Subscriber frequency control system and method in point-to-multipoint RF communication system

• US 6,240,556 B1
• Filed: 06/03/1998
• Issued: 05/29/2001
• Est. Priority Date: 11/21/1995
• Status: Expired due to Term

• Current Assignee: Alcatel USA Sourcing L.P. (Nokia Corporation)
• Original Assignee: Stanford Telecommunications, Inc. (Nokia Corporation)
• Inventors: Evans, Allan, Chen, Horen
• Primary Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US09/089,969
• Time in Patent Office: 1,091 Days
• Field of Search: 348/10, 348/11, 348/12, 348/13, 348/7, 455/3.2, 455/5.1, 455/6.2, 455/6.3, 455/71, 455/76, 455/72, 375/225, 375/227, 375/219, 375/220, 375/222, 375/259, 375/377, 370/347, 370/337, 370/350, 725/121, 725/125, 725/131, 725/132, 725/114
• US Class Current: 725/114
• CPC Class Codes: H04N 21/4622 Retrieving content or additional data from different sources, e.g. from a broadcast channel and the Internet web site content organization and management for information retrieval from the Internet G06F16/958; transmission by internet of broadcast information H04H60/82; stock exchange data over packet-switching network H04L12/1804; push services including data channel over packet-switching network H04L12/1859
• CPC Class Codes: H04N 21/4782 Web browsing , e.g. WebTV
• CPC Class Codes: H04N 5/44 Receiver circuitry for the reception of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 7/173 with two-way working, e.g. subscriber sending a programme selection signal
• CPC Class Codes: H04N 7/20 Adaptations for transmission via a GHz frequency band, e.g. via satellite

Abstract

A point-to-multipoint star configured terrestrial radio communication system having at least one base station transmitting to and receiving RF communication signals from a plurality of associated subscriber stations in the 0.3-300 GigaHertz (GHz) range. The system includes means for reducing frequency uncertainty, drift or error of the RF transmissions from each of the subscriber stations to the base station. Each subscriber station has a low cost local reference oscillator, and the system incorporates a reference broadcast signal of high frequency precision from the base station and at each subscriber station there is means for measuring frequency error and compensating for frequency drift/error in the low-cost oscillator at the subscriber station. Moreover, the system can provide an estimate obtained from measuring each subscriber frequency drift or error in the base station and relaying the measured error to the corresponding subscriber station to compensate for that subscriber'"'"'s transmitter'"'"'s local oscillator be out of frequency.

Claims

1. In a point-to-multipoint, star-configured, terrestrial radio communications system having at least one base station transmitting to and receiving upstream RF communication signals in a burst mode from a plurality of associated subscriber stations in the 0.3-300 GigaHertz (GHz) range, the improvement comprising a system for reducing frequency uncertainty, drift or error of the RF transmissions from each of said subscriber stations to said base station, each subscriber station having a local reference oscillator, said system incorporating units for performing:

a reference broadcast signal of high frequency precision from said base station and elements at the subscriber stations for measuring the frequency error and compensating for frequency drift error in said subscriber'"'"'s stations'"'"' local reference oscillator,

for all bursts from all said associated subscriber stations between transmission bursts of each said associated subscriber station, respectively.

2. The radio communication system defined in claim 1 wherein said local reference oscillator at each subscriber station is a low cost crystal oscillator.

3. In a point-to-multipoint, star-configured, terrestrial radio communications system having at least one base station transmitting to and receiving upstream RF communication signals in a burst mode from a plurality of associated subscriber stations in the 0.3-300 GigaHertz (GHz) range, the improvement comprising a system for reducing frequency uncertainty, drift or error of the RF transmissions from each of said subscriber stations to said base station, each subscriber station having a local reference oscillator, said system incorporating units for performing:

providing an estimate obtained from measuring each subscriber'"'"'s frequency drift/error in the base station and relaying the measured error to the corresponding subscriber station to compensate for frequency drift/error in that subscriber'"'"'s transmitter local reference oscillator,

for all bursts from all said associated subscriber stations between transmission bursts of each said associated subscriber station, respectively.

4. The radio communication system defined in claim 3 wherein said local reference oscillator at each subscriber station is a low-cost crystal oscillator.