61 research outputs found
An Empirical Air-to-Ground Channel Model Based on Passive Measurements in LTE
In this paper, a recently conducted measurement campaign for
unmanned-aerial-vehicle (UAV) channels is introduced. The downlink signals of
an in-service long-time-evolution (LTE) network which is deployed in a suburban
scenario were acquired. Five horizontal and five vertical flight routes were
considered. The channel impulse responses (CIRs) are extracted from the
received data by exploiting the cell specific signals (CRSs). Based on the
CIRs, the parameters of multipath components (MPCs) are estimated by using a
high-resolution algorithm derived according to the space-alternating
generalized expectation-maximization (SAGE) principle. Based on the SAGE
results, channel characteristics including the path loss, shadow fading, fast
fading, delay spread and Doppler frequency spread are thoroughly investigated
for different heights and horizontal distances, which constitute a stochastic
model.Comment: 15 pages, submitted version to IEEE Transactions on Vehicular
Technology. Current status: Early acces
Low Altitude Air-to-Ground Channel Characterization in LTE Network
Low altitude unmanned aerial vehicle (UAV)-aided applications are promising in the future generation communication systems. In this paper, a recently conducted measurement campaign for characterizing the low-altitude air-to-ground (A2G) channel in a typical Long Term Evolution (LTE) network is introduced. Five horizontal flights at the heights of 15, 30, 50, 75, and 100 m are applied, respectively. The realtime LTE downlink signal is recorded by using the Universal Software Radio Peripheral (USRP)-based channel sounder onboard the UAV. Channel impulse responses (CIRs) are extracted from the cell specific signals in the recorded downlink data. To shed lights on the physical propagation mechanisms, propagation graph simulation is exploited. Moreover, path loss at different heights are investigated and compared based on the empirical data. The simulated and empirical results provide valuable understanding of the low altitude A2G channels
Google USM: Scaling Automatic Speech Recognition Beyond 100 Languages
We introduce the Universal Speech Model (USM), a single large model that
performs automatic speech recognition (ASR) across 100+ languages. This is
achieved by pre-training the encoder of the model on a large unlabeled
multilingual dataset of 12 million (M) hours spanning over 300 languages, and
fine-tuning on a smaller labeled dataset. We use multilingual pre-training with
random-projection quantization and speech-text modality matching to achieve
state-of-the-art performance on downstream multilingual ASR and speech-to-text
translation tasks. We also demonstrate that despite using a labeled training
set 1/7-th the size of that used for the Whisper model, our model exhibits
comparable or better performance on both in-domain and out-of-domain speech
recognition tasks across many languages.Comment: 20 pages, 7 figures, 8 table
A Comparative Study on Transformer vs RNN in Speech Applications
Sequence-to-sequence models have been widely used in end-to-end speech
processing, for example, automatic speech recognition (ASR), speech translation
(ST), and text-to-speech (TTS). This paper focuses on an emergent
sequence-to-sequence model called Transformer, which achieves state-of-the-art
performance in neural machine translation and other natural language processing
applications. We undertook intensive studies in which we experimentally
compared and analyzed Transformer and conventional recurrent neural networks
(RNN) in a total of 15 ASR, one multilingual ASR, one ST, and two TTS
benchmarks. Our experiments revealed various training tips and significant
performance benefits obtained with Transformer for each task including the
surprising superiority of Transformer in 13/15 ASR benchmarks in comparison
with RNN. We are preparing to release Kaldi-style reproducible recipes using
open source and publicly available datasets for all the ASR, ST, and TTS tasks
for the community to succeed our exciting outcomes.Comment: Accepted at ASRU 201
Healthy Breeding Service System of Vannamei Based on TD-SCDMA
Vannamei is recognized as one of the excellent variety of prawns in the world and has sanguine development foreground. However, the popularization of healthy farming technology in China is limited because of the weak agricultural information infrastructure. This paper takes full advantages of mobile network infrastructure and the features of surfing the Internet with smart phone, designs and implements the healthy breeding service system of vannamei based on TD-SCDMA, WAP and sentence similarity algorithm. Farmers can obtain real-time knowledge of healthy breeding, download training videos and receive early-warning information from the system. Furthermore, farmers can get SMS messages which contain video download addresses or early-warning information URLs chosen by users’ customized interests. This system proposes a better way for farmers to get the breeding knowledge and it can provide service whenever and wherever users want
- …