Performance analysis of microcellular mobile radio systems with shadowed cochannel interferers

A study is presented of microcellular mobile radio systems where the desired signal has Rician statistics and cochannel interferers experience lognormal shadowing as well as Rayleigh fading. This implies a Rician/Rayleigh-plus-lognormal microcell interference model. The probability density function of the signal-to-interference ratio is derived and used to evaluate the performance of microcellular systems in terms of the outage probability.<>     

Spectrum efficiency of GMSK land mobile radio

Gaussian-filtered minimum-shift keying (GMSK) is a constant envelope and narrow-band modulation suitable for power- and band-limited digital radio communication. From the viewpoint of efficient spectrum use by land mobile radio, geographical reuse of cochannels as well as power spectrum compactness are desired. The output power spectrum of GMSK modulation can be made compact, at a sacrifice of co-channel interference protection. Parameters for optimizing GMSK are determined maintaining a compromise between co-channel reuse and power spectrum compactness.     

Spectrum efficiency of a frequency-hopped-DPSK spread-spectrum mobile radio system

The spectrum efficiency (bits/s per unit bandwidth) of a frequency-hopped-DPSK spread-spectrum modulation technique proposed for use in urban mobile radio systems is estimated. The analysis is based on simple models for the factors influencing system performance, and requires no computer simulation. It permits straightforward evaluation of spectrum efficiency over a broad range of system parameters. For an isolated service area (cell) with no propagation impairments, the efficiency is 0.12 at a bit error rate of 10^-3. When interference from nearby cells is considered (assuming centrally located base stations with omni-directional antennas), the efficiency falls to 0.03 - 0.06, depending on how much performance degradation can be tolerated near the cell boundaries. Finally, the effects of multipath (Rayleigh) fading reduce system efficiency to 0.02 - 0.05.     

Spectrum efficiency limits in mobile cellular systems

In cellular mobile radio systems using coded modulations, the spectrum efficiency of the system is related to the cutoff rate and the cluster size. We evaluate the cutoff rate for M-ary QAM considering a coherent detection and a memoryless flat fading channel. Simulation results relate the cluster size to the signal-to-noise ratio and to the cutoff rate. We present the spectrum efficiency of the system as a function of the cutoff rate and show its limits in the classical cellular system. We apply the same procedure to examine the performance of systems using directional antennas with and without sectorization of the original cell surface. With our proposed representation, we can always determine the optimum spectrum efficiency of the modulation that maximizes the spectrum efficiencies of the different systems     

Area spectral efficiency of cellular mobile radio systems

A general analytical framework quantifying the spectral efficiency of cellular systems with variable-rate transmission is introduced. This efficiency, the area spectral efficiency, defines the sum of the maximum average data rates per unit bandwidth per unit area supported by a cell's base station. Expressions for this efficiency as a function of the reuse distance for the worst and best case interference configurations are derived. Moreover, Monte Carlo simulations are developed to estimate the value of this efficiency for average interference conditions. Both fully loaded and partially loaded cellular systems are investigated. The effect of random user location is taken into account, and the impact of lognormal shadowing and Nakagami (1960) multipath fading is also studied     

Bit error probabilities of NCFSK and DPSK signals in microcellular mobile radio systems

Microcellular mobile radio systems are studied where the desired signal has Rician statistics and the cochannel interferers experience Rayleigh fading. The probability density function of the signal-to-interference ratio is derived and is used to obtain the bit error probabilities of noncoherent frequency shift-keying and differential phase shift-keying signals.<>     

Free access stack algorithms for microcellular radio systems

We evaluate the data traffic performance of a centralized packet access protocol for microcellular radio systems supporting both speech and data users. A time-slotted radio channel is assumed. Speech contention is decoupled from data contention to give speech priority over data. A free access stack algorithm is used for handling data contention. An out-slot access scheme is used in which the slots are divided into user-information transmission slots and contention slots for sending transmission requests. The contention slots are subdivided in minislots to improve the access capacity. The out-slot algorithm performances are compared with the performances of a previously proposed in-slot one in which all slots can be used for sending user information. A memoryless channel, with capture and errors, is considered. The effects of speech traffic on data performance are evaluated. Moreover, the paper presents a method for evaluating the packet error probability of a packet cellular system. This method is used for evaluating the proposed algorithm in a microcellular system. An access technique with coordinated operation among cochannel cells is studied. The effects of sectorization on data performances and protocol unfairness are investigated. Different frequency reuse factors are taken into consideration     

