In this paper, we analyze the best relay selection scheme for the soft-decision-and-forward (SDF) cooperative networks with multiple relays. The term `best relay selection' implies that the relay having the largest end-to-end signal-to-noise ratio is selected to transmit in the second phase transmission. The approximate performances in terms of pairwise error probability (PEP) and bit error rate (BER) are analyzed and compared with the conventional multiple-relay transmission scheme where all the relays participate in the second phase transmission. Using the asymptotics of the Fox's H-function, the diversity orders of the best relay selection and conventional relay scheme for the SDF cooperative networks are derived. It is shown that both have the same full diversity order. The numerical results show that the best relay selection scheme outperforms the conventional one in terms of bit error rate.

In this paper, a decentralized concurrent transmission strategy in shared channel in Ad Hoc networks is proposed based on game theory. Firstly, a static concurrent transmissions game is used to determine the candidates for transmitting by channel quality threshold and to maximize the overall throughput with consideration of channel quality variation. To achieve NES (Nash Equilibrium Solution), the selfish behaviors of node to attempt to improve the channel gain unilaterally are evaluated. Therefore, this game allows each node to be distributed and to decide whether to transmit concurrently with others or not depending on NES. Secondly, as there are always some nodes with lower channel gain than NES, which are defined as hunger nodes in this paper, a hunger suppression scheme is proposed by adjusting the price function with interferences reservation and forward relay, to fairly give hunger nodes transmission opportunities. Finally, inspired by stock trading, a dynamic concurrent transmission threshold determination scheme is implemented to make the static game practical. Numerical results show that the proposed scheme is feasible to increase concurrent transmission opportunities for active nodes, and at the same time, the number of hunger nodes is greatly reduced with the least increase of threshold by interferences reservation. Also, the good performance on network goodput of the proposed model can be seen from the results.

This letter focuses on the performance analysis on the Adaptive Sidelobe Blanker (ASB) detection algorithm in homogeneous environments, and provides closed summation expressions for Probability of Detection (PD) and Probability of False Alarm (PFA) rate in terms of hypergeometric function. The derived results are more powerful and effective than previous integral ones. Moreover, the framework can be modified to solve the the performance analysis problem involving in F or/and beta distributions. Several numerical evaluations of the convergence rate and computation time are provided and discussed.

Service providers should monitor the quality of experience of a communication service in real time to confirm its status. To do this, we previously proposed a packet-layer model that can be used for monitoring the average video quality of typical Internet protocol television content using parameters derived from transmitted packet headers. However, it is difficult to monitor the video quality per user using the average video quality because video quality depends on the video content. To accurately monitor the video quality per user, a model that can be used for estimating the video quality per video content rather than the average video quality should be developed. Therefore, to take into account the impact of video content on video quality, we propose a model that calculates the difference in video quality between the video quality of the estimation-target video and the average video quality estimated using a packet-layer model. We first conducted extensive subjective quality assessments for different codecs and video sequences. We then model their characteristics based on parameters related to compression and packet loss. Finally, we verify the performance of the proposed model by applying it to unknown data sets different from the training data sets used for developing the model.

Vehicular ad hoc networks have been attracting the interest of both academic and industrial communities on account of their potential role in Intelligent Transportation Systems (ITS). However, due to vehicle movement and fading in wireless communications, providing a reliable and efficient multi-hop broadcast service in vehicular ad hoc networks is still an open research topic. In this paper, we propose FUZZBR (FUZZy BRoadcast), a fuzzy logic based multi-hop broadcast protocol for information dissemination in vehicular ad hoc networks. FUZZBR has low message overhead since it uses only a subset of neighbor nodes to relay data messages. In the relay node selection, FUZZBR jointly considers multiple metrics of inter-vehicle distance, node mobility and signal strength by employing the fuzzy logic. FUZZBR also uses a lightweight retransmission mechanism to retransmit a packet when a relay fails. We use computer simulations to evaluate the performance of FUZZBR.

Multi-Channel MAC protocols increase network throughput because multiple data transmissions can take place simultaneously. However, existing Multi-Channel MAC protocols do not take full advantage of the multi-channel environment, because they lack a mechanism allowing wireless stations to acquire vacant channel and time resources. In this paper, we first establish the basic model of existing Multi-Channel MAC protocols to know the capability of the most important existing protocols. Next, under the condition that each station can use only two transceivers, we propose Multi-Channel MAC protocols that effectively utilize idle channels and potentially available time resources of stations by employing bursts and interrupted frame transfers. We assume a transceiver can behave as either a transmitter or a receiver but not both at the same time. Moreover, we show the effectiveness of our proposal by computer simulation. Furthermore, through the evaluation in the case that each station can use more than two transceivers, we confirm two transceivers' case is best solution in terms of both attained throughput and hardware complexity.

