This paper proposes the use, in integrated wireless systems, of the Reserved Idle Signal Multiple Access with Collision Resolution (R-ISMA/CR) protocol for applications in future multimedia mobile communications. It is applied to the integrated voice and data wireless system. Moreover, the consideration is made of the integrated voice and the low-bit video wireless system in R-ISMA/CR. To integrate video we employed not only a packed discard for video packets when the video packet delay is more than a threshold value, but also the connection packet (CP) technique for improving the channel utilization. Finally the integration of voice, data, and low-bit-video wireless system in R-ISMA/CR is considered. The performance are evaluated mainly by simulations.

Recently several dosimetric assessment procedures have been proposed to demonstrate the compliance of handheld mobile telecommuications equipment (MTE) with safety limits. However, for none of these procedures has an estimation of the overall uncertainty in assessing the maximum exposure been provided for a reasonable cross-section of potential users. This paper presents a setup and procedure based on a high-precision dosimetric scanner combined with a new phantom derived from an anatomical study. This allows the assessment of the maximum spatial peak SAR values occurring in approximately 90% of all MTE users, including children, with a precision of better than 25%. This setup and procedure therefore satisfies the requirements of the FCC, as well as those drafted by a CENELEC working group mandated by the European Union.

This paper proposes a new approach for distributing millimeter wave signals from a central location to micro-base-stations using optical fiber links. The links utilize two Mach-Zehnder external optical modulators (EOMs) to perform all optical down-conversion, eliminating the need for a local oscillator or laser diode in the micro-base-station. A simple model of the EOMs is developed to illustrate the principle of dual-EOM mixing. The characteristics of conversion loss and intermodulation are examined for two cases: where the EOMs are operated in the linear mode and where the local oscillator's EOM is biased as a frequency doubling modulator. Additionally, we examined the use of an optical amplifier to reduce conversion loss for these two cases. The measured conversion loss of the link was 82 dB, and we estimated this could be reduced to about 48 dB by employing an optical amplifier and a more efficient EOM for RF reception.

In this contribution an algorithm for joint detection in fast frequency hopping/multiple frequency shift keying (FFH/MFSK) multiple access (MA) systems is presented. The new algorithm - referred to as REC algorithm - evaluates ambiguities which occur during the decision process and iteratively reduces the number of candidate symbols. The REC algorithm is of low complexity, suitable for every addressing scheme, and effective for both an interference-only channel and a fading channel. For the interference-only channel the REC algorithm enables maximum likelihood (ML) joint detection with low computational effort.

The paper deals with the evaluation of performance of current cellular systems which are required to accommodate in an already operating system a wide range of new services, with different quality requirements (on delays, retransmission rates, etc.), and often characterised by a high burstiness (i. e. with relatively short traffic bursts, interleaved by comparatively long silence periods). To this end, an extension of packet communications is appealing for its inherent flexibility; standardisation of packet protocols for data transmission over idle GSM channels is in progress, and a similar service exploiting AMPS radio and network resources is already specified as Cellular Digital Packet Data. In both cases voice traffic retains a higher priority. The paper focuses on the evaluation of the effect of this additional traffic on existing voice traffic in a GSM Phase 2+ system. Although voice calls experience the same channel availability, their performance are worsened by the higher co-channel interference due to the higher average channel occupancy. This impairment cannot be tackled, as a matter of course, by increasing the re-use distance as this would affect the overall system capacity. The paper suggests the use of smart planning strategies capable to ease control of interference levels with a negligible impact on system complexity and signalling load.

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.

A new transmit permission control scheme applicable in multi-cell communication systems is proposed. In this scheme, by prohibiting the transmissions from the users with relatively high propagation loss to their connecting hub stations, level of multiple access interference is decreased, and hence throughput characteristics are improved. Moreover, we continue our discussion to propose two adaptive forms of the transmit permission control scheme, in which the prohibition condition becomes more intelligent by considering the level of the offered traffic loads to hub stations. These methods are utilized in a slotted Aloha random transmission of the spread spectrum packets, and on the uplinks of a low earth orbit satellite communication system as an example of the multi-cell systems. It is shown that the adaptive schemes exhibits significantly improved characteristics at all offered traffic loads in these systems.

