Code division multiple access wireless system with closed loop mode using ninety degree phase rotation and beamformer verification
A wireless communication system ( 10 ). The system comprises a user station ( 12 ). The user station comprises despreading circuitry ( 22 ) for receiving and despreading a plurality of slots received from at least a first transmit antenna (A 12 1 ) and a second transmit antenna (A 12 2 ) at a transmitting station ( 14 ). Each of the plurality of slots comprises a first channel (DPCH) comprising a first set of pilot symbols and a second channel (PCCPCH) comprising a second set of pilot symbols. The user station further comprises circuitry ( 50 ) for measuring a first channel measurement (α 1,n ) for each given slot in the plurality of slots from the first transmit antenna and in response to the first set of pilot symbols in the given slot. The user station further comprises circuitry ( 50 ) for measuring a second channel measurement (α 2,n ) for each given slot in the plurality of slots from the second transmit antenna and in response to the first set of pilot symbols in the given slot. The user station further comprises circuitry ( 52 ) for measuring a phase difference value (φ 2 (n)) for each given slot in the plurality of slots in response to the first channel measurement and the second channel measurement for the given slot and in response to a ninety degree rotation of the given slot relative to a slot which was received by the despreading circuitry immediately preceding the given slot.
1 - 32 . (Canceled).
33 . A method of receiving a signal, comprising the steps of:
receiving a sequence of known signals;
calculating a respective coefficient corresponding to each of the known signals, wherein the phase of each said respective coefficient is rotated by 90 degrees with respect to a next coefficient of the sequence; and
producing a logic signal having a value corresponding to a position in the sequence and to the rotation of said respective coefficient.
34 . A method as in claim 33 , comprising sending the logic signal to a remote base station.
35 . A method as in claim 33 , wherein the known signals are pilot symbols.
36 . A method as in claim 35 , wherein each pilot symbol of the sequence of pilot symbols corresponds to one of an even and an odd time slot.
37 . A method as in claim 36 , wherein the pilot symbols are CDMA pilot symbols, and wherein said each pilot symbol comprises a plurality of pilot symbols in each time slot.
38 . A method as in claim 33 , wherein the step of receiving comprises receiving the known signals from a plurality of antennas of a remote transmitter.
39 . A method as in claim 33 , wherein the step of calculating comprises the steps of:
calculating a channel measurement corresponding to each antenna of a plurality of antennas;
calculating a complex dot product of said channel measurement of each antenna;
determining if a real part of the complex dot product is positive or negative; and
determining if an imaginary part of the complex dot product is positive or negative.
40 . A method as in claim 33 , wherein the position in the sequence is one of an even and an odd time slot.
41 . A method as in claim 40 , wherein said respective coefficient is a phase angle, and wherein a phase angle of an even time slot is rotated 90 degrees with respect to a phase angle of an odd time slot.
42 . A method as in claim 41 , comprising the step of calculating a channel estimate from a remote base station in response to the phase angle.
43 . A method of producing a phase angle, comprising the steps of:
receiving a known signal corresponding to one of an even and an odd time slot;
calculating a measurement having real and imaginary parts corresponding to the known signal;
determining the phase angle is 0 when the real part of the measurement is positive in an even time slot;
determining the phase angle is π when the real part of the measurement is negative in the even time slot;
determining the phase angle is −π/2 when the imaginary part of the measurement is positive in an odd time slot; and
determining the phase angle is π/2 when the imaginary part of the measurement is negative in the odd time slot.
44 . A method as in claim 43 , wherein the known signal is received from a remote wireless transmitter.
45 . A method as in claim 44 , wherein the known signal comprises a pilot symbol.
46 . A method as in claim 43 , comprising the steps of:
determining a coefficient is 0 when the phase angle is 0 or π/2; and
determining the coefficient is 1 when the phase angle is π or −π/2.
47 . A method as in claim 46 , comprising the step of transmitting the coefficient to a remote base station.
48 . A method as in claim 43 , wherein the step of calculating comprises calculating a complex dot product of a first channel measurement and a second channel measurement.
49 . A method as in claim 48 , wherein the first channel measurement corresponds to the known signal received from a first antenna of a remote base station, and wherein the second channel measurement corresponds to the known signal received from a second antenna of the remote base station.
50 . A method as in claim 43 , comprising the step of calculating a channel estimate from a remote base station in response to the phase angle.
51 . A method of calculating an estimated value, comprising the steps of:
receiving at least one channel estimate;
receiving a known signal corresponding to one of an even and odd time slot;
calculating a product of the at least one channel estimate and the known signal, the product having real and imaginary parts;
determining a phase angle is 0 when the real part of the product is positive in an even time slot;
determining the phase angle is π when the real part of the product is negative in the even time slot;
determining the phase angle is −π/2 when the imaginary part of the product is positive in an odd time slot; and
determining the phase angle is π/2 when the imaginary part of the product is negative in the odd time slot.
52 . A method as in claim 51 , comprising the step of averaging a coefficient comprising the phase angle over a plurality of time slots to produce the estimated value.
53 . A method as in claim 52 , comprising the step of producing a corrected channel estimate in response to the at least one channel estimate and the estimated value.
54 . A method as in claim 51 , comprising the steps of:
receiving a phase difference value;
producing a first and a second threshold value in response to the phase difference;
adding the first threshold value to the real part; and
adding the second threshold value to the imaginary part.
55 . A method as in claim 51 , wherein the step of receiving at least one channel estimate comprises receiving a plurality of channel estimates corresponding to communication channels from a plurality of antennas of a remote base station.
56 . A method as in claim 51 , wherein the step of receiving a known signal comprises receiving a weighted multi-slot average of a plurality of known signals.
57 . A method of calculating an estimated value, comprising the steps of:
receiving at least one channel estimate;
receiving a known signal;
calculating a product of the at least one channel estimate and the known signal;
rotating the product by a plurality of phase angles, thereby producing a constellation of values, each value of the constellation of values having real and imaginary parts;
detecting a maximum real part from the real part of each value of the constellation; and
producing the estimated value in response to the maximum real part.
58 . A method as in claim 57 , comprising the step of averaging a coefficient comprising the phase angle over a plurality of time slots to produce a threshold value.
59 . A method as in claim 58 , comprising the step of producing a corrected channel estimate in response to the at least one channel estimate and the threshold value.
60 . A method as in claim 57 , comprising the steps of:
receiving a phase difference value;
producing a plurality of threshold values in response to the phase difference; and
adding the threshold values to respective real parts of the constellation of values.
61 . A method as in claim 57 , wherein the step of receiving at least one channel estimate comprises receiving a plurality of channel estimates corresponding to communication channels from a plurality of antennas of a remote base station.
62 . A method as in claim 57 , wherein the step of receiving a known signal comprises receiving a weighted multi-slot average of a plurality of known signals.