218,478 research outputs found
Sensing-Assisted Communication in Vehicular Networks with Intelligent Surface
The recent development of integrated sensing and communications (ISAC)
technology offers new opportunities to meet high-throughput and low-latency
communication as well as high-resolution localization requirements in vehicular
networks. However, considering the limited transmit power of the road site
units (RSUs) and the relatively small radar cross section (RCS) of vehicles
with random reflection coefficients, the power of echo signals may be too weak
to be utilized for effective target detection and tracking. Moreover,
high-frequency signals usually suffer from large fading loss when penetrating
vehicles, which seriously degrades the quality of communication services inside
the vehicles. To handle this issue, we propose a novel sensing-assisted
communication mechanism by employing an intelligent omni-surface (IOS) on the
surface of vehicles to enhance both sensing and communication (S&C)
performance. To this end, we first propose a two-stage ISAC protocol, including
the joint S&C stage and the communication-only stage, to fulfill more efficient
communication performance improvements benefited from sensing. The achievable
communication rate maximization problem is formulated by jointly optimizing the
transmit beamforming, the IOS phase shifts, and the duration of the joint S&C
stage. However, solving this ISAC optimization problem is highly non-trivial
since inaccurate estimation and measurement information renders the achievable
rate lack of closed-form expression. To handle this issue, we first derive a
closed-form expression of the achievable rate under uncertain location
information, and then unveil a sufficient and necessary condition for the
existence of the joint S&C stage to offer useful insights for practical system
design. Moreover, two typical scenarios including interference-limited and
noise-limited cases are analyzed.Comment: IEEE Transactions on Vehicular Technology, 2023. arXiv admin note:
text overlap with arXiv:2211.0420
Short-range ultrasonic communications in air using quadrature modulation
A study has been undertaken of ultrasonic communications methods in air, using a quadrature modulation method. Simulations were first performed to establish the likely performance of quadrature phase shift keying over the limited bandwidth available in an ultrasonic system. Quadrature phase shift keying modulation was then implemented within an experimental communication system, using capacitive ultrasonic sources and receivers. The results show that such a system is feasible in principle for communications over distances of several meters, using frequencies in the 200 to 400 kHz range
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