Abstract:The reliability of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) vehicle-to-vehicle (V2V) communication in real road environments suffers from fading, shadowing and the hidden terminal problem, especially for non-line-of sight (NLOS) areas such as intersections. In order to improve the communication reliability, a CSMA/CA based vehicle-roadside-vehicle broadcast relay network was proposed and its effectiveness has been shown through simulations. However, the potential of such a network has not been well analyzed and optimized. In this paper, a theoretical model is proposed to analyze the performance of the broadcast relay network in detail. In order to fit real vehicular environments, the model assumes a typical crossroad and takes into account fading, shadowing, the hidden terminal problem and the capture effect. The influence of system parameters including position of nodes, carrier sense threshold and RF frequency band on the reliability of the network is studied based on the model. The accuracy of the proposed analytical model is confirmed by simulations. The analytical model and the obtained results are useful for the design of vehicular broadcast networks to select appropriate system parameters.
Macrophage inflammation protein-3alpha (MIP-3alpha) is a chemokine expressed in inflamed tissue and capable of inducing migration of immature dendritic cells (DCs) or Langerhans cells. We postulated that conditioning vaccination sites with MIP-3alpha might enhance the efficacy of subsequently administered DC-based cancer vaccines. Our results demonstrate that subcutaneously injection of irradiated tumor cells expressing MIP-3alpha induces substantial cell infiltration to the injection site. Vaccination of irradiated tumor cells expressing MIP-3alpha followed by DCs pulsed with irradiated tumor cells can effectively suppress tumor growth in animals, which is significantly better than vaccination with irradiated MIP-3alpha-producing tumor cells or DCs pulsed with tumor cells alone. The protective effect was most evident when the MIP-3alpha-producing tumor cells and DC-based vaccines were injected at the same site. These results support the notion that this combination vaccination strategy might generate a more effective immune response to suppress the growth of tumor cells in animals.
Abstract-Semi-blind space-time equalisation is considered for dispersive multiple-input multiple-output systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, approximately equal to the dimension of the space-time equaliser (STE), are first utilised to provide a rough initial least squares estimate of the STE's weight vector. A gradient-Newton-type concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the STE. The proposed semi-blind adaptive STE is capable of converging fast and accurately to the optimal minimum mean square error STE solution.
I. INTRODUCTIONWith the aid of smart antenna arrays and by exploiting both the space and time dimensions, space-time processing is capable of effectively improving the achievable system capacity, coverage and quality of service by suppressing both intersymbol interference and co-channel interference [1]- [7]. In this contribution, we consider space-division multiple-access (SDMA) induced frequency selective multiple-input multipleoutput (MIMO) systems that employ quadrature amplitude modulation (QAM) signalling. A bank of space-time equalisers (STEs) [8]-[14] form the multiuser receiver. Adaptive implementation of STE can be realised using the training-based least mean square (LMS) or recursive least squares (RLS) algorithm [15]. However, a large number of training symbols is required to adapt a STE, which considerably reduces the achievable system throughput. Blind adaptive methods may be applied to adjust a STE, which does not require training symbols and, therefore, does not reduce the achievable system throughput. However, blind methods require high computational complexity and, moreover, they result in unavoidable estimation and decision ambiguities [16], [17], which can only be resolved with the aid of a few training symbols. At the cost of requiring a few training symbols, semi-blind schemes can avoid the estimation and decision ambiguity problem and are computationally simpler than their blind counterparts.Many semi-blind methods have been proposed for narrowband MIMO systems [18]-[24]. In particular, the work of [24] has developed a semi-blind spatial equalisation scheme for narrowband MIMO systems that employ QAM signalling. In this semi-blind method, a few training symbols, approximately equal to the dimension of the spatial equaliser, are first used to provide a rough least squares (LS) estimate of the spatial equaliser's weight vector. The stochastic-gradient (SG) based constant modulus algorithm (CMA) and soft decision-directed (SDD) scheme, originally developed for blind equalisation of
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