CLAIMS 1. A mobile station comprising: a wireless communication unit
to transmit and receive signals to and from a 5 base station and
to measure received quality of downlink signals received from the base station;
a position information acquisition unit to acquire position information on the mobile station; 10 a measurement information management unit to acquire
the position information, received quality information that is measurement result of received quality of downlink signals 15 received from a handover source base station currently connected and a handover destination base station to be connected next, with measuring being performed at the wireless communication unit, and
received quality information that is 20 measurement result of received quality of uplink signals from the mobile station measured at the handover destination base station and of measurement results of received quality of uplink signals acquired by the handover target base station from the handover source base station, 25 and
to store measurement information that is received
quality information on signals transmitted and received
between the mobile station and the base station; and
a communication connection control unit
30 to acquire the position information from the
position information acquisition unit,
to perform a handover when a position of the mobile station is a handover position determined on the

basis of the measurement information, and
to switch base stations to be connected.
2. The mobile station according to claim 1, wherein 5 in an operation mode for determining the handover position, the communication connection control unit
transmits a measurement result request addressed to the handover destination base station a plurality of times via the wireless communication unit while connected
10 to the handover source base station, and
when the communication connection control unit acquires via the wireless communication unit, as a response to the measurement result request, the received quality information on the uplink signals measured at the handover
15 destination base station and also acquires via the handover source base station the received quality information on the uplink signals measured at the handover source base station, the communication connection control unit outputs, to the measurement information management unit, the acquired
20 received quality information on the uplink signals of each base station together with the position information at the time of transmitting the measurement result request acquired from the position information acquisition unit, and
25 the measurement information management unit stores,
for each measurement result request, the position information and the received quality information on the uplink signals of each base station acquired from the communication connection control unit, and
30 the received quality information on the downlink
signals from each base station measured at the time of transmitting the measurement result request acquired from the wireless communication unit.

3. The mobile station according to claim 1 or 2, wherein
in an operation mode for changing the handover
position, the communication connection control unit
5 transmits a measurement result request addressed
to the handover destination base station via the wireless communication unit while connected to the handover source base station before performing a handover at the handover position,
10 acquires via the wireless communication unit, as
a response to the measurement result request, the received quality information on the uplink signals measured at the handover destination base station and also acquires, via the handover source base station, the received quality
15 information on the uplink signals measured at the handover source base station, and
outputs, to the measurement information management unit, the acquired received quality information on the uplink signals of each base station together with
20 the position information at the time of transmitting the measurement result request acquired from the position information acquisition unit, and
the measurement information management unit stores the position information and the received quality information
25 on the uplink signals of each base station acquired from the communication connection control unit as well as the received quality information on the downlink signals from each base station measured at the time of transmitting the measurement result request and the time information on the
30 time of measuring the received quality of the downlink signals acquired from the wireless communication unit.
4. The mobile station according to claim 1, 2, or 3,

Docket No. PMAA-17127-PCT 75
wherein
the communication connection control unit
transmits, via the wireless communication unit, the measurement information to a maintenance device that 5 determines the handover position on the basis of the measurement information or
outputs the measurement information, via a data input/output unit that performs input and output of data with a storage medium, to the storage medium. 10
5. A base station to be connected to the mobile station
according to any one of claims 1 to 4, the base station
comprising:
a wireless communication unit
15 to transmit and receive signals to and from the
mobile station and
to measure received quality of uplink signals received from the mobile station;
a measurement information management unit to acquire 20 and store
received quality information on the uplink signals measured at the wireless communication unit and
time information on time of measuring the received quality of the uplink signals; and 25 a communication connection control unit to perform control such that the received quality information on the uplink signals is transferred.
6. The base station according to claim 5, wherein
30 the wireless communication unit measures received
quality of a measurement result request addressed to the base station received from the mobile station,
the measurement information management unit acquires

Docket No. PMAA-17127-PCT 76
and stores therein
received quality information on the measurement result request of a handover destination base station, which is received quality information on the measurement 5 result request measured at the wireless communication unit and
time information on time of measuring the received quality of the measurement result request, and
the communication connection control unit transmits, 10 via the wireless communication unit, to a handover source base station to which the mobile station is currently connect, a first measurement result that includes the received quality information on the measurement result request of the handover destination base station and the 15 time information on the time of measuring the received quality of the measurement result request ed.
7. The base station according to claim 6, wherein
in a case where the base station is a handover source
20 base station to which the mobile station is currently connected, the wireless communication unit receives the first measurement result addressed to the base station from the handover destination base station, and
the communication connection control unit
25 acquires, from the measurement information
management unit, the received quality information on an uplink signal at a time indicated by the time information on the time of measuring the received quality of the measurement result request included in the first
30 measurement result, and
transmits, to the mobile station via the wireless communication unit, a second measurement result that includes

