We present a throughput analysis of a multi-address call extraction server in F-NET. The extraction server splits a multi-address call into individual calls. Since the actual operation mechanisms of the server are complicated, it is difficult to directly apply the standard Markov chain technique. Restricting ourselves to the case where the server is offered by a saturated input process, we propose a simple probabilistic method to investigate the departure process of the server and its asymptotic behavior. Numerical examples evaluated by the method are compared with simulations, which demonstrate the accuracy of our modeling approach.

In this paper, we consider a location management scheme using Limited Pointer forwarding from Commonly visited sites (LPC) strategy for Personal Communication Services (PCS) networks. The Commonly Visited Site (CVS) is defined as a site in which a mobile user is found with high probability. A feature of the strategy is that it skips updating location information of the mobile user, provided that the mobile user moves within its CVSs. Such a strategy is expected to significantly reduce the location update cost. We evaluate the location management cost of the LPC scheme by employing a Continuous-Time Markov Chain (CTMC) model. We show that the LPC scheme can reduce the location management cost of a highly mobile user who is found in its CVS with high probability.

We propose a traffic measurement system which uses trap and polling methods. To obtain its performance we consider a queueing model with a single server and evaluate a packet delay. In our multi-cast traffic, packets are modeled as a batch with a batch size distribution {gk}. The batch arrival process is observed as two processes on the basis of batch size. For a batch whose size is more than or equal to a threshold L, the batch will be trapped by our traffic measurement system (in queueing model, it will enter a queue immediately after its arrival). For a batch whose size is less than L, it will be observed at a polling cycle T (in queueing model, it will be temporarily stored in a buffer and all these small batches will be cyclically noticed with a cycle T). We analyze this queueing model by a diffusion approximation and compare the packet delay observed by our traffic measurement system with the L=1 original batch arrival model. Evaluating the results of the diffusion approximation, we illustrate that our traffic measurement system has functions not only to give an accurate estimation of the mean waiting time but also reduce the number of measurements by choosing appropriate parameters L and T.

Stream Control Transmission Protocol (SCTP) is a new transport layer protocol for the next generation Internet. SCTP is a connection-oriented protocol that carries over TCP's features but also supports UDP-like message-oriented data transmission. In this paper, we make use of SCTP's multi-streaming feature to transmit MPEG-4 video efficiently, and evaluate its transmission performance under the policy with/without differentiated retransmission. Moreover, to enhance the communication quality, we extend SCTP multi-streaming to realize selective retransmission policy. Our extension utilizes packet-by-packet timestamps to control retransmission of lost packets. By computer simulation, we show that SCTP can (1) improve the video quality by exploiting the multi-streaming and partial reliability features, (2) enhance the video transmission quality by adjusting SCTP fast retransmit threshold, and (3) SCTP with our selective retransmission extension can further improve the whole performance.

The Medium Access Control (MAC) protocol that uses non-overlapping multiple channels, called the multi-channel MAC protocol, was proposed in order to increase the capacity of ad hoc networks. Since the number of packet interfaces on each node is less than the number of channels in ad hoc networks in general, the node needs to select a suitable channel for data transmission. This means that the multi-channel MAC protocol must be provided with a good channel selection algorithm. In this paper, we design a channel selection algorithm called Conditionally Randomized Channel Selection (CRCS) based on Extended Receiver Directed Transmission (xRDT) protocol that only uses one packet interface. Briefly, CRCS uses the acitve channel for data transmission until the amount of data packets reaches a threshold, at which point it selects one of the available channels other than the active channel. Although CRCS is a very simple channel selection algorithm, by using network simulator we find that CRCS is effective to increase the capacity of ad hoc networks and to keep the load balance of all channels compared to the other channel selection algorithms.

A multi-server system with trunk reservation is studied. The system is offered by two types of customers (class-1 and class-2). They arrive in independent batch Poisson streams and have an exponentially distributed service time. Class-1 customers will be lost or rejected if they find all S servers busy on their arrivals. Class-2 customers will use at most S'=S-R servers and enter a queue with N capacity if they find the number of idle servers less than or equal to R on their arrivals. Here, R is the number of reserved servers for class-1 customers. An example of the system is realized in NTT's facsimile communications network F-NET.