We propose a multiuser MIMO precoding algorithm that combines the block Tomlinson-Harashima precoding and the vector perturbation (BTHP-VP). BTHP-VP supports multi-stream transmission without additional estimation of each user's effective channel and achieves full spatial diversity. Computer simulations show that BTHP-VP can achieve similar sum rate and improved BER performance compared to the BTHP with maximum likelihood receiver.

In the IEEE 802.11p WAVE system, applications can directly control the transmission power of the messages sent in WAVE Short Message Protocol (WSMP). This feature enables the vehicles to control the transmission range based on the application requirements and/or the vehicle density. Seemingly straightforward, however, the distributed power control between vehicles can easily go awry. Unless carefully coordinated, the power assignments can irrevocably deviate from the vehicle density pattern. In this letter, we first show that such anomaly happens for a straightforward power control where the power level reacts to the number of messages heard from ambient vehicles. Then in order to resolve the anomaly, we propose an application layer scheme that adapts the WSMP transmission power so that the power assignments precisely reflect the vehicle density pattern.

In large-scale wireless sensor networks, in order to support group mobility of mobile sinks, this letter proposes a novel strategy for energy-efficient and robust data dissemination to the sinks based on cluster-based communication. The novel strategy is composed of two major mechanisms for reduction of structure construction overhead and routing state maintenance overhead: 1) a virtual infrastructure construction through grid-referred clustering and 2) inter-cluster communication by geographic routing relying on recursive location search. Based on the two major mechanisms, the strategy provides representative location management per sink group, distributed data collection, and per-cluster foot-print chaining in order to effectively adapt the traditional strategy for individual mobile sinks. Simulation results prove the proposed strategy shows better performances in terms of energy efficiency and robustness of data dissemination.

In this paper, the inherent problem of the Hough transform when applied to search radars is considered. This problem makes the detection probability of a target depend on the length of the target line in the data space in addition to the received SNR from it. It is shown that this problem results in a non-uniform distribution of noise power in the parameter space. In other words, noise power in some regions of the parameter space is greater than in others. Therefore, the detection probability of the targets covered by these regions will decrease. Our solution is to modify the Hough detector to remove the problem. This modification uses non-uniform quantization in the parameter space based on the Maximum Entropy Quantization method. The details of implementing the modified Hough detector in a search radar are presented according to this quantization method. Then, it is shown that by using this method the detection performance of the target will not depend on its length in the data space. The performance of the modified Hough detector is also compared with the standard Hough detector by considering their probability of detection and probability of false alarm. This comparison shows the performance improvement of the modified detector.

This paper proposes a multiple-input multiple-output (MIMO) precoding scheme for the down link of single user (SU) cooperative base station (BS) systems. The proposed precoding scheme mitigates the performance degradation caused by large inter-BS path-loss imbalance and large intra-BS antenna correlation by controlling two parameters. The proposed precoding scheme multiplexes the multiple layers by adjusting the amplitude of each layer, and then decreases the occurrence probability of the small absolute value of the log likelihood ratio (LLR), and so reduces the bit error rate (BER). Link level simulation results show that the proposed precoding scheme decreases the required signal-to-noise ratio (SNR) of BER = 0.001 by 5.5 dB, 2.2 dB, and 0.7 dB in the case of QPSK and coding rate 1/1, 3/4, and 1/2 respectively. The proposed precoding scheme is also evaluated in terms of spectrum efficiency using rank adaptation and adaptive modulation, showing that it improves the spectrum efficiency when the SNR per a receiver antenna is higher than 4 dB.

Broadcasting information to users about new resource assignments generates a substantial mapping overhead. The mapping overhead influences the system throughput and, in particular, seriously affects the performance of voice-over-Internet protocol (VoIP) services. Persistent scheduling was introduced to reduce the mapping overhead. However, up to now no studies have mathematically analyzed the performance of the persistent scheduling. This paper develops analytical and simulation models and evaluates the performance of the persistent scheduling for VoIP services in mobile WiMAX systems.

In this paper, we design a practical time-reversal quasi-orthogonal space-time block code (TR-QO-STBC) system for broadband multi-input multi-output (MIMO) communications. We first modify the TR-QO-STBC encoding structure so that the interference between the transmitted blocks can be completely removed by linear processing. Two low complex decision-feedback equalization (DFE) schemes are then proposed. One is built from the frequency-domain decision-feedback equalization (FD-DFE). The derived bi-directive FD-DFE (BiD-FD-DFE) cancels the interference among the successive symbols along the time axis. The other one is the enhanced V-BLAST, which cancels the interference between the real and imaginary parts of the spectral components. They have distinct performance characteristics due to the different interference-cancellation strategies. The underlying orthogonal and symmetric characters of TR-QO-STBC are exploited to reduce the computational complexity. Computer simulations confirm that the proposed equalizers can achieve better performance than the existing schemes.

