14,518 research outputs found
Wi-Fi Teeter-Totter: Overclocking OFDM for Internet of Things
The conventional high-speed Wi-Fi has recently become a contender for
low-power Internet-of-Things (IoT) communications. OFDM continues its adoption
in the new IoT Wi-Fi standard due to its spectrum efficiency that can support
the demand of massive IoT connectivity. While the IoT Wi-Fi standard offers
many new features to improve power and spectrum efficiency, the basic physical
layer (PHY) structure of transceiver design still conforms to its conventional
design rationale where access points (AP) and clients employ the same OFDM PHY.
In this paper, we argue that current Wi-Fi PHY design does not take full
advantage of the inherent asymmetry between AP and IoT. To fill the gap, we
propose an asymmetric design where IoT devices transmit uplink packets using
the lowest power while pushing all the decoding burdens to the AP side. Such a
design utilizes the sufficient power and computational resources at AP to trade
for the transmission (TX) power of IoT devices. The core technique enabling
this asymmetric design is that the AP takes full power of its high clock rate
to boost the decoding ability. We provide an implementation of our design and
show that it can reduce the IoT's TX power by boosting the decoding capability
at the receivers
Speech Separation Using Partially Asynchronous Microphone Arrays Without Resampling
We consider the problem of separating speech sources captured by multiple
spatially separated devices, each of which has multiple microphones and samples
its signals at a slightly different rate. Most asynchronous array processing
methods rely on sample rate offset estimation and resampling, but these offsets
can be difficult to estimate if the sources or microphones are moving. We
propose a source separation method that does not require offset estimation or
signal resampling. Instead, we divide the distributed array into several
synchronous subarrays. All arrays are used jointly to estimate the time-varying
signal statistics, and those statistics are used to design separate
time-varying spatial filters in each array. We demonstrate the method for
speech mixtures recorded on both stationary and moving microphone arrays.Comment: To appear at the International Workshop on Acoustic Signal
Enhancement (IWAENC 2018
On a Hybrid Preamble/Soft-Output Demapper Approach for Time Synchronization for IEEE 802.15.6 Narrowband WBAN
In this paper, we present a maximum likelihood (ML) based time
synchronization algorithm for Wireless Body Area Networks (WBAN). The proposed
technique takes advantage of soft information retrieved from the soft demapper
for the time delay estimation. This algorithm has a low complexity and is
adapted to the frame structure specified by the IEEE 802.15.6 standard for the
narrowband systems. Simulation results have shown good performance which
approach the theoretical mean square error limit bound represented by the
Cramer Rao Bound (CRB)
Fast synchronization 3R burst-mode receivers for passive optical networks
This paper gives a tutorial overview on high speed burst-mode receiver (BM-RX) requirements, specific for time division multiplexing passive optical networks, and design issues of such BM-RXs as well as their advanced design techniques. It focuses on how to design BM-RXs with short burst overhead for fast synchronization. We present design principles and circuit architectures of various types of burst-mode transimpedance amplifiers, burst-mode limiting amplifiers and burst-mode clock and data recovery circuits. The recent development of 10 Gb/s BM-RXs is highlighted also including dual-rate operation for coexistence with deployed PONs and on-chip auto reset generation to eliminate external timing-critical control signals provided by a PON medium access control. Finally sub-system integration and state-of-the-art system performance for 10 Gb/s PONs are reviewed
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