The transmission S-parameter between two dipole-elements is a measure to evaluate sites for measuring complex antenna factors (CAF). In this paper, the S-parameter between two dipole-elements on a ground plane is measured using a network analyzer with its TRL (Thru-Reflect-Line) calibration. The S-parameter is also calculated by the method of moment (MoM) and compared to the measurement results. The comparison shows that the calculated S-parameter is usable as a reference value in the evaluation of CAF measurement sites. As an example of the evaluation and selection of measurement sites, the transmission S-parameter on a finite ground plane is calculated using the hybrid method combined the geometrical theory of diffraction (GTD) and MoM. As a result, a preferable antenna setting on the finite ground plane is recommended.

A rack-mounted prototype packet switch that makes use of wavelength-division-multiplexing (WDM) interconnect techniques has been developed. The switch has a maximum throughput of 320 Gbit/s. It features a WDM star-based switch architecture, an electrical control circuit layer and a broad-bandwidth optical WDM layer. The basic characteristics of the broad bandwidth WDM layer, such as level diagram, transmission characteristics, 32-wavelength-channel switching, and high-speed optical gating within a 1.6-ns guard time, are described. Experimental results demonstrated that the switch can perform practical self-routing switch operations, such as address-extraction, optical buffering, and filtering for packet speeds of up to 10 Gbit/s. The switch is promising for such applications as a terabit-per-second switching node in future WDM transport networks.

In this paper, we discuss on the realization of reduced peak power transmission for the multicarrier systems. Since the signals have large amplitude fluctuations in conventional multicarrier systems, signals amplified by a nonlinear amplifier are greatly distorted, resulting in severe performance degradation. In order to avoid this large amplitude fluctuation, we propose a scheme for reducing the nonlinear distortion by using the set of the signal point series which show low peak to mean envelope power ratio (PMEPR) value. In this system, one symbol is transmitted with multicarriers and the received signal is detected with maximum likelihood sequence detection.

We present a design method of the simulation probability density function for a trellis-coded modulation (TCM) in an impulsive noise environment. The upper bound evaluation method for the TCM scheme cannot be applied to the lognormally distributed impulsive noise, since the Chernoff bound cannot be defined. Thus the error probability can only be estimated by a computer simulation. For an evaluation of a low error probability, importance sampling (IS) is an efficient technique. A design method of the simulation probability density function, which plays an important role in IS, is proposed for the noise. The effectivity is shown by a numerical example.

This paper investigates noise enhancement factors of a zero-forcing detector and a decision feedback detector for synchronous Multiple Input Multiple Output (MIMO) channels. It is first shown that the zero-forcing and decision feedback detectors can be implemented in a vector digital filter form, and the noise enhancement factors with the detectors can easily be calculated by using the vector digital filter form. This paper then applies the zero-forcing and decision feedback detectors to the signal detection of a frequency-overlapped multicarrier signaling (FOMS) system. The normalized noise enhancement factor, which is given as a product of the noise enhancement and bandwidth reduction factors, is shown to be smaller with the decision feedback detector than the zero-forcing detector. Results of computer simulations conducted to evaluate bit error rate (BER) performances with the two detectors are also shown together with the BER performance with a conventional channel-by-channel detector.

For binary linear block codes, we introduce "multiple GMD decoding algorithm. " In this algorithm, GMD-like decoding is iterated around a few appropriately selected search centers. The original GMD decoding by Forney is a GMD-like decoding around the hard-decision sequence. Compared with the original GMD decoding, this decoding algorithm provides better error performance with moderate increment of iteration numbers. To reduce the number of iterations, we derive new effective sufficient conditions on the optimality of decoded codewords.

With a view to virtual studio applications, we design an optimal grid pattern such that the observed image of a small portion of it can be matched to its corresponding position in the pattern easily. The grid shape is so determined that the cross ratio of adjacent intervals is different everywhere. The cross ratios are generated by an optimal Markov process that maximizes the accuracy of matching. We test our camera calibration system using the resulting grid pattern in a realistic setting and show that the performance is greatly improved by applying techniques derived from the designed properties of the pattern.

Multi-user uniquely decodable (UD) k-ary coding for the multiple-access adder channel is investigated. It is shown that a Tf+g+1-user UD k-ary affine code with code length f+g+1 can be obtained from two Tf-user and Tg-user UD k-ary affine codes. This leads to construct recursively a Tn-user UD k-ary affine code with arbitrary code length n. The total rate of the code tends to be higher than those of all the multi-user UD k-ary codes reported previously as the number of users increases.

