Existing reliable multicast protocols are designed to perform well in wired networking environments. However, in mobile networking environments, these reliable mobile multicast protocols are not optimal as they do not take into account the limitations of power (energy), storage capacity, processing power, impairments of wireless communication channels, and the frequent changes of location and the resulting loss of network connectivity. This paper analyses four hybrid reliable multicast schemes, namely NAK-based schemes, ACK-based schemes, ACK-based schemes with FEC (Forward Error Correction), and NAK-based schemes with FEC that are suitable for mobile networking environments and quantifies their performance. These four schemes differ from the generic sender-initiated and receiver-initiated reliable multicast protocols in that they rely on a mixture of multicasting and unicasting for providing reliability. This analysis is used to show that NAK-based schemes with FEC is best suited for reliable multicasting in mobile environments as they provide excellent performance in terms of average wireless channel utilization and average processing time, independently of the number of MHs.

In this paper, we propose the design of a scalable reliable mobile multicast scheme--SRMoM. SRMoM uses well-known Scalable Reliable Multicast (SRM) in the wired networks and a NAK-based ARQ with adaptive Forward Error Correction (AFEC) in the wireless networks. In AFEC, the probability of needing retransmission of original multicast packets after FEC recovery is selectable. This selective property enables the control of channel utilization in the wireless segment for different numbers of Mobile Hosts (MHs). Using this property, the channel utilization of SRMoM is made to be virtually independent of the number of MHs, thus making it extremely scalable. The performance of SRMoM is analyzed with three adaptive FEC algorithms based on three wireless loss models, namely a Gilbert-Elliott channel, a simplified Gilbert-Elliott channel, and a binary symmetric channel, analytically as well as through simulation. Furthermore, the performance of SRMoM is compared with SRM and MRMoM (NAK-based protocol without FEC) through simulation. Using the average number of transmissions per original multicast packet, and wireless link utilization as metrics, we demonstrate that the performance of SRMoM is indeed virtually independent of the number of MHs, and that it results in the lowest number of packet transmissions and lowest channel utilization of reliable mobile multicast protocols that have been proposed to date.

This paper considers a design method of a discrete-time adaptive output feedback control system with a feedforward input based on almost strict positive realness (ASPR-ness). The proposed scheme utilizes the property of ASPR of the controlled plant, and the reference signal is used as feedforward input. The parallel feedforward compensator (PFC) which renders an ASPR augmented controlled plant is also investigated. Besides, it is shown that the output of original plant can track reference signal perfectly without any steady state error. The effectiveness of the proposed scheme is confirmed through a pilot-scale temperature control system.