Handoff test method between mobile communication switching stations

An improved handoff test method for mobile communication stations which is capable of more easily testing a handoff function between switching stations by providing a handoff generation and control apparatus and processing a forward hard handoff and a backward hard handoff using a handoff signal and a control signal outputted from the handoff generation and control apparatus. The method comprises the steps of a first step for judging whether a test hard handoff signal from a handoff generation and control apparatus of the exchange station is a forward hard handoff signal or a backward hard handoff signal, a second step for determining whether a forward hard handoff test is performed in the serving exchange station or a forward hard handoff test in the target exchange station when the test hard handoff signal is not a forward hard handoff signal in the first step, a third step for determining whether a backward hard handoff test is performed in the serving exchange station or a backward hard handoff test is performed in the target exchange station when a test hard handoff signal is a backward hard handoff signal in the first step, and a fourth step for performing a forward hard handoff in the serving exchange station when the forward hard handoff test is performed in the exchange station in the second step.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a handoff test method between mobile 
communication switching stations using a Code Division Multiple Access 
(CDMA) method, and in particular, to an improved handoff test method 
between mobile communication switching stations which is capable of more 
easily testing a handoff function between switching stations by providing 
a handoff generation and control apparatus and processing a forward hard 
handoff and a backward hard handoff using a handoff signal and a control 
signal outputted from the handoff generation and control apparatus. 
2. Description of the Conventional Art 
Generally, the conventional CDMA mobile communication system is a 
communication system implemented between mobile communication users or a 
mobile communication unit and a fixed communication unit by which it is 
possible to communicate between remote users by using radio signals. The 
conventional CDMA mobile communication system includes a mobile station 
which is movable in a predetermined area, a base station for 
transmitting/receiving a message to/from the mobile station and managing a 
wireless resource, a control station for controlling the base station and 
transmitting/receiving a message, and an exchange station for performing a 
switching operation between the control station and another remote 
station, and a predetermined network. 
In the above-described mobile communication system, it is very important to 
secure a desired mobility of a subscriber terminal of the mobile station. 
In order to obtain such desired mobility of the subscriber, a position 
registration and a handoff technique are needed. 
The position registration is a process for reporting various features such 
as an operational state of a mobile network or itself network to the base 
station, and the handoff technique is a process for switching a 
communication path between the mobile station and the base station so that 
the mobile station is deviated from the service region of the base station 
or the sector. 
As the above-described handoff methods, there are known a soft handoff 
method which is a handoff method between neighboring stations using the 
identical frequency and a hard handoff method which is a handoff method 
between the base station and the exchange station using the different 
frequencies. In conventional art, the handoff function is tested in order 
to obtain a more efficiency processing method rather than the 
above-described handoff. 
In particular, in the operation of testing the hard handoff function 
between the exchange stations, since the mobile network is remotely 
positioned from the exchange station, when a user moves from the 
controlled area of one exchange station to another area of the exchange 
station by using a vehicle, thus generating a hard handoff, the handoff 
function is tested by performing the handoff operation between the 
exchange stations by using the thusly generated hard handoff signal and a 
control signal outputted from the mobile station. 
However, in the conventional hard handoff test method, since a user must 
generate a hard handoff signal between exchange stations which is needed 
for testing the hard handoff function by moving his position from a 
control area of one exchange station to another area of the exchange 
station using a vehicle. The user have to directly move to the area for 
the handoff function test. In addition, many instruments and high cost are 
required for generating a desired hard handoff signal, and the test for 
the handoff function is inefficiently performed. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a handoff 
test method for mobile communication switching stations which overcomes 
the aforementioned problems encountered in the conventional art. 
It is another object of the present invention to provide an improved 
handoff test method for mobile communication stations which is capable 
more effectively performing a handoff test by installing a handoff 
generation and control apparatus in an exchange station without using a 
handoff signal and a control signal from a mobile station based on a 
user's direct movement at the time of generating a forward hard handoff or 
a backward hard handoff between exchange stations and processing a handoff 
operation and processing a forward hard handoff or a backward hard handoff 
by using a handoff signal and a control signal from the handoff generation 
and control apparatus, whereby it is possible to significantly reduce the 
number of necessary staff, time and cost. 
