Centroid tracking for spread-spectrum communications

• US 6,721,301 B2
• Filed: 01/18/2001
• Issued: 04/13/2004
• 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., Ozluturk, Fatih M.
• Primary Examiner(s): Yao, Kwang Bin
• Application Number:
  US09/765,016
• Publication Number:
  US 20020044539A1
• Time in Patent Office: 1,181 Days
• Field of Search: 370/320, 370/328, 370/329, 370/335, 370/342, 370/441, 370/479, 375/130, 375/140, 375/142, 375/143, 375/145, 375/147, 375/149, 375/150, 375/152
• 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 13/004 : 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

An improvement for a method and system for tracking a spreading code, used in a code division multiple access (CDMA) system. An input signal has spread-spectrum modulation. The spreading code embedded in the spread-spectrum modulation has a plurality of chips. The input signal is sampled, and half-chip offset samples are formed from the sampled input signal. An even set of the half-chip offset samples are grouped into an early set of samples, and an odd set of the half-chip offset samples are grouped into a late set of samples. Each early set of samples is multiplied by spreading codes c(n+1), c(n+2), . . . , c(n+L), to generate a first plurality of products. L is approximately equal to the number of chips of delay between the earliest and latest multipath signals. A first plurality of sums and magnitudes are computed from the first plurality of products. The first plurality of magnitudes are multiplied by a first plurality of weights, to generate a first plurality of weighted-signal values. The first plurality of weighted-signal values are summed to generate an early signal-energy value. Each late set of samples is multiplied by spreading codes c(n−1), c(n−2), . . . , c(n−L), to generate a second plurality of products. A second plurality of sums and magnitudes are computed from the second plurality of products. The second plurality of magnitudes are multiplied by a second plurality of weights, to generated a second plurality of weighted-signal values. The second plurality of weighted-signal values are summed to generate a late signal-energy value. A difference is calculated between the early signal-energy value and the late signal-energy value, thereby producing an error signal.

Claims

1. An improvement for tracking a spreading code in a multipath environment generating a plurality of multipath signals, used in a code division multiple access (CDMA) tracking circuit, the improvement comprising:

an analog-to-digital converter for sampling an input signal having spread-spectrum modulation, with the spreading code embedded in the spread-spectrum modulation having a plurality of chips, with the analog-to-digital converter forming half-chip offset samples and grouping an even set of the half-chip offset samples into an early set of samples, and alternatively grouping an odd set of the half-chip offset sample into a late set of samples;

a first correlation-bank, adaptive-matched filter, coupled to said analog-to-digital converter, for multiplying each early set of samples by the spreading code c(n+1), c(n+2), . . . , c(n+L), where L is small compared to the length of the spreading code and approximately equal to the number of chips of delay between the earliest and latest multipath signals, thereby generating a first plurality of products;

a first sum-and-dump bank, coupled to said first correlation bank, adaptive-matched filter, for computing a first plurality of sums from the first plurality of products, respectively;

a first plurality of calculators, coupled to said first sum-and-dump bank, for calculating a first plurality of magnitudes from the first plurality of sums, respectively;

a first plurality of weighted amplifiers, coupled to said first plurality of calculators, for multiplying the first plurality of magnitudes by a first plurality of weights, to generate a first plurality of weighted-signal values, respectively;

a first summer, coupled to said first plurality of weighted amplifiers, for summing the first plurality of weighted-signal values to generate a first early signal-energy value, respectively;

a second correlation-bank, adaptive-matched filter, coupled to said analog-to-digital converter, for multiplying each late set of samples by the spreading code c(n−

1), c(n−

2), . . . , c(n−

L), thereby generating a second plurality of products;

a second sum-and-dump bank, coupled to said second correlation bank, adaptive-matched filter, for computing a second plurality of sums from the second plurality of products, respectively;

a second plurality of calculators, coupled to said second sum-and-dump bank, for calculating a second plurality of magnitudes from the second plurality of sums, respectively;

a second plurality of weighted amplifiers, coupled to said second plurality of calculators, for multiplying the second plurality of magnitudes by a second plurality of weights, to generate a second plurality of weighted-signal values, respectively;

a second summer, coupled to said second plurality of weighted amplifiers, for summing the second plurality of weighted-signal values to generate a late signal-energy value; and

a subtractor, coupled to said first summer and to said second summer, for calculating a difference between the early signal-energy value and the late signal-energy value, thereby producing an error signal.

