Methods and apparatus for synchronization in a wireless network

• US 6,243,372 B1
• Filed: 11/14/1996
• Issued: 06/05/2001
• Est. Priority Date: 11/14/1996
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Omnipoint Corp. (Deutsche Telekom AG)
• Inventors: Petch, Byran K., Lindsay, Charles L., Jensen, Ryan N.
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/749,105
• Time in Patent Office: 1,664 Days
• Field of Search: 370/310, 370/315, 370/316, 370/324, 370/350, 370/503, 370/516, 370/522, 370/520, 375/343, 375/356, 375/357, 375/367, 375/371, 375/137, 375/145, 375/149, 455/502, 455/422
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
• CPC Class Codes: H04L 7/0331 with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock H04L7/0337 takes precedence
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15

Abstract

As part of a preferred communication protocol, base stations which are synchronized to a PSTN of a wireless communication network, periodically transmits a preamble. A remote detects the preamble and, upon verification of the data contained in the base station transmission, sets its counter to an initialized state based on the received preamble. An early/late analysis of each subsequently received base station timing pulse is used to adjust both the mobile station timing and to adjust the output frequency of the mobile station master clock and codec clock to effectively maintain end to end synchronization with the respective base station and the PSTN throughout the duration of an established communication link.

Claims

1. A communication network, comprising:

a base station, said base station comprising

an adjustable base station oscillator circuit outputting a base station clock signal,

base station clock circuitry for adjusting said base station oscillator circuit, and

base station transmission circuitry for transmitting over the air, based on the base station clock signal, a preamble; and

a mobile station, said mobile station comprising

an antenna for receiving the preamble transmitted by said base station,

mobile station circuitry for detecting the preamble and generating a base station timing signal upon detection of the preamble,

an adjustable mobile station oscillator circuit outputting a mobile station clock signal,

a mobile station controller outputting a controller signal comprising a timing count based on the mobile station clock signal; and

mobile station clock circuitry for generating an adjustment signal to adjust said mobile station controller, the adjustment signal determined by the base station timing signal and the controller signal.

2. The communication network of claim 1, said base station further comprising interface circuitry for generating a reference clock signal derived from a reference network.

3. The communication network of claim 2, said base station further comprising

a first dividing circuit for deriving a lower frequency component signal from the base station clock signal,

a second dividing circuit for deriving a lower frequency component signal from the reference clock signal, and

circuitry for comparing the lower frequency component signal from the base station clock signal with the lower frequency component signal from the reference clock signal and generating a corresponding reference signal comparison output signal.

4. The communication network of claim 3, wherein said base station clock circuitry for adjusting said base station oscillator circuit comprises a varactor tuning circuit which supplies a voltage across said base station oscillator circuit directly proportional to the reference signal comparison output signal.

5. The communication network of claim 3, wherein said circuitry for comparing the lower frequency component signal from the base station clock signal with the lower frequency component signal from the reference clock signal comprises an XOR circuit.

6. The communication network of claim 2, wherein the reference clock signal is derived from a public switched telephone network.

7. The communication network of claim 2, wherein said adjustable base station oscillator circuit comprises a voltage sensitive 20 MHZ crystal and the reference clock signal comprises an 8 KHZ signal supplied by a public switched telephone network.

8. The communication network of claim 1, said mobile station further comprising circuitry for generating a vocoder clock signal synchronized to the mobile station clock signal.

9. The communication network of claim 8, wherein said circuitry for generating the vocoder clock signal comprises an adjustable timing oscillator circuit.

10. A method of synchronizing a base station and a remote station in a communication network, comprising:

generating timing information in the form of a periodically transmitted preamble at a base station;

transmitting the timing information over the air from the base station to the remote station;

generating a clock signal at the remote station;

comparing the timing information and the clock signal at the remote station;

adjusting the clock signal without reference to an external clock, based on said comparing of the timing information and the clock signal;

comparing a base station clock signal used in said generating timing information with a reference clock signal derived from a reference network;

adjusting the base station clock signal based on the reference clock signal;

receiving periodic GPS pulse signals at the base station; and

resetting a signal frame transmission cycle derived from the base station clock signal based upon receipt of a GPS pulse signal.

