We propose parallel rate-variable punctured convolutional coded PPM in photon communication to achieve high energy information efficiency Ie for desired bit error rate (BER) and transmission bandwidth. We theoretically show the BER performance, bandwidth expansion factor β and necessary Ie to achieve BER=10-6 of the proposed systems for some combinations of code rates. It is found that the proposed system can achieve high Ie for desired BER and β by selecting a suitable combination of code rates depending on the channel conditions. Moreover, it is shown that the proposed system has better BER performance than RS-coded PPM in the range of small β.

Detecting Android malwares is imperative. As a promising Android malware detection scheme, we focus on the scheme leveraging the differences of traffic patterns between benign apps and malwares. Those differences can be captured even if the packet is encrypted. However, since such features are just statistic based ones, they cannot identify whether each traffic is malicious. Thus, it is necessary to design the scheme which is applicable to encrypted traffic data and supports identification of malicious traffic. In this paper, we propose an Android malware detection scheme based on level of SSL server certificate. Attackers tend to use an untrusted certificate to encrypt malicious payloads in many cases because passing rigorous examination is required to get a trusted certificate. Thus, we utilize SSL server certificate based features for detection since their certificates tend to be untrusted. Furthermore, in order to obtain the more exact features, we introduce required permission based weight values because malwares inevitably require permissions regarding malicious actions. By computer simulation with real dataset, we show our scheme achieves an accuracy of 92.7%. True positive rate and false positive rate are 5.6% higher and 3.2% lower than the previous scheme, respectively. Our scheme can cope with encrypted malicious payloads and 89 malwares which are not detected by the previous scheme.

This paper proposes two energy-efficient standby mode algorithms in short-range one-to-one 60GHz millimeter-wave (mmWave) communications. Among the many usage scenarios for mmWave radio, file downloading from kiosk terminals or peer-to-peer sync service with portable terminals are of great interest. For these portable terminals, reducing power consumption of standby mode as well as keeping connection setup time short is important. Comparing the power consumption between frame transmission and reception in short-range one-to-one 60GHz mmWave, the power consumed for a frame reception may become larger than that for a frame transmission. The proposed two energy-efficient standby mode algorithms for one-to-one communications assure the connection setup time and take each terminal's different requirement for reduction of its power consumption into consideration. In the proposed algorithms, each terminal accesses asynchronously and operates based on an interval consisting of several sub-intervals. In one proposed algorithm (Prop 1), a terminal transmits a connection request frame (CREQ) once every sub-interval and the other terminal waits for the CREQ during one sub-interval per interval. Thus, Prop 1 reduces the power consumption for CREQ transmission. In the other proposed algorithm (Prop 2), a terminal selects one sub-interval randomly for each interval and transmits CREQs repeatedly during that sub-interval. The other terminal waits for a CREQ during this CREQ transmission period at every sub-interval. Prop 2 saves the power consumption for a CREQ reception. We evaluate the power consumption of standby mode and connection setup time for Prop 1 and Prop 2 by both numerical analysis and computer simulations. We show that the power consumption of the CREQ waiting terminal with the proposed algorithms is more than 10mW lower than that with the conventional algorithm. We also show that our numerical analysis of the proposed algorithms derives the optimum parameters and facilitates system design. Next, we implement Prop 2 in a fully-integrated CMOS transceiver chip-set with antenna, RF/analog, PHY, and MAC for 60GHz proximity wireless communication. This experimental result is the same as the analysis result and it is verified that our proposed standby algorithm works as designed.

This paper proposes a scheme to select an appropriate gateway based on multiple metrics such as remaining energy, mobility or speed, and number of hops in Mobile Ad Hoc Network (MANET) and the infrastructure network integration. The Multiple Criteria Decision Making (MCDM) method called Simple Additive Weighting (SAW) is used to rank and to select the gateway node. SAW method calculates the weights of gateway node candidates by considering these three metrics. The node with the highest weight will be selected as the gateway. Simulation results show that our scheme can reduce the average energy consumption of MANET nodes, and improve throughput performance, gateway lifetime, Packet Delivery Ratio (PDR) of the MANET and the infrastructure network.

In this paper, we propose multiple subcarrier modulation (MSM) for infrared wireless systems using punctured convolutional codes and variable amplitude block codes to minimize the average optical power by allocating the appropriate amplitudes to the puncturing bits. The proposed system maps the coded bits corresponding to zeros in the puncturing table to the amplitudes of subcarriers, while the rate-compatible punctured convolutional (RCPC) code deletes them. We compare two proposed systems with the conventional systems: one block code maps the coded bits corresponding to zeros in the puncturing table to zeros (proposed 1), and the other maps them to the appropriate values among 0, and 1 (proposed 2) so that the required bias can be minimized. We show that the proposed 2 can achieve the minimum required SNR at the same average optical power and the same information rate among all the systems.

