Apparatus and method for expanding service area of CDMA mobile communication system

• US 6,421,330 B1
• Filed: 04/28/1999
• Issued: 07/16/2002
• Est. Priority Date: 09/03/1998
• Status: Expired due to Term

• Current Assignee: Hyundai Syscomm, Inc. (Hyundai Motor Group)
• Original Assignee: Hyundai Electronics Industries Co. Ltd. (SK Hynix Inc.)
• Inventors: Shin, Yang Soo, Chung, Chae Hun
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): LE, LANA N
• Application Number:
  US09/301,474
• Time in Patent Office: 1,175 Days
• Field of Search: 370/335, 370/350, 370/517, 370/519, 370/320, 370/342, 455/502, 455/503, 455/427, 455/561
• US Class Current: 370/335
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713

Abstract

An apparatus and method for expanding a service area of a code division multiple access (CDMA) system restricted in terms of timing. The service area of a CDMA mobile communication system, which is defined by a radius longer than a radius of a communication supported area, namely, a cell, restricted in terms of timing due to the hardware of a base station modem ASIC equipped in the system, is radially divided into a plurality of radial zones by a constant distance not longer than a maximum possible cell radius allowed by the base station modem ASIC. In accordance with the present invention, signal processing units are used which are configured in such a fashion that one of them covers the entire zone of the service area in regard to forward links from an associated base station to mobile stations in different zones of the service area while covering only the zone nearest to the base station in regard to reverse links from the mobile stations to the base station. The remaining signal processing units cover reverse links associated with the remaining zones of the service area, respectively. By such a configuration, it is possible to extend the radius of the cell limited in terms of timing.

Claims

1. An apparatus for expanding a service area of a CDMA mobile communication system from a first zone resulting from a restriction of the service area occurring in terms of timing to second, third and fourth zones gradually expanding wider than the first zone by a distance not longer than a cell radius allowed by a base station modem application-specific integrated circuit (ASIC) equipped in the system, comprising:

a clock generating unit for receiving 10 MHZ, time of day (TOD), and 1-pulse per second (PPS) signals from a global positioning system (GPS) receiver and generating a first even-second clock synchronized to the 1-PPS signal, the clock generating unit also generating second, third, and fourth even-second clocks delayed by respective maximum bidirectional propagation delay values associated with the second, third and fourth zones;

a first signal processing unit for receiving the first even-second clock from the clock generating unit, the first signal processing unit serving to, in regard to forward links from an associated base station to mobile stations in the service area, modulate and transmit forward link channels covering all the first, second, third and fourth zones in sync with the first even-second clock while, in regard to reverse links from the mobile stations to the base station, detecting and demodulating only reverse link channels transmitted from mobile stations located in the first zone in sync with the first even-second clock;

a second signal processing unit for receiving the second even-second clock from the clock generating unit, the second signal processing unit serving to detect and demodulate only reverse link channels transmitted to the base station from mobile stations located in the second zone in sync with the second even-second clock;

a third signal processing unit for receiving the third even-second clock from the clock generating unit, the third signal processing unit serving to detect and demodulate only reverse link channels transmitted to the base station from mobile stations located in the third zone in sync with the third even-second clock; and

a fourth signal processing unit for receiving the fourth even-second clock from the clock generating unit, the fourth signal processing unit serving to detect and demodulate only reverse link channels transmitted to the base station from mobile stations located in the fourth zone in sync with the fourth even-second clock.

2. The apparatus in accordance with claim 1, wherein each of the first, second, third and fourth signal processing units comprises:

at least one channel card including at least one channel element provided with a set of base station modem ASICs and adapted to modulate/demodulate digital signals, and a channel card processor adapted to control the channel element; and

an analog modulator/demodulator unit including a D/A converter for receiving a digital signal from an associated one of the at least channel card and converting the received digital signal into an analog signal, a QPSK modulator for receiving the analog signal from the D/A converter and QPSK modulating the received analog signal, a QPSK demodulator for receiving an input radio frequency (RF) signal and QPSK demodulating the input RF signal, and an A/D converter for receiving the QPSK demodulated signal from the QPSK demodulator and converting the received signal into a digital signal.

