No abstract

As a result of the drastic increase in the number of mobile device users, there is considerable public debate about possible health hazards especially due to base stations and Wi-Fi access points. For this reason, in this study the effects of the number of users in a base station and wireless fidelity (Wi-Fi) access point on electric field strength (E) levels were investigated using real-time measurements. Two-stage E measurements were performed on Ondokuz Mayıs University's (OMU) Kurupelit Campus with a PMM-8053 and SRM-3006 electromagnetic field (EMF) meter. In the first stage, 24-h measurements were performed with PMM-8053 at the location where the maximum E was measured and from which the busiest times of the day were then determined. The relationship among band selective E values was assessed using the number of users per minute provided by three cellular system operators for the location. Upper and lower bounds of E according to the number of users were calculated, and then an empirical model that helps calculate the E of medium with 86% accuracy was proposed. In the second stage, the effect of the number of users in a Wi-Fi access point on E level was investigated. For this purpose, the measurement environment was set as including one Wi-Fi access point with needed measurement devices. The number of users was increased as per user per minute. The number of users was validated with the data obtained from OMU IT Department. Using the measurement result, a model with a 96% accuracy between the E value in the environment and the number of users accessing the Wi-Fi system is proposed. With the use of these models, E level in the medium can be determined without using any EMF meters, thus precautions can be taken to stay within regulatory limits.

Özetçe-KBÇEtabanlı sistemlerde çok kullanıcılı sezme (ÇKS) yöntemleri kullanılarak çoklu erişim girişiminin (ÇEG) etkisi giderilip sistem başarımı artırılır. Bu yöntemlerden bir tanesi olan paralel girişim bastırma (PGB) yöntemi anlık olarak tüm kullanıcı bilgilerini tahmin edip aktif kullanıcı sinyalinden ÇEG sinyalini çıkartmak temeline dayanmaktadır. Bu çalışmada, radyo kanalının ve kullanıcı sayısının PGB'li geniş bant KBÇE (GB-KBÇE) sistem başarımına etkisi incelenmiştir. Değerlendirmelerde gezgin radyo kanalı olarak Manchester kent merkezinde yapılan radyo kanalı ölçümlerinde elde edilen 4 kanal profili ve 2, 4, 8, 15 kullanıcı sayısı ve 3 parmaklı Tırmık alıcı yapısı kullanılmıştır. Sonuçlardan PGB başarımının kanalın yankı profiline ve kullanıcı sayısına bağlı olarak anlamlı ölçüde değiştiği görülmüştür. Anahtar Kelimeler-GB-KBÇE, çoklu erişim girişimi, çok kullanıcılı sezme, paralel girişim bastırma, uyumlu filtre.