Manuel Duque-Antón

Channel assignment for cellular radio using simulated annealing

The channel assignment problem, i.e. the task of assigning the channels to the radio base stations in a spectrum-efficient way, is an NP-complete optimization problem occurring during design of cellular radio systems. Previously, this problem has been solved by graph coloring algorithms. An alternative approach is presented. The problem is solved using simulated annealing, which is a general approach to combinatorial optimization. The algorithm has been successfully applied to practical radio network planning situations. One major benefit of the approach consists in the enhanced flexibility it gives to the engineer. >

Static and Dynamic Channel Assignment Using Simulated Annealing

When planning a radio network, the operator has to assign frequencies, or more general channels, to base stations in, such a way that both, the call quality and the channel availability are good enough. This means that for an incoming call request the probability that an idle channel can be found is sufficiently high, and the probability that the signal-to-interference-ratio S/I falls short of a predefined value is sufficiently low.

Constructing efficient simulated annealing algorithms

Abstract Simulated annealing is a general purpose optimization technique for combinatorial optimization problems. In order to improve the efficiency of simulated annealing, the neighbourhood structure and the generation probabilities have to be designed carefully. Usually, this process is problem dependent and, hence, unlikely to be generally applicable to various combinatorial problems. In the present paper a general theory is introduced and proved to support the construction of efficient generation mechanisms. In order to reduce the complexity of the problem, a particular problem-dependent equivalence relation within the set S of all possible configurations can be defined, determining a quotient set within the original set S. If all optimal configurations are assigned to the same equivalence class, in order to find an optimal configuration, it suffices to wander within the quotient set instead of the original set S. If the average size of a non-optimal equivalence class is much larger than the size of the optimal class, the optimal configurations will be preferred during the annealing process. This translates to a significant reduction in CPU time. To avoid the need to compute the quotient set explicitly, the search procedure in the quotient set is simulated within the original set of configurations. Our approach has parallels with the ejection chain strategies used in tabu search, and our theory provides further motivation for such strategies (in addition to the combinatorial leverage theorems of tabu search). Applications to the channel assignment problem which occurs during the design of cellular radio systems demonstrate clearly the power of the general construction theory. With the new method we can construct generation mechanisms that reduce the exponential complexity of the configuration set to a polynomial dependence on the problem size, as characteristic of the combinatorial leverage phenomenon of ejection chains.

Extending Kohonen's self-organizing mapping for adaptive resource management in cellular radio networks

To satisfy the growing demand for mobile communication, microcellular systems are expected to be introduced in the near future. For these, the development of fast, reliable, and spectrum-efficient radio-resource management procedures is mandatory. Topology-conserving mappings play an important part in the biological processing of sensory input. We suggest that principles found capable of establishing such maps could also be applied to organize the learning of radio-resource assignments.

A Software Architecture for Control and Management of Distributed ATM Switching

Distributed switching will become a key feature for flexible and inexpensive workgroup switches as well as for dedicated high performance networking solutions. The Philips Research Laboratories in Aachen have demonstrated the feasibility of distributed ATM switching by developing a ring-based ATM switch. After solving the hardware related problems we are now focusing our efforts on the design of a distributed software platform for switch control and management purposes.

Open Switching for ATM Networks

This contribution discusses the way how Open Switching can be supported in ATM networks. First the elements of an ATM system that are relevant for call control and call handling are described. Then we evaluate which of the call control interfaces should be realized by which parts of the system, especially which signalling aspects are relevant for the software architecture on network side. Finally we propose a concept for the integration of external call control as part of the network control architecture. The paper aims at a switch control architecture that facilitates for providing advanced applications in ATM networks by external call control. The definition of standardized protocols and the design of Open Switching applications themselves are out of the scope of our work.

A switch control software architecture for future ATM broadband services

Besides the basic function to route cells an ATM switch has to make provision for several higher layer functions such as call control and switch management. Call control functions such as call handling and call admission control are usually performed in software on a more or less dedicated switch-CPU. For the future, even more additional functionalities in the area of network management, open switching and mobility management for wireless ATM networks can be expected. This paper presents a switch control software architecture which provides the basic switch functionality as well as a means for integrating new services. This software will be implemented on the Philips distributed ATM switch which has been developed at the Philips Research Laboratories, Aachen.

Formulas, Processes, and Petri-Nets Applied to the Specification and Verification of a HDLC Protocol

In specifying a variant of a HDLC protocol we illustrate a method that addresses three problems: decompostion of a complex system into simple components, hierarchical design of a protocol starting from the service specification and resulting in the protocol description and, finally, modular verification of the protocol w.r.t. the service specification. The theoretical basis is given by Process Theory. Descriptions of basic protocol functions are obtained considering projections of the global protocol behaviour onto ‘locally’ relevant sets of events. Compositionality of semantics allows reasoning about complete (protocol-)components by induction over properties of their constituents. To formalize behaviour we use formulas, process terms and Petri-Nets.