The performance of various ARQ protocols has recently been analyzed for multidestination environments. In all previous work, the round-trip delays between the transmitter and each of the receivers are assumed (or forced) to be equal to the maximum one, to simplify the analysis and/or the operation. This assumption obviously will sacrifice the system performance. In this paper, we evaluate the throughput efficiencies of three multidestination GBN ARQ protocols under unequal round-trip delays. In the investigated protocols, multiple copies of each data block are (re)transmitted contiguously to the receivers. Tight lower bounds are obtained for the throughput efficiencies of the schemes in which each data block is transmitted with the optimum number of copies. Results show that assuming all the round-trip delays to be equal to the maximum one may sacrifice the performance significantly. We also compare the performances of the three investigated protocols. In general, the performance becomes better as the transmitter utilizes more of the outcomes of previous transmission attempts.

In the future, it will be necessary that robot technology or environmental technology has an auditory function of recognizing sound expect for speech. In this letter, we propose a recognition system for the species of birds receiving birdcalls, based on network technology. We show the first step of a recognition system for the species of birds, as an application of a recognition system for environmental sound.

This paper briefly considers future broadcasting technologies, including digital television as a system for the near future and three-dimensional television as a part of a system to be developed rather later. However, due to limitations of space, this paper discusses only video technologies in detail. First, the status of bit reduction technologies for digital television is described and then satellite digital broadcasting and terrestrial digital broadcasting are also discussed. The authors stress the necessity of the further development of digital video compression technologies. Later, we discuss three-dimensional television, we describe requirements for the service and the present status of the technologies. And last, the paper considers the future prospects for a three-dimensional television service.

With the arrival of B-ISDN, point-to-point routing alone is no longer adequate. A new class of computer and video related services, such as mass mailing, TV broadcasting, teleconferencing, and video 900 service, requires the network to handle multiple destination routing (MDR). Multiple destination routing enables widespread usage of multipoint services at a lower cost than networks using point-to-point routing. With this in mind, network providers are researching more into MDR algorithms. However, the MDR problem itself is very complex. Furthermore, its optimal solution, the Steiner tree problem, is NP-complete and thus not suitable for real-time applications. Recently, various algorithms which approximate the Steiner tree problem have been proposed and, in this invited paper, we will summarize the simulation results of these algorithms. But first, we will define the MDR problem, the issues involved, and the benchmark used to compare MDR algorithms. Then, we will categorize the existing MDR algorithms into a five-level classification tree. Lastly, we will present various published results of static algorithms and our own simulation results of quasi-static algorithms.

We discuss fault tolerance of an information disseminating scheme, t-disseminate on a network with N processors, where each processor can send a message to t directions at each round. When N is a power of t+1 and at most tlogt+1N-1 (at most t) processors and/or edges have hailed, logt+1N+(f1)/t rounds (logt+1N+2 rounds) suffice for broadcasting information to all destinations from any source by t-disseminate. For a arbitrary N, logt+1N2f/t1 rounds (logt+1N+2 rounds) suffice for broadcasting information to all destinations from any source by t-disseminate if at most t(logt+1N1)/2 (at most t/2) processors and/or edges have failed.

Weather conditions affect the performance of satellite broadcasting receiving systems. For example, snow accretion on antennas degrades G/T seriously because it reduces received signal power and also can increase antenna noise. We need a continuous measurement of G/T to evaluate the effect of the weather conditions to the satellite broadcasting receiving systems. However, a conventional method cannot perform the continuous measurement because the antenna under test must be oriented in a specific direction (to the zenith) to obtain a noise level in a satellite broadcasting channel. This paper presents the continuous measurement of G/T for the satellite broadcasting receiving systems. We describe details of the measurement method. In our measurement system, a standard antenna is placed at the inside of a room in order to prevent the weather conditions from affecting the gain of the standard antenna. The power flux density at the inside of the room is different from that at the outside where the antennas under test are placed. Employing the effective gain of the standard antenna, we take the difference of the power flux density into account. Moreover, we propose a method to estimate the noise level in the satellite broadcasting channel from the values at the outside of the channel, and clarify the accuracy of the noise estimation. Then, we show measurement results of the G/T values for several receiving systems. From these results, we show that the G/T measurement system has high precision. Also, from the specifications of the antenna gain and typical values of the noise figure, it is expected that the measurement system has a sufficient accuracy.

We present schemes for disseminating information in the n-dimensional hypercube with some faulty nodes/edges. If each processor can send a message to t neighbors at each round, and if the number of faulty nodes/edges is k(kn), then this scheme will broadcast information from any source to all destinations within any consecutive n+[(k+l)/t] rounds. We also discuss the case where the number of faulty nodes is not less than n.

We describe two information disseminating schemes, t-disseminate and t-Rdisseminate in a computer network with N processors, where each processor can send a message to t-directions at each round. If no processors have failed, these schemes are time optimal. When at most t processors have failed, for t1 and t2 any of these schemes can broadcast information within any consecutive logt+1N2 rounds, and for an arbitrary t they can broadcast information within any consecutive logt+1N3 rounds.