Broadband CDMA for personal communications systems

An application of decentralized location registration (DLR) information storage method has been investigated for multimedia services through mobile communication networks. Various kinds of multimedia services will be introduced in mobile communication networks in quite near future. Since a service area of such mobile communication system can be nationwide or even worldwide, information delivery cost to each mobile unit will be increased because the distances between a central storage office and each unit is large and there may be too many units communicating at the same time. To minimize the cost and increase the network efficiency, it is possible to apply the DLR-information storage method, which the author has proposed for personal communication networks, to this field. The author demonstrates an easier authentication method by adopting a decentralized mobile control center which memorizes the communication history of each personal communication unit.

An ubiquitous network for multimedia personal communications (Personal Communications Network (PCN)) with small, individual low-cost terminals is one of the most ambitious worldwide projects for the 21st century that are being pursued nowadays. In the development of such PCN, Geostationary, Medium, and Low Earth Orbiting (GEO, MEO, LEO) satellite constellations will play a fundamental role to provide worldwide coverage for most services required by the end-user. The characteristics of efficiency and flexibility inherently required by that scenario suggest, amidst other possibilities, to take into special consideration a radio interface based on code division multiple access (CDMA) to ensure, in addition to the features mentioned above, a sufficient grade of power and spectral efficiency of the relevant satellite radio link. The aim of this paper is a review of the current status of those issues in the field of satellite CDMA transmission systems design that, in our opinion, appear fundamental to the successful operation of an efficient PCN. In particular, we survey the techniques for multiplexing, coding and transmission of direct-sequence spread spectrum (DS/SS) signals, and we touch upon the techniques for the minimization of the self-noise effect, and the related topics of power-control and multiuser detection. We also shortly address in this respect some technological aspects related to an efficient modem design via digital signal processing techniques. The final part of the paper deals more specifically with some typical issues of satellite transmission, namely the minimization of the detrimental effects of the nonlinear satellite transponder and of multipath propagation; the applicability of diversity reception to a multisatellite network is also addressed as possible means of performance boost.

Field tests were conducted to test whether a broadband code division multiple access (CDMA) network can be overlayed on the 1850-1990-MHz band which will not interfere with existing FSM (fixed site microwave) users of that band and will itself function properly. The test demonstrated that, on the average, even without the use of a notch filter and without voice activity, there will be no significant interference to microwave receivers under EIA specification 10E when 50 users are located in single cells of diameter 1200 ft. The CDMA system functioned with excellent voice quality at mobile power levels of 100 mu W or less, and the microwave signals caused no significant effect on performance. Additionally, the tests obtained data on propagation conditions in the 1850-1990-MHz band in urban, rural, suburban and in-building areas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Star 16QAM is a modulation method that transmits 4 bits per symbol and has the advantage that it may be differentially encoded and detected. It is very robust to fast multiplicative Rayleigh fading and is suitable for mobile telephone systems and personal communication networks. The main contribution of this paper is the derivation and bit error probability simulation of the maximum likelihood differential detector using phase differences and amplitude ratios from L diversity branches for bit decisions. As a comparison, much simpler previously known post detection combining techniques are generalized for star 16QAM and optimized. The bit error probability is simulated for both diversity detectors on a multiplicative Rayleigh fading channel with additive white Gaussian noise. It is found that the bit error probability of the ML detector may also be obtained by the simple combining detector. This is also true for the error floor due to the maximum Doppler frequency. The diversity gain is almost 8 dB, measured in signal to noise ratio per diversity branch, at a bit error probability of 1 percent. The diversity detector can sustain an almost 3 times larger Doppler frequency again at a bit error probability of 1 percent. We also show that star 16QAM offers, at most, 3 subchannels with different bit error probabilities. >

The knowledge of channel behaviour is of paramount importance in order to engineer the various sub-systems of a wireless communication system. The requirement to understand the signal propagation mechanisms, and the ability to model them, is even greater for the frequencies at which satellite-based mobile and personal communication networks are being planned. Satellite-mobile link quality and the availability of such services, to a great extent, will be determined by the propagation channel characteristics. The propagation channel characteristics are believed to be most significantly dependent upon the mobile surrounding environment. Signal amplitude variations of the order of several dBs may be experienced mainly due to the obstruction of the line-of-sight (LOS) path between a satellite and a mobile over a relatively short duration of time. This effect is known as ‘shadowing’. Due to generally small dimensions of a mobile terminal, and therefore less or no antenna directivity, signal reception over multiple paths is another propagation degradation called ‘multipath’ reception. The dynamic nature of the satellite-mobile link results due to the constantly changing phase relationships of various incoming component signals at the terminal. Multipath is essentially cause of faster channel variations. In general, the depth of channel fading is dominated by the shadowing whilst the rate of the fading process (also called fading bandwidth) depends upon multipath.

A hybrid (reservation/random) medium access control protocol based on code division multiple access is described and analyzed under multimedia traffic load. The protocol meets the quality of service requirements of the different users and applications by following proper reservation policies and through a multi-priority mechanism which is embedded in its collision resolution algorithm. The priority mechanism is implemented and controlled explicitly by the users and without any involvement from the network. This makes the allocation of priority transparent to the network infrastructure and adds to the simplicity and practical value of the proposed scheme. The evaluation shows that the protocol is able to achieve high levels of utilization and is capable of supporting relatively large numbers of video/voice users and relatively high volumes of data traffic.

