Analytical Studies of Fragmented-Spectrum Multi-Level OFDM-CDMA Technique in Cognitive Radio Networks

In this paper, we present a multi-user resource allocation framework using fragmented-spectrum synchronous OFDM-CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, a channel sensing and estimation method is used to obtain information of subcarrier availability. Given this information, some real-valued multi-level orthogonal codes, which are orthogonal codes with values of $\{\pm1,\pm2,\pm3,\pm4, ... \}$, are provided for emerging new users, i.e., cognitive radio users. Additionally, we have obtained a closed form expression for bit error rate of cognitive radio receivers in terms of detection probability of primary users, CR users' sensing time and CR users' signal to noise ratio. Moreover, simulation results obtained in this paper indicate the precision with which the analytical results have been obtained in modeling the aforementioned system.Comment: 6 pages and 3 figure

Cognitive Radio for Emergency Networks

In the scope of the Adaptive Ad-hoc Freeband (AAF) project, an emergency network built on top of Cognitive Radio is proposed to alleviate the spectrum shortage problem which is the major limitation for emergency networks. Cognitive Radio has been proposed as a promising technology to solve todayâ?~B??~D?s spectrum scarcity problem by allowing a secondary user in the non-used parts of the spectrum that aactully are assigned to primary services. Cognitive Radio has to work in different frequency bands and various wireless channels and supports multimedia services. A heterogenous reconfigurable System-on-Chip (SoC) architecture is proposed to enable the evolution from the traditional software defined radio to Cognitive Radio

Damped Zero-Pseudorandom Noise OFDM Systems

This paper proposed a new OFDM scheme called damped zero-pseudorandom noise orthogonal frequency division multiplexing (DZPN-OFDM) scheme. In the proposed scheme, ZPN-OFDM non-zero part damped to reduce the guard interval energy as well as the mutual interference power in-between the data and training blocks, and conservative the pseudo-noise conventional properties required for channel estimation or synchronization. The motivation of this paper is the OFDM long guard interval working in wide dispersion channels, where significant energy waste if conventional ZPN-OFDM is used as well as the BER performance degradation. Also, to solve the ZPN-OFDM spectrum efficiency loss problem, the proposed scheme doesn’t duplicate the guard interval. Both detailed performance analysis and simulation results show that the proposed DZPN-OFDM scheme can, indeed, offer significant bit error rate, spectrum efficiency as well as energy efficiency improvement

Orthogonal Frequency-Division Multiplexing-Based Cooperative Spectrum Sensing for Cognitive Radio Networks

The detection of transmitted data collusion among sensing nodes needs to be resolved at data link layer. It takes a lot algorithm calculation effort and time constraint. A new method to sense the performance of cognitive radio (CR) by avoiding interference based on new master node (MN) algorithm. Interference could be reduced significantly by using only PHY (physical) information of the cognitive radio network. It saves a lot computational on above layer and detect the collusion of transmitted data as early as possible. By using a novel MN algorithm at PHY layer, it reduces the cost of computation and time to detect and avoid collusion of transmitted data