Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-12-09
2003-12-30
Vo, Nguyen T. (Department: 2681)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S562100, C455S101000, C455S277100, C370S334000
Reexamination Certificate
active
06671524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a base station apparatus that carries out a radio communication by switching between transmission and reception every predetermined unit time using a plurality of carriers and a transmission branch selection method.
2. Description of the Related Art
In a mobile communication system, it is proposed that a base station apparatus should select a transmission branch when sending a signal to a mobile station apparatus in order to alleviate the load of signal processing on the mobile station apparatus.
Suppose a group of signals transmitted or received for a unit time of switching between transmission and reception is called “burst” here. The base station apparatus alternately performs 1-burst (downlink) transmission and 1-burst (uplink) reception.
A conventional base station apparatus and transmission branch selection method are explained below using FIG.
1
and FIG.
2
.
FIG. 1
is a block diagram showing a configuration of a reception system in a conventional base station apparatus and
FIG. 2
is a block diagram showing a configuration of a transmission system in the conventional base station apparatus.
In FIG.
1
and
FIG. 2
, suppose the number of subcarriers is 4 and the number of branches is 2.
In
FIG. 1
, signals received from branch
1
and branch
2
(reception signals) are converted to digital signals by A/D converters
101
and
102
and FFT-processed by Fast Fourier Transform (hereinafter referred to as “FFT”) circuits
103
and
104
.
The reception levels of the FFT-processed reception signals are detected by level detectors
105
to
112
for their respective subcarriers. The detected reception levels are determined on a subcarrier basis by large/small comparison sections
113
to
116
as to which has a higher reception level, the signal received from branch
1
or the signal received from branch
2
.
The determination results are used as control signals
1
to
4
corresponding to their respective subcarriers for switching by switches
117
to
120
and for transmission branch selection in a transmission system which will be described later.
The FFT-processed reception signals are also input to switches
117
to
120
and the reception signal with a higher reception level between the reception signal from branch
1
and the reception signal from branch
2
is output for each subcarrier from switches
117
to
120
through switchover control by control signals
1
to
4
.
The output signals of switches
117
to
120
are subjected to delay detection processing by delay detectors
121
to
124
, determined by determination circuits
125
to
128
and output to parallel-serial (hereinafter referred to as “P/S” ) converter
129
. P/S converter
129
converts a plurality of parallel signals from determination circuits
125
to
128
to a serial signal and obtains a demodulated signal.
On the other hand, in
FIG. 2
, the modulated data are converted by serial-parallel (hereinafter referred to as “S/P” ) converter
201
from a serial signal to a plurality of parallel signals. The plurality of parallel signals from S/P converter
201
is each mapped by mapping circuits
202
to
205
.
For the signals mapped by mapping circuits
202
to
205
, either branch
1
or branch
2
is selected as their output destination by switches
206
to
209
using control signals
1
to
4
described with reference to FIG.
1
.
Inverse Fast Fourier Transform (hereinafter referred to as “IFFT” ) circuits
210
and
211
perform IFFT processing on signals to be transmitted from branch
1
and branch
2
, respectively. The IFFT-processed signals by IFFT circuits
210
and
211
are converted from digital to analog signals by D/A converters
212
and
213
.
As described above, the conventional base station apparatus detects reception levels of all subcarriers of reception signals at all branches, carries out reception diversity to determine which signal has the highest reception level received from different branches for each subcarrier and select a branch from which to receive signals based on this determination result, and transmission diversity to select a branch from which to transmit signals.
However, if there is a certain time interval after an uplink burst is received until a downlink burst is transmitted, that is, in the case of an intermittent communication condition, the radio propagation environment characteristic may change in the above interval in the conventional base station apparatus. Therefore, if a branch is selected based on the reception level of the immediately preceding uplink burst to transmit each subcarrier of the next downlink burst, accurate branch selection is not made.
Moreover, if a setting is made in such a way that branches can also be switched during 1-burst transmission, bursts become discontinuous on the mobile station apparatus side causing the error rate characteristic to deteriorate.
SUMMARY OF THE INVENTION
The present invention has been implemented taking account of the points described above and it is an objective of the present invention to provide a base station apparatus and transmission branch selection method carrying out accurate transmission branch selection even in an intermittent communication condition with a certain time interval after an uplink burst is received until a downlink burst is transmitted.
This objective is achieved by the base station apparatus estimating the reception levels of the next uplink bursts to be received from the reception levels of a plurality of uplink bursts and selecting a branch to transmit each subcarrier of the next downlink burst to be transmitted based on this estimated value.
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patent: 5648992 (1997-07-01), Wright et al.
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patent: 6480479 (2002-11-01), Miya et al.
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patent: 2-200020 (1990-08-01), None
patent: 5-29990 (1993-02-01), None
Matsumoto et al., entitledOFDM subchannel Space-Combining Transmission Diversity(SC-JD)for TDMA-TDD Broadband Wireless Accsess Systems, 1998 IEICE Conference, pp. 380.
English Language Abstract of JP 5-29990.
English Language Abstract of JP 2-200020.
Article by Takahashi et al., entitled “Antenna and Multi-Carrier Combined Diversity System”, IEICE Transactions on Communications, vol. E79B, No. 9, Sep. 1, 1996, pp. 1221-1226.
Article by Takahashi et al., entitled “Antenna and Multi-Carrier Combined Diversity System”, IEICE Transactions on Communications, vol. E79B, No 9, Sep. 1, 1996, pp. 1221-1226.
Article by Kondo et al., entitled“Linear Predictive Transmitter Diversity for Microcellular TDMA/TDD Mobile Radio System”, IEEE Vehicular Technology Conference, vol. 43, May 18, 1993, pp. 602-606.
Greenblum & Bernstein P.L.C.
Matsushita Electric - Industrial Co., Ltd.
Sharma Sujatha
Vo Nguyen T.
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