| 1. |
- Feigin, Valery L., et al.
(författare)
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Global, regional, and national burden of neurological disorders, 1990–2016 : a systematic analysis for the Global Burden of Disease Study 2016
- 2019
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Ingår i: Lancet Neurology. - : Elsevier. - 1474-4422 .- 1474-4465. ; 18:5, s. 459-480
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Tidskriftsartikel (refereegranskat)abstract
- Background: Neurological disorders are increasingly recognised as major causes of death and disability worldwide. The aim of this analysis from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 is to provide the most comprehensive and up-to-date estimates of the global, regional, and national burden from neurological disorders.Methods: We estimated prevalence, incidence, deaths, and disability-adjusted life-years (DALYs; the sum of years of life lost [YLLs] and years lived with disability [YLDs]) by age and sex for 15 neurological disorder categories (tetanus, meningitis, encephalitis, stroke, brain and other CNS cancers, traumatic brain injury, spinal cord injury, Alzheimer's disease and other dementias, Parkinson's disease, multiple sclerosis, motor neuron diseases, idiopathic epilepsy, migraine, tension-type headache, and a residual category for other less common neurological disorders) in 195 countries from 1990 to 2016. DisMod-MR 2.1, a Bayesian meta-regression tool, was the main method of estimation of prevalence and incidence, and the Cause of Death Ensemble model (CODEm) was used for mortality estimation. We quantified the contribution of 84 risks and combinations of risk to the disease estimates for the 15 neurological disorder categories using the GBD comparative risk assessment approach.Findings: Globally, in 2016, neurological disorders were the leading cause of DALYs (276 million [95% UI 247–308]) and second leading cause of deaths (9·0 million [8·8–9·4]). The absolute number of deaths and DALYs from all neurological disorders combined increased (deaths by 39% [34–44] and DALYs by 15% [9–21]) whereas their age-standardised rates decreased (deaths by 28% [26–30] and DALYs by 27% [24–31]) between 1990 and 2016. The only neurological disorders that had a decrease in rates and absolute numbers of deaths and DALYs were tetanus, meningitis, and encephalitis. The four largest contributors of neurological DALYs were stroke (42·2% [38·6–46·1]), migraine (16·3% [11·7–20·8]), Alzheimer's and other dementias (10·4% [9·0–12·1]), and meningitis (7·9% [6·6–10·4]). For the combined neurological disorders, age-standardised DALY rates were significantly higher in males than in females (male-to-female ratio 1·12 [1·05–1·20]), but migraine, multiple sclerosis, and tension-type headache were more common and caused more burden in females, with male-to-female ratios of less than 0·7. The 84 risks quantified in GBD explain less than 10% of neurological disorder DALY burdens, except stroke, for which 88·8% (86·5–90·9) of DALYs are attributable to risk factors, and to a lesser extent Alzheimer's disease and other dementias (22·3% [11·8–35·1] of DALYs are risk attributable) and idiopathic epilepsy (14·1% [10·8–17·5] of DALYs are risk attributable).Interpretation: Globally, the burden of neurological disorders, as measured by the absolute number of DALYs, continues to increase. As populations are growing and ageing, and the prevalence of major disabling neurological disorders steeply increases with age, governments will face increasing demand for treatment, rehabilitation, and support services for neurological disorders. The scarcity of established modifiable risks for most of the neurological burden demonstrates that new knowledge is required to develop effective prevention and treatment strategies.Funding: Bill & Melinda Gates Foundation.
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| 2. |
- Csikos, A, et al.
