Effective capacity evaluation model for cognitive radio networks using ofdm

Authors: 
M. Kyryk, V. Yanyshyn, I.B. Strykhalyuk

Lviv Polytechnic National University

In this paper considered the cognitive radio (CR) networks with the GSM network like primary network cooperation possibility. The cognitive radio system meant radio with a self-management mechanism with different levels of ability to adapt to the changing radio environment. The self-management mechanism is based on the principles of learning and artificial intelligence. In world practice, the frequency assigned to a particular entity in a certain area on a long term basis. However, most commonly frequency for this designated area not always used, and as necessary. In other words, many frequency bands are irregularly loaded in the space and time domains. Because of the shortage of frequency resources are limited to the cellular network to the data rate. The data rate of modern communication systems is also increasing due to the use high-level types of signal modulation, requiring more signal/noise ratio at the receiver input. Existing GSM network is almost completely satisfy the needs of users for voice services, but the data rate cannot compete with cellular networks based on UMTS and LTE technologies. Here proposed high speed data transmitting method in GSM based on the principles of cognitive radio. On the existing GSM network topology (primary/licensed network) complementary superimposed secondary/unlicensed network operating in the same frequency bands.
CR system must have ability to measure, sense, learn, and be aware of important operating conditions. It should be able to find and exploit the unused parts of the spectrum at the fastest and efficient way. The popular spectrum sensing algorithms such as matched filtering, energy detection, spectral correlation (cyclostationarity), radio identification based sensing, waveform based sensing can provide awareness of CR system. Moreover, cooperation spectrum sensing can reduce the detection time and increase the agility, but also facilitate the problem of hidden terminal, shadowing or severe multipath fading. Here proposed to use OFDM for the CR system and discussed OFDM’s advantages to allow better sensing and spectrum shaping capabilities, considered OFDM-symbol formation method in CR system and determined the data structure organization. The mathematical simulation model of CR network with one primary system and one secondary cell created for accurate capacity evaluation of selected system. Model simulates GSM primary users’ activity and CR network operation scheme that taking into account the radio environment conditions, CR users location and their quality requirement for different type of services.