# US 2010/0166040 A1 · Method and system for adapting an effective spreading sequence in a communication system using direct sequence spreading

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- Number: US 2010/0166040 A1
- Document ID: US20100166040A1
- Status: Published application
- Kind: A1
- Application number: 12/721,840
- Filed: 2010-03-11
- Published: 2010-07-01
- Earliest claimed: 2005-06-21
- Assignees: QUALCOMM Incorporated
- Inventors: Hans Dieter Schotten
- Web page: https://patentgrep.com/patent/US20100166040A1

## CPC

- H04J 13/004: {Orthogonal}
- H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)}
- H04B 1/7097: Interference-related aspects
- H04B 2201/709709: Methods of preventing interference
- H04J 13/18: Allocation of orthogonal codes
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04B: TRANSMISSION

## Abstract

A method and system for adapting an effective spreading sequence in a wire-line or a wireless communication system using direct sequence spreading system is described. A station of the communication system determines a state of a communication channel, represented by, e.g., an impulse response, a step response, or any other characteristic known to one skilled in the art. The station determines the channel state by measurements of a received signal or by receiving a feedback signal comprising an information enabling the station to determine the plurality of linearly related phases The station then determines a plurality of linearly related phases in accordance with the state of the communication channel, and then applies at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

## Claims

### Claim 1

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel, the channel estimation unit configured to:
determine an operating environment of the communication system;
select a pre-determined model for the state of the communication channel in accordance with said determined operating environment;
determine parameters of the pre-determined model in accordance with the state of the communication channel; and
determine the state of the communication channel from the parameters and the pre-determined model; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel and apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to despread a received signal.

### Claim 2

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel, the determination unit configured to:
determine a value of a phase shift factor α that maximizes the expression:
Re
(
∑
m


j


2


π


α


m
M

C
ss

(
m
)

C
hh
*

(
m
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
m is an index;
M is number of phases;
* identifies a complex conjugate;
Css(m) is a value of an aperiodic autocorrelation of the effective spreading sequence; and
Chh(m) is a value of an aperiodic autocorrelation of an impulse response of the communication channel;
determine the plurality of linearly related phases in accordance with the phase shift factor α; and
apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to despread a received signal.

### Claim 3

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel, the determination unit configured to:
calculate for each of a plurality of indexes m a corresponding value of an aperiodic autocorrelation of an impulse response of the communication channel Chh(m);
determine an index mmax>0 for which a magnitude of the value Chh(m) attains maximum;
determine a value of an aperiodic autocorrelation of an effective spreading sequence Css(mmax);
determine the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax); and
apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to despread a received signal.

### Claim 4 (depends on 3)

The apparatus as claimed in claim 3, wherein the determination unit is further configured to:
determine a value of a phase shift factor α that maximizes the expression:
Re

(

j


2


π


α


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 5 (depends on 3)

The apparatus as claimed in claim 3, wherein the determination unit is further configured to:
determine a phase of Chh(mmax);
determine a phase of Css(mmax); and
determine the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax).

### Claim 6 (depends on 5)

The apparatus as claimed in claim 5, wherein the determination unit is further configured to:
determine a value of a phase shift factor α that minimizes the expression:
(
2


π


α


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 7

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel, the determination unit configured to:
determine indexes m1 and m2 for the largest and the second largest magnitudes of an impulse response of the communication channel h(m);
calculate an aperiodic autocorrelation of the impulse response of the communication channel Chh(mmax), wherein mmax=m1−m2;
calculate an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determine the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax);
wherein the determination unit is further configured to apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to despread a received signal.

### Claim 8 (depends on 7)

The apparatus as claimed in claim 7, wherein the determining unit is further configured to:
determine a value of a phase shift factor α that maximizes the expression:
Re

(

j


2


π


α


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 9

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel, the determination unit configured to:
determine indexes m1 and m2 for the largest and the second largest magnitudes of an impulse response of the communication channel h(m);
determine a phase of Chh(mmax), wherein mmax=m1−m2;
determine a phase of Css(mmax);
determine the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax); and
apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to despread a received signal.

