In this paper, a design method of two-dimensional (2-D) orthogonal symmetric wavelets is proposed by using a lattice structure for multi-dimensional (M-D) linear-phase paraunitary filter banks (LPPUFB), which the authors have proposed as a previous work and then modified by Lu Gan et al. The derivation process for the constraints on the second-order vanishing moments is shown and some design examples obtained through optimization with the constraints are exemplified. In order to verify the significance of the constraints, some experimental results are shown for Lena and Barbara image.

In this paper, we derive the exact average symbol error probability (SEP) of M-ary phase-shift keying and quadrature amplitude modulation signals over Stacy fading channels. The Stacy fading is modelled by a three-parameter generalized gamma or physically α-µ fading distribution, spanning a wide range of small-scale fading such as Rayleigh, Nakagami-m, and Weibull fading. The average SEP is generally expressed in terms of (generalized) Fox's H-functions, which particularizes to the previously known results for some special cases. We further analyze the diversity order achieved by orthogonal space-time block codes in multiple-input multiple-output (MIMO) Stacy fading channels.

Similar to orthogonal frequency-division multiplexing (OFDM) systems, orthogonal frequency-division multiple access (OFDMA) is vulnerable to carrier frequency offset (CFO). Since the CFO of each user is different, CFO compensation in OFDMA uplink is much more involved than that in OFDM systems. It has been shown that the zero-forcing (ZF) compensation method is a simple yet effective remedy; however, it requires the inversion of a large matrix and the computational complexity can be very high. Recently, we have developed a low-complexity iterative method to alleviate this problem. In this paper, we consider the theoretical aspect of the algorithm. We specifically analyze the output signal-to-interference-plus-noise-ratio (SINR) of the algorithm. Two approaches are used for the analysis; one is simple but approximated, and the other is complicated but exact. The convergence problem is also discussed. In addition to the analysis, we propose a pre-compensation (PC) method enhancing the performance of the algorithm. Simulations show that our analysis is accurate and the PC method is effective.

Several quasi-orthogonal STBCs (QOSTBCs) designs using four transmit antennas have been proposed. However, these STBC codes do not maintain full diversity due to the limitations of their complex orthogonal design. In this paper, we propose a code selection method with single-phase feedback which eliminates most of the interference by selecting the QOSTBC with less interference from among two predefined QOSTBCs. The BER performance improvement is investigated in relation with the single-phase feedback scheme at the expense of one bit.

Construction of quaternion design for Space-Time-Polarization Block Codes (STPBCs) is a hot but difficult topic. This letter introduces a novel way to construct high dimensional quaternion designs based on any existing low dimensional quaternion orthogonal designs(QODs) for STPBC, while preserving the merits of the original QODs such as full diversity and simple decoding. Furthermore, it also provides a specific schema to reach full diversity and maximized code gain by signal constellation rotation on the polarization plane.

We present a novel frequency partitioning technique of fractional frequency reuse (FFR) that reduces the effect of co-channel interference and increases the capacity of OFDM systems. The usable sub-channel sets are classified into the common sub-channel sets for all cells and the dedicated sub-channel sets for specific cell types in FFR. The proposed fractional frequency reuse with ordering scheme (FFRO) can decrease the amount of interference in the common sub-channel sets by specially designing the sub-channel sets and the order of sub-channel assignment for specific cell types. Simulation results show that the proposed FFRO yields enhanced performance for both uniform and non-uniform distributions of traffic load.

In approximately synchronous CDMA (AS-CDMA) systems, zero correlation zone (ZCZ) sequences are known as the sequences to eliminate co-channel and multi-path interferences. Therefore, numerous constructions of zero correlation zone (ZCZ) sequences have been introduced e.g. based on perfect sequences and complete complementary codes etc. However, the previous construction method which based on complete complementary code is lacking for merit figures when none of whose elements are zero. In this paper, a new construction method of ZCZ sequences based on complete complementary codes is proposed. By proposed method, non zero elements ZCZ sequences whose merit figure is greater than 1/2 are constructable.

In this letter, we propose combinatorial and search construction methods of 2-D multi-weight optical orthogonal codes (OOCs) with autocorrelation 0 and crosscorrelation 1, called multi-weight single or no pulse per row (MSNPR) codes. An upper bound on the size of MSNPR codes is derived and the performance of MSNPR codes is compared to those of other OOCs in terms of the bit error rate (BER) and evaluated using blocking probability. It is also demonstrated that the MSNPR codes can be flexibly constructed for different applications, providing the scalability to optical CDMA networks.