We are interesting in the error exponent for source coding with fidelity criterion. For each fixed distortion level Δ, the maximum attainable error exponent at rate R, as a function of R, is called the reliability function. The minimum rate achieving the given error exponent is called the minimum achievable rate. For memoryless sources with finite alphabet, Marton (1974) gave an expression of the reliability function. The aim of the paper is to derive formulas for the reliability function and the minimum achievable rate for memoryless Gaussian sources.

In this paper, we propose a call arrival history-based location tracking strategy for a variable call arrival rate over time. The basis of the proposed strategy is a time-based location tracking strategy. A mobile terminal obtains the up-to-date information about changes in the call arrival rate by maintaining its call arrival history, from which it can calculate an appropriate timeout interval for a variable call arrival rate. We present a simple analytical model and numerical results to investigate its performance for both a fixed and a variable call arrival rate which is modeled by a Markov-modulated Poisson process.

Session length and group size are two most significant factors in achieving efficient scheduling for unicast and multicast traffic in single-hop wavelength division multiplexing (WDM) local area networks (LANs). This paper presents a hybrid protocol to schedule both unicast and multicast traffic in broadcast WDM networks. The protocol makes an important assumption that unicast traffic is the major portion of the overall traffic and is usually scheduled with a pre-allocation-based protocol. On the other hand, multicast traffic is a smaller portion of the overall traffic with multicast sessions and multicast groups, and is scheduled with a reservation-based protocol. The concept of multicast threshold, a function of random variables including the multicast session length and the multicast group size, is also proposed to partition the multicast traffic into two types. If the transmission threshold of a multicast request is larger than the multicast threshold, the request is handled with a reservation-based protocol. Otherwise, the multicast request is handled similar to unicast traffic; that is, each packet in the multicast session is replicated and sent to the unicast queues of destinations. The results show that the hybrid protocol can achieve better channel utilization efficiency and packet delay for unicast traffic under the multicast scenarios with moderate session length and group size. However, separate scheduling or broadcasting will be more suitable for a multicast scenario with very large session length and group size, which is not common on most realistic networks.

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.

An optical spectral coding scheme is devised for fiber-optic code-division multiple-access (FO-CDMA) networks. The spectral coding is based on the pseudo-orthogonality of FO-CDMA codes properly written in the fiber Bragg grating (FBG) devices. For an incoming broadband optical signal having spectral components equal to the designed Bragg wavelengths of the FBG, the spectral components will be reflected and spectrally coded with the written FO-CDMA address codes. Each spectral chip has different central wavelength and is distributed over the spectrum of the incoming light source. Maximal-length sequence codes (m-sequence codes) are chosen as the signature or address codes to exemplify the coding and correlation processes in the FO-CDMA system. By assigning the N cycle shifts of a single m-sequence code to N users, we get an FO-CDMA network that can theoretically support N simultaneous users. To overcome the limiting factor of multiple-access interference (MAI) on the performance of the FO-CDMA network, an FBG decoder is configured on the basis of orthogonal correlation functions of the adopted pseudo-orthogonal codes. An intended receiver user that operates on the defined orthogonal correlation functions will reject any interfering user and obtain quasi-orthogonality between the FO-CDMA users in the network. Practical limiting issues on networking performance, such as non-flattened source spectra, optical path delay, and asynchronous data accesses, are evaluated in terms of the bit-error-rate versus the number of active users. As expected, the bit-error-rate will increase with the number of active users. Increasing the flatness parameter of optical signal will lead to a lower average error probability, since we are working in a part of the more flattened optical spectrum. In contrast, reducing the encoded bandwidth will reduce the total received power, and this will necessitate higher resolution of fiber Bragg gratings.