(författare)
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Network traffic flow optimization under performance constraints
- 2017
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Ingår i: Transportation Research, Part C: Emerging Technologies. - : Elsevier BV. - 0968-090X. ; 83, s. 120-133
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a model-based perimeter control policy for large-scale urban vehicular networks is proposed. Assuming a homogeneously loaded vehicle network and the existence of a well-posed Network Fundamental Diagram (NFD), we describe a protected network throughout its aggregated dynamics including nonlinear exit flow characteristics. Within this framework of constrained optimal boundary flow gating, two main performance metrics are considered: (a) first, connected to the NFD, the concept of average network travel time and delay as a performance metric is defined; (b) second, at boundaries, we take into account additional external network queue dynamics governed by uncontrolled inflow demands. External queue capacities in terms of finite-link lengths are used as the second performance metric. Hence, the corresponding performance requirement is an upper bound of external queues. While external queues represent vehicles waiting to enter the protected network, internal queue describes the protected network’s aggregated behavior.By controlling the number of vehicles joining the internal queue from the external ones, herewith a network traffic flow maximization solution subject to the internal and external dynamics and their performance constraints is developed. The originally non-convex optimization problem is transformed to a numerically efficiently convex one by relaxing the performance constraints into time-dependent state boundaries. The control solution can be interpreted as a mechanism which transforms the unknown arrival process governing the number of vehicles entering the network to a regulated process, such that prescribed performance requirements on travel time in the network and upper bound on the external queue are satisfied. Comparative numerical simulation studies on a microscopic traffic simulator are carried out to show the benefits of the proposed method.
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| 3. |
- Csikos, A, et al.
(författare)
-
Traffic flow optimization with QoS constrained network admission control
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 50:1, s. 5275-5280
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Konferensbidrag (refereegranskat)abstract
- The paper proposes a control design method in order to gate input flow to a protected urban vehicular network such that travel time Quality of Service (QoS) constraints are preserved within the network. In view of the network to be protected (also called the region), two types of queues are distinguished: external and internal. While external queues represent vehicles waiting to enter the protected network, an internal queue can be used to describe the network's aggregated behaviour. By controlling the number of vehicles entering the internal queue, the travel time within the network subject to the vehicular conservation law and the Network Fundamental Diagram (NFD) can be subsequently controlled. The admission controller can thus be interpreted as a mechanism which transforms the unknown arrival process governing the number of vehicles entering the network to a regulated process, such that prescribed QoS requirements on travel time in the network and upper bound on the external queue are satisfied. The admission control problem is formulated as a constrained convex optimization problem and a Model Predictive Control (MPC) problem. A case study demonstrates the benefits of the admission control mechanisms proposed.
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| 4. |
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| 5. |
- Farhadi, Hamed, 1983, et al.
(författare)
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An adaptive localization technique for wireless capsule endoscopy
- 2016
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Ingår i: International Symposium on Medical Information and Communication Technology, ISMICT. - : IEEE Computer Society. - 2326-8301 .- 2326-828X. - 9781509028498
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Konferensbidrag (refereegranskat)abstract
- Wireless capsule endoscopy (WCE) is an emerging technique to enhance Gastroenterologists information about the patient's gastrointestinal (G.I.) tract. Localization of capsule inside human body in this case is an active area of research. This can be thought of as a sub-domain of micro and bio-robotics fields. If capsule and micro-robot localization problem in human body is solved, then it may potentially lead to less invasive treatments for G.I. diseases and other micro-robot assisted medical procedures. Several approaches have been investigated by the researchers to estimate capsule location. The proposed solutions are mainly static and thus prone to the changes in the propagation medium. We propose an adaptive algorithm based on expectation maximization technique for capsule localization. The proposed algorithm adaptively updates the estimated location based on the received radio frequency (RF) signal measurements.
