We propose two fault-tolerant broadcasting schemes in star graphs. One of the schemes can tolerate up to n2 faults of the crash type in the n-star graph. The other scheme can tolerate up to (n3d1)/2 faults of the Byzantine type in the n-star graph, where d is the smallest positive integer satisfying nd!. Each of the schemes is designed for the single-port mode, and it completes the broadcasting in O(n log n) time. These schemes are time optimal. For the former scheme we analyze the reliability in the case where faults of the crash type are randomly distributed. It can tolerate (n!)α faults randomly distributed in the n-star graph with a high probability, where α is any constant less than 1.

A novel combinatorial optimization algorithm called "Gradual neural network (GNN)" is presented for NP-complete broadcast scheduling problems in packet radio (PR) networks. A PR network provides data communications services to a set of geographically distributed nodes through a common radio channel. A time division multiple access (TDMA) protocol is adopted for conflict-free communications, where packets are transmitted in repetition of fixed-length time-slots called a TDMA cycle. Given a PR network, the goal of GNN is to find a TDMA cycle with the minimum delay time for each node to broadcast packets. GNN for the N-node-M-slot TDMA cycle problem consists of a neural network with N M binary neurons and a gradual expansion scheme. The neural network not only satisfies the constraints but also maximizes transmissions by two energy functions, whereas the gradual expansion scheme minimizes the cycle length by gradually expanding the size of the neural network. The performance is evaluated through extensive simulations in benchmark instances and in geometric graph instances with up to 1000 vertices, where GNN always finds better TDMA cycles than existing algorithms. The result in this paper supports the credibility of our GNN algorithm for a class of combinatorial optimization problems.

We have investigated the operation of a reflection type magnetostatic wave signal-to-noise enhancer in detail. It has good enhancement characteristics, low insertion loss, and low operating power. It is also composed of a transducer using a ceramic substrate having a high dielectric constant and an LaGa-YIG film with low saturation magnetization to enable direct operation in the 400-MHz band (the IF band of current DBS receivers). Enhancement of 8 dB was achieved over a 40-MHz bandwidth. Although its operating frequency range depends critically on device temperature, we can compensate for the temperature dependence by adjusting the bias magnetic field. Experiments showed that the enhancer improved the received carrier-to-noise ratio by 2 to 3 dB, providing good noise reduction in DBS reception.

This paper reviews the hyper-media photonic information network (HM-PIN) concept as a candidate of innovative future networks based on photonic technologies. The HM-PIN having a universal network interface integrates a variety of information services: telecommunications, newspapers, magazines, TV broadcasts and the growing collection of information servers. This network fundamentally offers three items: (1) bi-directional real-time channels with 10-Mbit/s-class or higher bit rate, (2) multipoint connections including multicasting/broadcasting, (3) high accessibility to information. These items are derived from the constraints of the conventional telephone networks and the Internet. By applying photonic technologies, the HM-PIN can be implemented as follows: The local network (the service platform) of the HM-PIN can be achieved by using a wavelength-division-multiplexing (WDM) broadcast-and-select (B&S) architecture that offers broadband multipoint connections (one-to-many, many-to-many) based on an inherent full-mesh topology. The WDM B&S local network will be able to support 10,000 to 100,000 channels (each with 10-Mbit/s or more bandwidth) by using optical and electrical multiplexing techniques. The backbone network can be constructed by combining photonic asynchronous transfer mode (ATM) switching systems and WDM transmission systems (including cross-connects). Two deployment scenarios of the HM-PIN (cost-oriented and service-oriented deployment scenarios) are also described for smoothly introducing the HM-PIN even before the cost issue is solved. The HM-PIN based on photonic technologies will be a future network service platform that greatly enhances communication services.

This paper describes the implementation and demonstration of local networks for the hyper-media photonic information network (HM-PIN), a candidate for the information service platform offering broadcast and telecommunication services. In addition, the feasibility of the HM-PIN is also demonstrated using prototype local network systems. This local network adopts architecture based on wavelength-division-multiplexing (WDM) and broadcast-and-select (B&S) switching, and supports all HM-PIN services except inter-local-network communication. The major issues of this proposed network are the technologies that support many broadcast channels and reduce channel selection cost. This paper also considers the combination of WDM technology and three alternatives: electrical TDM, subcarrier multiplexing (SCM or electrical FDM), and optical TDM (O-TDM). Three 128 ch (8 wavelengths 16 channels) WDM B&S prototype systems are built to demonstrate the feasibility of the proposed HM-PIN. In WDM/SCM, 30 and 20 Mb/s channels are realized as 16-QAM and 64-QAM, and 155 Mb/s channels are realized by WDM/TDM. Moreover, these three prototypes were connected to form a small HM-PIN and applications such as video distribution and IP datagram cut-through are demonstrated. Furthermore, the delay and throughput of the HM-PIN are evaluated by connecting a local network to a 200-km WDM-ring backbone network. Our discussions and demonstrations confirm the impact and feasibility of the proposed hyper-media photonic information network.

