Provision of SPS timing signals

• US 5,510,797 A
• Filed: 04/15/1993
• Issued: 04/23/1996
• Est. Priority Date: 04/15/1993
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Abraham, Charles, Janky, James M.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/047,859
• Time in Patent Office: 1,104 Days
• Field of Search: 342/352, 342/357, 375/107, 379/63, 370/104.1, 370/50, 368/47, 455/51.1, 455/51.2
• US Class Current: 342/352
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04J 3/0652 Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP] bus network with centralized control in which slots are of a TDMA packet structure H04L12/4035

Abstract

Methods for provision of a sequence of timing signals for one or a plurality of microprocessors, microprocessor peripheral devices or other timing-controlled instruments ("users"), using timing signals determined from a Satellite Positioning System (SPS), such as GPS or GLONASS. In a first embodiment, one or a plurality of users is individually provided with SPS signal antennas and receiver/processors, and timing signals are optionally individually for each user. The timing signals can be periodic, for example, a One-Pulse-Per-Second signal for fine corrections of high frequency timing signals issued by an internal or external clock. The timing signals can also be substantially non-periodic. The timing signals may also be used to determine the time at which selected events occur, such as issuance of interrupt commands in, or directed to, a microprocessor. In another embodiment, CDMA or spread spectrum communications can be implemented and improved by using frequency hopping or other carrier-coded communications in which a time interval for use of the present carrier code is determined by two spaced apart timing signals received from an SPS timing device. In another embodiment, transmission times for each of a plurality of TDMA communications stations are synchronized using SPS timing signals. In another embodiment, each of a plurality of cellular telephone (CT) users is allocated to an appropriate CT cell for signal transmission and receipt, using timing and location information obtained from differential SPS signals.

Claims

1. A method for providing a sequence of timing signals for a network of M microprocessors or other timing-controlled electronic instruments, numbered m=1, 2, . . . , M, (M≧

2), the method comprising the steps of;

providing a network containing a plurality of M timing-controlled electronic instruments, numbered m=1, 2, . . . , M (M≧

2);

providing each of the M electronic instruments with an internal clock that generates and issues internal tinning signals for use in operations by that instrument;

providing a GPS signal antenna and GPS signal receiver/processor, to receive and process GPS signals from two or more GPS satellites, to use these GPS signals to determine the times of receipt of these signals at the GPS antenna, to continually compute and transmit a sequence of time measurement signals, which have associated timing errors of at most about one microsecond and which are transmitted at least once in every time interval of length at most about one second; and

causing each of the M instruments to receive this sequence of time measurement signals from the GPS receiver/processor and to adjust its internal timing signals to be synchronized with this sequence of time measurement signals,

whereby the timing of operations performed by each of the M instruments is synchronized with the sequence of timing signals.

2. The method of claim 1, wherein said step of adjusting said internal timing signals for said instrument number m comprises:

determining the time interval Δ

t(rcvr,m) presently required for signal propagation from said GPS receiver/processor to said instrument m (m=1, 2, . . . , M) at each of a selected sequence of times; and

compensating for this value of the time interval Δ

t(rcvr,m) in adjusting said internal timing signals for said instrument number m.

3. The method of claim 1, further comprising the steps of:

transmitting at least one message, containing information other than a time measurement signal, from a first instrument numbered m1 to a second instrument numbered m2, where m1 and m2 are distinct numbers (m1≠

m2) drawn from the numbers m=1, 2, . . . , M; and

attaching to this message a time stamp indicating the time, determined by the instrument number m 1, that this message is transmitted from the instrument number m1 to the instrument number m2.

4. A method for synchronizing communications between two or more users in a code division multiple access (CDMA) communications system, the method comprising the steps of:

providing a plurality of M electronic communications means, numbered m=1, 2, . . . , M (M≧

2), for transmitting electromagnetic signals to, and receiving electromagnetic signals from, each other, where each communications means has an internal clock that generates and issues internal timing signals for use by that communications means, and where, if communications means number m transmits one or more signals during a selected time interval T_m,n ={t|t_m,n ≦

t<

t_m,n+1 (n=1, . . . , N;

