Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-03-16
2001-12-18
Trost, William (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S434000, C455S436000, C455S442000, C455S440000, C370S331000, C370S519000, C370S350000
Reexamination Certificate
active
06332079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a service area expansion method for a mobile communication system and a method of processing calls between service areas. More particularly, the present invention relates to a service area expansion method and a method of processing calls between service areas in a mobile communication system adopting a CDMA (code division multiple access) system like a DCS (digital cellular system) or a PCS (personal communication system), in which a reference clock is delayed and an application specific integrated circuit (ASIC) of a plurality of CSMs (cell site modem) in a base station is controlled using such a delayed reference clock so as to expand service area by each CSM ASIC unit, and a handoff area is positioned between expanded service areas so as to perform a normal call processing.
2. Description of the Related Art
In general, as shown in
FIG. 1
, mobile communication system like DCS or PCS includes a mobile station
1
, a base station
2
for transmitting/receiving data to/from the mobile station, a control station
3
for transmitting/receiving data to/from the base station, and an exchange station
4
.
A mobile communication system having such a configuration synchronizes timing using a GPS (global position system), and terminals of mobile communications generate signals in accordance with the reference clock.
Thus-generated signals generate a phase delay by a delay in movement distance, and a correct phase tracking is required in demodulating a signal at a receiving terminal.
However, a CSM ASIC which is mounted in a channel card of the base station
2
so as to be used as a channel element has a phase tracking scope of 512PN chip (1PN chip=813 nsec) which can be converted into 125 km, i.e., distance of radio wave movement.
The above-mentioned distance is a round trip distance between the base station
2
and the mobile station
1
, and a service area is a radius of 62.5 km from the base station
2
if any hardware or software-related delay does not exist.
The service area in the above-described mobile communication system is restricted within the radius of 60 km due to the limitation of CSM ASIC.
In a conventional art, a pair of CSM ASICs are employed to expand the service area without re-design of CSM ASIC.
That is, the CSM ASIC occupying a normal region within 60 km is capable of performing a phase tracking having a scope of 0 to 512PN chip, and the CSM ASIC occupying an extended region of 60 km to 120 km is provided with a reference clock delayed by 512PN chip and capable of performing a phase tracking having a scope of 512PN to 1,024 PN chip, thus expanding the service area.
As described above, a conventional art expands an overall service area by means of dividing the service area into a normal area and an extended area. However, a method of normally processing calls between service areas is required for cases where a mobile terminal moves from the normal area to the extended area, or from the extended area to the normal area.
SUMMARY OF THE INVENTION
Therefore, it is a first object of the present invention to provide a service area expansion method for a mobile communication system in which a reference clock is delayed in a base station, the reference clock and the delayed reference clock are respectively provided to corresponding CSM ASICS, and the CSM ASICs are enabled respectively so as to thereby expand the service area.
It is a second object of the present invention to provide a method of processing calls between service areas for a mobile communication system in which a handoff area is positioned between a normal area and an extended area so as to allow both two CSM ASICs to perform a phase tracking, and a call processing between service area is normally performed by using such functions as adding, dropping, swap pointing and radio wave RTD (round trip delay).
To accomplish the first object of the present invention, there is provided a service area expansion method for a mobile communication system including a TFC (time & frequency controller), a first delay for counting a system clock output from the TFC and outputting an even second clock delayed by a predetermined time in accordance with the counted value, a second delay for delaying the even second clock and the delayed even second clock output from the first delay, respectively, and generating a first and a second interrupt signals of 80 msecond ticks, a CPU for generating an interrupt using the first and second interrupt signals generated from the second delay and generating a first and a second enable signals, a normal area CSM ASIC which is enabled by the first enable signal output from the CPU, operates in accordance with the even second clock output from the TFC, and processes a call of a mobile terminal in the normal area, and an extended area CSM ASIC which is enabled by the second enable signal output from the CPU, operates in accordance with the delayed even second clock output from the first delay, and processes a call of a mobile terminal in the extended area, the method including: a first step of initializing the normal area CSM ASIC using the even second clock output from the TFC, the extended area CSM ASIC using the delayed even second clock output from the first delay in accordance with a re-synchronization command for the normal area CSM ASIC and the extended area CSM ASIC and which is output from the CPU, receiving from a control station a configuration for channel allocation for each CSM ASIC, and determining whether a channel to be allocated is a traffic channel or an access channel; a second step of setting up a pair of the two CSM ASICs to a traffic channel or an access channel if the channel to be allocated is determined as a traffic channel or an access channel in the first step, and advancing a forward timing by a delayed reference clock; and a third step of setting up only the normal area CSM ASIC to a corresponding channel if the channel to be allocated is not determined as a traffic channel or an access channel in the first step.
To accomplish the second object of the present invention, there is provided a method of processing calls between service areas for a mobile communication system in which a handoff area for a phase tracking of both normal area CSM (cell site modem) and extended area CSM is arranged between the normal area and extended area, the method including: a first step of detecting an RTD (round trip delay) value at a state where a call is normally maintained in the normal area if a mobile terminal moves from the normal area to the extended area; a second step of setting up a call to the extended area CSM ASIC and disabling an uppermost terminal for transmission/reception if the RTD value detected in the first step is Extend-Call-Add Point; a third step of enabling transmission/reception of the extended area CSM ASIC and disabling transmission/reception of the normal area CSM ASIC if the RTD value detected in the first step is Normal-Call To Extend-Call-Swap Point; and a fourth step of releasing the call by the normal area CSM ASIC and normally maintaining at the extended area the call of the mobile terminal if the RTD value detected in the first step is Normal-Call-Drop Point.
To accomplish the second object of the present invention, there is provided a method of processing calls between service areas for a mobile communication system in which a handoff area for a phase tracking of both normal area CSM (cell site modem) and extended area CSM is arranged between the normal area and extended area, the method including: a first step of detecting an RTD (round trip delay) value at a state where a call is normally maintained in the extended area if a mobile terminal moves from the extended area to the normal area; a second step of setting up a call to the normal area CSM ASIC and disabling an uppermost terminal for transmission/reception if the RTD value detected in the first step is Normal-Call-Add Point, a third step of enabling transmission/reception of the normal area CSM AS
Kim Jae-hoon
Kim Tae-Hoon
Uhr Joon-Sun
Coleman Henry D.
Hyundai Electronics Industries Co,. Ltd.
Milord Marceau
Sapone William J.
Sudol R. Neil
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