Dynamic rate adaptation for wireless multicast

Most communication styles in tactical networks are one-to-many communications, which is multicast transmission. Recently, tactical networks has been evolving to Ad-Hoc-like distributed networks with OFDM-based Wideband Networking Waveform (WNW). In this paper, novel rate-adaptive multicast transmission method over OFDM-based wireless networks is proposed. Transmission rate for wireless multicast over Ad-Hoc Networks has always been the lowest data rate without dynamic link-adaptation. Even though it degrades the performances of networks, implementing dynamic rate adaptation over wireless multicast seems impossible because it causes overhead increasing as a function of the number of member stations. The MAC protocol proposed in this paper utilizes OFDMA mechanism, so that all members can report their rate preferences at one time without increasing overhead. A multicast source is able to find each member´s rate preference from the multiple three-OFDM symbols arrived simultaneously. From the rate-preferences from all members, the source dynamically choose appropriate data rate for upcoming multicast data transmission. As a result, the proposed protocol increases network performances comparing with the multicast transmission using the lowest and constant data rate. It is proven through the extensive simulations.