1,720,987 research outputs found
Multi-Antenna Noncoherent ML Synchronization for UWB-IR Faded Channels
No full textThis contribution focuses on the maximum likelihood (ML) noncoherent synchronization of multi-antenna transceivers working in faded environments and employing ultra-wideband impulse radio (UWB-IR) transmit technology. In particular, the Cramer-Rao bound (CRB) is derived for the general case of multiple input multiple output (MIMO) UWB-IR systems and used to compare the ultimate performance of three basic transmit schemes, thereinafter referred to as single input multiple output (SIMO), MIMO equal signaling (MIMO-ES), and MIMO orthogonal signaling (MIMO-OS) ones. Thus, the noncoherent ML synchronizer is developed for the better performing transmit scheme (i.e., the SIMO one) and its performance is evaluated under both signal acquisition and tracking operating conditions. The performance gain in the synchronization of UWB-IR signals arising by the utilization of the multi-antenna technology is also evaluated. © 2006 KICS
Noncoherent Synchronization of UWB-IR Multiple Antenna Multipath Channels
No full textto appear in 2009 on IEEE Transactions on Vehicular Technolog
Maximum-Rate Node-Selection for Power-Limited Multi-Antenna Relay Backbones
No full textWireless Mesh Networks (WMNs) are envisioned for extending the coverage of WLANs by interconnecting the underlying Access Points (APs) via high-capacity wireless backbones. Since the ultimate goal of a WMN is to provide Internet connectivity to residential clients, WMN traffic is mainly routed over the backbone either toward the Internet Gateways (IGWs) or from the IGWs to the APs. In principle, the transport capacity of a WMN can further be upgraded by equipping the underlying backbone routers with Multiantenna (MA) radio modules. Motivated by the above consideration, in this paper, we focus on the optimized node selection (e.g., path-routing) over MA mesh backbones when the target is to maximize the end-to-end routed information rate subject to a constraint on the total power available for the relays. Under the assumption of Rayleigh-distributed block fading, we assume that point-to-point capacity-achieving Space-Time Codes (STCs) are used for the single-hop link. At first, we tackle the routing problem when neither Interference Mitigation (IM) nor Transmit Beamforming (TB) is performed at the relay nodes, and then, we extend the analysis to the cases when IM and/or TB are also carried out. The effects of Channel-State-Information (CSI) possibly available at the relay nodes are also investigated. So doing, we are able to gain insight about the combined effect of spatial multiplexing and IM capabilities of the overall MA architecture on both end-to-end capacity and access medium performance of the considered WMN
A new family of optimized Orthogonal Space-Time Codes for PPM-based MIMO Systems with Imperfect channel estimates
No full textIn this contribution, we develop a single Multiple-Input Multiple Output (MIMO) transceiver for Orthogonal PPM (OPPM) data transmitted over (baseband) faded MIMO channels with a priori unknown path-gains. The signaling-scheme we adopt allows to equip the Maximum-Likelihood receiver with reliable estimates of the (possibly time-varying) MIMO channel, without reducing the conveyed information throughput. Hence, after evaluating the performance of the proposed transceiver via a suitable version of the Union-Chernoff Bound, we introduce a novel family of unitary orthogonal Space-Times Block Codes (e.g., the Space-Time OPPM codes), that are able to attain both maximum diversity and coding gains. Afterwards, we present closed-form formulas for evaluating the SNR loss induced by mistiming effects possibly impairing the received signals. Lastly, we report several numerical results supporting both the medium/long coverage ranges attained by the proposed transceiver in outdoor applications and its performance robustness against correlated channel fading, mistiming effects and degradation induced by dense-multipath fading. © 2007 Springer Science+Business Media, LLC
Optimal MIMO UWB-IR Transceiver for Nakagami-fading Poisson-Arrivals
No full textIn this contribution, we develop a (novel) family of Multiple-Input Multiple-Output (MIMO) UWB Impulse-Radio (UWB-IR) transceivers for Orthogonal PPM-modulated (OPPM) coded transmissions over (baseband) multipath-faded MIMO channels. To by-pass expensive channel-estimation procedures, the MIMO channel path-gains are assumed to he fully unknown at the receiver. Thus, according to the UWB-IR. statistical channel-models currently reported in the literature for both indoor/ outdoor application scenarios, we develop and analyze three versions of the resulting noncoherent transceiver, that are optimal for Nakagami, Gaussian, and Log-normal distributed channel-gains, respectively. As dictated by the Saleh-Valenzuela (SV) UWB model, the resulting noncoherent Maximum-Likelihood (ML) Decoder explicitly accounts for the Poisson-distribution of the path-arrivals. Hence, after analytically evaluating the performance of the proposed noncoherent transceiver via suitable versions of the Union-Chernoff bound, we prove that the family of Space-Time OPPM (STOPPM) recently presented in the Literature is able to attain full-diversity in the considered multipath-affected application scenario. To corroborate the carried out performance analysis, we report several numerical results supporting both the medium/ long coverage ranges attained by the proposed STOPPM-coded noncoherent transceiver, and its performance robusta against the degrading effects induced by Inter-Pulse-Interference (IPI), spatially-correlated multipath fading and mistiming. © 2008 Academy Publisher
Il Piano degli Spostamenti Casa-Lavoro (PSCL): valutazioni monetarie delle esternalità negative generate della mobilità privata. Il caso di Parma.
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Competitively Optimal Space-Division Broadband Multiple Access for Multi-Antenna ''ad-hoc'' 4G WLAN
No full textA Distributed Power-Allocation and Signal Shaping Game for Multiple Antenna ad-hoc networks impaired by Multiple-Access Interference
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