It is another object of the present invention to provide an improved 
handoff test method for mobile communication stations which is capable of 
more easily testing a handoff function between switching stations by 
providing a handoff generation and control apparatus and processing a 
forward hard handoff and a backward hard handoff using a handoff signal 
and a control signal outputted from the handoff generation and control 
apparatus. 
To achieve the above objects, there is provided a handoff test method for 
mobile communication switching stations, wherein the mobile communication 
system includes a mobile station, a base station, a control station, a 
control station matching unit, a mobile call control unit, and a handoff 
controller, comprises the steps of a first step for judging whether a test 
hard handoff signal from a handoff generation and control apparatus of the 
exchange station is a forward hard handoff signal or a backward hard 
handoff signal, a second step for determining whether a forward hard 
handoff test is performed in the serving exchange station or a forward 
hard handoff test in the target exchange station when the test hard 
handoff signal is not a forward hard handoff signal in the first step, a 
third step for determining whether a backward hard handoff test is 
performed in the serving exchange station or a backward hard handoff test 
is performed in the target exchange station when a test hard handoff 
signal is a backward hard handoff signal in the first step, a fourth step 
for performing a forward hard handoff in the serving exchange station when 
the forward hard handoff test is performed in the exchange station in the 
second step, a fifth step for performing a forward hard handoff in the 
target exchange station when the forward hard handoff test is performed in 
the target exchange station in the second step, a sixth step for 
performing a backward hard handoff in the serving exchange station when 
the backward hard handoff test is performed in the serving exchange 
station in the third step, and a seventh step for performing a backward 
hard handoff in the target exchange station when the backward hard handoff 
test is performed in the target exchange station in the third step. 
Additional advantages, objects and other features of the invention will be 
set forth in part in the description which follows and in part will become 
apparent to those having ordinary skill in the art upon examination of the 
following or may be learned from practice of the invention. The objects 
and advantages of the invention may be realized and attained as 
particularly pointed out in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION 
The hard handoff test method between mobile communication exchange stations 
according to the present invention will now be explained with reference to 
the accompanying drawings. 
FIG. 1 illustrates the construction of a mobile communication system 
provided with a handoff generation and control apparatus for a handoff 
test according to the present invention, wherein a mobile communication 
system includes a base station 10, a control station 20 having a call 
processing unit 21, and an exchange station 30. The system includes a 
handoff generation and control apparatus 32 for generating a hard handoff 
signal between exchange stations for performing a handoff function test in 
the mobile call processing unit 31 of the exchange station 30 and 
controlling the same. 
The handoff generation and control apparatus 32 generates a forward hard 
handoff signal for a serving exchange station based on the movement of a 
mobile station and transmits the forward hard handoff generation signal to 
the serving exchange station on behalf of the base station and control 
station, so that the serving exchange station processes a forward hard 
handoff. 
In addition, a forward hard handoff request signal is generated by the 
serving exchange station which is generated by the movement of the mobile 
station and then is transmitted to a target exchange station, so that the 
target exchange station processes a forward hard handoff operation. A 
backward hard handoff request signal is generated by the target exchange 
station by the movement of the mobile station and then is transmitted to 
the serving exchange station, so that the serving exchange station 
processes a backward hard handoff operation. 
A backward hard handoff signal is generated by the target exchange station 
by the movement of the mobile station, and the backward hard handoff 
generation signal is transmitted to the target exchange station on behalf 
of the base station and the control station, so that the target exchange 
station processes a backward hard handoff operation. 
