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In recent years, embedded systems such as various electronic devices equipped with a microprocessor, which acts as a brain of electronic devices, have been spreading due to the improvement of computational capability of system semiconductors and the generalization of large-capacity memory. However, as the requirements of the application using the embedded system increase, the number of the peripheral devices and the interfaces built in the embedded system increases. As a result, it takes much effort and time to develop the embedded system and verify the function. Therefore, in this paper, we propose and study a verification system that can efficiently test the interface to the embedded system.

In this letter, we analyze the outage performance of the signal-to-noise ratio (SNR)-based selective relaying in a relay network, where the relay terminal may retransmit the received signal or remain silent based on the received SNR of the link from the source to the relay. For the proposed relaying scheme, we derive the exact outage probability.

In this paper, we first introduce our own binary CDMA technology. Then we propose a wireless distribution automation system using the binary CDMA technology. The major research items are the binary CDMA distribution automation system, piconet configuration for remote control and monitoring, scheduling for the transmission and reception of data, and ways of applying encryption to protect wireless packet. To verify the possibility of applying wireless transmission to the distribution automation system, we experiment the implemented system in terms of the transmission rate by applying it to a real-world environment.

Randomness is a basic security evaluation item for the most cryptographic algorithms. NIST has proposed a statistical test suit for random number generators for cryptographic applications in the process of AES project. However the test suit of NIST is customized to block ciphers which have the same input and output lengths. It needs to revise NIST's test suit for key derivation functions which have multiple output blocks. In this paper we propose a revised method of NIST's statistical randomness test adequate to the most key derivation functions and some experimental results for key derivation functions of 3GSM and NIST.Keywords:Statistical Randomness Test, Key Derivation Function, Multiple Block Output Function 1. 서 론 1) 정보보호시스템에서 암호 알고리즘이 올바르게 구동되기 위해서는 안전성 높은 대칭키나 공개키 암호알고리즘에 적합한 키관리시스템이 반드시 필요하다. 키관리시스템은 마스터키, 세션키, 암호화키, 인증키 등 키의 중요성 수준과 용도에 따라 다양한 키들을 안전하게 사용하기 위한 것이다. 다양한 용도의 키들은 하나의 마스터키로부터 유도되는 것이 보통이며, 이 때 사용되는 알고리즘이 키유도함수(key derivation function)이다. 그러므로 키관리시스템에서 핵심

The CSMA/CA driven MAC protocols withhold packet transmissions from exposed stations when they detect carrier signal above a certain threshold. This is to avoid collisions at other receiving stations. However, this conservative scheme often exposes many stations unnecessarily, and thus minimizes the utilization of the spatial spectral resource. In this paper, we demonstrate that remote estimation of the status at the active receivers is more effective at avoiding collisions in wireless networks than the carrier sensing. We apply a new concept of the interference range, named as n-tolerant interference range, to guarantee reliable communications in the presence of n (n ≥ 0) concurrent transmissions from outside the range. We design a distributed interference preventive MAC (IP-MAC) using the n-tolerant interference range that enables parallel accesses from the noninterfering stations for an active communication. In IP-MAC, an exposed station goes through an Interference Potentiality Check (IPC) to resolve whether it is potentially interfering or noninterfering to the active communication. During the resolve operation, IPC takes the capture effect at an active receiver into account with interfering signals from a number of possible concurrent transmissions near that receiver. The performance enhancement offered by IP-MAC is studied via simulations in different environments. Results reveal that IP-MAC significantly improves network performance in terms of throughput and delay.

Orthogonal modulation provides low probability of bit error, however its bandwidth efficiency is very low. Biorthogonal code may double the bandwidth efficiency, but its required bandwidth grows exponentially with the number of input bits as in orthogonal modulation. In this paper, we propose a multi-code biorthogonal code keying (MBCK) scheme that significantly reduces the signal bandwidth with the benefit from orthogonal waveform coding maintained. The system consists of multiple waveform coding blocks, and the sum of output codewords is transmitted. A problem with MBCK is that output signal is multi-level, which requires amplifier with high linearity. So it may not be an appropriate scheme for portable unit where power efficiency is highly important. We also propose a modified MBCK scheme that guarantees constant amplitude output. The transmitter of the proposed scheme contains a redundant waveform coder whose input is generated by encoding the information bits. Adding the codewords from all constituent waveform coding blocks, the composite signal has constant amplitude. It is also shown that the redundant bits are not only used to make constant amplitude signal but also used to improve the BER performance at the receiver.

Multicode code-division multiple access (MC-CDMA) and variable processing gain CDMA (VPG-CDMA) are very appealing techniques for achieving high bit-rate data transmission and providing significant capacity gain in wireless channels. This letter provides the peak-to-average power ratio (PAPR) reduction scheme by using a code selective allocation (CSA) in a MC VPG-CDMA system. From simulation results, the MC VPG-CDMA system experiences a reduced PAPR thanks to the CSA algorithm and maintains an acceptable performance degradation even if encountered with nonlinear distortions introduced by a level clipper.

