EP0876002A2
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Pilot interference cancellation for a coherent wireless code division multiple access receiver
Assignee: Nokia of America Corp
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Filing: 1998-04-21
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Granted: —
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Expires: 2018-04-21
Abstract
Abstract A Code-Division Multiple Access (CDMA) receiver is disclosed which removes the pilot signal from the received signal. The pilot signal is defined by its multipath parameters (amplitudes, phase shift and delays) and its signature sequence. Since this information is known at the user's receiver terminal (i.e., handset), the pilot signals of the interfering multipath components of the baseband received signal are detected and removed prior to demodulation of the desired multipath component. The pilot signal may be cancelled prior to or following the data accumulation stage. The pilot signal cancellation can be switched on and off depending on the detected path signal level.
Inventors
- 👤 Howard C. Huang
- 👤 Stephan Ten Brink
- 👤 Chih-Lin I
- 👤 Giovanni Vannucci
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 23:05
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/69; H04B1/707; H04B1/7097; H04B1/7103; H04B1/7107; H04B1/71072; H04B1/711; H04B1/7115; H04B1/7117; H04B1/712; H04B2001/71077; H04B2201/00; H04B2201/69; H04B2201/707; H04B2201/70701; H04B2201/70707; H04B2201/70709
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
134 words
A Code Division Multiple Access (CDMA) receiver for receiving and
demodulating a coherent CDMA signal including at least one user data
channel and a separate pilot channel over a plurality of L ( L > or = 2 )
paths, where the desired data channel is orthogonal to the pilot channel for
a given path, the CDMA receiver comprising L path demodulators, each demodulator for estimating a data channel and a
pilot channel from a CDMA signal received over one of the L paths and for
generating L- 1 cancellation signals each to be used by a specific subtractor
means, and L subtractor means, each subtractor means for subtracting the L -1
cancellation signals produced by different ones of the other L -1 path
demodulators from the CDMA signal associated with that subtractor means.
Claim 2
Dependent Claim
43 words
The CDMA receiver of claim 1 wherein the L- 1 cancellation signals are
reconstructed pilot signals, and where each of the subtractor means is
located prior to its associated demodulator to subtract the reconstructed
pilot signals from the signal inputted to its demodulator.
Claim 3
Dependent Claim
64 words
The CDMA receiver of claim 1 wherein each of the L- 1 cancellation signals
is a pair of correlator-processed reconstructed pilot signals, and where each
of the subtractor means is a pair of subtractors located after a pilot and a
data accumulator of its demodulator, to subtract the pair of correlator-processed
reconstructed pilot signals from the signal outputted from its data
and pilot accumulators.
Claim 4
Dependent Claim
53 words
The CDMA receiver of claim 2 wherein the pilot signals for cancellation are reconstructed using a channel
estimation algorithm which has the latest channel estimates available that
are obtained by a first channel estimation performed over one symbol,and
wherein the demodulator input is obtained by buffering the incoming chip-rate signal
for one symbol.
Claim 5
Dependent Claim
51 words
The CDMA receiver of claim 2 wherein the pilot signals for cancellation are reconstructed using a channel
estimation algorithm whose most recent channel estimate is taken from the
previous symbol interval demodulation and wherein these channel
estimates are used for both reconstructing the pilot signals and
demodulating the previous symbol interval.
Claim 6
Dependent Claim
42 words
The CDMA receiver of claim 4 wherein a subtractor means prior to the first channel estimation over one symbol
cancels out pilot signals reconstructed using a channel estimation algorithm
whose most recent channel estimate is taken from the previous symbol
interval demodulation.
Claim 7
Dependent Claim
31 words
The CDMA receiver of claim 3 wherein the pair of correlator-processed reconstructed pilot signals for cancellation
are obtained using a channel estimation algorithm that has the most recent
channel estimates available.