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| 6. |
- Farhadi, Hamed, 1983-
(författare)
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Coordinated Transmission for Wireless Interference Networks
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless interference networks refer to communication systems in which multiple source–destination pairs share the same transmission medium, and each source’s transmission interferes with the reception at non-intended destinations. Optimizing the transmission of each source–destination pair is interrelated with that of the other pairs, and characterizing the performance limits of these networks is a challenging task. Solving the problem of managing the interference and data communications for these networks would potentially make it possible to apply solutions to several existing and emerging communication systems. Wireless devices can carefully coordinate the use of scarce radio resources in order to deal effectively with interference and establish successful communications. In order to enable coordinated transmission, terminals must usually have a certain level of knowledge about the propagation environment; that is, channel state information (CSI). In practice, however, no CSI is a priori available at terminals (transmitters and receivers), and proper channel training mechanisms (such as pilot-based channel training and channel state feedback) should be employed to acquire CSI. This requires each terminal to share available radio resources between channel training and data transmissions. Allocating more resources for channel training leads to an accurate CSI estimation, and consequently, a precise coordination. However, it leaves fewer resources for data transmissions. This creates the need to investigate optimum resource allocation. This thesis investigates an information-theoretic approach towards the performance analysis of interference networks, and employs signal processing techniques to design transmission schemes for achieving these limits in the following scenarios. First, the smallest interference network with two single-input single-output (SISO) source–destination pairs is considered. A fixed-rate transmission is desired between each source–destination pair. Transmission schemes based on point-to-point codes are developed. The transmissions may not always attain successful communication, which means that outage events may be declared. The outage probability is quantified and the ε-outage achievable rate region is characterized. Next, a multi-user SISO interference network is studied. A pilot-assisted ergodic interference alignment (PAEIA) scheme is proposed to conduct channel training, channel state feedback, and data communications. The performance limits are evaluated, and optimum radio resource allocation problems are investigated. The analysis is extended to multi-cell wireless interference networks. A low-complexity pilot-assisted opportunistic user scheduling (PAOUS) scheme is proposed. The proposed scheme includes channel training, one-bit feedback transmission, user scheduling and data transmissions. The achievable rate region is computed, and the optimum number of cells that should be active simultaneously is determined. A multi-user MIMO interference network is also studied. Here, each source sends multiple data streams; specifically, the same number as the degrees of freedom of the network. Distributed transceiver design and power control algorithms are proposed that only require local CSI at terminals.
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| 7. |
- Farhadi, Hamed, et al.
(författare)
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Distributed interference alignment and power control for wireless MIMO interference networks
- 2013
-
Ingår i: 2013 IEEE Wireless Communications and Networking Conference (WCNC). - : IEEE Communications Society. - 1525-3511. - 9781467359399 - 9781467359382 ; , s. 3077-3082
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Konferensbidrag (refereegranskat)abstract
- This paper considers joint transceiver design and power control for K-user multiple-input multiple-output (MIMO) interference networks. Each source intends to communicate with its corresponding destination at a fixed data rate. Only local channel side information (i.e. knowledge related to the channels directly connected to a terminal) is available at each terminal. We propose iterative algorithms to perform power control to guarantee successful communication while designing transmitter beamforming matrices and receiver filtering matrices according to the interference alignment concept. The proposed algorithms can exhibit a substantial performance improvement compared to the conventional orthogonal transmission schemes.
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| 8. |
- Farhadi, Hamed, et al.
(författare)
-
Distributed Interference Alignment and Power Control for Wireless MIMO Interference Networks with Noisy Channel State Information
- 2013
-
Ingår i: 2013 First International Black Sea Conference on Communications and Networking (BlackSeaCom). - : IEEE conference proceedings. - 9781479908578 ; , s. 23-27
-
Konferensbidrag (refereegranskat)abstract
- This paper considers a multi-input multi-output(MIMO) interference network in which each transmitter intendsto communicate with its dedicated receiver at a certain fixed rate. It is known that when perfect CSI is available at each terminal, the interference alignment technique can be applied to align theinterference signals at each receivers in a subspace independent of the desired signal subspace. The impact of interference canhence be eliminated. In practice, however, terminals in general can acquire only noisy CSI. Interference alignment cannot be perfectly performed to avoid interference leakage in the signal subspace. Thus, the quality of each communication link dependson the transmission power of the unintended transmitters. Tosolve this problem, we propose an iterative algorithm to performstochastic power control and transceiver design based on onlynoisy local CSI. The transceiver design is conducted based on the interference alignment concept, and the power control seeks solutions of efficiently assigning transmit powers to provide successful communications for all transmitter-receiver pairs.