To evaluate frequency-domain interference between orthogonally intersecting stripline geometries, a lumped mutual capacitance was incorporated into a circuit model, and then a simplified circuit was proposed in the previous paper. The circuit model was approximated from an investigation of the distribution of mutual capacitance but it has remained how the capacitance is approximated. In this paper, a technique using an error function is proposed for the problem. Then, the time-domain response in an analytical expression is studied using the simplified circuit model in a Laplace transformation to make the mechanism clear. Comparing the experimental and the computed results verifies the proposed models.

In this letter, we derive a very accurate closed-form approximate formula for the average achievable rate of stacked orthogonal space-time block code (OSTBC) in Rayleigh fading channels. Some simulations are performed to demonstrate that the derived formula shows better agreement with Monte-Carlo simulation results than the existing closed-form approximate expressions.

Since an FFT-based speech encryption system retains a considerable residual intelligibility, such as talk spurts and the original intonation in the encrypted speech, this makes it easy for eavesdroppers to deduce the information contents from the encrypted speech. In this letter, we propose a new technique based on the combination of an orthogonal frequency division multiplexing (OFDM) scheme and an appropriate QAM mapping method to remove the residual intelligibility from the encrypted speech by permuting several frequency components. In addition, the proposed OFDM-based speech encryption system needs only two FFT operations instead of the four required by the FFT-based speech encryption system. Simulation results are presented to show the effectiveness of this proposed technique.

The measurements for Multiple Access Interference (MAI) problems and the improvement of the data rate are key issues on the advanced wireless networks. In this paper, the nonorthogonal Code Shift Keying Code Division Multiple Access (CSK/CDMA) with received-power adaptive access control scheme is proposed. In our system, a user who is ready to send measures the received power from other users, and then the user decides whether to transmit or refrain from transmission according to the received power and a pre-decided threshold. Not only overcoming the MAI problems, but our system also improve the throughput performance. The throughput performance of the proposed system is evaluated by theoretical analysis. Consequently, the nonorthogonal CSK/CDMA system improves by applying received-power adaptive access control. It was also found that the throughput performance of the nonorthogonal CSK/CDMA system is better than that of the orthogonal CSK/CDMA system at any Eb/N0. We conclude that the nonorthogonal CSK/CDMA system with received-power adaptive access control scheme is expected to be effective in advanced wireless networks.

Phase noise (PHN) can cause the common phase error (CPE) and the inter-carrier interference (ICI), both of which impair the accurate channel estimation in orthogonal frequency division multiplexing (OFDM) systems. In this letter, we build a new signal model parameterized by the channel impulse response, the CPE and the ICI. Based on this model, we derive the maximum likelihood estimator (MLE) and the minimum mean square error estimator (MMSEE). Simulation results show that the proposed schemes significantly improve the performance of OFDM systems in the presence of PHN.

Partial transmit sequence (PTS) is a well known technique used to reduce the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. However, it has relatively high complexity due to the computation of multiple inverse fast Fourier transforms (IFFTs). To reduce this complexity, we use intermediate signals within a decimation in frequency (DIF) radix IFFT and propose a new PTS subblocking technique which requires the computation of only partial IFFTs. Performance results are presented which show a PAPR reduction similar to that with other techniques such as original PTS (O-PTS). Further, we show that complexity reduction can be achieved with either low or high radix IFFT algorithms.

In an orthogonal frequency division multiplexing (OFDM) receiver with direct-conversion architecture, carrier frequency offset (CFO) and direct-current offset (DCO), which cause severe performance degradation, need to be estimated and compensated. Recently, by investigating the subspace of OFDM signal after coarse DCO cancellation using time-domain average, we have proposed a nullspace-based estimator (NSE), for blind CFO and DCO estimation. In this paper, based on an analysis of the cost function of the NSE, we propose a common nullspace based estimator (CNSE). It is shown that by matching the frequency occupation of the received OFDM signal with CFO and DCO, the CNSE can achieve the full performance potential of the NSE. Also, the performance analysis reveals that the CNSE can asymptotically approach the Cramer-Rao bound (CRB) of OFDM CFO estimation in the presence of DCO. Finally the analysis results are confirmed by simulations.

