Base station, receiving device, mobile terminal, and frequency sharing method

• US 8,086,258 B2
• Filed: 09/10/2008
• Issued: 12/27/2011
• Est. Priority Date: 09/28/2007
• Status: Expired due to Fees

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Fujii, Hiromasa, Yoshino, Hitoshi
• Primary Examiner(s): DEAN, RAYMOND S
• Application Number:
  US12/207,618
• Publication Number:
  US 20090088083A1
• Time in Patent Office: 1,203 Days
• Field of Search: 455/69, 455/522, 370/318
• US Class Current: 455/522
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 52/242 taking into account path loss
• CPC Class Codes: H04W 52/367 Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A disclosed base station is used in a first wireless communication system using a first frequency band that is the same as or adjacent to a second frequency band used by a second wireless communication system, and includes a propagation loss estimation unit configured to estimate propagation loss of a signal in the first frequency band when the signal arrives at a receiving device of the second wireless communication system; a frequency difference calculation unit configured to calculate a frequency difference between the first frequency band and the second frequency band; a maximum transmission power determining unit configured to determine maximum transmission power based on the estimated propagation loss and the calculated frequency difference; and a transmission control unit configured to transmit a signal with transmission power less than or equal to the maximum transmission power determined by the maximum transmission power determining unit.

Claims

1. A base station in a first wireless communication system using a first frequency band that is the same as or adjacent to a second frequency band used by a second wireless communication system, the base station comprising:

a propagation loss estimation unit configured to estimate propagation loss of a signal in the first frequency band when the signal arrives at a receiving device of the second wireless communication system;

a frequency difference calculation unit configured to calculate a frequency difference between the first frequency band and the second frequency band;

a maximum transmission power determining unit configured to determine maximum transmission power based on the propagation loss estimated by the propagation loss estimation unit and the frequency difference calculated by the frequency difference calculation unit; and

a transmission control unit configured to transmit a signal with transmission power less than or equal to the maximum transmission power determined by the maximum transmission power determining unit.

2. The base station as claimed in claim 1, further comprising:

a system information receiving unit configured to receive a frequency restriction signal for restricting the use of a specified frequency band from the receiving device, the frequency restriction signal including an occupied frequency band of the second wireless communication system and a transmission power value of the frequency restriction signal;

wherein the propagation loss estimation unit is configured to estimate the propagation loss based on received power of the frequency restriction signal and the transmission power value in the frequency restriction signal.

3. The base station as claimed in claim 1, wherein

the transmission control unit is configured to transmit a propagation path measuring signal including a transmission power value of the propagation path measuring signal to the receiving device;

and

the maximum transmission power determining unit is configured to determine the maximum transmission power based on the frequency difference calculated by the frequency difference calculation unit and the propagation loss estimated by the receiving device based on received power of the propagation path measuring signal and the transmission power value in the propagation path measuring signal.

7. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on a tilt angle of an antenna to be used for transmission by the base station.

8. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on an allowable interference level of the second wireless communication system.

9. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on a direction in which the receiving device of the second wireless communication system is located.

10. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on receiving antenna directivity of the receiving device of the second wireless communication system.

11. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on antenna directivity of the base station.

12. The base station as claimed in claim 2 or 5, wherein the frequency restriction signal includes an allowable interference level of the second wireless communication system.

13. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on a height at which a transmitting antenna of the base station is located.

14. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on a frequency waveform of a transmission signal, the frequency waveform including a transmit spectrum mask.

15. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on geographical conditions surrounding a geographical location of the base station.

16. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine the maximum transmission power based on whether the base station is located indoors or outdoors.

17. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to use different usage rates of the first frequency band for an inner area and an outer area of a cell covered by the base station, the inner area being closer to the base station and the outer area being further from the base station.

18. The base station as claimed in claim 17, wherein the maximum transmission power determining unit is configured to change the usage rates of the first frequency band according to the amounts of traffic and/or the geographical distribution of users in the inner area, the outer area, and cells covered by other base stations.