FIG. 2 illustrates the construction of a mobile communication system 
exchange station 30 provided with a handoff generation and control 
apparatus 32 for a handoff test operation, which includes a handoff 
generation and control apparatus 32 for generating a forward hard handoff 
signal, a forward hard handoff request signal, a backward hard handoff 
request signal and a backward hard handoff signal, performing a handoff 
processing function in accordance with the thusly generated hard handoff 
signals and hard handoff request signals, and controlling a call, a 
control station matching unit 33 performing a call setting and maintaining 
function and performing a processing function which is needed for a 
handoff operation, a mobile controller 34 connected with the control 
station matching unit 33 for performing an actual call setting and 
maintaining function, and a handof f controller 35 connected with the 
control station matching unit 33 for performing an operation needed for 
the handoff operation and an interacting function with another exchange 
station. 
The handoff generation and control apparatus 32 is loaded to the mobile 
call controller 34 and is operated as the control station 20, and performs 
a message transmission and receiving operation together with the control 
station matching unit 33. 
The forward hard handoff and backward hard handoff processing processes 
performed by the serving exchange station or target exchange station by 
using a test hard handoff signal and hard handoff request signal outputted 
from the handoff generation and control apparatus 32 of the mobile 
communication system exchange station will now be explained with reference 
to FIGS. 3 through 7. 
In the present invention, when a handoff is generated in a state that a 
mobile station is in use, the exchange station set a first call is called 
a serving exchange station, and a newly entered exchange station is called 
a target exchange station. 
In addition, the handoff generation and control apparatus 32 generates a 
forward hard handoff signal, a forward hard handoff request signal, a 
backward hard handoff request signal, and a backward hard handoff signal. 
Here, the forward hard handoff signal denotes a hard handoff signal which 
is generated as a mobile station is first moved from one exchange station 
service area to another exchange station service area during when a system 
is in use, and the backward hard handoff signal denotes a hard handoff 
signal which the mobile station is moved to a previously defined exchange 
station service area after a forward hard handoff is generated at the time 
when the mobile station is first moved to another exchange station service 
area when the system is in use. 
FIG. 3 illustrates a flow chart of a hard handoff test method between 
exchange stations based on the handoff generation and control apparatus 
32, in which a handoff function is tested in accordance with the kind of a 
test handoff signal and a handoff processing step, which signal is 
outputted from the handoff generation and control apparatus 32 provided in 
the exchange station 30. 
When a test handoff signal is outputted from the handoff generation and 
control apparatus 32 in Step S10, it is judged whether a test hard handoff 
signal is a forward hard handoff signal or a backward hard handoff signal 
in Step S20. 
If the test hard handoff signal from the handoff generation and control 
apparatus 32 in Step S20 is a forward hard handoff signal, it is judged 
whether a forward hard handoff test is performed by the serving exchange 
station, or the forward hard handoff test is performed by the target 
exchange station in Step S30. 
In addition, in the case that the test hard handoff signal outputted from 
the handoff generation and control apparatus 32 in Step S20 is a backward 
hard handoff signal, it is judged whether the backward hard handoff test 
is performed by the serving station, or the backward hard handoff test is 
performed by the target exchange station in Step S40. 
In the case that the forward hard handoff test is performed by the serving 
exchange station in Step S30, the forward hard handoff is performed by the 
serving exchange station, and in the case that the forward hard handoff 
test is performed by the target exchange station, the forward hard handoff 
is performed by the target exchange station in Step S60. 
In addition, in the case that the backward hard handoff test is performed 
by the serving exchange station in Step S40, the backward hard handoff is 
processed by the serving exchange station in Step S70, and in the case 
that the backward hard off test is performed by the target exchange 
station, the backward hard handoff is processed by the target exchange 
station in Step S80. 
Next, the hard handoff processing steps of Steps S50 through S80 will now 
be explained with reference to FIGS. 4 through 7. 
FIG. 4 illustrates a forward hard handoff processing flow by the serving 
exchange station based on the handoff generation and control apparatus 32 
when a handoff is generated. The handoff generation and control apparatus 
32 of the serving exchange station transmits a transmission subscriber 
information to the mobile call controller 34 through the control station 
matching unit 33 and requests an outgoing signal setting operation of a 
particular subscriber. 