This letter presents a timing synchronization method of high-rate wireless personal area network (WPAN) systems encountered with a multipath fading channel. Two-stage timing synchronization using constant amplitude zero auto-correlation (CAZAC) training symbols and correlation techniques is adopted. At the same time, a simple way of setting a reliable threshold used to estimate WPAN timing is provided.

In this paper a multi-coded variable spreading gain (MC-VSG) CDMA system employing a binary transmission of MC signals by introducing a level clipper termed MC-VSG BNet system, is proposed for the candidate of wireless personal area network (WPAN) and 3G cellular applications. With an emphasis on the MC-VSG BNet physical layer we address the concise specification of the MC-VSG BNet system including the spreading code, level clipping, modulation, coding, frame format, and its applications. From the receiver performance based on simulation results, in addition to simple receiver structure, an acceptable performance degradation of the MC-VSG BNet system over the existing DS/CDMA system is observed, while guaranteeing a high bit rate transmission.

This paper describes two adaptive timing synchronization schemes for a short-ranged Bluetooth system in the partial-band noise environments. One estimates the variance of the partial-band interference, which is utilized for the trigger threshold value of the inquiry scan and page scan states, while second is designed using the scaled partial correlation value for the connection state. Numerical results show the proposed synchronization algorithms are robust to the partial-band noise interference and of low complexity which is suitable for a low-cost personal area network (PAN).

This paper presents a channel estimation and a DC-offset estimation techniques, and two error control methods in a short-ranged Bluetooth system. Each of the Bluetooth devices in the connection state knows the access codes used in the ad-hoc networks, which is utilized as a reference signal for the parameter estimation. Also, the access correlation output can help the error correction schemes of the Bluetooth networks because the correlation output reflects the radio channel environments. The proposed estimators can be implemented without degradation of frame and spectral efficiency thanks to using the access code specified for the Bluetooth system.

This letter proposes a low-complexity single frequency estimator for flat fading channels. The simplified estimator decreases the number of computations in the calculation of the autocorrelation function (AF) when compared to AF-based conventional estimators. The simplified estimator yields a comparable estimation performance to the existing estimators, while retaining the same frequency range.

In this letter, we present a simple way of estimating the integer frequency offset of orthogonal frequency division multiplexing (OFDM) system over a rapidly time-varying channel. By utilizing the channel responses of neighboring subcarriers within one pilot symbol, the frequency offset estimator is derived. We show by simulation that the proposed estimator can accurately estimate the integer frequency offset with reduced computational burden.

In this letter, a multi-phased CDMA system employing a variable spreading gain (VSG) approach is proposed for high-rate applications, based on four algorithms for selecting a multi-code set. From simulation results, in addition to simple receiver structure thanks to level clipping, the multi-phased VSG CDMA system provides an high bit rate transmission, while maintaining an acceptable performance degradation.

This article is concerned with a Bluetooth receiver with the channel estimation and DC-offset estimation. Each of the Bluetooth devices in the connection state knows the access codes used in the ad-hoc networks, which is utilized as a reference signal for the parameter estimation. The proposed estimators can be implemented without degradation of frame and spectral efficiency thanks to using the access code specified for the Bluetooth system.

In this study, we propose a new routing and scheduling algorithm for a relay network of Koinonia V2.0 in which each station transmits either multimedia data or multimedia streaming. Different from previous related works, all stations are used by altruistic users who don’t want to cooperate with each other. With the proposed algorithm, master stations compute paths for each single slave station and allocate divisible wireless resources to each slave station. The system with the proposed scheme reaches Nash Equilibrium Points (NEPs) per every single superframe. Simulation results show that the proposed scheme provides all slave stations with the best path which efficiently balances the capacities of relay users in the two hops.

As wireless network cannot dispense with a proper security measure due to its inborn vulnerability, a new security measure has been developed with an advent of new wireless network technology. Each security measure properly serves the security needs of its associated wireless network as it was intended to. Quality of Protection (QoP) estimates the stability of individual network system by quantifying security intensity. So, it can work as an evaluation standard for the security of network. This paper considers Historical Vulnerability Measure (HVM) and relative weight in total reward function for the improved QoP model. HVM is objectively organized by Flow-based Abnormal Traffic Detection Algorithm for utility function.

An ad hoc network is multi-hop wireless formed by mobile node with no infrastructure. Due to the mobility of nodes in mobile ad hoc networks, the topology of network changes frequently. In this environments, multicast protocols are faced with the challenge of producing multi-hop routes and limitation of bandwidth. We compare the performance of two multicast routing protocols for mobile ad hoc networks - serial multiple disjoint tree multicast routing protocol (serial MDTMR) and adapted core multicast routing protocol (ACMRP). The simulator is implemented with GloMoSim.

