Method and apparatus for automatic delay compensation in space diversity radio transmissions

• US 7,274,715 B2
• Filed: 04/13/2001
• Issued: 09/25/2007
• Est. Priority Date: 04/14/2000
• Status: Expired due to Fees

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Spalvieri, Arnaldo, Brioschi, Massimo, Valtolina, Roberto, Pellizzoni, Roberto
• Primary Examiner(s): Chan; Wing
• Assistant Examiner(s): Chang; Richard
• Application Number:
  US09/833,666
• Publication Number:
  US 20020048261A1
• Time in Patent Office: 2,356 Days
• Field of Search: 370/516, 370/517, 370/519, 375/229, 375/234, 375/349
• US Class Current: 370/516
• CPC Class Codes: A61P 17/00 Drugs for dermatological disorders
• CPC Class Codes: A61P 17/06 Antipsoriatics
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/0894 using different delays between antennas

Abstract

A method and apparatus is described for the automatic delay compensation in space diversity radio transmissions. The method includes the steps of: a) receiving a first analog signal and a second analog signal, a possible delay being between the first and second signals; b) sampling the first and the second analog signals to obtain a first digital signal and a second digital signal, respectively; c) sending the digital signals to respective equalizers, and the steps of d) digitally delaying one of the first digital signal and the second digital signal by a period equal to an integral multiple of the sampling period, and e) recoverying, at the equalization phase, the residual difference between the imposed delay and the actual one.

Claims

1. A method of compensating for a possible delay between two or more radio transmission paths in space diversity radio transmissions, said method comprises:

receiving a first analog signal;

receiving at least one second analog signal;

sampling said first analog signal and said at least one second analog signal to obtain a first digital signal and at least one second digital signal, respectively, a possible delay being present between the first digital signal and the at least one second digital signal; and

sending said digital signals to respective equalizers;

delaying, in a digital manner, one of said first and second digital signals relative to the other by a period equal to an integer multiple of the sampling period, said delaying comprising automatically calculating a value of said integer multiple, and optionally

recovering, at equalization, the difference between the imposed delay and the real delay.

2. A method according to claim 1, wherein delaying comprises calculating the value of the integer multiple, wherein calculating the integer multiple comprises:

realizing delayed replicas r_lj(kT_sa)=s₁(kT_sa−

jT_sa) and r_2i(kT_sa)=s₂(kT_sa−

iT_sa) of said first and said at least second digital signals, with 0≦

j≦

N₁ and 0≦

i≦

N₂, N₁T_sa being the maximum assumable delay of the first signal with respect to the at least one second signal and N₂T_sa being the maximum assumable delay of the at least one second signal with respect to the first signal;

calculating cross-correlations

$\begin{array}{c}{\mathrm{xc}}_{1<br><br>j=}<br><br><br><br>E<br><br>\left\{\underset{m}{\sum <br><br>}<br><br>\underset{n}{\sum <br><br>}<br><br>a_n<br><br>a_m*g_2*\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{mT}\right)<br><br>g_1<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{nT}-\mathrm{\tau <br><br>}-{\mathrm{jT}}_{\mathrm{sa}}\right)\right\}\\ <br><br>\mathrm{with}<br><br><br><br>0\le <br><br>j\le <br><br>N_1,\\ {\mathrm{xc}}_{2<br><br>i=}<br><br><br><br>E<br><br>\left\{\underset{m}{\sum <br><br>}<br><br>\underset{n}{\sum <br><br>}<br><br>a_m<br><br>a_n*g_1^{*}<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{nT}-\mathrm{\tau <br><br>}\right)<br><br>g_2<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{mT}-{\mathrm{iT}}_{\mathrm{sa}}\right)\right\}\\ <br><br>\mathrm{with}<br><br><br><br>0\le <br><br>i\le <br><br>N_2,\end{array}$

between the various delayed replicated signals, where * denotes the complex conjugate operation and E{·

} the time average operation; and

deriving the maximum value of said cross-correlations as i and j vary, namely

$M=\underset{t,j}{\max }<br><br>\left({<br><br>{\mathrm{xc}}_{1<br><br>j}<br><br>}^p,{<br><br>{\mathrm{xc}}_{2<br><br>i}<br><br>}^p\right)$

said maximum value corresponding to the value of the integer multiple.

3. A method according to claim 2, wherein the method further comprises selecting the delayed replica to be sent to said equalizers as a function of the information related to the maximum of the calculated cross-correlations.

7. A computer program comprising computer program code means adapted to perform all the steps of claim 1 when said program is run on a computer.

8. A computer-readable medium having a program recorded thereon, said computer-readable medium comprising computer program code means adapted to perform all the steps of claim 1 when said program is run on a computer.

4. An apparatus for compensating a delay between two or more radio transmission lines in space diversity radio transmissions, said apparatus comprising:

means for receiving a first analog signal;

means for receiving at least one second analog signal;

means for sampling the first analog signal and the at least one second analog signal to obtain a first digital signal and at least one second digital signal, respectively, a delay being possibly present between the first digital signal and the at least one second digital signal; and

equalizers receiving said digital signals at their respective inputs;

means for delaying, in a digital manner, one of said first and second digital signals relative to the other by a period equal to an integer multiple of the sampling period, said delaying comprising automatically calculating a value of said integer multiple, and

equalizer means capable of restoring the difference between an imposed delay and the real delay.

