Comments on “Teletraffic model and performance analysis forcellular mobile radio telephone systems with prioritized andnonprioritized handoff procedures”

Hong and Rappaport (see Proc. Inst. Electr. Eng., vol.136, pt.I, no.5, p.339-46, 1989) considered a handoff scheme for cellular systems, where priority is given to handoff calls in channel assignment and a queue of handoff calls is allowed. This paper points out and corrects their critical error in getting some performance measures for the scheme. We also discuss the effects of our correction on the related results in their paper and in the paper of Pavlidou (see IEEE Trans. Commun., vol.42, no.2/3/4, p.848-53, 1994)     

Efficient handoff policy without guard channels for mobile radio telephone systems

Presented in this letter is a prioritised pushout handoff policy without guard channels for increasing the total grade of service (GOS) in a mobile radio telephone system. Blocking probability and waiting time distribution for each call are obtained, and a boundary for two handoff policies between with and without guard channels is found.<>     

Traffic model for third generation cellular mobile telecommunication systems

Traffic analysis for third generation mobile telecommunication systems should take into account a variety of services (e.g., voice, data, video) and environments (private, public outdoor, public indoor) as well as the user mobility behavior. The analytical traffic model presented in this paper incorporates all the above mentioned features. The model utilizes a set of simplifying assumptions regarding the distribution of certain random time intervals (e.g., call duration and cell residence time) and the handover arrival process. The core of the model focuses on the estimation of the cell border crossing rate and the time it takes a busy mobile user to leave a cell area. This allows for the estimation of the handover rate and the call duration within a cell, which in turn, utilizing an iterative method, allows for the calculation of the offered traffic load per cell. The major advantages of the model are: (a) the simple closed form solutions, (b) its independence from the applied radio resource management scheme, and (c) its accuracy. The latter is validated via a simulation tool, which accommodates different cell-layout scenarios over a geographical area, representing a typical city center, modeled as a Manhattan grid.     

Teletraffic performance evaluation of microcellular personalcommunication networks (PCN's) with prioritized handoff procedures

Evaluates four handoff priority-oriented channel allocation schemes. These give priority to handoff calls by reserving channels exclusively for handoff calls. The measurement-based handover channel adaptive reassignment scheme (MHAR-A) exclusively uses reserved handover channels for newly originated calls if a certain criterion is satisfied. All four schemes studied differ from the conventional guard channel-based handover priority-oriented channel allocation scheme. To study the schemes, a personal communication network (PCN) based on city street microcells is considered. A teletraffic simulation model accommodating a fast moving vehicle is developed, and the performance parameters are obtained. The performances of all four schemes are compared with the nonpriority scheme and the conventional guard channel-based handover priority-oriented channel allocation scheme. It was found that some of the channel allocation algorithms studied improved the teletraffic capacity over the nonpriority and the conventional guard case. Also, the probability of new call blocking and carried traffic was improved for three of the schemes when compared to the conventional guard scheme. The MHAR-A scheme did not perform up to expectation. Nevertheless, it can be used to finely control the communication service quality equivalent to the control obtained by varying the number of handoff channels in a fraction of one. Increasing the number of reserved handover channels in fraction of one can never be achieved in the conventional guard channel-based handover priority-oriented channel allocation scheme     

A model for analyzing handoff algorithms [cellular radio]

A model for analyzing the performance of handoff algorithms based on signal strength measurements made by mobile stations in a lognormal fading environment is presented. This model enables one to evaluate the effect of averaging the hysteresis on the handoff process. Handoffs are related to level crossings of the difference between the received signal strengths from two base stations. The algorithm performance is derived by modeling the level crossings as Poisson processes with time-varying rate functions. The model is seen to yield results that agree with simulations over the range of algorithm parameters of practical interest. These results can be used to determine the averaging interval and hysteresis level that achieve the optimum tradeoff between the number of unnecessary handoffs and the delay in handing off     

Capacity of cellular mobile radio systems

A lower bound to the Shannon capacity of the uplink channel of a cellular system, with perfect channel state information (CSI) at the receiver, is evaluated against the reuse distance and the level of shadowing affecting the interfering signals. Capacity is normalised to the covered area and expressed in bit/s/Hz/unit area     

