An increase in the system capacity and maximum user bit rate is required for wireless multimedia communications that offer high speed signal transmission such as simultaneous voice and data transmission. This paper proposes a Time Division Multiple Access-Time Division Duplex method combined with an Alternated Frequency Duplexer (TDMA/TDD-AF) for TDMA based wireless personal communications. The newly proposed duplexing method uses the same frequency band and all time slots within a TDMA frame for both up-stream and down-stream transmission. This enables a two-fold increase in the number of time slots within a TDMA frame and the maximum user bit rate compared with the conventional TDMA/TDD method. Transmitter diversity is also applied to improve the transmission quality under multipath fading environments. The traffic performance of the proposed method is approximated theoretically compared with the conventional TDMA/TDD systems on the assumption that an infinite number of terminals are in a cell. The results indicate that the TDMA/TDD-AF method significantly improves the blocking probability when the system is asynchronized among adjacent cells and the number of usable carriers is high.

Spread-spectrum (SS) sharing with comb spectrum structure in a microcell/macrocell cellular architecture in order to increase spectral efficiency is proposed. Such method employs a filter in the code division multiple access (CDMA) transmitter to feature comb spectrum structure, and suppress interference with a narrowband time division multiple access (TDMA) system in using together in SS sharing. The relationship between microcellular capacity and macrocellular capacity of the system is explored and compared to those of conventional SS sharing and orthogonal sharing. To be concrete, we investigate two cases, i.e., using no power control and ideal power control in the TDMA system. In both cases, the proposed SS sharing gives better capacity results than the conventional SS sharing and in the comparison when ideal power control is used in th. TDMA system, it even has the property to oppose the orthogonal sharing in ideal condition without interference.

In packet radio networks with TDMA, the throughput performance of network should be degraded due to the unequal traffic of each user. To overcome this problem, Mini-Slotted Alternating Priorities (MSAP) and TDMA with Parallel Transmission (TDMA/PT) were proposed. Especially, TDMA/PT can attain the thorughput performance more than one, even under unequal traffic. However, TDMA/PT cannot be used for mobile networks, because each terminal should know the location of every other terminal. In this paper, we propose an entirely new protocol named Slot Reservation TDMA with Parallel Transmissino: SR-TDMA/PT," which is suitable for mobile networks because a central station is able to locate every terminal easily. The central station also reserves time slots for each terminal so as to transmit packets in parallel as much as possible. Therefore, the throughput performance of SR-TDMA/PT is higher than TDMA/PT. We describe SR-TDMA/PT in detail and evaluate the performance of this protocol by simulation under various conditions.

A CATV network which has a switched double star configuration, fiber to the home (FTTH) and full digital transmission has been tested to see the feasibility with one Head-End (HE), one Central Office (CO), one Distribution Center (DC), and 25 subscribers. Also POTS and NISDN services have been provided to 5 subscribers. Single mode optical fibers are fully deployed from a HE to subscribers. A PON with TDM/polling scheme has been implemented considering the economic issue. Also in the outside plant, we tried to use the existing facility including the in-house duct. This paper deals with the results of the trial and some issues on the operational view.

This paper investigates the performance of an integrated voice and data transmission protocol that can be used in mobile communication networks, e.g. mobile cellular and LEOGEO satellite networks. Voice and data are concentrated at place such as base station in a cellular network. Time sensitive voices are supported by the concentrator in the manner of TDMA. Loss sensitive data are collected, stored, and transmitted using idle TDMA slots. Data users transmit data to the concentration point using ALOHA protocol. Characterization of data arrivals to the concentrator is done by the method of moment matching. The emphasis of this study is on the data performance in terms of packet loss rate, average buffer occupancy, and mean packet waiting time. It is demonstrated through numerical examples that a buffer of reasonable size is good enough to offer satisfactory performance. The analysis is also validated by computer simulations.