The number of SIP-based services provided by network service providers (NSPs) is increasing. SIP allows NSPs to control services and to collect the information relating to charging for the usage of their customer communications. Monitoring SIP messages (exchanged between SIP proxy servers and user terminals) is vital for providing the stable SIP-based services. Monitoring SIP messages enables NSPs to quickly discover a fault location where SIP messages are lost, and to determine the subsequent recovery solutions. This paper proposes a lightweight method for determining the location of SIP message loss through relationships based on the SIP's retransmission mechanism. Numerical analyses show that the proposed method can locate the lossy links of SIP messages with a low probability of detection failure.

Transmission coordination mechanism (TCM) aids opportunistic routing (OR) to reduce the total number of packet transmissions and improve end-to-end throughput. Existing paradigms based on batch map partitions packets of communication session into segments, and transmit packet segments in batch mode sequentially. However, the rate of successful transmission coordination oscillates due to the oscillation of the number of packets batch transmitted. In this paper, we propose batch sliding window-based TCM to improve the performance of OR. By transmitting packets in continuous batch mode, batch sliding window-based TCM can hold the rate of successful transmission coordination steady. Simulation results show the average end-to-end throughput gain of the proposed TCM is 15.4% over existing batch map-based TCM.

Recently, pairing-based cryptographic application sch-emes have attracted much attentions. In order to make the schemes more efficient, not only pairing algorithm but also arithmetic operations in extension field need to be efficient. For this purpose, the authors have proposed a series of cyclic vector multiplication algorithms (CVMAs) corresponding to the adopted bases such as type-I optimal normal basis (ONB). Note here that every basis adapted for the conventional CVMAs are just special classes of Gauss period normal bases (GNBs). In general, GNB is characterized with a certain positive integer h in addition to characteristic p and extension degree m, namely type-⟨h.m⟩ GNB in extension field Fpm. The parameter h needs to satisfy some conditions and such a positive integer h infinitely exists. From the viewpoint of the calculation cost of CVMA, it is preferred to be small. Thus, the minimal one denoted by hmin will be adapted. This paper focuses on two remaining problems: 1) CVMA has not been expanded for general GNBs yet and 2) the minimal hmin sometimes becomes large and it causes an inefficient case. First, this paper expands CVMA for general GNBs. It will improve some critical cases with large hmin reported in the conventional works. After that, this paper shows a theorem that, for a fixed prime number r, other prime numbers modulo r uniformly distribute between 1 to r-1. Then, based on this theorem, the existence probability of type-⟨hmin,m⟩ GNB in Fpm and also the expected value of hmin are explicitly given.

Device mismatch plays an important role in the design of accurate analog circuits. The common centroid structure is commonly employed to reduce device mismatches caused by symmetrical layouts and processing gradients. Among the candidate placements generated by the common centroid approach, however, whichever achieves better matching is generally difficult to be determined without performing the time-consuming yield evaluation process. In addition, this rule-based methodology makes it difficult to achieve acceptable matching between multiple capacitors and to handle an irregular layout area. Based on a spatial correlation model, this study proposed a design methodology for yield enhancement of analog circuits using switched-capacitor techniques. An efficient and effective placement generator is developed to derive a placement for a circuit to achieve the highest or near highest correlation coefficient and thus accomplishing a better yield performance. A simple yield analysis is also developed to evaluate the achieved yield performance of a derived placement. Results show that the proposed methodology derives a placement which achieves better yield performance than those generated by the common centroid approach.

In this paper we first demonstrate that effective selection functions in power analysis attacks change depending on circuit architectures of a block cipher. We then conclude that the most resistant architecture on its own, in the case of the loop architecture, has two data registers have separate roles: one for storing the plaintext and ciphertext, and the other for storing intermediate values. There, the pre-whitening operation is placed at the output of the former register. The architecture allows the narrowest range of selection functions and thereby has resistance against ordinary CPA. Thus, we can easily defend against attacks by ordinary CPA at the architectural level, whereas we cannot against DPA. Secondly, we propose a new technique called "self-templates" in order to raise the accuracy of evaluation of DPA-based attacks. Self-templates enable to differentiate meaningful selection functions for DPA-based attacks without any strong assumption as in the template attack. We also present the results of attacks to an AES co-processor on an ASIC and demonstrate the effectiveness of the proposed technique.

In order to reduce the convergence time in an iterative procedure, some gradient based preliminary processes are employed to eliminate outliers. The adaptive variable block size is also introduced to balance the accuracy and computational complexity. Moreover, the use of Canberra distance instead of Euclidean distance illustrates higher performance in measuring motion similarity.

This paper evaluates the performance of a pilot-assisted fine carrier frequency offset (CFO) estimation scheme for orthogonal frequency division multiplexing (OFDM) in time-varying channels. An analytical closed-form expression of the mean square error (MSE), of the post-FFT based CFO synchronization scheme, is presented in terms of time-variant fading channels. To verify our analysis in this paper, simulations are carried out within the framework of mobile WiMAX systems.

