This paper proposes a non-linear adaptive algorithm, the amplitude banded RLS (ABRLS) algorithm, as an adaptation procedure for time variant channel equalizers. In the ABRLS algorithm, a coefficient matrix is updated based on the amplitude level of the received sequence. To enhance the capability of tracking for the ABRLS algorithm, a parallel adaptation scheme is utilized which involves the structures of decision feedback equalizer (DFE). Computer simulations demonstrate that the novel ABRLS based equalizer provides a significant improvement relative to the conventional RLS DFE on a rapidly time variant communication channel.

In this paper, the error performances of several reliability based decoding algorithms over the Rayleigh fading channel with coherent detection are evaluated. The algorithms for which the theoretical bounds are evaluated are the Generalized Minimum Distance (GMD), Chase-type, combined GMD and Chase-type and ordered statistic decodings. All derived bounds are relatively tight and require the same computational effort.

A universal channel decoder for a given family of channels is a decoder that can be designed without prior knowledge of the characteristics of the channel. Nevertheless, it still attains the same random coding error exponent as the optimal decoder tuned to the channel. This paper investigates the duality between universal channel decoders and universal source encoders. First, for the family of finite-state channels, we consider a sufficient condition for constructing universal channel decoders from universal source encoders. Next, we show the existence of a universal channel code that does not depend on the choice of the universal decoder.

We have developed InGaP-channel field effect transistors (FETs) with high breakdown voltages that can be fabricated by using conventional GaAs FET fabrication processes. The buffer and barrier layers were also optimized for the realization of high-voltage operation. The InGaP-channel FET has an extremely high on-state drain-to-source breakdown voltage of over 40 V, and a gate-to-drain breakdown voltage of 55 V. This enabled high-voltage large-signal operation at 40 V. The third-order intermodulation distortion of the InGaP channel FETs was 10-20 dB lower than that of an equivalent GaAs-channel FET, due to the high operating voltage.

In this paper, we propose a new type of hybrid ARQ protocol, in which a channel-adaptive variable rate channel coding scheme is combined with a multi-copy retransmission strategy so as to enhance the system performance under the delay constraint of real-time ATM services in broadband radio access networks. The main feature of a multi-copy retransmission strategy in this scheme is to improve the average throughput for a given Forward Error Correction (FEC) rate, subject to the prescribed cell loss requirement of the real-time wireless ATM services, while augmenting the reliability of channel state information required for a channel-adaptive FEC scheme. Our analysis shows that under a harsh fading channel, the proposed approach is useful for achieving the prescribed cell loss performance without significantly degrading the average throughput performance.

The capacity of quantum channel with product input states was formulated by the quantum coding theorem. However, whether entangled input states can enhance the quantum channel is still open. It turns out that this problem is reduced to a special case of the more general problem whether the capacity of product quantum channel exhibits additivity. In the present study, we apply one of the quantum Arimoto-Blahut type algorithms to the latter problem. The results suggest that the additivity of product quantum channel capacity always holds and that entangled input states cannot enhance the quantum channel capacity.

Devices DC, RF, and microwave power performances between Al0.3Ga0.7As/In0.15Ga0.85As double doped-channel FET (D-DCFETs), conventional doped-channel FETs (DCFETs) and HEMTs are compared with each other. Device linearity and power performance have been improved by a double doped-channel design. The D-DCFETs provides a higher current density, higher gate breakdown voltage, and improves gate operation bias range as well as frequency performance. The linear power gain and output power for D-DCFETs is 19 dB and 305 mW/mm with a power-added efficiency of 52% at Vds = 2.5 V under a 1.9 GHz operation. These advantages suggest that double doped-channel design is more suitable for a high linearity and high microwave power device applications.

Near-optimality of subcodes of the cyclic Hamming codes is demonstrated on the binary additive channel whose noise process is the two-state homogeneous Markov chain, which is a model of bursty communication channels.

New method for deriving the bit error rate (BER) of the BPSK signal in the cochannel interference is proposed, which utilizes the eye pattern of the interference signal, and is different from the conventional method based on the conversion of the interference components to thermal noise. The validity of the proposed derivation method is quantitatively evaluated in terms of the BER performance and is confirmed by comparing with the results obtained by the computer simulation.

This work presents a novel channel assignment scheme for low earth-orbit (LEO) satellite-based mobile communication systems, in which any newly generated call will first be assigned an optimum channel and will no longer be reassigned even when it crosses the boundary of the cell. Thus, the compact reuse distance can be maintained and no handoff failure will occur owing to channel unavailability. Furthermore, a high quality service which guarantees successful handoff processes can be provided. The performance of the proposed strategy is analyzed and compared with the performances of the fixed channel assignment (FCA) scheme and dynamic channel assignment schemes.

This paper considers the design of quadrature amplitude modulation (QAM) transceivers for fixed wireless communications. We propose the use of power control in the QAM transmitter (Tx) to obtain BER performance robust to fading. The gain of the Tx is adaptively adjusted to keep the power of the received signal nearly constant despite of the short term fading and the second multipath. The BER performance of the proposed scheme is analytically evaluated in fixed wireless channels with flat fading and frequency selective fading. Analytic and simulation results show that the use of power control in the Tx can provide the BER performance only about 1 dB inferior to that in additive white Gaussian noise (AWGN) channel.

