Field-programmable gate array (FPGA) is a preferred solution for a CMOS image sensor (CIS) automatic test equipment (ATE) because it provides fast upgradability for the timely testing of CIS products using a new interface protocol. However, implementing a Mobile Industry Processor Interface (MIPI) C-PHY receiver to receive images from the CIS in an FPGA can be challenging due to the use of three wires, three distinct voltage levels, and the requirements of fast clock data recovery (CDR) lock time and wide CDR tracking bandwidth. To overcome these challenges, we have developed an FPGA-only MIPI C-PHY receiver that utilizes a blind oversampling CDR technique, which offers fast CDR lock time and wide CDR bandwidth. We used an Altera Stratix 10 GX FPGA as an oversampling device by operating its transceiver in a lock-to-reference-clock mode. We developed a parallel gate-based clock recovery algorithm and a fork and join-based data decision algorithm. As a result, we were able to test CIS wafers at symbol rates of up to 3.5 Giga-symbols per second, achieving performance comparable to that of sophisticated ASIC-based CIS ATEs.

Evaluating the clock quality of a device's phase-locked loop (PLL) using automatic test equipment (ATE) at an affordable cost is challenging due to the large number of channels and long test times required. This study proposes a new low-cost method for testing the clock jitter of the device using PLL, delay, gate, etc. in the FPGA. Using this circuit, the total jitter analysis function of an expensive, heavy, and slow oscilloscope can be performed simultaneously with tens of CH of clocks within 1us time on a smart phone size board with only tens of dollars of FPGA.

During wafer testing with probe cards in Automatic Test Equipment (ATE), it is challenging to maintain a stable VDD-GND voltage supplied to the Device Under Test (DUT) due to fluctuations in GND voltage caused by the return current from the DUT. Typically, due to a lack of channels, the test equipment reads and corrects the VDD voltage based on the representative GND voltage at an intermediate point where power is supplied, rather than the ground of each DUT. As a result, if there is a change in the GND voltage of each DUT, the test equipment is unable to detect and adjust for it. To overcome these limitations, this study proposes a method of configuring a circuit within the probe card that allows for the use of existing equipment functions such as current measurement and open-short testing while correcting changes in the individual DUT GND voltage of sensitive power sources. This approach aims to minimize wrong defect determination caused by changes in GND voltage during wafer testing.

When measuring the DC drive capability of the DUT's output pin in ATE, the DUT's output voltage is often measured with a termination resistor such as 100 ohms for a differential signal or 50 ohms for a single-ended signal. In this case, as the tester must always be accurate, it is important to create an accurate termination resistance condition. In addition, in some cases, it is desirable to measure the output voltage of the signal pin under different termination conditions. This paper presents a method of correcting an inaccurate termination resistance value or changing a termination resistance value to another value by using the current output function of a parametric measurement unit (PMU) in a tester with only one representative load resistor. In this way, the termination resistance deviation between equipment and CH can be evenly calibrated, and if a test is required under new termination resistance conditions that are not mounted on the tester, the test can be performed only by modifying the software without modifying H/W.

If a transmission line carrying a high-speed signal is damaged, for example by poor contact, the transmitted signal will have a slight increase in jitter. Normally, an oscilloscope or a Vector network analyzer (VNA) is required to measure this jitter increase. In this study, we will show that it is possible to diagnose small losses in transmission lines using only an FPGA without instruments by transmitting a pulse signal through the CH to be diagnosed and then oversampling it in an FPGA to statistically accurately measure the width of the transmitted pulse and detect the small pulse width reduction that occurs when a loss occurs.

As signal transmission loss in automatic test equipment (ATE) is large, receiving a signal without an equalizer is difficult. This study designs a 4.5 Gsps mobile industry processor interface (MIPI) D-PHY analog front-end receiver circuit for ATE. The D-PHY signal uses a DC-coupled low-voltage signal, making the use of commercially available continuous time linear equalizer (CTLE)-included redrivers difficult. We propose a receiving circuit with an equalizer as an off-the-shelf device that can receive D-PHY signals from long distances. The developed receiving circuit achieved optimal signal restoration performance by tuning for the fixed loss characteristics. Additionally, using this receiving circuit, we verified the complete output-signal conversion into an image in a wafer mass production environment.

This paper presents a 3.5Gsps MIPI C-PHY analog front-end receiver circuit for Automatic Test Equipment. This circuit has two features. First, it is made entirely of off-the-shelf components. Second, it has powerful CTLE to compensate for transmission line loss. Since it does not use ASIC, it is possible to add functions at a low cost and in a short time. In the wafer test environment, the loss between the wafer and the receiving circuit is large. This CTLE can be fine-tuned and effectively compensate for the transmission line loss of the developed equipment.

Achieving the benefits of high-capacity of optical networks and the mobility feature of wireless networks leads to integrate EPON and WiMAX for a promising broadband access solution. To efficiently put both benefits together, we propose an integration architecture of EPON-WiMAX based upon a Distributed Antenna (DA) environment, where collaborative Base Stations (BSs) concurrently transmit same wireless downlink signals (specifically for multicast and broadcast services (MBSs)) to Mobile Stations (MSs) in overlapped cell coverage areas. It helps enlarge the region of the available network coverage area by increasing Signal to Interference and Noise Ratio (SINR) in overlapped cell coverage areas through cooperation between Optical Line Terminal (OLT) and Optical Network Unit (ONU)- BS. We also present an cost-efficient cell planning to optimally control the size of overlapped cell coverage areas for the proposed DA-based integration architecture with a case study under a required region of the available network coverage area in consideration of the number of ONU-BSs and the distance between ONU-BSs. Performance evaluation results show that the proposed DA-based integration architecture enhances cost efficiency compared to the Traditional Antenna (TA) (non-DA)-based integration architecture with a similar level of spectral efficiency of MSs.

