1,723 research outputs found
Regulatory and Policy Implications of Emerging Technologies to Spectrum Management
This paper provides an overview of the policy implications of technological developments, and how these technologies can accommodate an increased level of market competition. It is based on the work carried out in the SPORT VIEWS (Spectrum Policies and Radio Technologies Viable In Emerging Wireless Societies) research project for the European Commission (FP6)spectrum, new radio technologies, UWB, SDR, cognitive radio, Telecommunications, regulation, Networks, Interconnection
Joint beamforming and channel estimation for pilot-aided WCDMA systems
The problem of joint beamforming and channel estimation for multi-rate multi-code systems is addressed. Usual schemes perform this filtering/estimation operation making use of a training sequence time-multiplexed with the transmitted data. However if pilot and traffic signals are transmitted simultaneously using distinct code allocation-as it is the case in recent standards such as cdma2000 or WCDMA-these schemes tend to fail. This paper proposes semi-blind techniques to overcome the uplink auto-interfering effects of such systems. It is shown that the semi-blind approach yields substantially better performance results thanks to the implicit modeling of the unknown traffic data.Peer ReviewedPostprint (published version
Performance degradation due to multipath noise for narrowband OFDM systems: channel-based analysis and experimental determination
The performance of OFDM systems over a multipath channel can strongly degrade due to the propagation delay spread. The distortion of the received signal over the fast Fourier transform window is referred to as multipath noise. This work aims to analytically determine the performance loss due to multipath noise as a function of OFDM and channel parameters for narrowband OFDM systems. First, it is investigated whether it is possible to describe the multipath noise, varying over different OFDM packets due to the temporal variation of the channel, by an effective noise factor F-delay, from which the loss factor is directly determined. Second, the theory of room electromagnetics is applied to develop a closed-form expression for F-delay as a function of the OFDM and reverberation parameters. This analytical method is validated with excellent agreement. Finally, the loss factor is determined for IEEE 802.11 based on channel measurements in two large conference rooms, providing values up to 19 dB for an 800 ns cyclic prefix length
Parametric channel estimation for massive MIMO
Channel state information is crucial to achieving the capacity of
multi-antenna (MIMO) wireless communication systems. It requires estimating the
channel matrix. This estimation task is studied, considering a sparse channel
model particularly suited to millimeter wave propagation, as well as a general
measurement model taking into account hybrid architectures. The contribution is
twofold. First, the Cram{\'e}r-Rao bound in this context is derived. Second,
interpretation of the Fisher Information Matrix structure allows to assess the
role of system parameters, as well as to propose asymptotically optimal and
computationally efficient estimation algorithms
Ultra wideband: applications, technology and future perspectives
Ultra Wide Band (UWB) wireless communications offers a radically different approach to wireless communication compared to conventional narrow band systems. Global interest in the technology is huge. This paper reports on the state of the art of UWB wireless technology and highlights key application areas, technological challenges, higher layer protocol issues, spectrum operating zones and future drivers. The majority of the discussion focuses on the state of the art of UWB technology as it is today and in the near future
Active Terminal Identification, Channel Estimation, and Signal Detection for Grant-Free NOMA-OTFS in LEO Satellite Internet-of-Things
This paper investigates the massive connectivity of low Earth orbit (LEO)
satellite-based Internet-of-Things (IoT) for seamless global coverage. We
propose to integrate the grant-free non-orthogonal multiple access (GF-NOMA)
paradigm with the emerging orthogonal time frequency space (OTFS) modulation to
accommodate the massive IoT access, and mitigate the long round-trip latency
and severe Doppler effect of terrestrial-satellite links (TSLs). On this basis,
we put forward a two-stage successive active terminal identification (ATI) and
channel estimation (CE) scheme as well as a low-complexity multi-user signal
detection (SD) method. Specifically, at the first stage, the proposed training
sequence aided OTFS (TS-OTFS) data frame structure facilitates the joint ATI
and coarse CE, whereby both the traffic sparsity of terrestrial IoT terminals
and the sparse channel impulse response are leveraged for enhanced performance.
Moreover, based on the single Doppler shift property for each TSL and sparsity
of delay-Doppler domain channel, we develop a parametric approach to further
refine the CE performance. Finally, a least square based parallel time domain
SD method is developed to detect the OTFS signals with relatively low
complexity. Simulation results demonstrate the superiority of the proposed
methods over the state-of-the-art solutions in terms of ATI, CE, and SD
performance confronted with the long round-trip latency and severe Doppler
effect.Comment: 20 pages, 9 figures, accepted by IEEE Transactions on Wireless
Communication
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