Access network over a dedicated medium

Details Access network over a dedicated medium Access network over a dedicated medium

1997-06-04

2001-09-25

Olms, Douglas (Department: 2661)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S401000, C370S351000

Reexamination Certificate

active

06295293

ABSTRACT:

TECHNICAL FIELD
This invention relates to a network terminal and an IP based access network. The network node provides instant access to a multitude of communication services such as telephony, video, data, multi media as well as services provided by Internet . In the access network IP is used as the multiplexing and transport technique. The speed at which data is transported on the access line is limited by the transmission technique used not by the restrictions posed by the general public switched telephone network PSTN.
BACKGROUND
The traditional access to PSTN is a copper wire network with an individual two wire copper line, referred to as access line or subscriber line, for each subscriber. The access line supports 3.1 kHz telephony and is terminated in a local office, or in a remote switch group. As a physical medium the copper pair can support much higher bandwidths, but traditional local offices can only support 64 kb/s, or multiples thereof, stream services. ISDN (Integrated Services Digital Network) is using the same type of copper line, but uses a DSL (Digital Subscriber Line) modulation technique, which provides 144 kb/s (2B+D). However, ISDN requires an entirely new network solution.
The traditional method to access Internet from a subscriber's home is to use a dialed up connection to a modem pool of an Internet server. The connection is set up in the PSTN. Over the connection information is exchanged in IP packets (packets using the Internet Protocol suit). At the subscriber's end of the access line a telephone and a PC (Personal Computer) is connected to a modem. The modem is used to provide for transmission of digital data. Due to restrictions posed by PSTN the bit rates at which the modem can transmit and receive data is limited to about 30 kb/s.
This known method to access Internet is slow, it takes up to 30 seconds to set up the connection. Once the connection is set up, its bandwidth is often utilized very poorly due to the bursty nature of the IP traffic. Also the transmission of large amounts of data, in particular graphic information such as a WWW page, is slow due to the limited bandwidth provided by the modem to modem connection on top of the digital 64 kb/s connection. Further, when the connection has been set up no incoming calls can be received and no outgoing calls can be placed.
From a network point of view the above method to access Internet has a serious problem. The PSTN network has been dimensioned by assuming certain characteristics of the traffic, among other things a certain mean value of the traffic on subscriber/access lines, and a certain mean value of the duration of calls. PSTN is a concentrating network, and the number of outgoing trunks from a local office may be as low as one fourth of the subscriber/access lines. Internet access via dialed up modem connections usually have a quite different traffic pattern. For example the duration of calls are much longer than the mean value for ordinary telephone calls, a fact that would call for redimensioning of the switched telephone network if Internet access over PSTN becomes very frequent.
Subscribers which have been provided ISDN can access Internet over one or two B-channels. If one B-channel is used for Internet access, the subscriber can still receive incoming telephone calls on the other. This known access method, however, has the same negative consequences for the network dimensioning as the dialed up modem method.
There is a rapid development on the copper access technology field. Compare ADSL Forum, General Introduction to Copper Access Technologies (Available at http.//www.adsl.com/general
13
tutorial.html). A number of different modem technologies are being developed, such as VDSL (Very high bit rate Digital Subscriber Line) which provides 20 Mb/s in both directions over a copper pair up to a copper pair length of a few hundred meters. ADSL (Asymmetric Digital Subscriber Line) provides 1,5-9 Mb/s downstream and at least 16-640 kb/s upstream depending on the length of the copper pair length. However these technologies assume that the PSTN access should be provided as before and that a frequency band above the one used for PSTN access shall be used for data communication.
The recent development of the PSTN (ISDN) access network includes the standard interfaces V5.1 and V5.2 between local offices and access networks. These standards permit the introduction of access nodes which are connected to the local office.
Access nodes can also be connected to PSTN by a digital PABX (Private Automatic Branch Exchange) interface and to ISDN by a PRI (Primary Rate Interface). The V5 interfaces, the PRI interface and the PABX interface provide only 64 Kb/s bearer services and multiples thereof.
A previously known technique which permits simultaneously an Internet session and a telephony session over the same telephone access line includes a DSVD modem.(Digital Simultaneous transmission of Voice and Data on a single line).
A new technique that for simultaneously an Internet session and a telephony session over the same telephone access line includes a telephone doubler arrangement described in
FIG. 1
below and in Swedish Patent Application No. 9602212-4.
The telephone doubler arrangement permits a user which is connected to an analogue telephone network to access an IP-based communication service and still be able to receive and answer incoming calls, and to place outgoing calls, while simultaneously surfing the Internet.
In
FIG. 1
the telephone doubler arrangement
1
is shown to be connected to PSTN
2
and to Internet
3
. At the user side a modem
4
is connected to PSTN
2
, to a standard analogue telephone
5
and to a PC
6
. The telephone doubler arrangement
1
comprises a modem pool
7
connected to PSTN
2
, to Internet
3
and to a telephony server
9
. The telephony server
9
is connected to PSTN
2
.
When a user A is connected to Internet
3
via a dialed up PSTN connection to the modem pool
7
the telephone
5
cannot be used. On his/her PC the user can still communicate with other PSTN users by using the connectivity and multiplexing capabilities of IP. The dialed up line can carry a multiplexed stream of IP packages of: (a) an Internet session and (b) a telephony call. Speech carrying IP packages are routed to/from the telephony server
9
to PSTN. Telephony control signals are exchanged between the telephony server
9
and a telephony application
10
which runs on the PC. If the PC has audio capabilities, symbolized by a headset
11
comprising earphones and a microphone, a user A can be engaged in speech conversations with other users connected to the PSTN or ISDN. The user has got a new, soft phone on the PC
6
.
Another new technique that allows for simultaneously an Internet session and a telephony session over the same telephone access line makes use of the telephone doubler principle described above complemented, at the user end, with an IP modem
12
as shown in FIG.
2
and in Swedish Patent Application No. 9604409-4. IP functionality, such as provided by the PC
6
in
FIG. 1
, has been integrated in the modem
12
and therefore the modem is referred to as an IP modem.
This arrangement makes possible a dialed up connection, using a standard analog telephone, or a telephony application on a PC, while simultaneously an Internet user is engaged in an Internet session over a PC connected to the same IP modem.
The arrangement shown in
FIG. 2
is similar to that of
FIG. 1. A
telephone doubler arrangement
1
is connected to PSTN and Internet and comprises the same units as in FIG.
1
.
Over a first IP link
13
between the IP modem and Internet
3
IP packets containing information relating to an Internet session are transported. Part of this link comprises a subscriber line
14
extending between the IP modem and PSTN. Over a second IP link
15
IP packets carrying digitized, compressed speech are transported to/from the telephony server and the modem pool. The telephony server creates a dynamic relation between the IP address of the IP modem and the

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