A design methodology of Random Switching Logic (RSL) using CMOS standard cell libraries is proposed to counter power analysis attacks against cryptographic hardware modules. The original RSL proposed in 2004 requires a unique RSL-gate for random data masking and glitch suppression to prevent secret information leakage through power traces. In contrast, our new methodology enables to use general logic gates supported by standard cell libraries. In order to evaluate its practical performance in hardware size and speed as well as resistance against power analysis attacks, an AES circuit with the RSL technique was implemented as a cryptographic LSI using 130-nm and 90-nm CMOS standard cell library. From the results of attack experiments that used a million traces, we confirmed that the RSL-AES circuit has very high DPA and CPA resistance thanks to the contributions of both the masking function and the glitch suppressing function.

A dual-mode pulse-triggered flip-flop design supporting functional versatility is presented. A low-complexity unified logic module, consisting of only five transistors, for dual-mode pulse generation is devised using pass transistor logic (PTL). Potential threshold voltage loss problem is successfully resolved to ensure the signal integrity. Despite the extra logic for dual-mode operations, the circuit complexity of the proposed design is comparable to those of the single mode designs. Simulations in different process corners and switching activities prove the competitive performance of proposed design against various single mode designs.

Reliable data transmission is desirable in wireless sensor networks due to the high packet loss rate during multi-hop transmissions. To reliably transmit data for event-driven applications, packet loss recovery mechanism is needed. For loss recovery, sensor nodes need to keep packets in their buffers until transmissions successfully complete. However, since sensor nodes have limited memory, packets cannot be buffered for a long period of time. This letter proposes an efficient buffer management technique that caches data packets for appropriate amount of time to minimize the resource requirements and at the same time provide reliable data transmission among sensor nodes.

Spectrum sensing is a fundamental function for cognitive radio network to protect transmission of primary system. Cooperative spectrum sensing, which can help increasing sensing performance, is regarded as one of the most promising methods in realizing a reliable cognitive network. In such cooperation system, however the communication resources such as sensing time delay, control channel bandwidth and consumption energy for reporting the cognitive radio node's sensing results to the fusion center may become extremely huge when the number of cognitive users is large. In this paper, we propose an ordered sequential cooperative spectrum sensing scheme in which the local sensing data will be sent according to its reliability order to the fusion center. In proposed scheme, the sequential fusion process is sequentially conducted based on Dempster Shafer theory of evidence's combination of the reported sensing results. Above all, the proposed scheme is highly feasible due to the proposed two ordered sequential reporting methods. From simulation results, it is shown that the proposed technique not only keeps the same sensing performance of non-sequential fusion scheme but also extremely reduces the reporting resource requirements.

We present an orthogonal frequency division multiple access (OFDMA) based multichannel slotted ALOHA for cognitive radio networks (OMSA-CR). The performance of an infinite population based OMSA-CR system is analyzed in terms of channel capacity, throughput, delay, and packet capture effect. We investigate the channel capacity for OMSA-CR with perfect or imperfect spectrum sensing. We introduce the proposed CR MAC based on two channel selection schemes: non-agile channel selection (NCS) and agile channel selection (ACS). Comparing them, we show the tradeoff between complexity and system performance. We verify the proposed CR system model using numerical analysis. In particular, using simulation with a finite populated linear feedback model, we observe the OMSA-CR MAC tradeoff between throughput and minimum delay whose results matched those of the analytical framework. Numerical results for the proposed system throughput are also compared to conventional MACs, including pure ALOHA based CR MAC.

The selection cooperation is a basic and attractive scheme of cooperative diversity in the multiple relays scenario. Most previous schemes of selection cooperation consist only one relay-stage in which one relay is selected to retransmit, and the signal from the selected relay is not utilized by other relays. In this paper, we introduce a two relay-stage selection cooperation scheme. The performance can be improved by letting all other relays to utilize the signal from the first selected relay to make another selection and retransmission in the second relay-stage. We derive the closed-form expression of the outage probability of the proposed scheme in the high SNR regime. Both theoretical and numerical results suggest that the proposed scheme can reduce the outage probability compared with the traditional scheme with only one relay-stage. Furthermore, we demonstrate that more than two relay-stage can not further reduce the outage probability. We also study the dependence of the proposed scheme on stage lengths and topology, and analyze the increased overhead.