In this paper we analytically investigate the generalization performance of learning using correlated inputs in the framework of on-line learning with a statistical mechanical method. We consider a model composed of linear perceptrons with Gaussian noise. First, we analyze the case of the gradient method. We analytically clarify that the larger the correlation among inputs is or the larger the number of inputs is, the stricter the condition the learning rate should satisfy is, and the slower the learning speed is. Second, we treat the block orthogonal projection learning as an alternative learning rule and derive the theory. In a noiseless case, the learning speed does not depend on the correlation and is proportional to the number of inputs used in an update. The learning speed is identical to that of the gradient method with uncorrelated inputs. On the other hand, when there is noise, the larger the correlation among inputs is, the slower the learning speed is and the larger the residual generalization error is.

In this paper, a new large spreading code set with a uniform low cross-correlation is proposed. The proposed code set is capable of (1) increasing the number of assigned user (capacity) in a multicarrier code division multiple access (MC-CDMA) system and (2) reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system. In this paper, we derive a new code set and present an example to demonstrate performance improvements of OFDM and MC-CDMA systems. Our proposed code set with code length of N has K=2N+1 number of codes for supporting up to (2N+1) users and exhibits lower cross correlation properties compared to the existing spreading code sets. Our results with subcarrier N=16 confirm that the proposed code set outperforms the current pseudo-orthogonal carrier interferometry (POCI) code set with gain of 5 dB at bit-error-rate (BER) level of 10-4 in the additive white Gaussian noise (AWGN) channel and gain of more than 3.6 dB in a multipath fading channel.

This paper presents a new adaptive minor subspace extraction algorithm based on an idea of Peng and Yi ('07) for approximating the single minor eigenvector of a covariance matrix. By utilizing the idea inductively in the nested orthogonal complement subspaces, the proposed algorithm succeeds to relax the numerical sensitivity which has been annoying conventional adaptive minor subspace extraction algorithms for example, Oja algorithm ('82) and its stabilized version: O-Oja algorithm ('02). Simulation results demonstrate that the proposed algorithm realizes more stable convergence than O-Oja algorithm.

An optical CDMA (OCDMA) system is a flexible technology for future broadband multiple access networks. A secure OCDMA network in broadband optical access technologies is also becoming an issue of great importance. In this paper, we propose novel reconfigurable wavelength-time (W-T) optical codes that lead to secure transmission in OCDMA networks. The proposed W-T optical codes are constructed by using quasigroups (QGs) for wavelength hopping and one-dimensional optical orthogonal codes (OOCs) for time spreading; we call them QGs/OOCs. Both QGs and OOCs are randomly generated by a computer search to ensure that an eavesdropper could not improve its interception performance by making use of the coding structure. Then, the proposed reconfigurable QGs/OOCs can provide more codewords, and many different code set patterns, which differ in both wavelength and time positions for given code parameters. Moreover, the bit error probability of the proposed codes is analyzed numerically. To realize the proposed codes, a secure system is proposed by employing reconfigurable encoders/decoders based on array waveguide gratings (AWGs), which allow the users to change their codeword patterns to protect against eavesdropping. Finally, the probability of breaking a certain codeword in the proposed system is evaluated analytically. The results show that the proposed codes and system can provide a large codeword pattern, and decrease the probability of breaking a certain codeword, to enhance OCDMA network security.

In the Evolved UTRA (UMTS Terrestrial Radio Access) uplink, single-carrier frequency division multiple access (SC-FDMA) radio access was adopted owing to its advantageous low peak-to-average power ratio (PAPR) feature, which leads to wide coverage area provisioning with limited peak transmission power of user equipments. This paper proposes orthogonal pilot channel generation using the combination of FDMA and CDMA in the SC-FDMA-based Evolved UTRA uplink. In the proposed method, we employ distributed FDMA transmission for simultaneous accessing users with different transmission bandwidths, and employ CDMA transmission for simultaneous accessing users with identical transmission bandwidth. Moreover, we apply a code sequence with a good auto-correlation property such as a Constant Amplitude Zero Auto-Correlation (CAZAC) sequence employing a cyclic shift to increase the number of sequences. Simulation results show that the average packet error rate performance using an orthogonal pilot channel with the combination of FDMA and CDMA in a six-user environment, i.e., four users each with a 1.25-MHz transmission bandwidth and two users each with a 5-MHz transmission bandwidth, employing turbo coding with the coding rate of R = 1/2 and QPSK and 16QAM data modulation coincides well with that in a single-user environment with the same transmission bandwidth. We show that the proposed orthogonal pilot channel structure using the combination of distributed FDMA and CDMA transmissions and the application of the CAZAC sequence is effective in the SC-FDMA-based Evolved UTRA uplink.