METHOD AND SYSTEM FOR ADAPTING AN EFFECTIVE SPREADING SEQUENCE IN A COMMUNICATION SYSTEM USING DIRECT SEQUENCE SPREADING

• US 20100166040A1
• Filed: 03/11/2010
• Published: 07/01/2010
• Est. Priority Date: 06/21/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Schotten, Hans Dieter
• Granted Patent: US 8,018,833 B2
• Time in Patent Office: Days
• US Class Current: 375/140
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes

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

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.

14. 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.

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;

$\mathrm{Re}\left(\underset{m}{\sum <br><br>}<br><br>{\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m\right)<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m\right)\right)$

wherein;

Re identifies real part;

j is an imaginary unit;

m is an index;

M is number of phases;

* identifies a complex conjugate;

C_ss(m) is a value of an aperiodic autocorrelation of the effective spreading sequence; and

C_hh(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.

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 C_hh(m);

determine an index m_max>

0 for which a magnitude of the value C_hh(m) attains maximum;

determine a value of an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max);

determine the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max); 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.

4. 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;

$\mathrm{Re}<br><br>\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

5. The apparatus as claimed in claim 3, wherein the determination unit is further configured to:

determine a phase of C_hh(m_max);

determine a phase of C_ss(m_max); and

determine the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max).

6. 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;

${(}^{\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right))$

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

.

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 C_hh(m_max), wherein m_max=m₁−

m₂;

calculate an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determine the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max);

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.

8. 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;

$\mathrm{Re}<br><br>\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

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 C_hh(m_max), wherein m_max=m₁−

m₂;

determine a phase of C_ss(m_max);

determine the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max); 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.

10. 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;

${(}^{\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

11. 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).

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)=e<sup>jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M}$

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.

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<sup>−

jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M}$

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.

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.

28. 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.

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;

$\mathrm{Re}\left(\underset{m}{\sum <br><br>}<br><br>{\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m\right)\right)$

wherein;

Re identifies real part;

j is an imaginary unit;

m is an index;

M is number of phases;

* identifies a complex conjugate;

C_ss(m) is a value of an aperiodic autocorrelation of the effective spreading sequence; and

C_hh(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.

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 C_hh(m);

determining an index m_max>

0 for which a magnitude of the value C_hh(m) attains maximum;

determining a value of an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max); and

applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

18. The computer readable media as claimed in claim 17, wherein said determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that maximizes the expression;

$\mathrm{Re}<br><br>\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

19. The computer readable media as claimed in claim 17, wherein said determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max) comprises:

determining a phase of C_hh(m_max);

determining a phase of C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max).

20. The computer readable media as claimed in claim 19, wherein said determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that minimizes the expression;

${(}^{\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right))$

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

.

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 C_hh(m_max), wherein m_max=m₁−

m₂;

calculating an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max); and

applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

22. The computer readable media as claimed in claim 21, wherein said determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that maximizes the expression;

$\mathrm{Re}<br><br>\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

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 C_hh(m_max), wherein m_max=m₁−

m₂;

determining a phase of C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max); and

applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

24. The computer readable media as claimed in claim 23, wherein said determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that minimizes the expression;

${(}^{\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

25. The computer readable media as claimed in claim 23, wherein said determining the phase of C_hh(m_max) comprises:

determining the phase difference between h(m₁) and h(m₂).

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)=e<sup>jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M}$

is the m-th phase;

α

is a phase factor; and

M is number of phases.

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<sup>−

jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M}$

is the m-th phase;

α

is a phase factor; and

M is the number of phases.

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;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br><br><br>\mathrm{\pi <br><br>}<br><br><br><br>\mathrm{\alpha <br><br>}<br><br><br><br>m}{M};<br><br>$

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.

30. The apparatus as claimed in claim 29, further comprising an evaluator configured to evaluate for each index m an equation:

s′

(m)=e<sup>jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence; and

j is an imaginary unit.

31. The apparatus as claimed in claim 29, further comprising an evaluator configured to evaluate for each index m an equation:

s′

(m)=e<sup>−

jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit.

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.

33. 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 C_hh(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;

$\mathrm{Re}\left(\underset{m}{\sum <br><br>}<br><br>{\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m\right)<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m\right)\right)$

wherein;

Re identifies real part;

j is an imaginary unit;

m is an index;

M is number of phases;

* identifies a complex conjugate;

C_ss(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

.