This paper presents large capacity switching systems for a local network using the broadcast-and-select (B&S) architecture. The B&S switching system, based on optical time-division multiplexing (OTDM), can provide several hundreds of Gbit/s by using a nonlinear optical switch as the time-channel selector. Moreover, the combination of OTDM and wavelength-division multiplexing (WDM) can realize throughputs over Tbit/s. In experiments, first, all-optical selection from a 51.2-Gbit/s data-stream to yield a 160-Mbit/s data-channel is demonstrated for a B&S OTDM switching system. Second, all-optical selection from a 25.6-Gbit/s 2 (51.2-Gbit/s) WDM data-stream to yield a 160-Mbit/s data-channel is demonstrated for a B&S OTDM and WDM switching system. Finally, the number of optical amplifiers that one user has to share in the B&S OTDM switching system is discussed.

This paper reviews the hyper-media photonic information network (HM-PIN) concept as a candidate of innovative future networks based on photonic technologies. The HM-PIN having a universal network interface integrates a variety of information services: telecommunications, newspapers, magazines, TV broadcasts and the growing collection of information servers. This network fundamentally offers three items: (1) bi-directional real-time channels with 10-Mbit/s-class or higher bit rate, (2) multipoint connections including multicasting/broadcasting, (3) high accessibility to information. These items are derived from the constraints of the conventional telephone networks and the Internet. By applying photonic technologies, the HM-PIN can be implemented as follows: The local network (the service platform) of the HM-PIN can be achieved by using a wavelength-division-multiplexing (WDM) broadcast-and-select (B&S) architecture that offers broadband multipoint connections (one-to-many, many-to-many) based on an inherent full-mesh topology. The WDM B&S local network will be able to support 10,000 to 100,000 channels (each with 10-Mbit/s or more bandwidth) by using optical and electrical multiplexing techniques. The backbone network can be constructed by combining photonic asynchronous transfer mode (ATM) switching systems and WDM transmission systems (including cross-connects). Two deployment scenarios of the HM-PIN (cost-oriented and service-oriented deployment scenarios) are also described for smoothly introducing the HM-PIN even before the cost issue is solved. The HM-PIN based on photonic technologies will be a future network service platform that greatly enhances communication services.

This paper describes the implementation and demonstration of local networks for the hyper-media photonic information network (HM-PIN), a candidate for the information service platform offering broadcast and telecommunication services. In addition, the feasibility of the HM-PIN is also demonstrated using prototype local network systems. This local network adopts architecture based on wavelength-division-multiplexing (WDM) and broadcast-and-select (B&S) switching, and supports all HM-PIN services except inter-local-network communication. The major issues of this proposed network are the technologies that support many broadcast channels and reduce channel selection cost. This paper also considers the combination of WDM technology and three alternatives: electrical TDM, subcarrier multiplexing (SCM or electrical FDM), and optical TDM (O-TDM). Three 128 ch (8 wavelengths 16 channels) WDM B&S prototype systems are built to demonstrate the feasibility of the proposed HM-PIN. In WDM/SCM, 30 and 20 Mb/s channels are realized as 16-QAM and 64-QAM, and 155 Mb/s channels are realized by WDM/TDM. Moreover, these three prototypes were connected to form a small HM-PIN and applications such as video distribution and IP datagram cut-through are demonstrated. Furthermore, the delay and throughput of the HM-PIN are evaluated by connecting a local network to a 200-km WDM-ring backbone network. Our discussions and demonstrations confirm the impact and feasibility of the proposed hyper-media photonic information network.

This paper presents large capacity switching systems for a local network using the broadcast-and-select (B&S) architecture. The B&S switching system, based on optical time-division multiplexing (OTDM), can provide several hundreds of Gbit/s by using a nonlinear optical switch as the time-channel selector. Moreover, the combination of OTDM and wavelength-division multiplexing (WDM) can realize throughputs over Tbit/s. In experiments, first, all-optical selection from a 51.2-Gbit/s data-stream to yield a 160-Mbit/s data-channel is demonstrated for a B&S OTDM switching system. Second, all-optical selection from a 25.6-Gbit/s 2 (51.2-Gbit/s) WDM data-stream to yield a 160-Mbit/s data-channel is demonstrated for a B&S OTDM and WDM switching system. Finally, the number of optical amplifiers that one user has to share in the B&S OTDM switching system is discussed.

