The influence of pump phase error on phase-sensitive optical amplifier (PSA) repeaters and the waveform degradation due to chromatic dispersion and fiber nonlinearities in the optical multi-relay transmission of quadrature phase-shift keying phase-conjugated twin waves are considered theoretically. First, the influence of noise from the pump phase error, optical local oscillator, receiver, and the amplified spontaneous-emission (ASE) in PSA repeaters is investigated with the assumption that transmission fibers are linear lossy channels. The bit-error rate (BER) is estimated as a function of the signal-to-noise ratio, and the relationship between the number of transmission relays and the fiber launch power is clarified. Waveform degradation due to chromatic dispersion and the optical fiber nonlinearities in transmission fibers are investigated with the noiseless condition, and the maximum repeatable number as a function of the fiber launch power is calculated. Finally, we show the relationship among the maximum repeatable number, standard deviation of pump phase error in PSA repeaters, and the fiber launch power to clarify the optimum transmission condition with consideration of the noise and the waveform degradation.

To drastically increase the splitting ratio of extended-reach (40km span) time- and wavelength-division multiplexed passive optical networks (WDM/TDM-PONs), we modify the gain control scheme of our automatic gain controlled semiconductor optical amplifiers (AGC-SOAs) that were developed to support upstream transmission in long-reach systems. While the original AGC-SOAs are located outside the central office (CO) as repeaters, the new AGC-SOAs are located inside the CO and connected to each branch of an optical splitter in the CO. This arrangement has the potential to greatly reduce the costs of CO-sited equipment as they are shared by many more users if the new gain control scheme works properly even when the input optical powers are low. We develop a prototype and experimentally confirm its effectiveness in increasing the splitting ratio of extended-reach systems to 512.

The authors propose “Disk-repeater” as a new structure alternative to the conventional resonator repeater. Disk-repeater has a simple structure comprised of just copper plates and wire, non-resonant structure. First, coupling coefficients are measured as functions of disk diameter and wire length to characterize the basic performance of Disk-repeater. It is explained by several experimental evidences that Disk-repeater and resonator are not magnetically coupled but electrically coupled. It is also shown that the transmission distance extends dramatically longer than that of conventional resonator repeater. Further, two-dimensional arrangement, where multiple disks are connected, shows very high efficiency and uniform transmission characteristic regardless of positions of receiving resonator. Disk-repeater gives possibility of unprecedented versatile application with the simple structure.

An on-channel repeater (OCR) performing simultaneous reception and transmission at the same frequency is beneficial to improve spectral efficiency and coverage. In an OCR, it is important to cancel the feedback interference caused by imperfect isolation between the transmit and receive antennas, and least mean square (LMS) based adaptive filters are commonly used for this purpose. In this paper, we analyze the performance of the LMS based adaptive feedback canceller in terms of its transient behavior and the steady-state mean square error (MSE). Through a theoretical analysis, we derive iterative equations to compute transient MSEs and provide a procedure to simply evaluate steady-state MSEs for the adaptive feedback canceller. Simulation results performed to verify the theoretical MSEs show good agreement between the proposed theoretical analysis and the empirical results.

We focus on a characteristic which is specific to the quantum repeater protocol. In the quantum repeater protocol, quantum states which are generated by the protocol do not depend on receivers. Therefore, we can reuse EPR pairs which are generated before a change of a receiver for the quantum repeater protocol after the change. The purpose of reusing is advancing the finishing time of sharing EPR pairs, which is not equal to increasing the fidelity. In this paper, we construct concrete methods of reusing EPR pairs and analyze the effectiveness of reusing EPR pairs. Besides, we derive conditions in which reusing EPR pairs is effective.

This paper proposes a new spectrum sharing scheme which uses one-sided collaboration. In the proposed system, the transmitter of the secondary system relays the primary signal and overlays its own data on the retransmitted primary signal. The results of the theoretical analysis show that the proposed scheme with regenerative relay allows the secondary system to communicate at the same speed as the primary system that disregards the presence of the secondary system.

This paper presents a model to estimate jitter insertion and accumulation in clock repeaters. We propose expressions to estimate, with low computational effort, both static and dynamic clock jitter insertion in repeaters with different sizes, interconnects and slew-rates. It requires only the pre-characterization of a reference repeater, which can be accomplished with a small number of simulations or measurements. Furthermore, we propose expressions for dynamic jitter accumulation that considers the dual nature of power and ground noise impact on delay. The complete model can be used to replace time-consuming transient noise simulations when evaluating jitter in clock distribution systems, and provide valuable insights regarding the impact of design parameters on jitter. Presented results show that our models can estimate jitter insertion and accumulation with an error within 10% of simulation results, for typical designs, and accurately reflect the impact of changing design parameters.