The occurrence of via defects increases due to the shrinking size in integrated circuit manufacturing. Redundant via insertion is an effective and recommended method to reduce the yield loss caused by via failures. In this paper, we introduce the redundant via allocation problem for layer partition-based redundant via insertion methods [1] and solve it using the genetic algorithm. At the same time, we use a convex-cost flow model to equilibrate the via density, which is good for the via density rules. The results of layer partition-based model depend on the partition and processing order of metal layers. Furthermore, even we try all of partitions and processing orders, we might miss the optimal solutions. By introducing the redundant via allocation problem on partitioning boundaries, we can avoid the sub-optimality of the original layer-partition based method. The experimental results show that the proposed method got 12 more redundant vias inserted on average and the via density balance can be greatly improved.

Recent advances in cooperative communication and wireless Network Coding (NC) may lead to huge performance gains in relay systems. In this context, we focus on the two-way relay scenario, where two nodes exchange information via a common relay. We design a practical Superposition Coding (SC) based NC scheme for Decode-and-Forward (DF) half-duplex relaying, where the goal is to increase the achievable rate. By taking advantage of the direct link and by providing a suboptimal yet efficient power division among the superposed layers, our proposed SC two-way relaying scheme outperforms the reference schemes, including the well-known 3-step DF-NC scheme and the capacity of 2-step schemes for a large set of SNRs, while approaching closely the performance bound.

Accurate registration is crucial for medical image analysis. In this letter, we proposed an improved Demons technique (IDT) for medical image registration. The IDT improves registration quality using orthogonal gradient information. The advantage of the proposed IDT is assessed using 14 medical image pairs. Experimental results show that the proposed technique provides about 8% improvement over existing Demons-based techniques in terms of registration accuracy.

In this paper, we propose an error diagnosis technique based on clustering LUT elements to shorten the processing time. By grouping some elements as a cluster, our technique reduces the number of elements to be considered, which is effective to shorten the processing time for screening error location sets. First, the proposed technique partitions the circuit into FFR (fanout-free region) called cluster, which is a subcircuit composed of LUT elements without fanout. After screening the set of clusters including error locations, this technique screens error location sets composed of elements in the remaining set of clusters, where corrections should be made. Experimental results with benchmark circuits have shown that our technique shortens the processing time to 1/170 in the best case, and rectifies circuits including 6 errors which cannot be rectified by the conventional technique.

Statistical timing analysis for manufacturing variability requires modeling of spatially-correlated variation. Common grid-based modeling for spatially-correlated variability involves a trade-off between accuracy and computational cost, especially for PCA (principal component analysis). This paper proposes to spatially interpolate variation coefficients for improving accuracy instead of fining spatial grids. Experimental results show that the spatial interpolation realizes a continuous expression of spatial correlation, and reduces the maximum error of timing estimates that originates from sparse spatial grids For attaining the same accuracy, the proposed interpolation reduced CPU time for PCA by 97.7% in a test case.

In this paper, a scheme for constructing the flat frequency spectrum of interleaved frequency division multiple access (IFDMA) is proposed. Since IFDMA is one of the single carrier modulation schemes, the frequency spectrum components are fluctuated and depend on the information data sequence. Even if IFDMA modulation scheme makes frequency spectrum dispersive for obtaining frequency diversity gain, frequency diversity gain is reduced by the fluctuation of frequency spectrum. In addition, in decision directed channel estimation (DDCE), which achieves good channel estimation accuracy in fast fading environment, the accuracy of channel transfer function estimated at the significant attenuated frequency component is much degraded. In the proposed technique, a random phase sequence is multiplied to the information data sequence for constructing the flat frequency spectrum. As a result, the frequency diversity gain is enlarged and the accuracy of channel estimation by DDCE is improved. Furthermore, we consider the blind estimation technique for the random phase sequence selected by transmitter. We show the effects of the proposed scheme by computer simulation.

Todays cellular systems reach their limits for data rate due to the continuously increasing amount of subscribers using wireless service for business purposes or in leisure time (smartphone effect). Thus, recent research focuses on concepts for interference management for cellular OFDMA systems. This paper addresses various techniques related to this topic, while considering the concepts with lowest complexity and backhaul costs as promising candidates to be applied first. Starting from interference canceling receivers over multi-user MIMO using fixed precoding to multi-cell interference estimation, which improves the precision of link adaptation, we discuss closed-loop cooperative transmit beamforming using multiple base stations grouped into a wireless distributed network (WDN), which is denoted as coordinated multi-point joint transmission in the 3GPP LTE-Advanced standardization. It is obvious, the more sophisticated these techniques are, the higher the demands for feedback and backhaul become. Performance results are provided by employing multi-cell simulations according to recommendations from 3GPP. In addition, feasibility of coordinated multi-point joint transmission is demonstrated in a real-time prototype setup, i.e. in the Berlin LTE-Advance Testbed.