This paper proposes an adaptive modulation system with a punctured convolutional code for land mobile communications to achieve high quality, high bit rate, and high spectral efficient data transmission in multipath fading environments. The proposed system adaptively controls the coding rate of the punctured convolutional code, symbol rate, and modulation level according to the instantaneous fading channel conditions. During good channel conditions, the modulation parameters are selected to increase the transmission rate as much as possible with satisfying a certain transmission quality. As channel conditions become worse, lower rate modulation parameters are applied or transmission is stopped. The performances in fading environments are evaluated theoretically and by computer simulations. The results show that the proposed system can realize higher quality transmission without the degradation in average bit rate compared to conventional adaptive modulation systems.

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.

Empirical studies confirm that the received radio signals in certain cellular systems are well modelled by Nakagami statistics. Therefore, performing relevant systems studies can be potentially useful to a system designer. A very useful statistical measure for characterizing the performance of a mobile radio system is the probability of outage, which describes the fraction of time that the signal-to-interference ratio (SIR) drops below some threshold. A more refined criterion for the outage is the failure to simultaneously obtain a sufficient SIR and a minimum power level for the desired signal. Thus, we derive new expressions for the probability of outage where a mobile unit receives a Nakagami desired signal and multiple, independent, cochannel Nakagami interferers. A salient feature of our results is that, unlike some previous studies, the outage expressions do not restrict the Nakagami fading parameter, m, to strictly integer values. Furthermore, since the received signals in mobile radio also experience log-normal shadowing, we analyze the case where the received signals are modelled by a composite of Nakagami and log-normal distributions. Outage probabilities are computed and graphically presented for several cases. The effect of specifying a minimum signal requirement for adequate reception is found to introduce a floor on the outage probability. It is also found that shadowing in macrocellular systems severely degrades the desired quality of service by increasing the reuse distance necessary for a given outage level.

This paper discusses advanced wireless communication technologies for achieving future high-speed mobile radios. Mainly, five technical fields are considered, that is, multi-level modulation for transmitting high-capacity information signal, advanced adaptive wireless system flexibly changing modulation level, symbol rate and traffic according to fading conditions, adaptive multicarrier system transmitting multimedia signals by changing the number of carrier according to the capacity of the signals, new CDMA techniques for mapping different bit rate services onto the same allocated bandwidth at the same time, and optical-linked microcellular communication system with millimeter wave air interface.

Mobile telecommunication is a rapidly growing market. Second generation systems such as GSM, DECT and ERMES, which are actually in an evolving status will be replaced by the third generation UMTS from the beginning of the next century on. While UMTS will allow data communication with up to 2Mbit/s, the fourth generation system MBS will provide up to 155Mbit/s. In several European R & D projects of the ESPRIT, DRIVE, COST and RACE programmes investigations concerning network planning, network operation, signalling, access techniques, security, terminal development and image and voice compression are carried out in order to create the scientific and technological bases for future UMTS and MBS. Some of these projects are described in more detail and an outlook toward future R & D activities is given. Finally some considerations are made concerning expectations of future services and questions concerning the development of wide band versus narrow band solutions are put.

Development of a large-scale mobile communications network (IMN: Intelligent Mobile communications Network), as an infrastructure integrating multimedia functions, is indispensable for the support of future mobile communication services aiming toward "personalization," "intelligence," and "multimedia services." This paper discusses the aims of mobile communications and the outline of network technology aspects of PDC (Personal Digital Cellular) network which is currently in service. In addition, the future prospect of mobile communication technologies is discussed with special focuses on the support of universal mobility, network architecture including mobile communications platform, and multimedia technologies in the transport and access systems.

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 reviews recent progress in adaptive signal processing techniques for digital mobile radio communications. In Radio Signal Processing (RSP) , digital signal processing is becoming more important because it makes it relatively easy to develop sophisticated adaptive processing techniques, Adaptive signal processing is especially important for carrier signal processing in RSP. Its main objective is to realize optimal or near-optimal radio signal transmission. Application environments of adaptive signal processing in mobile radio are clarified. Adaptive equalization is discussed in detail with the focus on adaptive MLSE based on the blind algorithm. Demodulation performance examples obtained by simulations and experiments are introduced, which demonstrates the recent advances in this field. Next, new trends in adaptive array processing, interference cancelling, and orthogonalization processing are reviewed. Finally, the three automatic calibration techniques that are based on adaptive signal processing are described for realizing high precision transmission devices.