In AMS/OFDM systems, base station is in control of the modulation level of each subcarrier, and then, adaptive modulated packet is transmitted from the base station to the mobile station. In this case, the mobile station is required the modulation level information (MLI) to demodulate the received packet. The MLI is generally transmitted as a data symbol, therefore, the throughput is degraded. In an OFDM, the channel response at a particular subcarrier frequency is not supposed to be totally different from its neighboring frequencies, and hence, they must have correlation which depends on the coherence bandwidth of the channel Bc. If we could assign the same modulation level for coherently faded subcarrier block, MLI is required only one time for each subcarrier block. Moreover, we can assign the data on the empty space of pilot signals for increasing the total transmission. In this paper, we propose an adaptive subcarrier block modulation with differentially modulated pilot symbol assistance for downlink OFDM using uplink delay spread.

The performance of coded multi-pulse pulse position modulation (MPPM) consisting of m slots and 2 pulses, denoted as (m, 2) MPPM, with imperfect slot synchronization is analyzed. Convolutional codes and Reed-Solomon (RS) codes are employed for (m, 2) MPPM, and the bit error probability of coded (m, 2) MPPM in the presence of the timing offset is derived. In each coded (m, 2) MPPM, we compare the performance of some different code rate systems. Moreover, we compare the performance of both systems at the same information bit rate. It is shown that in both coded systems, the performance of code rate-1/2 coded (m, 2) MPPM is the best when the timing offset is small. Wheji the timing offset is somewhat large, however, uncoded (m, 2) MPPM is shown to perform better than coded (m, 2) MPPM. Further, convolutional coded (m, 2) MPPM with the constraint length k7 is shown to perform better than RS coded (m, 2) MPPM for the same code rate.

We propose the coherent subcarrier multiplexed (SCM) system with distributing local oscillator (LO) in local loop. The proposed system can realize multichannel transmission with one optical carrier by using the SCM technique and has no need to have LO at each station. Therefore the proposed system becomes cost-effective. The proposed SCM system uses bandpass filter to select a specific channel. We analyze CNR of the system with frequency-shift keying (FSK) in a multioctave configuration. First, the general expression of CNR is derived and is shown for the following parameters such as the number of channels, the position of station on the loop, and the number of stations on the loop. Second, optimal phase modulation (PM) index is derived, and the optimal CNR, minimum required power of lasers, and maximum number of stations that the proposed system can serve are shown by using it. Moreover CNR of the proposed system is compared with that of the system having LO at each station in local loop. It is shown that the proposed system can obtain good performance at the expense of slight increase of the output power of only two lasers at the central station. Therefore the proposed system is cost-effective and practical.

In this paper, we propose a mitigation system of high-level multiple access interference (MAI) for multimedia optical Code-Division Multiple-Access (CDMA) systems using the optical power selector (OPS). The proposed system can eliminate high-intensity MAI at the receiver for low-priority users. Moreover, the proposed system can reduce by half the required number of code sequences compared to the conventional scheme. As a result, the proposed system can increase the number of weights at the same code-length and, thus, obtain higher code spreading gain. We analyze performances of the proposed system and show that both high-priority users and low-priority users achieve lower bit error rates in comparison to the conventional scheme.

In coherent optical subcarrier multiplexing (SCM) systems, the performance degradation of the system due to the phase noise of lasers restricts the maximum number of stations and channels that the system can serve. However, the effects of phase noise on the performance of the coherent SCM system with distributing Local Oscillator (LO) in local loop have not been analyzed. On the other hand, a limit on both the number of channels and stations can be effectively alleviated by using coding technique. In this paper, the effects of phase noise of lasers on the performance of frequency shift keying (FSK) SCM system with distributing LO in local loop are analyzed in terms of carrier-to-noise ratio (CNR) penalty. Second, the effects of Reed-Solomon (RS) coding on FSK SCM system with distributing LO in local loop are analyzed. It is shown that both the number of channels and stations can be increased by using coding technique.

The control of class DE amplifier is an important problem since its switching operations do not satisfy class E switching conditions when the load resistance varies from the initial designed values. Therefore, several of control schemes of class DE amplifier were proposed. However, the changes of the output voltage and the power conversion efficiency by using these controls can be measured only experimentally and thus, they cannot be found theoretically. In this paper, an exact analysis of class DE amplifier with FM and PWM control schemes is presented. From the analysis, we can theoretically derive the output voltage, the power conversion efficiency and so on. Moreover, the frequency and the duty ratio to keep the constant output voltage can be found when the load resistance or the input voltage varies. We indicate that the theoretical predictions are similar to the experimental results quantitatively. The measured efficiency is over 94% with 1.0 MHz and 1.8 W output.

We propose a new interference cancellation technique using reference signals for optical synchronous code-division multiple-access (CDMA) systems. In the proposed system, we use the signature code sequences composed of the group information codes and the modified prime code sequences. The group information codes are added in the forefront of the signature code sequences to estimate the amount of the multiple access interference (MAI). The proposed cancellation scheme can be realized with the simpler structure than the conventional canceller using the time division reference signal, because it can reduce the number of optical correlators from P to two where P is the prime number. We analyze the performance of the proposed system with considering the effects of the MAI, avalanche photodiode (APD) noise, and thermal noise. We show that the proposed canceller has better bit error probability than the conventional canceller.