Spectrum efficiency of a frequency-hopped MFSK spread spectrum mobile radio system

The spectrum efficiency of a frequency-hopped multilevel frequency-shift keying (FH-MFSK) spread spectrum modulation technique proposed for use in mobile radio systems is evaluated. The analysis assumes randomly chosen address vectors, a perfect synchronization at the receiver, and noncoherent detection. With perfect transmission where the only degradation is due to mutual interference, the efficiency is 0.262, 0.295, and 0.345 at an average bit error rate of 10^-3for 1.64, 3.41, and 20 MHz bandwidth. However, with transmission impairments consisting of additive white Gaussian noise and frequency selective Rayleigh fading, which characterize the mobile radio channel, the efficiency depends on the average signal-to-noise ratio (SNR), and on the average bit error rate.     

Effect of cochannel interference on handover in microcellular mobile radio

The effect of cochannel interference on a fast handover algorithm for microcellular mobile radio systems is described. The presence of cochannel interference had only a marginal effect on the handover point when the microcell base stations were spaced by 300 m. Increasing the mobile speed increased the effective cell length.<>     

Closed-form expressions for the prediction of microcellular mobile radio propagation in urban environments

The paper derives two closed-form expressions for predicting microcellular mobile radio signal levels in urban street-grid environments. The results demonstrate that the two expressions are faster and more accurate than existing models and methods. Benefiting from physical optics and the conservation of energy, the two expressions are alternatives to available techniques such as ray tracing. The dielectric property (i.e., permittivity) of street buildings and other obstacles is essential to the ray tracing technique. However, there are no established, widely accepted techniques for selecting the permittivity in urban mobile environments, which varies in a wide range. Establishing a natural link between the received power after a street corner to the width of the street and the angle of incidence, our expressions show the possibility of making fast and accurate propagation predictions without having to use the permittivity.     

Security services for protecting radio mobile systems

The development of radio networks has brought the problem of security specifically related to mobility of terminals sharply into focus, and has created the need for radio network operators to implement new security functionalities. The security level of the analog radio mobile systems (the so-called “first generation ” systems was very low, and these systems were often exposed to massive fraud. The development of digital radio mobile systems (the so-called “second generation” systems: GSM, DECT,. allowed the systematic introduction of cryptology based protection mechanisms. Hence, for gsm networks for instance, the main fraud and confidentiality problems were taken into account at the design stage and a security architecture was implemented to provide security services to users and network operators. The third generation mobile telecommunication systems belonging to the imt- 2000 family (which are still under specification within standardisation bodies in particular within the 3gpp worldwide third generation partnership project) will, in the forthcoming years, provide a wide variety of services on a single terminal in a multi-environment (domestic, public, business), multi-operator, and multi-service provider context. Security will be based on second generation systems security functions that have proved to be needed and reliable, and shall be adapted and improved to resolve security threats underlying to new services supplied by third generation radio systems. This document presents examples of security solutions currently implemented for protecting second generation radio mobile systems against frauds and attacks and gives an overview of potential solutions for protecting future third generation radio mobile telecommunication systems.     

Network planning for third-generation mobile radio systems

The success of UMTS relies not only on the development of a flexible air interface, efficient coding techniques, and handset technology; it is equally important to design a system that can support the underlying technology and to interface with other networks     

Finite-source analysis of traffic on private mobile radio systems

Users of private mobile radio trunking systems often communicate in groups, queueing for a free channel if all channels are engaged. A finite-source queueing model is more appropriate than the infinite-source Erlang-C model. Performance equations, including the probability of delay exceeding a certain period, are derived     

Multiple radio zone plans in mobile radio systems

Multiple zone structure in a land mobile system seems to offer a flexibility in radio zone planning by using different interference distances conforming to the different system requirements in a system, thus improving the frequency utilization. A multiple zone structure can be formed by a tessellation of basic zone groups with an identical shape in parallel translation on a plane. To assure the possibility of the tessellation, two types of basic zone groups are investigated. One has several hexagonally shaped zones covered by an omnidirectional antenna beam from the zone center, while another is constructed as a subdivision of hexagons covered by a directive antenna beam. The former is expected to facilitate reduced interference distance between adjacent frequencies. An estimate of the latter type has shown better frequency economy than that in a conventional zone structure.     

