Adaptive matched filter and vector correlator for a code division multiple access (CDMA) modem

• US 5,991,332 A
• Filed: 02/17/1998
• Issued: 11/23/1999
• Est. Priority Date: 06/30/1995
• Status: Expired due to Term

• Current Assignee: Altralight, Inc., EGO Elektro-Gerã¤Tebau GmbH (EGO Blanc und Fischer & Company GmbH)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Ozluturk, Fatih, Lomp, Gary, Silverberg, Avi
• Primary Examiner(s): Le, Amanda T.
• Application Number:
  US09/024,473
• Time in Patent Office: 644 Days
• Field of Search: 375/200, 375/207, 375/208, 375/210, 375/343, 375/346, 375/349, 375/350, 370/320, 370/335, 370/342, 370/479, 370/491
• US Class Current: 375/152
• CPC Class Codes: G06F 13/374 using a self-select method with individual priority code comparator
• CPC Class Codes: H03H 17/0226 comprising look-up tables
• CPC Class Codes: H03H 17/06 Non-recursive filters
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70753 Partial phase search
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70755 Setting of lock conditions, e.g. threshold
• CPC Class Codes: H04B 1/70758 Multimode search, i.e. using multiple search strategies
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/711 the interference being multi-path interference
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/70707 : Efficiency-related aspects
• CPC Class Codes: H04B 2201/7071 : with dynamic control of receiver resources
• CPC Class Codes: H04B 7/2628 : using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04B 7/2637 : for logical channel control
• CPC Class Codes: H04B 7/264 : for data rate control
• CPC Class Codes: H04J 13/00 : Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/004 : Orthogonal
• CPC Class Codes: H04J 13/0048 : Walsh
• CPC Class Codes: H04J 13/0077 : Multicode, e.g. multiple codes assigned to one user
• CPC Class Codes: H04J 13/10 : Code generation
• CPC Class Codes: H04J 13/107 : by concatenation
• CPC Class Codes: H04J 13/12 : Generation of orthogonal codes
• CPC Class Codes: H04J 13/16 : Code allocation
• CPC Class Codes: H04J 2013/0037 : Multilevel codes
• CPC Class Codes: H04L 1/0001 : Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/004 : by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0042 : Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 1/0047 : Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286
• CPC Class Codes: H04L 1/0054 : Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0059 : Convolutional codes
• CPC Class Codes: H04L 2027/003 : at baseband only
• CPC Class Codes: H04L 2027/0053 : Closed loops
• CPC Class Codes: H04L 25/0212 : of impulse response
• CPC Class Codes: H04L 27/206 : using a pair of orthogonal carriers, e.g. quadrature carriers
• CPC Class Codes: H04L 27/2332 : using a non-coherent carrier
• CPC Class Codes: H04L 5/1446 : of transmission speed
• CPC Class Codes: H04N 1/00912 : Arrangements for controlling a still picture apparatus or components thereof not otherwise provided for
• CPC Class Codes: H04N 1/3333 : during transmission, input or output of the picture signal; within a single document or page
• CPC Class Codes: H04N 2201/3335 : Speed or rate
• CPC Class Codes: H04W 52/04 : TPC
• CPC Class Codes: H04W 52/08 : Closed loop power control
• CPC Class Codes: H04W 52/143 : Downlink power control
• CPC Class Codes: H04W 52/146 : Uplink power control
• CPC Class Codes: H04W 52/24 : using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/241 : taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/245 : taking into account received signal strength
• CPC Class Codes: H04W 52/247 : where the output power of a terminal is based on a path parameter sent by another terminal
• CPC Class Codes: H04W 52/26 : using transmission rate or quality of service QoS [Quality of Service]
• CPC Class Codes: H04W 52/262 : taking into account adaptive modulation and coding [AMC] scheme AMC per se H04L1/0001
• CPC Class Codes: H04W 52/322 : Power control of broadcast channels
• CPC Class Codes: H04W 52/325 : Power control of control or pilot channels
• CPC Class Codes: H04W 52/343 : taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 : distributing total power among users or channels
• CPC Class Codes: H04W 52/36 : with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/367 : Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/44 : in connection with interruption of transmission
• CPC Class Codes: H04W 52/50 : at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 52/52 : using AGC [Automatic Gain Control] circuits or amplifiers
• CPC Class Codes: H04W 52/54 : Signalisation aspects of the TPC commands, e.g. frame structure
• CPC Class Codes: H04W 52/60 : using different transmission rates for TPC commands
• CPC Class Codes: Y02D 10/00 : Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A CDMA modem includes a modem transmitter having: a code generator which provides an associated pilot code signal and which generates a plurality of message code signals: a spreading circuit which produces a spread-spectrum message signal by combining each of the information signals with a respective one of the message code signals; and a global pilot code generator that provides a global pilot code signal to which the message code signals are synchronized. The CDMA modem also includes a modem receiver having an associated pilot code generator and a group of associated pilot code correlators for correlating code-phase delayed versions of the associated pilot signal with a receive CDM signal to produce a despread associated pilot signal. The code phase of the associated pilot signal is changed responsive to an acquisition signal value until a pilot signal is received. The associated pilot code tracking logic adjusts the associated pilot code signal in phase responsive to the acquisition signal so that the signal power level of the despread associated pilot code signal is maximized. Finally, the CDMA modem receiver includes a group of message signal acquisition circuits, each including a plurality of receive message signal correlators which correlate respective local received message code signal to the CDM signal to produce a respective despread received message signal.