This letter proposes a practical algorithm for video transmission of the scalable extension of H.264/AVC (SVC) over limited bit-rate and varying channel signal-to-noise ratio (SNR). The proposal consists of SVC source-layer dropping and layered FEC using LDPC codes to maximize the video quality. The experimental results show that the proposed method realizes better video quality than the compared unequal error protection (UEP) without source-layer dropping. This implies that the dropping of a certain number of source-layers and using the resultant bit-budget for channel coding is more effective than the other UEP case which uses all possible source-layers.

Obtaining a compact representation of a large-size feature map built by mapper robots is a critical issue in recent mobile robotics. This “map compression” problem is explored from a novel perspective of dictionary-based data compression techniques in the paper. The primary contribution of the paper is the proposal of the dictionary-based map compression approach. A map compression system is presented by employing RANSAC map matching and sparse coding as building blocks. The effectiveness levels of the proposed techniques is investigated in terms of map compression ratio, compression speed, the retrieval performance of compressed/decompressed maps, as well as applications to the Kolmogorov complexity.

To improve simulation precision, the signal model of navigation satellite signal simulators is illustrated, and the generation mechanism and evaluation criteria of an important error source-phase jitter in baseband signal generation, are studied subsequently. An improved baseband signal generator based on dual-ROM look-up table structure is designed with the application of a newly-established concept-virtual sampling rate. Pre-storage of typical baseband signal data and sampling rate conversion adaptive to Doppler frequency shifts are adopted to achieve the high-precision simulation of baseband signals. Performance analysis of the proposed baseband signal generator demonstrates that it can successfully suppress phase jitter and has better spectral performance, generating high-precision baseband signals, which paves the way to improving the overall precision of navigation satellite signal simulators.

This paper proposes Direct Spectrum Division Transmission with spectrum editing technique. The transmitter divides the single carrier modulated signal into multiple “sub-spectra” in the frequency domain and arranges each sub-spectrum so as to more fully utilize the unused frequency resources. In the receiver, the divided sub-spectra are combined in the frequency domain and demodulated. By editing the divided spectrum in the frequency domain, the total bandwidth occupied by the multiple “sub-spectra” is less than that of the modulated signal. The proposed technique allows the unused frequency resources scattered across the bands to be better utilized. Simulations show that the proposed technique makes the bit error rate negligible.

This paper shows a design method for a regular expression matching circuit based on a decomposed automaton. To implement a regular expression matching circuit, first, we convert a regular expression into a non-deterministic finite automaton (NFA). Then, to reduce the number of states, we convert the NFA into a merged-states non-deterministic finite automaton with unbounded string transition (MNFAU) using a greedy algorithm. Next, to realize it by a feasible amount of hardware, we decompose the MNFAU into a deterministic finite automaton (DFA) and an NFA. The DFA part is implemented by an off-chip memory and a simple sequencer, while the NFA part is implemented by a cascade of logic cells. Also, in this paper, we show that the MNFAU based implementation has lower area complexity than the DFA and the NFA based ones. Experiments using regular expressions form SNORT shows that, as for the embedded memory size per a character, the MNFAU is 17.17-148.70 times smaller than DFA methods. Also, as for the number of LCs (Logic Cells) per a character, the MNFAU is 1.56-5.12 times smaller than NFA methods. This paper describes detail of the MEMOCODE2010 HW/SW co-design contest for which we won the first place award.

Photonic integrated circuits (PICs) produced by large-scale integration (LSI) on Si platforms have been intensively researched. Since thermal diffusion from the LSI logic layer is a serious obstacle to realizing a Si-based optical integrated circuit, we have proposed and realized athermal wavelength filters using Si slot waveguides embedded with benzocyclobutene (BCB). First, the athermal conditions were theoretically investigated by controlling the waveguide and gap width of the slot waveguides. In order to introduce the calculated waveguide structures to wavelength filters, the propagation losses and bending losses of the Si slot waveguides were evaluated. The propagation losses were measured to be 5.6 and 5.3 dB/cm for slot waveguide widths of 500 and 700 nm, respectively. Finally, athermal wavelength filters, a ring resonator, and a Mach-Zhender interferometer (MZI) with a slot waveguide width of 700 nm were designed and fabricated. Further, a temperature coefficient of -0.9 pm/K for the operating wavelength was achieved with the athermal MZI.

Multimedia applications such as music or video streaming, video teleconferencing and IP telephony are flourishing in packet-switched networks. Applications that generate such real-time data can have very diverse quality-of-service (QoS) requirements. In order to guarantee diverse QoS requirements, the combined use of a packet scheduling algorithm based on Generalized Processor Sharing (GPS) and leaky bucket traffic regulator is the most successful QoS mechanism. GPS can provide a minimum guaranteed service rate for each session and tight delay bounds for leaky bucket constrained sessions. However, the delay bounds for leaky bucket constrained sessions under GPS are unnecessarily large because each session is served according to its associated constant weight until the session buffer is empty. In order to solve this problem, a scheduling policy called Output Rate-Controlled Generalized Processor Sharing (ORC-GPS) was proposed in [17]. ORC-GPS is a rate-based scheduling like GPS, and controls the service rate in order to lower the delay bounds for leaky bucket constrained sessions. In this paper, we propose a call admission control (CAC) algorithm for ORC-GPS, for leaky-bucket constrained sessions with deterministic delay requirements. This CAC algorithm for ORC-GPS determines the optimal values of parameters of ORC-GPS from the deterministic delay requirements of the sessions. In numerical experiments, we compare the CAC algorithm for ORC-GPS with one for GPS in terms of schedulable region and computational complexity.