This paper presents a voltage reference that utilizes the virtually diode-connected MOS transistors, biased in the weak-inversion region. The proposed architecture increases the gain of the feedback loop that consequently reduces the system sensitivity, and hence improves the PSRR. The circuit is designed and simulated in a standard 0.18 µm CMOS technology. The simulation results in HSPICE indicate the successful operation of the circuit as follows: the PSRR at DC frequency is 86 dB and for the temperature range from -55C to 125C, the variation of the output reference voltage is less than 66 ppm/C.

Currently, there are various routing methods that consider the energy in a wireless sensor environment. The algorithm we consider is a low-rate wireless personal area network, viz., 802.15.4, and ZigBee routing network. Considering, the overall organization of the network energy efficiency, we suggest a logical position exchange (LPE) algorithm between specified nodes. Logical positioning means connecting high sub-networks and low sub-networks based on the neighbor nodes information of the address ID, and depth in the ZigBee tree topology network. When one of the nodes of the tree topology network, which is responsible for connecting multiple low sub-networks and high sub-networks, has difficulty performing its important roles in the network, because of energy exhaustion, it exchanges essential information and entrusts logical positioning to another node that is capable of it. A partial change in the logical topology enhances the energy efficiency in the network.

Transmission of convolutionally encoded source-codec parameters over noisy channels can benefit from the turbo principle through iterative source-channel decoding. We first formulate a recursive implementation based on sectionalized code trellises for MAP symbol decoding of binary convolutional codes. Performance is further enhanced by the use of an interpolative softbit source decoder that takes into account the channel outputs within an interleaving block. Simulation results indicate that our proposed scheme allows to exchange between its constituent decoders the symbol-level extrinsic information and achieves high robustness against channel noises.

A low peak-to-average-power-ratio (PAPR) transceiver with a time-frequency cyclic shift orthogonal keying (TF-CSOK) technique is proposed for the uplink multi-carrier CDMA (MC-CDMA) system over multiple access interference (MAI) and multipath interference (MPI) channels. The low complexity structure of the TF-CSOK MC-CDMA system is designed to involve the FCSOK and TCSOK techniques to combat MPI and MAI effects, respectively. In particular, at the besestation, the multiuser detector employs the maximum likelihood (ML) rule and the TFSOK despreading and demapping techniques to acquire the M-ary modulation gain and diversity gain. Simulation results show that the multuser receiver has the robustness against strong MAI. Moreover, it outperforms the conventional single-carrier frequency division multiple access (SC-FDMA) system and the conventional MC-CDMA system under MAI and MPI environments.

A 9-bit 100-MS/s successive approximation register (SAR) ADC with low power and small area has been implemented in 65-nm CMOS technology. A tri-level charge redistribution technique is proposed to reduce DAC switching energy and settling time. By connecting bottom plates of differential capacitor arrays for charge sharing, extra reference voltage is avoided. Two reference voltages charging and discharging the capacitors are chosen to be supply voltage and ground in order to save energy and achieve a rail-to-rail input range. Split capacitor arrays with mismatch calibration are implemented for small area and small input capacitance without linearity degradation. The ADC achieves a peak SNDR of 53.1 dB and consumes 1.46 mW from a 1.2-V supply, resulting in a figure of merit (FOM) of 39 fJ/conversion-step. The total active area is 0.012 mm2 and the input capacitance is 180 fF.

In this letter, we address a strategy to enhance the signal-to-interference plus noise ratio (SINR) of the worst-case user by using cooperative transmission from a set of geographically separated antennas. Unlike previously reported schemes which are based on either the power control of individual antennas or cooperative orthogonal transmission, the presented strategy utilizes the minimum-mean-squared error (MMSE) filter structure for beamforming, which provides increased robustness to the external interference as well as the background noise at the receiver. By iteratively updating the cooperative transmission beamforming vector and power control (PC), the balanced SINR is obtained for all users, while the transmission power from each antenna also converges to within the constrained value. It is demonstrated that proposed MMSE beamforming significantly outperforms other existing schemes in terms of the achievable minimum SINR.

This paper proposes a concept for a new technical field called wireless distributed network (WDN) as a strategic technical field to enable flexible networking and radio resource management (RRM) to cope with dynamic variation of spatially distributed traffic demands. As the core technical subject areas for the WDN, this paper identifies distributed networking for flexible network creation, cooperative transmission and reception for flexible link creation, and dynamic spectrum access for flexible radio resource management, and explains their technical features and challenges for constructing the WDN. This paper also discusses some already being studied application fields as well as potential future directions of the WDN applications.