Recently, according to Eco-technology accelerating, new types of traction motor with the high efficiency and power are demanded. This paper presents that the Hairpin winding is applied to a design of the electric vehicle traction motor for the high efficiency and power density. Generally, the winding method using the toroidal coil has the restriction which is the unnecessary spaces between coils. However the Hairpin winding method can reduce the gap between coils, therefore the space factor is higher than that of winding methods. However, because of using the full pitch winding and wave winding, this method has the disadvantages of increasing the THD of back electromotive force and torque ripple. Thus, to minimize the THD and torque ripple, the full factorial method, Response surface method and the step skew to the rotor are applied. The paper presents the motor design using the Hairpin winding for the high space factor, and the analysis result by using RSM, the step skew and full factorial method shows the reduced space harmonics.

As today's networks evolve towards an IP-based integrated network, the role of transmission control protocol (TCP) has been increasing as well. As a well-known issue, the performance of TCP is affected by its loss recovery mechanism that is comprised of two algorithms; fast retransmit and fast recovery. Although retransmission timeout (RTO) caused by multiple packet losses can be avoided by the modified fast recovery algorithm of TCP NewReno or selective acknowledgement (SACK) option, RTO cannot be avoided if a retransmitted packet is lost. To cope with the problem, lost retransmission detection (LRD) has been proposed for each TCP in B. Kim and J. Lee (2004). In this paper, we evaluate the LRD algorithm by tracing TCP sender's behaviors for several scenarios where a retransmitted packet is lost. In addition, we consider the 'conservation of packets' rule to advocate that LRD does not violate fairness with TCP connections that do not support the LRD algorithm.

This paper investigates the possibility of using pre-equalization on the up-link of a time division duplex (TDD) OFDM system. The application of this principle is suggested to enhance the spectral efficiency by omitting the usage of training sequences on the up-link. This is desired in order to enable the efficient transmission of very short data packets, like single ATM cells. The principle proposed also keeps the complexity of synchronization low at the base station, which is accessed by many users. We describe a simple scheme to limit the transmission power on the up-link. The power is kept constant by deleting subcarriers that are severely attenuated due to fading. Parameter estimation steps for retrieving the data at the base-station are explained and evaluated. Those include the estimation of the timing-offset, the carrier phase offset, and the received magnitude. Coherent demodulation is considered.

The characteristics of spreading sequences significantly affect the performance of the forward link DS-CDMA system in a fading channel. The bit error rate (BER) is a function of the signal-to-interference ratio (SIR) which has different characteristics depending upon the spreading sequence. In this paper, the SIR is analyzed when orthogonal codes and pseudo random codes are used as the spreading sequence. The BER performance is analyzed with and without the use of convolutional codes. The use of orthogonal codes can cancel out the interference signals having the same path delay, but the use of random codes cannot, resulting in significant performance degradation. As a result, the BER performance of the orthogonal spreading system is much better than that of the random spreading system. Even in the case of many multipaths, the number of users achieving a fixed BER value in the orthogonal spreading system is twice larger than that in the random spreading system. The analytical results are verified by computer simulation.

This paper describes a method of deriving channel parameters for a time-dispersive (=frequency-selective) radio channel from simple wide-band power measurements. A novel relationship is found allowing the estimation of the root-mean-square (RMS) delay spread from such data. Furthermore, we describe a set of equations that can be used for fitting the (measured) channel parameters to a mathematical model, the so-called frequency-domain (FD) model. We also show a simulation procedure, which directly implements the mathematical description of the channel. The output of this procedure-realizations of frequency-selective channel transfer functions-may be used for instance in the investigation of OFDM systems. The study is restricted to the small-scale modeling; Rayleigh and Ricean fading channels are considered. The estimation of the RMS delay spread is based on the frequency-domain level crossing rate (LCR/sub f/), which is derived from the FD-channel model. It is shown that the RMS delay spread is proportional to the LCR/sub f/. Because of the simple hardware required for finding the LCR/sub f/, the suggested measurement method is particularly interesting for the millimeter-wave frequency band (>30 GHz). However, it can be used at other frequencies as well, where standard laboratory equipment is sufficient for conducting the measurements. The accuracy of this technique depends on the bandwidth observed and can be increased further by combining multiple measurements performed within a small local area.

This paper presents a hardware platform that enables the realistic emulation of wide-band air interfaces at low cost. Real-time base-band algorithms for the modulator and demodulator are implemented on separate-and thus independent-DSP evaluation boards. A channel simulation sub-system is suggested, consisting of another DSP board for multipath channel simulation and of analog I/Q-modulators and -demodulators for emulating carrier frequency offsets. The latter allows assessment of frequency synchronization techniques. Reduced speed (bandwidth -40 kHz) tremendously reduces implementation difficulties. The advantages and limitations compared to full-speed hardware and pure computer simulation are elaborated on. The system is used by the authors to assess real-time algorithms for OFDM air-interfaces, but it can be used for other modulation schemes as well. Another possible application is in the education of electrical engineers.

In this paper, a novel frequency-domain model (FD-model) for the frequency selective Ricean fading radio channel is presented. Frequency domain filtering and the Hilbert transform are used to generate samples of the channel's transfer function with appropriate frequency correlation properties (WSSUS model). One of the main advantages of this approach is the availability of analytical expressions relating channel parameters to model parameters. This can be used to conveniently fit the proposed channel model to any of the (measured) channel parameters. Based on this new model, level crossing statistics of the channel's transfer function were investigated. Results have shown that the level crossing rate (LCR/sub f/) is proportional to the RMS delay spread (RDS) of the channel. This implies that from the LCR/sub f/, which can be derived from wide-band power measurements, an accurate estimation of the RDS is possible. Previously, expensive and cumbersome equipment like network analyzers was required to measure this parameter. Computational results have been evaluated with measurements and a time-domain model for the 60 GHz frequency band.