19. The base station as claimed in claim 18, wherein the maximum transmission power determining unit is configured to use the distribution of signal-to-interference-plus-noise ratios of the users as the geographical distribution of users.

20. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine a usage rate of the first frequency band based on the determined maximum transmission power.

21. The base station as claimed in claim 1 or 4, wherein the maximum transmission power determining unit is configured to determine a usage rate of the first frequency band based on the amount of traffic in a cell covered by the base station and the amounts of traffic in cells covered by other base stations.

22. The base station as claimed in claim 1 or 4, wherein when multiple frequency bands are available, the maximum transmission power determining unit is configured to select one of the frequency bands for transmission based on a frequency usage rate, system information sent from the second wireless communication system, a transmission power restriction, and propagation loss between the base station and the receiving device.

23. The base station as claimed in claim 22, wherein the maximum transmission power determining unit is configured to select one of the frequency bands based on communication quality or transmission efficiency.

4. A base station in a first wireless communication system using a first frequency band that is the same as or adjacent to a second frequency band used by a second wireless communication system, the base station comprising:

a frequency difference calculation unit configured to calculate a frequency difference between the first frequency band and the second frequency band;

a distance calculation unit configured to calculate a distance between the base station and a receiving device of the second wireless communication system;

a maximum transmission power determining unit configured to determine maximum transmission power based on the frequency difference calculated by the frequency difference calculation unit and the distance calculated by the distance calculation unit; and

a transmission control unit configured to transmit a signal with transmission power less than or equal to the maximum transmission power determined by the maximum transmission power determining unit.

5. The base station as claimed in claim 4, further comprising:

a system information receiving unit configured to receive a frequency restriction signal for restricting the use of a specified frequency band from the receiving device, the frequency restriction signal including an occupied frequency band of the second wireless communication system and a transmission power value of the frequency restriction signal;

wherein the distance calculation unit is configured to calculate the distance between the base station and the receiving device based on received power of the frequency restriction signal and the transmission power value in the frequency restriction signal.

6. The base station as claimed in claim 4, wherein

the transmission control unit is configured to transmit a propagation path measuring signal including a transmission power value of the propagation path measuring signal to the receiving device;

and

the maximum transmission power determining unit is configured to determine the maximum transmission power based on the frequency difference calculated by the frequency difference calculation unit and the distance between the base station and the receiving device calculated by the receiving device based on received power of the propagation path measuring signal and the transmission power value in the propagation path measuring signal.

24. A mobile terminal in a first wireless communication system using a first frequency band that is the same as or adjacent to a second frequency band used by a second wireless communication system, the mobile terminal comprising:

a frequency difference calculation unit configured to calculate a frequency difference between the first frequency band and the second frequency band;

a distance calculation unit configured to calculate a distance between the mobile terminal and a receiving device of the second wireless communication system;

a maximum transmission power determining unit configured to determine maximum transmission power based on the frequency difference calculated by the frequency difference calculation unit and the distance calculated by the distance calculation unit; and

a transmission control unit configured to transmit a signal with transmission power less than or equal to the maximum transmission power determined by the maximum transmission power determining unit.

25. A frequency sharing method performed by a base station in a first wireless communication system using a first frequency band that is the same as or adjacent to a second frequency band used by a second wireless communication system, the method comprising:

a frequency difference calculation step of calculating a frequency difference between the first frequency band and the second frequency band;

a distance calculation step of calculating a distance between a mobile terminal of the first wireless communication system and a receiving device of the second wireless communication system;

a maximum transmission power determining step of determining maximum transmission power based on the frequency difference calculated in the frequency difference calculation step and the distance calculated in the distance calculation step; and

a transmission control step of transmitting a signal with transmission power less than or equal to the maximum transmission power determined in the maximum transmission power determining step.