Error correcting codes are used in various processing systems such as computers, control systems, optical disks, audio recordings, space communications and particularly land mobile radio communications. A unique feature of the mobile radio communication system is the fact that the received signal envelope varies constantly due to the motion of the vehicle and the multipath propagation. In addition, the demand for services such as cellular telephone, paging, personal communication network, and automatic vehicle location systems, etc., is rapidly increased. As a result, these disturbances cause transmission imparities in both random and burst errors and result in degradation of system performance, i.e. increase of system bit error rate (BER) [1].

Personal Communication Networks (PCNs) have become an important filed of activity and they are expected to play a fundamental role in next-generation telecommunication systems. In particular, the emerging personal communication services, such as portable computing, paging, personal e-mail, etc. have led to the need of an efficient integration of voice and data traffic in a same PCN by means of a suitable multiple-access scheme. This paper considers stability and optimization issues for the Packet Reservation Multiple Access (PRMA) protocol used for integrating voice and burst data traffic in a PCN. An important result here devised is that the optimized PRMA protocol permits to be achieved good performance even under heavy traffic load conditions.

The personal networks of listeners and nonlisteners to an entertainment-education radio soap opera in Tanzania are examined to determine the effects of interpersonal discussion of the soap opera's educational themes of family planning and HIV prevention. Listeners are more likely to discuss these two educational issues in their personal communication networks and are also more likely to have other listeners to the radio program in their personal communication networks. Respondents demonstrate a relatively high degree of homophily with their network partners and are more likely to discuss matters arising from the radio program with their network partners who are of similar tribal membership, religious affiliation, and gender, and those who are equally or more highly educated than themselves.

We propose an efficient location management algorithm for broadband personal communication networks (PCNs) which reduces the complexity of network signaling and delay due to database access when locating a portable station (PS). Previous works on updating and search algorithms for personal communications have concentrated on the access delay due to signaling network traffic only. But, with the advances in fiber optic technology, it will be possible to provide the capacity of signaling network on the order of several Mbps in broadband PCNs. Thus it may be more important to simplify the signaling procedure and reduce the number of database accesses for mobility management at the cost of some increase of signaling traffic. In the proposed algorithm, we first remove all visitor location registers (VLRs) in order to achieve the simplicity of signaling procedure. Thus, only home databases for mobility management are distributed in a global network, and each database keeps only the current locations of PSs initially registered in its management area. It can solve the problem of requiring an impractically large database in a centralized database structure by distributing home location registers (HLRs) while maintaining the simplicity of mobility management and reducing database loads. This algorithm has a simple signaling procedure, and reduces database operations when compared to hierarchical algorithms as network switching hierarchy increases or relocation and calling rate increase.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An advanced telecommunications system is provided for the recognizing of spoken commands over a cellular telephone (15), satellite telephone (14), or personal communications network (16). In the cellular application, for example, a Speech Recognition System (20) interconnects either internally with or as an external peripheral to a cellular telecommunications switch (12). The Speech Recognition System (20) includes an administrative subsystem (21), a call processing subsystem (23), a speaker-dependent recognition subsystem (25), a speaker-independent recognition subsystem (27), and a data storage subsystem (29). Pre-recorded instructional messages are stored in the memory of the call processing subsystem (23) for instructing a user on his or her progress in using the system. The speaker-independent recognition subsystem (27) allows the user to interact with the system employing non-user specific functions. User specific functions are controlled with the speaker-dependent recognition subsystem (25). User specific attributes collected by the recognition subsystems are stored in the data storage subsystem (29).

This paper presents a discussion of system design issues related to the development of next-generation multimedia personal communication networks (PCN). It is proposed that the baseline definition of emerging PCN systems be broadened to provide multimedia transport capabilities qualitatively similar to those offered by BISDN/ATM. A number of system-level design and technology selection issues are discussed. Specific topics considered include: multimedia PCN traffic handling requirements, service cost targets, system design criteria, choice of packet switching vs. circuit switching, strategies for ATM compatibility, media access control (MAC) selection, etc. The presentation is concluded with an outline of a dynamic TDMA based multimedia PCN system architecture consistent with the preceding discussion. Simulation based performance evaluation results are also given for such a dynamic TDMA PCN channel operating in example mixed voice/data traffic scenarios.

The microcellular mobile radio systems are widely utilized in the third generation of digital mobile communication networks, and will certainly be applied in the forthcoming personal communication networks as well. However, we still have no strict definition so far for the so-called in the urban wireless communication environment. Roughly speaking, the microcell implies such a region in which the radiated signal power is relatively small (typically around 10 mW), the height of the transmitting antenna is low (usually suspended at a lamp-pole in a street). Therefore the covering area of a base-station in a microcell system is much smaller than that of a base-station in a macrocell system. It is naturally understandable that the surrounding buildings will definitely affect the radiation wave coverage of a microcellular base-station to a great extent. We discuss the problem of using microcell systems from a new point of view. The point is that the cellular areas must be miniaturized in order to ensure the electromagnetic compatibility both in the internal and the external communication network. To support this point, we discuss a number of technical and economical problems concerning the miniaturization of the mobile communication cells.

Integrated Multimedia Personal Communications with Asymmetric Services for Mobile Users in Cellular Systems

Combine federated learning with the mobile network a good opportunity for the introduction of AI technology research and application in the mobile communication network.This article proposes a kind of the mobile network architecture based on FL to promote the integration of FL technologies with mobile communication network and to meet the joint modelling needs of users, operators, and industries. And points out some key technologies of the mobile network to illustrate how the mobile network to support FL working. Meanwhile, proposes some use cases to illustrate what possible application scenarios and values, if the FL technology is introduced into the mobile communication network.