This paper evaluates the impact of Through-Silicon Via (TSV) on the performance and power consumption of 3D circuitry. The physical and electrical model of TSV which considers the coupling effects with adjacent TSVs is exploited in our investigation. Simulation results show that the overall performance of 3D IC infused with TSV can be improved noticeably. The frequency of the ring oscillator in 4-tier stacking layout soars up to two times compared with one in 2D planar. Furthermore, TSV process variations are examined by Monte Carlo simulations to figure out the geometrical factor having more impact in manufacturing. An in-depth research on repeater associated with TSV offers a metric to compute the optimization of 3D systems integration in terms of performance and energy dissipation. By such optimization metric with 45 nm MOSFET used in our circuit layout, it is found that the optimal number of tiers in both performance and power consumption approaches 4 since the substantial TSV-TSV coupling effect in the worst case of interference is expected in 3D IC.

Multiple-input multiple-output (MIMO) repeater systems have been discussed in several published papers. When a repeater has only one antenna element, the propagation environment is called keyhole. In this kind of scenario the achievable channel capacity and link quality are decreased. Another limit is when the number of the antenna elements of a repeater is larger than that of a MIMO transceiver, the channel capacity cannot be increased. In this paper, in order to obtain an upper bound of the channel capacity, we express a propagation process of the distributed MIMO repeater system with amplify-and-forward method by the numerical formular, and optimize the position of each repeater.

We present a 60-GHz wireless through-repeater system based on self-heterodyne transmission scheme with the potential to optimize the carrier-to-interference and noise ratio (CINR) performance according to the transmission distance. The phase-noise degradation through a 60-GHz repeater link is not a serious concern when we employ the self-heterodyne transmission scheme. Multichannel interferences caused by third-order intermodulation distortions are efficiently suppressed by setting a high power ratio of LO carrier to RF signals in the self-heterodyne transmission. However, this high power ratio results in a lower carrier-to-noise ratio (CNR) and becomes unsuitable for improving link performance if the transmission distance increases. In order to facilitate a solution, we propose and make an embodiment of 60 GHz self-heterodyne transmitters that provide flexible control over the power ratio of LO to RF in a range of 10 dB ranges. With them, we successfully demonstrate terrestrial digital broadcasting signals on five channels and optimize their performance for wireless through-repeater applications.

In this paper, an indoor repeater antenna with high isolation for WCDMA application is proposed. The designed repeater has very small separation of 20 mm between the donor and server antennas. The antenna has two resonance frequencies to cover the WCDMA band from 1.92 GHz to 2.17 GHz. The fabricated antenna has VSWR below 1.5, gain over 8 dBi, and isolation between server and donor antennas less than -80 dB in the WCDMA band.

An interference cancellation (ICAN) scheme for mobile communication radio repeaters is presented. When a radio repeater has a gain that is larger than the isolation between its transmit and receive antennas, it oscillates due to feedback interference signals. To prevent feedback oscillation of a radio repeater, we first formulate a feedback oscillation model of the radio repeater and then derive an ICAN model from that model. From the derived ICAN model, we show that the stability and the signal quality of the repeater depend on the repeater's gain and delay, the propagation delay on feedback paths, feedback channel characteristics, and the capability of the feedback channel estimation algorithm. It is also shown that the stability condition of the repeater does not guarantee the quality of the repeater's output signal. To guarantee repeater's stability and signal quality, an ICAN scheme based on an iterative algorithm is subsequently proposed. The simulation results confirm the relationship between the stability and signal quality of the repeater and the impact of the aforementioned factors. Using the proposed ICAN scheme, a mean error vector magnitude (quality indicator) of about 6.3% for the repeater's output signal was achieved.

In this letter, the influence of the downlink average ratio of the other cell interference to other-user interference in the serving cell (DARI) on the distributed repeater system (DRS) performance is analyzed. It is found that the improvement of DARI depends on a propagation path loss environment. Applying the computed DARI to a 3-RS DRS cell, as high as 13.9% capacity enhancement was obtained when the path loss exponent is 4.5. In addition, by using the power allocation equation, it is expected that a hexagonal DRS cell without coverage holes or excessive coverage overlap can be realized.