3. The apparatus in accordance with claim 1, further comprising RF signal processing means comprising:

an RF transmitter unit coupled between the first, second, third and fourth signal processing unit and the transmitting and receiving antennas equipped in the base station, the RF transmitter unit receiving forward link channels from the first signal processing unit and RF modulating the received forward link channels in the form of a signal capable of being transmitted over the transmitting antenna; and

an RF receiver unit for receiving a reverse link channel signal from a mobile station over the receiving antenna and RF modulating the received reverse link channel signal in the form of a signal capable of being processed in the first, second, third, and fourth signal processing units.

4. An apparatus for expanding a service area of a CDMA mobile communication system from a first zone resulting from a restriction of the service area occurring in terms of timing to second, third and fourth zones gradually expanding wider than the first zone by a distance not longer than a cell radius allowed by a base station modem application-specific integrated circuit (ASIC) equipped in the system, comprising:

a clock generating unit for receiving 10 MHZ, time of day (TOD), and 1-pulse per second (PPS) signals from a global positioning system (GPS) receiver and generating a first even-second clock synchronized to the 1-PPS signal, the clock generating unit also generating second, third, and fourth even-second clocks delayed by respective maximum bidirectional propagation delay values associated with the second, third and fourth zones;

a first signal processing unit for receiving the first even-second clock from the clock generating unit, the first signal processing unit serving to, in regard to forward links from an associated base station to mobile stations in the service area, modulate and transmit pilot, synchronization and paging channels covering all the first, second, third and fourth zones and a traffic channel covering the first zone in sync with the first even-second clock while, in regard to reverse links from the mobile stations to the base station, detecting and demodulating only reverse access and traffic channels transmitted from mobile stations located in the first zone in sync with the first even-second clock so as to cover only the first zone;

a second signal processing unit for receiving the second even-second clock from the clock generating unit, the second signal processing unit serving to, in regard to forward links from the base station to the mobile stations in the second zone, modulate and transmit the forward traffic channel in a state advanced by a desired delay time corresponding to a delay time for which the second even-second clock is delayed from the first even-second clock while, in regard to reverse links from the mobile stations to the base station, detecting and demodulating only reverse access and traffic channels transmitted from the mobile stations in the second zone in sync with the second even-second clock so as to cover only the second zone;

a third signal processing unit for receiving the third even-second clock from the clock generating unit, the third signal processing unit serving to, in regard to forward links from the base station to the mobile stations in the third zone, modulate and transmit the forward traffic channel in a state advanced by a desired delay time corresponding to a delay time for which the third even-second clock is delayed from the first even-second clock while, in regard to reverse links from the mobile stations to the base station, detecting and demodulating only reverse access and traffic channels transmitted from the mobile stations in the third zone in sync with the third even-second clock so as to cover only the third zone; and

a fourth signal processing unit for receiving the fourth even-second clock from the clock generating unit, the fourth signal processing unit serving to, in regard to forward links from the base station to the mobile stations in the fourth zone, modulate and transmit the forward traffic channel in a state advanced by a desired delay time corresponding to a delay time for which the fourth even-second clock is delayed from the first even-second clock while, in regard to reverse links from the mobile stations to the base station, detecting and demodulating only reverse access and traffic channels transmitted from the mobile stations in the fourth zone in sync with the fourth even-second clock so as to cover only the fourth zone.

5. The apparatus in accordance with claim 4, further comprising RF signal processing means comprising:

an RF transmitter unit coupled between the first, second, third and fourth signal processing unit and the transmitting and receiving antennas equipped in the base station, the RF transmitter unit receiving forward link channels from the first signal processing unit and RF modulating the received forward link channels in the form of a signal capable of being transmitted over the transmitting antenna; and

an RF receiver unit for receiving a reverse link channel signal from a mobile station over the receiving antenna and RF modulating the received reverse link channel signal in the form of a signal capable of being processed in the first, second, third, and fourth signal processing units.

