A transmission line created by cables adjoined by connectors is influenced by noise from connectors with contact failure, and such noise degrades communication quality. The authors used a model of a connector with increased contact resistance in a coaxial cable and measured the electromagnetic near-field around a cable while changing positions of the model. In this paper, the result shows that the radiated electromagnetic field has no relationship with the position along the cable of a connector with increased contact resistance, when the contact condition of connector, contact resistance value, measurement position, and length of a transmission line are constant.

When contact failure occurs in a connector in a coaxial HF signal transmission line, an electromagnetic field is radiated around the line. We have measured the electromagnetic field and examined the characteristics of such radiation. The results show that the radiation is related to the contact resistance and the symmetry of the distribution of contact points at the connector. When contact resistance is low, radiation is observed at resonant frequencies related to the length of the transmission line. If a connector has axially asymmetric contact points, its radiation is higher than that when the contact points are symmetric. We show that if contact points in a connector are axially symmetrical with resistance lower than 0.25 Ω, the electromagnetic interference caused by the connector contact failure is as low as the background noise.

In this paper, we report on the transmission characteristics of transformers of a RF splitter widely used in CATV systems. From the point of view of broadening the splitter's operating frequency, the relationship between the RF transformer's transmission characteristics and design parameters has been investigated using computer-aided engineering. Based on the calculations, a sample device has been fabricated to confirm the theoretical results. It has been found that the configulation of the transformer winding is the most important factor affecting device performance. By selecting the appropriate winding, excessive loss can be suppressed to less than 1.6 dB and 3 dB in a frequency range of 20 MHz to 2,600 MHz for the cases of 2-way and 4-way splitters, respectively.

This paper starts by describing the advantages of cascaded modulation, i.e., using multiple concatenated external modulators to modulate CW (Continuous Wave) light. Next, the paper examines computer simulations of the resulting modulated light waveform shapes and intermodulation distortion values to elucidate the basic modulation characteristics of a cascaded modulation scheme. Examples of applying cascaded modulation to a multi-channel optical signal transmission system are shown, and the characteristics are clarified by optical transmission experiments. For example, the dependency of the signal quality on the modulation depth values of each external modulator is clarified. Moreover, experiments show that cascaded modulation permits the remote insertion of local broadcast programs into wide area broadcast programs. Last, the paper shows that cascaded modulation offers better modulation properties than the conventional single modulation approach.

We propose a scheme by which Broadcast Satellite/Communication Satellite- radio frequency (BS/CS-RF) converted TV signals are transmitted over optical fiber, and also propose a simultaneous Frequency Modulation (FM) converted CATV and BS/CS-RF converted TV optical transmission system as one of its applications. To confirm the proposals, we demonstrate the simultaneous transport of FM converted CATV signals and BS/CS-RF converted TV signals over a single optical fiber. In the experiments, 40 carriers of AM-VSB CATV channels, 30 carriers of 64-QAM digital TV channels, 8 carriers of FM/TC8PSK BS-TV channels, and 12 carriers of QPSK CS-TV channels are simultaneously transmitted. For optical access network application, the practical transmission length of 15 km over 1.3 µm-zero-dispersion optical fiber can be achieved by using dispersion compensation fiber (DCF).

Japanese terrestrial digital broadcasting (ISDB-T) began in 2003. To spread its signals throughout the country, optical fibers will be used to complement radio-wave networks. This paper describes recent applications of optical transmission of ISDB-T. It also describes our research on re-transmission with 40-GHz Radio On Fiber technology.

The hybrid fiber coax (HFC) technology enables the conventional cable-television (CATV) network to provide subscribers with Internet access services. In this paper, we propose a new preemptive priority scheme (PPS) for IEEE 802.14 hybrid fiber coax (HFC) networks with the intelligent nodes (INs). The INs are placed between the headend controller and stations. By using INs, that stand for downstream subscribers to contend for the demand resources, the collision probability, and the collision resolving period can be reduced. In this paper, we further extend such network architecture to support multi-priority access. In each IN or individual station, the proposed PPS will prevent a higher priority request from colliding with requests of lower priority. Moreover, in PPS, the granted bandwidth for lower priority requests can be preempted by the waiting request with higher priority. This will speedup the channel capture by priority data. The efficiency of PPS is investigated by simulations. Simulation results show that by adopting INs with PPS to be an agent for subscribers can not only shorten the collision resolving period but also minimize the average request delay of priority data.

The poor capability of bandwidth management on the current CATV network hinders the promotion of multi-media streaming services. This paper proposes a solution by applying stream-code partition on the S-CDMA system adopted in the DOCSIS 2.0 standard. The method makes use of the Fine Granularity Scalability source coding and offers an efficient way for uplink rate control, so that bandwidth management can be performed in an extremely flexible manner.

As an access network to the Internet, CATV/HFC network has been widespread recently. Such a network employs a reservation access method under which reservation and data transmission periods appear by turns. Before data transmission, a station must send a request in a random access manner during the reservation period called a request cluster. If the cluster size is large, the probability of request collision occurrence becomes small. A large cluster size however increases the packet transmission delay. Moreover the throughput decreases since vacant duration of reservation period increases. DOCSIS, a de facto standard for the networks, employs the binary back-off method for request cluster allocation. Since that method normally allocates unnecessary large request cluster, the transmission delay increases under heavy load conditions. In this paper, we propose a request cluster allocation method which dynamically changes the cluster size according to the load conditions. In order to evaluate performance of the proposed method, we build a queuing model and execute computer simulation. Simulation result shows that the proposed method provides smaller delay than the binary back-off method.

