Slowing the observed rate of channel fluctuations in a multiple antenna system
View Patent ↗A method and apparatus for reducing the observed rate of change of the channel characteristics in a system with multiple antennas at a mobile terminal. The slowing down of the observed channel fluctuations is effectuated on the downlink by either calculating or receiving signals that have a similar Doppler shift, referred to herein as Doppler-compensatable signals, and processing one or more of the Doppler-compensatable signals to compensate for Doppler shift. The slowing down of the observed channel fluctuations is effectuated on the uplink by pre-compensating symbol streams with the Doppler shift associated with the direction in which they are transmitted, so that the observed Doppler shift of these signals when they are received is reduced or even eliminated.
1. A method for use in a wireless communication device having at least two receive antennas, the method comprising the steps of:
receiving a first received signal on a first receive antenna;
receiving a second received signal on a second receive antenna; and
separately processing each one of the received signals to compensate each signal for its Doppler effects.
2. The invention of claim 1 , wherein:
the receive antennas are directional antennas such that the received signals are directional signals; and
the processing step comprises compensating each of the directional signals for its Doppler effects.
3. The invention of claim 2 , wherein:
each of the directional antennas covers a range of angles; and
the range of angles of any one of the directional receive antennas does not completely overlap with the range of angles of any of the other of the directional antennas.
4. The invention of claim 1 , wherein the processing step comprises the steps of:
calculating at least two directional signals using the received signals; and
compensating each of the calculated directional signals for its Doppler effects.
5. The invention of claim 4 , wherein the calculating step comprises calculating at least as many directional signals as there are receive antennas.
6. The invention of claim 4 , wherein each calculated directional signal corresponds to a respective angle range and is a composition of the signals that arrive from the corresponding angle range.
7. The invention of claim 1 , wherein:
each received signal comprises at least two transmit signals representing information of a data stream; and
each of the at least two transmit signals were concurrently transmitted over respective different transmit antennas of a second wireless communication device.
8. A wireless communication device comprising:
a first receive antenna adapted to receive a first received signal;
a second receive antenna adapted to receive a second received signal; and
a compensation module coupled to the receive antennas, the compensation module adapted to process each of the received signals to compensate each signal for its Doppler effects.
9. The invention of claim 8 , wherein:
the receive antennas are directional antennas such that the received signals are directional signals; and
the compensation module comprises a Doppler-compensation module adapted to compensate each of the directional signals for its Doppler effects.
10. The invention of claim 9 , wherein:
each of the directional antennas covers a range of angles; and
the range of angles of any one of the directional receive antennas does not completely overlap with the range of angles of any of the other of the directional antennas.
11. The invention of claim 8 , wherein the compensation module comprises:
a beam-forming module adapted to receive the received signals, the beam-forming module being adapted to calculate at least two directional signals using the received signals; and
a Doppler-compensation module adapted to receive the calculated directional signals, the Doppler-compensation module adapted to compensate each of the calculated directional signals for its Doppler effects.
12. The invention of claim 11 , wherein the beam-forming module is further adapted to calculate at least as many formed directional signals are there are the receive antennas.
13. The invention of claim 11 , wherein each calculated directional signal corresponds to a respective angle range and is a composition of the signals that arrive from the corresponding angle range.
14. The invention of claim 8 , wherein:
each received signal comprises at least two transmit signals representing information of a data stream; and
each of the at least two transmit signals were concurrently transmitted over respective different transmit antennas of a second wireless communication device.
15. A method for use in a wireless communication device, the method comprising the steps of:
separately processing signals to pre-compensate for Doppler effects associated with each signal; and
transmitting the signals over a transmit antenna to produce one or more directional signals.
16. The invention of claim 15 , wherein the transmit antenna is a directional transmit antenna.
17. The invention of claim 15 , wherein the transmit antenna is a phased-array antenna.
18. The invention of claim 15 , wherein the number of directional signals is at least equal to the number of transmit antennas.
19. A wireless communication device for transmitting a directional signal, the wireless communication device comprising:
a Doppler-pre-compensation module adapted to separately process input signals to pre-compensate each input signal for Doppler effects; and
a transmit antenna adapted for transmitting the directional signal, the directional signal being a function of the Doppler compensated input signals.
20. The invention of claim 19 , wherein the transmit antenna is a directional transmit antenna.
21. The invention of claim 19 , wherein the transmit antenna is a phased-array antenna.
22. The invention of claim 19 , wherein the number of directional signals is at least equal to the number of transmit antennas.
23. A method for use in a wireless communication device having at least two receive antennas, the method comprising the steps of:
receiving a first received signal on a first receive antenna;
receiving a second received signal on a second receive antenna; and separately processing each one of the received signals to compensate each signal for its Doppler effects, the processing step further comprising the steps of:
calculating at least two signals using the received signals, each of the calculated signals having a Doppler shift range, the Doppler shift range being a proper subset of a combined Doppler shift range of the received signals; and
compensating at least one of the calculated signals for its respective Doppler effect.
24. The invention of claim 23 , wherein the calculating step comprises calculating at least as many directional signals as there are receive antennas.
25. The invention of claim 23 , wherein the calculating step comprises the step of multiplying the received signals by
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ω n is the n th Doppler shift, and
A nm is the amplitude weight applied to the received signal received over the m th antenna with the n th Doppler shift.
26. A wireless communication device comprising:
a first receive antenna adapted to receive a first received signal;
a second receive antenna adapted to receive a second received signal; and
a compensation module coupled to the receive antennas, the compensation module adapted to process each of the received signals to compensate each signal for its Doppler effects, the compensation module comprising:
a beam-forming module adapted to receive the received signals, the beam-forming module being adapted to calculate at least two signals using the received signals, each of the calculated signals corresponds to a Doppler shift range that is a proper subset of a combined Doppler shift range of the received signals; and
a Doppler-compensation module adapted to compensate at least one of the calculated signals for its respective Doppler effect.
27. The invention of claim 26 , wherein the beam-forming module is further adapted to calculate at least as many formed directional signals are there are receive antennas.
28. The invention of claim 26 , wherein the beam-forming module comprises a multiplier having an input coupled to outputs of the receive antennas and having an output coupled to an input of the Doppler compensation module, the multiplier adapted to multiply a particular one of the received signals by
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where:
R is the number of the receive antennas;
φ m (ω n ) is the phase shift of the received signal on the m th antenna for an n th Doppler shift,
ω n is the n th Doppler shift, and
A nm is the amplitude weight applied to the received signal received over the m th antenna with the n th Doppler shift.