Cable modem system using CATV transmission path

Details Cable modem system using CATV transmission path Cable modem system using CATV transmission path

1999-12-21

2004-03-23

Williams, Kimberly A. (Department: 2611)

Interactive video distribution systems

Video distribution system with upstream communication

Having link to external network

C725S119000, C725S122000

Reexamination Certificate

active

06711742

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cable modem system and, more particularly, to a cable modem system for performing data communication by utilizing cable television (CATV) transmission path.
2. Description of the Related Art
In the cable television network, broadcasting signals are transmitted from a CATV station to each subscriber via a trunk line and a branch line. The trunk line may be a multistage tree type or a multistage star type. Since the trunk line and the branch lines are used to transmit the wide-band broadcasting signals, coaxial cables and optical fiber cables are chiefly used for the trunk line and the branch lines. Accordingly, the CATV system has a superior wide-band transmission ability.
Recently, Internet has been rapidly widespread. As a result, it is concerned to the broad-band transmission ability with an excellent CATV system. The preparation to use CATV transmission path as an access network of Internet is being advanced. Especially, standardization is being advanced by using CATV transmission path as for the cable modem system to connect the subscriber to Internet by a LAN interface. The telco return method and the 2-way method have been standardized.
In the 2-way method, the CATV transmission path is used for both the down-link to transmit signals from the CATV station to the subscriber side and the up-link to transmit signals from the subscriber side to the CATV station. Detail of the specification of the 2-way method is described in “Data-Over-Cable Service Interface Specifications, Radio Frequency Interface Specification SP-RFI-I04-980724”.
In the telco return method, the CATV transmission path is used for the down-link and the public switch telephone network (PSTN) is used for the up-link. Detail of the specification of the telco return method is described in “Data-Over-Cable Service Interface Specifications, Cable Modem Telephony Return Interface Specification SP-CMTRI-I01-970804.
A description will now be given, with reference to
FIGS. 1 and 2
, of the 2-way method and the telco return method.
FIG. 1
is a structural diagram of a cable modem system using the 2-way method.
FIG. 2
is a structural diagram of a cable modem system using the telco return method.
The cable modem system shown in
FIG. 1
comprises a CATV station
10
, a CATV transmission path
20
and a subscriber unit
30
. The CATV station
10
comprises a cable modem termination system (CMTS)
11
connected to the CATV transmission path
20
and a router
14
connected to Internet.
The CATV transmission path
20
includes a coaxial cable and an amplifier for amplifying attenuated RF signals. An optical fiber cable may be used together with the coaxial cable depending on the transmission distance. The subscriber unit
30
includes a cable modem (CM)
31
and a terminal unit
35
such as a personal computer which supports a standard Internet protocol TCP/IP. The terminal unit
35
is connected to the CATV transmission path
20
via the cable modem
31
.
When the subscriber connects the terminal unit
35
to Internet, the Internet protocol (IP) packet output from the terminal unit
35
is supplied to a LAN end terminal
33
of the cable modem
31
via the LAN. The cable modem
31
converts the supplied IP packet into a multiple frame of the time division multiplexer access (TDMA) method. Thereafter, the multiple frame is digitally modulated to an RF signal by an up-link RF end terminal
32
, and the RF signal is output to the CATV transmission path
20
.
The RF signal output to the CATV transmission path
20
is supplied to the cable modem termination system
11
of the CATV station
10
. The RF signal is then digitally demodulated by an up-link RF end terminal
12
, and the multiple frame is disassembled so as to reproduce the original IP packet. The cable modem termination system
11
sends the original IP packet to Internet via the router
14
.
On the other hand, an IP packet supplied from Internet is supplied to the cable modem termination system
11
via the router
14
. The cable modem termination system
11
converts the supplied IP packet into a multiple frame of a time division multiplex (TDM) method. The multiple frame is digitally modulated to an RF signal by a down-link RF end terminal
13
, and is output to the CATV transmission path
20
. The RF signal output to the CATV transmission path
20
is supplied to the cable modem
31
of the subscriber. The RF signal is digitally demodulated by a down-link RF end terminal
34
, and the multiple frame is disassembled so as to reproduce the original IP packet. The original IP packet is supplied to the terminal unit
35
via the LAN.
The cable modem system using the telco return method shown in
FIG. 2
comprises the CATV station
10
, the CATV transmission path
20
, the subscriber
30
and a public service telephone network (PSTN)
40
. In
FIG. 2
, parts that are the same as the parts shown in
FIG. 1
are given the same reference numerals, and descriptions thereof will be omitted.
The CATV station
10
includes the cable modem termination system
11
, the router
41
and a telco remote access concentrator (TRAC)
15
which is connected to the public service telephone network
40
.
When the subscriber connects the terminal unit
35
to Internet, the cable modem
31
is activated by turning on a power switch. The down-link RF end terminal
34
of the cable modem
31
searches for an RF signal which is supplied from the CATV station
10
via the CATV transmission path
20
which serves as a down-link to the CATV center
10
so as to receive a dial number, a user name and a password that are necessary for the connection to Internet.
Then, a telco return end terminal
37
included in the cable modem
31
sends a call to the public service telephone network
40
by using the received dial number so as to establish a communication line to a line end functional unit
16
of the telco remote access concentrator
15
.
After the communication line is established, a link is established in accordance with the point-to-point protocol (PPP) which is a standard Internet protocol for a serial connection. At this time, the user name and the password received by the down-link RF end terminal
34
of the cable modem
31
are used for attestation. By this attestation, it can be determined whether or not the subscriber is an authorized user by determining whether or not the user name has been registered.
Thereafter, the IP packet output from the terminal unit
35
is supplied to the LAN end terminal
33
of the cable modem
31
via the LAN. The IP packet is converted into an encapsulated signal in accordance with the point-to-point protocol by the telco return protocol unit
17
. The encapsulated signal is supplied to a telco return end terminal
37
, and is modulated to a modem signal of V.34. The modem signal is supplied to the telco remote access concentrator
15
via the public service telephone network
40
.
The line end functional unit
16
of the telco remote access concentrator
15
demodulates the supplied modem signal. Thereafter, the telco return protocol unit
17
removes the encapsulation by the protocol so as to reproduce the original IP packet. The telco remote access concentrator
15
sends the reproduced IP packet to Internet via the cable modem termination system
11
and the router
14
. On the other hand, the IP packet supplied by Internet is supplied to the terminal unit
35
via the CATV transmission path
20
in the same manner as that of the 2-way method.
The telco return method described with reference to
FIG. 2
uses a public service telephone network for the up-link. However, a public personal handyphone system (PHS) network
50
may be used as shown in
FIG. 3
, or a private PHS network may be used as shown in FIG.
4
.
The cable modem system using the telco return method shown in
FIG. 3
uses the public PHS network for the up-link. Accordingly, the CATV station
10
is provided with a terminal adapter (TA)
18
which is compatible with the PHS Internet access

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