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This paper discusses a reliable wireless connection for factory through a distributed antenna system in 920MHz. In this paper, a base station that combines multiple destination nodes installed in a factory and mobile nodes are assumed. In a proposed system, multiple TXs and RXs for a base station are assumed to be fed through a single fiber with Wavelength Division Multiplexing(WDM) or Time Division Multiplexing(TDM) technique with a concept of radio over fiber(RoF). Diversity combining technique are investigated for multiple antenna reception through measurement campaigns in a laboratory room that mimics a factory environment.

This paper discusses a coexisting signal detection technique for sharing the spectrum of an Ultra Wideband (UWB) radio with other radio systems. In some countries' regulations, the Detection and Avoidance technique is required to be implemented in UWB systems so they do not interfere with other radio systems. In most interference avoidance techniques it is necessary to detect emissions of the interfering system and the interfering bands. In this paper, correlation detection is applied for interfering signal detection without band pass filters. In the detector, a Chirp-UWB is prepared as a template waveform. The signal received before UWB communications is correlated with the Chirp-UWB template waveform, and is then integrated. The integral period is decided from the sweep function of the Chirp-UWB and the interfering bands. Therefore the detection technique can detect arbitrary frequency band signals by modifying the integral period. The sweep function of the Chirp-UWB also improves the detection performance. A sine function is adopted for the sweep function of the chirp. The miss Detection Error Rate and False Alarm Rate are evaluated to show the effectiveness of the proposed interference detection technique.

Cooperative transmission system is proposed approach to wireless communication for industrial use. This system is suitable for a factory channel environment, because it can prevent packet delay resulting from long term shadowing with maintaining low power consumption. In this paper, several simulations are made to investigate the packet delay and power consumption properties. They have been carried out based on joint channel model of Rician fading and shadowing attenuation, and a novel evaluation algorithm which calculates the mean packet transmission time and the mean gross transmission energy to assess packet delay and power consumption. Results shows cooperative transmission system maintains low packet transmission time and gross transmission energy even for lower reduced transmission powers. It indicates that cooperative transmission system can reduce the transmission power while maintaining the packet transmission time.

Wavelet packet modulation (WPM) using the discrete wavelet transform is a multiplexing transmission method in which data is assigned to wavelet subbands having different time and frequency resolutions. The WPM keeps data transmission throughput even in tone and impulse interference environments that cannot be achieved with conventional multiplexing methods such as TDM (Time division multiplexing) or OFDM (Orthogonal frequency division multiplexing). In this paper, we propose an effective multicarrier transmission method of WPM for wireless mobile communications. First, the transmission characteristics of WPM in fading environments are minutely investigated. Then, taking the advantage of the WPM and the OFDM that has an equalizing technique in multipath fading environments, we propose a multimode transmission method using them. The adaptive transmission in those fading and interference environments is achieved by using the multimode transmission. Their transmission performances are evaluated by computer simulations.

Pilot symbol-assisted modulation (PSAM) has been proposed to overcome the Rayleigh fading. However, as the fading rate becomes more rapid, it is difficult to provide an exact interpolation with conventional PSAM. To compensate for the fast Rayleigh fading, a PSAM which calculates in the frequency domain rather than the time domain as in conventional PSAM is proposed. Although this PSAM scheme only needs the zero interpolation for fading estimation, it provides a very accurate estimate even in relatively fast Rayleigh fading environments. We introduce this PSAM using fast Fourier transform (FFT) and apply it to 16QAM and then show some results of computer simulations.

This paper presents an experimental evaluation of communication during human walking motion, using the medium access control (MAC) evaluation system for a prototype ultra-wideband (UWB) based wireless body area network for suitable MAC parameter settings for data transmission. Its physical layer and MAC specifications are based on the draft standard in IEEE802.15.6. This paper studies the effects of the number of retransmissions and the number of commands of GTS (guaranteed time slot) request packets in the CAP (contention access period) during human walking motion by varying the number of sensor nodes or the number of CFP (contention free period) slots in the superframe. The experiments were performed in an anechoic chamber. The number of packets received is decreased by packet loss caused by human walking motion in the case where 2 slots are set for CFP, regardless of the number of nodes, and this materially decreases the total number of packets received. The number of retransmissions and the GTS request commands increase according to increases in the number of nodes, largely reflecting the effects of the number of CFP slots in the case where 4 nodes are attached. In the cases where 2 or 3 nodes are attached and 4 slots are set for CFP, the packet transmission rate is more than 95%. In the case where 4 nodes are attached and 6 slots are set for CFP, the packet transmission rate is reduced to 88% at best.

