System and method for data distribution in VHF/UHF bands

• US 9,124,476 B2
• Filed: 08/28/2012
• Issued: 09/01/2015
• Est. Priority Date: 10/03/2008
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Inventors: Wu, Shiquan, Yee, Jung
• Primary Examiner(s): Taha, Shaq
• Application Number:
  US13/596,982
• Publication Number:
  US 20120320897A1
• Time in Patent Office: 1,099 Days
• Field of Search: 370/230
• US Class Current: 1/1
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/26265 Arrangements for sidelobes suppression specially adapted to multicarrier systems, e.g. spectral precoding
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Whitespace devices can use unused television frequencies for transmission and reception of WiFi OFDM signals. Three contiguous bands, such as former channels 2, 3, and 4, may be bonded together to define a whitespace band. In order to fit a WiFi OFDM signal into this whitespace band, a whitespace device compresses the bandwidth of each WiFi OFDM signal using a specific spectrum mask. Very low transmission power is needed for the modified WiFi OFDM signals, eliminating the need for high power amplifiers and most of the WiFi OFDM designs such as PHY and MAC can be reused with minor modifications.

Claims

1. A method of transmitting user data within a communication band, over a local area network (LAN), comprising:

identifying in the communication band a whitespace band available in an area of operation of the LAN;

generating a baseband WiFi orthogonal frequency division multiplexing (OFDM) signal from user data;

reconfiguring the baseband WiFi OFDM signal into a modified WiFi OFDM signal using a transmit spectrum mask that defines the bandwidth of the modified WiFi OFDM signal in the whitespace band and attenuates the modified WiFi OFDM signal at the edges of the whitespace band for maintaining a performance of any neighboring licensed primary service, wherein the bandwidth of the modified WiFi OFDM signal is based at least in part on whether the whitespace band is in a first portion of the communication band or not in the first portion; and

transmitting the modified WiFi OFDM signal over the whitespace band.

2. The method of claim 1

wherein when the whitespace band is in the first portion of the communication band, the bandwidth occupied by the modified WiFi OFDM signal is 16.25 MHz, and

when the whitespace band is not in the first portion of the communication band, the bandwidth occupied by the modified WiFi OFDM signal is 13 MHz.

3. The method of claim 2, wherein the first portion of the communication band includes digital TV channels 2-4.

4. The method of claim 1, wherein the bandwidth occupied by the modified WiFi OFDM signal is 16.25 MHz when the whitespace band is in the first portion of the communication band.

5. The method of claim 4, wherein the transmit spectrum mask has a plateau of 18 MHz around a central frequency to enable a maximum amplitude for the modified WiFi OFDM signal and an attenuation of −

99 dB over 6 MHz from edges of the plateau.

6. The method of claim 5, wherein the transmit spectrum mask includes sharp attenuations of −

36 dB at the edges of the plateau over 500 kHz.

7. The method of claim 4, wherein the modified WiFi OFDM signal has a symbol duration of 4 μ

s, including 3.2 μ

s as a useful signal duration and 0.8 μ

s as a guard interval duration.

8. The method of claim 7, wherein the modified WiFi OFDM signal has a subcarrier spacing of 312.5 kHz.

9. The method of claim 4, wherein the modified WiFi OFDM signal includes a data rate of 54 Mbps.

10. The method of claim 1, wherein the bandwidth occupied by the modified WiFi OFDM signal is 13 MHz when the whitespace band is not in the first portion of the communication band.

11. The method of claim 10, wherein the transmit spectrum mask has a plateau of 18 MHz around a central frequency to enable a maximum amplitude for the modified WiFi OFDM signal and an attenuation of −

99 dB over 6 MHz from edges of the plateau.

12. The method of claim 11, wherein the transmit spectrum mask includes sharp attenuations of −

36 dB at the edges of the plateau over 500 kHz.

13. The method of claim 10, wherein the modified WiFi OFDM signal has a symbol duration of 5 μ

s, including 4 μ

s as a useful signal duration and 1 μ

s as a guard interval duration.

