1,720,973 research outputs found
Rapid search algorithms for code acquisition in UWB impulse radio communications
No full textUltrawideband (UWB) impulse radio is an emerging technology suitable for high-rate tactical wireless communications. One of the crucial challenges for a connecting station remains the initial code acquisition, in a hostile propagation environment (e.g., urban combat). In this paper, we address the coarse acquisition of pseudonoise (PN) codes and propose algorithms for speeding up the acquisition process and/or reducing the complexity of the acquisition algorithm itself. Also, in the case of energy detection, we show that the front-end sampling rate may be reduced. An in-depth analysis, supported by simulations in the presence of multipath is presented, and the results discussed
Pseudo-chaotic communication method exploiting symbolic dynamics
No full textA pseudo-chaotic coding/modulation method. The coding method exploits symbolic dynamics of a chaotic map at the transmitter to encode data. The encoding synthesizes the chaotic map based upon the data to be transmitted. In a preferred embodiment, pseudo-chaotic iterates are generated from a digital implementation of a Bernoulli shift map. The output of the shift map is translated by a mapping, preferably implemented by a digital signal processor, to allow transitions between states in a transmitted signal to differ, and the translated map is used to drive a modulator (for example PPM, FSK, PSK, QAM, etc.). In the specific case of pulse-position modulation (PPM) the translated map is used to modulate pulse train positions within a periodic synchronization frame.; The preferred embodiment uses a shift register to implement an approximation of the Bernoulli shift map acting as a form of convolutional code with a number of states equal to the symbolic states defined on the chaotic map. A receiver may use fewer states and still decode the data signal, allowing receiver scalability
Orthogonal Convolutional Modulation for UWB-Impulse Radio Systems: Performance Analysis and Adaptive Schemes
No full textIn the context of UWB (ultra-wide band) Impulse Radio (IR) heterogeneous low data-rate networks, the need for coding/modulation schemes amenable of both coherent and noncoherent detection has emerged. The rationale is the potential coexistence of different classes of nodes, characterized by different complexity and performances. In such scenario, one of the main technical challenges is the design of efficient coding/modulation schemes incorporating forward error correction (FEC) and spreading capabilities, thus providing the necessary processing and coding gain, to guarantee robust communications. In this work, we introduce novel coding schemes exploiting the trellis structure of Orthogonal Convolutional Codes for generating time hopping sequences suitable for UWB-IR, while simultaneously mapping the information bits onto the transmitted waveforms.
Namely, we present a new class of Orthogonal Convolutional
Modulation (OCM) schemes, highlighting the trade-offs in terms of coherent vs. non-coherent detection performance. Then we develop an adaptive OCM scheme (AOCM) for application to broadcast transmission in heterogeneous UWB-IR networks, illustrating advantages in terms of energy savings and potential drawbacks
An Ultra-Wideband Impulse Radio-Based Control Layer for Enhanced Coexistence in Wireless LANs
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