2. An improvement for tracking a spreading code in a multipath environment generating a plurality of multipath signals, used in a code division multiple access (CDMA) tracking circuit, the improvement comprising the steps of:

sampling an input signal having spread spectrum modulation, with the first spreading code embedded in the spread-spectrum modulation having a plurality of chips;

forming half-chip offset samples from the sampled input signal;

grouping an even set of the half-chip offset samples into an early set of samples;

grouping, alternatively, an odd set of the half-chip offset samples into a late set of samples;

multiplying each early set of samples by the spreading code c(n+1), c(n+2), . . . , c(n+L), where L is small compared to the length of the spreading code and approximately equal to the number of chips of delay between the earliest and latest multipath signals, thereby generating a first plurality of products;

computing a first plurality of sums from the first plurality of products, respectively;

calculating a first plurality of magnitudes from the first plurality of sums, respectively;

multiplying the first plurality of magnitudes by a first plurality of weights, to generate a first plurality of weighted-signal values, respectively;

summing the first plurality of weighted-signal values to generate an early signal-energy value;

multiplying each late set of samples by the spreading code c(n−

1), c(n−

2), . . . , c(n−

L), thereby generating a second plurality of products;

computing a second plurality of sums from the second plurality of products, respectively;

calculating a second plurality of magnitudes from the second plurality of sums, respectively;

multiplying the second plurality of magnitudes by a second plurality of weights, to generate a second plurality of weighted-signal values, respectively;

summing the second plurality of weighted-signal values to generate a late signal-energy value; and

calculating a difference between the early signal-energy value and the late signal-energy value, thereby producing an error signal.

3. An improvement for tracking a spreading code in a multipath environment generating a plurality of multipath signals, used in a code division multiple access (CDMA) tracking circuit, the improvement comprising:

sampling means for sampling an input signal having spread-spectrum modulation, with the spreading code embedded in the spread-spectrum modulation having a plurality of chips, with said sampling means forming half-chip offset samples and grouping an even set of the half-chip offset samples into an early set of samples, and alternatively grouping an odd set of the half-chip offset samples into a late set of samples;

first correlation means for multiplying each early set of samples by the spreading code c(n+1), c(n+2), . . . , c(n+L), where L is small compared to the spreading code length and approximately equal to a number of chips of delay between the earliest and latest multipath signals, thereby generating a first plurality of products;

first sum-and-dump means for computing a first plurality of sums from the first plurality of products, respectively;

first calculator means for calculating a first plurality of magnitudes from the first plurality of sums, respectively;

a first multiplying means for multiplying the first plurality of magnitudes by a first plurality of weights, to generate a first plurality of weighted-signal values, respectively;

first summer means for summing the first plurality of weighted-signal values to generate an early signal-energy value;

second correlation means for multiplying each late set of samples by the spreading code c(n−

1), c(n−

2), . . . , c(n−

L), thereby generating a second plurality of products;

second sum-and-dump means for computing a second plurality of sums from the second plurality of products, respectively;

second calculator means for calculating a second plurality of magnitudes from the second plurality of sums, respectively;

second multiplying means for multiplying the second plurality of magnitudes by a second plurality of weights, to generate a second plurality of weighted-signal values, respectively;

second summer means for summing the second plurality of weighted-signal values to generate a late signal-energy value; and

subtractor means for calculating a difference between the early signal-energy value and the late signal-energy value, thereby producing an error signal.