Abstract: A data re-transmission management scheme capable of improving the communication efficiency. In a data re-transmission from a server to a plurality of terminals through a communication network, any abnormal terminal including a busy terminal and/or a poor performance terminal among the plurality of terminals is detected, and each abnormal terminal is managed separately from other normal terminals, at the server. A management of data transmission and re-transmission from the server to the normal terminals is carried out first, and then a management of a re-transmission of only unreceived data of each abnormal terminal from the server to each abnormal terminal is carried out, after a completion of the data transmission and re-transmission with respect to the normal terminals.

Abstract: A packet scrambling communication scheme capable of reducing the processing amount and the processing time required for the scrambling processing and the descrambling processing at the transmitting side and the receiving side. The original data is scrambled at the transmitting side, by dividing the original data into a plurality of data units in packet sizes, assembling packets by storing the data units into the packets and attaching false packet identifiers indicating a scrambled packet order to the packets, and transmitting the packets in the scrambled packet order according to the false packet identifiers from the transmitting side to the network. The packets received from the network are descrambled at the receiving side, by recovering a data unit order information indicating a descrambled order of the data units from the false packet identifiers, and reconstructing the original data from the data units stored in the packets according to the data unit order information.