850 research outputs found
New expression for the functional transformation of the vector Cramér-Rao lower bound
Assume that it is desired to estimate α = f(θ), where f(·) is an r-dimensional function. This paper derives the general expression for the functional transformation of the vector Cramér-Rao lower bound (CRLB). The derived bound is a tight lower bound on the estimation of uncoupled parameters, i.e., parameters that can be estimated separately. Unlike previous results in the literature, this new expression is not dependent on the inverse of the Fisher's information matrix (FIM) of the untransformed parameters, θ. Thus, it can be applied to scenarios where the FIM for θ is ill-conditioned or singular. Finally, as an application, the derived transformation is applied to determine the exact CRLB for estimation of channel parameters in amplify-and-forward relaying networks.This research was supported under Australian Research Council’s Discovery Projects funding scheme (project number DP110102548)
Joint Resource Optimization for Multicell Networks with Wireless Energy Harvesting Relays
This paper first considers a multicell network deployment where the base
station (BS) of each cell communicates with its cell-edge user with the
assistance of an amplify-and-forward (AF) relay node. Equipped with a power
splitter and a wireless energy harvester, the self-sustaining relay scavenges
radio frequency (RF) energy from the received signals to process and forward
the information. Our aim is to develop a resource allocation scheme that
jointly optimizes (i) BS transmit powers, (ii) received power splitting factors
for energy harvesting and information processing at the relays, and (iii) relay
transmit powers. In the face of strong intercell interference and limited radio
resources, we formulate three highly-nonconvex problems with the objectives of
sum-rate maximization, max-min throughput fairness and sum-power minimization.
To solve such challenging problems, we propose to apply the successive convex
approximation (SCA) approach and devise iterative algorithms based on geometric
programming and difference-of-convex-functions programming. The proposed
algorithms transform the nonconvex problems into a sequence of convex problems,
each of which is solved very efficiently by the interior-point method. We prove
that our algorithms converge to the locally optimal solutions that satisfy the
Karush-Kuhn-Tucker conditions of the original nonconvex problems. We then
extend our results to the case of decode-and-forward (DF) relaying with
variable timeslot durations. We show that our resource allocation solutions in
this case offer better throughput than that of the AF counterpart with equal
timeslot durations, albeit at a higher computational complexity. Numerical
results confirm that the proposed joint optimization solutions substantially
improve the network performance, compared with cases where the radio resource
parameters are individually optimized
Microbial dynamics during various activities in residential areas of Lahore, Pakistan
Bioaerosols are ubiquitous in the atmosphere with their levels affected by a variety of environmental factors as well as
type of activities being carried out at any specific time. The present study investigated how indoor activities influence
bioaerosol concentrations in five residential houses of Lahore. Agar coated petri plates were exposed face upwards for
twenty minutes in kitchens and living rooms during activity and non-activity periods. The temperature and relative
humidity levels were noted as well. The bioaerosol concentrations in kitchens during the activity time ranged between
1022 to 4481 cfu/m3 and in living rooms from 1179 to 3183 cfu/m3 . Lower values were observed during non-activity
periods. A paired-t test revealed a significant difference in bacterial loads during activity and non-activity times in both
micro-environments (p = 0.038 in kitchen and p = 0.021 in living room). The predominant species identified were
Micrococcus spp., Staphylococcus spp., and Bacillus spp. which are a common constituent of the indoor environment
and are known to be opportunistic pathogens as well
Measurement of NO2 indoor and outdoor concentrations in selected public schools of Lahore using passive sampler
Higher levels of NO2 are a danger to human health especially for children. A seven day study was carried to find out the
ambient concentrations of NO2in 27 schools of Lahore with the help of passive samplers. In each school three sites were
selected, viz: laboratory, corridor and outdoors. After 7 days exposure the tubes were subjected to spectrophotometric
analysis. Results showed that the maximum values measured in laboratory, outdoor and corridors were 376µg/m3 ,
222µg/m3 and 77µg/m3 . Minimum values for laboratory, outdoor and corridors were 10µg/m3 , 20µg/m3 and 8µg/m3 .
Factors affecting these values were laboratory activities and proximity to main roads. These values were significantly
higher than the standard values defined by EPA. Therefore children in schools were at risk of developing health
complications
Channel, Phase Noise, and Frequency Offset in OFDM Systems: Joint Estimation, Data Detection, and Hybrid Cramer-Rao Lower Bound
Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely
impact the performance of orthogonal frequency division multiplexing (OFDM)
systems, since they can result in inter carrier interference and rotation of
the signal constellation. In this paper, we propose an expectation conditional
maximization (ECM) based algorithm for joint estimation of channel, PHN, and
CFO in OFDM systems. We present the signal model for the estimation problem and
derive the hybrid Cramer-Rao lower bound (HCRB) for the joint estimation
problem. Next, we propose an iterative receiver based on an extended Kalman
filter for joint data detection and PHN tracking. Numerical results show that,
compared to existing algorithms, the performance of the proposed ECM-based
estimator is closer to the derived HCRB and outperforms the existing estimation
algorithms at moderate-to-high signal-to-noise ratio (SNR). In addition, the
combined estimation algorithm and iterative receiver are more computationally
efficient than existing algorithms and result in improved average uncoded and
coded bit error rate (BER) performance
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