In cellular systems, autonomous reuse partitioning (ARP) is one of the channel assignment strategy which attains the high spectral efficiency. In the strategy, the movement of mobile stations (MSs) causes the disturbance of reuse partition. Furthermore the smaller cell size causes the spectral efficiency worse. In this paper, we propose a new ARP strategy with reuse partitioning reconstructing, named RP-reconstructing ARP strategy, for microcellular systems. We evaluate the performance of the proposed strategy with blocking rate and forced call termination rate by the computer simulation. The results show that the system with the proposed strategy accommodates 1.5 times as many users as the system with ARP does.

In this paper, we propose an equalizer for indoor infrared wireless systems using on-off keying code-division multiple-access (OOK-CDMA). The proposed equalizer has a decision-feedforward filter to mitigate the effects of inter symbol interference (ISI) at the previous chip position of the sampling instant. We evaluate the performance of indoor infrared wireless systems using OOK-CDMA with three kinds of equalizers: the decision-feedback qualizer (DFE), the feedforward equalizer (FE), and the proposed equalizer. To estimate the impulse response, we use the training sequence that alternates '1' and '0' sequentially. Among three kinds of equalizers, we show that the system with the proposed equalizer can achieve the best bit error rate (BER) performance at high bit rate, while the system with the FE achieves the best BER performance when the bit rate is low.

The convolutional coding combined with continuous phase modulation (CPM) is well known for its good tradeoff between coding gain and bandwidth. On the other hand, the multi-h modulation i.e., the scheme in which plural modulation indices are in cyclically use, is also introduced to obtain the higher power efficiency. However the study of the combination of convolutional coding multi-h scheme is not reported yet. In this study, we consider the combination of convolutional coded CPM with multi-h modulation to achieve larger Euclidean distance. We found that, in some cases, our proposed convolutional coded multi-h CPM can give considerable gains compared with those of conventional single-h scheme.

A general analysis of the effect of the power-law envelope detector by the use of output harmonic components on signal-to-noise ratio (SNR) is performed. By using multiplication and filtering, the additional zero-frequency components are obtained from output harmonic components of the power-law envelope detector. An general expression of the improvement factor on SNR is obtained which is applicable to non-Gaussian noise. It is found that the output SNR can be improved by using the additional zero-frequency components from the output harmonic components of the power-law envelope detector.

We analyze the performance of QPSK systems using complex transversal filters with decision-feedback (DF) taps in the presence of multiple continuous wave (CW) interference and Gaussian noise. The general analytic expressions for the optimum tap weights and minimum mean square errors in the presence of multiple CW interference for both one-sided and two-sided transversal filters with and without DF taps are derived. We find that the output signal-to-noise ratio (SNR) of the one-sided DF filter is most improved among the four types of the filter structures and that multiple CW interference can be almost completely rejected. We also consider the transient behavior of the DF filters in the presence of multiple CW interference. It is found that the magnitudes of the tap weights are proportional to the relative multiple interference power ratios, while they converge to their corresponding steady-state values with the equal rate. It is also found that one-sided DF filter has shorter setting time compared to two-sided DF filter.

Packet contention is one of the fundamental problems that must be overcome in designing packet switches. In banyan network, which has multistage interconnection structure of many small switch elements, we must be concerned with output port conflicts and internal collisions. Dilated banyan network which provides multiple path for internal link can reduce packet loss due to internal collisions in loss system. However, under hot-spot traffic higher packet loss probability is measured at the hot-spot port and the ports close to the hot-spot as coefficient h increases due to the heavy traffic to hot-spot port. In order to moderate the packet loss probability at the hot-spot port we propose the method to disperse the packets which concentrate on the hot-spot route by altering address field of a half of incoming packets. These packets are switched along detour routes. Thus, the traffic concentration toward hot-spot is mitigated and the packet loss probability at the hot-spot port is moderated.

We propose an optical spread-time code-division multiple-access (ST-CDMA) with pulse position modulation (PPM) signaling for high-speed communication networks. We obtain a union upper bound on the bit error rate (BER) considering the multi-access interference (MAI), shot noise and thermal noise at the receiver. As a result, we show that the optical ST-CDMA with PPM signaling improves the BER performance at the same received power and bit rate compared to that with OOK signaling. This leads to an increase of the bit rate at the same BER. Moreover, we show that the proposed system can relax the requirement for spectral resolution compared to the optical ST-CDMA with OOK signaling under the received power and bit rate constraints.

In this paper, we propose Split Multi-path Routing protocol with Load Balancing policy (SMR-LB) to improve TCP performance in mobile ad hoc networks. In SMR-LB, each intermediate node records how many primary paths are attempted to construct as well as which source nodes attempt to construct the primary path. Each intermediate node decides which primary path should be constructed by using the primary path and the source node ID information. As a result, SMR-LB can balance the loads and so reduce the probability of congestion and avoid the continuous link breakage time between the specific source and destination pair. Computer simulation results show that SMR-LB can improve TCP performance compared with the conventional protocols.