Relay, which promises to enhance the performance of future communication networks, is one of the most promising techniques for IMT-Advanced systems. In this paper, multiple-input multiple-output (MIMO) relay channels based on outdoor measurements are investigated. We focus on the link between the base station (BS) and the relay station (RS) as well as the link between the RS and the mobile station (MS). First of all, the channels were measured employing a real-time channel sounder in IMT-Advanced frequency band (2.35 GHz with 50 MHz bandwidth). Then, the parameters of multipath components (MPCs) are extracted utilizing space-alternating generalized expectation algorithm. MPC parameters of the two links are statistically analyzed and compared. The polarization and spatial statistics are gotten. The trends of power azimuth spectrum (PAS) and cross-polarization discrimination (XPD) with the separation between the RS and the MS are investigated. Based on the PAS, the propagation mechanisms of line-of-sight and non-line-of-sight scenarios are analyzed. Furthermore, an approximate closed-form expression of channel correlation is derived. The impacts of PAS and XPD on the channel correlation are studied. Finally, some guidelines for the antenna configurations of the BS, the RS and the MS are presented. The results reveal the different characteristics of relay channels and provide the basis for the practical deployment of relay systems.

In this paper, two techniques for implementing a low-power pipelined analog-to-digital converter (ADC) are proposed. First, the time-interleaved correlated double sampling (CDS) technique is proposed to compensate the finite gain error of operational amplifiers in switched-capacitor circuits without a half-rate front-end sample-and-hold amplifier (SHA). Therefore, low-gain amplifiers and the SHA-less architecture can be used to effectively reduce power consumption of a pipelined ADC. Second, the back-end pipelined stages of a pipelined ADC are implemented using a low-power time-interleaved successive approximation (SA) ADC rather than operational amplifiers to further reduce the power consumption of the proposed pipelined ADC. A 9-bit, 100-MS/s hybrid pipelined-SA ADC is implemented in the TSMC 0.13 µm triple-well 1P8M CMOS process. The ADC achieves a spurious free dynamic range (SFDR) of 62.15 dB and a signal-to-noise distortion ratio (SNDR) of 50.85-dB for 2-MHz input frequency at a 100-MS/s sampling rate. The power consumption is 21.2 mW from a 1.2 V supply. The core area of the ADC is 1.6 mm2.

The effect of DC offset on multi-input multi-output (MIMO) direct transceivers with adaptive modulation (AM) is discussed in this paper. A variable-rate variable-power (VRVP) AM system with perfect channel state information (P-CSI) at both the transmitter and receiver in a MIMO scenario is considered. The DC offset is modeled as a zero mean complex Gaussian distributed random variable. By this modeling of the DC offset, the analytical expression for degraded bit error rate (BER) is derived. To derive this analytical expression, we establish a reasonable approximation. The good agreement between the analytical and simulation results shows that the approximation is valid and confirms the accuracy of the analytical expressions. Moreover, an approach to improve the degraded BER in these systems is introduced. For this purpose, we introduce a design for AM MIMO systems that takes account of DC offset and its effectiveness is confirmed. Throughput analysis for the AM MIMO system in the presence of DC offset is presented in this paper too. An analytical expression for throughput is derived and approximated to a simpler equation. At last, throughput results are compared to the simulation outcomes.

The challenge in resource utilization under dynamic environment is how to utilize appropriate resources to the right users at the right time and the right location. In conventional system, centralized management system is applied but it tends to congest when user requests increase or resources rapidly move. Therefore, this paper proposes Autonomous Coordination Technology (ACT) through community organization for resource utilization. In ACT, a node which has surplus resources autonomously constructs community with a surplus-level based size and distributes resources to members which are deficient in resources. ACT consists of autonomous coordination within community and among communities. According to community organization, online property and flexibility can be satisfied. However, it is difficult to achieve service provision timeliness and resource allocation operatability in the mean time. Thus, ACT includes successive transportation method, and autonomous resource allocation which dynamic decision is made by a tradeoff between timeliness and operatability. As a result, the service assurance in terms of timeliness and operatability can be assured. The effectiveness of proposed technology is affirmed through the simulation of taxi dispatching application in terms of response time and standard deviation versus user rates.

A BICM-ID system with 3-dimensional rotated BPSK constellation and signal space diversity (SSD) is proposed to combat the effect of Rayleigh fading. A new criterion based on mutual information is proposed to find the optimal rotation matrix, and the labeling that fits well with the outer code is presented. Simulation results show that at BER of 10-5 over a Rayleigh fading channel, with the code length of 192,000 bits and the iteration number of 100, the performance of the proposed system is only about 0.8 dB from the Gaussian-input Shannon limit and exceeds the limit constrained by the traditional QPSK input without rotation or SSD, at the spectrum efficiency of 1 bit/s/Hz.

In this paper, we have derived a novel integral representation for the ground wave propagation over land-to-sea mixed-paths by applying the Helmholtz-Kirchhoff integral theorem. By using the method of stationary phase applicable uniformly as the stationary phase point approaches the endpoint of the integral, we have derived the asymptotic solution for the scattered fields consisting of the first-order and the second-order diffraction terms. We show that the asymptotic solution thus derived agrees with the asymptotic solution derived by applying the aperture field method (AFM) and the method of stationary phase. We have confirmed the validity and the utility of the novel integral representation and its asymptotic solution by comparing with the widely used mixed-path theorem and the experimental measurement performed in Kanto area and Tokyo bay.