MIMO leads to dramatic improvement in channel capacity and/or link reliability of wireless systems. However, a MIMO channel has only one degree of freedom in a keyhole environment. As a result, this environment reduces achievable channel capacity and link quality. This paper proposes a MIMO repeater system, which can realize a multi-stream transmission. Although the averaged channel capacity in the MIMO repeater system is discussed in several published papers, the probability density functions of eigenvalues of correlation matrix are not analyzed. MIMO transmission performance can basically be estimated from eigenvalues of the channel correlation matrix. We derive an approximated formula for the probability density function of all eigenvalues linked to the space diversity. It is shown that the calculated values based on the proposed method agrees very well with the simulated values.

The transmit power of Ultra Wideband (UWB) is limited in short range communications to avoid the interference with existing narrow-band communication systems. Since this limits UWB communication range, this paper proposes a novel relay scheme that uses shared frequency repeaters for impulse UWB signal relay to improve system range. After considering possible problems with the repeater, in particular the coupling interference between the input and output and relay-delay, a switching control method is proposed that offers short relay-delay and suppresses the coupling interference at the repeaters. With respect to the proposed relay scheme, Pulse-Position-Modulation (PPM) UWB-based signal relay is evaluated by analyzing its BER performance using the point-to-point transmission link model.

This paper describes a newly developed automatic direction control scheme for bi-directional bus repeaters that uses dynamic collaborative driving techniques. Repeater directions are rapidly determined by detecting the direction of control signal propagation through an additional control signal line that is driven by dynamic collaborative drivers. Application to an on-chip peripheral bus reduces control circuit transistor counts by about 75% and the number of control signal lines by about 50% without loss of speed. Experimental results for a 0.18-µm CMOS implementation indicate that the proposed scheme is four times faster than a conventional scheme with no bi-directional bus repeaters.

To avoid over-engineered and expensive systems, it is important that the design takes account of variations in optical fiber characteristics due to the presence of many fiber pieces and splices in optical fiber networks. We present a design method for optical fiber networks that employ distributed Raman amplification (DRA), that considers variations in both optical losses at signal and pump wavelengths, Raman gain characteristics and splice losses. Our method can be applied to the design of both newly developed systems and installed systems. We show design examples based on our method and reveal the practicability of our method.

This paper describes the choke-loaded patch array antenna for use in the IMT-2000 repeater systems. The choke structure of the 4-element array is designed by means of an electromagnetic analysis. A high front-to-back (FB) ratio is required for suppressing mutual coupling in order to stop the oscillation caused by the interference waves between a transmitting and receiving antenna. The suppression of the FB ratio by a choke is limited in the case of the 16-element array because its side lobe level is large. In this paper, we examine the effect of suppressing the mutual coupling using a binomial array.

In a wireless home network, shadowing is frequently caused by human bodies or furniture. Therefore, relay transmission function is considered for the hub station in Wireless Homelink when the direct communication of terminals is obstructed. However, in relaying high rate isochronous data such as video streams, the bandwidth resource of Wireless Homelink may be crammed with those data. In this paper, we propose an efficient relay scheme--"Pipeline Repeater" for Wireless Homelink. The proposed scheme spatially multiplexes the relay transfer of the isochronous data using antenna directivity. The Pipeline Repeater can relay the isochronous packets as an efficient use of the limited frequency band, and it can be achieved to repeat the high rate data with delay of only one frame. To verify the proposed scheme, we conduct measurements in some actual home environments, and perform the numerical analyses and computer simulations based on the measurements. Our results confirm the efficiency of the Pipeline Repeater scheme.

This paper proposes a radio repeater, cell enhancer (CE), that targets 5-GHz broadband wireless access systems to improve the coverage probability without the need to establish a new access point (AP). The CE adopts a non-regenerative repeating scheme to transfer signals and implements two novel approaches, timing control and gain control, to apply to the target systems. By monitoring the control signals broadcast from the AP, the CE behaves as an AP using the same frame timing and transmitting power level, but using a second frequency channel. Thus, the CE can extend the coverage area of one AP. It appears that, however, in the orthogonal frequency division multiplexing (OFDM) system, over two hops with non-regenerative repeating, the additive effect of multipath fading from the two paths results in more violent subcarrier fluctuations and increased delay spread. Computer simulations in multipath fading environments derive the required CNR values for each path, which are required when the CE is installed in the field. In addition, we clarify that multiple CEs can use the same second frequency and provide better coverage with useful macro diversity gain in 5-GHz indoor environments.