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| 9. |
- Farhadi, Hamed, et al.
(författare)
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Distributed Transceiver Design and Power Control for Wireless MIMO Interference Networks
- 2015
-
Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276 .- 1558-2248. ; 14:3, s. 1199-1212
-
Tidskriftsartikel (refereegranskat)abstract
- This paper considers distributed transceiver design and power control for K-user multiple-input-multiple-output interference networks. Each source intends to send multiple independent data streams to its corresponding destination where the number of data streams coincides with the degrees of freedom of the network. Each data stream is encoded at a fixed data rate, whereas different streams can be encoded at possibly different rates. We assume that only local channel side information (i.e., knowledge related to channels directly connected to a terminal) can be acquired by each terminal. We propose iterative algorithms to perform both power control and transceiver design. Transmitter beamforming matrices and receiver filtering matrices are designed to maximize signal-to-interference-plus-noise ratio corresponding to each stream, and a power control scheme is performed to assign the minimum power to each encoded data stream such that successful communication can be guaranteed. The proposed algorithms exhibit a substantial performance improvement compared with the conventional orthogonal transmission schemes.
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| 10. |
- Farhadi, Hamed, 1983, et al.
(författare)
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Ergodic Interference Alignment with Limited Feedback: Power Control and Rate Adaptation
- 2015
-
Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers. - 1558-2248 .- 1536-1276. ; 14:12, s. 6679-6694
-
Tidskriftsartikel (refereegranskat)abstract
- Considering the time-varying K-user single-antenna interference channel (IC), it has been shown that, when terminals have perfect global channel state information (CSI) and they can tolerate asymptotically long delay, applying an ergodic interference alignment (EIA) scheme can achieve half of the interference-free achievable rate. However, in practice obtaining such CSI is challenging, and only a limited delay is acceptable. This paper addresses data transmission over the IC by taking these concerns into account. Specifically, we consider the case that each transmitter attains only quantized CSI via limited feedback signals. This causes imperfect interference alignment and a degraded performance. We propose adaptive schemes to compensate the impact of the CSI uncertainties. We first study a power control problem which concerns how to communicate at fixed rates using minimum transmit powers. A power control algorithm is used to reach the solution. Next, we address a throughput maximization problem when the transmit powers are fixed. Through the analysis of system outage probability, we propose a rate adaptation scheme to maximize throughput. Finally, we quantify the throughput loss in delay-limited systems. Our results show that, even with limited feedback, performing the EIA scheme with proper power control or rate adaptation strategies can still outperform conventional orthogonal transmission approaches.
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| 11. |
- Farhadi, Hamed, 1983-, et al.
(författare)
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Ergodic interference alignment with noisy channel state information
- 2013
-
Ingår i: 2013 IEEE International Symposium on Information Theory Proceedings (ISIT). - : IEEE conference proceedings. - 9781479904464 ; , s. 584-588
-
Konferensbidrag (refereegranskat)abstract
- We investigate the multi-user time-varying Gaussian interference channel (IC) in which each source desires to communicate to an intended destination. For the ergodic time-varying IC with global perfect CSI at all terminals, it is known that with an interference alignment technique each source-destinationpair can communicate at half of the interference-free achievable rate. In practice, the channel gains are estimated by transmitting known pilot symbols from the sources, and the channel estimation procedure is hence prone to errors. In this paper, we model the channel estimation error at the destinations by an independent additive Gaussian noise and study the behavior of the ergodic interference alignment scheme with the global noisy CSI at all terminals. Toward this end, we present a closed-form innerbound on the achievable rate region by which we conclude that the achievable degrees of freedom with global perfect CSI is preserved, if the variance of channel estimation error is proportional to the inverse of the transmitted power.
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| 12. |
- Farhadi, Hamed, 1983, et al.
