Adaptive vector correlator for spread-spectrum communications

• US 6,697,350 B2
• Filed: 01/18/2001
• Issued: 02/24/2004
• Est. Priority Date: 06/30/1995
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Lomp, Gary R.
• Primary Examiner(s): Yao, Kwang Bin
• Application Number:
  US09/765,256
• Publication Number:
  US 20020036998A1
• Time in Patent Office: 1,132 Days
• Field of Search: 370/320, 370/335, 370/342, 370/449, 370/479, 375/142, 375/143, 375/145, 375/147, 375/148, 375/149, 375/150, 375/151, 375/152, 375/153, 375/340, 375/343, 375/349
• US Class Current: 370/342
• 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 13/10 : 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 multiple access, spread-spectrum communication system processes a plurality of information signals received by a radio carrier station over telecommunication lines for simultaneous transmission over a radio frequency channel as a code-division-multiplexed signal to a group of subscriber units. The radio carrier station receives a call request signal that corresponds to a telecommunication line information signal, and a user identification signal that identifies a user to receive the call. The radio carrier station includes a plurality of CDMA modems, one of which provides a global pilot code signal. The modems provide message code signals synchronized to the global pilot signal. Each modem combines an information signal with a message code signal to provide a code division multiplexed signal. The RCS includes a system channel controller is coupled to receive a remote call. A radio frequency transmitter is connected to all of the modems to combine the code division multiplexed processed signals with the global pilot code signal to generate a code division multiplexed signal. The transmitter also modulates a carrier signal with the code division multiplexed signal and transmits the modulated carrier signal through a radio frequency communication channel to the subscriber units. Each subscriber unit includes a CDMA modem which is also synchronized to the global pilot signal. The CDMA modem despreads the code division multiplexed signal and provides a despread information signal to the user. The system includes a closed loop power control system for maintaining a minimum system transmit power level for the radio carrier station and the subscriber units, and system capacity management for maintaining a maximum number of active subscriber units for improved system performance.

Claims

1. An adaptive vector correlator for estimating channel response and for obtaining a reference value of a plurality of received-multipath signals of a spread-spectrum signal having a pilot-spreading-code signal, comprising:

despreading means for generating a plurality of replicas of the pilot-spreading-code signal, with each of the plurality of replicas of the pilot-spreading-code signal having a different phase, said despreading means for despreading, using the plurality of replicas of the pilot-spreading-code signal, the plurality of received-multipath signals of the spread-spectrum signal as a plurality of despread-multipath signals;

said despreading means for generating a noise-power level when each pilot-spreading-code signal embedded in each of the plurality of received-multipath signals of the spread-spectrum signal is not in phase with any of the plurality of replicas of the pilot-spreading-code signal;

said despreading means for generating one or more detected-pilot signals, when one or more pilot-spreading-code signals embedded in the received-multipath signals of the spread-spectrum signal is in phase with one or more of the plurality of replicas of the pilot-spreading-code signal, respectively;

an adder for combining the one or more detected-pilot signals, as a combined-pilot signal;

channel-response-estimation means, coupled to said despreading means and to said adder, responsive to the one or more detected-pilot signals and the noise-power level and the combined-pilot signal from said adder, for estimating the channel response and thereby generating a channel-response-estimate signal;

correction means, coupled between said despreading means, said channel-response-estimation means and said adder, responsive to the channel-response-estimate signal, for correcting the plurality of despread-multipath signals for effects of the channel response;

acquisition-decision means, coupled to said despreading means and responsive to the one or more detected-pilot signals from said despreading means, for determining whether the one or more detected-pilot signals are synchronized to one or more of the plurality of replicas of the pilot-spreading-code signal;

said acquisition-decision means, responsive to detecting no synchronization, for sending a control signal to said despreading means, for offsetting the phase of the one or more of the plurality of replicas of the pilot-spreading-code signals; and

said acquisition-decision means, responsive to detecting synchronization, for maintaining synchronization between the plurality of received-multipath signals and the plurality of replicas of the pilot-spreading-code signal.

2. The adaptive vector correlator as set forth in claim 1, with said despreading means including:

a code generator for generating the plurality of replicas of the pilot-spreading-code signal;

a plurality of correlators, coupled to said code generator, with each correlator using one of the plurality of a replicas of the pilot-spreading-code signal, said plurality of correlators for correlating the spread-spectrum signal with the plurality of replicas of the pilot-spreading-code signal;

said plurality of correlators thereby generating the noise-power level when each pilot-spreading-code signal embedded in each of the plurality of received-multipath signals of the spread-spectrum signal is not in phase with any of the plurality of replicas of the pilot-spreading-code signal; and

said plurality of correlators for generating one or more detected-pilot signals and the noise-power level, when one or more pilot-spreading-code signals embedded in the received-multipath signals of the spread-spectrum signal is in phase with one or more of the plurality of replicas of the pilot-spreading-code signal, respectively.