14. The method of claim 13, wherein the modified WiFi OFDM signal has a subcarrier spacing of 250 kHz.

15. The method of claim 10, wherein the modified WiFi OFDM signal includes a data rate of 43.2 Mbps.

16. The method of claim 1, wherein the modified WiFi OFDM signal is modulated over 48 data carriers and uses 4 pilot carriers in the whitespace band.

17. The method of claim 1, wherein the whitespace band extends over a band around a central frequency in a portion of the spectrum allocated to digital TV between 54 MHz and 698 MHz.

18. A transmitter that broadcasts user data over a local area network (LAN) within a whitespace band in a communication band, where the whitespace band is not currently used in an area of operation of the LAN for transmission of licensed primary services, comprising:

a baseband generator configured to generate a baseband WiFi orthogonal frequency division multiplexing (OFDM) signal from the user data;

a frequency converter configured to reconfigure the baseband WiFi OFDM signal into a modified WiFi OFDM signal using a transmit spectrum mask that defines the bandwidth of the modified WiFi OFDM signal in the whitespace band and to attenuate the modified WiFi OFDM signal at the edges of the whitespace band for maintaining a performance of any neighboring licensed primary service, wherein the bandwidth of the modified WiFi OFDM signal is based at least in part on whether the whitespace band is in a first portion of the communication band or not in the first portion; and

a transmitter configured to transmit the modified WiFi OFDM signal over the whitespace band.

19. The transmitter of claim 18, wherein when the whitespace band is in the first portion of the communication band, the bandwidth occupied by the modified WiFi OFDM signal is 16.25 MHz, and

when the whitespace band is not in the first portion of the communication band, the bandwidth occupied by the modified WiFi OFDM signal is 13 MHz.

20. The transmitter of claim 19, wherein the first portion of the communication band includes digital TV channels 2-4.

21. The transmitter of claim 18, wherein the bandwidth occupied by the modified WiFi OFDM signal is 16.25 MHz when the whitespace band is in the first portion of the communication band.

22. The transmitter of claim 21, wherein the transmit spectrum mask has a plateau of 18 MHz around a central frequency to enable a maximum amplitude for the modified WiFi OFDM signal and an attenuation of −

99 dB over 6 MHz from edges of the plateau.

23. The transmitter of claim 22, wherein the transmit spectrum mask includes sharp attenuations of −

36 dB at the edges of the plateau over 500 kHz.

24. The transmitter of claim 21, wherein the modified WiFi OFDM signal has a symbol duration of 4 μ

s, including 3.2 μ

s as a useful signal duration and 0.8 μ

s as a guard interval duration.

25. The transmitter of claim 24, wherein the modified WiFi OFDM signal has a subcarrier spacing of 312.5 kHz.

26. The transmitter of claim 21, wherein the modified WiFi OFDM signal includes a data rate of 54 Mbps.

27. The transmitter of claim 18, wherein the bandwidth occupied by the modified WiFi OFDM signal is 13 MHz when the whitespace band is not in the first portion of the communication band.

28. The transmitter of claim 27, wherein the transmit spectrum mask has a plateau of 18 MHz around a central frequency to enable a maximum amplitude for the modified WiFi OFDM signal and an attenuation of −

99 dB over 6 MHz from edges of the plateau.

29. The transmitter of claim 28, wherein the transmit spectrum mask includes sharp attenuations of −

36 dB at the edges of the plateau over 500 kHz.

30. The transmitter of claim 27, wherein the modified WiFi OFDM signal has a symbol duration of 5 μ

s, including 4 μ

s as a useful signal duration and 1 μ

s as a guard interval duration.

31. The transmitter of claim 30, wherein the modified WiFi OFDM signal has a subcarrier spacing of 250 kHz.

32. The transmitter of claim 27, wherein the modified WiFi OFDM signal includes a data rate of 43.2 Mbps.

33. The transmitter of claim 18, wherein the modified WiFi OFDM signal is modulated over 48 data carriers and uses 4 pilot carriers in the whitespace band.

34. The transmitter of claim 18, wherein the whitespace band extends over a band around a central frequency in a portion of the spectrum allocated to digital TV between 54 MHz and 698 MHz.