Korea Railroad Research Institute

Yong Soo Song

Ju Yeop Kim

Sang Won Choi

Yong Kyu Kim

Yong Gyu Kim

A method of Mission Critical Push to Talk (MCPTT) service performed by a mobile terminal includes: generating, at the mobile terminal, a group call announcement for off-network Mission Critical Push to Talk (MCPTT) service, the group call announcement for off-network MCPTT service including information of a period of the group call announcement for off-network MCPTT service; controlling a transceiver to periodically transmit, to one or more mobile terminals, the group call announcement for off-network MCPTT service based on the period; in response to the transmitted group call announcement for off-network MCPTT service, receiving a response from the one or more mobile terminals; and establishing, based on the response from the one or more mobile terminals, a group call with the one or more mobile terminals by setting a direct wireless communication with the one or more mobile terminals.

Apparatus and method for controlling PTT service by multiplexing call originator and floor arbitrator

A method for transmitting packets by a transmitter in a wireless communication network and retransmitting the packets not received correctly by receivers is discussed. The method includes transmitting the packets to at least two receivers, receiving reception acknowledgement response signals including ACK or NACK signals for the packets transmitted to the receivers, analyzing patterns of the received reception acknowledgement response signals in accordance with a number of the ACK or NACK signals, differently index coding the packets which are not received correctly by each receiver, and retransmitting the index-coded packets.

Growing community of inventors

Uiwang-si, South Korea

Yong Soo Song