UHF television interference associated with cellular mobile telephone systems

An investigation is made into two types of interference which may occur between UHF television and 850 MHz cellular mobile telephone systems: 1) ITV--interference to the cellular mobile telephone receivers, created by a UHF TV transmitter; 2) TVI--interference to the UHF TV receiver, created by the cellular system mobile transmitters. In the case of ITV it has been determined that TV transmitters operating on TV channels 65 through 69 may produce third-order intermodulation, within a radius of about 0.5 mi, to certain telephone channels assigned to mobiles operating in a cellular system fringe area. A judicious choice of telephone channel assignments would mitigate this type of degradation. Alternatively, in the case of TVI, it is shown that within a minimum grade B television service area, it is possible for cellular mobile telephones to at times produce image interference to present-day UHF TV receivers tuned to channels 58 through 61. However, because of cellular telephone subscriber density and channel position (and loading) the probability of interference is expected to be low. An increase of TV receiver image rejection by 20 dB would essentially eliminate all likelihood of this interference.     

Elements of cellular mobile radio systems

A major concern in a cellular mobile radio system is the co-channel interference. Therefore, the reduction of co-channel interference becomes a main thrust for the system design engineers. We use the co-channel interference reduction factor as a design criterion and predict the signal-to-interference (S/I) ratios in different system configurations. The handoff mechanism and algorithmic considerations, the traffic capacity and procedure for splitting cells, and the near-end-to-far-end ratio interference and reduction are the elements described.     

The error performance of CD900-like cellular mobile radio systems

The symbol error performance of CD900-like digital cellular mobile radio systems over narrowband and urban wideband transmission channels was investigated. The basic performance is presented for Gaussian, flat-fading Rayleigh, and log-normal channels in the presence of selection and ratio combining space diversity schemes. For wideband channels having more than one resolvable fading path, a CD900-like system without diversity reception suffers from large residual symbol error probabilities P_R(≈10^-1). The introduction of adaptive correlation diversity (ACD) mitigates the effects of multipath, yielding a P_R of 6×10^-5. Although this P_R value is relatively low, the probability of symbol error (P_e) versus signal-to-noise ratio (SNR) is significantly poorer than for the Gaussian channel. By combining the ACD scheme with space diversity, the P_R is eliminated by P_e >10^-5, and the channel SNR is within 5 dB of the Gaussian channel performance when P_e is 10^-10     

The performance enhancement of multibeam adaptive base-stationantennas for cellular land mobile radio systems

The problem of meeting the proliferating demands for mobile telephony within the confinement of the limited radio spectrum allocated to these services is addressed. A multiple-beam adaptive base-station antenna is proposed as a major system component in an attempt to solve this problem. The approach is demonstrated by employing an antenna array capable of resolving the angular distribution of the mobile users as seen at the base-station site, and then using this information to direct beams toward either lone mobiles, or groupings of mobiles, for both transmit and receive modes of operation. The energy associated with each mobile is thus confined within the addressed volume, greatly reducing the amount of cochannel interference experienced from and by neighboring cochannel cells. To ascertain the benefits of such an antenna, the conventional and proposed antenna systems are modeled in a typical mobile radio environment. For a given performance criterion, the theoretical results indicate that a significant increase in the spectral efficiency, or capacity, of the network is obtainable with the proposed antenna     

Traffic engineering of combined mobile telephone and dispatch systems

If a server group carrying short-holding-time queued traffic at high blocking probability is combined with another server group carrying normal blocked-calls-cleared traffic at low blocking probability, the resulting mixed group will in many cases operate at an intermediate blocking probability. Thus the mixed group provides better service to the queued traffic, while degrading the service of the cleared traffic. If the random arrival characteristics of the short-holding-time traffic are suitably modified by delaying calls an appropriate time before service, then the grades of service for both types of traffic may be engineered independently. An example of a possible use of this technique of induced delay, the combining of dispatch and mobile-telephone traffic on the same set of radio channels in the High-Capacity Mobile Telecommunications System, is discussed.     

