8 research outputs found
Linear Block Coding for Efficient Beam Discovery in Millimeter Wave Communication Networks
The surge in mobile broadband data demands is expected to surpass the
available spectrum capacity below 6 GHz. This expectation has prompted the
exploration of millimeter wave (mm-wave) frequency bands as a candidate
technology for next generation wireless networks. However, numerous challenges
to deploying mm-wave communication systems, including channel estimation, need
to be met before practical deployments are possible. This work addresses the
mm-wave channel estimation problem and treats it as a beam discovery problem in
which locating beams with strong path reflectors is analogous to locating
errors in linear block codes. We show that a significantly small number of
measurements (compared to the original dimensions of the channel matrix) is
sufficient to reliably estimate the channel. We also show that this can be
achieved using a simple and energy-efficient transceiver architecture.Comment: To appear in the proceedings of IEEE INFOCOM '1
Codebook-based Uplink Transmission Enhancement in 5G Advanced: Sub-band Precoding
The transformative enhancements of fifth-generation (5G) mobile devices bring
about new challenges to achieve better uplink (UL) performance. Particularly,
in codebook-based transmission, the wide-band (WB) precoding and the legacy UL
codebook may become main bottlenecks for higher efficient data transmission. In
this paper, we investigate the codebook-based UL single-layer transmission
performance using fully coherent antenna ports in the context of sub-band (SB)
precoding. We analyze the SB precoder selection criteria and design an UL
codebook used for SB precoding by increasing the number of relative phase
shifts of each port. Via link-level simulations, we verify that the UL SB
precoding can improve up to 2 dB performance gain in terms of the block error
rate (BLER) compared with the UL WB precoding which is the current UL precoding
scheme. We also show that UL performance gain is sensitive to the SB size
selection as well as the relative phase shift diversity.Comment: This work has been accepted by IEEE VCC 2023. 5 pages, 7 figure
Continuous Beam Alignment for Mobile MIMO
Millimeter-wave transceivers use large antenna arrays to form narrow
high-directional beams and overcome severe attenuation. Narrow beams require
large signaling overhead to be aligned if no prior information about beam
directions is available. Moreover, beams drift with time due to user mobility
and may need to be realigned. Beam tracking is commonly used to keep the beams
tightly coupled and eliminate the overhead associated with realignment. Hence,
with periodic measurements, beams are adjusted before they lose alignment. We
propose a model where the receiver adjusts beam direction "continuously" over
each physical-layer sample according to a carefully calculated estimate of the
continuous variation of the beams. In our approach, the change of direction is
updated using the rate variation prediction of beam angles via three different
solutions. Our approach incurs no additional overhead in pilots, yet, the
performance of beam tracking is improved significantly. Numerical results
reveal an SNR enhancement associated with reducing the MSE of the beam
directions. In addition, our approach reduces the pilot overhead by 60% and up
to 87% while achieving a similar total tracking duration as the
state-of-the-art.Comment: The paper is accepted to be published by IEEE Transactions on
Wireless Communication
A hardware implementation for efficient spectrum access in cognitive radio networks
Opportunistic spectrum access is a propitious technique to overcome the under-utilization of spectrum bands. In this work, we design an experimental test-bed for evaluating an un-slotted spectrum access scheme under real indoor environment conditions. To this end, we use the USRP software defined radio platform along with the GNURadio software that incorporates the PHY and MAC functions and modules. Our contribution is multi-fold. First, we design a MAC protocol to integrate the packet based transmission of the coexisting PU/SU network, while compensating for spectrum sensing imperfection as well as collision detection faults. Second, we evaluate the USRP-induced latency (delay) and show that it has random behavior.We work around it to obtain a fixed packet transmission time which is crucial for the channel access scheme realization and evaluation. Third, we perform helping experiments to quantify the spectrum sensing imperfection in terms of false alarm and detection probabilities. We also quantify the imperfection in collision detection. Finally, we evaluate the performance of the whole channel access scheme and compare its results to the classical sense-transmit scheme. We show that 28.5% increase in SU throughput can be achieved for the same PU packet collision rate.Scopu