Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1999-07-30
2004-04-20
Chin, Wellington (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S467000
Reexamination Certificate
active
06724780
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to telecommunications networks and, more particularly, to a method for reducing information error rates and increasing throughput of communication channels within telecommunication networks.
2. Description of the Related Art
The use of communication networks such as telephony networks and data communication networks (e.g., the Internet) by the general public to convey information has increased significantly in the past several years. The information is represented by analog and/or digital communication signals. A telephony network provides traditional telephony services (e.g., voice communications, facsimile communications, analog data) over such media as twisted metallic wire pairs (e.g., tip/ring pairs), coaxial cables, fiber optic cables, air, free space, and other media. The Public Switched Telephone Network (PSTN) is an established telephony network which is accessible to the general public. A data communication network is a network in which information signals are conveyed throughout the network in digital form. Examples of a data communication network include the public Internet and computer communication networks (e.g., corporate communication networks, educational communication networks, governmental communication networks).
Often, users of telephony networks, computer communication networks, and other communication networks gain access to such networks via local access networks such as a Digital Loop Carrier (DLC) system. An exemplary DLC system is shown in FIG.
1
. DLC
10
comprises Remote Terminal (RT)
28
connected to Local Digital Switch (LDS)
20
via communication link
26
. Communication signals are exchanged between LDS
20
and communication link
26
via interface
24
. LDS
20
is connected to PSTN
12
and Public Internet
14
via communication links
18
and
16
, respectively. Remote Terminal
28
is connected to user
1
(
34
) via communication link
30
and to user
2
(
36
) via communication link
32
. Users
1
and
2
thus have access to PSTN
12
, Public Internet
14
, and to each other. For the sake of clarity only two users are shown in FIG.
1
. In practice, DLC systems connect hundreds or even thousands of users. Moreover, an actual DLC system, such as the one shown in
FIG. 1
, may provide access to a variety of communication networks in addition to the ones shown.
Communication links
30
and
32
are currently implemented with metallic wires (i.e., tip/ring pairs) through which analog communication signals (e.g., voice, facsimile) are conveyed between the users (
30
,
32
) and Remote Terminal
28
. Communication links
30
and
32
, when implemented as metallic tip/ring pairs, are part of the well-known Plain Old Telephone Service (POTS) telephony system and such links are commonly referred to as POTS lines. POTS lines typically are able to convey analog communication signals within a limited bandwidth spanning the frequency range of 0-4 KHz, commonly referred to as Voice Frequencies (VF). The VF range is typically further band limited to a frequency range of 200-3400 Hz due to additional analog filtering by DLC
10
equipment.
Users who wish to communicate with data communication networks, such as the Public Internet, typically use modems to transmit and receive analog data signals over the POTS lines. The analog signals from communication links
30
and
32
are converted to digital signals by RT
28
and are conveyed over communication link
26
. The digital signals are processed in accordance with a protocol being followed by DLC
10
and are transferred to LDS
20
which transmits such digital signals to either PSTN
12
or Public Internet
14
via communication links
18
or
16
, respectively. A protocol is a set of rules and standards that govern the operation of the various equipment of a communication network such as a local access network so as to control, monitor, and/or manage communications between users of the same or different networks and also between equipment of the same or different networks. Part of the protocol information is referred to as signaling information which is used to initiate communication between users, monitor the channel through which information is being conveyed during user communications, and terminate communications between users. The signaling information is often generated by the various communication network equipment (e.g., RT
28
, LDS
20
).
Before users of the same or different networks can communicate with each other, the communication is established in accordance with the protocol. A communication is established when the system has allocated appropriate network resources (e.g., a communication channel) and has followed certain procedural steps defined by the protocol, to allow users to convey communication signals to each other within a communication network or different networks. The communication signals conveyed between users is referred to as user information. Examples of protocols used by local access networks (particularly in North America) include the well-known TR-303 Hybrid Signaling protocol and the TR-008 protocol.
Still referring to
FIG. 1
, LDS
20
also receives user information from either PSTN
12
or Public Internet
14
and transmits such information to RT
28
which converts the information to the proper analog signal for propagation through communication links
30
or
32
. The signaling information is extracted by RT
28
and the remaining user information is relayed to the users. It should also be noted that communication links
30
and
32
need not be analog POTS lines, but can be other communication links through which digital and/or analog communication signals are conveyed.
The user information conveyed through the various communication links of local access network
10
is packaged and structured in accordance with well-defined communication channel formats. An example of a communication channel format used in many local access networks and other communication networks is the well-known Digital Signal Zero (DS0) channel format. A DS0 channel is defined as a communication channel with an information capacity of 64 kbps (64,000 bits per second). Part of the information conveyed through the communication channels represents protocol information. Communication links can be also be formatted as per a Digital Signal One (DS1) structure. A DS1 contains 24 DS0 channels.
The digital signals conveyed between RT
28
and LDS
20
over communication link
26
are organized in a particular fashion dictated by the protocol being followed by the local access network.
Referring to
FIG. 2
, there is shown how digital signals are organized and conveyed over communication link
26
between LDS
20
and RT
28
as per the TR-303 Hybrid Signaling protocol. Communication link
26
is organized as a DS1. Typically, the analog signals from the users are sampled by RT
28
at a rate of 8000 samples per second. RT
28
converts each sample to an 8-bit word, which is then placed in a particular DS0 channel within the DS1 of communication link
26
. In particular, the digital signals are organized as frames
38
, with each frame being 125 &mgr;sec long (i.e., length of one sample). Each frame
38
comprises data for 24 DS0 channels
40
, where each DS0 channel contains the 8 bits of data representing a sample from a particular user, and a framing bit
43
used as an indicator for separating the frames. Thus, a DS1 can serve up to 24 separate users.
The TR-303 Hybrid Signaling protocol allows signaling information to be integrated with user information and both types of information are conveyed through the DS1. Such a technique of integrating user information with signaling information is commonly referred to as in-band signaling (or in-slot signaling). Still referring to
FIG. 2
, part of each user's information, and in particular, the least significant bit
42
of each DS0 channel of every sixth frame is discarded and replaced with a signaling bit that represents signaling information for that DS0 cha
Bhuyan Arupjyoti
Boyer Gerald R.
Brown Ronald Robert
Deichstetter Eric A.
Duffany Jeffrey Louis
Chin Wellington
Lucent Technologies INc.
Schultz William
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