Bell Atlantic Network Svcs. v. Covad

• Decision Date: 17 August 2001
• Parties: (Fed. Cir. 2001) BELL ATLANTIC NETWORK SERVICES, INC. (doing business as Verizon Services, Inc.), Plaintiff-Appellant, v. COVAD COMMUNICATIONS GROUP, INC., DIECA COMMUNICATIONS, INC. (doing business as COVAD Communications Company), and COVAD COMMUNICATIONS COMPANY, INC., Defendants-Appellees. 00-1475
• Court: U.S. Court of Appeals — Federal Circuit

Page 1258

262 F.3d 1258 (Fed. Cir. 2001)

BELL ATLANTIC NETWORK SERVICES, INC. (doing business as Verizon Services, Inc.) Plaintiff-Appellant, v. COVAD COMMUNICATIONS GROUP, INC., DIECA COMMUNICATIONS, INC. (doing business as COVAD Communications Company), and COVAD COMMUNICATIONS COMPANY, INC., Defendants-Appellees.

00-1475

United States Court of Appeals for the Federal Circuit

August 17, 2001

Appealed from: United States District Court for the Eastern District of Virginia Judge Jerome B. Friedman

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Richard G. Taranto, Farr & Taranto, of Washington, DC, argued for plaintiff-appellant. Of counsel on the brief were George C. Lombardi, and James F. Hurst, Winston & Strawn, of Chicago, Illinois; Adam T. Bernstein, Verizon Communications, of New York, New York; and John Thorne, Verizon Services, Inc., of Arlington, Virginia.

Ruffin B. Cordell, Fish & Richardson P.C., of Washington, DC, argued for defendants-appellees. With him on the brief were Michael J. McKeon, and Lauren A. Degnan.

Before LOURIE, Circuit Judge, PLAGER, Senior Circuit Judge, and GAJARSA, Circuit Judge.

GAJARSA, Circuit Judge.

Bell Atlantic Network Services, Inc. ("Bell Atlantic") is the owner of United States Patent No. 5,812,786 ("the '786 patent"), which concerns certain data transmission services, particularly certain digital subscriber line ("DSL") services.¹ In 1999, Bell Atlantic brought this patent infringement action against Covad Communications Company, Inc., DIECA Communications, Inc., and Covad Communications Group, Inc. (collectively "Covad"), alleging that certain DSL services offered by Covad infringe the '786 patent. On April 4, 2000, the United States District Court for the Eastern District of Virginia ("district court") determined that certain limitations required by claims 1 and 21 of the '786 patent are not present in Covad's DSL systems either literally or under the doctrine of equivalents, and granted Covad's motion for summary judgment of noninfringement. Bell Atlantic Network Servs. v. Covad Communications Group, Inc., 92 F.Supp.2d 438 (E.D.Va. 2000). Bell Atlantic appeals that judgment.

For the reasons discussed below, we affirm.

I. BACKGROUND

A. Introduction

DSL technology is a relatively new data transfer technology that can turn a single pair of copper telephone wires ("a copper pair") into a high-speed, multi-channel, data delivery system. A basic DSL system consists of two high-speed modems located at each end of a conventional telephone line- one at the telephone company's end, and one at the customer's end. This technology allows customers to gain high-speed access to large sources of data, including the internet, without the need for expensive additional wiring.

Prior to the advent of DSL technology, copper telephone wiring transmitted simple voice data at frequencies below four kilohertz (4 kHz). The transmission of this common residential telephone service is known as "POTS" ("Plain Old Telephone Service"). It has been known for some time that additional communications streams can be carried on the same wire with POTS through a technique called "frequency division multiplexing." Frequency division multiplexing is a scheme in which numerous signals are combined for transmission on a single communications line by assigning each signal a different frequency. Until recently, much of the available range of frequencies, or "bandwidth," on twisted-pair copper telephone wiring remained unused. DSL technology enables high-speed transmissions over common copper telephone wiring by exploiting the unused, higher frequencies over twisted-pair wires.

In order to take advantage of the higher frequencies, DSL technology employs high-speed modems, or transceivers, to modulate and demodulate the high-frequency data. The transceivers allow the low frequencies to be used for traditional POTS communication, while simultaneously using the higher frequencies for high-speed digital communications. A transceiver must be employed at each end of the "subscriber loop"- the customer's end and the telephone company's switching office.