N≧

1)}, communications means number m uses a selected transmission code C_m,n for encoding this transmission during the time interval T_m,n ;

for two distinct numbers m1 and m2 (m1≠

m2), drawn from the set of numbers m=1, 2, . . . , M, providing communications means number m1 with a transmission code C_m1,n1 for a first selected sequence of time intervals T_m1,n1 and with a transmission code C_m2,n2 for a second selected sequence of time intervals T_m2,n2, where n1 and n2 are drawn from the set of numbers n=1, . . . , N;

providing a GPS signal antenna and GPS signal receiver/processor, to receive and process GPS signals from two or more GPS satellites, to use these GPS signals to determine the times of receipt of these signals at the GPS antenna, to continually compute and transmit a sequence of time measurement signals, which have associated timing errors of at most about one microsecond and which are transmitted at least once in every time interval of length at most about one second, to provide this sequence of time measurement signals for communications means numbers m1 and m2;

causing each of the instruments number m1 and m2 to receive this sequence of time measurement signals from the GPS receiver/processor and to adjust its internal timing signals to be synchronized with this sequence of time measurement signals,

causing the communications means number m1 to generate and issue the following sequences;

a first sequence of one or more pairs of timing signals at times t=t_m1,m1 and t=t_m1,n1+1, corresponding to the beginning time and the ending time of the selected time intervals T_m1,n1 ; and

a second sequence of one or more pairs of timing signals at times t=t_m2,n2 and t=_m2,n2+1, corresponding to the beginning time and the ending time of the selected time intervals T_m2,n2 ;

causing the communications means number m1 to transmit a signal that is encoded using the communication code C_m1,n1 during at least one of the selected time intervals T_m1,n1 ; and

causing the communications means number m1 to receive a signal transmitted by communication means number m2 during at least one of the selected time intervals T_m2,n2 and to use the transmission code C_m2,n2 to decode this received signal.

5. The method of claim 4, further comprising the steps of:

transmitting at least one message, containing information other than a time measurement signal, from said instrument numbered m1 to said instrument numbered m2; and

attaching to this message a time stamp indicating the time, determined by said instrument number m1, that this message is transmitted from said instrument number m1 to said instrument number m2.

6. A method for communicating information from a first location to a second location by means of spread spectrum communications, the method comprising the steps of:

providing an electronic communications means transmitter at a first location that transmits, at least once per second, an arbitrary signal using any of a selected set of carrier frequencies {f_n }_n (n=1, 2, . . . , N;

N≧

2), with at least two carrier frequencies f_n being distinct from each other;

providing an electronic communications means receiver at a second location, spaced apart from the first location, that is capable of receiving and interpreting an arbitrary signal using any of the selected set of frequencies {f_n }_n ;

providing each of the transmitter and the receiver with a sequence of time measurement signals from a GPS signal receiver/processor, which time measurement signals have associated timing errors that are at most about one microsecond and which are received at least once in every time interval of length at most about one second, at a selected set of times {t_n }_n, where t_n <

t_n+1 (n=1, 2, . . . , N-1);

causing the electronic communications means transmitter to transmit a message and the electronic communications means receiver to receive this message, where the transmitter uses the carrier frequency f_n during the time interval given by t_n <

t<

t_n+1, and uses at least two distinct carrier frequencies;

;

transmitting at least one message, containing information other than a time measurement signal, from said transmitter to said receiver; and

attaching to this message a time stamp indicating the time, determined by the transmitter, that this message is transmitted from the transmitter to the receiver.

7. A method for synchronizing communications between a plurality of users in a time division multiple access (TDMA) communications system, the method comprising the steps of:

providing a plurality of M electronic communications means, numbered m=1, 2, . . . , M (M≧

2) for transmitting signals to, and receiving signals from, each other, where each communications means has an internal clock that generates and issues internal timing signals for use by that communications means;

providing each communications means number m (1≦

m≦

M) with a sequence of one or more selected time intervals T_m,n ={t|t_m,n ≦

t<

t_m,n+1 (n=1, . . . , N-1;

N≧

2)}, during which communications means number m may transmit signals, where any two time intervals T_m1,n1 and T_m2,n2 have no overlapping time values if m1≠

m2, or n1≠

n2, or both m1≠

m2 and n1≠

n2 (m1 and m2=1, 2, . . . , M;

n1 and n2=1, . . . , N);

providing a GPS signal antenna and GPS signal receiver/processor to receive and process GPS signals from a plurality of two or more GPS satellites, and to use these GPS signals to continually compute and transmit a sequence of time measurement signals, which have associated timing errors that are at most about one microsecond and which are transmitted at least once in every time interval of length at most about one second;

causing each of communications means number m (m=1, 2, . . . , M) to receive the sequence of time measurement signals issued by the GPS receiver/processor and to synchronize the internal clock of communications means number m to these timing signals; and

causing at least one of the communications means number m to transmit a signal during at least one of the time intervals for which t_m,n ≦

t<

t_m,n+1 (n=1, . . . , N).

8. The method of claim 7, further comprising the steps of:

transmitting at least one message, containing information other than a time measurement signal, from said instrument numbered m1 to said instrument numbered m2; and

attaching to this message a time stamp indicating the time, determined by said instrument number m1, that this message is transmitted from said instrument number m1 to said instrument number m2.