Mobile satellite communication system

• US 5,835,846 A
• Filed: 12/12/1995
• Issued: 11/10/1998
• Est. Priority Date: 12/13/1994
• Status: Expired due to Term

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Mobile Communications Network Inc. (Nippon Telegraph and Telephone Corporation)
• Inventors: Ohno, Yoshihisa, Nishi, Yasuki, Kodama, Eiji, Kobayashi, Hiroshi, Furukawa, Kenji
• Primary Examiner(s): Pham, Chi H.
• Application Number:
  US08/571,126
• Time in Patent Office: 1,064 Days
• Field of Search: 455/10, 455/12.1, 455/13.4, 455/52.1, 455/67.1, 455/69, 455/70, 455/134, 455/277.2, 455/226.1, 455/226.2, 455/226.3, 455/54.1, 455/54.2
• US Class Current: 455/10
• CPC Class Codes: H04B 7/18543 for adaptation of transmission parameters, e.g. power control for detecting or preventing errors in the information received H04L1/00
• CPC Class Codes: H04W 52/225 Calculation of statistics, e.g. average, variance
• CPC Class Codes: H04W 52/228 using past power values or information

Abstract

A transmission power control method in a mobile satellite communication system implementing accurate control of transmission power of a base station by obtaining an average received signal level at a mobile station at high accuracy. The mobile station measures an average received signal level Q_k in a predetermined period (step SP2), and informs the base station of the average received signal level Q_k and an actual measuring time T_k (step SP3). The base station calculates a total measuring time t_k which is the sum total of the actual measuring time T_k (step SP16), a corrected average received signal level R_k associated with the average received signal level during the total measuring time t_k (step SP18), and a measuring error ΔD_k (step SP17), and controls the transmission power on the basis of these values (step SP21). Estimating the measuring error ΔD_k in the total measuring time t_k longer than the individual actual measuring time T_k makes it possible to reduce the measuring error, thereby implementing highly accurate transmission power control.

Claims

1. A mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite,

said mobile station comprising:

measuring means for obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T; and

transmission means for informing said base station of said actual measuring time T_k and said average received signal level Q_k, and

said base station comprising;

means for extracting said actual measuring time T_k and said average received signal level Q_k from a received signal sent from said mobile station;

means for calculating a total measuring time t_k which is a sum total of said actual measuring time T_k ;

means for obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

storing means for storing a total measuring time t_k-1, a corrected average received signal level R_k-1 and a transmission power control amount Δ

P_k-1 at the end of a preceding measuring period of said mobile station;

means for obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of said corrected average received signal level R_k-1, said transmission power control amount Δ

P_k-1, said total measuring time t_k-1 said average received signal level Q_k, said actual measuring time T_k and said total measuring time t_k ;

means for calculating a transmission power control amount Δ

P_k of said base station on the basis of said measuring error Δ

D_k and a difference between said corrected average received signal level R_k and a predetermined reference value R_ref of the received signal level of said mobile station; and

means for obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k.

2. The mobile satellite communication system as claimed in claim 1, wherein said base station comprises means for setting an initial value P₀ of said transmission power at a predetermined value.

3. The mobile satellite communication system as claimed in claim 1, wherein said means for calculating a transmission power control amount obtains said present transmission power control amount Δ

P_k of said base station by adding said measuring error Δ

D_k to a difference between said reference value R_ref of the received signal level and said corrected average received signal level R_k.

4. The mobile satellite communication system as claimed in claim 1, wherein said means for calculating a transmission power control amount obtains said present transmission power control amount Δ

P_k of said base station by adding a sum of said measuring error Δ

D_k and a level setting error Δ

S_k at said base station to a difference between said reference value R_ref of the received signal level and said corrected average received signal level R_k.

5. The mobile satellite communication system as claimed in claim 1, wherein said means for obtaining said measuring error obtains said measuring error Δ

D_k by dividing a predetermined value C by a square root of said total measuring time t_k.

6. The mobile satellite communication system as claimed in claim 1, wherein said means for obtaining said corrected average received signal level obtains said corrected average received signal level R_k by the following equation:

space="preserve" listing-type="equation">R.sub.k ={(R.sub.k-1 +Δ

P.sub.k-1)t.sub.k-1 +Q.sub.k T.sub.k }/t.sub.k.

