307 research outputs found
DSP Linearization for Millimeter-Wave All-Digital Receiver Array with Low-Resolution ADCs
Millimeter-wave (mmWave) communications and cell densification are the key
techniques for the future evolution of cellular systems beyond 5G. Although the
current mmWave radio designs are focused on hybrid digital and analog receiver
array architectures, the fully digital architecture is an appealing option due
to its flexibility and support for multi-user multiple-input multiple-output
(MIMO). In order to achieve reasonable power consumption and hardware cost, the
specifications of analog circuits are expected to be compromised, including the
resolution of analog-to-digital converter (ADC) and the linearity of
radio-frequency (RF) front end. Although the state-of-the-art studies focus on
the ADC, the nonlinearity can also lead to severe system performance
degradation when strong input signals introduce inter-modulation distortion
(IMD). The impact of RF nonlinearity becomes more severe with densely deployed
mmWave cells since signal sources closer to the receiver array are more likely
to occur. In this work, we design and analyze the digital IMD compensation
algorithm, and study the relaxation of the required linearity in the RF-chain.
We propose novel algorithms that jointly process digitized samples to recover
amplifier saturation, and relies on beam space operation which reduces the
computational complexity as compared to per-antenna IMD compensation.Comment: 2019 IEEE 20th International Workshop on Signal Processing Advances
in Wireless Communications (SPAWC
Compressive Identification of Active OFDM Subcarriers in Presence of Timing Offset
In this paper we study the problem of identifying active subcarriers in an
OFDM signal from compressive measurements sampled at sub-Nyquist rate. The
problem is of importance in Cognitive Radio systems when secondary users (SUs)
are looking for available spectrum opportunities to communicate over them while
sensing at Nyquist rate sampling can be costly or even impractical in case of
very wide bandwidth. We first study the effect of timing offset and derive the
necessary and sufficient conditions for signal recovery in the oracle-assisted
case when the true active sub-carriers are assumed known. Then we propose an
Orthogonal Matching Pursuit (OMP)-based joint sparse recovery method for
identifying active subcarriers when the timing offset is known. Finally we
extend the problem to the case of unknown timing offset and develop a joint
dictionary learning and sparse approximation algorithm, where in the dictionary
learning phase the timing offset is estimated and in the sparse approximation
phase active subcarriers are identified. The obtained results demonstrate that
active subcarrier identification can be carried out reliably, by using the
developed framework.Comment: To appear in the proceedings of the IEEE Global Communications
Conference (GLOBECOM) 201
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