Abstract-This paper deals with the automatic selection and configuration of base station sites for mobile cellular networks. An optimization framework based on simulated annealing is used for site selection and for base-station configuration. Realistic path-loss estimates incorporating terrain data are used. The configuration of each base station involves selecting antenna type, power control, azimuth, and tilt. Results are presented for several design scenarios with between 250 and 750 candidate sites and show that the optimization framework can generate network designs with desired characteristics such as high area coverage and high traffic capacity. The work shows that cellular network design problems are tractable for realistic problem instances.Index Terms-Cell planning, heuristics, radio frequency assignment, radio network design.

Abstract. This paper describes a system, FASoft, for discrete channel frequency assignment. In practice, the assignment of frequencies in a network of compatible equipment is often done manually or by the use of a single computational technique. FASoft incorporates state-of-the-art heuristics, sequential assignment algorithms, and a maximal clique algorithm to aid in the assignment process. Lower bounding procedures are included into the system to assess the performance of the assignment techniques and to provide an assessment of how close a particular assignment is to the optimal. The results show that FASoft produces optimal solutions to several practical examples. IntroductionThe radio spectrum is an important natural resource. Many services, both civil and military, require access to the spectrum in order to function, and the demand for frequencies is increasing year by year. Consequently, efficient management of the spectrum requires that frequencies be assigned, for a particular service, in an optimum or near-optimum manner. In practice, this assignment of frequencies is often done using greedy heuristics, which mimic the way the process may be done manually. These methods produce assignments quickly (even for large problems) but inevitably use more spectrum than is necessary. Exact methods based on graph theory give the optimum solution but are computationally unrealistic for problems involving •>50 transmitters. The purpose of this paper is to show how the so-called metaheuristic techniques (simulated annealing, genetic algorithms, and tabu search) can be used to produce optimum solutions to frequency assignment problems. This paper is concerned with the assignment of discrete channels to the transmitters of a system of compatible equipment. In some applications, such as cellular radio networks, the coverage area is divided into a number of cells, typically hexagonal, with each cell assigned a set of frequencies. We refer to such A software system FASoft will be described which produces a frequency assignment for any problem described by a constraint matrix, not necessarily a cellular system. FASoft can handle constraints with transmitters external to the system under consideration. However, it does not handle issues such as intermodulation products or required bandwidth for different modulation schemes such as digital code division multiple access (CDMA), nor does it address problems such as spread spectrum systems and discrete narrowband systems operating in the same 1921

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Algae blooms are a seasonal problem in UK waters and during these periods interferences with treatment plants are reported. This paper presents an analysis of data from 2000 to 2005 demonstrating UK experiences of algae at water treatment works. Cell populations are lower than those reported in the 1970s and 1980s, but reach levels that adversely affect treatment processes. Diatoms and cyanobacteria dominate in spring and autumn respectively. A treatment works including pre-oxidation, coagulation, flotation and filtration removes on average 96% of influent cells, while rapid gravity filters alone remove 63-75%. Cells present in the filtrate are typically either unicellular, micro-algae, or flagellated algae. filter blockages in the spring and autumn are caused by large cells of complex morphology, including the diatoms Melosira and Asterionella. Overall, since the 1980s the key issue with respect to algae treatment has changed from one of treatability to that of process optimisation and economics.