Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-01-05
2002-07-02
Nguyen, Lee (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S422100, C455S436000, C455S440000, C455S450000, C370S331000, C370S335000, C370S342000
Reexamination Certificate
active
06415152
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a method for operating a base station in a code division multiple access (CDMA) mobile communication system, and more particularly to a method for operating abase station to solve a call discontinuity, or speech disable state, based on the inter-speech sphere movement of a mobile station in enlarging a speech radius limited in timing in a CDMA mobile communication system.
2. Description of the Prior Art
In a conventional CDMA mobile communication system, all mobile stations and base stations are timed with a reference time of the CDMA system. A mobile station obtains timing information from a message sent from a base station and sets a reference time on the basis of the obtained timing information for synchronization with the base station. At this time, the reference time set by the mobile station is a value delayed from a reference time of the base station due to a propagation delay from the base station to the mobile station and a signal process delay of the mobile station. Further, the mobile station sends a signal synchronously with the set self reference time, and such a reverse link signal is delayed for a propagation delay time and then received by the base station. As a result, the base station sends a forward link signal synchronously with a system reference clock, but receives a reverse link signal with a time delay (referred to hereinafter as “bidirectional propagation delay”) from the system reference clock.
In the CDMA system, the maximum allowable value of such a bidirectional propagation delay is limited in a hardware manner by a modem application specific integrated circuit (ASIC) of the base station. The maximum allowable value is about 416 &mgr;s, which is about 62 Km (416 &mgr;light velocity/2) when it is calculated in terms of cell speech radii in an open area. Consequently, the maximum allowable cell speech radius is limited in timing by the base station modem ASIC.
A method for enlarging the cell speech radius limited in timing by the hardware of the base station modem ASIC as mentioned above is shown in Korean Patent Application No. 98-36239, filed by this applicant.
FIG. 3
shows a service area for speech radius enlargement and call processing. As shown in this drawing, a speech radius, which is wider than that limited in timing by the hardware of the base station modem ASIC in the CDMA mobile communication system, is partitioned by a predetermined unit into first and second speech spheres
110
and
120
. The predetermined unit signifies a value below the maximum cell speech radius limited in timing by the hardware of the base station modem ASIC. In this regard, the above speech radius may be partitioned into a different number of speech spheres.
With reference to
FIG. 1
, there is shown in block form an example of a base station for speech radius enlargement in a CDMA mobile communication system. As shown in this drawing, the base station comprises a clock generator
200
, first and second signal processors
300
and
310
and radio frequency (RF) signal processing means
400
.
The clock generator
200
receives a 10 MHz signal, time of day (TOD) signal and 1 pulse per second (PPS) signal from a global positioning system (GPS) receiver
100
and generates a first EVEN SECOND clock synchronously with the 1 PPS signal and a second EVEN SECOND clock, which is delayed from the first EVEN SECOND clock by the maximum bidirectional propagation delay value of the first speech sphere
110
, as shown in FIG.
2
.
The first signal processor
300
assigns pilot, synchronization, paging and traffic channels covering both of the first and second speech spheres
110
and
120
synchronously with the first EVEN SECOND clock from the clock generator
200
and outputs the assigned channels to the RF signal processing means
400
. The first signal processor
300
further detects and demodulates only access and traffic channels, which are sent from mobile stations located in the first speech sphere
110
to the base station, synchronously with the first EVEN SECOND clock from the clock generator
200
.
The second signal processor
310
detects and demodulates only access and traffic channels, which are sent from mobile stations located in the second speech sphere
120
to the base station, synchronously with the second EVEN SECOND clock from the clock generator
200
.
Each of the first and second signal processors
300
and
310
includes at least one channel card
303
and an analog modulator/demodulator circuit
315
, as shown in FIG.
5
. The channel card
303
is composed of at least one channel element
305
containing a set of base station modem ASICs (commercially available from, for example, QUALCOMM company)
306
for modulating and demodulating digital signals, and a channel card processor
304
for controlling the channel element
305
. The analog modulator/demodulator circuit
315
includes a digital/analog (D/A) converter
307
for converting a digital signal from the channel card
303
into an analog signal, a quadrature phase shift keying (QPSK) modulator
309
for modulating the analog signal from the D/A converter
307
in a QPSK manner, a QPSK demodulator
313
for demodulating an RF signal in the QPSK manner, and an analog/digital (A/D) converter
308
for converting a QPSK-demodulated signal into a digital signal. The channel card
303
also receives the first or second EVEN SECOND clock from the clock generator
200
.
On the other hand, in each of the first and second signal processors
300
and
310
, each channel card is provided with a corresponding one of a channel element for the process of a forward channel and a channel element for the process of a reverse channel. Alternatively, each channel card may be provided with both of the channel elements.
The RF signal processing means
400
includes an RF transmitter
410
for receiving forward link channel signals from the first signal processor
300
, to be transmitted to mobile stations, modulating the received signals into RF signals and transmitting the modulated RF signals through a transmission antenna
500
, and an RF receiver
420
for receiving reverse link channel signals from the mobile stations through reception antennas
510
and
513
of the base station, RF-demodulating the received signals and transferring the resultant signals to the first and second signal processors
300
and
310
, respectively.
Now, a description will be given of the cell speech radius enlarging method of the 98-36239 patent application, which is performed by the base station with the above-mentioned construction.
First, the clock generator
200
receives the 10 MHz signal, TOD signal and 1 PPS signal from the GPS receiver
100
and generates the first EVEN SECOND clock synchronously with the 1 PPS signal. The clock generator
200
further generates the second EVEN SECOND clock delayed from the first EVEN SECOND clock for the maximum bidirectional propagation delay time of the first speech sphere
110
.
Then, the first and second signal processors
300
and
310
receive the first and second EVEN SECOND clocks from the clock generator
200
, respectively. The first signal processor
300
assigns pilot, synchronization and paging channels synchronously with the received first EVEN SECOND clock and transmits them to all speech spheres belonging to the base station through the RF signal processing means
400
and transmission antenna
500
.
At this time, if an access channel is sent from a specific mobile station located in the first speech sphere
110
, then it is received at the reception antenna
510
and transferred to the first signal processor
300
through the RF signal processing means
400
. As a result, the first signal processor
300
detects and demodulates the access channel, which is sent from the specific mobile station in the first speech sphere
110
to the base station, synchronously with the first EVEN SECOND clock.
Subsequently, the first signal processor
300
assigns a traffic channel synchronou
Hyundai Electronics Industries Co,. Ltd.
Merchant & Gould P,C,
Nguyen Lee
Yun Eugene
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