An architecture is presented for efficient and reliable delivery of multimedia contents from a primary center (PC) to secondary centers (SCs). Requested contents are delivered from the PC to the SCs through a satellite broadcast channel, or from one SC to another SC through a terrestrial channel. Cycling methods are presented that enable sharing of the contents directory of each SC. Several fundamental models and algorithms are introduced for possible consideration during the planning and design of a contents-delivery system. Simulation has shown that using both satellite broadcast and terrestrial channels for contents delivery is superior in terms of cost to the conventional use of only a satellite network.

This paper proposes local lightwave networks with grouping property which are based on a wavelength division multiplexing (WDM). The proposed network is partitioned into several groups according to traffic volume between stations so that traffic is more likely to be within groups. The stations within a group are connected to a broadcast-and-select WDM network with star topology. For inter-group communication, a WDM network of each group is connected to another star-topology WDM network through a special station called a router. In the proposed network, intra-group communication is achieved by one hop and inter-group communication goes through multiple hops. We analyze the average hop number, the maximum throughput, and the mean packet delay of the proposed network and investigate its performance characteristics. Since the proposed network has the better performance as its grouping property strengthens, it is fit for local lightwave networks with the locality of traffic.

Unequal error protection (UEP) is a very promising coding technique for satellite broadcasting, as it gradually reduces the transmission rate. From the viewpoint of bandwidth efficiency, UEP should be achieved in the context of multilevel coded modulation. However, the conventional mapping between encoded bits and modulation signals, usually realized for multilevel block modulation codes and multistage decoding, is not very compatible with UEP coding because of the large number of resulting nearest neighbor codewords. In this paper, new coded modulation schemes for UEP based on unconventional partitioning are proposed. A linear operation referred to as interlevel combination is introduced. This operation generalizes previous partitioning proposed for UEP applications and provides additional flexibility with respect to UEP capabilities. The error performance of the proposed codes are evaluated both by computer simulations and a theoretical analysis. The obtained results show that the proposed codes achieve good tradeoff between the proportion and the error performance of each error protection level.

Almost all broadcasting systems and their equipment would be digitalized in the near future. In Japan, investigation of digital broadcasting has been going on for a long time, aiming at a realization of improvement of picture quality, new services, system flexibility, etc. Japanese digital broadcasting systems under development have a lot of technical merits, for example, a high transmission capacity and a hierarchical transmission scheme for satellite, and mobile reception for terrestrial digital broadcasting systems, compared to conventional digital systems.

Let T1, , Tn be n spanning trees rooted at node r of graph G. If for any node v, n paths from r to v, each path in each spanning tree of T1, , Tn, are internally disjoint, then T1, , Tn are said to be independent spanning trees rooted at r. A graph G is called an n-channel graph if G has n independent spanning trees rooted at each node of G. We generalize the definition of n-channel graphs. If for any node v of G, among the n paths from r to v, each path in each spanning tree of T1, , Tn, there are k internally disjoint paths, then T1, , Tn are said to be (k,n)-independent spanning trees rooted at r of G. A graph G is called a (k,n)-channel graph if G has (k,n)-independent spanning trees rooted at each node of G. We study two fault-tolerant communication tasks in (k,n)-channel graphs. The first task is reliable broadcasting. We analyze the relation between the reliability and the efficiency of broadcasting in (k,n)-channel graphs. The second task is secure message distribution such that one node called the distributor attempts to send different messages safely to different nodes. We should keep each message secret from the nodes called adversaries. We give two message distribution schemes in (k,n)-channel graphs. The first scheme uses secret sharing, and it can tolerate up to t+k-n listening adversaries for any t < n if G is a (k,n)-channel graph. The second scheme uses unverifiable secret sharing, and it can tolerate up to t+k-n disrupting adversaries for any t < n/3 if G is a (k,n)-channel graph.

This paper introduces a new analytic method that uses modified state equations to evaluate the performance of PCSD (Packet Channel Sharing protocol for DCA systems) with the goal of increasing the spectrum efficiency of DCA systems by realizing channel sharing between circuit-switched calls and packets. The results of this analysis show that PCSD is more suitable for microcellular systems than cellular systems, and that PCSD system performance improves as the average holding time of circuit-switched calls increases. Moreover, this paper proposes a novel scheme to determine the optimum release delay time of packet channels in order to achieve high throughput for packets as well as high channel capacity for circuit-switched calls. The proposed scheme shows that the optimum release delay time for PHS (Personal Handy-phone System) is greater than 60 frames and less than 100 frames.

