Off-line broadband network interface

Details Off-line broadband network interface Off-line broadband network interface

2000-05-09

2004-07-06

Nguyen, Steven H. D (Department: 2739)

Multiplex communications

Communication techniques for information carried in plural...

Combining or distributing information via time channels

C375S332000, C375S240030, C704S230000

Reexamination Certificate

active

06760347

ABSTRACT:

CROSS REFERENCE TO MICROFICHE APPENDIX
Appendix A, which is a part of the present disclosure, is a microfiche appendix consisting of 2 sheets of microfiche having 114 frames. Microfiche appendix A includes a software program operable on a host processor in order to drive a hardware card shown in appendix B.
Appendix B, which is a part of the present disclosure, is a microfiche appendix consisting of one (1) sheet of microfiche having 26 frames. Microfiche appendix B includes circuit diagrams and chip design diagrams for an embodiment of the invention as implemented on a circuit board.
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
This and other embodiments are further described below.
BACKGROUND
1. Field of the Invention
This invention relates to receiving data from a physically shared medium in a network interface where a portion of the required signal processing is accomplished off-line, independent of receiving the data.
2. Background
Packet-switched communication networks are often used in the transmission of data over shared communication channels. Shared communication channels may exist on a variety of physical media such as copper twisted-pair, coaxial cable, power lines, optical cable, wireless RF (radio frequency) and wireless IR (infrared). A system that has found wide-spread commercial use is Ethernet. (see “Multipoint Data Communication System With Collision Detection,” U.S. Pat. No. 4,063,220, issued Dec. 13, 1977 to Metcalfe et al). A multiple-access technique is used in systems such as Ethernet to coordinate access among several stations contending for use of the shared channel. Ethernet is based on 1-persistent Carrier Sense Multiple Access with Collision Detect (CSMA/CD) using a collision resolution algorithm referred to as Binary Exponential Backoff (BEB).
A typical packet-switched network is shown in FIG.
1
. In
FIG. 1
, stations
102
,
104
,
105
and
106
are connected to a shared medium
101
. Although only four stations are shown in
FIG. 1
, any number of stations may be connected to shared-medium
101
. Shared medium
101
may be any of the variety of available physical media including copper twisted-pair, coaxial cable, power lines, optical cable and wireless (RF or IR).
Station
102
shows a network interface
103
. All of the stations connected to common shared medium
101
have a network interface similar to network interface
103
. Network interface
103
controls access to shared medium
101
from host station
102
and provides conversion between host station formatted data and data packets on shared medium
101
.
FIG. 2
shows a typical Ethernet network interface
210
installed in a host station
220
. See “Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specification,” ANSI/IEEE Std. 802.3, Fifth Edition Jul. 29, 1996. Ethernet network interface
210
is a typical network interface
103
(
FIG. 1
) providing access to shared medium
101
from host station
220
.
Typically, signal processing functions in network interface
210
are grouped into a physical (PHY) layer
200
and a Media Access Control (MAC) layer
201
. Physical layer
200
(the lowest level layer of the interface) interfaces to MAC layer
201
. Signals ReceiveBit (RB), TransmitBit (TB), collisionDetect (CD), and carrierSense (CS) are exchanged between PHY layer
200
and MAC layer
201
. Media access control (MAC) layer
201
implements an access control algorithm and translates between a sample packet bit stream output from PHY layer
200
and a host formatted data packet bit stream compatible with host station
220
.
In PHY layer
200
, a hybrid
209
couples both receive and transmit elements of PHY layer
200
to shared medium
101
. The receive elements include a CODEC/DEMOD
203
and a carrier sense
202
. CODEC/DEMOD
203
in conjunction with Carrier Sense
202
detects the presence of a transmission on shared medium
101
. Carrier sense
202
outputs the carrierSense (CS) signal indicating whether or not a data packet on shared medium
101
is detected. Further, CODEC/DEMOD
203
converts analog data packets received by hybrid
209
from shared medium
101
into the sample packet bit stream from PHY layer
200
. Typically, CODEC/DEMOD
203
includes a controlled gain amplifier, anti-aliasing and receive filters, and an analog to digital converter. The anti-aliasing and receive filters of CODEC/DEMOD
203
carry out the symbol processing required to counter the effect that channel distortion by shared medium
101
has on a received data packet. Therefore, a majority of the signal processing required to receive and process data packets from shared medium
101
is accomplished in real-time in CODEC/DEMOD
203
. CODEC/DEMOD
203
must be capable of processing data packets from shared medium
101
at the transmission rate of shared medium
101
. The output of CODEC/DEMOD
203
, the sample packet, is a nearly completely processed form of the received data packet and is substantially converted to host data format.
The transmit elements of PHY layer
200
include a CODEC/MOD
205
. CODEC/MOD
205
typically includes a controlled gain amplifier, a digital to analog converter and reconstruction filters. CODEC/MOD
205
converts an output bit stream into appropriate transmit data packets which are transmitted on shared medium
101
by Hybrid
209
. Collision detect
204
compares the transmit data packets being transmitted to received data packets to detect the presence of other transmissions from other stations. A data collision occurs when another station is transmitting a data packet during the time when station
210
attempts to transmit a data packet. Collision detect
204
generates the collisionDetect (CD) signal indicating whether or not a data collision has been detected.
Physical layer
200
outputs signal CD from collision detect
204
and signal CS from carrier sense
202
to MAC controller
206
in MAC layer
201
. PHY layer
200
also outputs the receiveBit (RB) signal to RX Queue
207
of MAC layer
201
and receives the transmitBit (TB) signal from TX Queue
208
of MAC layer
201
.
RX Queue
207
receives the sampled packet in a sequence of receiveBit (RB) signals from CODEC/DEMOD
203
. When the sample packet is complete and stored in RX Queue
207
, host processor
230
of station
220
is alerted and the sample packet is transmitted to processor
230
.
Buffer TX Queue
208
receives a transmit packet in sample packet format from processor
230
in station
220
. TX Queue
208
stores the transmit packet and, in response to a signal from MAC controller
206
, alerts CODEC/MOD
205
of the presence of the transmit packet. CODEC/MOD
205
receives the transmit packet from TX Queue
208
, converts the transmit packet to data packet format, and transmits the data packet to hybrid
209
for transfer to shared medium
101
. Both TX Queue
208
and RX Queue
207
hold data that is substantially in host data format and the signal processing required for receiving data from shared medium
101
or transmitting data to physical medium
101
is accomplished in CODEC/DEMOD
203
and CODEC/MOD
205
, respectively.
MAC controller
206
controls the timing of transmit data packets through TX Queue
208
to CODEC/MOD
205
of PHY
200
. MAC controller
206
outputs a controller signal to TX Queue
208
, the controller signal indicating to TX Queue
208
when it is desirable to transmit a data packet onto shared medium
101
.
Implementations of CODEC/DEMOD
203
and CODEC/MOD
205
depend on the signaling and modulation format used in shared medium
101
and are strongly dependent on the required system performance and the overall channel characteristics. An industry trend has been to use more sophisticated mo

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