Antenna systems with common overhead for CDMA base stations

• US 20040092291A1
• Filed: 11/03/2003
• Published: 05/13/2004
• Est. Priority Date: 12/11/2000
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Rockstar Bidco LP (Rockstar Consortium Inc.)
• Inventors: Deane, Peter, McGowan, Neil M., Legnain, Abdelgader
• Granted Patent: US 7,953,446 B2
• Time in Patent Office: Days
• US Class Current: 455/562.1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 3/40 with phasing matrix
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

Systems and methods for use in CDMA antenna systems are provided in which signals each having a common overhead component are transmitted on a set of adjacent beams of a sector with a micro-timing offset between signals transmitted on adjacent pairs of beams which is large enough that destructive cancellation substantially does not occur between the pair of beams.

Claims

1. An antenna system for a transmitter comprising:

a plurality of antennas defining a respective plurality of fixed beams which together cover a coverage area;

for each antenna a respective signal generator generating a respective signal comprising a common overhead component common to all the signals;

transceiver circuitry connecting the signal generators to the antennas such that a respective one of the signals is transmitted by each antenna;

wherein the each pair of signals transmitted on an adjacent pair of said antennas has a respective mutual micro-timing offset which is large enough that destructive cancellation substantially does not occur between the pair.

2. An antenna system according to claim 1, implemented for a plurality of coverage areas, each coverage area being a respective sector served by the base station.

3. A system according to claim 1 wherein the transmitter is a CDMA base station, and each signal is a CDMA signal.

4. A system according to claim 2 wherein the transmitter is a CDMA base station, and each signal is a CDMA signal.

5. A system according to claim 4 wherein the respective mutual micro-timing offset is small enough that substantially no signal source ambiguity occurs at a receiver.

6. A system according to claim 4 wherein:

the sector has a sector-specific spreading code, and wherein the respective mutual micro-timing offset between each pair of CDMA signals is realized by applying the sector-specific spreading code with a respective mutual micro-offset.

7. A system according to claim 6 wherein the sector-specific spreading code is a PN code.

8. A system according to claim 7 wherein each mutual micro-offset is at least one chip and less than eight chips.

9. A system according to claim 7 wherein each mutual micro-offset is half a width of a traffic search less than a window/space implemented in a mobile terminal community with the base station.

10. A system according to claim 4 wherein the sector-specific code is a short code having a sector specific offset used to distinguish between other sources using the same short code, and wherein the respective mutual micro-timing offset is small enough that substantially no ambiguity between different sector specific offsets occurs at a receiver in respect of any pair of signals transmitted by adjacent antennas.

11. A system according to claim 10 wherein the short code is of length 2{circumflex over ( 

)}15−

1.

12. A system according to claim 4 wherein:

the sector has a sector-specific spreading code, and wherein the respective mutual micro-timing offset between each pair of CDMA signals is realized by applying the sector-specific spreading code and then applying a mutual micro-timing offset.

13. A system according to claim 4 wherein:

the sector has a sector-specific spreading code, and wherein the respective mutual micro-timing offset between each pair of CDMA signals is realized by applying the micro-timing offset to respective sector-specific spreading code generators.

14. A system according to claim 12 wherein the sector-specific spreading code is a PN code.

15. A system according to claim 4 wherein the common overhead component comprises at least one of pilot channel, sync channel, paging channel, quick paging, advanced access channel and auxiliary pilot.

16. A system according to claim 4 further comprising:

for each active user located within the sector, at a given instant only one of the CDMA signals includes a user-specific traffic component generated by the respective CDMA signal generator.

17. A system according to claim 4 wherein the one of the CDMA signals to include the user-specific traffic component for a given user is identified by analyzing signal strength on reverse links from the user, and selecting the CDMA signal corresponding with the reverse link having a best signal strength.

18. A system according to claim 1 wherein the transceiver circuitry is further adapted to provide transmit frequencies in a manner such that the transmit frequencies include a frequency offset from one another.

19. A system according to claim 18 comprising a beam-forming matrix.

20. A system according to claim 19 wherein the beam-forming matrix is a Butler matrix.

21. A system of claim 18 wherein the frequency offset is chosen to further reduce undesirable effects of signal cancellation.

22. A system according to claim 18 wherein the signals have unique traffic channels.

23. A system according to claim 22 wherein the frequency offset is a multiple other than that of the frame rate.

24. A system according to claim 18 wherein the frequency offset is greater than 30 Hz and less than 120 Hz.

25. A system according to claim 1 further comprising:

means in the transceivers for providing transmit phases that include a time dependent phase offset from one another, wherein the phase offset is chosen to reduce undesirable effects of signal cancellation.

26. A method in a CDMA antenna system comprising transmitting signals each having a common overhead component on a plurality of adjacent beams of a sector with a micro-timing offset between signals transmitted on adjacent pairs of beams which is large enough that destructive cancellation substantially does not occur between the pair of beams.

27. A method according to claim 26 wherein the sector has a sector-specific spreading code, and wherein the respective mutual micro-timing offset between each pair of CDMA signals is realized by applying the sector-specific spreading code with a respective mutual micro-offset.