This paper shows a performance evaluation for ultra wideband (UWB)-based wireless body area networks (WBANs) through experiments by using a prototype. Specifications on the physical (PHY) and media access control (MAC) of the prototype are based on the draft standard for IEEE802.15.6. On the PHY, the prototpe uses UWB that its center frequency is 4.096 GHz with bandwidth of around 700 MHz. The MAC layer is based on a superframe structure comprising time slots assigned to a beacon slot, slots for contention access period (CAP), or slots for contention-free period (CFP). Experiments have been conducted with mounting the devices on human body in an anechoic chamber. Over-the-air experiments have been conducted when multiple nodes connecting to a single hub device send packets simultaneously. Through experiment results, it is shown that the number of slots allocated to CAP is crucial in order to maintain packet transmission successfully.

This paper proposes a packet error mitigation technique, LT code, to realize a highly reliable wireless body area network (WBAN). First, we measured received signal strength (RSS) as radio propagations around the human body between two antennas attached to the participants. Next, we calculated packet error rate (PER) based on the measurement results of RSS. Finally, to mitigate the packet error, we evaluate the application of LT code to WBAN.

The volume of Internet traffic increases every year, caused by increased amounts of individual information. Quality of Service (QoS) controls is necessary to manage this traffic. Differentiated Service (Diffserv) is a promising technique to realize scalable QoS control in the internet; extensive efforts have been made for its practical use and it is already introduced in some networks. The control functions for Diffserv are installed in edge and core router, which enables the scalable QoS control. In this paper, we use Diffserv to control QoS on service classes. We propose a new active queue management scheme for Assured Forwarding (AF) services guaranteeing minimum bandwidth provided that Random Early Detection with IN and OUT (RIO) and Weighted Fair Queuing (WFQ) are used as the basic QoS control mechanisms. The proposed method controls the queue threshold values of RIO for each flow and the allocated bandwidth of WFQ for each flow and users' flows. Simulation results show that the proposed scheme reduces the packet discard rate when packets concentrate on a specific flow.

This paper discusses an interference detection technique for ultra wideband (UWB) to share the spectrum with other radio system. A detection and avoidance (DAA) technique are required in UWB system from some countries regulations. In most of interference mitigation techniques, it is required to detect existence of interfering signal and its band. However, some band pass filters are needed to detect various interfering bands detected used by the conventional energy detection. In this paper, the correlation detection is applied for the interfering signal detection without band pass filters. In UWB receiver, a chirp-UWB is prepared as a template waveform. The received signal before UWB communication is correlated with the chirp-UWB template waveform, and the signal is integrated. The integral period is decided from sweep function of the chirp-UWB depending on the interfering bands. The sweep function of the Chirp-UWB is also considered to improve the performance. The sine function is adopted for the sweep function. The miss detection error rate (DER) and false alarm rate (FAR) are evaluated to show the effectiveness of proposed interference detection technique.

Ultra-wideband (UWB) is a useful radio technique for sharing frequency bands between radio systems. It uses very short pulses to spread spectrum. However, there is a potential for interference between systems using the same frequency bands at close range. In some regulatory systems, interference detection and avoidance (DAA) techniques are required to prevent interference with existing radio systems. In this paper, the effect of interference on orthogonal frequency division multiplexing (OFDM) signals from pulse-based UWB is discussed, and an interference mitigation technique is proposed. This technique focuses on the pulse repetition cycle of UWB. The pulse repetition interval is set the same or half the period of the OFDM symbol excluding the guard interval to mitigate interference. These proposals are also made for direct sequence (DS)-UWB. Bit error rate (BER) performance is illustrated through both simulation and theoretical approximations.

