1. A communication system comprising a frst base station device, a second base station device, and a communication terminal device capable of radio communication with te frst base station device and the second base station device,
wherein the communication terinal device is confgured to communicate with the frst base station device via a frst path fr direct communication with the frst base station device, and via a second path fr communication with the frst base station device through the second base station device,
the communication terminal device is set to transmit, to the frst base station device and the second base station device, trasmission data addressed to the frst base station device when an amount of the transmission data exceeds a predetermined threshold, and to trasmit the transmission data not to the second base station device but to the frst base station device when the amount of the transmission data is smaller than or equal to the theshold, and
the threshold is chaged so that the communication terminal device transmits the transmission data to the frst base station device and the second base station device, when the second base station device is set to communicate with the communication terinal device with radio resources periodically allocated and the amount of the transmission data is smaller than or equal to the threshold.
2. A communication system comprising a frst base station device, a second base station device, and a communication terminal device capable of radio communication with the frst base station device and the second base station device,
wherein the communication terminal device is confgured to communicate wit the frst base station device via a frst path fr direct communication with the frst base

station device, and via a second path for communication with the first base station device through the second base station device,
the communication terminal device is set to transmit, to the first base station device and the second base station device, transmission data addressed to the first base station device when an amount of the transmission data is larger than or equal to a predetermined threshold, and to transmit the transmission data not to the second base station device but to the first base station device when the amount of the transmission data is smaller than the threshold, and
the threshold is changed so that the communication terminal device transmits the transmission data to the first base station device and the second base station device, when the second base station device is set to communicate with the communication terminal device with radio resources periodically allocated and the amount of the transmission data is smaller than the threshold.
3. A communication system comprising a first base station device, a second base station device, and a communication terminal device capable of radio communication with the first base station device and the second base station device,
wherein the communication terminal device is configured to communicate with the first base station device via a first path for direct communication with the first base station device, and via a second path for communication with the first base station device through the second base station device,
the communication terminal device is set to transmit, to the first base station device and the second base station device, transmission data addressed to the first base station device when an amount of the transmission data exceeds a predetermined threshold, and to transmit the transmission data not to the second base station device but

to the first base station device when the amount of the transmission data is smaller than or equal to the threshold, and
the communication terminal device is set to transmit the transmission data to the first base station device and to transmit an end signal to the second base station device, when the second base station device is set to communicate with the communication terminal device with radio resources periodically allocated and the amount of the transmission data is smaller than or equal to the threshold, the end signal representing an end of the communication with the radio resources periodically allocated.
4. A communication system comprising a first base station device, a second base station device, and a communication terminal device capable of radio communication with the first base station device and the second base station device,
wherein the communication terminal device is configured to communicate with the first base station device via a first path for direct communication with the first base station device, and via a second path for communication with the first base station device through the second base station device,
the communication terminal device is set to transmit, to the first base station device and the second base station device, transmission data addressed to the first base station device when an amount of the transmission data is larger than or equal to a predetermined threshold, and to transmit the transmission data not to the second base station device but to the first base station device when the amount of the transmission data is smaller than the threshold, and
the communication terminal device is set to transmit the transmission data to the first base station device and to transmit an end signal to the second base station device, when the second base station device is set to communicate with the communication

terminal device with radio resources periodically allocated and the amount of the transmission data is smaller than the threshold, the end signal representing an end of the communication with the radio resources periodically allocated.
5. The communication system according to claim 3 or 4,
wherein the communication terminal device stops releasing the radio resources periodically allocated upon receipt of release stop information indicating stopping release of the radio resources periodically allocated.
6. The communication system according to claim 5,
wherein the communication terminal device resumes releasing the radio resources periodically allocated upon receipt of release resuming information indicating resuming release of the radio resources periodically allocated.