5. An apparatus according to claim 4, wherein said delay means comprise means for calculating the value of the integer multiple, wherein said calculation means comprise:

means for realizing delayed replicas r_lj(kT_sa)=s₁(kT_sa−

jT_sa) and r_2i(kT_sa)=s₂ (kT_sa−

iT_sa) of said first and said at least one second digital signals, with 0≦

j≦

N₁ and 0≦

i≦

N₂, N₁T_sa being the maximum assumable delay of the first signal with respect to the at least one second signal and N₂T_sa being the maximum assumable delay of the at least one second signal with respect to the first signal;

means for calculating cross-correlations

$\begin{array}{c}{\mathrm{xc}}_{1<br><br>j=}<br><br><br><br>E<br><br>\left\{\underset{m}{\sum <br><br>}<br><br>\underset{n}{\sum <br><br>}<br><br>a_n<br><br>a_m*g_2*\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{mT}\right)<br><br>g_1<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{nT}-\mathrm{\tau <br><br>}-{\mathrm{jT}}_{\mathrm{sa}}\right)\right\}\\ <br><br>\mathrm{with}<br><br><br><br>0\le <br><br>j\le <br><br>N_1,\\ {\mathrm{xc}}_{2<br><br>i=}<br><br><br><br>E<br><br>\left\{\underset{m}{\sum <br><br>}<br><br>\underset{n}{\sum <br><br>}<br><br>a_m<br><br>a_n*g_1^{*}<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{nT}-\mathrm{\tau <br><br>}\right)<br><br>g_2<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{mT}-{\mathrm{iT}}_{\mathrm{sa}}\right)\right\}\\ <br><br>\mathrm{with}<br><br><br><br>0\le <br><br>i\le <br><br>N_2,\end{array}$

between the various delayed replicated signals, where * denotes the complex conjugate operation and E{·

} the time average operation; and

means for deriving a maximum value of said cross-correlations as i and j vary, namely

$M=\underset{i,j}{\max }<br><br>\left({<br><br>{\mathrm{xc}}_{1<br><br>j}<br><br>}^p,{<br><br>{\mathrm{xc}}_{2<br><br>i}<br><br>}^p\right),$

said maximum value corresponding to the value of the integer multiple.

6. An apparatus according to claim 5, further comprising switching means for selecting a proper delayed replica to be sent to said equalizer means as a function of information related to the maximum of the cross-correlations calculated.

9. An apparatus for compensating a delay between two or more radio transmission lines in space diversity radio transmissions, said apparatus comprising:

a first receiver that receives a first analog signal;

a second receiver that receives at least one second analog signal;

a sampling circuit that samples the first analog signal and the at least one second analog signal to obtain a first digital signal and at least one second digital signal, respectively, a delay being possibly present between the first digital signal and the at least one second digital signal;

equalizers that receive said digital signals at their respective inputs;

a digital delay circuit that digitally delays one of said first and second digital signals relative to the other by a period equal to an integer multiple of the sampling period, said delaying comprising automatically calculating a value of said integer multiple, and

a restoring equalizer that restores the difference between an imposed delay and the real delay.

10. An apparatus according to claim 9, wherein said digital delay circuit comprises a calculation circuit for calculating the value of the integer multiple, wherein said calculation circuit:

a delay circuit that realizes delayed replicas r_lj(kT_sa)=s₁(kT_sa−

jT_sa) and r_2i(kT_sa)=s₂(kT_sa−

iT_sa) of said first and said at least one second digital signals, with 0≦

j≦

N₁ and 0i≦

N≦

₂, N₁T_sa being the maximum assumable delay of the first signal with respect to the at least one second signal and N₂T_sa being the maximum assumable delay of the at least one second signal with respect to the first signal;

a correlation circuit that calculates cross-correlations

${\mathrm{xc}}_{1<br><br>j}=E<br><br>\left\{\underset{m}{\sum <br><br>}<br><br>\underset{n}{\sum <br><br>}<br><br>a_n<br><br>a_m*g_2*\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{mT}\right)<br><br>g_1<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{nT}-\mathrm{\tau <br><br>}-{\mathrm{jT}}_{\mathrm{sa}}\right)\right\}<br><br>$ $\mathrm{with}<br><br><br><br>0\le <br><br>j\le <br><br>N_1,<br><br>{\mathrm{xc}}_{2<br><br>i}=E<br><br>\left\{\underset{m}{\sum <br><br>}<br><br>\underset{n}{\sum <br><br>}<br><br>a_m<br><br>a_n*g_1*\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{nT}-\mathrm{\tau <br><br>}\right)<br><br>g_2<br><br>\left({\mathrm{kT}}_{\mathrm{sa}}-\mathrm{mT}-{\mathrm{i<br><br>T}}_{\mathrm{sa}}\right)\right\}<br><br>$ $\mathrm{with}<br><br><br><br>0\le <br><br>i\le <br><br>N_2$

between the various delayed replicated signals, where * denotes the complex conjugate operation and E{·

} the time average operation; and

a maximum value circuit derives a maximum value of said cross-correlations as i and j vary, namely

$M=\underset{i,j}{\max }<br><br>\left({<br><br>{\mathrm{xc}}_{1<br><br>j}<br><br>}^p,{<br><br>{\mathrm{xc}}_{2<br><br>i}<br><br>}^p\right),$

said maximum value corresponding to the value of the integer multiple.

11. An apparatus according to claim 10, further comprising a switch for selecting a proper delayed replica to be sent to said restoring equalizer as a function of information related to the maximum of the cross-correlations calculated.