Fiber optic microcellular radio

A distributed antenna system consisting of optical fiber connected canisters is proposed to replace or supplement the base station antennas required for cell splitting of growing cellular mobile radio systems. The end-to-end linear transmission of RF signal voltage can be maintained over the wide dynamic range of mobile radio. The technical feasibility of multiplexed subcarrier transmission using available lightwave components has been verified by signal-to-noise ratio and intermodulation distortion measurements. Measurements of a two-way audio link over both simulated and real radio paths have demonstrated the compatibility of a prototype lightwave transceiver, designed for the canister, with the existing base station and mobile equipment     

Outage probability and spectrum efficiency of cellular mobile radio systems with smart antennas

Relying on the distribution of noncentral multivariate F variates, we investigate the outage probability and spectrum efficiency performance of cellular systems with smart antennas. We consider interference-limited systems in which the number of interferers exceeds or is equal to the number of antenna elements, and we present closed-form expressions when the desired signal is subject to Rician-type fading and interfering signals exhibit Rayleigh-, or, more general Nakagami-type fading. When applicable, these new expressions are compared to those previously reported in the literature dealing with the performance of cellular systems without smart antenna capabilities and the performance of cellular systems with optimum combining when both the desired and interfering signals are subject to Rayleigh-type fading. Corresponding numerical results and plots are also provided and discussed.     

Outage analysis in mobile radio systems with generically correlatedlog-normal interferers

A novel methodology is proposed for computing the outage probability in mobile radio systems in the presence of log-normal shadowing. A relevant feature is that the proposed analysis assumes a general correlation for any pair of links. Various approaches are considered to compute the statistics of user signal-to-interference ratio (SIR), namely Schwartz and Yeh's method, Wilkinson's method, and Fenton's method. By a simple reformulation of the problem, these methods can be used to calculate in a straightforward way the parameters of the SIR. The accuracy of the methods is checked in a number of situations of interest. Moreover, when the same correlation is assigned to any pair of links, the novel analysis is more accurate than previously proposed approaches     

Dipole printed array antennas for mobile radio systems

Dipole array antennas realized on the basis of radiating modules in which strip dipoles are integrated with antenna balancers of a novel structure are described. Units with reduced overall dimensions and a reduced mass, which allow substantial simplification of the construction of array antennas for mobile radio systems, are proposed.     

Spectrum efficiency in cellular [radio]

The spectrum efficiency in cellular radio systems can be measured by a parameter that is called radio capacity. Using radio capacity, it is shown that splitting analog channels does not increase the spectrum efficiency in cellular radio systems, but that using digital cellular channels does. A simple evaluation method for judging spectrum efficiency in different digital systems is introduced. Also, several new concepts of spectrum efficiency in cellular radio systems are described     

Sigmoid-basis nonlinear power-control algorithm for mobile radio systems

Convergence speed and distributiveness are important properties of a power-control algorithm in order to evaluate its potential for use in cellular radio systems. Most of the power-control algorithms in literature are derived from numerical linear algebra or linear control theory and, consequently, are in linear form. This paper, on the other hand, proposes a (sigmoid-basis) nonlinear power-control algorithm that is fully distributed and first order. The algorithm is obtained by discretization of the differential equation forms of the algorithm shown to be stable in the case of a feasible system. It is shown to be quadratically convergent in the neighborhood of its fixed point. We carried out computational experiments on a code-division multiple-access system. The results indicate that our algorithm significantly enhances the convergence speed of power control in an estimation error-free scenario and is more robust against estimation errors as compared with the linear distributed power-control algorithm of Foschini and Miljanic as a reference algorithm. The proposed algorithm was also verified with an advanced dynamic system simulator.