Simple and robust digital code tracking loop for wireless communication systems

Patent metadata

Field	Value
Publication number	US-9525455-B2
Application number	US-201213544665-A
Country	US
Kind code	B2
Filing date	Jul 9, 2012
Priority date	Apr 29, 2002
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

A simple and robust CTL is used for time tracking of multipath components of a spread spectrum signal transmitted over a wireless multipath fading channel. A digital code-tracking loop includes despreading early and late data samples by use of a pseudonoise sequence, an error signal output generated by the despreading, and adjustment for a plurality of on-time, early and late samples, a data rate of a control signal provided as a fractional proportion of a data rate of error signals.

First claim

What is claimed is:

1. A digital code-tracking loop comprising:
a despreader for despreading early and late data samples by use of a pseudo noise sequence;
a detector configured to generate an error signal for each set of early and late data samples coherently, wherein the error signal is generated coherently on a condition that a transmitted signal is estimated;
an interpolator for generating the early and late samples of a received signal, wherein the interpolator is adjusted by a control signal either forward or backward by a number samples, wherein the control signal adjusts at a fractional chip rate, where the control signal is generated according to a sign of a sum of a plurality of error signals from the detector;
wherein generating the error signal coherently comprises estimating the transmitted signal by removing modulated data from the despread early samples and despread late samples according to:
S e ( k ) a ( k )* and S l ( k ) a ( k )*,

wherein S e (k) is the despread early signal, S l (k) is the despread late samples, and a(k)* equals the complex conjugate of the estimated transmitted samples; and
the error signal is calculated as:

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wherein N 1 equals a number of despread early and late samples used to calculate the error signal.

2. The digital code-tracking loop of claim 1 , wherein:
the error signals provide timing tracking.

3. The digital code tracking loop of claim 2 , wherein for every N samples, one sample provides an on-time synchronized sample, used for despreading, demodulation and rake combining, the code tracking loop tracking timing and selecting the on-time sample, where N>1.

4. The digital code tracking loop of claim 2 , wherein:
the received signal comprises a plurality of slots of a dedicated physical control channel including 10 symbols, the 10 symbols providing pilot, transmit power control and transport format combination indication (TFCI) bits; and
the code tracking loop is updated every 2 frames.

5. The digital code-tracking loop of claim 1 , wherein the adjustment provides time tracking of multipath component of direct sequence spread spectrum signal over a wireless multipath fading channel.

6. A radio transmission controller implementing a digital code-tracking loop, the radio transmission controller comprising:
a despreading circuit for despreading sets of early and late data samples by use of a pseudo noise sequence;
a detector circuit providing an error signal for each set of early and late data samples coherently, wherein the error signal is generated coherently on a condition that a transmitted signal is estimated;
a control circuit providing a control signal; and
a interpolator circuit providing the sets of early and late samples based on a received signal, wherein the interpolator circuit is adjusted by the control signal either forward or backward by a number of samples, wherein the control signal adjusts at a fractional chip rate, where the control signal is generated according to a sign of a sum of a plurality of error signals from the detector;
wherein generating the error signal coherently comprises estimating the transmitted signal by removing modulated data from the despread early samples and despread late samples according to:
S e ( k ) a ( k )* and S l ( k ) a ( k )*,

wherein S e (k) is of the despread early signal, S l (k) is the despread late samples, and a(k)* equals the complex conjugate of the estimated transmitted samples; and
the error signal is calculated as:

E
r

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(
k
)

=



∑

k
=
1

N
1

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k
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a

Assignees

• Li Bin
• Interdigital Tech Corp

Inventors

• Li Bin

Classifications

• H04B1/7117

  Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers · CPC title

• H04B2001/70706

  using a code tracking loop, e.g. a delay locked loop · CPC title

• H04B1/7115

  Constructive combining of multi-path signals, i.e. RAKE receivers · CPC title

• H04B1/7085 Primary

  using a code tracking loop, e.g. a delay-locked loop · CPC title