Hyun-Seo Oh

5.8 GHz DSRC packet communication system for ITS services

In this paper, we introduce a 5.8 GHz DSRC (dedicated short range communication) packet communication system which has been developed by ETRI. 5.8 GHz DSRC packet communication systems are under deveolpment worldwide and it will be widely applied to ITS (intelligent transportation system) services. We discuss the basic requirements of the DSRC communication system and system design specification to meet the requirements with regard to the physical layer, MAC (media acces control) layer, LLC (logical link layer) layer and application layer. DSRC packet communication systems consist of a micro-processor block, baseband packet modem block and an RF block. The microprocessor block handles MAC and application SW, the baseband packet modem transmits data up to 2.048 Mbps and recovers the received data from the RF block. The RF block has a function for ASK modulation and demodulation. We describe packet frame architecture and packet communication procedures for link setup and normal communication.

4.7pJ/pulse 7th Derivative Gaussian Pulse Generator for Impulse Radio UWB

This paper presents an ultra low-power, low-complexity circuit to generate the monocycle pulse for impulse radio UWB (IR-UWB) applications. A 7th order derivative Gaussian pulse is generated using the edge combination technique plus an extra derivative circuitry. The proposed pulse generator is designed using TSMC 0.18 mum CMOS process. Simulation shows 500 mV of pulse amplitude and 800 ps of the pulse duration. Generated pulse spectrum fully complies with the FCC spectrum mask for out-door applications, especially in the range of 3.1-5.1 GHz. The pulse generator dissipates no static current with only dynamic energy consumption of around 4.7 pJ per pulse from 1.5 V supply.

Vehicular Multi-Hop Broadcasting Protocol for Safety Message Dissemination in VANETs

Most safety-related applications targeting at Vehicular Ad-hoc Networks (VANETs) use Vehicle-to- Vehicle (V2V) broadcast method to disseminate safety- related information to all surrounding vehicles. However, the conventional broadcast schemes have the broadcast storm problem which can lead to unbearable transmission delay and packet loss. In this paper, we present an efficient broadcast scheme referred as Vehicular Multi-hop broadcasting Protocol (VMP) for fast dissemination of safety message within the critical area. The core of the VMP is that it designates multiple reliable forwarders with differentiated forwarding delay, and exploits cooperative forwarding mechanism to help the forwarding when the specified forwarders fail to transmit the alert message. With the realistic simulation studies, the VMP demonstrates better performance than previous contention-based schemes by reducing end-to-end delay and message rebroadcasting ratio while keeping high message reception rate.

Robust noncoherent PN-code acquisition for CDMA communication systems

We are proposing a new noncoherent pseudonoise code acquisition method for code-division multiple-access (CDMA) mobile communication systems. The proposed method employs two digital matched filters, and the code acquisition is based on a double dwell process. Through serial cascading of the dual-matched filters, the proposed code acquisition method does not lose the track of the incoming sequence even after returning from the false alarm state. This unique feature imparts on our design much desired stability. Moreover, the use of two matched filters increases the acquisition speed, which is of prime importance. One important issue in CDMA acquisition is how to determine the threshold values for optimal performance, the measure of optimality being the minimum mean acquisition time. In our performance analysis, we have derived the probability of detection and false alarm as a function of threshold values, then determine the threshold values that achieve the minimum mean acquisition time. Our performance analysis shows that the mean acquisition time is 35 ms at -15 dB input chip signal-to-noise ratio, much faster than the conventional active correlation technique.

RF gain/phase and I/Q imbalance error correction technique for multi-channel array antenna systems

A method of correcting the I/Q imbalance errors and amplitude/phase variations for the multi-channel transceiver has been proposed. It utilizes multi-frequency sinusoidal probe signals to take account of the amplitude/phase variations in the passband of the system. The performance of the proposed multi-channel transceiver calibration scheme is verified by the experiment and simulation. The effect of mutual coupling errors between antenna elements on the beam pattern is also evaluated by simulation.