We present the design and simulation of an adaptive MAC protocol based on the path-diversity routing information for ad hoc networks. As a routing protocol, a multipath routing protocol based on SPAFAR is used, where a route discovery algorithm finds multiple paths significantly reduce the delay in finding an alternate path. The information about multiple paths discovered in the network layer is exploited by the MAC layer in order to forward a frame over the best hop out of multiple hop choices. The performance of our approach is compared with IEEE 802.11 MAC through the simulation. The results show that our scheme exhibits a significantly better performance rather than the IEEE 802.11 MAC protocol in terms of packet overhead and end-to-end throughput.

In mobile ad hoc networks, the large amount of control overheads associated with discovering and maintaining end-to-end routing path information may not be tolerable. In this paper, we present the design and simulation of a new approach for IEEE 802.11 MAC based on the multipath routing information for ad hoc networks. The routing information about multiple paths discovered in the network layer is exploited by the MAC layer in order to forward a frame over the best hop out of multiple hop choices. The performance of our approach is compared with the one of the IEEE 802.11 MAC protocol via simulation. The results show that our proposed scheme exhibits a remarkable performance improvement over the IEEE 802.11 MAC protocol in terms of packet overhead and end-to-end throughput.

In this paper, we present a simple way of estimating the integer frequency offset of orthogonal frequency division multiplexing (OFDM) system over a rapidly time-varying channel By utilizing the channel responses of neighboring subcarriers within one pilot symbol, the frequency offset estimator is derived. We show by simulation that the proposed estimator can accurately estimate the integer frequency offset with reduced computational burden.

High data-rate wireless personal area networks such as WiMedia are ideal for enabling wireless connectivity and real-time streaming among numerous multimedia applications. However, wireless channels have higher error rates and burstier error patterns than wireline links. In this paper, we propose forward error correction protocol which includes a novel code selection scheme, and addresses two important issues in the transmission of real-time traffic on wireless channels: (1) Adaptability to channel conditions, through prompt reactions to channel variations; and (2) QoS provision, especially throughput and packet error rate. Then, we evaluate the performance of the proposed AFEC. Performance evaluation shows that the proposed technique guarantees the target PER.

IEEE 802.15.3 high-rate Wireless Personal Area Networks (WPANs) is a short range communication technology, in which devices (DEVs) of a piconet communicate with a Piconet Coordinator (PNC). An extension of the communication area in WPAN via formation of a multi-piconet is one of the most challenging issues. Although a concept of multi-piconet has been defined in the IEEE 802.15.3 WPAN standard, a detailed formation mechanism of multi-piconet is not presented. In this paper, we propose efficient multi-piconet formation algorithms, Piconet Coordinator To Device (PCTD) and Device To Piconet Coordinator (DTPC). We evaluate the performance of the algorithms via simulations. The proposed algorithms are shown to extend the communication area with one to three levels and to provide sufficient Channel Time Allocations (CTAs) for subsidiary piconets in IEEE 802.15.3 WPAN.

The IEEE 802.15.3 standard does not specify how to schedule CTA (Channel Time Allocation)s in CTAP (Channel Time Allocation Period) of a superframe. In this paper, we propose a novel scheduling algorithm for channel time allocation of 802.15.3-based HR-WPAN (High Rate Wireless Personal Area Networks), named WFCTA (Weighted Fair Channel Time Allocation). The proposed WFCTA inherently has properties which are necessary for various QoS provisioning, because it is based on TDMA, applied by WFQ algorithm. We explain and compare four implementation cases of WFCTA. We also analyze its worst-case performance in terms of both link utilization and fairness and verify it by simulation.

The IEEE 802.15.3 WPAN(Wireless Personal Area Network) has been designed to provide a very high-speed short-range transmission capability with QoS provisions. Its unidirectional channel allocations for the guaranteed time slots, however, often result in a poor throughput when a higher layer protocol such as TCP requires a full-duplex transmission channel. In this paper we propose a mechanism, called TCP transfer mode, that provides the bidirectional transmission capability between TCP sender and receiver for the channel time allocations(CTAs) of the high-rate WPAN. As our scheme does not require additional control messages nor additional CTAs, the throughput of a TCP connection on the high-rate WPAN can be greatly improved. Our simulation results show that the proposed scheme outperforms any possible ways of TCP transmission according to the current standard of the WPAN.