3. The adaptive vector correlator as set forth in claim 1, with said despreading means including a plurality of correlators for correlating the spread-spectrum signal with a plurality of phases of the plurality of replicas of the pilot-spreading-code signal, respectively.

4. The adaptive vector correlator as set forth in claim 2, with said despreading means including a plurality of correlators for correlating the spread-spectrum signal with a plurality of phases of the plurality of replicas of the pilot-spreading-code signal, respectively.

5. The adaptive vector correlator as set forth in claim 1 or 2, with said adder including means for adding the one or more detected-pilot signals as a combined-pilot signal.

6. The adaptive vector correlator as set forth in claim 3, with said adder including means for adding the one or more detected-pilot signals as a combined-pilot signal.

7. The adaptive vector correlator as set forth in claim 4, with said adder including means for adding the one or more detected-pilot signals as a combined-pilot signal.

8. An adaptive vector correlator for estimating channel-impulse response and for obtaining a reference value of a plurality of received multipath signals of a spread-spectrum signal having a pilot-spreading-code signal, comprising:

a code generator for generating a plurality of replicas of the pilot-spreading-code signal, with each of the plurality of replicas of the pilot-spreading-code signal having a different phase;

a plurality of correlators, coupled to said code generator, for despreading, using the plurality of replicas of the pilot-spreading-code signal, the plurality of received-multipath signals of the spread-spectrum signal as a plurality of despread-multipath signals;

said plurality of correlators for generating a noise-power level when each pilot-spreading-code signal embedded in each of the plurality of received-multipath signals of the spread-spectrum signal is not in phase with any of the plurality of replicas of the pilot-spreading-code signal;

said plurality of correlators for generating one or more detected-pilot signals, when one or more pilot-spreading-code signals embedded in the received-multipath signals of the spread-spectrum signal is in phase with one or more of the plurality of replicas of the pilot-spreading-code signal, respectively;

an adder for combining the one or more detected-pilot signals, as a combined-pilot signal;

a channel-response estimator, responsive to the one or more detected-pilot signals and the noise-power level and the combined-pilot signal, for estimating a channel response and thereby generating a channel-response-estimate signal;

a correction circuit, coupled between said plurality of correlators, said channel-response estimator and said adder, responsive to the channel-response-estimate signal, for correcting the plurality of despread-multipath signals for effects of the channel response;

an acquisition-decision circuit, coupled to said plurality of correlators and responsive to the one or more detected-pilot signals from said plurality of correlators, for determining whether the one or more detected-pilot signals are synchronized to one or more of the plurality of replicas of the pilot-spreading-code signal;

said acquisition-decision circuit, responsive to detecting no synchronization, for sending a control signal to said plurality of correlators, for offsetting phase of one or more of the plurality of replicas of the pilot-spreading-code signals; and

said acquisition-decision circuit, responsive to detecting synchronization, for maintaining synchronization between the plurality of received-multipath signals and the plurality of replicas of the pilot-spreading-code signal.

9. The adaptive vector correlator as set forth in claim 8, with said adder including means for adding the one or more detected-pilot signals, as a combined-pilot signal.

10. An adaptive vector correlation method for estimating channel-impulse response and for obtaining a reference value of a plurality of received multipath signals of a spread-spectrum signal having a pilot-spreading code signal, comprising the steps of:

generating a plurality of replicas of the pilot-spreading-code signal, with each of the plurality of replicas of the pilot-spreading-code signal having a different phase;

despreading, using the plurality of replicas of the pilot-spreading-code signal, the plurality of received-multipath signals of the spread-spectrum signal as a plurality of despread-multipath signals;

generating a noise-power level when each pilot-spreading-code signal embedded in each of the plurality of received-multipath signals of the spread-spectrum signal is not in phase with any of the plurality of replicas of the pilot-spreading-code signal;

generating one or more detected-pilot signals, when one or more pilot-spreading-code signals embedded in the received-multipath signals of the spread-spectrum signal is in phase with one or more of the plurality of replicas of the pilot-spreading-code signal, respectively;

combining the one or more detected-pilot signals, as a combined-pilot signal;

estimating, from the one or more detected-pilot signals and the noise-power level, a channel response and thereby generating a channel-response-estimate signal;

correcting, in response to the channel-response-estimate signal, the plurality of despread-multipath signals for effects of the channel response;

determining, from the one or more detected-pilot signals, whether the one or more detected-pilot signals are synchronized to one or more of the plurality of replicas of the pilot-spreading-code signal;

sending, in response to detecting no synchronization, a control signal for offsetting phase of the one or more of the plurality of replicas of the pilot-spreading-code signals; and

maintaining, in response to detecting synchronization, synchronization between the plurality of received-multipath signals and the plurality of replicas of the pilot-spreading-code signal.

11. The adaptive vector correlator method as set forth in claim 10, with the step of combining including the step of adding the one or more detected-pilot signals, as a combined-pilot signal.