Sungmin Han

A microelectromechanical system artificial basilar membrane based on a piezoelectric cantilever array and its characterization using an animal model

We proposed a piezoelectric artificial basilar membrane (ABM) composed of a microelectromechanical system cantilever array. The ABM mimics the tonotopy of the cochlea: frequency selectivity and mechanoelectric transduction. The fabricated ABM exhibits a clear tonotopy in an audible frequency range (2.92–12.6 kHz). Also, an animal model was used to verify the characteristics of the ABM as a front end for potential cochlear implant applications. For this, a signal processor was used to convert the piezoelectric output from the ABM to an electrical stimulus for auditory neurons. The electrical stimulus for auditory neurons was delivered through an implanted intra-cochlear electrode array. The amplitude of the electrical stimulus was modulated in the range of 0.15 to 3.5 V with incoming sound pressure levels (SPL) of 70.1 to 94.8 dB SPL. The electrical stimulus was used to elicit an electrically evoked auditory brainstem response (EABR) from deafened guinea pigs. EABRs were successfully measured and their magnitude increased upon application of acoustic stimuli from 75 to 95 dB SPL. The frequency selectivity of the ABM was estimated by measuring the magnitude of EABRs while applying sound pressure at the resonance and off-resonance frequencies of the corresponding cantilever of the selected channel. In this study, we demonstrated a novel piezoelectric ABM and verified its characteristics by measuring EABRs.

High speed CAN transmission scheme supporting data rate of over 100 Mb/s

As the number of electronic components in the car increases, the requirement for the higher data transmission scheme among them is on the sharp rise. The control area network (CAN) has been widely adopted to support the in-car communications needs but the data rate is far below what other schemes such as Ethernet and optical fibers can offer. A new scheme for enhancing the speed of CANs has been proposed, where a carrier modulated signal is introduced on top of the existing CAN signal, whereby the data rate can be enhanced over 100 Mb/s. The proposed scheme is compatible with the existing CAN network and accordingly enables seamless upgrade of the existing network to support high-speed demand using CAN protocol.

Communication channel modeling of controller area network (CAN)

Controller area network (CAN) has been widely used for in-vehicle network. The demand of data rate of invehicle network has risen sharply, while traditional CAN communication cannot support this demand of data rate with limited bandwidth around DC. To overcome the limitation, passband communication systems can be considered where wider bandwidth may be available. In order to use the passband, we need to understand and analyze CAN communication channel. However, since real measurement of the channel response takes so much time and efforts, it will be convenient if channel modeling of CAN communication system is available. In this paper, we perform modeling of passband CAN communication systems in case of end-to-end topology by using transmission matrix and cascade of two port network methods. Instead of real measurement, we expect to reduce the time and efforts significantly to obtain a passband CAN communication channel response by using the channel modeling result. Finally, we suggest the range of frequency band and bridge tap lengths for designing CAN communication systems.

Harnessing self-cancellation for coexistence of Wi-Fi and Bluetooth

In this paper, we present a simple and effective solution for resolving the in-device coexistence problem of Wi-Fi and Bluetooth. The main idea is to introduce a canceller in the circuit in order to cancel out the in-device interference when Wi-Fi and Bluetooth radios simultaneously operate in the same device. Our proposed approach, entitled the hybrid arbitrator, can significantly improve the performance of both of Wi-Fi and Bluetooth. Based on our testbed, we carry out extensive experiments to validate the performance of the proposed scheme. Our results show that the proposed hybrid arbitrator gives substantially better performance than existing methods.

Tactical beamforming against high-power reactive jammer

Beamforming can spatially filter out a jamming signal and effectively obtain the desired directional gain. However, due to side-lobe, blunt beam of main-lobe, fault adaptation, and so forth, a targeted signal can be leaked to a reactive jammer. By sensing the leaked signal power, the reactive jammer concentrates its own power to the frequency band of the targeted signal. To solve this problem, we suggest parallel transmission of the target signal and a decoy signal in addition to conventional joint tx-rx beamforming for anti-jamming. Because the decoy signal uses different frequency band from the target, jammer cannot help distributing its jamming power between these signals. By measuring signal-to-jamming-plus-noise power ratio (SJNR) and channel capacity under the high-performance reactive jammer, we show that the proposed anti-jamming beamforming scheme outperforms the conventional one especially in the presence of high power jamming.

Random access success probability in full-duplex radio networks

It is well known that the full-duplex radio can enhance spectrum efficiency compared with half-duplex radio in inter-node interference free environment. However, in real situation, the inter-node interference is inevitable especially in the random access system whose performance is considerably affected by the interference. In this paper, we analyze the full-duplex system in random access scenario to show that the full-duplex radio can improve random-access throughput performance, e.g., even more than twice in special conditions.

BER analysis of CAN under BPSK passband CAN-HD interference

An increasing demand for processing a large amount of data traffic resulted in the necessity of higher data rate of in-vehicle systems. In this regard, the controller area network for high data rate (CAN-HD) improves the data rate and is also compatible with conventional controller area network (CAN) system. To improve the data rate, the CAN-HD uses more bandwidth and allocates its power to the passband. Additionally, the CAN-HD is compatible with the conventional CAN by using a low-pass filter in a conventional CAN receiver. However, as more power is allocated in the passband, the bit error rate (BER) may increase due to the CAN-HD interference. In order to mitigate such problem, we analyze the performance of standard CAN receiver with high passband power for providing the criterion for proper power allocation for the passband signal.

Channel capacity analysis for high speed controller area network (CAN)

Controller area network (CAN) is an in-vehicle communication network system. Many microcontrollers are built in vehicles that transmit and receive the data through CAN bus. As more microcontrollers are built in the car, the amount of data to be processed are increased. However, it is insufficient to process the increasing data because the maximum data rate of the standard CAN is 1Mbps. Therefore, we recently proposed a high data rate CAN system which combines the standard baseband CAN signal with a passband modulated signal. Before designing this system, the channel capacity analysis is needed to estimate the performance of the proposed scheme. This paper introduces the channel capacity analysis of the proposed scheme. In order to get the signal to noise power ratio (SNR) that is needed for capacity analysis, the standard baseband CAN noise is measured in a real car. Based on the SNR, water-filling algorithm is then employed for power allocation in the frequency domain, resulting in the channel capacity.

Analysis of D2D system performance with a maximal SINR channel selection strategy.

In this paper, we investigate the throughput of device to device (D2D) communication which utilizes maximal signal to noise and interference power ratio (SINR) channel selection strategy when it shares on frequency band with a cellular system. The throughput is affected by both the total number of available channels and number of used channels which is proven by numerical simulation. The results of this paper will give us an intuition about D2D device channel planning.