This paper proposes a new digitized group modulator for radio base station transmitters of multi-carrier TDMA. This group modulator can flexibly set carrier spacing and features a simple construction as a result of employing the Simple Fractional Sampling technique. A group modulator LSI was designed and built using 0.5-µm BiCMOS technology, and a π/4-shifted QPSK group modulator was constructed using this LSI. Experiments confirm that the modulator simultaneously generates multiple carriers in a wide bandwidth without the need for precise adjustment and there is little difference between each of the carriers in terms of BER performance. Moreover, experiments confirm that the group modulator's burst-output (frequency hopping) performance is excellent.

Multiple TDMA bursts assignment between a base station and a personal terminal will be required for multimedia communications that offers high speed signal transmission such as voice and data simultaneous transmission. This paper proposes a reliable packet transmission method for TDMA based wireless multimedia communications. The proposed method employs an adaptive transmission rate control according to the packet length and a burst diversity technique is applied to improve the frame error rate of a packet. The frame error rate performance has been approximated theoretically by using fade- and infade-duration statistics of a Rayleigh fading channel and a computer simulation has been carried out for two control channels, FACCH/SACCH (Fast/Slow Associated Control CHannel) in the PHS as well as GSM. Both results indicate that the frame error rate is dramatically improved, about one order, when two bursts have different frequency and improved by about 25% when the two bursts have the same frequency.

Exploitation of air interfaces for mobile communications is rapidly increasing because of diversified service demands, technology trends and radio propagation conditions. This paper summarizes the radio and optic interaction devices and systems that can solve the future problems resulting from spreading demands in mobile multimedia communications. The concept of the Virtual Free Space Network (Radio Highway Network) is proposed for universal mobile access networks that can support any mobile service or radio air-interface. As one example of the proposed network, the optical TDMA network for radio is analyzed and results of some theoretical calculations are shown.

To connect among many radio base stations by using optical fiber bus link in microcellular system, subcarrier multiplexing (SCM) is excellent in simplicity and flexibility. But performance degradation due to optical beat noises is severe problem. To solve this problems, this paper proposes a new type of intercell connection bus fiber-optic link (ICBL) using time division multiplexing, called TDM-ICBL. This paper also analyzes transmission performance of TDM-ICBL theoretically and compares with SCM-ICBL. The analysis clarifies that while the number of RBSs connected to SCM-ICBL is severely restricted by beat noises, TDM-ICBL is more useful than SCM-ICBL when there are many number of connected RBSs.

A transmission power control technique on a TDD-CDMA/TDMA system for wireless multimedia networks is proposed. The assumed network connects mobile terminals to a node of an ATM based high speed LAN through a radio central unit. Only human interface facilities are implemented into the terminal so that users access integrated services through the node of the network. The uplink (from a mobile terminal to a radio central unit) employs a CDMA scheme to transmit human interface signals (2.4kbit/s) and the downlink employs a TDMA scheme to transmit display interface signals (24 Mbit/s). Both the CDMA and the TDMA signals occupy the same frequency band. To mitigate bit error rate degradation due to the fading, the radio central unit estimates the impulse response of the channel from the received CDMA signals and controls the transmission power of the TDMA signals to compensate the fading attenuation. The bit error rate performance of the downlink with the proposed transmission power control is theoretically analyzed under several fading conditions. Numerical results using the Nakagami-m fading model and recent propagation measurements show that the proposed power control technique compensates the fading attenuation and improves the bit error rate performances. The bit error rate of the downlink is reduced from 10-2 to 10-5 at the symbol SNR of 20dB by employing the proposed transmission power control, which is less sensitive to the severity of the fading. Furthermore, the proposed transmission power control is implemented without increasing the terminal complexity because all the processing on the power control of the downlink is carried out only in the radio central unit.

This paper deals with the method of integration of voice and data in wireless communication systems. By applying the DSV (Data Steal into Voice) technique to D-TDMA (Dynamic Time Division Multiple Access) systems, this paper presents an MAC (Media Access Control) method of integration of voice and data for the systems such as cellular radios and cordless phones. After a brief review of the D-TDMA scheme and the DSV technique, the protocol called D-TDMA/DSV is described. Then, a static analysis to derive the channel capacity and a dynamic analysis to evaluate the throughput and delay performance are presented. An extension of TFA (Transient Fluid Approximation) analysis is employed in the dynamic analysis. With the same system parameters, the capacity of D-TDMA/DSV is compared with that of the traditional D-TDMA. Under the limitation of the blocking probability required for cellular radios, some numerical examples of dynamic analysis are given to show the throughput and delay performance of the system.