Claims

1. An adaptive matched filter (AMF) for collecting signal power of a spread data channel in a spread-spectrum communication system from a spread signal having a plurality of multipath signal components, each of the multipath signal components having a carrier phase, wherein the spread signal includes a spread pilot channel employing a first predetermined spreading code sequence and a spread data channel employing a second predetermined spreading code sequence different from the first predetermined spreading code sequence, the spread pilot channel is unmodulated and the spread data channel is data-modulated;

the AMF comprising;

pilot vector correlator means, coupled to receive the spread signal, for determining a plurality of multipath signal weighting values from a plurality of multipath signal carrier components of the spread pilot channel, each multipath signal weighting value corresponding to, and derived from, a respective multipath signal carrier component, the pilot vector correlator means comprising;

a) local pilot code sequence generator means for generating a plurality of local code sequences, each of the code sequences being a code phase-shifted version of the pilot spreading code sequence;

b) a plurality of pilot spreading code correlators, each pilot spreading code correlator correlating a respective one of the local code sequences with the spread signal, each spreading code correlator comprising i) combining means for combining the spread signal with the respective one of the local code sequences to produce a correlated pilot signal value and ii) accumulator means for accumulating the correlated pilot signal value for a predetermined period to produce a despread multipath pilot signal component having a carrier signal phase;

c) filter means including a plurality of lowpass filters, wherein each one of the plurality of despread multipath pilot signal components is applied to a respective one of the plurality of low pass filters to produce a respective multipath signal weighting value corresponding to the carrier signal phase of the respective received multipath signal component;

wherein, one of the plurality of despread multipath pilot signal components and a respective one of the multipath signal weighting value is applied to a respective one of a plurality of multipliers; and

each multipath pilot signal component is multiplied by the respective one of the multipath signal weighting values to produce a respective scaled and phase rotated pilot signal component of a plurality of scaled and phase rotated pilot signal components having substantially equal carrier phases; and

d) pilot component combining means for combining the plurality of weighted pilot signal components to produce a pilot data value; and

local code sequence generator means for generating a plurality of local code sequences, each of the local code sequences being a code phase-shifted version of the second predetermined spreading code sequence;

data AMF means, coupled to receive the spread signal, for providing a data value determined from the spread data channel, the data AMF means comprising;

a) a plurality of spreading code correlators for despreading all multipath data signal components, each spreading code correlator correlating a respective one of the local code sequences with the received spread signal to produce a respective despread multipath data signal component having a carrier phase value;

b) a plurality of weighting means for scaling the respective multipath data signal components in magnitude and for aligning the carrier phase value of the despread multipath data signal component responsive to the respective multipath weighting value; and

c) data component combining means for combining all of the scaled and aligned multipath data signal components to produce the data value.

2. The data AMF apparatus of claim 1, wherein:

each of the plurality of spreading code correlators further includes i) multiplication means for multiplying the spread signal with a respective one of the local code sequences to produce a correlated signal value and ii) accumulation means for accumulating the correlated signal value for a predetermined period to produce a despread multipath data signal component having a carrier phase which corresponds to the carrier signal phase of the respective received multipath signal component; and

the weighting means comprises a plurality of multipliers, each multiplier multiplying a respective one of the despread multipath data signal components with a respective one of the multipath signal weighting values, and each multiplier producing one scaled and aligned multipath data signal component.