### Claim 10 (depends on 9)

The apparatus as claimed in claim 9, wherein the determination unit is further configured to:
determine a value of a phase shift factor α that minimizes the expression:
(
2


π


α


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 11 (depends on 9)

The apparatus as claimed in claim 9, wherein the determining unit is further configured to:
determine the phase difference between h(m1) and h(m2).

### Claim 12

An apparatus for adapting an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel and apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence by evaluating for each index m an equation:
s′(m)=ejθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2


π


α


m
M
is the m-th phase;
α is a phase factor; and
M is number of phases,
and wherein the determination unit is further configured to use the adapted spreading sequence to despread a received signal.

### Claim 13

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a channel estimation unit configured to determine a state of a communication channel; and
a determination unit configured to determine a plurality of linearly related phases in accordance with the state of the communication channel and apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence by evaluating for each index m an equation:
s′(m)=e−jθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2


π


α


m
M
is the m-th phase;
α is a phase factor; and
M is the number of phases,
and wherein the adapted spreading sequence is used to despread a received signal.

### Claim 14 (depends on 1)

The method as claimed in claim 1 wherein the determination unit is further configured to:
transmit a feedback signal comprising said selected pre-determined model; and
transmit a feedback signal comprising said determined parameters.

### Claim 15

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
determining a state of a communication channel which includes:
determining an operating environment of the communication system;
selecting a pre-determined model for the state of the communication channel in accordance with said determined operating environment;
determining parameters of the pre-determined model in accordance with the state of the communication channel; and
determining the state of the communication channel from the parameters and the pre-determined model;
determining a plurality of linearly related phases in accordance with the state of the communication channel; and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 16

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
determining a state of a communication channel;
determining a plurality of linearly related phases in accordance with the state of the communication channel, including:
determining a value of a phase shift factor α that maximizes the expression:
Re
(
∑
m


j


2


π


α


m
M

C
ss

(
m
)
·
C
hh
*

(
m
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
m is an index;
M is number of phases;
* identifies a complex conjugate;
Css(m) is a value of an aperiodic autocorrelation of the effective spreading sequence; and
Chh(m) is a value of an aperiodic autocorrelation of an impulse response of the communication channel; and
determining the plurality of linearly related phases in accordance with the phase shift factor α; and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 17

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
determining a state of a communication channel;
determining a plurality of linearly related phases in accordance with the state of the communication channel, the means including:
calculating for each of a plurality of indexes m a corresponding value of an aperiodic autocorrelation of an impulse response of the communication channel Chh(m);
determining an index mmax>0 for which a magnitude of the value Chh(m) attains maximum;
determining a value of an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax); and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 18 (depends on 17)

The computer readable media as claimed in claim 17, wherein said determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that maximizes the expression:
Re

(

j


2


π


α


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 19 (depends on 17)

The computer readable media as claimed in claim 17, wherein said determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax) comprises:
determining a phase of Chh(mmax);
determining a phase of Css(mmax); and
determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax).

### Claim 20 (depends on 19)

The computer readable media as claimed in claim 19, wherein said determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that minimizes the expression:
(
2


π


α


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 21

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
determining a state of a communication channel;
determining a plurality of linearly related phases in accordance with the state of the communication channel, including:
determining indexes m1 and m2 for the largest and the second largest magnitudes of an impulse response of the communication channel h(m);
calculating an aperiodic autocorrelation of the impulse response of the communication channel Chh(mmax), wherein mmax=m1−m2;
calculating an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax); and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 22 (depends on 21)

The computer readable media as claimed in claim 21, wherein said determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that maximizes the expression:
Re

(

j


2


π


α


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 23

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
determining a state of a communication channel;
determining a plurality of linearly related phases in accordance with the state of the communication channel, including:
determining indexes m1 and m2 for the largest and the second largest magnitudes of an impulse response of the communication channel h(m);
determining a phase of Chh(mmax), wherein mmax=m1−m2;
determining a phase of Css(mmax); and
determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax); and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 24 (depends on 23)

The computer readable media as claimed in claim 23, wherein said determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that minimizes the expression:
(
2


π


α


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 25 (depends on 23)

The computer readable media as claimed in claim 23, wherein said determining the phase of Chh(mmax) comprises:
determining the phase difference between h(m1) and h(m2).