Challenges of LTE high-speed railway network to coexist with LTE public safety network

As the speed of train trialled by the French National Rail Corporation has reached more than 500 km/h, the secure and continuous connection to the train control system has only grown more important. In this paper, current status and progress of national disaster safety network project and LTE-based integrated wireless network for railway in Korea, firstly, and the major challenges of LTE-R network to coexist with LTE public safety network are addressed in the aspect of the air interface requirements for the essential railway services. In our view, it is the most important thing at present for designing and planning LTE railway network to eliminate - not to mitigate or reduce - the radio interference, especially from the adjacent LTE public safety network to LTE-based wireless train control because they use the same frequency band.

A robust code acquisition architecture for non-coherent systems using dual digital matched filters

In this paper, we are proposing a new noncoherent PN code acquisition method for CDMA mobile communication systems. The proposed method employs two digital matched filters, and the code acquisition is based on a double dwell process. Through serial cascading of the dual matched filters, the proposed code acquisition method keeps track of the incoming sequence, until it eliminates the possibility of false alarms through the verification process. This unique feature imparts to our design much desired stability. Moreover, the use of two matched filters in parallel increases the acquisition speed which is of prime importance in the currently emerging wide-band CDMA technology such as IMT2000. Our performance analysis show that the proposed acquisition technique can achieve code acquisition within 35 ms at -10 dB input chip SNR. This is many times faster than the conventional active correlation technique. In this analysis, we have considered the minimum expected acquisition time as the condition for optimality. At this minimized acquisition time, we have analyzed the threshold values required for optimal performance and have derived the probability of detection and false alarm. The worst case acquisition time for the proposed system is 850 ms and the best case is 21 ms. The probability of false alarm for our system is of the order of 3.7/sup /spl times//10/sup -4/.

HOLOGRAPHIC VIDEO SYSTEM WITH A PULSE LASER

A holographic video system operated by a pulse laser is described. The use of a pulse laser as the light source allows the polygon mirror (or scanners) in the system to be eliminated. At the same time, a single long aperture acousto-optic modulator (AOM) is replaced by 6 small aperture AOMs linearly aligned and a still polygon mirror set is used. The effective aperture length of the 6-AOM-combination is 6 times that of an individual AOM. Since in this system the computer-generated-hologram (CGH) data is divided into 6 equal parts and loaded into the corresponding AOMs independently and synchronously, the loading time of CGH data to an AOM is reduced. This system can display 36,864 (in the horizontal direction)×128 (in the vertical direction) holographic fringe data points in binary format and operate at a rate of 60 frames per second using a personal computer.

Improving the Performance of AODV(-PGB) based on Position-based Routing Repair Algorithm in VANET

Vehicle ad hoc networks (VANET) are one of the most important technologies to provide various ITS services. While VANET requires rapid and reliable transmission, packet transmission in VANET is unstable because of high mobility. Many routing protocols have been proposed and assessed to improve the efficiency of VANET. However, topology-based routing protocols generate heavy overhead and long delay, and position-based routing protocols have frequent packet loss due to inaccurate node position. In this paper, we propose a position-based routing repair algorithm to improve the efficiency of VANET. This algorithm is proposed based on the premise that AODV (-PGB) can be used effectively in VANET, if the discovery, maintenance and repair mechanism of AODV is optimized for the features of VANET. The main focus of this algorithm is that the relay node can determine whether its alternative node exits and judge whether the routing path is disconnected. If the relay node is about to swerve from the routing path in a multi-hop network, the node recognizes the possibility of path loss based on a defined critical domain. The node then transmits a handover packet to the next hop node, alternative nodes and previous node. The next node repairs the alternative path before path loss occurs to maintain connectivity and provide seamless service. We simulated protocols using both the ideal traffic model and the realistic traffic model to assess the proposed algorithm. The result shows that the protocols that include the proposed algorithm have fewer path losses, lower overhead, shorter delay and higher data throughput compared with other protocols in VANET.

Coherent DLL code tracking and BER effect on QPSK demodulation in wideband DS-CDMA reverse link

In this paper, a novel coherent code tracking scheme called as pilot-aided delay locked loop (PADLL) for QPSK demodulation in wideband DS-CDMA reverse link is proposed. When noncoherent DLL is applied, it suffers from the timing zitter degradation due to squaring loss. The timing zitter formula for PADLL in AWGN is derived and compared with the noncoherent DLL tracking scheme. The analysis shows that the proposed PADLL scheme with the accumulation period of 4 symbols improves the performance of QPSK demodulation by 0.6 dB over the noncoherent code tracking.