2,134 research outputs found
A Signal-Space Analysis of Spatial Self-Interference Isolation for Full-Duplex Wireless
The challenge to in-band full-duplex wireless communication is managing
self-interference. Many designs have employed spatial isolation mechanisms,
such as shielding or multi-antenna beamforming, to isolate the
self-interference wave from the receiver. Such spatial isolation methods are
effective, but by confining the transmit and receive signals to a subset of the
available space, the full spatial resources of the channel be under-utilized,
expending a cost that may nullify the net benefit of operating in full-duplex
mode. In this paper we leverage an antenna-theory-based channel model to
analyze the spatial degrees of freedom available to a full-duplex capable base
station, and observe that whether or not spatial isolation out-performs
time-division (i.e. half-duplex) depends heavily on the geometric distribution
of scatterers. Unless the angular spread of the objects that scatter to the
intended users is overlapped by the spread of objects that backscatter to the
base station, then spatial isolation outperforms time division, otherwise time
division may be optimal.Comment: To Appear at 2014 International Symposium on Information Theor
Spatial degrees-of-freedom in large-array full-duplex: the impact of backscattering
The key challenge for in-band full-duplex wireless communication is managing self-interference. Many designs have employed spatial isolation mechanisms, such as shielding or multi-antenna beamforming, to isolate the self-interference waveform from the receiver. Because such spatial isolation methods confine the transmit and receive signals to a subset of the available space, the full spatial resources of the channel may be under-utilized, expending a cost that may nullify the net benefit of operating in full-duplex mode. In this paper, we leverage an antenna-theory-based channel model to analyze the spatial degrees of freedom available to a full-duplex capable base station. We observe that whether or not spatial isolation out-performs time-division (i.e., half-duplex) depends heavily on the geometric distribution of scatterers. Unless the angular spread of the objects that scatter to the intended users is overlapped by the spread of objects that backscatter to the base station, then spatial isolation outperforms time division, otherwise time division may be optimal
Sum Throughput Maximization in Multi-Tag Backscattering to Multiantenna Reader
Backscatter communication (BSC) is being realized as the core technology for
pervasive sustainable Internet-of-Things applications. However, owing to the
resource-limitations of passive tags, the efficient usage of multiple antennas
at the reader is essential for both downlink excitation and uplink detection.
This work targets at maximizing the achievable sum-backscattered-throughput by
jointly optimizing the transceiver (TRX) design at the reader and
backscattering coefficients (BC) at the tags. Since, this joint problem is
nonconvex, we first present individually-optimal designs for the TRX and BC. We
show that with precoder and {combiner} designs at the reader respectively
targeting downlink energy beamforming and uplink Wiener filtering operations,
the BC optimization at tags can be reduced to a binary power control problem.
Next, the asymptotically-optimal joint-TRX-BC designs are proposed for both low
and high signal-to-noise-ratio regimes. Based on these developments, an
iterative low-complexity algorithm is proposed to yield an efficient
jointly-suboptimal design. Thereafter, we discuss the practical utility of the
proposed designs to other application settings like wireless powered
communication networks and BSC with imperfect channel state information.
Lastly, selected numerical results, validating the analysis and shedding novel
insights, demonstrate that the proposed designs can yield significant
enhancement in the sum-backscattered throughput over existing benchmarks.Comment: 17 pages, 5 figures, accepted for publication in IEEE Transactions on
Communication
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