Multiplex communications – Duplex – Communication over free space
Reexamination Certificate
2000-06-27
2003-07-22
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Duplex
Communication over free space
C370S252000, C455S450000
Reexamination Certificate
active
06597668
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to communication systems and methods and more particularly to a system and method which provides for broadband information communication between processor-based systems through a centralized communication array using adaptive time division duplexing.
BACKGROUND OF THE INVENTION
In the past, information communication between processor-based systems, such as local area networks (LAN) and other general purpose computers, separated by significant physical distances has been an obstacle to integration of such systems. The choices available to bridge the physical gap between such systems have not only been limited, but have required undesirable tradeoffs in cost, performance, and reliability.
One group of historically available communication choices includes such solutions as the utilization of a standard public switch telephone network (PSTN) or multiplexing signals over an existing physical link to bridge the gap and provide information communication between the systems. Although such solutions are typically inexpensive to implement, they include numerous undesirable traits. Specifically, since these existing links are typically not designed for high speed data communication, they lack the bandwidth through which to communicate large amounts of data rapidly. As in-building LAN speeds increase to 100 Mbps, the local PSTN voice grade circuits even more markedly represent a choke point for broadband metropolitan area access and therefore are becoming a less and less desirable alternative. Furthermore, such connections lack the fault tolerance or reliability found in systems designed for reliable transmission of important processor-based system information.
Another historically available group of communication choices is found at the opposite end of the price spectrum than those mentioned above. This group includes such solutions as the utilization of a fibre optic ring or point to point microwave communication. These solutions are typically cost prohibitive for all but the larger users. The point to point systems require a dedicated system at each end of the communication link which lacks the ability to spread the cost of such systems over a plurality of users. Even if these systems were modifiable to be point-to-multipoint, to realize the economy of multiple system use of some system elements, the present point-to-point microwave systems would not provide broadband data services but rather traditional bearer services such as T
1
and DS
3
. Furthermore these systems typically provide a proprietary interface and therefore do not lend themselves to simple interfacing with a variety of general purpose processor-based systems.
Although a fibre optic ring provides economy if utilized by a plurality of systems, it must be physically coupled to such systems. As the cost of purchasing, placing, and maintaining such a ring is great, even the economy of multi-system utilization generally does not overcome the prohibitive cost of implementation.
A need therefore exists in the art of information communication for a communication system providing cost effective bridging of large physical distances between processor-based systems.
A further need exists in the art for a communication system providing high speed broadband information communication between processor-based systems.
A still further need exists in the art for a communication system and a method of operation which efficiently utilizes the available spectrum in order to provide optimized information throughput.
A need also exists in the art for a fault tolerant communication system providing reliable bridging of physical gaps between processor-based systems.
Additionally, a need exists in the art for a broadband communication system providing simple connectivity to a variety of processor-based systems and communication protocols, including general purpose computer systems and their standard communication protocols.
SUMMARY OF THE INVENTION
These and other objects, needs and desires are achieved by a system and method of communication in which a communication array (referred to herein as a hub), is centrally located to provide an air link to a plurality of physically separated subscriber processor-based systems, or other sources of communication such as voice communication, utilizing a communication device (referred to herein as a node, which together with the subscriber processor-based system is referred to herein as a remote system or subscriber system) of the present invention. Preferably, this central array may be physically coupled to an information communication backbone providing communication between air linked systems and physically linked systems. Furthermore, multiple ones of such system may be utilized to bridge large physical separation of systems by the intercommunication of multiple central arrays. Moreover, pervasive surface coverage may be provided by arranging a plurality of such communication arrays to provide a cellular like overlay pattern.
In a preferred embodiment, the communication spectrum utilized by the communication system is frequency division multiplexed (FDM) to provide multiple channels or carriers for simultaneous information communication to a plurality of subscribers. Moreover, a preferred embodiment subscriber system is adapted to be dynamically controllable to select between ones of the FDM carriers utilized by the communication system.
Preferably a carrier frequency in the millimeter wavelength (MM Wave) spectrum, such as 10 to 60 GHz, is used by the present invention. Such carrier frequencies are desirable in order to provide a communication bandwidth sufficient for the transmission of at least 30 Mbps through each defined FDM channel of approximately 10 MHz. However, it shall be appreciated that the concepts of the present invention are applicable to portions of the spectrum other than millimeter wavelengths. For example, the present invention is particularly well suited for use in lower frequency bands, such as those in the 300 MHz to 3 GHz range, where radiation of signals are not as confined to line-of-sight as those of the millimeter wavelength spectrum.
Time division multiplexing (TDM) is preferably utilized to provide multiple, seemingly simultaneous, communications on a single carrier channel. Here ones of the FDM channels are broken down into a predetermined number of discrete time slices (burst periods or timeslots) which form a frame. Each burst period may be utilized by a different subscriber so as to result in information communication contained in a single frame, having a number of TDM bursts, being directed to/from a number of subscribers over a single FDM channel.
Moreover, full duplexing may be synthesized on a single carrier channel by time division duplexing (TDD) through the use of burst periods like those used in TDM. Through TDD, Tx and Rx frames, each frame having one or more burst periods, are defined to provide communication in a particular direction at a predefined time. According to a most preferred embodiment, TDD of the present invention is adaptive (ATDD) to provide for dynamic sizing of the Tx and Rx frames. For example, allocation of burst periods to either a Tx frame or Rx frame may be based on the instantaneous traffic demands of the subscriber systems.
In a preferred embodiment, the central communication array or hub comprises a plurality of individual antenna elements, or other structure, for providing radiation of signals in predefined areas, or antenna beams, having subscriber systems deployed therein. Preferably, the hub is adapted to conduct simultaneous communication with multiple ones of the subscriber systems. Such simultaneous communications may be accomplished using a plurality of FDM channels wherein the channels themselves are sufficiently isolated to allow simultaneous communications at the hub. Additionally or alternatively, the hub may be adapted to provide isolation of FDM channels so as to allow their simultaneous use in communications. Accordingly, signals associated with a particular subscri
Foster Robert B.
McMeekin M. Sue
Schafer David C.
Duane Morris LLP
Harris Broadband Wireless Access, Inc.
Hsu Alpus H.
Nguyen Toan
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