This paper proposes a symbol rate controlled adaptive modulation/TDMA/TDD for future wireless personal communication systems. The proposed system controls the symbol rate according to the channel conditions to achieve wide dynamic range of the modulation parameter control as well as to improve the delay spread immunity. The main purpose of the proposed system is to increase the data throughput with keeping a certain transmission quality, especially in frequency selective fading environments. For this purpose, the proposed system predicts the C/N0 (carrier power-to-noise spectral density ratio) and the delay spread separately, and selects the optimum symbol rate that gives the maximum bit rate within a given bandwidth satisfying the required BER. The simulated results show that the proposed system can achieve higher transmission quality in comparison with the fixed symbol rate transmission system in both flat Rayleigh and frequency selective fading environments. The results also show that the proposed system is very effective to achieve higher bit rate transmission in frequency selective fading environments.

A channel equalization technique on a time division duplex CDMA/TDMA system for wireless multimedia networks is investigated, and the bit error rate performance of the system is theoretically analyzed. The assumed network connects mobile terminals to a node of ATM based high speed LAN through a radio central unit. Only human interface facilities are implemented into the terminal so that users access integrated services through the node of the network. The uplink (from a mobile terminal to a radio central unit) employs a CDMA scheme to transmit human interface signals and the downlink employs a TDMA scheme to transmit display interface signals. Both the CDMA and the TDMA signals occupy the same frequency band. To mitigate bit error rate degradation due to fading, the radio central unit estimates the impulse response of the channel from the received CDMA signals and subtracts the replica signal to cancel the major intersymbol interference (ISI) component. Numerical results using the Nakagami-m fading model and recent propagation measurements show that the proposed TPC technique compensates the fading attenuation and the proposed CEQ cancels the major ISI component. The bit error rate performance of the downlink with the proposed CEQ is superior to that with the DFE by 12dB of the symbol SNR at the BER=10-6 over a specular channel, and the system with the proposed CEQ achieves a BER=10-6 at the symbol SNR=12dB. Furthermore, the channel equalizer is implemented without increases in complexity of the terminal because all the processing on the equalization is carried out only in the radio central unit.

A novel wireless multimedia network employing a time division duplex CDMA/TDMA scheme is proposed. The network connects mobile multimedia terminals to an ATM based LAN through a radio central unit, and provides both uplink and downlink with unbalanced data rates in the same frequency band. The uplink (from a mobile terminal to a radio central unit) employs a CDMA scheme to transmit low speed human interface signals (-2.4kbit/s), and the downlink employs a TDMA scheme to transmit high speed video signals (-24Mbit/s). The data rates of both links are independent from that of the LAN. The uplink also employs a RAKE receiver and a forward error correction (FEC) scheme using a BCH code in order to reduce bit errors caused by multipath fading. To mitigate channel degradation caused by the near-far problem and multipath fading, a transmission power control (TPC) method for both links and a channel equalizer (CEQ) for the downlink are proposed. The control signals for the TPC and the CEQ are estimated from the impulse response of the channel which is extracted as the output of the matched filters in the CDMA receiver. Theoretical analyses are performed to evaluate the bit error rate (BER) characteristics of the proposed network. The BER performance is derived for a general multipath fading condition modeled by the Nakagami-m distribution and a typical delay profile. Numerical calculation using recent propagation measurements shows the bit error rates of both uplink and downlink to be less than 10-6 when both of the TPC and the CEQ are employed if there are some specular components in the received signals. This excellent performance can cut a way to realize a mobile multimedia terminal for customer premises. Furthermore, the configuration of the mobile terminal is quite simple even if the high speed TDMA signals are received over a multipath fading channel.