(författare)
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Fixed-Rate Transmission Over Fading Interference Channels Using Point-to-Point Gaussian Codes
- 2015
-
Ingår i: IEEE Transactions on Communications. - : IEEE Press. - 0090-6778 .- 1558-0857. ; 63:10, s. 3633 - 3644
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates transmission schemes for fixed-rate communications over a Rayleigh block-fading interference channel. There are two source-destination pairs where each source, in the presence of a short-term power constraint, intends to communicate with its dedicated destination at a fixed data rate. It encodes its messages using a point-to-point Gaussian codebook. The two users' transmissions can be conducted orthogonally or non-orthogonally. In the latter case, each destination performs either direct decoding by treating the interference as noise, or successive interference cancellation (SIC) to recover its desired message. For each scheme, we seek solutions of a power control problem to efficiently assign power to the sources such that the codewords can be successfully decoded at destinations. However, because of the random nature of fading, the power control problem for some channel realizations may not have any feasible solution and the transmission will be in outage. Thus, for each transmission scheme, we first compute a lower bound and an upper bound on the outage probability. Next, we use these results to find an outer bound and an inner bound on the \epsilon-outage achievable rate region, i.e., the rate region in which the outage probability is below a certain value \epsilon.
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| 13. |
- Farhadi, Hamed, 1983-
(författare)
-
Interference alignment and power control for wireless interference networks
- 2012
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the design of efficient transmission schemes forwireless interference networks, when certain channel state information(CSI) is available at the terminals.In wireless interference networks multiple source-destination pairsshare the same transmission medium for the communications. The signalreception at each destination is affected by the interference from unintendedsources. This may lead to a competitive situation that each sourcetries to compensate the negative effect of interference at its desired destinationby increasing its transmission power, while it in fact increasesthe interference to the other destinations. Ignoring this dependency maycause a significant waste of available radio resource. Since the transmissiondesign for each user is interrelated to the other users’ strategies, anefficient radio resource allocation should be jointly performed consideringall the source-destination pairs. This may require a certain amount ofCSI to be exchanged, e.g. through feedback channels, among differentterminals. In this thesis, we investigate such joint transmission designand resource allocation in wireless interference networks.We first consider the smallest interference network with two sourcedestinationpairs. Each source intends to communicate with its dedicateddestination with a fixed transmission rate. All terminals have the perfectglobal CSI. The power control seeks feasible solutions that properly assigntransmission power to each source in order to guarantee the successfulcommunications of both source-destination pairs. To avoid interference,the transmissions of the two sources can be orthogonalized. They canalso be activated non-orthogonally. In this case, each destination maydirectly decode its desired signals by treating the interference signals asnoise. It may also perform decoding of its desired signals after decodingand subtracting the interference signals sent from the unintendedsources. The non-orthogonal transmission can more efficiently utilize the available channel such that the power control problem has solutions withsmaller transmission power in comparison with the orthogonal transmission.However, due to the randomness of fading effects, feasible powercontrol solutions may not always exist. We quantify the probability thatthe power control problem has feasible solutions, under a Rayleigh fadingenvironment. A hybrid transmission strategy that combines the orthogonaland non-orthogonal transmissions is then employed to use the smallesttransmission power to guarantee the communications in the consideredtwo-user interference network.The network model is further extended to the general K-user interferencenetwork, which is far more complicated than the two-user case. Thecommunication is conducted in a time-varying fading environment. Thefeedback channel’s capacity is limited so that each terminal can obtainonly quantized global CSI. Conventional interference management techniquestend to orthogonalize the transmissions of the sources. However,we permit them to transmit non-orthogonally and apply an interferencealignment scheme to tackle inter-user interference. Ideally, the interferencealignment concept coordinates the transmissions of the sources insuch a way that at each destination the interference signals from differentunintended sources are aligned together in the same sub-space which isdistinguishable from the sub-space for its desired signals. Hence, eachdestination can cancel the interference signals before performing decoding.Nevertheless, due to the imperfect channel knowledge, the