A novel carrier frequency offset and timing offset detection scheme for orthogonal frequency division multiplexing (OFDM) is proposed. The carrier frequency offset is detected by utilizing a certain a-priori known pattern of power differences along the sub-carrier index. The power difference is caused by the collapse of the orthogonal condition. In order that the power differences are effectively influenced by the frequency offset, time-domain windowing is employed. Timing offset is detected by utilizing average phase rotation according to the sub-carrier index. Moreover, by applying the cyclically mapped sequence as a pilot sequence, the computational complexity for reference signal generation is reduced. Additionally, a simplified burst frame searcher is possible if the sliding correlator is applied as a burst frame searcher. The proposed scheme is advantageous for designing the air-frame format, because the operation for synchronization is done using only one pilot symbol. The simulation results of the offset detection performance are shown, and the validity of the proposed offset detection scheme is presented.

In order to realize universal service access of mobile users on the global telecommunication environment, we have to consider the scalable networking architecute based on the distributed object computing technologies. In this paper, we apply TINA to the promising networking architecture, and propose TINA-based scalable model for realizing personal mobility service, which especially focuses on making access to telecommunication services from any legacy systems that do not support such the new environment, using a downloadable module in an end terminal, as well as considering load balance of a whole system. Our proposed model also focuses on exchanging personal infomation of mobile users between different administrative domains, by separating the already-specified user profile information objects into two parts, which are the domain-common part and domain-specific part, and propose secure exchange procedure.

Software radio base and personal station prototypes are proposed and implemented. The prototypes are composed of RF/IF, A/D and D/A, pre- and post-processors, CPU, and DSP parts. System software is partitioned into CPU program and DSP program to use processor resources effectively. They support various air interfaces, some of which are equivalent to the 384 kbit/s transmission rate PHS (personal handy phone system) and a 96 kbit/s transmission rate system. The base station can also be used as a communication bridge between two systems. In order to ease IF filter requirements, the zero-stuff method is employed. Basic transmission and receiving performances are evaluated in an experiment and their results agree well with those expected.

Out-of-head sound localization achieved via binaural earphones is indispensable for a virtual sound system. It is necessary to measure the two transfer functions of each subject, Spatial Sound Transfer Function (SSTF) and Ear Canal Transfer Function (ECTF), for achieving sound localization. It is well known that the quality of sound localization may be poor if the individual transfer functions are not accurately reproduced. This is because each subject has his/her own transfer functions. It is very important to clarify which function includes more individual information, SSTF or ECTF, in order to implement a simpler model. Therefore, we introduce the quantity of "Personal differences" for investigating the subject's transfer functions included in SSTF and ECTF. We measure the transfer functions SSTF and ECTF of 60 subjects in a soundproofed room, and analysis of the data using Principal Component Analysis (PCA) and three subjective assessment tests. This study finds that ECTF differs more widely from person to person than SSTF.

This paper proposes a short delay, error-resilient video transmission scheme for mobile radio channels. Compressed video data are sensitive to channel error. Video coding schemes such as H. 263 use variable length coding so channel error can cause synchronization failure in the decoder and fatally degrade the reconstructed video sequence by triggering intra- and inter-frame error propagation. ARQ prevents all forms of error propagation but significantly increases the transmission delay of the video frame. We propose a new error control scheme to reduces the delay incurred by ARQ; the receiving buffer can transmits the video frame data to the video decoder even if not all ARQ frames containing the video frame are received. The encoder transmits additional information, the Macro Block (MB) size, in the video frame header. Upon receiving this information, the receiving buffer can determine MB length which allows MB de-synchronization to be prevented. For example, if an ARQ frame is lost, the decoder determines the position of the missing MB and replace this MB with the equivalent block in the previous video frame; this prevents intra-frame error propagation. When all ARQ frames are received and decoded correctly, the video frame in the reference video memory is replaced with the correctly decoded one. Simulation results show that the proposed scheme can minimize the delay and the reduction in frame rate caused by retransmission control without intra- and inter-error propagation.

This paper clarifies the appropriate traffic domains for combination between two database schemes (i. e. , HLR database scheme and VLR database scheme) and two call routing schemes (i. e. , Redirection Routing scheme and Look-a-head Routing scheme) in the Global Mobility Network (GLOMONET), which is able to provide global roaming service for the personal telecommunication user. The appropriate domains for combination between each scheme are shown to depend on user's mobility (i. e. the frequency of a user's access to a network where the user stays, the length of the period during which the user stays in the same network). Whether the appropriate domains for the HLR database scheme exist depends only on the frequency of the user's access to the network. When there are appropriate domains for the HLR database scheme, increasing the frequency of the user's access to the network, decreasing the length of the period the user stays in the user's home network, or increasing the length of the period the user stays in a network that isn't the user's home network widens the domains where the VLR database scheme is appropriate.