34. 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 C_hh(m) of the communication channel in accordance with the pre-determined model and the parameters;

determine an index m_max>

0 for which a magnitude of the value C_hh(m) attains maximum;

determine a value of an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determine the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max).

35. 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;

$\mathrm{Re}\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

36. The apparatus as claimed in claim 34, wherein the device is further configured to:

determine a phase of C_hh(m_max);

determine a phase of C_ss(m_max); and

determine the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max).

37. 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;

$\left({\hspace{0.17em}<br><br>}^{\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)\right)$

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

.

38. 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 C_hh(m_max), wherein m_max=m₁−

m₂;

calculate an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determine the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max).

39. 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;

$\mathrm{Re}\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

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 C_hh(m_max), wherein m_max=m₁−

m₂;

determine a phase of C_ss(m_max); and

determine the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max); 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.

41. 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;

$\left({\hspace{0.17em}<br><br>}^{\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)\right)$

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

.

42. The apparatus as claimed in claim 40, wherein said device is further configured to:

determine the phase difference between h(m₁) and h(m₂).

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)=e<sup>jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M}$

is the m-th phase;

α

is a phase factor; and

M is number of phases.

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<sup>−

jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M}$

is the m-th phase;

α

is a phase factor; and

M is the number of phases.

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;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M};<br><br>$

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.

46. 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<sup>jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence; and

j is an imaginary unit.

47. 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<sup>−

jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit.

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.

49. 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 C_hh(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;

$\mathrm{Re}\left(\underset{m}{\sum <br><br>}<br><br>{\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m\right)<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m\right)\right)$

wherein;

Re identifies real part;

j is an imaginary unit;

m is an index;

M is number of phases;

* identifies a complex conjugate;

C_ss(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

.

50. 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 C_hh(m) of the communication channel in accordance with the pre-determined model and the parameters;

determining an index m_max>

0 for which a magnitude of the value C_hh(m) attains maximum;

determining a value of an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max).

51. The computer readable media as claimed in claim 50, wherein said determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that maximizes the expression;

$\mathrm{Re}\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

52. The computer readable media as claimed in claim 50, wherein said determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max) comprises:

determining a phase of C_hh(m_max);

determining a phase of C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max).

53. The computer readable media as claimed in claim 52, wherein said determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that minimizes the expression;

$\left({\hspace{0.17em}<br><br>}^{\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)\right)$

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

.

54. 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 C_hh(m_max), wherein m_max=m₁−

m₂;

calculating an aperiodic autocorrelation of an effective spreading sequence C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max).

55. The computer readable media as claimed in claim 54, wherein said determining the plurality of linearly related phases in accordance with the C_hh(m_max) and the C_ss(m_max) comprises:

determining a value of a phase shift factor α

that maximizes the expression;

$\mathrm{Re}\left({\mathrm{<br><br>}}^{\frac{j<br><br><br><br>2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)·<br><br>C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)$

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

.

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 C_hh(m_max), wherein m_max=m₁−

m₂;

determining a phase of C_ss(m_max); and

determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max); and

applying at least one of the plurality of linearly related phases to at least one sample of the effective spreading sequence.

57. The computer readable media as claimed in claim 56, wherein said determining the plurality of linearly related phases in accordance with the phases of C_hh(m_max) and the C_ss(m_max) comprise:

determining a value of a phase shift factor α

that minimizes the expression;

$\left({\hspace{0.17em}<br><br>}^{\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m_{\max }}{M}}<br><br>+\mathrm{arc}<br><br>\left(C_{\mathrm{ss}}<br><br>\left(m_{\max }\right)\right)+\mathrm{arc}<br><br>\left(C_{\mathrm{hh}}^{*}<br><br>\left(m_{\max }\right)\right)\right)$

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

.

58. The computer readable media as claimed in claim 56, wherein said determining the phase of C_hh(m_max) comprises:

determining the phase difference between h(m₁) and h(m₂).

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)=e<sup>jθ

(m)</sup>·

s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M}$

is the m-th phase;

α

is a phase factor; and

M is number of phases.

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<sup>−

jθ

(m)</sup>s(m)

wherein;

s′

(m) is the adapted spreading sequence;

s(m) is the effective spreading sequence;

j is an imaginary unit;

$\mathrm{\theta <br><br>}<br><br>\left(m\right)=\frac{2<br><br>\mathrm{\pi <br><br>\alpha <br><br>}<br><br><br><br>m}{M}$

is the m-th phase;

α

is a phase factor; and

M is the number of phases.