Access Points Placement as a Discrete Optimization Problem

In this work, we consider a method of searching of the direction of a wireless network development (the places of new access points or base stations etc.) optimized with criteria of coverage of important territories and minimum cost of equipment and additional needed infrastructure which does not need the execution of special field testings and determination of the exact geometry of elements of RF-propagation medium and their RF absorbing properties but takes into account the minimum accessible information obtained from built-in measuring instruments of wireless hardware and approximate data of the medium elements shape. The problem of search of a disposition and types of the infrastructure elements of the growing network is formulated as a multicriteria discrete constrained optimization problem solvable with variant probability method [1]. The problem of a medium RF-propagation properties modeling is also formulated and solved as a discrete optimization task. 1.INTRODUCTION The sparsely populated territories with underdeveloped infrastructure need a special approach for solving the problem of supply with the telecommunication facilities. The uninterrupted rapid growth of the telecommunication networks including qualitative increasing of data channels bandwidth and quality of service is mostly typical for the megapolises and densely populated territories is least apparent in remote and sparsely populated regions where the networks are nevertheless apparent. On the one hand, the absence of any infrastructure (not only telecommunication one but also traditional telephone lines, power transmission lines and roads along which the telecommunication cables infrastructure are usually laid) embarrasses the development of the traditional cable infrastructure. The implementation of ADSL technology using the existing cable infrastructure is also impossible. On the other hand, the necessity to supply that territories with the qualitative network access is dictated by the standards (written or de-facto ones) of the office work and business processes of various business, governmental, educational and research organizations. Furthermore, the remote territories need a qualitative communications which makes them 'nearer' to the 'big earth' even more than the central regions because this is the only way to establish contacts with the partners, to realize centralized management and even to make simple things like bank transfer. In conditions of the Northern Siberia, the existence of any serious cable infrastructure is often absolutely impossible even within small territories (for example, territory of a settlement) because of permafrost, bogs, moving soil. By the way, this problem embarrasses also the placing of wireless base stations, nevertheless, only the wireless technologies have any the serious perspectives at these territories. Certainly, the satellite technologies allow to establish the Internet access, telephone connection and everything else at every point but they are expensive. That is why, the local area networks (often covering large territories) are usually developed with WiFi technology (often, in addition to VSAT equipment as a gateway to WAN). Often, such networks are developed chaotic as far as an exigency to cover new territories arises. The equipment (especially arctic versions of devices) is not too cheap. The superfluous quantity of access points does not do much good because of interference and frequency sharing problems but this problem is less actual for sparsely populated territories. The execution of the field testings of RF-propagation properties of medium and its geometry need special equipment, skilled personnel and significant expenditure of labor. Meanwhile, the maximum usage of available information (even if it is not precise) of signal and noise levels at different points and RF absorbing 1 Author gratefully acknowledges the ICTP-ITU 2008 School on New Perspectives in Wireless Networking (2008, Trieste, Italy)