Novel Spectrum Sensing Algorithms for OFDM Cognitive Radio Networks

Cognitive radio (CR), as a concept based on the ability to detect and share the unutilised spectrum, has been envisioned as a promising candidate to improve the efficiency of frequency spectrum assignments. For the realisation of the CR concept, energy detection (ED), as one of the available spectrum sensing methods, is broadly considered because of its low computational complexity and implementation costs. Due to the vast usage of the orthogonal frequency division multiplexing (OFDM) technique in contemporary communication systems, the ED of OFDM signals in the CR networks has become important for practical realisation. Since the ED accuracy of the OFDM signals can be improved by the sensing threshold adaptation, this paper surveys the impact of noise variations and dynamic threshold (DT) adaptation on the ED performance of OFDM signals. Analyses were performed by the simulation of the ED related to OFDM signals transmitted in the margin or rate adaptive and combined margin and rate adaptive OFDM systems. The results obtained through extensive simulations provide fundamental insights into how different factors, including the transmission power, the signal to noise ratio, the false alarm probability and the sample quantity, affect the ED efficiency. Comprehensive analyses of the obtained results indicate the main ED weaknesses and how the appropriate selection of analysed factors can enhance the ED processes for different OFDM systems. The observed ED weaknesses were further thoroughly surveyed, and the open issues and challenges related to the enhancement of the main ED limitations have been elaborated. The presented survey results can serve as a basis for the improvement of a broadly accepted ED method in CR networks.

Section: Introductionmentioning

confidence: 99%

A Survey on the Energy Detection of OFDM Signals with Dynamic Threshold Adaptation: Open Issues and Future Challenges

Lörincz

Ramljak²,

Begušić

2021

“…In recent years, regulatory bodies such as FCC and Ofcom [ 1 , 2 , 3 ] have approved the dynamic access of unlicensed sensor networks, referred to in the following as Secondary Sensor Networks (SSNs), to the TV White Space (TVWS) spectrum. The existing regulations circumvented the need for sensing algorithms for establishing the availability of free TVWS spectrum [ 4 , 5 , 6 , 7 ], since they require the SSNs to periodically obtain the the list of TVWS channels free from licensed users from a geolocated database [ 8 , 9 ]. Hence, it is reasonable to expect that multiple and heterogeneous SSNs based on different standards such as [ 10 , 11 , 12 ] are expected to coexist within the same geographical region over shared TVWS spectrum.…”

Section: Introductionmentioning

confidence: 99%

On the Achievable Throughput Over TVWS Sensor Networks

Caleffi

Cacciapuoti

2016

In this letter, we study the throughput achievable by an unlicensed sensor network operating over TV white space spectrum in presence of coexistence interference. Through the letter, we first analytically derive the achievable throughput as a function of the channel ordering. Then, we show that the problem of deriving the maximum expected throughput through exhaustive search is computationally unfeasible. Finally, we derive a computational-efficient algorithm characterized by polynomial-time complexity to compute the channel set maximizing the expected throughput and, stemming from this, we derive a closed-form expression of the maximum expected throughput. Numerical simulations validate the theoretical analysis.

“…Nevertheless, PLC-based systems still have some details that can be improved in order to achieve a better performance. One of them is the implemented medium access technique, where most of the previous works have been focused on Multi-Carrier Modulation (MCM) [ 10 , 11 ], not only in PLC but also in other standards [ 12 ] like Long Term Evolution (LTE) [ 13 ]. MCM allows the performance and the spectrum efficiency to be enhanced by dividing the available bandwidth into subchannels, which data are transmitted through.…”

Section: Introductionmentioning

confidence: 99%

Efficient Implementation of a Symbol Timing Estimator for Broadband PLC

Nombela

García

Mateos

et al. 2015

Broadband Power Line Communications (PLC) have taken advantage of the research advances in multi-carrier modulations to mitigate frequency selective fading, and their adoption opens up a myriad of applications in the field of sensory and automation systems, multimedia connectivity or smart spaces. Nonetheless, the use of these multi-carrier modulations, such as Wavelet-OFDM, requires a highly accurate symbol timing estimation for reliably recovering of transmitted data. Furthermore, the PLC channel presents some particularities that prevent the direct use of previous synchronization algorithms proposed in wireless communication systems. Therefore more research effort should be involved in the design and implementation of novel and robust synchronization algorithms for PLC, thus enabling real-time synchronization. This paper proposes a symbol timing estimator for broadband PLC based on cross-correlation with multilevel complementary sequences or Zadoff-Chu sequences and its efficient implementation in a FPGA; the obtained results show a 90% of success rate in symbol timing estimation for a certain PLC channel model and a reduced resource consumption for its implementation in a Xilinx Kyntex FPGA.