Personal communication systems using multiple hierarchical cellularoverlays

A personal communication system with multiple hierarchical cellular overlays is considered. The system can include a terrestrial segment and a space segment. The terrestrial trail segment, consisting of microcells and macrocells, provides high channel capacity by covering service areas with microcells. Overlaying macrocells cover spots that are difficult in radio propagation for microcells and provide overflow groups of channels for clusters of microcells. At the highest hierarchical level, communications satellites comprise a space segment. The satellite beams overlay clusters of terrestrial macrocells and provide primary access for satellite-only subscribers. Call attempts from cellular/satellite dual subscribers are first directed to the terrestrial cellular network, with satellites providing necessary overlay. At each level of the hierarchy, hand-off calls are given priority access to the channels. The mathematical structure is that of a multilayer hierarchical overflow system. An analytical model for teletraffic performance (including hand-off) is developed. Theoretical performance measures are calculated for users having different mobility characteristics. These show the carried traffic, traffic distribution, blocking, and forced termination probabilities     

Channel holding time distribution in public telephony systems (PAMRand PCS)

This paper examines the channel holding time probability distribution in different public telephony systems. The systems analyzed are public access mobile radio under its two possible operation modes (message and transmission trunking) and personal communications systems. The three statistical studies are based on a fully empirical approach and make use of data acquired from actual working systems that the authors considered to be sufficiently representative. Although this empirical approach is obviously highly dependent on the environment, it eliminates the need to assume a number of hypotheses present in all analytical and simulation studies. The results achieved through this approach capture effects that others overlook and enrich the existing literature on the subject, and should be useful for teletraffic engineering mobile systems     

Dynamic Reservation Multiple Access (DRMA): A new multiple access scheme for Personal Communication System (PCS)

To improve the spectrum efficiency of integrated voice and data services in Personal Communication System (PCS), several reservation-type multiple access schemes, such as Packet Reservation Multiple Access (PRMA), Dynamic Time Division Multiple Access (D-TDMA), Resource Auction Multiple Access (RAMA), etc., have been proposed. PRMA uses the data packet itself to make a channel reservation, and is inefficient in that each unsuccessful reservation wastes one slot. However, it does not have a fixed reservation overhead and offers shorter access delay. On the other hand, fixed reservation overhead is unavoidable in both RAMA and D-TDMA. Compared to D-TDMA and PRMA, RAMA is superior in the sense that its slot assignment is independent of the traffic load. But its implementation is difficult. With these observations, a new reservation protocol, called Dynamic Reservation Multiple Access (DRMA), is proposed in this paper. With this new protocol, the success probability of channel access is greatly improved at the expense of slightly increased system complexity. It solves the problem of inefficiency in PRMA, but without introducing the fixed reservation overhead as in D-TDMA and RAMA. In addition, it is more suited to the dynamic behavior of the integrated traffic because there is no fixed boundary between voice and data slots (which is mandatory in D-TDMA and RAMA). Our numerical results indicate that its performance is superior to the existing reservation protocols, especially in the integrated traffic scenario. Moreover, the soft capacity feature is exhibited when the traffic load increases.     

Continuous-access guided communication (CAGC) for ground-transportation systems

Electromagnetic open-guiding structures, or surface waveguides, for continuous-access guided communication (CAGC) and obstacle detection ("guided radar"), are described for use in ground transportation, such as railways, highways, and more advanced guided systems. The experimental and theoretical work at Queen's University on surface-wave devices and their application to obstacle detection are reviewed in detail. It is concluded that there is considerable promise in these techniques and that obstacle detection, in particular, deserves much more attention than it appears to have received.     

Comparison of signaling loads for PCS systems

We present a comparison of the control signaling load of two vastly different architectures for providing personal communication services (PCSs). One architecture is based on current cellular networks. The other architecture, called the wireless distributed call processing architecture (WDCPA), distributes processing from the mobile switching centers and cell sites and executes new procedures for tracking mobile users and locating mobile users to deliver calls. We determine the signaling load generated within each system to support mobility management and call control based on standard assumptions about the operating parameters of a cellular network. Our results show that, when compared to current cellular systems, for simple single-connection services, WDCPA has marginally reduced cross-network signaling loads. For multiconnection calls, WDCPA incurs 35% less total signaling load for mobility management, has reduced cross-network signaling load for mobility management by up to 65%, and depending on the user model (e.g., data or telecommunication), has reduced total cross-network signaling load, including procedures for call/connection and mobility management, by up to 55% when compared to current cellular systems, while more flexibly supporting services     

Design trade-offs in cellular/PCS systems

With the increasing demand for all kinds of wireless access services, including cellular/PCS, wireless local loop, and broadband access, the system architects will have opportunities to design new communication systems, not necessarily based on existing wireless standards. In the design of wireless communication systems, there are usually multiple objectives such as low cost, small size, high reliability, and large capacity. The system architect would need to study the trade-offs among different combinations of modulation, coding, multiple access, and antenna techniques to determine the best design. In this tutorial we focus on the trade-offs between user bandwidth and multi-user interference in order to maximize the system capacity. The design trade-offs are depicted on a B-γ₀ plane. Where B is the user bandwidth and γ₀ is the carrier-to-interference ratio (C/I). For F/TDMA and CDMA systems, the author first shows that the contours of equal system capacity are straight lines with different slope's depending on the propagation environment, and the capacity decreases for increasing B and γ₀. Then as feasible solutions, the author plots the different combinations of modulation and coding with diversity to satisfy a certain quality of service in a multipath environment. The best design is obtained by moving a line with a certain slope from the lower left corner in the B-γ₀ plane until it touches the first feasible solution. From these plots we can see that, for example, while 1/2-rate channel coding is the best choice for F/TDMA systems, 1/3-rate is better for CDMA systems     