interferencecannot be completely eliminated and thus causes difficulties to theinformation recovery process. We study efficient resource allocation intwo different classes of systems. In the first class, each source desires tosend information to its destination with a fixed data rate. The powercontrol problem tends to find the smallest transmission powers to guaranteesuccessful communications between all the source-destination pairs.In another class of systems where the transmission power of each sourceis fixed, a rate adaptation problem seeks the maximum sum throughputthat the network can support. In both cases, the combination of interferencealignment and efficient resource allocation provides substantialperformance enhancement over the conventional orthogonal transmissionscheme.When the fading environment is time-invariant, interference alignmentcan still be realized if each terminal is equipped with multiple antennas.With perfect global CSI at all terminals, the interference signalscan be aligned in the spatial dimension. If each terminal has only localCSI, which refers to the knowledge of channels directly related to the terminal itself, an iterative algorithm can be applied to calculate thenecessary transmitter-side beamformers and receiver-side filters to properlyalign and cancel interference, respectively. Again, due to the lack ofperfect global CSI, it is difficult to completely eliminate the interferenceat each destination. We study the power control problem in this caseto calculate the minimum required power that guarantees each source tosuccessfully communicate with its destination with a fixed transmissionrate. In particular, since only local CSI is available at each terminal, wepropose an iterative algorithm that solves the joint power control andinterference alignment design in a distributed fashion. Our results showthat a substantial performance gain in terms of required transmissionpower over the orthogonalizing the transmissions of different sources canbe obtained.
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| 14. |
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| 15. |
- Farhadi, Hamed, 1983
(författare)
-
On the throughput of wireless interference networks with limited feedback
- 2011
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Ingår i: IEEE International Symposium on Information Theory Proceedings (ISIT'11). - 2157-8095. - 9781457705960 ; , s. 762 - 766
-
Konferensbidrag (refereegranskat)abstract
- Considering a single-antenna M-user interference channel with symmetrically distributed channel gains, when the channel state information (CSI) is globally available, applying the ergodic interference alignment scheme, each transmitter-receiver pair achieves a rate proportional to ½ of a single user's interference-free achievable rate. This is substantially higher than the achievable rate of the conventional orthogonal transmission schemes such as TDMA. Since the rigid requirement on the CSI may be difficult to realize in practice, in this paper we investigate the performance of applying the ergodic interference alignment scheme when the estimation of each channel gain is made globally known through exploiting only a limited feedback signal from the associated receiver of that channel. Under a block fading environment, we provide a lower bound on the achievable average throughput of the network. Our results imply that the better performance of interference alignment over TDMA may still exist even without the assumption of perfect CSI. Also, the trade off between allocating feedback rate of each receiver to the desired channel or the interference channels at deferent SNR region investigated.
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| 16. |
- Farhadi, Hamed, 1983-, et al.
(författare)
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On the Throughput of Wireless Interference Networks with Limited Feedback
- 2011
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Ingår i: 2011 IEEE International Symposium on Information Theory Proceedings (ISIT). - : IEEE. - 9781457705960 - 9781457705946 ; , s. 762-766
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Konferensbidrag (refereegranskat)abstract
- Considering a single-antenna M-user interferencechannel with symmetrically distributed channel gains, when thechannel state information (CSI) is globally available, applyingthe ergodic interference alignment scheme, each transmitterreceiverpair achieves a rate proportional to 1⁄2 of a single user’sinterference-free achievable rate. This is substantially higher thanthe achievable rate of the conventional orthogonal transmissionschemes such as TDMA. Since the rigid requirement on theCSI may be difficult to realize in practice, in this paper weinvestigate the performance of applying the ergodic interferencealignment scheme when the estimation of each channel gain ismade globally known through exploiting only a limited feedbacksignal from the associated receiver of that channel. Under a blockfading environment, we provide a lower bound on the achievableaverage throughput of the network. Our results imply that thebetter performance of interference alignment over TDMA maystill exist even without the assumption of perfect CSI. Also, thetrade off between allocating feedback rate of each receiver tothe desired channel or the interference channels at deferent SNRregion investigated.