The mobile call controller 34 sets an outgoing signal by using the 
transmission subscriber information transmitted thereto by the handoff 
generation and control apparatus 32 and reports a state that the outgoing 
signal setting is completed to the control station matching unit 33, and 
reports to the handoff generation and control apparatus 32 through the 
control station matching unit 33 that the outgoing signal is normally set 
in Step S51. 
After the outgoing signal is set, the mobile call controller 34 normally 
sets an incoming signal by using the receiving subscriber information 
transmitted thereto from the handoff generation and control apparatus 32 
and transmits a response message from the incoming subscriber to the 
handoff generation and control apparatus 32 through the control station 
matching unit 33 in Step S52. 
Thereafter, the handoff generation and control apparatus 32 receives a 
response message of the incoming subscriber, recognizes an in-use state of 
the system based on the thusly received response message, and generates a 
forward hard handoff generation message which informs that the handoff is 
generated from a transmission subscriber after about 10 seconds, so that 
the control station matching unit 33 receives a forward hard handoff 
generation message in Step S53. 
At this time, the handoff generation and control apparatus transmits the 
information data of the current serving exchange station and the 
information data of the target exchange area in which the mobile station 
performs a handoff and is newly positioned to the control station matching 
unit 33. 
When the forward hard handoff message is generated from the handoff 
generation and control apparatus 32, the control station matching unit 33 
informs that then handoff is first generated to the handoff controller 35, 
and then the handoff controller 35 analyzes the information of the target 
exchange station of the area in which the mobile station of the handoff 
generation and control apparatus 32 is newly positioned and prepares a 
message to be transmitted. After the preparation, the forward hard handoff 
request message is transmitted to the target exchange station in Step S54. 
Meanwhile, the target exchange station which receives the forward hard 
handoff request message, transmits an information that the mobile station 
is positioned in the base station area of the current target exchange 
station to the control station matching unit, and the control station 
matching unit requests the handoff generation and control apparatus of the 
target exchange station which operates on behalf of the control station to 
allocate a new channel based on the information from the mobile station. 
The handoff generation and control apparatus which receives a channel 
allocation request signal processes a handoff operation in which the 
channel is allocated and transmits a response message with respect to the 
forward handoff request message to the serving exchange station through 
the control station matching unit and the handoff controller. 
Therefore, the handoff controller 35 of the serving exchange station judges 
whether a response message corresponding to the forward hard handoff 
request message is received from the target exchange station which 
receives the forward hard handoff request message in Step S55. 
When the handoff controller 35 receives a response message with respect to 
the forward hard handoff request message from the target exchange station, 
the handoff controller 35 transmits a message to release the channel 
allocation information of the control station matching unit 33, and 
requests the handoff generation and control apparatus 32 to release the 
wireless resource information through the control station matching unit 
33, so that the handoff generation and control apparatus 32 releases the 
wireless resource information in Step S56. 
Thereafter, when the handoff generation and control apparatus of the target 
exchange station is connected with a wireless access which is allocated by 
the same, and then the mobile station reports a state that the forward 
hard handoff is completed in the current target exchange station to the 
serving exchange station through the control station matching unit and the 
handoff controller, the handoff controller 35 of the serving exchange 
station judges whether the forward handoff completion message of the 
target exchange station is received in Step S57. 
When the handoff controller 35 receives a forward hard handoff completion 
message in Step S57, the handoff controller 35 requests the control 
station matching unit 33 to release the handoff, and the control station 
matching unit 33 requests the handoff generation and control apparatus 32 
to release the call control processing step in Step S58. 
Meanwhile, in Step S55, when the handoff controller 35 does not receive the 
response message with respect to the forward hard handoff request message 
from the target exchange station, or in Step S57, the handoff controller 
35 does not receive the forward hard handoff completion message from the 
target exchange station, the in-use state is maintained in Step S59. 
As the handoff generation and control apparatus 32 releases the call 
control processes, thus completing the forward hard handoff of the 
outgoing signal, and then the forward hard handoff of the serving exchange 
station is performed, so that the forward hard handoff function between 
the serving exchange station and the target exchange station is performed. 