This paper proposes a new adaptive Interference Cancelling Equalizer (ICE) with a blind algorithm. From a received signal, ICE not only eliminates inter-symbol interference, but also cancels co-channel interference. Blind ICE can operate well even if training signals for the interference are unknown. First, training signal conditions for applying blind ICE are considered. Next, a theoretical derivation for blind ICE is developed in detail by applying the maximum likelihood estimation theory. It is shown that RLS-MLSE with diversity, which is derived for mobile radio equalizers, is also effective for blind ICE. Computer simulations demonstrate the 40kb/s QDPSK transmission performance of Blind ICE as a blind canceller with two branch diversity reception under Rayleigh fading in a single interference environment. The simulations assume synchronous training; the canceller is trained for the desired signal but not for the interference signals. Blind ICE can be successfully achieved at more than -10dB CIR values when average Eb/N0 is 15dB and a maximum Doppler frequency is 40Hz.

The performance of selection diversity combined with decision feedback equalizer for reception of TDMA carriers is investigated in this paper. The second generation digital land mobile communication systems standardized in the U.S., Japan, and Europe employ TDMA carriers at transmission bit rates up to several hundreds kbit/s. In order to provide higher quality of mobile communications services to the user with employing TDMA carriers, the systems would require both diversity and equalization techniques to combat attenuation of received signal power level due to Rayleigh fading and intersymbol interference resulting from time-variant multipath fading, respectively. This paper proposes a novel integration method of selection diversity and decision feedback equalization techniques which provides the better bit error rate performance than that for the conventional selection diversity method with decision feedback equalizer. The feature of proposed method is that selection diversity and decision feedback equalization techniques are integrated so as to interwork each other. We call the proposed method by the Decision Feedback Diversity with Decision Feedback Equalizer. The detailed algorithm of the proposed method is first presented, and then the system parameters for the method are evaluated based on the computer simulation results. Finally the computer simulation results for the performance of the proposed method are presented and compared to those for the conventional Selection Diversity with Decision Feedback Equalizer and the conventional Dual Diversity Combining and Equalization method under the typical mobile radio environments, in order to demonstrate the validity of the proposed method.

The paper proposes a new multicarrier 16QAM system for high-quality and high-bit-rate transmission with high spectral efficiency in land mobile radio communications. The proposed system uses a multicarrier transmission scheme to provide immunity against frequency-selective fading distortion. It also uses pilot-symbol-aided 16QAM to increase spectral efficiency, and it combines space diversity and FEC with maximum likelihood decoding to improve the bit error rate (BER) performance. Computer simulation shows that a BER of less than 10-4 is obtained over frequency-selective fading channels with rms delay spread of less than 5.4µs. Using a bandwidth of 200kHz the proposed system can achieve high-quality transmission with a total information rate of 256kbit/s.

In this paper we present a new tracking scheme using two tracking modes which are based on the concept of Delay Lock Loop (DLL). Under the multipath fading channels, a conventional DLL has problems of jitter performance degradation, lock-off and delay offset. It is necessary to solve these problems, because mobile communications have increased drastically. We propose the combination of a coarse tracking mode and a fine tracking mode. The former mode is employed for reducing the possibility of losing lock, the latter mode is used for suppressing the jitter of delay error and the delay offset in the presence of multipath fading. The both modes utilize the power of delay paths shown in the auto-correlation function of the received signal at the DLL. Computer simulation results show that our proposed scheme is extremely useful comparing with a conventional scheme over the multipath fading channels.

This paper analyzes the performance of the capacity controlled radio system under a frequency selective fading environment. This system controls the number of modulation levels according to the number of active subscribers. In the analysis, we consider the capacity controlled system either with or without adaptive equalizer. As the results of analysis, it is clarified that the system is superior to the conventional fixed capacity system, and can be considered as a good countermeasure for multi-path fading. And it is found that there exists a synergistic effect due to capacity controlling and adaptive equalizing.