US5659545A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for mobile unit acquisition in a satellite communication system and method therefor
Assignee: Google Technology Holdings LLC
•
Filing: 1994-11-15
•
Granted: 1997-08-19
•
Expires: 2014-11-15
Abstract
Abstract To obtain service from a satellite communication system, a mobile subscriber unit must acquire a TDMA communication channel. Because the satellites move with respect to the surface of the earth, propagation delays and Doppler shift affect the timing and frequency of received signals. A mobile subscriber unit synchronizes to the frequency and timing windows of a satellite communication station by receiving frequency and timing corrections during channel acquisition. The satellite initially estimates correction factors during initial acquisition requests and further estimates correction factors from synchronization bursts from the subscriber unit.
Inventors
- 👤 Kenneth L. Sowles
- 👤 Ralph C. Gregg
- 👤 Keith A. Olds
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:02
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/185; H04B7/1853; H04B7/18558
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
128 words
A method of synchronizing a subscriber unit with a node of a communication system, said method comprising the steps of: receiving an assignment of a traffic channel, said traffic channel being a time division multiple access (TDMA) frequency channel; sending a synchronization burst on said traffic channel; receiving timing and frequency correction data based on said synchronization burst, said timing and frequency correction data calculated by said node by comparing an arrival time of said synchronization burst with a time-slot of said traffic channel, said frequency correction data calculated by comparing a frequency of said traffic channel with a frequency of said synchronization burst; and adjusting timing and frequency characteristics of said subscriber unit for communication over said traffic channel based on said timing and frequency correction data.
Claim 2
Independent Claim
128 words
A method of synchronizing a subscriber unit with a node of a communication system, said method comprising the steps of: receiving an assignment of a traffic channel, said traffic channel being a time division multiple access (TDMA) frequency channel; sending a synchronization burst on said traffic channel; receiving timing and frequency correction data based on said synchronization burst, said timing and frequency correction data calculated by said node by comparing an arrival time of said synchronization burst with a time-slot of said traffic channel, said frequency correction data calculated by comparing a frequency of said traffic channel with a frequency of said synchronization burst; and adjusting timing and frequency characteristics of said subscriber unit for communication over said traffic channel based on said timing and frequency correction data.
Claim 3
Dependent Claim
32 words
A method as claimed in claim 1 further comprising the step of communicating data with said node over said traffic channel within said time-slot and at said frequency of said traffic channel.
Claim 4
Dependent Claim
31 words
A method as claimed in claim 1 further comprising the step of sending a second synchronization burst having an adjusted transmit time and adjusted frequency in response to the adjusting step.
Claim 5
Dependent Claim
50 words
A method as claimed in claim 1 further comprising the steps of: selecting a broadcast channel, said broadcast channel transmitting classes of subscriber units for which acquisition is prohibited; determining if acquisition is permitted based on a class of said subscriber unit; and sending an acquisition request to said node.
Claim 6
Dependent Claim
52 words
A method as claimed in claim 1 further comprising the steps of: selecting a broadcast channel, said broadcast channel providing frequency and time-slot information for at least two acquisition channels; randomly selecting one of said acquisition channels; and sending an acquisition request to said node on said one of said acquisition channels.
Claim 7
Dependent Claim
43 words
A method as claimed in claim 1 further comprising the steps of: receiving a downlink synchronization message from said node indicating whether synchronization has been achieved; and switching to a traffic mode when said downlink synchronization message indicates that synchronization has been achieved.
Claim 8
Dependent Claim
35 words
A method as claimed in claim 6 wherein said traffic channel is configured for bi-phase-shift-keyed (BPSK) modulation, and wherein the switching step includes the step of switching said traffic channel to quadrature phase-shift-keyed (QPSK) modulation.
Claim 9
Dependent Claim
55 words
A method as claimed in claim 6 wherein further comprising the steps of: sending a sync acknowledge message to said node to acknowledge receipt of said downlink synchronization message; and receiving a traffic mode message from said node that instructs said subscriber unit to switch to a quadrature phase-shift-keyed (QPSK) modulation on said traffic channel.
Claim 10
Dependent Claim
69 words
A method as claimed in claim 1 wherein said node is a low-earth orbiting satellite that is moving rapidly with respect to said subscriber unit, and wherein the receiving an assignment step comprises receiving an assignment of said traffic channel, said frequency of said traffic channel is affected by the satellite's movement, and said time-slot of said traffic channel is affected by a changing propagation distance to said satellite.
Claim 11
Independent Claim
101 words
A method of synchronizing a node of a communication system with a subscriber unit, said method comprising the steps of: receiving a synchronization burst from said subscriber unit on a TDMA traffic channel; comparing an arrival time of said synchronization burst with a time-slot of said TDMA traffic channel to determine timing correction data; comparing a frequency of said TDMA traffic channel with a frequency of said synchronization burst to determine frequency correction data; and sending said timing and frequency correction data to said subscriber unit, said subscriber unit adjusting a transmit time and transmit frequency based on said correction data.
Claim 12
Independent Claim
101 words
A method of synchronizing a node of a communication system with a subscriber unit, said method comprising the steps of: receiving a synchronization burst from said subscriber unit on a TDMA traffic channel; comparing an arrival time of said synchronization burst with a time-slot of said TDMA traffic channel to determine timing correction data; comparing a frequency of said TDMA traffic channel with a frequency of said synchronization burst to determine frequency correction data; and sending said timing and frequency correction data to said subscriber unit, said subscriber unit adjusting a transmit time and transmit frequency based on said correction data.
Claim 13
Dependent Claim
57 words
A method as claimed in claim 10 further comprising the steps of: determining if a timing and frequency threshold are met; and sending a repeat burst message to said subscriber unit when said timing and frequency threshold are not met, said repeat burst message directing said subscriber unit to resend said synchronization burst using said correction data.