In a personal communication system (PCS), a scheme for reforwarding call-terminating setup messages (SETUP messages) from a network or a cell station is used to guard against their loss. We have developed a method for evaluating the loss probability of a reforwarding scheme in which the network monitors the response messages from a personal station after forwarding a SETUP message to that personal station and reforwards the SETUP message only if a response message is not received. We started with a stochastic model in which messages registered in the paging-channel queue in a cell station are cyclically forwarded to the wireless area. This model corresponds to the finite-capacity M/D/1/N model with vacation time. We then added a method for calculating the "timeout" probability. Next we expanded the model into one in which the SETUP messages are reforwarded when a response message is not received by the network. This model corresponds to the M/D/1/N model with vacation time and retrials. We then added an approximate method for calculating the loss probability. Finally, using the proposed methods, we clarified the traffic characteristics of PCS call-terminating control.

By integrating three networks, namely, Public Switched Telephone Network (PSTN), Personal Handy-Phone System (PHS) and Intelligent Network (IN) to work together as a Personal Communication Telephone (PCT) service to be offered in the Bangkok metropolis area, the PCT service enables the advent of three new concepts, first, using the same telephone number as that of the fixed line to become a "Personal Number," second, a cell coverage designed to cover larger areas than that of the PHS (by changing hand-out threshold level from 33 dBµV to 30 dBµV and hand-in threshold level from 30 dBµV to 25 dBµV) in order to reduce the muting time during the handover process and provide higher mobility at up to 60 kilometers per hour, and third, a technique of "2 carriers per area" to reduce "call drop." All these techniques will be described in this paper.

In universal personal telecommunication (UPT) environments, UPT networks retain information related to incall/outcall registration in UPT user service profiles in order to provide incoming UPT calls for UPT users in any location who have registered at a terminal. As UPT networks support incall registration, terminal users can be different from terminal owners, and several UPT users can register for incoming calls on a single terminal. Therefore, appropriate third-party protection procedures are needed to protect the rights of terminal owners. A terminal profile database can be used to store information regarding terminal states and incall UPT users registered on a terminal in order to enable third-party protection procedures. In order to manage information within both the terminal profile and the service profile, we propose a request-based scheme for incall registration/deregistration of UPT users and incall registration resets of terminal owners. We evaluate the performance of the scheme in terms of; 1) total cost and, 2) the number of terminal profile accesses per unit time for a terminal.

A direct conversion transmitter IC including a proposed frequency doubler, a quadrature modulator, and a 3-bit variable attenuator was fabricated using BiCMOS technology with fT of 12 GHz. This architecture employing frequency doubler is intended for realizing wireless terminals that are low in cost and small in size. The architecture is effective for reducing serious interference between PA and VCO by making the VCO frequency different from that of PA. The proposed frequency doubler comprises a current-driven 90 phase-shifter and an ECL-EXOR circuit for both low power operation and wide input power range of local oscillator (LO). The proposed frequency doubler keeps high output power even when rectangular wave from LO is applied owing to use of the current-driven 90 phase-shifter instead of a voltage-driven 90 phase-shifter. An LO leakage of less than -25 dBc, an image rejection ratio in excess of 45 dBc, and a maximum attenuation of 21 dB were measured. The transmitter IC successfully operates at LO power above -15 dBm and consumes 68 mA from 2.7 V power supply voltage. An active die size is 1.5 mm3 mm.

This paper proposes a new cell station (CS) configuration for personal communication systems. The proposed CS employs a modified coherent demodulator with 4-branch maximal ratio combining diversity and a burst-by-burst automatic frequency control (AFC) to enhance the coverage. The proposed CS also employs an antenna-sharing diversity transmission to incorporate more than one transceiver block into a small unit with high power efficiency. With these techniques, the BER performance of the uplink control channel (CCH) is flattened regardless of carrier frequency errors within 12 kHz; the diversity gain of uplink traffic channel (TCH) is improved by 2 dB; the downlink transmission power is reduced by 1.9 dB.

The TMN that appears to operate the various communication networks generally and efficiently is developed under the different platform environment such as the different hardware and the different operating system. One of the main problems is that all the agents of the TMN system must be duplicated and maintain the software and the data blocks that perform the identical function. Therefore, the standard of the Q3 interface development cannot be defined and the multi-platform cannot be supported in the development of the TMN agent. In order to overcome these problems, the Farming methodology that is based on the Farmer model has been suggested. The main concept of the Farming methodology is that the software and the data components that are duplicated and stored in each distributed object are saved in the Platform Independent Class Repository (PICR) by converting into the format of the independent componentware in the platform, so that the componentwares that are essential for the execution can be loaded and used statically or dynamically from PICR as described in the framework of each distributed object. The distributed TMN agent of the personal communication network is designed and developed by using the Farmer model.

This paper proposes a new speech codec based on CELP for PHS multimedia communication. PHS portable terminals should consume as little power as possible, and the codec used in them has to be robust against channel errors. Therefore, the proposed codec operates with low computational complexity while reducing the deterioration in speech quality due to channel errors. This codec uses two new schemes to reduce computational complexity. One is moving average scalar quantization for the filter coefficients of the synthesis filter. This scheme requires 90% less complexity to quantize synthesis filter coefficients compared to the widely used vector quantization. The other is pre-selection for selecting an algebraic codebook used as random excitation source. An orthogonalization scheme is used for stable pre-selection. Deterioration of speech quality is suppressed by using CRC and parameter estimation for error protection. Two types of codec are proposed: a 10-ms frame type that transmits 160 bits every 10-ms and a 15-ms frame type that transmits 160 bits every 15 ms. The computational complexity of these codecs is less than 5 MOPS. In a nochannel error environment, the speech quality is equal to that of ITU-TG.726 at 32.0 kbit/s. With 0.3% channel error, both codecs offer more comfortable conversation than G.726. Moreover, at 1.0% channel error, the 10-ms frame type still provides comfortable conversation.

