Voice over Internet protocol and human-assisted e-commerce

By fostering the finalization of open standards and the convergence of voice, video, and data, the Internet protocol provides an ideal driver for the definition of the infrastructure for new multimedia and advanced communications applications. Voice over IP represents not only the chance to achieve cost-effective real-time voice communication over IP-based networks, but also the opportunity to build an integrated and open communications service delivery infrastructure. Developments of Web-based information systems and IP telephony in order to enable future e-commerce applications are summarized     

Capture-division packet access for wireless personal communications

This paper presents a new architecture for the third-generation mobile systems, capture-division packetized access (CDPA), that overcomes most of the limitations of present cellular systems. It addresses the three main issues of radio access, namely the channel reuse, the multiple access, and the handover problems, in complete adherence to packet-switching principles. The CDPA channel reuse mechanism is a completely new alternative with respect to time-division, frequency-division, or code-division multiple-access (TDMA, FDMA, and CDMA, respectively), which achieve communication parallelism by subdividing the bandwidth a priori among cells. In CDPA, a single frequency channel is used and parallel transmissions are achieved through the “capture” capability of receivers. The hybrid reservation-polling multiple access mechanism used in CDPA is able to integrate any kind of traffic and guarantees almost immediate retransmission of packets that are not captured, thus assuring their correct reception. Finally, the packet-switching approach allows connectionless communications with any base station (BS), and eliminates the need for extra radio traffic in managing handovers. This turns out to be very effective in local area systems where the required high bandwidth is obtained by using a pico-cell structure. We present the CDPA architecture, discuss some implementation issues, and evaluate its performance under a variety of system parameters and operating conditions, using analytical and simulation methods     

On the blocking performance of EGS networks under multicast traffic

Extended generalized shuffle (EGS) networks are a wide class of interconnection networks introduced by Richards (1993). In this work, we study the blocking performance of EGS networks under point-to-multipoint traffic. Two new routing algorithms for multicast connections in EGS networks are defined, and a theorem proving that these algorithms construct minimum-cost connection trees is enclosed. Simulation results show that the blocking performance of EGS networks under multicast traffic is much better than that of three-stage Clos networks of equal complexity     

Reuse partitioning in cellular networks with dynamic channel allocation

Great interest in recent years has been devoted to mobile communications. The research effort has been directed to increasing the capacity of radio systems by applying space reuse techniques. Higher efficiency in the usage of the available frequency spectrum can be obtained either by reducing the cell size, thus requiring the provision of new base stations, or by reusing the available spectrum more efficiently without cell size reduction. In this paper we present a dynamic frequency allocation algorithm for cellular networks that exploits a given reuse pattern. The performance of the proposed scheme, in terms of blocking probability, is evaluated by means of computer simulations both when the position of the mobiles remains unchanged and when mobility is taken into account, under both uniform and hotspot traffic. The numerical results show that the capacity of the proposed scheme is sensibly higher than that of a dynamic channel allocation without reuse partitioning. The effects of both user mobility and reuse partitioning on the signalling load are also considered.     

QoS support for per-flow services: POS vs. IP-over-ATM

Packet-over-Sonet and IP-over-ATM are two ways to build high-speed Internet backbones. The work presented maps the parameters for Internet-standard integrated services onto ATM technical parameters and quantifies the performance of each architecture in terms of admissible connections carrying multimedia traffic. Results suggest that ATM networks will not be competitive with pure IP infrastructures over the long term     

Bounds and Performance Networks of Reuse Partitioning in Cellular

In this paper we study a scheme that allows asmooth increase of the capacity of a cellular system forcircuit switching by applying cell partitioning andusing dynamic channel allocation techniques. A bound is computed for this reuse partitioningscheme that gives the maximum theoretical gainaccomplished in the system bandwidth. The performance ofthe proposed scheme in terms of blocking probability is evaluated both when the position of themobiles remains unchanged and when mobility is takeninto account. The numerical results show that thecapacity of the proposed scheme is sensibly higher than that of a fixed allocation scheme.     

A simple bandwidth management scheme for multiservice ATM networks

In this paper we outline a simple strategy to manage bandwidth allocation and congestion control and to guarantee service requirements in a multiservice ATM (asynchronous transfer mode) network. We propose a network architecture based on a core network, making available a limited number of quality of service profiles, and an access network, made of edge adapters in charge to match the user's requirements with the network's available quality of service profiles and to shape input traffic to achieve high network throughput. The connection admission rule is presented, and edge adapter architecture and design examples are given. The effectiveness of the scheme is demonstrated by numerical results which report the network utilization performance when the proposed core network policies and edge adapter design apply.