Claim 8
Dependent Claim
54 words
The CDMA receiver of claim 7 wherein a subtractor means prior to the channel estimation algorithm, whose output
is used for reconstructing the pair of correlator-processed pilot signals,
cancels out a first intermediate result of that component of the pair of
correlator-processed pilot signals which is used for cancellation on the pilot
accumulator signals.
Claim 9
Dependent Claim
35 words
The CDMA receivers of claims 1 including Reconstruction Low-Pass Filters ( RLP ) for reconstructing the pulse shape
of the pilot cancellation signals with respect to the delay times of the other L -1 demodulators.
Claim 10
Dependent Claim
21 words
The CDMA receiver of claim 9 wherein the RLP filter is implemented using a
Finite Impulse Response ( FIR ) filter.
Claim 11
Dependent Claim
19 words
The CDMA receiver of claim 10 wherein the FIR filter is implemented using
a look-up table for the coefficients.
Claim 12
Dependent Claim
16 words
The CDMA receiver of claim 9 wherein the RLP filter is implemented using a
look-up table.
Claim 13
Dependent Claim
34 words
The CDMA receivers of claims 1 including a switch means in each demodulator to switch on/off the generation of the L -1 cancellation signals according to the signal power of its designated
multipath component.
Claim 14
Dependent Claim
19 words
The CDMA receiver of claim 1 wherein the pilot channel is orthogonal to at
least one user signal channel.
Claim 15
Dependent Claim
73 words
The CDMA receiver of claim 1 wherein the pilot channel is non-orthogonal
to the desired user signal channel for a given path and wherein
each demodulator generates the L -1 cancellation signals and an additional
cancellation signal for cancelling out the non-orthogonal pilot signal of its
own multipath component prior to its demodulation, the cancellation of the
non-orthogonal pilot signal occurs by using an additional subtraction in each
of the L subtraction means.
Claim 16
Dependent Claim
17 words
The CDMA receiver of claim 1 wherein the plurality of signal channels are
encoded using Walsh codes.
Claim 17
Dependent Claim
18 words
The CDMA receiver of claim 1 wherein the at least one user uses a plurality
of signal channels.
Claim 18
Dependent Claim
21 words
The CDMA receiver of claim 1 wherein the coherent CDMA signal includes
at least a Q and an I signal channel.
Claim 19
Dependent Claim
28 words
The CDMA receiver of claim 1 being part of a user station of a CDMA
system including at least one base station and a plurality of user stations.
Claim 20
Dependent Claim
28 words
The CDMA receiver of claim 1 being part of a base station of a CDMA
system including at least one base station and a plurality of user stations.
Claim 21
Dependent Claim
24 words
The CDMA receiver of claim 1 including means for channel weighting the output of the subtractor means and means for combining the weighted outputs.
Claim 22
Independent Claim
137 words
A method of operating a Code Division Multiple Access (CDMA) receiver for
receiving and demodulating a coherent CDMA signal including at least one
user data channel and a separate pilot channel over a plurality of L ( L > or
= 2 ) paths, where the desired data channel is orthogonal to the pilot
channel for a given path, the method comprising the steps of: at each of L path demodulators, estimating a data channel and a pilot
channel from a CDMA signal received over one of the L paths and
generating L- 1 cancellation signals each to be used by a specific subtractor
means, and at each of L subtractor means, subtracting the L- 1 cancellation signals
produced by different ones of the other L- 1 path demodulators from the
CDMA signal associated with that subtractor.
Claim 23
Dependent Claim
59 words
The CDMA receiver of claim 1 further comprising switch means for controlling the subtraction of one or more of the L -1
cancellation signals, the subtraction of each of the L -1 cancellation signals
being controlled as a function of a determined threshold level based on a
pilot signal received in the associated data channel signal and variances
thereof.
Claim 24
Dependent Claim
22 words
The CDMA receiver of claim 23 wherein the set of cancellation signals to be
generated and subtracted is given by Eq (6).
References Cited (Backward Citations)
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