In this paper, we consider conventional signaling link fault tolerance and error correction mechanisms to provide reliable services of mobile multimedia telecommunication network based on ATM (Asynchronous Transfer Mode) technology. Also, we propose an efficient signaling protocol interworking architecture and a reliable distributed interworking network architecture between SS7 based FPLMTS and ATM networks. Besides, we evaluate the performance of proposed method through computer simulation. According to the results, proposed signaling architecture shows efficient and fast fault restoration characteristics than conventional MTP-3/3b based network. Functional signaling protocol stack and network architecture of proposed fast rerouting mechanism provide reliable and efficient restoration performance in view of interworking between SS7 based FPLMTS and ATM networks.

Given the tremendous growth in the cellular phone system and the Personal Hadny-phone System (PHS), it is to be expected that demands for mobile computing using those wireless infrastructures, that is mobile computer access, will dramatically increase. This paper describes high-quality and high-speed data transmission technology for PHS mobile computing and current PHS data transmission standardization activities. Furthermore, wireless agent communication and a service example are presented together with the concept of background communication for the coming wireless multimedia services.

Recently, the number of users utilizing mobile communication services has increased greatly in many information and communication fields. In the future, the number of mobile communication system users will increase even faster, until the rate of diffusion ultimately reaches that of telephones. The day that each person has his own portable mobile terminal is not so far off. Moreover, the systems will not only be used as telephones but also as mobile computing for multimedia information. Digitalization technologies of mobile communication systems needed to realize such mobile computing will be introduced in this paper.

We have developed a GaAs direct-conversion π/4 shifted QPSK modulator IC equipped with variable attenuators for controlling the output power level of the 1.9 GHz Personal Handy Phone system in Japan (PHS). The IC was successfully demonstrated showing state-of-the-art performance with the image rejection ratio of more than 36 dBc at a low input power of -10 dBm in 1.9 GHz frequency range. By using the "Gate Current Control method by Pull-down FET's" (GCCPF), the equipped attenuators vary the output power from 0 dB to -28 dB by 4 dB step. The IC operates at a 2.7 V supply with power dissipation of 259 mW. The 2.64.6 mm2 chip with about 400 elements was fabricated by a 0.5 µm WNx-gate BPLDD GaAs MESFET process.

A GaAs SPDT switch IC operating at a low power supply voltage of 2.7 V has been developed for use in 1.9 GHz band personal handy phone system (PHS). In combination with MESFETs with low on-resistance and high breakdown voltage, the switch IC adopts parallel-LC resonant circuits and utilizes both stacked FETs and an additional shunt capacitor at the receiver side in order to realize low insertion loss, high isolation and low distortion characteristics. An insertion loss of 0.55 dB and an isolation of 35.8 dB were obtained at 1.9 GHz. The IC also achieved an output power of 25.0 dBm at 1 dB gain compression point, a second order distortion of -54.3 dBc and an adjacent channel leakage power of -66 dBc at 600 kHz apart from 1.9 GHz at 19 dBm output power.

We propose a new network architecture nemed Holonic Network for personalized multimedia communications, which is characterized by distributed cooperative networking based on autonomous management and all-optical transport networks. We than propose autonomous routing method. Moreover, an information searching method and a route generation method with network maps, which are essential for this network, are proposed. Lastly, we evaluate the proposed network performance by theoretical analysis and system emulation.

Personal communication systems (PCS) have more signalling traffic than conventional fixed networks and require large-scale databases to manage users' profiles, which are sets of data items, such as the location the user is currently visiting and the user's authentication key, necessary for a PCS user to be provided with PCS services. This paper focuses on inter-network roaming in PCS environments. In designing a PCS supporting roaming service, it is essential to avoid increased signalling traffic and data searching time in the database. We first identify the appropriate domains for three routing schemes-Direction Routing, Redirection Routing, and Look-ahead Routing-from the viewpoints of the number of signals for inter-network roaming and roaming probability. We do this for two kinds of PCS database network architecture, Home Location Register (HLR) and Visitor Location Register (VLR), and show that Look-ahead Routing is the best scheme for the HLR network architecture (considering the number of signals for intra-network and inter-network database access) and that in the VLR network architecture, the decreasing of the roaming probability expands domains for which Redirection Routing is appropriate. We also propose a generic PCS data model that inter-network roaming interfaces can use to search effectively for a user's profile. The data model clarifies the contents of a set of data items which share certain characteristics, data items that the contents compose, and the relationships (data structures) between sets of data items. The model is based on the X. 500 series recommendations, which are applied for an Intelligent Network. We also propose a data structure between sets of data items using the directory information tree and show the ASN. 1 notations of the data model.