Claim 14
Dependent Claim
50 words
A method as claimed in claim 10 further comprising the steps of: determining if a timing and frequency threshold are met; sending a sync OK message when said timing and frequency threshold have been met; and switching from a synchronization mode to a traffic mode on said TDMA traffic channel.
Claim 15
Dependent Claim
47 words
A method as claimed in claim 12 further comprising the steps of: waiting for an acknowledgment of said sync OK message from said subscriber unit; and when said acknowledgment is not received within a predetermined time, sending a switch to traffic mode message to said subscriber unit.
Claim 16
Dependent Claim
82 words
A method as claimed in claim 10 further comprising the steps of: receiving an acquisition request from said subscriber unit; determining if said acquisition request is within a frequency and timing tolerance; when said acquisition request is within a frequency and timing tolerance, reserving said TDMA traffic channel for said subscriber unit; and transmitting to said subscriber unit a traffic channel assignment message which includes a frequency and time slot of said TDMA traffic channel and initial frequency and timing correction data.
Claim 17
Dependent Claim
112 words
A subscriber unit that synchronizes to a timing window of a communication station, said communication station moving with respect to earth's surface, said subscriber unit comprising: a transmitter for sending a synchronization burst on a traffic channel to said communication station; a receiver for receiving an assignment of said traffic channel from said communication station, said traffic channel being a time division multiple access (TDMA) frequency channel, and receiving timing and frequency correction data based on said synchronization burst; and a processor coupled to said receiver and said transmitter for adjusting timing and frequency characteristics of said transmitter for communicating over said traffic channel based on said timing and frequency correction data.
Claim 18
Dependent Claim
112 words
A subscriber unit that synchronizes to a timing window of a communication station, said communication station moving with respect to earth's surface, said subscriber unit comprising: a transmitter for sending a synchronization burst on a traffic channel to said communication station; a receiver for receiving an assignment of said traffic channel from said communication station, said traffic channel being a time division multiple access (TDMA) frequency channel, and receiving timing and frequency correction data based on said synchronization burst; and a processor coupled to said receiver and said transmitter for adjusting timing and frequency characteristics of said transmitter for communicating over said traffic channel based on said timing and frequency correction data.
Claim 19
Dependent Claim
46 words
A subscriber unit as claimed in claim 15 wherein said transmitter and receiver includes means for communicating data with said communication station over said traffic channel wherein said data is received by said communication station within a time-slot and at a frequency of said traffic channel.
Claim 20
Dependent Claim
27 words
A subscriber unit as claimed in claim 15 wherein said processor includes means for sending a second synchronization burst having an adjusted transmit time and adjusted frequency.
Claim 21
Dependent Claim
75 words
A subscriber unit as claimed in claim 15 wherein: said processor includes means for selecting a broadcast channel, said broadcast channel transmitting classes of subscriber units for which acquisition is prohibited; said processor includes means for determining if acquisition is permitted based on a class of said subscriber unit and said classes transmitted over said broadcast channel; and said transmitter includes means for sending an acquisition request to said communication station based on said class.
Claim 22
Dependent Claim
65 words
A subscriber unit as claimed in claim 15 wherein: said processor includes means for selecting a broadcast channel, said broadcast channel providing frequency and time-slot information for at least two acquisition channels, and includes means for randomly selecting one of said acquisition channels, and wherein said transmitter includes means for sending an acquisition request to said communication station on said one of said acquisition channels.
Claim 23
Dependent Claim
54 words
A subscriber unit as claimed in claim 15 wherein: said processor includes means for receiving a downlink synchronization message from said communication station indicating whether synchronization has been achieved; and wherein said transmitter and receiver include means for switching to a traffic mode when said downlink synchronization message indicates that synchronization has been achieved.
Claim 24
Dependent Claim
36 words
A subscriber unit as claimed in claim 20 wherein said traffic channel is configured for bi-phase-shift-keyed (BPSK) modulation, and wherein said transmitter and receiver include means for switching said traffic channel to quadrature phase-shift-keyed (QPSK) modulation.
Claim 25
Dependent Claim
48 words
A subscriber unit as claimed in claim 20 wherein: said transmitter includes means for sending a sync acknowledge message to said communication station to acknowledge receipt of said downlink synchronization message; and said receiver includes means for receiving a switch to traffic mode message from said communication station.
Claim 26
Dependent Claim
54 words
A subscriber unit as claimed in claim 15 wherein said communication station is a low-earth orbiting satellite that is moving rapidly with respect to said subscriber unit, and wherein a frequency of said traffic channel is affected by the satellite's movement, and a time-slot is affected by a changing propagation distance to said satellite.
References Cited (Backward Citations)
US3562432A
Cited
US3787634A
Cited
US3730998A
Cited
US3812430A
Cited
US3858007A
Cited
US3813496A
Cited
US3843843A
Cited
US3982075A
Cited
US4054753A
Cited
US4107608A
Cited
US4168398A
Cited
US4215239A
Cited
US4561099A
Cited
US4555782A
Cited
US4652834A
Cited
US4686673A
Cited
US4688217A
Cited
US4726040A
Cited
US5072445A
Cited
US4941155A
Cited
US5343497A
Cited
US5363373A
Cited
US5177740A
Cited
US5479409A
Cited
US5509035A
Cited
US5510797A
Cited
US5519710A
Cited
US5469467A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-08-18 | 2001-02-17 | 2001-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-08-18 | 2005-02-17 | 2005-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-08-18 | 2009-02-17 | 2009-08-19 | $7700.00 | Window Closed / Lapsed |