### Claim 26

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
determining a state of a communication channel;
determining a plurality of linearly related phases in accordance with the state of the communication channel;
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence, the means including means for evaluating for each index m an equation:
s′(m)=ejθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2


π


α


m
M
is the m-th phase;
α is a phase factor; and
M is number of phases.

### Claim 27

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, comprising:
determining a state of a communication channel;
determining a plurality of linearly related phases in accordance with the state of the communication channel;
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence, the means including means for evaluating for each index m an equation:
s′(m)=e−jθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2


π


α


m
M
is the m-th phase;
α is a phase factor; and
M is the number of phases.

### Claim 28 (depends on 15)

The computer readable media as claimed in claim 15 further comprising:
transmitting a feedback signal comprising said selected pre-determined model; and
transmitting a feedback signal comprising said determined parameters.

### Claim 29

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a feedback receiver configured to receive a feedback signal comprising a phase factor α and information enabling determination of a plurality of linearly related phases;
a device configured to determine the plurality of linearly related phases in accordance with the feedback by evaluating for each index m an equation:
θ

(
m
)
=
2


π


α


m
M
;
wherein:
M is number of phases; and
a multiplier configured to apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to spread a transmit signal.

### Claim 30 (depends on 29)

The apparatus as claimed in claim 29, further comprising an evaluator configured to evaluate for each index m an equation:
s′(m)=ejθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence; and
j is an imaginary unit.

### Claim 31 (depends on 29)

The apparatus as claimed in claim 29, further comprising an evaluator configured to evaluate for each index m an equation:
s′(m)=e−jθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit.

### Claim 32

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a feedback receiver configured to receive a feedback signal comprising information enabling determination of a plurality of linearly related phases wherein the feedback signal comprises a pre-determined model characterizing the communication channel and at least one parameter of the pre-determined model;
a device configured to determine the plurality of linearly related phases in accordance with the feedback; and
a multiplier configured to apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to spread a transmit signal.

### Claim 33 (depends on 32)

The apparatus as claimed in claim 32, wherein said device configured to determine the plurality of linearly related phases is further configured to:
determine an aperiodic autocorrelation of an impulse response Chh(m) of the communication channel in accordance with the pre-determined model and the parameters;
determine a value of a phase shift factor α that maximizes the expression:
Re
(
∑
m


j


2

πα


m
M

C
ss

(
m
)

C
hh
*

(
m
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
m is an index;
M is number of phases;
* identifies a complex conjugate;
Css(m) is a value of an aperiodic autocorrelation of the effective spreading sequence; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 34 (depends on 32)

The apparatus as claimed in claim 32, wherein said device is further configured to:
calculate for each of a plurality of indexes m a corresponding value of an aperiodic autocorrelation of an impulse response Chh(m) of the communication channel in accordance with the pre-determined model and the parameters;
determine an index mmax>0 for which a magnitude of the value Chh(m) attains maximum;
determine a value of an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determine the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax).

### Claim 35 (depends on 34)

The apparatus as claimed in claim 34, wherein the device is further configured to:
determine a value of a phase shift factor α that maximizes the expression:
Re
(

j


2

πα


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 36 (depends on 34)

The apparatus as claimed in claim 34, wherein the device is further configured to:
determine a phase of Chh(mmax);
determine a phase of Css(mmax); and
determine the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax).

### Claim 37 (depends on 36)

The apparatus as claimed in claim 36, wherein said device is further configured to:
determine a value of a phase shift factor α that minimizes the expression:
(
2

πα


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 38 (depends on 32)

The apparatus as claimed in claim 32, wherein said device is further configured to:
determine an impulse response of the communication channel h(m) in accordance with the pre-determined model and the parameters;
determine indexes m1 and m2 for the largest and the second largest magnitudes of the impulse response of the communication channel h(m);
calculate an aperiodic autocorrelation of the impulse response of the communication channel Chh(mmax), wherein mmax=m1−m2;
calculate an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determine the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax).

