Dimension spreading for coherent opportunistic communications

ICC 2019 - 2019 IEEE International Conference on Communications (ICC)

2019

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The uncoordinated design of pulse shaping filters for opportunistic communications is addressed. We show that under degrees-of-freedom sensing uncertainties the waveform design problem can be cast as a minimum-norm optimization, admitting hence a closed-form expression. Because designed waveforms are adapted to scenario working conditions, proposed design scheme may be considered in pilot reference signals design to achieve orthogonality, regardless the traditionally considered pilot symbols orthogonality. Hence, the effect of interferences such as pilot contamination is diminished. However, a crucial aspect relies on their detectability. Since each node uses only local observations from the wireless network, the sensed degrees-of-freedom may slightly differ from one node to others. In this paper we prove that, thanks to the existence of some invariances, designed waveforms can be detected by neighboring nodes. Even though degrees-offreedom sensing uncertainties may incur in a performance loss, we propose a least-squares constrained basis pursuit algorithm to reduce the effect of uncertainties by considering only the degreesof-freedom subspace intersection.

“…Hereunder we detail the decentralized pulse shaping design scheme. It is worth noting that it consists in a generalization of particular examples presented by the authors in [15], [16].…”

Section: Uncoordinated Pulse Shaping Designmentioning

confidence: 99%

“…Due to lack of space, the derivation of (10) is only sketched herein. The reader is referred to [15], [16] for further details. By solving the maximization problem in (10), we get…”

Section: Uncoordinated Pulse Shaping Designmentioning

confidence: 99%

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Decentralized Shaping for Pilot Generation and Detection in Opportunistic Communications

ICC 2019 - 2019 IEEE International Conference on Communications (ICC)

2019

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“…In this case, the upper-bound on DOFs uncertainty is k k F  ✏, being k • k F the Frobenius norm. As discussed in [6], when the worst case is taken into consideration, the error matrix indicates that all occupied DOFs are shadowed, providing then the maximum crossinterference to external users. Thus, minimizing the norm of the designed pilot is the best that can be done to achieve the highest performance under the worst conditions.…”

Section: Joint Beam and Dimension Spreading-based Uncoordinated mentioning

confidence: 99%

“…For instance, noise subspace-based waveforms are used to precode opportunistic signals. The main dissemblance between different strategies is that side information may be acquired statistically [5], [6], imperfectly [7][8][9] or instantaneously [10][11][12]. References therein are suggested to the reader for further information.…”

Section: Introductionmentioning

confidence: 99%

Uncoordinated Space-Frequency Pilot Design for Multi-Antenna Wideband Opportunistic Communications

2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)

2018

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The statistical side information of interference channels is exploited in this paper to derive a novel uncoordinated on-line pilot design strategy for opportunistic communications. Assuming a time division duplex (TDD), or frequency division duplex (FDD) with feedback, wireless network and reciprocity, we prove that the space-frequency pilot design technique in terms of minimum cross-interference to external-network users reduces to a classical minimum-norm problem. The advantages of this novel methodology are time-domain invariance to noise-subspace rotations, a maximally flat angle-frequency response, and robustness in front of frequency calibration errors. Simulation results are reported to assess the performance of the proposed strategy and the advantages of its low-resolution quantization in low signal-tonoise ratio (low-SNR) regimes. Index Terms-Opportunistic communications, pilot and waveform design, multi-antenna systems, distributed networks, wideband regime.

Interference Mitigation under Degrees-of-Freedom Sensing Uncertainties in Opportunistic Transmission

2019 IEEE Global Communications Conference (GLOBECOM)

2019

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Inter-system interference may limit the performance of co-existing systems in dense heterogeneous wireless networks. Context-aware waveform design can profitably overcome this limitation. However, the latter substantially depends on degreesof-freedom (DoF) sensing mechanisms. In this work, we show that total least-squares (TLS)-based waveform design is robust against sensing uncertainties. Given the equivalence of minimum norm and TLS, the latter exhibits the good properties of linear predictors, which are of paramount importance to guarantee minimum inter-system interference and detectability by neighboring nodes. Additionally, since derived solution relies on orthogonal projector onto the so-called noise subspace, we can efficiently and iteratively construct an orthogonal waveform-book enabling the presented transmission scheme in multi-carrier scenarios. Simulation results are presented to support our theoretical contributions, and to highlight any potential advantage of proposed solution in crowded heterogenous wireless networks. Index Terms-Opportunistic communications, distributed networks, total least-squares, sensing uncertainties, waveform design.