Design of medium access control (MAC) in wireless sensor networks (WSNs) poses several key factors such as energy conservation and latency. This paper proposes a new MAC protocol referred to as TEEMAC which reduces energy consumption by making the idle nodes sleep to reduce idle listening. TEEMAC is a cluster-based MAC protocol where each cluster is dynamically formed based on cluster-head. Numerical analysis is provided and it shows that the proposed MAC protocol outperforms other existing MAC protocols in terms of energy consumption.

In this paper, we make MAC protocol improvements for performance enhancement of multihop ad-hoc wireless networks. A node in ad-hoc wireless networks can transmit a packet only when the medium is available, and while a packet is being transmitted, no other node is allowed to transmit a packet if they are in carrier sensing range. Carrier sensing range can be divided into two disjoint areas of transmission range and carrier sensing zone, and we address the importance of the protocol procedure when a node is in carrier sensing zone. The characteristic of the carrier sensing zone is that a node can not know when the remaining time of the ongoing transmission session expires or exactly when the media becomes available. Current MAC protocol does not behave in much different way between when a node is in transmission range and in carrier sensing zone. We have conducted a comprehensive simulation to study the performance improvements. The simulation results indicate that the performance is increased and the number of dropped packets due to collision is significantly reduced as much as a half.

BER Performance of Multi-Code Biorthogonal Code Select CDMA system is shown in this paper. MC Biorthogonal CS/CDMA system employs truncation scheme to make binary signals so that it can reduce the value of peak to average power ratio(PAPR). Thus, this system enables to realize cost-efficient and power-efficient RF modules, still maintaining good overall BER performance. However, the nonlinear characteristics of Clipping cause some randomness in specific signal-to-noise ratio. Lloyd-Max Quantization is compared with Clipping for performance improvement. BER performance is shown in AWGN and multi-path fading channels.

In this paper, a multi-coded variable spreading gain (MC-VSG) CDMA system employing a binary transmission of MC signals by introducing a level clipper, termed MC-VSG BNet system, is proposed for a possible candidate of wireless personal area network (WPAN) and 3G cellular applications. With an emphasis on the MC-VSG BNet physical layer and the system performance, we address the concise specification of the MC-VSG BNet system. From the receiver performance based on simulation results, in addition to simple receiver structure, an acceptable performance degradation of the MC-VSG BNet system over the existing DS/CDMA system is observed, while guaranteeing an high bit rate transmission.

A multi-coded CDMA system employing a variable spreading gain (VSG) approach is proposed for high-rate applications, which is based on two algorithms for selecting the multi-code set. From the simulation results, in addition to a simple receiver structure thanks to level clipping, the multi-coded VSG CDMA system provides a high bit rate transmission, while maintaining an acceptable performance degradation of the multi-coded VSG CDMA system over the existing DS-CDMA system.

In this paper, we present an adaptive hopping algorithm for a wireless personal area network (WPAN) receiver applying a frequency hopping. Analytical results based on the closed-form solutions for the aggregate throughput show that the proposed hopping algorithm using two denned hopping criteria is more effective method for the all kinds of interferers and gives an enhanced throughput with a moderate computational complexity.

This paper considers a channel estimation technique in a wireless personal area network (WPAN) system with complementary code keying (CCK) signaling over multipath fading channels. The performance of the proposed coherent detector is compared with that of a noncoherent detector, and a significant improvement of performance is observed in terms of the bit error probability.

We present a coarse frequency-offset synchronization technique for an OFDM-based transmission system with an emphasis on the Eureka-147 DAB receiver. The proposed frequency-offset synchronization algorithm using two defined correlation functions is shown to have high robustness against a large range of symbol timing offset with a moderate implementational complexity.

This paper describes an adaptive timing synchronization scheme and DC-offset compensation technique for a short-ranged Bluetooth system. The synchronization scheme estimates the variance of the partial-band interference, which is utilized for the trigger threshold value of the inquiry scan and page scan states, while DC-offset compensation scheme is designed using the access codes which are known to each Bluetooth device. Numerical results show the proposed synchronization algorithm is robust to the partial-band noise interference and of low complexity. Also, the new DC-offset compensation method shows more reliable estimation ability of DC-offset than the existing method without extra hardware burdens.

A channel estimation technique with interference cancellation in a wireless personal area network system with complementary code keying signalling is described. The performance of the proposed coherent detector is compared with that of a non-coherent detector, and a significant performance improvement as a result of the self-interference cancellation feature is observed.

An adaptive hopping technique for a frequency-hopped WPAN receiver is presented. The proposed algorithm using two defined hopping criteria is more friendly towards all kinds of interferers and gives an enhanced throughput with a moderate computational complexity.

A channel estimation technique for a short-range Bluetooth system is presented. Each Bluetooth device in the connection state knows the access codes used in the ad-hoc networks, which is utilised for the channel compensation. The proposed channel estimator can be implemented without degrading the frame and spectral efficiency by using the access code specified for the Bluetooth system.