: A novel detection technique for MC-CDMA systems based on the MMSE criterion applied per user is presented. Simulation results in a Rayleigh fading channel show very good performance, mainly for non full load systems. Introduction :Since 1993, Multi-Carrier Code Division Multiple Access (MC-CDMA) has been the subject of much research, and appears to be a very good candidate to support multimedia services in mobile radio communications [1]. The MC-CDMA transmitter spreads in the frequency domain the original data stream over different subcarriers using a given spreading code. For a synchronous system as the downlink mobile radio communication channel, the application of orthogonal codes such as Walsh-Hadamard codes guarantees the absence of Multiple Access Interference (MAI) in a Gaussian channel. However, through a frequency selective fading channel, all the subcarriers have different amplitude levels and different phase shifts, which results in a loss of the orthogonality among users and then generates MAI. So, after direct FFT and frequency deinterleaving, the received sequence must be "equalized" by using one tap adaptive equalizer per subcarrier to make up for the phase and amplitude distortions caused by the mobile radio channel. To combat the MAI, various basic detection techniques such as Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), Orthogonal Restoring Combining (ORC) or Minimum Mean Square Error (MMSE) may be used. This last technique, based on the MMSE criterion applied independently on each subcarrier [2] achieves better performance. This letter describes a novel detection technique based on the MMSE criterion applied per user which provides performance improvements, mainly for non full load systems.

The objective of this work is to quantify for the first time soot-related radiative heat transfer in opposed flow flame spread in microgravity. This article presents experimental results obtained in parabolic flight facilities. A flame is established over a solid cylindrical polyethylene coated metallic wire and spreads at a steady rate, in low velocity flow conditions allowed by the absence of buoyancy. Implementing the Broadband Modulated Absorption/Emission (B-MAE) technique, the two-dimensional fields of soot volume fraction and temperature are obtained for the first time in flame spread configuration over an insulated wire in microgravity. The consistency of the results is assessed by comparing results from independent experimental runs. From these fields, radiative losses attributed to soot in the flame are computed at each location. This map of radiative losses together with the profile of the wire surface are then used as inputs to a novel experimental approach that enables the assessment of soot radiative heat feedback to the wire. Results are extracted from a specific case of a flame propagating over a polyethylene coated Nickel-Chrome (NiCr) wire at nominal pressure. The oxidizer, composed of 19% oxygen and 81% nitrogen in volume is blown at opposed flow parallel to the wire at a velocity of 200 mm.s −1. This new approach provides the first detailed quantitative measurements which are required to check the relevance

A new optical setup and its associated post-processing have been designed in an effort to map soot related quantities in an axisymmetric flame spreading over solid samples in microgravity environment where setup compactness constraints are stringent. Extending the well-established spectral modulated absorption/emission (S-MAE) technique that uses lasers as light sources together with a sophisticated optical arrangement, LEDs have been associated with broadband optics to enable the broadband modulated absorption/emission (B-MAE) technique. The design and the cautious assessment of the original B-MAE setup are reported in the present paper. Algorithms that need to be reformulated for broadband integration are first validated retrieving both two-dimensional soot temperature and volume fraction fields produced by numerical simulations. Then, these fields are measured with both B-MAE and S-MAE techniques in a largely documented steady laminar non-premixed coflow ethylene/air flame established at normal gravity. Thus, outputs delivered by the B-MAE technique can be compared with those obtained with the S-MAE setup. Both soot temperature and volume fraction are shown to be decently measured by the B-MAE technique. As the spread of the non-buoyant flames to be investigated in the near future is especially driven by radiative heat transfer, the discrepancies between both techniques outputs are commented in the light of the fields of local radiative loss computed from the fields measured by both techniques. As a result, the fields delivered by the B-MAE technique are expected to provide ground-breaking insights into the control of flame spread in the absence of buoyancy, therefore manned spacecraft fire safety.