7. A mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite,

said mobile station comprising:

measuring means for obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T;

means for calculating a total measuring time t_k which is a sum total of said actual measuring time T_k ;

means for obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

storing means for storing a total measuring time t_k-1 and a corrected average received signal level R_k-1 at the end of a preceding measuring period of said mobile station;

means for extracting a transmission power control amount Δ

P_k-1 from a signal transmitted from said base station to said mobile station;

means for obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of said corrected average received signal level R_k-1, said transmission power control amount Δ

P_k-1, said total measuring time t_k-1, said average received signal level Q_k, said actual measuring time T_k and said total measuring time t_k ; and

transmission means for informing said base station of said corrected average received signal level R_k, and

said base station comprising;

means for extracting said corrected average received signal level R_k from a received signal sent from said mobile station;

means for calculating said transmission power control amount Δ

P_k of said base station on the basis of a prestored level setting error Δ

S_k and a difference between said corrected average received signal level R_k and a predetermined reference value R_ref of the received signal level of said mobile station;

means for obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k ; and

means for transmitting information on said present transmission power control amount Δ

P_k to said mobile station.

8. The mobile satellite communication system as claimed in claim 7, wherein said mobile station further comprises means for setting an initial value P₀ of said transmission power at a predetermined value.

9. The mobile satellite communication system as claimed in claim 7, wherein said means for calculating a transmission power control amount obtains said present transmission power control amount Δ

P_k of said base station by adding said level setting error Δ

S_k to a difference between said reference value R_ref of the received signal level and said corrected average received signal level R_k.

10. The mobile satellite communication system as claimed in claim 7, wherein said means for obtaining said measuring error obtains said measuring error Δ

D_k by dividing a predetermined value C by a square root of said total measuring time t_k.

11. The mobile satellite communication system as claimed in claim 7, wherein said means for obtaining corrected average received signal level obtains said corrected average received signal level R_k by the following equation:

space="preserve" listing-type="equation">R.sub.k ={(R.sub.k-1 +Δ

P.sub.k-1)t.sub.k-1 +Q.sub.k T.sub.k }/t.sub.k -Δ

D.sub.k.

12. A base station in a mobile satellite communication system in which the base station is connected with a mobile station via a communication satellite, said base station comprising:

means for extracting from a received signal an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T, said actual measuring time T_k and said average received signal level Q_k being obtained at said mobile station and transmitted from said mobile station to said base station;

means for calculating a total measuring time t_k which is a sum total of said actual measuring time T_k ;

means for obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

storing means for storing a total measuring time t_k-1, a corrected average received signal level R_k-1 and a transmission power control amount Δ

P_k-1 at the end of a preceding measuring period of said mobile station;

means for obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of said corrected average received signal level R_k-1, said transmission power control amount Δ

P_k-1, said total measuring time t_k-1, said average received signal level Q_k, said actual measuring time T and said total measuring time t_k ;

means for calculating a transmission power control amount Δ

P_k of said base station on the basis of said measuring error Δ

D_k and a difference between said corrected average received signal level R_k and a predetermined reference value R_ref of the received signal level of said mobile station; and

means for obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k.

13. A mobile station in a mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite, said mobile station comprising:

measuring means for obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T; and

transmission means for informing said base station of said actual measuring time T_k and said average received signal level Q_k.

14. A mobile station in a mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite, said mobile station comprising:

measuring means for obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T;

means for calculating a total measuring time t_k which is a sum total of said actual measuring time means for obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

storing means for storing a total measuring time t_k-1 and a corrected average received signal level R_k-1 at the end of a preceding measuring period of said mobile station;

means for extracting a transmission power control amount Δ

P_k-1 from a signal transmitted from said base station to said mobile station;

means for obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of said corrected average received signal level R_k-1, said transmission power control amount Δ

P_k-1, said total measuring time t_k-1, said average received signal level Q_k, said actual measuring time T_k and said total measuring time t_k ; and

transmission means for informing said base station of said corrected average received signal level R_k.