11. A method of synchronizing communication signals sent over the air between a base station and a remote station in a communication network, comprising:

generating a first clock signal at the base station;

comparing the first clock signal with a reference clock signal derived from a GPS network;

adjusting the first clock signal based on the reference clock signal;

transmitting a message from the base station to the remote station;

deriving the adjusted first clock signal at the remote station based upon receipt of the message from the base station;

generating a second clock signal at the remote station; and

adjusting the second clock signal based on the derived first clock signal without reference to an external clock.

12. The method of synchronizing communication signals of claim 11, wherein the message transmitted from the base station comprises a preamble, and wherein the adjusted first clock signal is derived by detecting the preamble at the remote station with a digital matched filter circuit which produces a matched filter detect pulse.

13. A method of synchronizing communication signals sent over the air between stations of a communication network, comprising:

generating a first clock signal at a first station;

operating a first communication circuitry at the first station according to a first station frame transfer cycle matching the first clock signal;

comparing the first clock signal with a reference clock signal derived from a reference network;

adjusting the first clock signal based upon the reference clock signal;

transmitting a communication signal from the first station;

generating a second clock signal at a second station;

operating a second communication circuitry at the second station according to a second station frame transfer cycle matching the second clock signal;

receiving the communication signal transmitted from the first station at the second station;

deriving the adjusted first clock signal at the second station upon receiving the communication signal transmitted from the first station at the second station; and

adjusting the second clock signal on the second station, based upon the derived adjusted first clock signal, without reference to an external clock.

14. The method of synchronizing communication signals of claim 13, wherein the reference network is a GPS network.

15. The method of synchronizing communication signals of claim 13, wherein the reference network is a public switched telephone network.

16. A communication network, comprising:

a base station comprising

a base station radio comprising a base station radio input and a base station radio output, and

a base station clock circuit comprising a base station clock circuit output comprising a base station clock signal, the base station clock signal comprising said base station radio input, said base station radio output comprising a message comprising a plurality of bits, the message transmitted over the air at a time based on the base station clock signal; and

a remote station comprising

a remote station radio comprising an antenna for receiving the message,

a remote station module comprising a matched filter circuit comprising an input comprising one or more of the plurality of bits of the message and comprising an output comprising a base station timing signal, and an early/late detector comprising an input comprising the base station timing signal and comprising an output comprising an adjustment signal, and

a remote station clock comprising an input based on the adjustment signal and comprising an output comprising a remote station clock signal.

17. The communication network of claim 16, wherein the message comprises a preamble.

18. The communication network of claim 16, wherein said first remote station circuitry for generating the base station timing signal comprises a digital matched filter circuit which produces a matched filter detect pulse indicative of the base station clock signal.

19. The communication network of claim 16, wherein said remote station clock comprises an adjustable oscillator circuit.

20. The communication network of claim 19, wherein the frequency of the remote station clock signal varies according to a change in a voltage applied across said adjustable oscillator circuit.

21. The communication network of claim 19, wherein said remote station clock further comprises a varactor tuning circuit which applies a variable voltage across said adjustable oscillator circuit.

22. The communication network of claim 19, wherein the remote station module comprises a digital matched filter for generating the base station timing signal based on receipt of one or more of the plurality of bits of the message, an early/late detector comprising an input comprising the base station timing signal and an output comprising the remote station timing control signal, and a pulse width modulator comprising an input comprising the remote station timing control signal and an output comprising a pulse width modulated signal.

23. The communication network of claim 16, wherein said base station further comprises a GPS receiver, and wherein the base station clock signal is compared to a reference clock signal received by said GPS receiver and the base station clock signal is adjusted based on the comparison of the base station clock signal to the reference clock signal.