Telecommunications – Receiver or analog modulated signal frequency converter – Measuring or testing of receiver
Reexamination Certificate
1999-02-22
2002-08-20
Chin, Vivian (Department: 2745)
Telecommunications
Receiver or analog modulated signal frequency converter
Measuring or testing of receiver
C455S226200, C455S067700
Reexamination Certificate
active
06438362
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to measurement method and apparatus for measuring characteristics of a radio-wave, in particular, to a measurement technique for measuring a desired-signal power, an interference-signal power, and/or an SIR (signal-to-interference power ratio) in, for example, a diversity combining receiver/transceiver.
2. Description of the Related Art
A prior art of the SIR measuring method is disclosed by the following article:
“An Investigation on SIR Measurement Methods in Adaptive Transmit Power Control for DS-CDMA” by S. Seo, Y. Okumura and T. Dohi, Proc. Communications Society, The Institute of Electronics, Information and Communication Engineers (IEICE), B-330, pp. 331, 1996.
The above article describes an SIR measurement method. In the method, a desired-signal power is obtained from a square of an average value of the envelope of a received signal resulted from the diversity reception within a predetermined symbol-period, while an interference-signal power is obtained as a variance of the average value of the envelope of the diversity reception signal within a predetermined symbol-period. Then, SIR is calculated by obtaining a ratio between these signal powers. However, the method needs complicated calculation to obtain the desired-signal power and the interference-signal power. Since, furthermore, the desired-signal power is estimated as an averaged value of the received signal, the power cannot be measured with high accuracy. A problem in this method will be briefly described below.
A signal r
1
received at a receiver channel
1
and a signal r
2
received at a receiver channel
2
can be written as:
r
1
=
s
1
+
i
1
(1)
r
2
=
s
2
+
i
2
(2)
where s
1
, s
2
and i
1
, i
2
respectively represent the values of the desired-signal amplitude and the interference-signal amplitude contained in the received signals r
1
and r
2
.
Combining r
1
and r
2
, using a maximal-ratio combining method, gives:
s
1
(
s
1
+
i
1
)+
s
2
(
s
2
+
i
2
)=
s
1
{circumflex over ( )}2
+s
2
{circumflex over ( )}2
+s
1
*
i
1
+
s
2
*
i
2
. (3)
where “{circumflex over ( )}2” denotes a square.
Now assume that i
1
{circumflex over ( )}2=i
2
{circumflex over ( )}2=N
0
and the average values of i
1
and i
2
are equal to zero. The desired-signal power S′ and the interference-signal power I′ appearing in the article cited above are then given by the expressions:
S
′=(
s
1
{circumflex over ( )}2
+s
2
{circumflex over ( )}2){circumflex over ( )}2 (4)
I
′=(
s
1
{circumflex over ( )}2
+s
2
{circumflex over ( )}2)*
N
0
(5)
Hence, the signal-to-interference power ratio (SIR) can be written as:
S′/I
′=(
s
1
{circumflex over ( )}2
+s
2
{circumflex over ( )}2)/
N
0
(6)
However, S′ and I′ calculated above do not represent the respective actual or real values of the desired-signal power and the interference-signal power. The following calculation must be therefore performed in order to obtain the actual values:
S=sqrt
(
S
′) (7)
I=I′/sqrt
(
S
′) (8)
where “sqrt” denotes a square root.
Thus, this method requires complicated calculations to arrive at the actual values S and I for the desired-signal power and the interference-signal power, respectively.
It should be also noted that an averaging treatment over a long symbol-period is employed for obtaining an interference-signal power with high accuracy in the method described in the above-mentioned article. Since, however, the interference-signal power I′ in Eq.(8) contains a time-varying term (s
1
{circumflex over ( )}2+s
2
{circumflex over ( )}2), the accuracy of the measurement will be reduced even with the long-period averaging. In order to avoid such problem, the desired-signal power S and the interference-signal power I must be determined exactly. It follows that the method has a drawback of requiring complicated calculations as mentioned above.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide method and apparatus for measuring radio-wave characteristics such as an SIR with high accuracy through a simple calculation process.
To achieve the above object, the present invention provides, in a first aspect, a method for measuring characteristics of a propagated radio-wave on the basis of a reference signal, wherein the reference signal is obtained by receiving and demodulating the propagated radio-wave. The method comprises the steps of: (1) within a signal-processing channel, estimating characteristics of a propagation-path through which the radio wave has transmitted, on the basis of the reference signal, and (2) determining radio-wave characteristics on the basis of the estimated characteristics.
The present invention further provides, in a second aspect, a method comprising the steps of: (1) within a signal-processing channel, estimating characteristics of a propagation-path through which the radio wave has transmitted, on the basis of the reference signal, (2) determining a first radio-wave characteristic on the basis of the estimated characteristics, and (3) within the respective signal-processing channels, calculating a difference value between the estimated characteristics and the reference signal so as to obtain a second radio-wave characteristic.
The present invention also provides, in a third aspect, a method further comprising the step of deriving a third radio-wave characteristic from the radio-wave characteristics calculated in the respective signal-processing channels.
In a further aspect, the present invention provides either a receiver or a transceiver that performs either one of the foregoing methods.
REFERENCES:
patent: 5574984 (1996-11-01), Reed et al.
patent: 5787338 (1998-07-01), Priest
patent: 5903554 (1999-05-01), Saints
patent: 6034952 (2000-03-01), Dohl
An Investigation on SIR Measurement Methods in Adaptive Transmit Power Control for DS-CDMA. Shunsuke SEO et al., 1996 NTT Mobile Communications Network Inc. (6 pages).
Adaptive RAKE Receiver for Mobile Communications. Yukitoshi Sanada et al., FEICE Trans. Commun., vol. E76-B., No. 8, Aug. 1993 pp. 1002-1007.
Chin Vivian
Moore James K
Oki Electric Industry CO Ltd.
Rabin & Berdo P.C.
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