In order to implement multidimensional scaling (MDS) efficiently, we propose a new method named “global mapping analysis” (GMA), which applies stochastic approximation to minimizing MDS criteria. GMA can solve MDS more efficiently in both the linear case (classical MDS) and non-linear one (e.g., ALSCAL) if only the MDS criteria are polynomial. GMA separates the polynomial criteria into the local factors and the global ones. Because the global factors need to be calculated only once in each iteration, GMA is of linear order in the number of objects. Numerical experiments on artificial data verify the efficiency of GMA. It is also shown that GMA can find out various interesting structures from massive document collections.

In this paper a novel and effective two phase admission control (TPAC) for QoS mobile ad hoc networks is proposed that satisfies the real-time traffic requirements in mobile ad hoc networks. With a limited amount of extra overhead, TPAC can avoid network congestions by a simple and precise admission control which blocks most of the overloading flow-requests in the route discovery process. When compared with previous QoS routing schemes such as QoS-aware routing protocol and CACP protocols, it is shown from system simulations that the proposed scheme can increase the system throughput and reduce both the dropping rate and the end-to-end delay. Therefore, TPAC is surely an effective QoS-guarantee protocol to provide for real-time traffic.

Efficient silicon-based light sources are expected to be key devices for applications such as optical interconnection. Huge number of researches has been conducted for realizing silicon-based light sources. Most of them utilized silicon-related materials such as silicon nanostructures or germanium, not crystalline silicon, which has been considered as a poor light emitter because of its indirect electronic bandgap. Light emission properties of materials can be tailored not only by modifying the material properties directly, but also by controlling the electromagnetic environment surrounding the material. Photonic nanostructures are a powerful tool for creating the engineered environment. In this paper, we briefly review the mechanisms for improving the light emission properties of materials by photonic nanostructures and present our recent experimental results showing the enhancement of light emission from silicon by introducing photonic crystal structures.

Existing query tree protocols deal with RFID tags in a blind manner. They query tags in a fixed bit order based on the assumption that the tag ID numbers are uniformly distributed throughout the range of the entire ID space because readers have no prior knowledge of the tags. This paper attempts to distinguish RFID applications where readers are already aware of all tags used by the application. We propose a heuristic query tree (H-QT) protocol that uses heuristic to select effective bits from known tags for the best queries in a divide and conquer approach. The performance evaluation shows that the proposed protocol is superior to original query tree protocols because it significantly reduces the number of tag collisions and no tag response.

Short-range Multiple-Input-Multiple-Output (SR-MIMO) transmission is an effective technique for achieving high-speed and short-range wireless communication. With this technique, however, the optimum aperture size of array antennas grows when the transmission distance is increased. Thus, antenna miniaturization is an important issue in SR-MIMO. In this paper, we clarify the effectiveness of using dual-polarized planar antennas as a means of miniaturizing SR-MIMO array antennas by measurements and analysis of MIMO transmission characteristics. We found that even in SR-MIMO transmission, the use of dual-polarized transmission enables higher channel capacity. Dual-polarized antennas can reduce by two thirds the array area that is needed to obtain the same channel capacity. For a transmission distance of two wavelengths, the use of a dual-polarized antenna improved the channel capacity by 26 bit/s/Hz while maintaining the same number of transmitters and receivers and the same antenna aperture size. Moreover, dual-polarized SR-MIMO has a further benefit when zero-forcing (ZF) reception without transmit beamforming is adopted, i.e., it effectively simplifies hardware configuration because it can reduce spatial correlation even in narrow element spacing. In this work, we confirmed that the application of dual-polarization to SR-MIMO is an effective way to both increase channel capacity and enhance transceiver simplification.

Evaluation of addition coefficients introduced by the addition theorems for vector spherical harmonics is one of the most intractable problems in electromagnetic scattering by multi-sphere systems. The derivation of the analytical expressions for the addition coefficients is lengthy and complex while the computation of the addition coefficients is annoyingly time-consuming even with the reasonably fast computers available nowadays. This paper presents an efficient algorithm for calculating addition coefficients which is based on the recursive relations of scalar addition coefficients. Numerical results from the formulation derived in this paper agree with those of previous published results but the algorithm proposed here reduces the computational time considerably. This paper also discusses the strengths and limitations of other formulations and numerical techniques found in the literature.

Undeniable signature, and unpretendable signature schemes have been studied independently. In this paper, efficient schemes which serve as both at the same time are presented. The schemes find their typical application in anonymous auction where the winner cannot deny her bid; nobody can pretend to be the winner; and the anonymity of all losers is preserved. The security of the schemes is proved in the common reference string model under discrete logarithm type assumptions.