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

• US 20020048261A1
• Filed: 04/13/2001
• Published: 04/25/2002
• Est. Priority Date: 04/14/2000
• Status: Active Grant

• Current Assignee: Alcatel SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Valtolina, Roberto, Pellizzoni, Roberto, Spalvieri, Arnaldo, Brioschi, Massimo
• Granted Patent: US 7,274,715 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• 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 comprises 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 said first and said second analog signals to obtain a first digital signal and a second digital signal, respectively; c) sending said 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 comprising the steps of:

receiving a first analog signal;

receiving at least one further analog signal;

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

sending said digital signals to respective equalizers;

wherein said method further comprises the step of

delaying in a digital manner one of said first digital signal and said at least one further digital signal by a period equal to an integer multiple of the sampling period, and possibly the further step of

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

2. A method according to claim 1, wherein the delaying step comprises the step of calculating, in an automatic manner, the value of the integer multiple, wherein said step of calculating the integer multiple in turn comprises the steps of:

realizing delayed replicas

r_1j(kT_sa)=s₁(kT_sa−

jT_sa) and r_2i(kT_sa)=s₂(kT_sa−

iT_sa)

of said first and said at least a further 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 further signal and, similarly, N₂T_sa the maximum assumable delay of the at least one further signal with respect to the first signal;

calculating cross-correlations

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

 

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

} the time average operation;

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 it further comprises the step of 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 claims 1 to 3 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 claims 1 to 3 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 further analog signal;

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

equalizers receiving said digital signals at the input;

wherein said apparatus further comprises;

means for delaying in a digital manner one of said first digital signal and said at lest one further digital signal by a period equal to an integer multiple of the sampling period, and equalizer means capable of restoring the difference between an imposed delay and the effective one.

5. An apparatus according to claim 4, wherein said delay means comprise means for calculating, in an automatic manner, the value of the integer multiple, wherein said automatic calculation means in turn comprise

means for realizing delayed replicas

r_1j(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 further 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 further signal and, analogously, N₂T_sa the maximum assumable delay of the at least one further signal with respect to the first signal;

means for calculating cross-correlations

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

 

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, wherein it further comprises 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.