IOG is a link layer protocol specifically designed for the high speed and bandwidth efficient transmission of IPv4 and IPv6 datagrams over optical fibers. That is, IOG is a simple point-to-point packetization protocol over a bit stream with a low bit error rate. MTU of IOG is 1535, which is long enough for the Internet with IPv6 multicast packets and Ethernet frames. IOG has a framing structure of fixed length (2048 bytes) for synchronization, CRCC (Cyclic Redundancy Check Code) and scrambling. A frame consists of 4 bytes of a frame header, 2040 bytes of a frame payload and 4 bytes of a frame trailer for CRCC. CRCC is also used for scrambling. A frame header consists of a 21 bit flag sequence ("011111111111111111110") and a 11 bit packet boundary pointer. A packet has an 11 bit length field and a 21 bit label field. The label field contains an Ethertype or a link layer label. Packets are packed continuously in frame payload. A packet is at least 20 and at most 1535 bytes long. If there are no packets to send, 20 byte packets of Ethertype 0 are sent, which is ignored by the receiver. A packet may be included in two adjacent frames. The packet boundary pointer in a frame header of a frame points to the first packet boundary of the frame, which means that once a frame synchronization is established, packet synchronization is also established. IOG is designed to allow high-speed implementations to enable 32 or 64 bit parallel processing. CRC polynomial of X32 + X2 + X + 1 is newly designed for high-speed 32 or 64 bit parallel calculation and frame wise SECDED (Single Error Correction, Double Error Detection). IOG is applicable to long haul transmission of IP datagrams in Internet backbone and to inter-chip or inter-module transmission of IP datagrams in parallel IP routers.

The need for greater transmission capacity through optical fiber has been met so far by the wide scale deployment of wavelength division multiplexing (WDM). Still, to manage and access this bandwidth, the next growth challenge will most likely emerge at the switching nodes, where processing is needed to groom the ever diverse and changing traffic. The eventual goal is to reduce the amount of complex electronics, and thus, the cost, by migrating to the all-optical network, where data is switched and routed transparently in optical form, with a minimum amount of electronic processing. As a first step in this direction, optical cross-connects (OXCs) and optical add-drop multiplexers (OADMs) are already being introduced commercially to perform basic routing and switching functions for protection and allocation. Eventually, we envision an optical packet switched network layer that features: (i) bit rate transparency, (ii) protocol transparency, and (iii) fast switching with fine granularity. With these characteristics, an optical packet switched network layer can be a high performance and cost competitive solution for future networks. Several networking functions will be needed to deploy the all-optical transparent layer. Wavelength conversion will allow the reuse of wavelengths in the network and may help alleviate contentions. Optical synchronization and optical packet header processing (for routing and switching) will increase throughput and reduce latency. Last, but not least, all the above solutions will need to be bit rate and modulation format independent (or at least be able to handle a wide range of bit rates and modulation formats).

In this paper, we propose path accommodation methods for unidirectional rings based on an optical compression time-division multiplexing (OCTDM) technology. We first derive a theoretical lower bound on the numbers of slots and frames, in order to allocate all paths among nodes. Three path accommodation algorithms for the all-optical access are next proposed to achieve the lower bound as closely as possible. Path splitting is next considered to improve the traffic accommodation. Finally, we analyze the packet delay time for given numbers of slots/frames, which are decided by our proposed algorithms. Numerical examples are also shown to examine the effectiveness of our proposed algorithms including path accommodation and path splitting methods.

In this paper, we consider the design for testability of a multiplier based on the modified Booth Algorithm. First, we present a basic array implementation of the multiplier. Next, we introduce testability considerations to derive two C-testable designs. The first of the designs is C-testable under the single stuck-at fault model (SAF) with 10 test patterns. And, the second is C-testable under the cell fault model (CFM) with 33 test patterns.

We analyze the performance of soft handoff used as intergroup handoff in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity.

This paper describes a novel IDDQ sensor circuit that is driven by only an abnormal IDDQ. The sensor circuit has relatively high sensitivity and can operate at a low supply voltage. Based on a very simple idea, it requires two additional power supplies. It can operate at either 5-V or 3.3-V VDD with the same design. Simulation results show that it can detect a 16-µA abnormal IDDQ at 3.3-V VDD. This sensor circuit causes a smaller voltage drop and smaller performance penalty in the circuit under test than other ones.

The non-collision packet reservation multiple access (NC-PRMA) protocol has been proposed for wireless voice communications. In that protocol, although it can avoid any collision by using control minislot, the terminal which generates its talkspurt in a current frame has to wait till a next frame to transmit an asking packet to obtain reservation. Furthermore, under integrated voice and data traffic, in the conventional NC-PRMA the voice packet dropping probability becomes worse, because of the number of slots that voice terminals can access are limited. In this paper, we propose the NC-PRMA with random transmission to idle slots. First, we evaluate the mean access delay and the voice packet dropping probability under only voice traffic by the theoretical analysis and the computer simulation. It is shown that the proposed scheme attains lower mean access delay than the conventional NC-PRMA. Next, we evaluate the data packet delay and the voice packet dropping probability under integrated voice and data traffic by the computer simulation. It is shown that the proposed scheme attains lower packet dropping probability than the PRMA and the conventional NC-PRMA.