Iterative short packet transmission for multicast wireless communication

We have developed a video distribution system using multicast wireless communication. This system allows for the distribution of a variety of contents including a multicast distribution and a unicast distribution to the geographically limited area by using wireless LAN. It is assumed to be used for distributing advertisements or some useful information at supermarkets, stations, amusement theme parks, and so on. Chief characteristics of the system is that it allows the multiple receivers for simultaniously starting to play a content that has already been stored on them. Multicast wireless communication allows for enabling a base station to communicate with multiple receivers simultaneously. However, by the multicast specification, the retransmission mechanism is not deployed in the event of packet loss. Therefore, in a poor channel condition, multicast communication is not practical because of a high packet error rate. Although it is too difficult to distribute a large size of data simultaneously using multicast wireless communication, it is still possible to distribute just a small size of data simultaneously through multicasting. We propose a method that some short packets including an instruction for starting to play a video would be only transmitted iteratively through multicasting after sending enormous amounts of payloads through unicasting in advance. Our scheme is effective in reducing the instruction packet loss in the radio environment where both random errors and burst errors occur moderately. This paper also shows a calibration method for optimizing repetitive transmission times of an instruction packet so as to increase the probability of successfully sending the instruction packet and to complete the distribution of within a relatively short time.