FIG. 5 illustrates a forward hard handoff process by the target exchange 
station based on the handoff generation and control apparatus 32 when the 
handoff occurs. When a forward hard handoff request message outputted from 
the serving exchange station, namely, the opposite exchange station, 
through the handoff generation and control apparatus 32 of the target 
exchange station is generated like the mobile station is moved from the 
current serving exchange station to the target exchange station, the 
handoff controller 35 of the target exchange station receives a forward 
hard handoff request message in Step S61. 
The handoff controller 35 which receives a forward hard handoff request 
message transmits the hard handoff request message to the control station 
matching unit 33, and the control station matching unit 33 requests the 
handoff generation and control apparatus 32, which acts as the control 
station, to allocates a new wireless resource using the information of the 
mobile station. 
Thereafter, the handoff generation and control apparatus 32 performs some 
steps which are needed for a handoff such as a wireless resource 
allocation in accordance with an allocation request of a wireless resource 
in Step S62, and then transmits a forward hard handoff preparation 
completion message to the serving exchange station in Step S63. 
Namely, the handoff generation and control apparatus 32 transmits the 
forward hard handoff preparation completion message to the control station 
matching unit 33, and the control station matching unit 33 reports a state 
that a preparation is completed for the forward handoff control to the 
handoff controller 35. Thereafter, the handoff controller 35 transmits the 
forward hard handoff preparation completion message to the serving 
exchange station which transmits the forward hard handoff request signal. 
In addition, in a case that the handoff generation and control apparatus 32 
does not perform some steps for a handoff process, for example, the 
wireless resource is not allocated, in accordance with the allocation 
request of the wireless resource in Step S62, the forward hard handoff 
preparation non-completion message is transmitted to the serving exchange 
station in Step S64. 
As in Step S63, a response massage with respect to the forward hard handoff 
request which is a forward hard handoff preparation completion message, is 
transmitted to the serving exchange station which requests the forward 
hard handoff through the handoff controller 35, and then the handoff 
generation and control apparatus 32 transmits the forward hard handoff 
completion message outputted from the target exchange station to the 
serving exchange station through the control station matching unit 33 and 
the handoff controller 35 like the forward hard handoff is completed by 
the target exchange station as the mobile station is moved from a 
particular base station to the service area of the target exchange station 
in Step S65. 
After the forward hard handoff of the target exchange station is generated, 
the forward hard handoff function is tested between the serving exchange 
station and the target exchange station. 
FIG. 6 illustrates a flow chart of a backward hard handoff process by the 
serving exchange station based on the handoff generation and control 
apparatus 32 when the handoff is generated. When the backward hard handoff 
request message is generated from the target exchange station, namely, 
which is outputted from the opposite exchange station through the handoff 
generation and control apparatus 32 of the serving exchange station like 
the mobile station is moved from the serving exchange station to the 
target exchange station, and then the same is moved from the target 
exchange station to the serving exchange station, the handoff controller 
35 of the serving exchange station receives a backward hard handoff 
request message in Step S71. 
The handoff controller 35 which receives a backward hard handoff request 
message, transmits then backward handoff request signal to the control 
station matching unit 33, and the control station matching unit 33 
requests the handoff generation and control apparatus 32, which acts as a 
control station, to allocate a new wireless resource by using an 
information from the mobile station in Step S72. 
Thereafter, the handoff generation and control apparatus 32 performs a 
preparation operation which is needed for a handoff process such as a 
wireless resource allocation in accordance with the allocation request of 
the wireless resource in Step S72 and transmits a backward hard handoff 
preparation completion message to the target exchange station in Step S73. 
Namely, the handoff generation and control apparatus 32 transmits the 
backward hard handoff preparation completion message to the control 
station matching unit 33, and the control station matching unit 33 reports 
a state that the backward hard handoff control preparation is completed to 
the handoff controller 35. Thereafter, the handoff controller 35 transmits 
a backward hard handoff preparation completion message to the target 
exchange station which transmits a backward hard handoff request signal. 
