No abstract

The exponential growth in traffic demand over wireless cellular networks challenges the operators' business model as it requires significant investments in infrastructure. Multi-layers deployment, i.e., heterogeneous networks (HetNet), is one of the solutions operators are deploying to overcome this "capacitycrunch" phenomena. Yet even by adopting HetNet operators are still required to invest in network planning, sites deployment, maintenance and on-going operational costs. This paper proposes a novel cost-effective HetNet deployment approach based on nomadic vehicular relay nodes (VeRNs). VeRN downlink performance are analyzed in two deployment models, which focus on VeRN impact on the network as a function of its placement. The 2-hop relay link via a VeRN is analyzed compared to the cellular direct-link for the proposed deployment models investigating both link level and spectral efficiency (SE) aspects. The analysis is based on extensive simulations with an indicative proposed figure of merit. The results show significant improvement in link level as well as substantial increase in spectral efficiency when using VeRNs across a set of deployment parameters.

No abstract

INTRODUCTIONAttitude determination systems are important in many fields, such as land static measurements (geodesy) and mobile applications, as well as in satellites for communications. While attitude finding was traditionally based on inertial navigation systems (INS), in the last decades several navigation equipment manufacturers have developed GPS-based solutions for the problem of orientation finding. GPS-based attitude determination systems have been tested for land, marine, air, and space vehicles [1 -4]. These systems have succeeded in providing comparatively low-cost and highly stable solutions.Multipath effects on GPS receivers for positioning applications, such as geodesy, are investigated and reported in [5]. A geometrical model is presented and applied to reduce the multipath interference in a static receiver utilizing multiple antennas [6].It is well known that the accuracy of a GPS-based attitude determination system is considerably limited by multipath interference [7 -10]. A GPS-based attitude determination system is basically a differential phase measurement apparatus. Multipath affects the receiver operation when a few delayed echoes of the desired signal are received and combined with the desired signal. The signal mixture induces phase error, which results in turn in large navigation errors.A method for calibrating multipath interference is presented in [8]. The method of [8] is based on an approximation of the multipath interference using a sum of spherical harmonic functions. A different mitigation technique, based on the assumption of low dynamics, is presented in [9]. In [9], the multipath interference effect on the attitude measurements is modeled by a sum of sinusoids.A different approach to the problem is presented in [10], where the multipath plus thermal noise is modeled as a first-order Gauss-Markov process. This statistical model is suitable for applying a Kalman filter [11]. Both methods [9,10] assume that the multipath model order is known a priori.Recently, a new method for calibrating multipath interference for a GPS-based attitude determination system was proposed [12]. This method, known as the Sky Map Method, shows improvement in and is especially suitable for a satellite in orbit. This is due to a relatively static environment surrounding the receiver antenna array. In this case, the platform often experience a periodic dynamics, which makes the problem setting similar to a static scenario.A new postprocessing iterative algorithm for multipath interference mitigation is presented in this paper. The proposed algorithm is based on separation of the measured attitude into time sections where the multipath interference acts uniformly.

In this paper new algorithms for coherent and noncoherent code tracking loops are presented. The algorithms are relatively simple and hardware reduced. Functional identity to the traditionally optimal earlglate (E-L) code tracking loops is presented. The new structures are computationally eficient by reducing substantially the multiply and accumulate (MA C) operations per time unit. A s a result, reduced power consumption schemes are obtained.