Docket No. PMAA-17127-PCT 77
the received quality information on the measurement result request of the handover destination base station included in the first measurement result and
the received quality information on the 5 uplink signal acquired from the measurement information management unit.
8. A maintenance device that monitors a state of the
mobile station according to any one of claims 1 to 4, the
10 maintenance device comprising:
a measurement information holding unit to hold the measurement information acquired from the mobile station; and
a handover position control unit to determine a 15 handover position of the mobile station on the basis of the measurement information.
9. The maintenance device according to claim 8, wherein
the handover position control unit determines the
20 handover position such that received quality of uplink
signals in the handover destination base station achieves received quality equal to or more than a handover destination uplink signal received quality threshold.
25 10. The maintenance device according to claim 8 or 9,
wherein
the handover position control unit determines the
handover position such that received quality of downlink
signals in the handover source base station achieves 30 received quality equal to or more than a handover source
downlink signal received quality threshold.
11. The maintenance device according to claim 8, 9, or 10,

Docket No. PMAA-17127-PCT 78
wherein
the handover position control unit determines the handover position such that received quality of downlink signals in the handover destination base station achieves 5 received quality equal to or more than a handover
destination downlink signal received quality threshold.
12. The maintenance device according to any one of claims
8 to 11, wherein
10 the handover position control unit determines the handover position such that received quality of uplink signals in the handover source base station achieves received quality equal to or more than a handover source uplink signal received quality threshold.
15
13. The maintenance device according to any one of claims
8 to 12, comprising:
a measurement information processing unit to select, on the basis of operation information on a train in a case
20 where the mobile station is mounted on the train, a piece of measurement information unusable by the handover position control unit for determining the handover position among pieces of the measurement information held by the measurement information holding unit, wherein
25 the handover position control unit determines the handover position by using usable pieces of measurement information obtained by excluding an unusable piece thereof through a process performed by a measurement information processing unit.
30
14. The maintenance device according to any one of claims
8 to 13, wherein
the handover position control unit

Docket No. PMAA-17127-PCT 79
distributes information on a determined handover position to the mobile station by wireless communication via a base station or
outputs the information on the determined 5 handover position, via a data input/output unit that performs input and output of data to and from a storage medium, to the storage medium.
15. A mobile communication system comprising:
10 the mobile station according to any one of claims 1 to 4;
the base station according to any one of claims 5 to 7; and
the maintenance device according to any one of claims 15 8 to 14, wherein
the maintenance device determines a handover position of the mobile station on the basis of received quality of signals transmitted and received between the mobile station and the base station. 20
16. A handover position determination method for a mobile
communication system comprising a mobile station to measure
received quality of downlink signals received from a base
station, the base station to measure received quality of
25 uplink signals received from the mobile station, and a
maintenance device to monitor states of the mobile station and the base station, the handover position determination method comprising:
a measurement result request step performed by the
30 mobile station of transmitting a measurement result request to a handover destination base station to be connected next, the mobile station being currently connected to a handover source base station;

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a handover destination base station transmission step performed by the handover destination base station of, when the handover destination base station receives the measurement result request, transmitting to the handover 5 source base station, a first measurement result that
includes received quality information on the measurement result request and time information on time of measuring received quality of the measurement result request;
a handover source base station transmission step 10 performed by the handover source base station of
transmitting, to the mobile station, a second measurement result that includes
received quality information on an uplink signal at the handover source base station at a time indicated by 15 the time information on the first measurement result and the received quality information on the measurement result request of the handover destination base station included in the first measurement result;
a measurement information storage step performed by 20 the mobile station of acquiring
position information at a time of transmitting the measurement result request,
received quality information that is measurement 25 result of received quality of downlink signals received from the handover source base station and the handover destination base station, and
from the handover source base station, received quality information on uplink signals measured at the 30 handover destination base station and the handover source base station, and
storing measurement information that is received quality information on signals transmitted and received

Docket No. PMAA-17127-PCT 81
between the mobile station and the base station; and
a handover position determination step performed by the maintenance device of determining a handover position of the mobile station on the basis of the measurement 5 information acquired from the mobile station.