On the Spectral Efficiency of Energy Constrained Short-Range Communicating Systems

Binary offset carrier modulation is applied in several signals of the global navigation satellite system (GNSS). It enhanced the robustness of GNSS against the impact of multipath and make the compatibility of GNSS better. However, it has the main drawback of potentially giving biased measurements in acquisition and tracking. The technique we proposed is based on linear fitting with multi-correlator to accomplish unambiguous tracking. The coefficient of each correlator was deduced in this paper. The theoretical analysis and simulation results indicate that the proposed method can performs well on multipath and thermal noise.     

Use of continuous resistive material for fringe field elimination in a cylindrical mirror analyzer

The use of a continuous carbon-impregnated epoxy resistive material is investigated for the elimination of fringe fields in a cylindrical-mirror photoelectron energy analyzer. This fringe correction approach permits close coupling between the source inlet and the analyzer slits.     

Multicarrier CDMA techniques for future wideband wireless networks

In this paper, multicarrier techniques are considered in the context of the future wideband wireless networks. An overview of the different access schemes based on a combination of code division and multicarrier techniques, such as Multi-Carrier Code Division Multiple Access (MC-CDMA), Multi-Carrier Direct Sequence CDMA (MC-DS-CDMA) and Multi-Tone CDMA (MT-CDMA) is presented first. Afterwards, MC-CDMA systems are considered for the downlink of high rate cellular networks. The performance of different mono-user detection techniques are first analytically estimated and then compared with the help of Monte Carlo simulations for a Rayleigh channel. Simulation results on the performance of mono-user and multi-user detection techniques are also provided for Bad Urban (BU) Hilly Terrain (HT) and Vehicular UMTS channels. With regard to the channel coding, convolutional codes and turbo-codes are considered. Among others, a new linear detection technique named Global Minimum Mean Square Error Algorithm (GMMSE) is compared to multi-user Parallel Interference Cancellation detection technique. It is shown that GMMSE offers good performance especially for non-full load systems. Thus, the efficiency of MC-CDMA as a very promising multiple access and robust modulation scheme is successfully demonstrated for the downlink of the future wideband mobile networks.     

Adaptive spread-spectrum multicarrier multiple-access over wirelines

In this paper, we investigate the dynamic resource allocation adapted to spread-spectrum multicarrier multiple-access (SS-MC-MA) systems in a multiuser power line communication (PLC) context. The developed adaptive system is valid for uplink, downlink, as well as for indoor and outdoor communications. The studied SS-MC-MA system is based on classical multicarrier modulation like digital multitone (DMT), combined with a spread-spectrum (SS) component used to multiplex several information symbols of a given user over the same subcarriers. The multiple-access task is carried out using a frequency-division multiple-access (FDMA) approach so that each user is assigned one or more subcarrier sets. The number of subcarriers in each set is given by the spreading code length as in classical SS-MC-MA systems usually studied in the wireless context. We derive herein a new loading algorithm that dynamically handles the system configuration in order to maximize the data throughput. The algorithm consists in an adaptive subcarrier, code, bit, and energy assignment algorithm. Power-spectral density constraint due to spectral mask specifications is considered, as well as finite-order modulations. In that case, it is shown that SS-MC-MA combined with the proposed loading algorithm achieves higher throughput than DMT in a multiuser PLC context. Because of the finite granularity of the modulations, some residual energy is indeed wasted on each subcarrier of the DMT spectrum. The combining of a spreading component with DMT allows to merge these amounts of energy so that one or more additional bits can be transmitted in each subcarrier subset leading to significant throughput gain. Simulations have been run over measured PLC channel responses and highlight that the proposed system is all the more interesting than the signal-to-noise ratio is low.