Novel overlay/underlay cognitive radio waveforms using SD-SMSE framework to enhance spectrum efficiency- part i: theoretical framework and analysis in AWGN channel

• Published in: IEEE transactions on communications Vol. 57; no. 12; pp. 3794 - 3804
• Main Authors: Chakravarthy, Vasu, Li, Xue, Wu, Zhiqiang, Temple, Michael A., Garber, Fred, Kannan, Rajgopal, Vasilakos, Athanasios
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-12-2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Additive white noise; Applied sciences; AWGN channels; Channels; Chromium; Code Division Multiple Access; Cognitive radio; Cryptography; dynamic spectrum access; Efficiency; Exact sciences and technology; Fading; FCC; Flexibility; Gaussian noise; Information, signal and communications theory; Maximization; Modulation, demodulation; Multicarrier code division multiple access; OFDM; overlay waveform; Performance analysis; Policies; Radiocommunication specific techniques; Radiocommunications; Signal and communications theory; Spectra; spectrum efficiency; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teletraffic; underlay waveform; Waveforms; Wireless communication; Wireless communications; Performance evaluation; Error probability; Wireless telecommunication; Frequency division multiplexing; Flexibility; AWGN channels; overlay waveform; underlay waveform; Modulation; Security of data; Digital signature; Soft decision; Fading channels; Availability; Channel capacity; dynamic spectrum access; Multicarrier; Teletraffic; Frequency domain method; Cognitive radio; Code division multiple access; Orthogonal frequency division multiplexing; spectrum efficiency; Public key cryptography; Hierarchical system; Traffic congestion; Software radio
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2009.12.080400

Recent studies suggest that spectrum congestion is primarily due to inefficient spectrum usage rather than spectrum availability. Dynamic spectrum access (DSA) and cognitive radio (CR) are two techniques being considered to improve spectrum efficiency and utilization. The advent of CR has created a paradigm shift in wireless communications and instigated a change in FCC policy towards spectrum regulations. Within the hierarchical DSA model, spectrum overlay and underlay techniques are employed to enable primary and secondary users to coexist while improving overall spectrum efficiency. As employed here, spectrum overlay exploits unused (white) spectral regions while spectrum underlay exploits underused (gray) spectral regions. In general, underlay approaches use more spectrum than overlay approaches and operate below the noise floor of primary users. Spectrally modulated, spectrally encoded (SMSE) signals, to include orthogonal frequency domain multiplexing (OFDM) and multi-carrier code division multiple access (MC-CDMA), are candidate CR waveforms. The SMSE structure supports and is well suited for CR-based software defined radio (SDR) applications. This paper provides a general soft decision SMSE (SDSMSE) framework that extends the original SMSE framework to achieve synergistic CR benefits of overlay and underlay techniques. This extended framework provides considerable flexibility to design overlay, underlay and hybrid overlay/underlay waveforms that are scenario dependent. Overlay/underlay framework flexibility is demonstrated herein for a family of SMSE signals, including OFDM and MC-CDMA. Analytic derivation of CR error probability for overlay and underlay applications is presented. Simulated performance analysis of overlay, underlay and hybrid overlay/underlay waveforms is also presented and benefits discussed, to include improved spectrum efficiency and channel capacity maximization. Performance analysis of overlay/underlay CR waveform in fading channels will be discussed in Part II of the paper.