### Claim 39 (depends on 38)

The apparatus as claimed in claim 38, wherein said device is further configured to:
determine a value of a phase shift factor α that maximizes the expression:
Re
(

j


2

πα


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 40

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a feedback receiver configured to receive a feedback signal comprising information enabling determination of a plurality of linearly related phases;
a device configured to determine the plurality of linearly related phases in accordance with the feedback, the device configured to:
determine an impulse response of the communication channel h(m) in accordance with the pre-determined model and the parameters;
determine indexes m1 and m2 for the largest and the second largest magnitudes of the impulse response of the communication channel h(m);
determine a phase of Chh(mmax), wherein mmax=m1−m2;
determine a phase of Css(mmax); and
determine the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax); and
a multiplier configured to apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to spread a transmit signal.

### Claim 41 (depends on 40)

The apparatus as claimed in claim 40, wherein said device is further configured to:
determine a value of a phase shift factor α that minimizes the expression:
(
2

πα


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determine the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 42 (depends on 40)

The apparatus as claimed in claim 40, wherein said device is further configured to:
determine the phase difference between h(m1) and h(m2).

### Claim 43

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a feedback receiver configured to receive a feedback signal comprising information enabling determination of a plurality of linearly related phases;
a device configured to determine the plurality of linearly related phases in accordance with the feedback; and
a multiplier configured to apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to spread a transmit signal by evaluating for each index m an equation:
s′(m)=ejθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2

πα


m
M
is the m-th phase;
α is a phase factor; and
M is number of phases.

### Claim 44

An apparatus configured to adapt an effective spreading sequence in a communication system, comprising:
a feedback receiver configured to receive a feedback signal comprising information enabling determination of a plurality of linearly related phases;
an apparatus configured to determine the plurality of linearly related phases in accordance with the feedback; and
a multiplier configured to apply at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence to generate an adapted spreading sequence, wherein the adapted spreading sequence is used to spread a transmit signal by
evaluating for each index m an equation:
s′(m)=e−jθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2

πα


m
M
is the m-th phase;
α is a phase factor; and
M is the number of phases.

### Claim 45

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
receiving a feedback signal comprising information enabling determination of a plurality of linearly related phases, wherein the feedback signal comprises a phase factor α;
determining the plurality of linearly related phases in accordance with the feedback, including
evaluating for each index m an equation:
θ

(
m
)
=
2

πα


m
M
;
wherein:
M is number of phases; and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 46 (depends on 45)

The computer readable media as claimed in claim 45, wherein said applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence comprises:
evaluating for each index m an equation:
s′(m)=ejθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence; and
j is an imaginary unit.

### Claim 47 (depends on 45)

The computer readable media as claimed in claim 45, wherein said applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence comprises:
evaluating for each index m an equation:
s′(m)=e−jθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit.

### Claim 48

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
receiving a feedback signal comprising information enabling determination of a plurality of linearly related phases wherein the feedback signal comprises a pre-determined model characterizing the communication channel; and at least one parameter of the pre-determined model;
determining the plurality of linearly related phases in accordance with the feedback; and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 49 (depends on 48)

The computer readable media as claimed in claim 48, wherein said determining the plurality of linearly related phases comprises:
determining an aperiodic autocorrelation of an impulse response Chh(m) of the communication channel in accordance with the pre-determined model and the parameters;
determining a value of a phase shift factor α that maximizes the expression:
Re
(
∑
m


j


2

πα


m
M

C
ss

(
m
)

C
hh
*

(
m
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
m is an index;
M is number of phases;
* identifies a complex conjugate;
Css(m) is a value of an aperiodic autocorrelation of the effective spreading sequence; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 50 (depends on 48)

The computer readable media as claimed in claim 48, wherein said determining the plurality of linearly related phases comprise:
calculating for each of a plurality of indexes m a corresponding value of an aperiodic autocorrelation of an impulse response Chh(m) of the communication channel in accordance with the pre-determined model and the parameters;
determining an index mmax>0 for which a magnitude of the value Chh(m) attains maximum;
determining a value of an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax).

