This paper aims to
study the performance of low complexity adaptive
resource allocation in the downlink of OFDMA
systems with fixed or variable rate requirements
(with fairness consideration). Two suboptimal
resource allocation algorithms are proposed
using the simplifying assumption of transmit
power over the entire bandwidth. The objective
of the
first algorithm is to maximize the total throughput while
maintaining rate proportionality among the users. The proposed
suboptimal algorithm prioritizes the user with the highest
sensitivity to the subcarrier allocation, and the variance over the
subchannel gains is used to define the sensitivity of each user.
The second algorithm concerns rate adaptive resource allocation in
multiuser systems with fixed rate constraints. We propose a
suboptimal joint subchannel and power allocation algorithm which
prioritizes the users with the highest required data rates. The main
feature of this algorithm is its low complexity while achieving
the rate requirements.
Multipath is still one of the major error sources that degrades the accuracy of GPS positioning. The amount of multipath is highly dependent on the antenna's environment, which makes it difficult to isolate. Usually there is at least one in-view satellite which is more susceptible to multipath, particularly the one with the lowest elevation angle. To increase the positioning the best satellites must be selected (i.e. by least square or multipath mitigation) for computing a position. In this paper we propose an algorithm which picks up the best satellites (when there are more than four satellites in view) based on wavelet analysis for calculating a position. In this experiment, code and carrier measurements were collected in 15-minute segments by exploiting a single frequency (L1), stationary, navigation-grade receiver in a high-multipath environment. The magnitudes of these pseudoranges were often inflated by multipath error. We then post-processed the received data by applying wavelet filtering to the residuals (code minus carrier) to approximate the multipath values, and compute the receiver's position based on the selected satellites. Satellites were selected based on the residual values. To compare the results with the raw measurements, statistical elements were computed. The results showed significant improvement in variance of the estimated positions and, most importantly, a normalization of the data scatter-distribution was observed.
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