such, may be the preferred network infrastructure if mobility is a priority for the end user.
In view of the advantages and disadvantages discussed above for both the wireless and powerline network solutions, it is not clear that one single solution, either wireless or powerline, will provide the optimum network technology to meet the need of a wide range of disparate users. Therefore, there currently exists a strong need in the PC home-networking industry to provide a versatile home-networking architecture using a common baseline technology which can support both powerline interconnect and wireless interconnect architecture, and which is inexpensive and easily implementable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a home-networking modulation system which is compatible with disparate communication channels such as the wireless and powerline physical layer communication medium.
It is another object of the present invention to provide a common home-networking modulation system which operates at a low signal to noise ratio and is robust to time dispersion distortion in both the RF and powerline environments.
It is yet another object of the present invention to provide a home-networking communications system which allows an end user to select either RF or powerline connectivity, or both, while using a common baseband processing unit and media access control protocol.
In one aspect of the present invention, a modular home-network communications system comprises: a network device; a plurality of channel interface units for operatively interfacing the network device to one of a plurality of disparate communication channels, each of the plurality of channel interface units being operatively compatible with a corresponding one of the plurality of disparate communication channels; modulation/demodulation means, operatively connected to one of the plurality of channel interface units, for encoding and decoding data transmitted between the network device and one of the plurality of disparate communication channels, the modulation/demodulation means being operatively compatible with each of the plurality of disparate communication channels; and media access protocol means, operatively connected between the network device and the modulation/demodulation means, for controlling the transfer of data between the network device and the modulation/demodulation means, the media access protocol means being operatively compatible with each of the plurality of disparate communication channels; whereby the network device may be interchangeably connected between each of the plurality of disparate communication channels by connecting the modulation/demodulation means to the corresponding one of the plurality of channel interface units.
The present invention is directed to a modular home-networking communication architecture which utilizes a common modulation system so that an end user is afforded the flexibility to configure the home network to simultaneously utilize a plurality of disparate communication channels (or easily switch between them) such as RF and/or powerline channels. Research performed by the present inventor has revealed that a direct-sequence spread-spectrum (DS-SS) modulation system will provide high-speed operation at a low signal to noise ratio with very good resistance to time dispersion distortion when the coding sequence used to spread information symbols (such as Barker codes) has sufficient autocorrelation properties. Consequently, by using the DS-SS based physical layer modulation, it is possible to provide a viable, high performance modular home-networking architecture which can support both wireless and powerline network devices.
Advantageously, the DS-SS modulation system is relatively inexpensive and simple to implement. The DS-SS modulation system may be used in the ISM band to provide a 2 Mbit data rate for wireless (RF) network connectivity. Furthermore, the present inventor has determined (through an analysis of the characteristics of the powerline channel) that the DS-SS modulation system is well adapted for use in the powerline channel, which is highly dispersive and noisy, since DS-SS can operate at a low signal to noise ratio and is robust to time dispersion distortion of signals transmitted on the powerline medium. Moreover, the DS-SS technology has proven to be capable of supporting a data rate of 1 Mbps over a typical powerline channel in a home environment. Equally important is that the DS-SS modulation system is particularly ideal for the powerline communication channel since it spreads the transmission power over a wide range of frequency, thereby lowering the power spectral density such that it will provide long distance coverage without violating FCC radiated emission and conducted power regulations.
REFERENCES:
patent: 5371734 (1994-12-01), Fischer
patent: 5504454 (1996-04-01), Daggett et al.
patent: 5633868 (1997-05-01), Baldwin et al.
patent: 5748619 (1998-05-01), Meier
patent: 5889816 (1999-03-01), Agrawal et al.
patent: 5960344 (1999-09-01), Mahany
Chin Stephen
F. Chau & Associates LLP
International Business Machines - Corporation
Liu Shuwang
LandOfFree
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