### Claim 51 (depends on 50)

The computer readable media as claimed in claim 50, wherein said determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that maximizes the expression:
Re
(

j


2

πα


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 52 (depends on 50)

The computer readable media as claimed in claim 50, wherein said determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax) comprises:
determining a phase of Chh(mmax);
determining a phase of Css(mmax); and
determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax).

### Claim 53 (depends on 52)

The computer readable media as claimed in claim 52, wherein said determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that minimizes the expression:
(
2

πα


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 54 (depends on 48)

The computer readable media as claimed in claim 48, wherein said determining the plurality of linearly related phases comprises:
determining an impulse response of the communication channel h(m) in accordance with the pre-determined model and the parameters;
determining indexes m1 and m2 for the largest and the second largest magnitudes of the impulse response of the communication channel h(m);
calculating an aperiodic autocorrelation of the impulse response of the communication channel Chh(mmax), wherein mmax=m1−m2;
calculating an aperiodic autocorrelation of an effective spreading sequence Css(mmax); and
determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax).

### Claim 55 (depends on 54)

The computer readable media as claimed in claim 54, wherein said determining the plurality of linearly related phases in accordance with the Chh(mmax) and the Css(mmax) comprises:
determining a value of a phase shift factor α that maximizes the expression:
Re
(

j


2

πα


m
max
M

C
ss

(
m
max
)
·
C
hh
*

(
m
max
)
)
wherein:
Re identifies real part;
j is an imaginary unit;
M is number of phases;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 56

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
receiving a feedback signal comprising information enabling determination of a plurality of linearly related phases;
determining the plurality of linearly related phases in accordance with the feedback, including
determining an impulse response of the communication channel h(m) in accordance with the pre-determined model and the parameters;
determining indexes m1 and m2 for the largest and the second largest magnitudes of the impulse response of the communication channel h(m);
determining a phase of Chh(mmax), wherein mmax=m1−m2;
determining a phase of Css(mmax); and
determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax); and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

### Claim 57 (depends on 56)

The computer readable media as claimed in claim 56, wherein said determining the plurality of linearly related phases in accordance with the phases of Chh(mmax) and the Css(mmax) comprise:
determining a value of a phase shift factor α that minimizes the expression:
(
2

πα


m
max
M

+
arc

(
C
ss

(
m
max
)
)
+
arc

(
C
hh
*

(
m
max
)
)
)
wherein:
M is number of phases;
arc( ) is a phase of the argument;
* identifies a complex conjugate; and
determining the plurality of linearly related phases in accordance with the phase shift factor α.

### Claim 58 (depends on 56)

The computer readable media as claimed in claim 56, wherein said determining the phase of Chh(mmax) comprises:
determining the phase difference between h(m1) and h(m2).

### Claim 59

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
receiving a feedback signal comprising information enabling determination of a plurality of linearly related phases;
determining the plurality of linearly related phases in accordance with the feedback; and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence, including evaluating for each index m an equation:
s′(m)=ejθ(m)·s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2

πα


m
M
is the m-th phase;
α is a phase factor; and
M is number of phases.

### Claim 60

Computer readable media embodying a method for adapting an effective spreading sequence in a communication system, the method comprising:
receiving a feedback signal comprising information enabling determination of a plurality of linearly related phases;
determining the plurality of linearly related phases in accordance with the feedback; and
applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence including evaluating for each index m an equation:
s′(m)=e−jθ(m)s(m)
wherein:
s′(m) is the adapted spreading sequence;
s(m) is the effective spreading sequence;
j is an imaginary unit;
θ

(
m
)
=
2

πα


m
M
is the m-th phase;
α is a phase factor; and
M is the number of phases.