Base station

Details Base station Base station

2000-02-24

2004-08-31

Duong, Frank (Department: 2732)

Multiplex communications

Communication over free space

Combining or distributing information via code word channels...

C370S348000

Reexamination Certificate

active

06785257

ABSTRACT:

This patent application claims priority based on a Japanese patent application, H11-046729 filed on Feb. 24, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a code division multiple access base station and in particular to a code division multiple access base station and which can process a signal wave having a long delay time.
2. Description of the Related Art
To deal with the variation of the delay time of a received signal, the conventional code division multiple access (CDMA) base station measures the delay profile of a transmission path from a received signal. The delay profile is the response of a signal wave transmitted through different transmission paths received at a base station. Because the signal wave transmits through different paths, the waveform of the signal wave is transformed by the influence of each transmission path. The conventional CDMA base station then selects a plurality of peaks having an effective power level and synthesizes the selected peak to demodulate the received signal.
FIG. 1
shows a configuration of a CDMA base station. A CDMA base station has an antenna
10
, a receiving unit
12
, a RACH signal receiver
14
, a DCH signal receiver
16
, and a controller
26
. The RACH signal receiver
14
has a delay profile measuring unit
18
and a demodulator
20
. The DCH signal receiver
16
has a delay profile measuring unit
22
and a demodulator
24
.
The antenna
10
receives a random access channel (PACH) signal and a data channel (DCH) signal which are spread spectrum modulated.
FIG. 2
shows how the RACH signal and the DCH signal are transmitted between the base station and the mobile station. First, the RACH signal is input to the base station from the mobile station to setup a c all. The RACH signal includes information such as the telephone number and a registration number of the user of the mobile station. Here, as an example, the RACH message of the RACH signal is 10 msec long. The RACH signal is transmitted by burst transmission where the communication is started and finished abruptly.
The ACH signal is then output from the base station to the mobile station. The ACH signal includes the information that the base station has acknowledged the mobile station. Then, the mobile station can start a call and sends the DCH signal to the base station. The DCH signal is a call signal set by the RACH signal. The DCH signal begins at an approximate predetermined time after the transmission of the ACH signal and finishes at a predetermined time after the commencement of the DCH signal transmission. Here, as an example, each DCH message of the DCH signal has a 10 msec time length.
The RACH signal and the DCH signal are complex signals having two-dimensions, namely an I-phase and a Q-phase. The receiving unit
12
converts the frequency of the RACH signal and DCH signal down to a baseband frequency from a carrier wave frequency band, and outputs to the RACH signal receiver
14
and the DCH signal receiver
16
, respectively. The RACH signal receiver
14
receives the RACH signal from the receiving unit
12
to despread the RACH signal.
The DCH signal receiver
16
receives the DCH signal from the receiving unit
12
to despread the DCH signal. The delay profile measuring unit
18
detects a peak of the RACH signal from the receiving unit
12
and detects the time of receiving the peak of the RACH signal. The delay profile measuring unit
18
then outputs the detected peak receiving time of the RACH signal to the demodulator
20
through the controller
26
. The demodulator
20
despreads the RACH signal received from the receiving unit
12
based on the peak receiving time of the RACH signal detected by the delay profile measuring unit
18
. The demodulator
20
then outputs the despread and demodulated RACH signal.
The delay profile measuring unit
22
receives the DCH signal from the receiving unit
12
and detects a peak of the DCH signal and detects the time of receiving the peak of the DCH signal. The delay profile measuring unit
22
then outputs the detected peak receiving time of the DCH signal to the demodulator
20
, through the controller
26
. The demodulator
24
despreads the DCH signal received from the receiving unit
12
based on the peak receiving time of the DCH signal detected by the delay profile measuring unit
22
. The demodulator
24
then outputs the despread and demodulated DCH signal.
The controller
26
sets a type of spreading code and timing of generation of the spreading code for despreading the RACH signal and the DCH signal for the delay profile measuring units
18
and
22
. The controller
26
also inputs the peak receiving time of the RACH signal from the delay profile measuring unit
18
and outputs this to the demodulator
20
. Furthermore, the controller
26
inputs the peak receiving time of the DCH signal and outputs this to the demodulator
24
.
The delay profile measuring units
18
and
22
measures a delay profile with a long delay time, so that the base station can receive various delay signals sent from various places inside the cell region of the base station. During the transmission of the signals, the signals transmit on a different path so that each of the delay profiles has a different delay time. At the same time as measuring the delay profile, the controller
26
notifies the demodulators
20
and
24
of the peak receiving time of the RACH and the DCH signal, so that the demodulators
20
and
24
can despread each RACH signal and DCH signal having various delay times.
FIG. 3
shows a detailed configuration of a delay profile measuring unit
18
. The delay profile measuring unit
18
can measure a delay profile having a long delay time. The delay profile measuring unit
18
has a RACH signal matched filter
28
and a RACH signal delay profile measuring unit
34
. The delay profile measuring unit
18
has a plurality of RACH signal matched filters
28
to despread the RACH signals sent from the plurality of users. Only one RACH signal matched filters
28
is shown in
FIG. 3
for simplicity. The RACH signal matched filter
28
has a spreading code generator
30
and a complex correlator
32
. The complex correlator
32
may include complex matched filter. The RACH signal delay profile measuring unit
34
has a power level calculator
36
, a delay time adjuster
38
, a delay profile averaging unit
40
, and a path detector
42
.
The RACH signal matched filter
28
inputs a RACH signal from the receiving unit
12
and despereads the input RACH signal. The RACH signal delay profile measuring unit
34
detects the peak receiving time of the RACH signal from the despread RACH signal, and outputs the peak receiving time of the RACH signal to the controller
26
.
The spreading code generator
30
generates a spreading code and outputs this to the complex correlator
32
. The complex correlator
32
despreads the RACH signal using spreading code generated by the spreading code generator
30
. Because the RACH signal is a complex signal having an I-phase and a Q-phase, the signal demodulated by the complex correlator
32
is also a complex signal having an I-phase and a Q-phase. The power level calculator
36
calculates the absolute value of a vector in the I-phase and the Q-phase of the demodulated RACH signal, to obtain a power level of the demodulated RACH signal. As a result of the power level calculation, the demodulated RACH signal having an I-phase and a Q-phase two-dimensional data changes to one-dimensional data.
The delay time adjuster
38
adjusts the delay times of a plurality of delay profiles having different delay times, to the same delay time. The delay profile averaging unit
40
has a memory to store the plurality of delay profiles, the delay times of which have been adjusted. The delay profile averaging unit
40
sums each of the peaks of the delay profiles as shown below in
FIG. 4
, so that the peak can be separated from the noise or interference components.
In this case, it is ass

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