CATV networks are considered as promising transmission channels in that they permit wide bandwidth and high quality data communications. In apartment houses, however, the ingress noise in the up-links due to the tree and branch structure of a network deeply degrades the transmission performance of data communication channels. This is a serious problem especially in apartment houses which are often equipped with old coaxial cables. It permits the noise generated from electrical appliances to disturb up-link data communications. In this paper, we propose a wireless CATV system. In the proposed system, the noise generated in the room of a subscriber does not intrude into a trunk line. We analyze the upstream channels of this system. Based on the results of numerical analyses, we found that the proposed system is suitable and practical for up-link operation in CATV networks for apartment houses.

We study the quality of the terrestrial digital video broadcasting (DVB-T) transmission over the cable TV network. Generally, when terrestrial digital TV signals are distributed in the cable TV, a conversion is needed in the head-end, from DVB-T (OFDM) to DVB-C (single carrier). In order to avoid this costly conversion and to transmit DVB-T signal directly in the existent cable channel, many requirements have to be satisfied. It is known that phase noise represents the main limitation for OFDM based systems. In this contribution we demonstrate the sensitivity of the OFDM system for the phase noise effects by using a dynamic model for CATV channel. Then, we conclude by giving the specifications that a converter in the CATV network should have to still allow the functionality of the DVB-T system.

This work presents a frame-structure, referred to as CATM (CATV ATM), to serve as a wireless network infrastructure. The widespread CATV (Community Antenna TV) networks are attractive infrastructures for next generation wireless networks. Providing interactive broadband services over CATV networks is a major trend in communication and ATM (Asynchronous Transfer Mode) networks with broadband communication features well fitted to be the backbone of CATV networks. Based on the proposed network architecture, this work addresses and investigates the problems of call setup and handoff handling. This work also proposes a wireless signaling protocol for establishing mobile connections over the CATM-based wireless networks. To enhance bandwidth utilization, the proposed scheme attempts to keep the path resulting after handoff as short as possible. The protocol also evolves a seamless handoff scheme (denoted as SHSW-CATM), that can preserve data continuity, is transparent to other mobile terminals, and produces a shorter path. Analytical results reveal that the SHSW-CATM has a high probability of obtaining an optimal path (that is, a non-elongated path) following mobility.

This paper proposes the technology of wide passband wavelength-division multiplexing (WWDM) for access networks offering multiplexed services. The technology greatly relaxes the wavelength setting accuracy requirements of the WDM light source and the multiplexer/demultiplexer (MUX/DEMUX) compared to dense WDM (DWDM) technology. A WWDM optical converter that offers the Internet protocol (IP) service is implemented and its performance assessed at temperatures ranging from 0C to 45C. In addition, we assess three channel transmission (cable television (CATV) and IP services) in the 1.5 µm region as a multiplexed service example. Using the proposed WWDM, we confirm the feasibility of a service multiplexing system that offers simultaneous CATV and IP services in access networks. This WWDM technology is expected to provide cost effective service multiplexing systems for access networks.

The cable TV (CATV) network is an ideal backbone for PCS due to its prevalent and broadcast nature. This significantly reduces the implementation costs and the handoff overheads. This paper proposes two architectures for the CATV-based PCS system. In the first architecture, each base station is equipped with multiple fixed receivers to provide fast and seamless handoffs for mobile users. Nevertheless, the hardware cost for this implementation is relative expensive. To overcome this, in the second architecture, each base station is equipped with only one tunable receiver. This simple and economic architecture suffers from the possibility of offset conflict when mobile terminals handoff between cells. Three offset assignment algorithms based on the concepts of random assignment, neighbor usage, and clustering, respectively are proposed to solve the offset conflict problem. Simulation results indicate the one with the concept of clustering performs much better than the other two schemes in terms of offset conflict probability.

The project of interconnecting CATV in Hyogo Prefecture, Japan has started since March, 1998. In this project, there are three CATV companies in Hanshin area; Kobe, Nishinomiya and Amagasaki. An ATM switch is equipped in each company and these CATVs are connected serially in the above order. Each company provides the video service to the rest of companies using the MPEG2 over ATM. Each MPEG2 stream is sent to the other two CATV companies according to the function of multicast implemented in ATM switch. In the coverage of each CATV, subscribers utilize Internet connection using cable modems as well as standard CATV broadcasting service. In this paper, we present the outline of the research project in Hyogo Prefecture, Japan, and examine the jitter processes of MPEG streams of the testbed network by the simulation. In our testbed network, cells with two types of requirement for QoS are multiplexed; cells for MPEG2 which require the real-time transmission and those for Internet packets which are much more sensitive for the cell loss ratio. We investigate the jitter processes under some scenarios and show how the jitter process is affected by the Internet traffic and the other cell streams of MPEG2. Furthermore, we study the effect of the number of ATM switches on the jitter process when more CATV networks are added serially.

For Cable-To-The-Air network providing a seamless access network in both indoor and outdoor, direct optical switching CDMA scheme is newly proposed to multiplex any types of radio signals. In two types of connection methods, optical switch connection and optical coupler connection systems, the received carrier-to-interference-plus-noise power ratios are theoretically analyzed. It is clarified that in the optical switch connection connection system, by introducing the additional optical gain at each radio base station, the carrier-to-interference-plus-noise power ratios for all radio base stations and the connected number of radio base stations can be improved compared with the OC connection system.

A CATV network which has a switched double star configuration, fiber to the home (FTTH) and full digital transmission has been tested to see the feasibility with one Head-End (HE), one Central Office (CO), one Distribution Center (DC), and 25 subscribers. Also POTS and NISDN services have been provided to 5 subscribers. Single mode optical fibers are fully deployed from a HE to subscribers. A PON with TDM/polling scheme has been implemented considering the economic issue. Also in the outside plant, we tried to use the existing facility including the in-house duct. This paper deals with the results of the trial and some issues on the operational view.