Ultra Wideband (UWB) is an attractive technique that enable coexistence with other radio systems to spread spectrum. However, there are potential interferences among those using the same frequency bands and close range. In some country regulations, the interference DAA (detect and avoidance) techniques are required to utilize UWB devices. This paper discusses the interference DAA technique. To utilize multi-carrier pulses made from several narrower sub-band pulses, that is possible to detect and mitigate the interference. The multi-carrier pulses are also suited for the transmitted pulse waveform, since they have advantages for adaptive wave forming. The proposal system is evaluated by the bit error rate performance and signal detection error rate to show their effectiveness. The WiMAX (world interoperability for microwave access) system is considered as an example of the interferer.

The delay guarantee has become an important issue for the Internet. Diffserv is a promising scalable technology to enable QoS control. The control functions for Diffserv disregard the relations between flows in applications and secure bandwidth for each service class collecting multiple flows. This enables a scalable QoS control. This paper proposes a new queue management scheme for AF services guaranteeing minimum bandwidth. This proposal method uses RIO, WFQ, and EDD. The threshold of RIO and the allocation band of WFQ are dynamically controlled by referring to the stay time in the node and the size of the packet, respectively. Simulation results show that the proposed scheme reduces the packet delay time and packet loss probability for higher priority classes.

This paper discusses an interference DAA (detection and avoidance) technique for the ultra wideband (UWB) to share frequency bands with other radio systems. The effect of interference on DS (direct sequence) -UWB system to OFDM (multi band orthogonal frequency division multiplexing) modulated signal is evaluated. The proposed interference mitigation technique focuses on the symbol repetition cycle of DS-UWB. The effective symbol repetition interval is investigated to mitigate the effect of interference. The proposal DAA technique is aimed to the simple hardware structure only to control the symbol repetition cycle.

The paper discusses the effects on biphase UWB radio systems of interference from other systems. Various systems, such as IEEE 802.11a wireless local area network (LAN) and multiband orthogonal frequency division multiplexing (OFDM), are assumed to interfere and the bit error rate performances of a UWB system are evaluated. To reduce the effects of interference, we propose using multicarrier type transmission pulse and template waveforms. We show that the proposed interference mitigation technique is effective, allowing for the coexistence of different wideband systems.

This paper discusses the reduction of interference from coexisting narrowband signal to UWB impulse radio. Two countermeasure techniques are proposed to reduce interference from narrowband signals on only the receiver side. One is to use a filter that rejects the interference signals. The second is to use modified template waveform at the receiver correlation. We propose to use multi-carrier type template waveform that has 11-sub-carrier pulses. When there are some interferers, it is possible to reduce the effect of the interferers by using a modified template waveform that is constructed with the multi-carrier type template removing some sub-carrier pulses that are close to the interfering spectrum. We show that the bit error rate performance is improved by the multi-carrier template.

The wavelet synthesis wave is able to set up the scale freely. So it is possible to use it as UWB transmission wave by compressing time. The possibility of the application to UWB was shown by the following characteristics of the wavelet and some figures of the transmission waveform and spectrum after band restriction. Also, we evaluated the BER characteristic that used Haar as the mother wavelet by computer simulation.

Performance of mobile satellite communication in stratospheric platform along with low Earth orbit and quasi zenith satellite channels are examined. The throughput performance of mobile satellite communications using the slotted and unslotted CDMA-ALOHA systems is studied. Computer simulation is carried out using measured propagation data, and throughput performance for the different propagation characteristics is compared. The packet delay performance is also evaluated along with the altitude of satellite when ARQ (automatic repeat request.) scheme is introduced for error control. This paper studies the effect of transmission control of packets following the channel state monitor to improve throughput performance in measured land mobile satellite channels.

The effects of overhead on the throughput and delay performance of mobile satellite communications using slotted CDMA ALOHA systems are examined. Computer simulation is carried out using measured propagation data, and throughput performances for the different propagation characteristics are compared. The packet delay performance is evaluated along with the altitude of satellite when the ARQ (automatic repeat request) scheme is introduced for error control. Also proposed is the adaptive data rate slotted CDMA ALOHA. In this method the data rate is changed for every packet by the situation of the propagation path and is applied to slotted CDMA ALOHA. The improved throughput, delay time and data rate are shown in case of high traffic.