In the multipath mobile channel, the received signal suffers from both the fluctuation in the received field intensity caused by fading and waveform distortion caused by the echo. Diversity reception using multiple spaced antennas is an effective method to compensate for fading, while echo cancellation with an adaptive array is good at compensating for waveform distortion. In this paper, an adaptive switching echo cancellation/diversity reception method to compensate for both waveform distortion and fading is proposed. The proposed switching reception monitors the impacts of channel conditions on received signal and then one of an echo canceller and a diversity receiver is selected accordingly to compensate the channel. The compensation performance of the proposed switching reception in terms of both average DUR (Desired to Undesired signal Ratio) and the probability of DUR below a threshold value is investigated with computer simulation. The results show that the adaptive switching echo cancellation/diversity reception has realized the advantages of both adaptive echo cancellation and diversity reception.

In this paper, we propose a high performance highly modular ATM switch architecture known as Bodhi which is suitable for small, large, and very large size ATM switch implementations. Its basic configuration consists of two stages: an input stage and an output stage. The input stage consists of input group modules (IGMs) and output stage output group modules (OGMs). Each IGM-OGM pair is connected by multiple paths which carry cells from IGMs to OGMs. Excess cells at the IGMs are recycled to minimize the cell loss probability. Another module called recirculation module is used to couple several IGMs together to create additional routes for recirculating cells which gives this architecture robustness against nonuniform and directed traffic. Multicasting has been implemented by integrating copying and broadcasting techniques, and using some novel techniques to minimize the switch complexity. A shared buffer architecture is employed for OGMs such that it implements multiple priorities dynamically in a weighted manner, requires no speedup, and, can function in standalone mode as small switches. The performance of Bodhi has been evaluated by computer simulation to select design parameters for a 1k 1k (k=1024) switch fabric. It allows growability from 2. 4 gigabit to 150 gigabit switch, and, expandability to 100+ Terabit switch with the complexity increasing approximately linearly with size. Based on the study presented in this paper, it is seen that the Bodhi architecture offers a high degree of modularity, weighted dynamic priority control, robustness against nonuniform traffic conditions, low complexity, low latency, and, supports multicasting efficiently and without any limitation. Bodhi, therefore, has high potential for application in high speed broadband networks.

This work is targeted to understand the operating principle of the feedback type echo canceller for use in an FM broadcasting receiver and to study its compensating features and the effects of the practical operating environment on its performance. The effects of the tap interval and the compensation performance in the presence of an echo with excess delay 0 - 15 µs are examined. The results show that the tap interval should be selected according to the observable bandwidth of the channel transfer function and the performance of a feedback type echo canceller has a wavelike curve with respect to the excess delay of the echo. To improve the performance of the feedback type echo canceller, an adaptive echo canceller operating with CM algorithm is proposed and examined with computer simulation. The results show that the compensation performance is improved.

The construction of fault-tolerant processor arrays with interconnections of cube-connected cycles (CCCs) by using an advanced spare-connection scheme for k-out-of-n redundancies called "generalized additional bypass linking" is described. The connection scheme uses bypass links with wired OR connections to spare processing elements (PEs) without external switches, and can reconfigure complete arrays by tolerating faulty portions in these PEs and links. The spare connections are designed as a node-coloring problem of a CCC graph with a minimum distance of 3: the chromatic numbers corresponding to the number of spare PE connections were evaluated theoretically. The proposed scheme can be used for constructing various k-out-of-n configurations capable of quick broadcasting by using spare circuits, and is superior to conventional schemes in terms of extra PE connections and reconfiguration control. In particular, it allows construction of optimal r-fault-tolerant configurations that provide r spare PEs and r extra connections per PE for CCCs with 4x PEs (x: integer) in each cycle.

A graph G is called an n-channel graph at vertex r if there are n independent spanning trees rooted at r. A graph G is called an n-channel graph if G is an n-channel graph at every vertex. Independent spanning trees of a graph play an important role in fault-tolerant broadcasting in the graph. In this paper we show that if G1 is an n1-channel graph and G2 is an n2-channel graph, then G1G2 is an (n1 + n2)-channel graph. We prove this fact by a construction of n1+n2 independent spanning trees of G1G2 from n1 independent spanning trees of G1 and n2 independent spanning trees of G2. As an application we describe a fault-tolerant broadcasting scheme along independent spanning trees.