3. A pilot vector correlator apparatus for collecting signal power of a spread pilot channel of a received spread signal, the spread signal having a plurality of received multipath signal components and the spread pilot channel being spread by a predetermined spreading code sequence, to produce a pilot data value and to provide a plurality of multipath signal weighting values determined from the spread pilot channel;

the apparatus comprising;

local pilot code sequence generator means for generating a plurality of local code sequences, each of the local code sequences being a code phase-shifted version of the pilot spreading code sequence;

a plurality of pilot spreading code correlators, each pilot spreading code correlator correlating a respective one of the local code sequences with the spread signal, each spreading code correlator comprising i) a multiplier which multiplies the spread signal by a respective one of the local code sequences to produce a correlated pilot signal value, and ii) accumulator means for accumulating the correlated signal for a predetermined period to produce a despread multipath pilot signal component having a respective carrier signal phase value;

filter means including a plurality of lowpass filters, wherein each one of the plurality of despread multipath pilot signal components is applied to a respective one of the plurality of low pass filters to produce a respective one of the plurality of multipath signal weighting values, each multipath signal weighting value corresponding to a carrier signal phase value of the respective received multipath signal component;

complex multiplier means for performing complex multiplication including a plurality of complex multipliers, each complex multiplier coupled to receive a respective one of the plurality of despread multipath pilot signal components and the respective multipath signal weighting value, wherein each multipath pilot signal component is multiplied by the respective weighting value to produce a respective phase rotated pilot signal component of a plurality of phase rotated pilot signal components having substantially equal carrier phase values; and

d) combining means for combining the plurality of phase rotated pilot signal components to produce the pilot data value.

4. The pilot vector correlator apparatus of claim 3, further comprising:

a phase locked loop (PLL) which measures a carrier phase error of the pilot data value and produces a composite carrier phase error signal;

wherein each one of the plurality of despread multipath pilot signal components and the respective multipath signal weighting values is applied to a respective one of a plurality of complex multipliers with the composite phase error signal, wherein each multipath pilot signal component is multiplied by the respective weighting value and the respective phase error signal to produce a respective scaled and phase rotated pilot signal component, thereby to provide each of the plurality of scaled and phase rotated pilot signal components with a substantially equal carrier phase value.

5. A data adaptive matched filter (AMF) apparatus for collecting signal power of a received spread signal, the spread signal having a plurality of multipath signal components, to produce a despread data value, the spread signal including a spread pilot channel and the spread data channel being spread by a predetermined spreading code sequence;

the data AMF apparatus comprising;

pilot vector correlator means for receiving the spread signal and for providing a plurality of multipath signal weighting values determined from the spread pilot channel, each multipath signal weighting value corresponding to the carrier signal phase of a respective received multipath signal component;

clock signal generator means for producing a clock signal;

code sequence generator means for generating a predetermined code sequence signal having a plurality of code chip values and being equivalent to the predetermined spreading code sequence of the spread data channel, said code sequence generator means being coupled to the clock signal generator means for sequentially providing each spreading code value responsive to the clock signal;

a data AMF comprising;

a) a shift register (SR) responsive to the clock signal and having a plurality of stages including a first stage and last stage, said predetermined code sequence signal being applied to the first stage, wherein each stage defines a respective tap, and each tap produces a signal which corresponds to successive ones of the spreading code values;

b) a plurality of signal multipliers, each signal multiplier multiplying a tap output value by a respective one of the plurality of multipath signal weighting values to produce one respective multipath despreading signal value of a plurality of multipath despreading signal values;

c) combining means for combining all of the plurality of multipath despreading signal values to produce a despreading signal;

d) multiplying means for multiplying the spread signal by the despreading signal to produce a despread data signal; and

e) accumulating means for accumulating the despread data signal for a predetermined period to produce the despread data value.

