Invalidity dossier
US 5442625
Code division multiple access system providing variable data rate access to a user
Current assignee: AT&T Inc
Added 9/21/2026, 9:37:31 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US5442625A
Title: Code division multiple access system providing variable data rate access to a user
Patent number: US5442625A (application US08/242,471)
Inventors: Richard D. Gitlin; Chih-Lin I
Assignee: Original assignee AT&T IPM Corp.; current assignee listed as AT&T Inc.
Key dates: Priority/filing date 1994-05-13; publication (grant) 1995-08-15; anticipated expiration 2014-05-13. Legal status listed as "Expired - Lifetime."
Purpose: The invention relates to code division multiple access (CDMA) systems and, more particularly, to a CDMA system for providing a user with variable and dynamic bandwidth capacity access.
Plain-language scope (as described in the supplied text):
- In CDMA, each call/user gets a unique binary spreading sequence ("code"); the user's signal is multiplied by that code and spread onto a channel much wider than the user's signal bandwidth ("spreading gain"). All active users share the same system channel frequency spectrum simultaneously, and capacity is proportional to spreading gain given a required signal-to-interference (S/I) ratio.
- The disclosed "multi-code CDMA system" lets a user at a radio transmitter unit dynamically change its source data rate.
- An adjustable coding means spreads and transmits the user's digital information, received at the selected bit rate, up to a channel bit rate that at least equals the highest of a plurality of source bit rates.
- The source bit rates include a basic bit rate R and at least one multiple M of R, where M is an integer of at least 1; the user's input selects a rate by identifying the multiple M to a base station.
- Embodiments include transmitter units (FIGS. 2–4), a flow chart for dynamically changing the source bit rate (FIG. 5), and an illustrative base-station uplink load graph (FIG. 6). Components described include a convolutional coder, interleaver, Walsh modulator, code spreader, and in-phase/quadrature coders.
What the excerpt does not establish: Full claim language and claim count; the complete description and omitted text; all drawing details; the substantive content of cited prior art (e.g., the Wi-LAN Inc. Technical Bulletin No. 3, October 1993); prosecution history; and any findings on validity, infringement, or ownership transfers beyond the listed assignment entries.
Source: https://patents.google.com/patent/[US5442625](/patent/US5442625)/en
Generated 10/1/2026, 10:02:00 PM
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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