System and Method for Secondary Communications with Directional Transmission

• US 20090325482A1
• Filed: 10/10/2008
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Kwon, Young Hoon, Soong, Anthony C.K., Zhou, Xiangwei
• Granted Patent: US 8,326,227 B2
• Time in Patent Office: Days
• US Class Current: 455/25
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

System and method for exploiting spatial spectrum holes (SSH) in the time/spectrum/location of wireless resources. A method comprises setting a directional antenna to a first transmission direction, determining a state of a spectrum band in the first transmission direction, transmitting information in the first transmission direction to the receiver in response to determining that the spectrum band state is idle and that the receiver lies within a coverage area of a transmitter, and transmitting the information in the first transmission direction to a first relay in response to determining that the spectrum band state is idle and that the receiver lies without the coverage area of the transmitter.

Claims

1. A method for transmitting information by a transmitter to a receiver, the transmitter having a directional antenna, the method comprising:

(1) setting the directional antenna to a first transmission direction;

(2) determining a state of a spectrum band in the first transmission direction;

(3) transmitting the information in the first transmission direction to the receiver in response to determining that the spectrum band state is idle and that the receiver lies within a coverage area of the transmitter; and

(4) transmitting the information in the first transmission direction to a first relay in response to determining that the spectrum band state is idle and that the receiver lies without the coverage area of the transmitter.

2. The method of claim 1, further comprising, in response to determining that the spectrum band state is busy:

(5) in response to determining that a group of untested transmission directions of the directional antenna is not empty,

(6) selecting an untested transmission direction from the group of untested transmission directions,

(7) determining the state of the spectrum band in the untested transmission direction,

(8) transmitting the information in the untested transmission direction to the receiver in response to determining that the spectrum band state is idle and that the receiver lies within a coverage area of the transmitter, and

(9) transmitting the information in the untested transmission direction to a second relay in response to determining that the spectrum band state is idle and that the receiver lies without the coverage area of the transmitter; and

(10) in response to determining that the group of untested transmission directions is empty, (11) buffering the information.

3. The method of claim 2, further comprising in response to determining that the spectrum band state in the untested transmission direction is busy, (12) repeating the elements (5) and (10).

4. The method of claim 1, wherein the directional antenna is an antenna array, and wherein the setting the directional antenna comprises specifying a set of antenna coefficients.

5. The method of claim 1, wherein the setting the directional antenna comprises selecting one of a plurality of directional antennas.

6. The method of claim 1, wherein the determining that the receiver lies within a coverage area comprises determining that the receiver is listed in a database as being within the coverage area.

7. The method of claim 1, wherein the first relay is listed in a database as being able to relay the information to the receiver.

8. The method of claim 7, wherein the first relay is listed in the database as being able to relay the information to a third relay that is able to relay the information to the receiver.

9. The method of claim 1, wherein the determining the state of the spectrum band comprises examining spectrum band usage restrictions.

10. The method of claim 1, wherein the determining the state of the spectrum band comprises:

filtering a received signal to attenuate signals outside of the spectrum band;

measuring a received energy of the filtered received signal within the spectrum band;

accumulating the measured received energy for a time interval; and

deciding the state of the spectrum band based on a comparison of the accumulated received energy and a threshold.

11. The method of claim 1, wherein a transmission containing the information is assigned a priority class k, and wherein the determining the state of the spectrum band comprises:

determining that the state of the spectrum band is idle in response to determining that no active transmission is taking place;

determining that the state of the spectrum band is idle in response to determining that an active transmission is taking place, the active transmission having a priority class j, wherein priority class j is lower in priority than priority class k; and

determining that the state of the spectrum band is busy in response to determining that an active transmission is taking place, the active transmission having a priority class i, wherein priority class i is greater than or equal in priority to priority class k.

12. The method of claim 1, wherein the transmitting the information in the first transmission direction to the first relay comprises transmitting the information to the receiver using a multi-hop transmission.

13. A method for relaying a transmission by a communications relay having a directional antenna, the method comprising:

determining a receiver from the transmission;

in response to determining that the communications relay is capable of relaying the transmission to the receiver,

setting the directional antenna to a first transmission direction,

determining spectrum band availability in the first transmission direction,

relaying a corresponding transmission directly to the receiver in response to determining that the spectrum band is idle and that the receiver lies within a coverage area of the communications relay, and

relaying the corresponding transmission to a second communications relay in response to determining that the spectrum band is idle and that the receiver lies without the coverage area of the communications relay; and

discarding the transmission in response to determining that the communications relay is not capable of relaying the transmission to the receiver.

14. The method of claim 13, wherein the corresponding transmission comprises information substantially identical to information contained in the transmission but with different control information.

15. The method of claim 13, wherein the determining a receiver comprises decoding the transmission.

16. The method of claim 13, further comprising, in response to determining that the spectrum band is busy:

in response to determining that a group of untested transmission directions of the directional antenna is not empty,

selecting an untested transmission direction from the group of untested transmission directions,

determining spectrum band availability in the untested transmission direction,

relaying the corresponding transmission in the untested transmission direction to the receiver in response to determining that the spectrum band is idle and that the receiver lies within a coverage area of the communications relay, and

relaying the corresponding transmission in the untested transmission direction to a third communications relay in response to determining that the spectrum band is idle and that the receiver lies without the coverage area of the communications relay;

in response to determining that the group of untested transmission directions is empty, buffering the transmission; and

in response to determining that the spectrum band in the untested transmission direction is busy, repeating the in response to determining that a group of untested directions of the directional antenna is not empty and the in response to determining that the group of untested transmission directions is empty.

17. The method of claim 13, wherein the determining that the communications relay is not capable of relaying the transmission to the receiver comprises determining that the receiver is not listed in a database of receivers that the communications relay is capable of making a transmission to.

18. The method of claim 17, wherein the determining that the communications relay is not capable of relaying the transmission to the receiver further comprises determining that a fourth communications relay is not listed in the database, wherein the fourth communications relay is capable of relaying the transmission to the receiver.

19. A communications node comprising:

a receiver coupled to an antenna, the receiver configured to receive signals detected by the antenna;

a transmitter coupled to a directional antenna, the transmitter configured to directionally transmit signals using the directional antenna; and

a processor coupled to the receiver and to the transmitter, the processor configured to sense a state of a spectrum band over which signals are transmitted and received, to relay a received transmission to the received transmission'"'"'s intended receiver or to a relay node capable of relaying the received transmission to the intended receiver, and to generate a database containing transmission relaying information.

20. The communications node of claim 19, wherein the processor comprises:

a spectrum sensing unit configured to sense a state of the spectrum band;

a message relay unit coupled to the spectrum sensing unit, the message relay unit configured to determine if the intended receiver is within a coverage area of a directional transmission of the transmitter by accessing the database, and to select a relay node if the intended receiver is without the coverage area by accessing the database; and

a database generator coupled to the message relay unit, the database generator configured to generate the database based on responses to messages transmitted by the communications node, the database arranged based on a directional transmission of the transmitter.

21. The communications node of claim 20, further comprising a transmission class unit coupled to the message relay unit, the transmission class unit configured to assign a classification to transmissions made by the transmitter, and to determine the state of the spectrum band based on the classification assigned to the transmissions.

22. The communications node of claim 19, wherein the communications node operates in proximity to a communications system having transmission priority over transmissions made by the communications node, the communications node further configured to directionally transmit information to receivers to reduce interference caused on transmissions of the communications system.

23. The communications node of claim 22, wherein the communications system is a licensed communications system, and the communications node is a cognitive radio node.