Adaptive region-based location management for PCS systems

The personal communications services (PCSs) systems can provide ubiquitous and customized services. The key issue, which affects the performance of the whole system, is the location management. We propose a region-based location strategy by taking advantage of the user's movement behavior to improve the performance of the conventional systems. Each mobile user is associated with a set of regions, which are derived from the user's movement patterns. The registration processes in the same region can be eliminated such that the cost of location management can be significantly reduced. Several design issues are studied by considering the workload balance and the call-to-mobility ratio for a user. The proposed strategy can be dynamically adjusted based on different system parameters and user behavior. A performance analysis on the signaling cost and the database access cost is given to justify the benefits of this approach     

Bandwidth limits of nonlinear (soliton) optical communication systems

We have shown that interactions between pulses can lead to a significant reduction of the bandwidth of nonlinear systems. The inclusion of loss is essential and implies that solitons must be launched with a separation of at least 10 times their pulse width for short systems of ~ 30 km and even more for longer systems.     

Quantum communication systems (Corresp.)

A mathematical formulation of the notion of an idealized continuous time quantum-mechanical communication system is given, using ideas from stochastic processes and from quantum field theory. The formalism is developed at an abstract level and illustrated by constructing a model of a coherent quantum communication system.     

LeZi-Update: An Information-Theoretic Framework for Personal Mobility Tracking in PCS Networks

The complexity of the mobility tracking problem in a cellular environment has been characterized under an information-theoretic framework. Shannon's entropy measure is identified as a basis for comparing user mobility models. By building and maintaining a dictionary of individual user's path updates (as opposed to the widely used location updates), the proposed adaptive on-line algorithm can learn subscribers' profiles. This technique evolves out of the concepts of lossless compression. The compressibility of the variable-to-fixed length encoding of the acclaimed Lempel–Ziv family of algorithms reduces the update cost, whereas their built-in predictive power can be effectively used to reduce paging cost.     

Tensor space-time (TST) coding for MIMO wireless communication systems

In this paper, we propose a tensor space-time (TST) coding for multiple-input multiple-output (MIMO) wireless communication systems. The originality of TST coding is that it allows spreading and multiplexing the transmitted symbols, belonging to R data streams, in both space (antennas) and time (chips and blocks) domains, owing the use of two (stream- and antenna-to-block) allocation matrices. This TST coding is defined in terms of a third-order code tensor admitting transmit antenna, data stream and chip as modes. Assuming flat Rayleigh fading propagation channels, the signals received by K receive antennas during P time blocks, composed of N symbol periods each, with J chips per symbol, form a fourth-order tensor that satisfies a new constrained tensor model, called a PARATUCK-(2,4) model. Conditions for identifiability and uniqueness of this model are established, and a performance analysis of TST coding is made, before presenting a blind receiver for joint channel estimation and symbol recovery. Finally, some simulation results are provided to evaluate the performance of this receiver.     

空时码及其在移动通信中的应用

总结了空时码的分类，分析了各类空时码的性能特点和在移动通信中的应用，并对其研究方向和发展前景进行了探讨。     

Optical fiber feeder for microcellular mobile communication systems(H-O15)

The authors investigate the feasibility of using an optical fiber feeder for microcellular mobile communication systems. The optical feeder enables compact and low-cost base stations, easy radio channel control, and flexible mobile communication systems. Basic transmission characteristics were investigated through optical transmission experiments. Using these results, it is estimated that the optical feeder can transmit 880 telephone channels for digital TDM systems and 2000 channels for analog FDM systems through 20 km of optical fiber. Furthermore, two kinds of novel techniques that enlarge dynamic range of the optical feeder are reported     

PACS: personal access communications systems an alternativetechnology for PCS

The personal access communications system (PACS) is an American National Standards Institute common air interface standard developed for the 1.9 GHz PCS band in the United States. The PACS uses frequency division duplexing technology and is optimized to support low-mobility pedestrian outdoor usage and wireless local loop applications in a medium-range environment. PACS-Unlicensed B (PACS-UB) is a version of PACS using time division duplexing. The PACS-UB has been optimized for private, indoor wireless PBX applications and cordless telephony. Both modes of operation are supported using the same portable hardware and the same signaling protocol     

DSD (double soft decision) concatenated FEC scheme in mobilesatellite communication systems

In order to realize a higher-code-gain forward error correction scheme in mobile satellite communication systems, a novel concatenated coding scheme employing soft decision decoding for not only inner codes but also outer codes (double soft decision, or DSD, concatenated forward error correction scheme) is proposed. Soft-decision outer decoding can improve the bit error probability of inner decoded data. In this scheme, likelihood information from an inner Viterbi decoder is used in the decoding of outer codes. A technique using the path memory circuit status 1.0 ratio for likelihood information is proposed, and is shown to be the most reliable even though it requires the simplest hardware among the alternative methods. A computer simulation clarifies that the DSD scheme improves Pe performance to one-third of that of the conventional hard-decision outer decoding. Moreover, to reduce the interleaving delay time in fading channels or inner decoded data of concatenated codes, a parallel forward error correction scheme is proposed     

Binary single-sideband phase-modulated communication systems (Corresp.)

Single-sideband phase modulation (SSBPM), in which a signal is simultaneously phase- and amplitude-modulated by a signal and its Hilbert transform, is shown to be suboptimum for binary signaling in white Gaussian noise. An alternative single-sideband technique based on the properties of binary suppressed-carrier phase modulation is proposed and shown to give performance equivalent to the double-sideband version.