15. A base station in a mobile station in a mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite, said base station comprising:

means for extracting a corrected average received signal level R_k from a received signal sent from said mobile station;

means for calculating a transmission power control amount Δ

P_k of said base station on the basis of a prestored level setting error Δ

S_k and a difference between said corrected average received signal level R_k and a predetermined reference value R_ref of the received signal level of said mobile station;

means for obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k ; and

means for transmitting information on said present transmission power control amount Δ

P_k to said mobile station.

16. A mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite,

said mobile station comprising:

measuring means for obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T; and

transmission means for informing said base station of said actual measuring time T_k and said average received signal level Q_k and

said base station comprising;

means for extracting said actual measuring time T_k and said average received signal level Q_k from a received signal sent from said mobile station;

means for calculating a total measuring time t_k which is a sum total of said actual measuring time T_k ;

means for obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

means for obtaining a total error Δ

E_k by adding said measuring error Δ

D_k to a predetermined level setting error Δ

S_k ;

storing means for storing a total measuring time t_k-1, a corrected average received signal level R_k-1 and a transmission power control amount Δ

P_k-1 at the end of a preceding measuring period of said mobile station;

means for obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of a predetermined reference value R_ref of the received signal level of said mobile station, said total error Δ

E_k, said total measuring time t_k-1, said average received signal level Q_k, said actual measuring time T_k and said total measuring time t_k by the following equation;

space="preserve" listing-type="equation">R.sub.k ={(R.sub.ref +Δ

E.sub.k-1)t.sub.k-1 +Q.sub.k T.sub.k }/t.sub.k

means for calculating a transmission power control amount Δ

P_k of said base station on the basis of said total error Δ

E_k and a difference between said reference value R_ref of the received signal level and said corrected average received signal level R_k ; and

means for obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k.

17. A mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite,

said mobile station comprising:

measuring means for obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T;

means for calculating a total measuring time t_k which is a sum total of said actual measuring time T_k ;

means for obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

storing means for storing a total measuring time t_k-1 and a corrected average received signal level R_k-1 at the end of a preceding measuring period of said mobile station;

means for extracting a transmission power control amount Δ

P_k-1 from a signal transmitted from said base station to said mobile station;

means for obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of a reference value R_ref of the received signal level of said mobile station, a predetermined level setting error Δ

S_k of said base station, said total measuring time t_k-1, said average received signal level Q_k, said actual measuring time T_k and said total measuring time t_k by the following equation;

space="preserve" listing-type="equation">R.sub.k ={(R.sub.ref +Δ

S.sub.k-1)t.sub.k-1 +Q.sub.k T.sub.k }/t.sub.k

transmission means for informing said base station of said corrected average received signal level R_k, and

said base station comprising;

means for extracting said corrected average received signal level R_k from a received signal sent from said mobile station;

means for calculating said transmission power control amount Δ

P_k of said base station on the basis of said level setting error Δ

S_k and a difference between said corrected average received signal level R_k and said predetermined reference value R_ref of the received signal level of said mobile station;

means for obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k ; and

means for transmitting information on said present transmission power control amount Δ

P_k to said mobile station.

18. A transmission power control method in a mobile satellite communication system in which a base station is connected with a mobile station via a communication satellite,

said method comprising the steps of:

obtaining an actual measuring time T_k and an average received signal level Q_k (k=1, 2, . . . ) in a predetermined measuring period T at said mobile station;

calculating a total measuring time t_k which is a sum total of said actual measuring time T_k ;

obtaining a measuring error Δ

D_k of an average received signal level in said total measuring time t_k ;

storing a total measuring time t_k-1, a corrected average received signal level R_k-1 and a transmission power control amount Δ

P_k-1 at the end of a preceding measuring period of said mobile station;

obtaining a corrected average received signal level R_k at the end of a present measuring period of said mobile station on the basis of said corrected average received signal level R_k-1, said transmission power control amount Δ

P_k-1, said total measuring time t_k-1, said average received signal level Q_k, said actual measuring time T_k and said total measuring time t_k ;

calculating a transmission power control amount Δ

P_k of said base station on the basis of said measuring error Δ

D_k and a difference between said corrected average received signal level R_k and a predetermined reference value R_ref of the received signal level of said mobile station; and

obtaining present transmission power P_k from said transmission power control amount Δ

P_k and preceding transmission power P_k-1, and for controlling the transmission power of said base station by said present transmission power P_k.