Meanwhile, if the handoff generation and control apparatus 32 does not 
perform a preparation process which is needed for a handoff process, for 
example, the wireless resource is not allocated in Step S72, the backward 
hard handoff preparation non-completion message is transmitted to the 
target exchange station in Step S74. 
As in Step S73, the response message with respect to the backward handoff 
request, which is a backward hard handoff preparation completion message, 
is transmitted to the target exchange station which requires a backward 
handoff through the handoff controller 35, and the handoff generation and 
control apparatus 32 transmits the backward hard handoff completion 
message outputted from the serving exchange station to the target exchange 
station through the control station matching unit 33 and the handoff 
controller 35 like the mobile station is detected to be in the service 
area of the serving exchange station of a particular base station in Step 
S75. 
The backward hard handoff of the serving exchange station is performed, and 
then the backward hard handoff function between the serving exchange 
station and the target exchange station is tested. 
FIG. 7 illustrates a backward hard handoff process by the target exchange 
station based on the handoff generation and control apparatus 32. After 
the forward handoff is performed toward the target exchange station, when 
the backward hard handoff message is generated through the handoff 
generation and control apparatus 32 of the target exchange station like 
the forward handoff is completed toward the target exchange station, and 
the mobile station is moved to the serving exchange station in which a 
previous call is set, the control station matching unit 33 of the target 
exchange station receives a backward hard handoff generation message in 
Step S81. 
The control station matching unit 33 which receives a backward hard handoff 
generation message from the handoff generation and control apparatus 32 
reports a state that a handoff is repeatedly generated to the handoff 
controller 35, and then the handoff controller 35 which received a 
continuous handoff generation message transmits the backward hard handoff 
request message to the serving exchange station. 
Thereafter, the handoff controller 35 judges whether a response message 
with respect to the backward hard handoff request message from the serving 
exchange station which receives a backward hard handoff request message is 
received in Step S83. 
In Step S83, when the handoff controller 35 receives a response message 
with respect to the backward hard handoff request message from the serving 
exchange station, the handoff controller 35 requests the control station 
matching unit 33 to release the wireless resource and requests the control 
station matching unit 33 to release the information of the wireless 
resource which is allocated to the handoff generation and control 
apparatus 32, so that the wireless resource information that the handoff 
generation and control apparatus allocated is released in Step S84. 
Thereafter, the handoff controller 35 judges whether a backward hard 
handoff completion message is received in Step S85, which message means 
that a backward hard handoff is completed by the serving exchange station. 
When the backward hard handoff completion message is received, the handoff 
controller 35 releases a source which is used during the forward hard 
handoff, and requests the control station matching unit 33 to release the 
source which is used during the forward hard handoff, and then the control 
station matching unit 33 requests the handoff generation and control 
apparatus 32 to release the call process step and releases itself call 
process step in Step 86. 
The handoff generation and control apparatus 32 receives a source release 
message of the control station matching unit 33, thus clearing all data 
and releasing the call process step. 
In addition, in Step S83, the handoff controller 35 does not receive the 
response message with respect to the backward hard handoff request message 
from the serving exchange station, or in Step S84, the handoff controller 
35 does not receive a backward hard handoff completion message from the 
serving exchange station, the in-use state of the system is maintained in 
Step S87. 
The backward hard handoff of the target exchange station is obtained, and 
it is possible to test the backward hard handoff function between the 
serving exchange station and the target exchange station. 
As described above, in the handoff test method between mobile communication 
switching stations according to the present invention, since it is 
possible to test the handoff function between exchange stations by using 
the test handoff signal from the handoff generation and control apparatus 
without moving the mobile in order to test the handoff function, it is 
possible to significantly reduce the number of research members for 
developing the CDMA mobile communication system and time and cost, thus 
more effectively testing the handoff. 
Although the preferred embodiments of the present invention have been 
disclosed for illustrative purposes, those skilled in the art will 
appreciate that various modifications, additions and substitutions are 
possible, without departing from the scope and spirit of the invention as 
recited in the accompanying claims.