Performance assessment & synergic operation of algorithmic solutions enabling opportunistic networks– D4.2

Deliverable D4.2 del projecte europeu OneFITPeer ReviewedPostprint (updated version

Collaborative spectrum sensing in OFDM-based cognitive radio

The rapid increase in the number of wireless devices highlights the importance of intensive dynamic use of the available spectrum. One technology to implement dynamic spectrum access is Cognitive Radio (CR). One of the main challenges CR is gaining spectrum awareness, thus being able to undertake reliable and sufficiently sensitive spectrum sensing. In this paper, an OFDM-based CR system exploiting the inherent cyclic prefix (CP) and idle period of the transmission signals is proposed, assuming a realistic fading channel. Furthermore, collaborative spectrum sensing has been studied based on the proposed methodology, in the presence of Rayleigh fading and log-normal distributed shadowing. The simulation results indicate that the probability of detection can be significantly improved while maintaining the level of interference protection to the primary users by including the CP and idle period in the sensing time in both slow and fast fading channels. Moreover, collaboration of multiple secondary users improves the sensitivity of the sensing algorithm in terms of minimum detectable SNR. The analyses provided in this paper show that collaboration among 10 users facilitates detection at lower SNR levels up to -10 dB with 0.9 probability of correct detection and 0.1 probability of false alarm

Dynamic spectrum allocation algorithm with interference management in displaced networks

Dynamic spectrum allocation (DSA) has been cited as a promising mechanism for managing the radio spectrum for coexisting systems. The goal of the DSA scheme is to increase the performance of networks in the shared spectrum, by providing a more efficient way of utilisation. This work addresses analytically the impact of multi-cell, multi-operator interference on the overall spectrum when multiple operators co-exist and share a common pool of radio resources. We propose a centralised DSA scheme that is able to capture the interference level and interact dynamically to minimise interference and enhance spectrum utilisation while maintaining a satisfactory level of QoS. Furthermore, a concise system model and framework able to describe the interaction among different operators is presented. The DSA algorithm has been investigated for co-located and displaced cellular networks. The simulation results indicate that the proposed DSA algorithm significantly outperformed the fixed spectrum allocation (FSA) ensuring minimum level of interference in the system. The QoS of the overall system has been improved in the DSA compared to traditional FSA. Moreover, the proposed algorithm enhanced the spectrum utilization by 26% guaranteeing that all operators are given fair access to the shared spectrum

Dynamic spectrum allocation algorithm with interference management in co-existing networks

This work addresses analytically the impact of multi-cell, multi-operator interference on the overall radio resources when multiple operators co-exist and share a common pool of spectrum. We propose a centralised dynamic spectrum allocation (DSA) scheme that is able to measure the interference level and interact dynamically to minimise interference and enhance spectrum utilisation while maintaining a satisfactory level of QoS. Furthermore, a concise system model and framework able to describe the interaction among different operators is presented

Optimal Packet Length for Free-Space Optical Communications with Average SNR Feedback Channel

In this article, a method to enhance data rates of free-space optical (FSO) systems using packet length optimization is proposed. The average signal-to-noise ratio (ASNR) is measured at the receiver and sent back to the transmitter to optimize packet length. In addition, the length of packet is optimized to enhance the average throughput. We concluded that packet length can be reduced at low ASNR. However, packet length should be increased at higher values of received ASNR. For each ASNR, we also choose the optimal modulation and coding scheme (MCS) and optimal packet length to maximize the throughput. Different MCSs are investigated such as 4-pulse amplitude modulation (PAM) with and without channel coding, 8-PAM, 16-PAM, and 32-PAM. The proposed method gives 0.8–1.9 dB gain with respect to conventional FSO with adaptive modulation and coding (AMC) and fixed packet length. This is the first paper to deal with packet length optimization for FSO systems