Currently, there are two major types of DSL technology. Symmetric or single-line digital subscriber line ("SDSL") technology uses a range of frequencies as a single two-way channel, and transmits and receives data on this channel at the same rate. Asymmetric digital subscriber line ("ADSL") technology allocates different amounts of bandwidth based on the needs of the customer. SDSL technology may be more suitable for videoconferencing applications, because equal upstream and downstream data transmission rates are preferable. However, ADSL technology may be more suitable for video-on- demand services and for customers who download more data in the "downstream" direction than they upload in the "upstream" direction. Traditionally, ADSL systems have allocated more bandwidth for downstream communication than for upstream communication. Indeed, prior art ADSL systems allocate only a small amount of bandwidth (approximately 15 kHz) to the upstream channel, also referred to as the "control" channel.

Figure 4 of the '786 patent specification illustrates how conventional ADSL systems have divided common telephone lines into different channels using frequency division multiplexing [Tabular or Graphical Material Omitted]

The diagram illustrates that in prior art ADSL systems, POTS service uses only 4 kHz, the control channel uses about 15 kHz, and the downstream data channel uses most of the remaining bandwidth.

B. The '786 Patent Claims

The invention disclosed by the '786 patent concerns data transmission systems that can be used to provide DSL services with variable rates and modes without replacing the underlying hardware and equipment. The written description of the '786 patent notes that prior art ADSL systems were "not well suited for other services in which the nature and amount of data and control signal transfer is substantially different and changes frequently." '786 patent, col. 2, ll. 26-28. The specification observes that "the two- way control channel may be unacceptably slow for services such as interactive multi-media, distance learning, or accessing a server in a remote local area network (LAN) over a POTS line using a single copper pair. One or more of these services may require a bi-directional control channel of up to, for example, 384 kbps [kilobits per second] in order to allow substantially real-time communications so that a subscriber is not waiting for information to be transmitted." Id. at col. 2, ll. 29-36.

Thus, the invention disclosed by the '786 patent adds capabilities to current DSL technology by providing an ADSL system with "adjustable variable rate" functionality ("ADSL/AVR"). The '786 patent notes in the Summary of the Invention that "such a network has the advantages of conventional ADSLs, while allowing the data rate of the reverse control signaling channel to be controllably increased so as to have a higher rate transmission than ADSL in a bi-directional mode." Id. at col. 3, ll. 15-19. In other words, the ADSL system described by the '786 patent allows customers to "access any file server, download files, store information, and perform any other functions permitted in the optimum mode and at the optimum rate for that function." Id. at col. 15, ll. 7-9.

Claims 1 and 21 are the two independent claims at issue in this appeal. The claims read as follows:

1.A transmission system for variably transmitting information data in a plurality of different modes over a network, said transmission system comprising:

a first transceiver, connected to a first end of a subscriber loop, for selectively operating in one of said plurality of different modes, said first transceiver transmitting or receiving signals, at a first transmission rate, on a first channel, and transmitting or receiving signals, at a second transmission rate, on a second channel, in each of said plurality of different modes;

a second transceiver, connected to said first transceiver via said subscriber loop, for selectively operating in one of said plurality of different modes, said second transceiver transmitting or receiving said first channel signals at said first transmission rate on said first channel and transmitting or receiving said second channel signals at said second transmission rate on said second channel; and

a controller connected to said first transceiver for selectively changing said first and second transmission rates.

21.An ADSL/AVR transmission system for variably transmitting information data over a plurality of channels, comprising:

a first ADSL/AVR transceiver for transmitting or receiving signals at a first transmission rate on a first channel, and transmitting or receiving signals at a second transmission rate on a second channel;

a second ADSL/AVR transceiver for transmitting or receiving signals at said first transmission rate on said first channel and transmitting or receiving said second channel signals at said second transmission rate on said second channel; and

a subscriber loop for connecting said first and second ADSL/AVR transceivers together; wherein

each of said first and second ADSL/AVR transceivers includes a controller for selectively changing the transmission rates on said first and second channels.

Id. at col. 17, ll. 5-23; col. 19, ll. 27-44 (emphasis added).

C. The Accused Covad DSL System

Covad provides its customers with both ADSL and SDSL services. Covad also uses DSL transceivers, called "line cards," at both ends of the subscriber loop. In Covad's ADSL line card transceivers, the allocation of bandwidth between the upstream and downstream channels is fixed, with most of the frequency allocated to the downstream channel. Because the bandwidth allocation is fixed, Covad's ADSL line card transceivers are incapable of shifting bandwidth between the...