A learning approach for prioritized handoff channel allocation in mobile multimedia networks

An efficient channel allocation policy that prioritizes handoffs is an indispensable ingredient in future cellular networks in order to support multimedia traffic while ensuring quality of service requirements (QoS). In this paper we study the application of a reinforcement-learning algorithm to develop an alternative channel allocation scheme in mobile cellular networks that supports multiple heterogeneous traffic classes. The proposed scheme prioritizes handoff call requests over new calls and provides differentiated services for different traffic classes with diverse characteristics and quality of service requirements. Furthermore, it is asymptotically optimal, computationally inexpensive, model-free, and can adapt to changing traffic conditions. Simulations are provided to compare the effectiveness of the proposed algorithm with other known resource-sharing policies such as complete sharing and reservation policies     

Vehicle location in cellular mobile radio systems

A tutorial discussion of vehicle location as used to control cellular mobile radio systems is presented. Early concepts and misconceptions concerning vehicle location are described, and the relation between location "accuracy" and system performance optimization is discussed. Measurement parameters commonly used for vehicle location are described, and considerations relating to the algorithm used in the location process are presented.     

Capacity estimation of cellular mobile radio systems

A capacity estimation procedure for cellular systems is introduced under a condition of concentrated traffic distribution. Comparisons are made of systems with 12.5 kHz and 25 kHz channel spacing to clarify the difference in system capacity for uniform and concentrated traffic distribution conditions. The results show it is necessary to take actual traffic distribution conditions into account in making system capacacity estimations.     

Outage probabilities of cellular mobile radio systems with multipleNakagami interferers

Closed-form expressions for outage probabilities of mobile radio channels experiencing multiple, cochannel, independent Nakagami interferers are derived. This is done for the case of Nakagami fading alone with an arbitrary number of interferers. Analytical results for the case of Nakagami fading combined with log-normal shadowing are obtained for a single interferer. The case of multiple shadowed interferers is examined by simulation. The fading severity parameter in the Nakagami distribution may be varied to model different fading conditions. Interferers with similar and different Nakagami statistics are analyzed. The probability of cochannel interference is related to the reuse distance, which is one of the key parameters in the design of cellular mobile radio systems. In addition, the effects of specifying a minimum signal power requirement for satisfactory reception are investigated. A number of system examples that illustrate applications of the results are included     

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     

Frequency allocation for a mobile radio telephone system

Several ways of allocating frequencies efficiently are suggested that are based on the use of Latin squares. A Latin square of order n is a square array of n rows and n columns, and involving n symbols each of which occurs n times within the square in such a way that all the different symbols occur once in each row and once in each column. This approach provides two alternative ways of arranging the transmitters for a mobile radio telephone system, one rectangular and the other close-packed hexagonal. In both cases optimal patterns for frequency allocation result. A solution using the least-possible number of frequencies for each case is given, as well as one that is ideal in the sense that all the transmitters that surround any particular one are provided with distinct frequencies     

Spectrum efficiency analysis for microcellular mobile radio systems

Spectrum efficiency is analysed in a microcellular mobile radio environment considering an appropriate model for UHF ground-wave path loss. The influence of cluster size and reuse distance on the spectrum efficiency is investigated by obtaining the probability of cochannel interference for uncorrelated Rayleigh fading interferers and Rician fading desired signal. The effect of traffic intensity is also considered in evaluating the spectrum efficiency.<>     

A channel allocation for cellular mobile radio systems using simulated annealing

We consider the channel allocation problem, which is one of the most interesting problems in mobile radio systems. This problem is known to be NP‐complete and a couple of heuristic algorithms have been developed. In this paper, we convert the problem into a simpler form through the concept of pattern, a set of cochannel cells. We suggest another algorithm based on simulated annealing for this simplified problem. The algorithm is applied into different benchmark problems that have appeared in the literature. The presented examples illustrate that our method works very well. Computational results using our formulation and simulated annealing algorithm are reported. This revised version was published online in August 2006 with corrections to the Cover Date.     

Multiple correlated log-normal interferers in mobile cellular radio systems

The probability of cochannel interference (PCI) is evaluated in shadowed mobile cellular systems considering multiple correlated log-normal interferers. The influence of blocking probability and the number of channels per cell on the performance is also presented. The effect of correlation on PCI is investigated for various values of the propagation path loss exponent.<>