Electrical computers and digital processing systems: multicomput – Remote data accessing
Reexamination Certificate
1998-07-10
2001-02-20
Faile, Andrew I. (Department: 2711)
Electrical computers and digital processing systems: multicomput
Remote data accessing
C348S014160, C348S014160, C370S447000, C379S090010, C379S093090
Reexamination Certificate
active
06192399
ABSTRACT:
BACKGROUND
This invention relates to communication of information, such as computer data or video, over unshielded twisted-wire pairs (UTP) such as those used for telephone communication within a building.
Referring to
FIG. 1
, in a typical situation in which a building
100
a
is coupled to a variety of external information systems, communication within the building may use different wiring networks. The information systems can include public switched telephone network (PSTN)
120
, television distribution system
124
and a data network
122
. Building
100
a
can be a single family dwelling or a multiple unit dwelling or office building.
PSTN
120
is coupled to building
100
a
with one or more UTP cables
121
. UTP cables
121
include wire pairs that each provides an outside telephone line to the building. Television distribution system
124
can be a cable or satellite television system which provides multiple channels of television signals over a broadband connection
125
, typically a coaxial cable.
Data network
122
, such as the Internet, is coupled to building
100
a
in one of several different ways, providing a high-speed connection (e.g., 1 Mb/s or higher rates). Data network
122
can be coupled through PSTN
120
, either using one or more UTP cables
121
to pass data back and forth to building
100
a
. For instance, the two wire pairs can carry data in a T1 or partial-T1 format in which those wire pairs are used exclusively for data. Alternatively, data network
122
can be coupled to building
100
over some UTP cables
121
using a digital subscriber loop (DSL) signaling technique in which the data communication is passed in a different frequency range than voice telephone communication passing over the same wires.
Data network
122
can also be coupled to building
100
a
through television distribution system
124
. For instance, bi-directional data communication can pass over a cable television distribution system concurrently with television programming.
In building
100
a
, UTP cables
121
terminate at a telephone interface
132
, such as a main wiring block. Similarly, broadband connection
125
terminates at a television interface
152
. Data network
122
is coupled to devices in building
100
a
through a data interface
142
. If data network
122
is coupled through PSTN
120
, data interface
142
provides an interface appropriate to the type of signaling used (e.g., T1, DSL). If data network
122
is coupled through television distribution system
124
, data interface
142
can be a cable modem coupled to broadband connection
125
through television interface
152
.
Within building
100
a
, separate networks are typically used for telephone, data, and television signals. A telephone wiring network
130
couples telephones
134
to telephone interface
132
and to PSTN
120
. If no telephone switching equipment is deployed in building
100
, telephone wiring network
130
and UTP cables
121
provide a continuous electrical path from each telephone
134
to telephone switch in PSTN
120
. Multiple telephones
134
can be connected to the same conductive path when they are extensions of the same telephone line.
A data wiring network
140
couples one or more computers
144
to data network
122
through data interface
142
. A common form of data wiring network used within building adheres to one of the Ethernet standards (IEEE STD 802.3, 802.12), such as 10BaseT, 10Base2, 100BaseT4, or 100VG.
In 10BaseT, each data communication paths consisting of two UTP coupling a computer
144
to data interface
142
. Communication is at a rate of 10 Mb/s. If more than one computer
144
is connected to data wiring network
140
, data wiring network
140
can include a hub (not shown) that is connected to data interface
142
and to each of the computers
144
. Each of the computers
144
includes a network interface controller (NIC) that provides an appropriate electrical interface to data wiring network
140
. According to the IEEE 802.3 standard, 10BaseT communication paths should be no longer than 330 feet without an intervening hub.
The two UTP which couple two communicating devices consist of one UTP for communication in each direction. The two UTP are not intended for simultaneous communication in both directions. There are however occasions when both devices inadvertently transmit at the same time.
In 10BaseT, a device should not transmit when it is receiving a signal from the other device. As a result, the circumstance where both sides transmit at once only occurs when each side begins a transmission before it receives the signal sent from the opposite end. This creates a condition called a “collision.”
When a collision occurs, each device is required to suspend its transmission and wait until they are not receiving a signal. After a period of quiet, each device can attempt to transmit again.
As a result, when a 10BaseT device is transmitting on its outbound wire pair, it must monitor the inbound wire pair only to determine whether or not the other end has sent a signal causing a collision. The device does not need to interpret the information sent in the signal causing the collision.
The signal transmitted by a device to send a binary data stream is a Manchester coding of the binary data stream. A Manchester coding of a data stream is a bi-level signal that has at least one transition per input bit. For 10 Mb/s data stream, the spectrum of the coded data stream extends approximately from 3 MHz to 15 MHz.
In 10Base2, a second 10 Mb/s IEEE 802.3 standard, data communication paths consist of a single transmission line, typically a coaxial cable (e.g., RG-58), coupling a computer
144
to data interface
142
. Data wiring network
140
can in this case be arranged in a star configuration or can be run in a daisy-chained arrangement coupling multiple computers
144
to data interface
142
. When a 10Base2 device applies signals to the transmission line, it uses a similar Manchester coding used in 10BaseT. The multiple 10Base2 devices receive signals from the same line.
In 10Base2, when two devices transmit at the same time causing a collision, the devices detect the collision by monitoring the DC level of the received signal. When one device transmits, it applies a DC offset to the transmission line. A second device can detect this offset, even while it is transmitting.
The IEEE standard calls for the same transmission levels for 10Base2 and 10BaseT, but the minimum receive level is lower by 6 dB for 10Base2 than for 10BaseT.
Circuitry for converting between the signaling used in the 10BaseT and the 10Base2 standards is available from many vendors. The circuitry is typically called a “media converter.” One integrated circuit media converter is a available from Level One Corp., the LXT906 integrated circuit.
In 100 BaseT4, a 100 Mb/s IEEE 802.3 (u) standard, communication is over four UTP. When transmitting, a device sends 33.3 Mb/s on each of three of the four UTP. When receiving, the device receives 33.3 Mb/s on three of the four UTP, including the UTP that it does not use for transmission. The UTP that is not used for transmission is used for collision detection as in the 10BaseT two wire pair standard. Each of the 33.3 Mb/s data stream is block coded resulting in a signal that does not have significant energy in the voice band and extends to approximately 25 MHz.
In 100VG, a 100 Mb/s IEEE 802.12 standard, communication is also over four UTP. When transmitting data, a device sends 25 Mb/s on each of the four UTP. Rather than relying on a collision detection approach, in 100VG, the hub grants permission to transmit to a single device at a time between data transmissions. A non-return-to-zero (NRZ) signaling approach is used to transmit data, resulting in the coded data extending to approximately 15 MHz.
Television wiring network
150
is a coaxial network (e.g., RG-6) which couples each television
154
through television interface
152
to television distribution system
124
. Television wiring network typically provides the same broadband signal t
Brown Reuben M.
Faile Andrew I.
Fish & Richardson P.C.
Inline Connections Corporation
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