In [3], the decision feedback channel estimation (DFCE) for M-ary orthogonal modulation in direct sequence/code division multiple access (DS/CDMA) systems was proposed. However, the performance of the DFCE in the multiuser environment is severely degraded due to multiple access interference (MAI). In this letter, to overcome this problem, we modify the DFCE as multistage configurations using a multistage parallel interference cancellation (PIC) scheme. According to the results of our simulations, the performance of coherent demodulation using the proposed multistage DFCE is significantly improved in comparison with conventional demodulation in [3].

An algorithm for blind identification of multichannel (single-input and multiple-output) FIR systems is proposed. The proposed algorithm is based on subspace approach to blind identification, which requires so-called noise space spanned by some eigenvectors of correlation matrices of observations. It is shown that a subspace of the noise space can be obtained by one-step scalar-valued linear prediction and then the subspace is sufficient for blind identification. To acquire the subspace, the proposed algorithm utilizes one-step scalar-valued linear prediction in place of a singular- (or eigen-) value decomposition and hence it is computationally efficient. Computer simulations are presented to compare the proposed algorithm with the original one.

In this paper, we propose an adaptive video frame rate control method, called AFCON, that video encoders use in conjunction with explicit rate based congestion control in the network. First, an encoder buffer constraint which guarantees the end-to-end delay of video frames is derived under the assumption of bounded network transmission delay for every frame data. AFCON is based on the constraint and consists of future channel rate prediction, frame discarding, and frame skipping. Recursive Least-Squares (RLS) is used to predict the low-frequency component of the channel rate. Frame discarding prevents the delay violation of frames due to the prediction error of the channel rate. Frame skipping adapts the encoder output rate to the channel rate while avoiding abrupt quality degradation during the congestion period. From the simulation results, it is shown that AFCON can adapt to the time-varying rate channel with less degradation in temporal resolution and in PSNR performance compared to the conventional approach.

This paper proposes and investigates optimum modulation assignment and band allocation scheme according to subband channel status for BST-OFDM system. The proposed system can adaptively optimize modulation assignment and band allocation according to the conditional parameter under independently fading subband channels. Specifically, in this paper only two optimization problems are treated in terms of modulation assignment. At first, an optimization criterion is a total Bit Error Rate (BER) subject to the constraint conditions of a desired total information bit rate under a fixed effective bandwidth. Another optimization problem is the maximization of a total information bit rate to satisfy a desired BER under a fixed effective bandwidth. Knowledge of the subband channel status is assumed to be updated by the feedback information from a receiver. This paper shows that the proposed system can overperform the conventional system in which all subbands employ the same modulation schemes in terms of BER. In addition, it is shown that the proposed system improves the overall information bit rate, which is not accomplishable in the conventional system.

This paper proposes an outer loop control method of fast transmit power control (TPC) for high-quality data transmission such as that with the average bit error rate (BER) of 10-6 in serial concatenated channel coding combining convolutional (inner) and Reed-Solomon (outer) codings for DS-CDMA mobile radio. In the proposed method, the outer loop control is performed based on the measured intermediate block error rate (BLER) value after inner-channel decoding. Since the number of block errors after inner-channel decoding is much greater than that of the final output after outer channel decoding, fast tracking performance of the sudden changes in the propagation conditions such as the number of multipaths and fading Doppler frequency, i.e., moving speed of the mobile station, is achieved. The experimental results clarify that the measured BLER after outer channel decoding is accurately controlled to almost a constant value from the low to high fading maximum Doppler frequency of up to 480 Hz, and that the measured BER after outer channel decoding is within the range of one-order of magnitude of the antenna diversity reception (meanwhile, the target SIR value after Rake combining varied with the range of 2.5 dB).

This paper discusses the teletraffic characteristics of cellular systems using Dynamic Channel Assignment. In general, it is difficult to exactly and theoretically analyze the teletraffic characteristics of Dynamic Channel Assignment. Also, it is not easy to theoretically evaluate influence of mobility on the traffic characteristics. This paper proposes approximate techniques to analyze teletraffic characteristics of Dynamic Channel Assignment considering mobility. The proposed techniques are based on Clique Packing approximation.

In the current digital mobile communication that is used in the micro cellular system, a Self-Organized Dynamic Channel Assignment (DCA) Method has been proposed to use frequencies effectively. However, its characteristics and operational matters have not been reported yet. This paper takes up the TDMA/TDD system used in the current PHS system and also evaluates the characteristics and operational matters of this method through the actual operational tests. In addition, this paper aims to propose a new DCA method in order to speed up the Channel Segregation and evaluates its effects through the actual operational tests.

We describe a simplified receiver structure having several receiving antennas (i.e., an adaptive array antenna system) and using time-division-multiplexing (TDM) signal processing. Three simplified receiver structures were investigated for use in the antenna system. To confirm the feasibility of using a TDM receiver, both a TDM receiver and a conventional adaptive array receiver were constructed for testing. In our proposed system, several repetitions of the constant modulus algorithm (CMA) are used to reduce co-channel interference (CCI). The frame format used for both receivers was the same as that of the personal handy phone system in Japan. The laboratory testing was done using a fading simulator to enable measurement of the bit error rate. The results are very promising and show the feasibility of the TDM receiver.

This paper focuses on the comparison of OFDM system channel estimation using time domain techniques and using frequency domain techniques. The channel model is based on the Taiwan DTV field-testing results, with static and dynamic multipath distortion. The simulation results prove that the channel estimation performance of the OFDM system in the time domain is better than in the frequency domain.