Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
2000-04-11
2002-06-11
Woo, Stella (Department: 2684)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S090010, C379S093280
Reexamination Certificate
active
06404861
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a system which provides access to a high-speed connection. In particular, the present invention is directed to a modem using digital subscriber line (DSL) technology to facilitate the transfer of voice and data.
2. Background Art
As the information age matures, it is enabled by a number of technological advances, such as the geometric growth of networked computing power and the prevalence of reliable and ubiquitous transmission media. Today's consumers in both the residential and business arena have been acclimated to a more graphical approach to communication. In particular, multimedia applications (which include textual, graphical, image, video, voice and audio information) have become increasingly popular and find usage in science, business, and entertainment. Local area networks (LANs) are essential to the productivity of the modern workplace; Ethernet-type networks have dominated the LAN market and have been continually enhanced (e.g., switched Ethernet, Fast Ethernet, and/or Gigabit Ethernet) to keep pace with the bandwidth intensive multimedia applications.
A compelling example of the growth of information consumption is the dramatic increase in users of the World Wide Web, a multimedia-based information service provided via the Internet. Although initially a forum for academia to exchange ideas captured in ASCII text, the Internet has developed to become a global media for users from all walks of life. These Internet users regularly exchange multimedia graphical, image, video, voice and audio information as well as text.
Furthermore, the business world has come to realize tremendous value in encouraging workers to telecommute. To avoid the idle commuting time, today's workers enjoy the convenience of working from home via their personal computers. As illustrated in Figure, a user at a remote site
101
(e.g., home) has traditionally been able to access her/his office
119
, which includes accessing an office local area network
119
b
(LAN), through a dial-up connection over a 33 Kbps or 56 Kbps modem
101
b
. The dial-up connection is handled by a telephone central office (CO)
105
through a voice switch
107
, which switches the “data” call through a public switched telephone network (PSTN)
111
. The data call terminates in a remote CO
121
at a voice switch
123
. The voice switch
123
switches the call to the subscriber; in this case, the called line is associated with a modem in a modem pool
119
a
. Once connected to the modem pool
119
a
, the end user at her/his remote site
101
can access the computing resources in his office
119
. These sources include a multimedia server
119
c
and a PC
119
d
of the remote user. A similar connection to Internet
115
by a user at a remote site
101
can be accomplished by connecting to an Internet Service Provider (ISP)
117
instead of modem pool
119
c.
Unfortunately, telecommuting from a remote office or accessing multimedia information from home over the Internet imposes an enormous strain on networking resources. It is common knowledge that the networking infrastructure is the bottleneck to the expedient transfer of information, especially bandwidth intensive multimedia data. As alluded to before, today's access methods are limited to standard analog modems, such as
101
b
, which have a maximum throughput of 56 Kbps on a clean line (i.e., a line not having any appreciable noise causing errors in bit rate transfer). Remote users may alternatively acquire basic rate (
2
B+D) Integrated Services Digital Network (ISDN) services at 128 kbps. Even at this speed, telecommuters may quickly grow impatient with slow response times as compared to the throughput of their LANs to which they have grown accustomed. On average, a typical Ethernet user can expect to achieve approximately 1 Mbps on a shared 10Base-T Ethernet LAN and up to 9+ Mbps in a full duplex switched Ethernet environment. In addition, Internet users are also demanding greater access speeds to cope with the various multimedia applications that are continually being developed. Fortunately, the communication industry has recognized the escalating demand.
Cell switching technology, such as Asynchronous Transfer Mode (ATM), was developed in part because of the need to provide a high-speed backbone network for the transport of various types of traffic, including voice, data, image, and video. An ATM network
113
is typically able to provide bandwidths to an ATM user at approximately 1.5 Mbps on a T1 line, 44.7 Mbps on a T3 line, and 155 Mbps over a fiber optic OC-3c line. Consequently, ATM networks are suitable to transport multimedia information.
ATM further provides a mechanism for establishing quality of service (QoS) classes during the virtual channel setup, thereby allotting a predetermined amount of bandwidth to the channel. QoS classes define five broad categories that are outlined, for example, by the ATM Forum's UNI 3.0/3.1 specification. Class 1 specifies performance requirements and indicates that ATM's quality of service should be comparable with the service offered by standard digital connections. Class 2 specifies necessary service levels for packetized video and voice. Class 3 defines requirements for interoperability with other connection-oriented protocols, particularly frame relay. Class 4 specifies interoperability requirements for connectionless protocols, including IP, IPX, and SMDS. Class 5 is effectively a “best effort” attempt at delivery; it is intended for applications that do not require guarantees of service quality.
In conventional data networks, such as the typical Ethernet LAN or X.25 WAN, there are no explicit negotiations between the network and the user specifying the traffic profile and quality of service expected. Rather, the network is expected to provide each user with a “fair share” of the available bandwidth.
However, in an ATM network, fair allocation of bandwidth requires users to adjust their transmission rates according to the feedback from the network. ATM networks carry fixed bandwidth services required for multimedia applications (constant bit rate (CBR) traffic) and guaranteed bandwidth services for high-priority data applications (variable bit rate (VBR) traffic). The remaining bandwidth, not used by guaranteed bandwidth services, must be shared fairly across all users. The ATM Forum refers to services that make use of this otherwise idle bandwidth as available bit rate (ABR) services.
Although these ABR applications must contend for remaining available bandwidth and would not provide specific throughput guarantees, ABR applications still would require fair access to the available bandwidth with a minimum of cell loss. If ABR traffic had no mechanism to determine if sufficient bandwidth were available to handle the transmission on the network and traffic was simply fed in, network congestion might result in dropped cells, and application traffic might be lost. ABR flow control is an ATM layer service category for which the limiting ATM layer transfer characteristics provided by the network may change after establishing the network connection. A flow control mechanism is specified which supports several types of feedback to control the source rate in response to changing ATM layer transfer characteristics. When the network becomes congested, the end-stations outputting ABR traffic are instructed to reduce their output rate. It is expected that an end-system that adapts its traffic in accordance with the feedback will experience a low cell loss ratio and obtains a fair share of the available bandwidth according to a network-specific allocation policy. Cell delay variation is not controlled in this service, although admitted cells are not delayed unnecessarily.
In this end-to-end rate-based scheme, the source (e.g., a user remote site
103
) of a virtual circuit (VC) indicates the desired rate in a resource management cell (RM cell). An RM cell is a standard 53-byte ATM cell used to transmit flow-cont
Babu K. C.
Balasubramanyam R.
Cohen Michael S.
Kumar P.K. Nanda
Ramanathan Murali
e-Cell Technologies
McDermott & Will & Emery
Ramakrishnaiah Melur
Woo Stella
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