Radio communication system, common reception apparatus and user terminal
To suppress reduction in system performance for mobile communications (group mobility) in a plurality of terminals existing inside the same moving object, a radio communication system for a plurality of user terminals existing inside a moving object and a radio base station is described. The user terminal receives a signal transmitted from the radio base station, and transmits the signal transmitted from the radio base station to a common reception apparatus disposed inside the moving object. The common reception apparatus detects a signal for each user terminal, based on signals transmitted from the plurality of user terminals, and transmits the detected signal to each user terminal. The user terminal receives the signal for the user terminal detected in the common reception apparatus to demodulate. Thus, for group mobility, it is possible to cancel interference among user terminals to improve the multiplexing effect, while suppressing communication overhead.
1. A radio communication system comprising:
a plurality of user terminals that exist inside a moving object; and
a common reception apparatus disposed inside the moving object;
wherein each of the user terminals comprises:
a first receiver that receives a signal transmitted from a radio base station; and
a first transmitter that transmits, to the common reception apparatus, a signal transmitted from the radio base station,
wherein the common reception apparatus comprises:
a second receiver that receives signals transmitted from the user terminals;
a second processor that detects, by using the signals received from the user terminals, a signal addressed to each user terminal; and
a second transmitter that transmits the detected signal to a corresponding user terminal, and
wherein the first receiver receives a signal transmitted from the common reception apparatus,
wherein each of the user terminals further comprises a first processor that demodulates the signal transmitted from the common reception apparatus,
wherein the first processor of a user terminal of the plurality of user terminals time-multiplexes an orthogonal coding sequence into the signal transmitted from the radio base station to transmit to the common reception apparatus,
wherein the second processor of the common reception apparatus estimates a channel state of a radio link,
wherein the second processor of the common reception apparatus estimates a channel state of a radio link between the user terminal and the common reception apparatus, based on the orthogonal coding sequence included in the signal transmitted from the user terminal,
wherein the second processor of the common reception apparatus detects a signal for a predetermined user terminal selected, as a common reception target to perform common reception processing, from among the plurality of user terminals that exist inside the moving object, and
wherein the common reception target is selected from the plurality of user terminals such that a smaller value between reception quality of a radio link between the radio base station and the predetermined user terminal and reception quality of a radio link between the predetermined user terminal and the common reception apparatus is a predetermined value or more.
2. The radio communication system according to claim 1 , wherein based on the signal received from the radio base station included in the signal transferred from a user terminal of the plurality of user terminals, the second processor of the common reception apparatus estimates a channel state of a radio link between the radio base station and the user terminal.
3. The radio communication system according to claim 1 , wherein the second processor of the common reception apparatus performs Successive Interference Cancellation (SIC) on the signals transmitted from the plurality of user terminals to detect a signal for each user terminal.
4. The radio communication system according to claim 1 , wherein the radio base station performs beam forming for the plurality of user terminals, and thereby performs spatial division multiplexing to transmit a signal.
5. A common reception apparatus used in radio communications between a plurality of user terminals that exist inside a moving object and a radio base station, comprising:
a receiver that receives signals transmitted from the radio base station via the plurality of user terminals;
a processor that detects, by using the signals received from the user terminals, a signal addressed to each user terminal; and
a transmitter that transmits the detected signal to a corresponding user terminal,
wherein the common reception apparatus is disposed inside the moving object,
wherein a user terminal of the plurality of user terminals time-multiplexes an orthogonal coding sequence into the signal transmitted from the radio base station to transmit to the common reception apparatus,
wherein the processor estimates a channel state of a first radio link,
wherein the processor estimates a channel state of a second radio link between the user terminal and the common reception apparatus, based on the orthogonal coding sequence included in the signal transmitted from the user terminal,
wherein the processor detects a signal for a predetermined user terminal selected, as a common reception target to perform common reception processing, from among the plurality of user terminals that exist inside the moving object, and
wherein the common reception target is selected from the plurality of user terminals such that a smaller value between reception quality of a radio link between the radio base station and the predetermined user terminal and reception quality of a radio link between the predetermined user terminal and the common reception apparatus is a predetermined value or more.
6. The common reception apparatus according to claim 5 ,
wherein the processor estimates a channel state of a radio link between a user terminal of the plurality of user terminals and the common reception apparatus, based on an orthogonal coding sequence included in a signal transmitted from the user terminal, and
wherein the orthogonal coding sequence is time-multiplexed into a signal transmitted from the radio base station by the user terminal, and is transmitted from the user terminal to the common reception apparatus.
7. A user terminal that exists inside a moving object and that communicates with a radio base station, comprising:
a receiver that receives a signal from the radio base station; and
a transmitter that transmits to a common reception apparatus disposed inside the moving object, the signal transmitted from the radio base station, wherein
the signal transmitted by the transmitter is received by the common reception apparatus,
a signal addressed to the user terminal is detected from the signal received by the common reception apparatus and is transmitted from the common reception apparatus to the user terminal,
the receiver receives the signal addressed to the user terminal that is transmitted from the common reception apparatus, and
the user terminal further comprises a processor that demodulates the signal addressed to the user terminal that is transmitted from the common reception apparatus,
wherein processor time-multiplexes an orthogonal coding sequence into the signal transmitted from the radio base station to transmit to the common reception apparatus,
wherein the common reception apparatus estimates a channel state of a first radio link,
wherein the common reception apparatus estimates a channel state of a second radio link between the user terminal and the common reception apparatus, based on the orthogonal coding sequence included in the signal transmitted from the user terminal,
wherein the common reception apparatus detects a signal for a predetermined user terminal selected, as a common reception target to perform common reception processing, from among a plurality of user terminals that exist inside the moving object, and
wherein the common reception target is selected from the plurality of user terminals such that a smaller value between reception quality of a radio link between the radio base station and the predetermined user terminal and reception quality of a radio link between the predetermined user terminal and the common reception apparatus is a predetermined value or more.