6. A method of collecting signal power of a spread data channel by an adaptive matched filter (AMF) from a spread signal having a plurality of multipath signal components, each of the multipath signal components having a carrier phase value, wherein the spread signal includes a spread pilot channel employing a first predetermined spreading code sequence and a spread data channel employing a second predetermined spreading code sequence different from the first predetermined spreading code sequence, the spread pilot channel is unmodulated and the spread data channel is data-modulated;

the method comprising the steps of;

a) determining a plurality of multipath signal weighting values from a plurality of multipath signal carrier components of the spread pilot channel, each multipath signal weighting value corresponding to, and derived from, a respective multipath signal carrier component, the determining step further comprising;

a1) generating a plurality of local code sequences, each of the code sequences being a code phase-shifted version of the pilot spreading code sequence;

a2) correlating, by a respective one of a plurality of pilot spreading code correlators, each of the plurality of local code sequences with the spread signal by i) combining the spread signal with the local code sequence to produce a respective correlated pilot signal value and ii) accumulating the correlated pilot signal value for a predetermined period to produce a despread multipath pilot signal component having a respective carrier signal phase;

a3) applying each one of the plurality of despread multipath pilot signal components to a respective one of a plurality of low pass filters to produce a multipath signal weighting value corresponding to the carrier signal phase of the respective received multipath signal component;

a4) multiplying each one of the plurality of despread multipath pilot signal components with the respective multipath signal weighting value to form a plurality of scaled and phase rotated pilot signal components having substantially equal carrier phases; and

a5) combining the plurality of weighted pilot signal components to produce a pilot data value; and

b) generating a plurality of local code sequences, each of the local code sequences being a code phase-shifted version of the second predetermined spreading code sequence;

c) correlating all multipath data signal components, by each of a plurality of spreading code correlators, a respective one of the local code sequences with the received spread signal to produce a respective despread multipath data signal component having a carrier phase value;

d) modifying, by a plurality of weighting means, the respective multipath data signal components to scale each carrier phase value of the despread multipath data signal component in magnitude and align the carrier phase value responsive to the respective multipath weighting value; and

f) combining each scaled and aligned data signal component to produce a data value.

7. The method of claim 6, wherein:

the correlating step c) further includes the steps of multiplying the spread signal with a respective one of the local code sequences to produce a correlated signal value, and accumulating the correlated signal value for a predetermined period to produce a despread multipath data signal component having a carrier phase which corresponds to the carrier signal phase of the respective received multipath signal component; and

the modifying step d) includes the steps of multiplying, by respective ones of a plurality of multipliers, of the despread multipath data signal components with a respective one of the multipath signal weighting values, to produce a respective scaled and aligned data signal component.

8. A method of collecting signal power of a spread pilot channel of a received spread signal, the spread signal having a plurality of received multipath signal components and the spread pilot channel being spread by a predetermined spreading code sequence, to produce a pilot data value and to provide a plurality of multipath signal weighting values determined from the spread pilot channel, the method comprising the steps of:

a) generating a plurality of local code sequences, each of the code sequences being a code phase-shifted version of the pilot spreading code sequence;

b) correlating, by a plurality of pilot spreading code correlators, each respective one of the local code sequences with the spread signal, each of the plurality of spreading code correlators multiplying the spread signal by a respective one of the local code sequences to produce a correlated pilot signal value and accumulating the correlated signal values produced by each correlator for a predetermined period to produce a respective plurality of despread multipath pilot signal components having respective carrier signal phase values;

c) filtering each one of the plurality of despread multipath pilot signal components with a respective one of a plurality of low pass filters to produce a respective one of the plurality of multipath signal weighting values, each multipath signal weighting value corresponding to a carrier signal phase value of the respective received multipath signal component;

d) complex multiplying, by a respective one of a plurality of complex multipliers, each multipath pilot signal component by the respective weighting value to produce a respective phase rotated pilot signal component of a plurality of phase rotated pilot signal components having substantially equal carrier phase values; and

e) combining the plurality of phase rotated pilot signal components to produce the pilot data value.

9. The method of collecting signal power of a spread pilot channel as recited in claim 8, further comprising the steps of:

f) measuring, by a phase locked loop (PLL), a carrier phase error of the pilot data value to produce a composite carrier phase error signal; and

g) applying the composite phase error signal to respective ones of a plurality of complex multipliers with the plurality of despread multipath pilot signal components and the respective multipath signal weighting value;

wherein, in the complex multiplying step d), each multipath pilot signal component is complex multiplied by the respective weighting value and the respective phase error signal to produce a respective scaled and phase rotated pilot signal component, thereby to provide the plurality of scaled and phase rotated pilot signal components with a substantially equivalent carrier phase values.