This paper reviews very high-speed optical signal processing technology based on the instantaneous characteristic of optical nonlinearities. Focus is placed on 100-Gbit/s optical time-division multiplexing (TDM) transmission systems. The key technologies including ultrashort optical pulse generation, all-optical multiplexing/demultiplexing and optical timing extraction techniques are alse described together with their major issues and future prospects.

This paper presents a fully digital high speed (60 Mb/s) Quadrature Phase Shift Keying (QPSK)/Offset QPSK (OQPSK) burst demodulator for radio applications, which has been implemented on a 0.5 µm Complementary Metal Oxide Semiconductor (CMOS) master slice Very Large Scale Integrated circuit (VLSI). The developed demodulator VLSI eliminates analog devices such as mixers, phase-shifters and Voltage Controlled Oscillator (VCO) for bit-timing recovery, which are used by conventional high-speed burst demodulators. In addition to the fully digital implementation, the VLSI achieves fast carrier and bit-timing acquisition in burst modes by employing a reverse-modulation carrier recovery scheme with a wave-forming filter for OQPSK operation, and a bit-timing recovery scheme with bit-timing estimation and interpolation using a pulse-shaping filter. Results of performance evaluation assuming application in Time Division Multiple Access (TDMA) systems show that the developed VLSI achieves excellent bit-error-rate and carrier-slipping-rate performance at high speed (60 Mb/s) with short preamble words (less than 100 symbols) in low Eb/No environments.

This paper gives field experimental results on 16-ary quadrature amplitude modulation/time division multiple access (16QAM/TDMA) and trellis coded 16QAM/TDMA systems for land mobile communications in order to evaluate its capability of achieving large capacity and high quality data transmission. Pilot symbol aided space diversity and symbol timing synchronization based on maximum likelihood (ML) estimation are applied to both 16QAM/TDMA and trellis coded 16QAM/TDMA to improve transmission quality. For the trellis coded 16QAM/TDMA, trellis coding with Viterbi decoding and 2-frame symbol interleaving are further employed. The field experiments were conducted in the Tokyo metropolitan area of Japan. The results show that 16QAM/TDMA and trellis coded 16QAM/TDMA are practical modulation/access schemes for land mobile communication systems.

This paper proposes a new burst coherent demodulator that improves transmission quality of microcellular TDMA/TDD systems for personal communications and has configuration suitable for low power consumption with LSIC-implementation. To achieve the better transmission quality, the proposed demodulator employs coherent detection with a unique carrier recovery scheme that can operate without any preamble for carrier recovery. In addition, the demodulator uses a clock recovery scheme with clock phase estimation using twice differentiation, which eliminates hangup and attains fast clock acquisition at 2 samples/symbol. Experimental results clarify the superiority of the proposed coherent demodulator for microcellular TDMA/TDD systems. The proposed coherent demodulator reduces the irreducible frame error rate by 40%, and achieves 4dB improvement at the frame error rate of 10% compared with differential detection under the Rayleigh fading (fD/fs=810-5, τrms/Ts=510-2) typical of personal communication environments.

This paper proposes a semi-autonomous frame synchronization scheme for a TDMA (Time Division Multiple Access)-TDD (Time Division Duplexing) personal communication system to realize accurate frame synchronization in a simple manner. The proposed scheme selects specific adjacent base stations by the station indicator (SID), carries out high resolution frame timing control, and compensates the propagation delay between base stations by using geographical data. This autonomously synchronizes all base stations to each other. Computer simulation and analysis results confirm the accurate and stable TDMA frame synchronization of all base stations even in fading environments.

This paper proposes a group demodulator that employs multi-symbol chirp Fourier transform to demodulate pulse shaped and time asynchronous signals without degradation; this is not possible with conventional group demodulators based on chirp Fourier transform. Computer simulation results show that the bit error rate degradation of the proposed group demodulator at BER=10-3 is less than 0.3dB even when a root Nyquist (α=0.5) filter is used as the transmission pulse shaping filter and the symbol timing offset between the desired channel and the chirp sweep is half the symbol period.