6. The apparatus in accordance with claim 4, wherein:

each of the first, second, third and fourth signal processing units comprises

at least one channel card including at least one channel element provided with a set of base station modem ASICs and adapted to modulate/demodulate digital signals, and a channel card processor adapted to control the channel element, and

an analog modulator/demodulator unit including a D/A converter for receiving a digital signal from an associated one of the at least channel card and converting the received digital signal into an analog signal, a QPSK modulator for receiving the analog signal from the D/A converter and QPSK modulating the received analog signal, a QPSK demodulator for receiving an input radio frequency (RF) signal and QPSK demodulating the input RF signal, and an A/D converter for receiving the QPSK demodulated signal from the QPSK demodulator and converting the received signal into a digital signal; and

the second, third and fourth signal processing units are provided at their base station modem ASICs with timing compensation registers respectively transmitting the forward traffic channel to mobile stations in a state advanced by desired delay times corresponding to respective times for which the second, third and fourth even-second clocks are delayed from the first even-second clock.

7. A method for expanding a service area of a CDMA mobile communication system from a first zone resulting from a restriction of the service area occurring in terms of timing to second, third and fourth zones gradually expanding wider than the first zone by a distance not longer than a cell radius allowed by a base station modem application-specific integrated circuit (ASIC) equipped in the system, comprising the steps of:

receiving, at a clock generating unit, 10 MHZ, TOD, and 1-PPS signals from the GPS receiver and generating, from the clock generating unit, a first even-second clock synchronized to the 1-PPS signal and second, third, and fourth even-second clocks delayed by respective maximum bidirectional propagation delay values associated with the second, third and fourth zones with respect to the first even-second clock;

receiving, at first, second, third, and fourth signal processing units, the first, second, third, and fourth even-second clocks while modulating and transmitting pilot, synchronization, paging, and traffic channels covering all the first, second, third and fourth zones in sync with the first even-second clock by the first signal processing unit;

detecting and demodulating an access channel transmitted from a mobile station located in the service area by one of the first, second, third, and fourth signal processing units associated with the zone where the mobile station is located, in sync with an associated one of the first, second, third, and fourth even-second clocks;

modulating and transmitting a forward traffic channel associated with the zone of the mobile station in sync with the first even-second clock by the first signal processing unit; and

detecting and demodulating a reverse traffic channel transmitted from the mobile station in sync with the associated even-second clock by the associated signal processing unit.

8. A method for expanding a service area of a CDMA mobile communication system from a first zone resulting from a restriction of the service area occurring in terms of timing to second, third and fourth zones gradually expanding wider than the first zone by a distance not longer than a cell radius allowed by a base station modem application-specific integrated circuit (ASIC) equipped in the system, comprising the steps of:

receiving, at a clock generating unit, 10 MHZ, TOD, and 1-PPS signals from the GPS receiver and generating, from the clock generating unit, a first even-second clock synchronized to the 1-PPS signal and second, third, and fourth even-second clocks delayed by respective maximum bidirectional propagation delay values associated with the second, third and fourth zones with respect to the first even-second clock;

receiving, at first, second, third, and fourth signal processing units, the first, second, third, and fourth even-second clocks while modulating and transmitting pilot, synchronization, paging, and traffic channels covering all the first, second, third and fourth zones in sync with the first even-second clock by the first signal processing unit;

detecting and demodulating an access channel transmitted from a mobile station located in the service area by one of the first, second, third, and fourth signal processing units associated with the zone where the mobile station is located, in sync with an associated one of the first, second, third, and fourth even-second clocks;

modulating and transmitting a forward traffic channel in sync with the first even-second clock by the first signal processing unit when the zone of the mobile station corresponds to the first zone while modulating and transmitting, by the associated signal processing unit, the forward traffic channel in a state advanced by a desired delay time corresponding to a delay time for which the associated even-second clock is delayed from the first even-second clock when the zone of the mobile station corresponds to one of the second, third, and fourth zones; and

detecting and demodulating a reverse traffic channel transmitted from the mobile station in sync with the associated even-second clock by the associated signal processing unit.