A Power-Saving Mechanism (PSM) operates with sleep-mode and wake-mode, based on the receipt of requests for transition to each mode. The sleep-mode operation is manipulated by adjusting operating parameters such as the minimum sleep interval (Tmin) and the maximum sleep interval (Tmax). Interestingly, both energy consumption and the response delay of the request for a BS initiation of awakening are reciprocally affected by the relative sizes of these two operating parameters compared to the sleep duration (from the beginning of sleep-mode to that of wake-mode). To resolve this issue, this paper proposes a new PSM, called EPSM, which adaptively and simultaneously controls the operating parameters by efficiently reflecting the sleep duration. Moreover, depending on the current remaining energy state, this mechanism can also increase the available sizes of the operating parameters to be manipulated for achieving more intensive energy conservation. A numerical model is developed with a Markov chain for performance evaluation of the proposed mechanism pertaining to energy consumption and the response delay. The evaluation results substantiate that this mechanism can enhance energy conservation within reasonable response delay compared to the standard mechanism. Moreover, under an insufficient remaining energy state, the EPSM can prolong battery life while enduring an increasing response delay.

The sleep-mode operation in power management helps to increase the life of a mobile station by saving energy consumption while it increases the MAC service data unit (SDU) response delay. Due to the trade-off relationship between these two performance metrics, it is important to determine the suitable values for two operating parameters, the initial sleep interval (Tmin) and the final sleep interval (Tmax), which manipulate the sleep-mode operation in the IEEE 802.16e MAC. To reach a fuller understanding of this problem, this paper first presents the sleep-mode operation. A new power management mechanism based on the knowledge on remaining energy in a mobile subscriber station (MSS) is then proposed. Benefits of this mechanism are to reduce the MAC SDU response delay under sufficient energy and to increase the life of a station under insufficient remaining energy. An analytical model for sleep-mode operation is developed, and the proposed mechanism is validated by computer simulation.

Since channel scanning time in IEEE 802.11 handoff is dominant in total handoff delay time, attention has to be paid to the reduction of channel scanning time for effectively supporting delay sensitive applications such as voice over IP (VoIP). Therefore, this paper proposes a new channel scanning scheme that adaptively adopts full channel scanning before, and first satisfaction first reservation scanning after a required delay time obtained from the application layer. Simulation results substantiate that the proposed scheme can keep the total handoff delay as low as possible compared to the required delay while maintaining acceptable Received Signal Strength (RSS) to a Mobile Host (MH) and thus the Quality of Service (QoS) of the applications can be more guaranteed than the conventional and previous schemes.

Hybrid WDM/TDM-passive optical network (PON) is a modified architecture of the WDM-PON based on gain- saturated reflective semiconductor amplifier (RSOA). In this system, the number of splitting ratios should be limited to four due to remodulation scheme for uplink signals within gain- saturated regime of RSOA. To address this problem, we propose a novel frame format, which doubles splitting ratios by applying shared-time division duplex (TDD) scheme. Moreover, adaptive time window control scheme is designed to find an optimal TDD boundary according to the amount of traffic in each link. Comparing fixed-boundary algorithm, simulation results show that the proposed scheme effectively controls the bandwidth, and thus improves total queueing delay and throughput. In spite of some bandwidth loss when applying this scheme, therefore, it makes no performance degradation to the existing system in asymmetric traffic while increasing the number of capable subscribers.

Performances of differentiated services in the upstream transmission of Ethernet passive optical network (E-PON) are affected by bandwidth reservation algorithm of an optical network unit, since data packets can be transmitted to an optical line termination only during the reserved transmission window. The effects of time-slot reservation on differentiated services are analysed and an adaptive class-based excess bandwidth reservation algorithm, called service quality pre-engagement (SQP), which reserves a time-slot based on the backlog queue and traffic arrival pattern of class is proposed. SQP applies the prediction-based bandwidth reservation to selected forward reservation classes (FRCs) which are determined by the introduced dynamic FRC selection. The proposed short-term service work-based time-slot reservation and long-term adaptive FRC selection optimise time-slot reservation according to traffic load of class. Analytic and simulation results show that this approach improves the performance of differentiated services, especially in terms of system buffer size, light-load penalty and service fairness, while guaranteeing high link utilisation and throughput.

Optical burst switching (OBS) is a promising solution to implement the optical Internet backbone. However, the lack of adequate congestion-control mechanisms may result in high burst loss. Schemes such as fiber delay line (FDL), wavelength conversion, and deflection routing to reduce burst collision are unable to prevent the network congestion effectively. To address this problem, we propose and investigate a global solution, called integrated congestion-control mechanism (ICCM), for OBS networks. ICCM, which combines congestion avoidance with recovery mechanism, restricts the amount of burst flows entering the network according to the feedback information from core routers to edge routers to prevent network congestion. Also, a flow-policing scheme is proposed to intentionally drop the overloaded traffic with a certain probability at a core router to support fairness among flows. Moreover, the transmission rate of each flow is controlled to achieve optimized performance such as maximizing throughput or minimizing loss probability using a two-step rate controller at the edge router. Simulation results show that ICCM effectively eliminates congestion within the network and that, when combined with a flow-policing mechanism, the fairness for competing flows can be supported while maintaining effective network performance.

Optical burst switching (OBS) is an approach to building very high capacity routing switches based on optical data paths and electronic control. Therefore, OBS is considered as a viable solution in the high-speed optical Internet backbone. In this paper, we propose an intra-class contention resolution scheme in optical burst switching networks by the enhanced alternative routing algorithm. The blocking probability of the proposed scheme is significantly reduced as compared with the general OBS while the additional delay due to the alternative path is smaller than 10% of the basic offset time.