Shiro Handa

Multiple-symbol differential detection of APSK based on MAP criterion

The multiple-symbol differential detection scheme based on the MAP criterion is adopted to APSK. The decision rule to estimate the transmitted signals is constructed theoretically which includes the terms of the channel noise power. The symbol error rate (SER) performance of 16APSK under the decision rule is evaluated. It is confirmed that the performance shows good approach to that of the ideal coherent detection on the AWGN channel. We also consider the transmission over the Rayleigh fading channel and confirm the performance through the computer simulation for the star QAM and the (4,12) QAM which are the typical constellations for 16APSK.

Data tracking and effect of frequency offset to simultaneous collecting method for wireless sensor networks

In the packet access of wireless sensor networks, a distributed access protocol is employed to avoid packet collision but it also causes delay. Therefore, real time data collection is difficult. In wireless communication for simultaneous multidata collection (WC-SDC), sensed data are projected onto the parameters of the wireless communication. The specific feature of the sensed data appears in received signals. Even if the transmitted signal from each sensor collides by simultaneous access, the mixture sensed can be separated by using the specific features. Therefore, the real time data collection is achieved. However, frequency mismatch causes the fluctuation of sensed data, which gives the adverse impact to data separation. In this paper, a data tracking method is used for the data separation in the WC-SDC. We clarify the accuracy of data separation and the impact from the frequency offset. We propose a method for coping with the frequency offset and the error tracking. From the numerical results, our proposed method accurately achieves data separation even under 7% frequency offset normalized by the minimum frequency resolution.

Multiple-Symbol Differential Detection for Space-Time Block Codes over Fast Rayleigh Fading Channels

In this paper, multiple-symbol differential detection (MSDD) for space-time block codes (STBC) is considered over fast Rayleigh fading multiple-input multiple-output (MIMO) channels. The decision metric is derived by considering the fading autocorrelation, and the M-algorithm is adopted to reduce the computational complexity of the decision metric. Simulation results demonstrate that MSDD is effective to fill the performance gap between conventional differential detection and coherent detection of differential STBC by extending the observation interval.

Multi-target tracking based on features of sensing results and wireless parameters for physical wireless parameter conversion sensor networks

In wireless sensor network, in addition to long life operation and low complexity, small time delay and large traffic acceptance for supporting various machine-to-machine communications are required. Although physical wireless parameter conversion sensor network (PHY-C SN) achieves simultaneous data collection, the separation of mixed sensing results is a difficult problem. For separating each sequence of them, multi-target tracking technique is available, but failing when similar sequences are included in the sensing data. This paper proposes a novel data separation method based on multi-target tracking that uses both features of the sensing results and the wireless parameters. We show the accuracy of our method through computer simulations.

Iterative multiple-symbol differential detection of differential LDPC codes

In this paper, an iterative multiple-symbol differential detection (MSDD) scheme for differential LDPC codes is considered over slow and fast Rayleigh fading channels. The metric computation algorithm and its simplified algorithm used to output soft information for MSDD are derived. Simulation results demonstrate that the bit error rate (BER) performance of the proposed system is close to that of coherent detection by extending the observation interval and iterative decoding. In addition, the simulation results show that the proposed system, which can exploit the time diversity benefit of the fast fading channels, has much better performance over fast fading channels.

Approximate equation of average bit-error rate in DS-CDMA systems over fading channels

The transmission quality in mobile wireless communications is affected not only by additive white Gaussian noise, but also by multipath fading, which drastically changes the amplitudes and phases of wireless signals. It is one of the key themes in direct-sequence code-division multiple-access systems to evaluate average bit error rate (BER) performances as parameters of the Doppler frequency, the delay profile, the number of simultaneous access users, and so on. This paper proposes the approximate equation for easily calculating the average BER over fading channels (multiray fading models). The performance evaluations are carried out in the two-ray model, the IMT2000 model, and the COST207 model. It is confirmed from the coincidence of approximate results with computer simulation results that the proposed approach is applicable to a variety of parameters.

Fuzzy early discard (FED) to improve TCP Reno performance over ATM-UBR

We propose a fuzzy logic-based buffer management scheme called fuzzy early detection (FED) to improve TCP Reno performance over ATM-UBR service. FED employs the strategies of early congestion detection and selective packet discard to achieve its design goals, and adopts EPD to prevent frequent buffer overflows. Its performance is compared to that of pure EPD through simulation. The effects of TCP MSS and propagation delay on their performances are studied. Our simulation results prove that FED is superior to EPD in terms of efficiency and scalability, while its fairness remains comparable with the latter.

Performance evaluation of multi-target tracking for PhyC-SN

Physical conversion sensor networks (PhyC-SN) achieve simultaneous data collection in wireless sensor networks. Although the PhyC-SN can recognize the median and the outliers of all the sensing data simultaneously, their separation into each sensor data is a difficult task. To address this task, we have proposed a data separation method that utilizes multi-target tracking with use of the sensing data and the received spectrum power for the separation. Even if some of the sensor data are close to each other, the instantaneous power of the sensor data bearing signal is a useful feature for the separation. In this paper, we clarify the separation accuracy of our separation method under various wireless environments by computer simulation.

Physical layer network coding with multiple untrusted relays for physical layer security

We proposed the physical layer security (PLS) under the untrusted relay in the wireless communication with the physical layer network coding (PLNC). In PLNC, the two information source accesses the relay station, simultaneously and thus it is difficult for the relay station to demodulate each signal due to the masking-effect from the other signal. As a result, the leakage of information to the untrusted relay is avoidable. The transmit power control (TPC) for the balancing between the two received signal powers is powerful. The secure capacity is enlarged but has not been optimized for maximizing the secure capacity. In this paper, the quasi-optimization of TPC for enlarging secure capacity is derived in the wireless communication with the untrusted relay and PLNC.

Theoretical analysis of BER in DPSK/OFDM systems with postdetection diversity reception

In OFDM systems with differential phase shift keying (DPSK), it is possible to apply differential modulation in either the time or frequency domain, depending on fading channel conditions, such as Doppler frequency shift and delay spread. Meanwhile, postdetection diversity for DPSK is attractive because the cophasing function necessary in predetection combiners is not required. The paper proposes a simple calculation method, that is an approximate closed-form equation of the bit error rate (BER) in DPSK/OFDM systems with postdetection diversity over both time and frequency selective Rayleigh fading channels. The validity of the proposed method is demonstrated by the fact that the BER performances given by the derived equation coincide with those by Monte Carlo simulation.