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| 17. |
- Farhadi, Hamed, 1983-, et al.
(författare)
-
Pilot-assisted ergodic interference alignment for wireless networks
- 2014
-
Konferensbidrag (refereegranskat)abstract
- This paper considers the ergodic block fading multi-user Gaussian interference channel (IC) in which each source desires to communicate to an intended destination. We assume that there is no CSI a priori available at terminals. We develop achievable rate results and compute the associated degrees of freedom by using a pilot-assisted interference alignment scheme. In this scheme, each source first sends known pilot symbols via which the destinations estimate channel gains, and the destinations then broadcast the estimated channel gains via orthogonal feedback channels. The estimated channel gains are used to perform interference alignment for data transmission. The pilot transmission power can be different from the data transmission power. By allocating more power to pilot transmission, channel gains can be estimated more accurately which implies less power left for data transmission. We find the optimum power allocation to pilot symbols and data symbols. Our study recommends, in large networks, to allocate more power to channel training instead of data transmission. In addition, our results reveal that for a K-user ergodic IC with a coherence time T, the total degrees of freedom 1/2Kopt(1-Kopt/T) is achievable, where Kopt=min{K,T/2} is the optimum number of users selected to be active in the network. This recommends to perform a user selection in large networks (K>T/2), and apply channel training and interference alignment within the set of selected users.
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| 18. |
- Farhadi, Hamed, 1983-, et al.
(författare)
-
Pilot-assisted opportunistic user scheduling for wireless multi-cell networks
- 2015
-
Ingår i: IEEE International Conference on Communications. - : IEEE. - 9781467363051
-
Konferensbidrag (refereegranskat)abstract
- We consider downlink transmission in multi-cell wireless networks where in each cell one base station is serving multiple mobile terminals. There is no a priori channel state information (CSI) available at base stations and mobile terminals. We propose a low-complexity pilot-assisted opportunistic user scheduling (PAOUS) scheme. The proposed scheme operates in four subsequent phases: channel training; feedback transmission; user scheduling; and data transmission. We deploy an orthogonal pilot-assisted channel training scheme for acquiring CST at mobile terminals. Consequently, each mobile terminal obtains a noisy estimation of the corresponding local CST (i.e. channel gains from base stations to the mobile terminal). Then, it makes a local decision based on the estimated channel gains of the interfering links (i.e. the links between base stations in neighboring cells and the mobile terminal) and sends a one-bit feedback signal to the base station of the corresponding cell. Each base station schedules one mobile terminal for communication. We compute the achievable rate region and the achievable degrees of freedom (DoF) of the proposed transmission scheme. Our results show that in a multi-cell network with K base stations and coherence time T, the total DoF K-opt (1 - K-opt/T) is achievable given that the number of mobile terminals in each cell scales proportional to signal-to-noise-ratio. Since limited radio resources are available, only a subset of base stations should be activated, where the optimum number of active base stations is K-opt = min {K, T/2}. This recommends that in large networks (K > T/2), select only a subset of the base stations to be active and perform the PAOUS scheme within the cells associated to these base stations. Our results reveal that, even with single antenna at base stations and no a priori CSI at terminals, a non-trivial DoF gain can be achieved. We also investigate the power allocation between channel training and data transmission phases. Our study shows that in large networks (many base stations) more power should be allocated to channel training while in dense networks (many mobile terminals in each cell) more power should be allocated for data transmission.
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| 19. |
- Farhadi, Hamed, 1983-, et al.
(författare)
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Power Control in Wireless Interference Networks with Limited Feedback
- 2012
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Ingår i: International Symposium on Wireless Communication Systems (ISWCS), 2012. - : IEEE conference proceedings. - 2154-0217. - 9781467307604 - 9781467307611 ; , s. 671-675
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Konferensbidrag (refereegranskat)abstract
- This paper addresses a power control problem in a wireless time-varying K-user interference network. Each transmitter intends to communicate to its desired receiver at afixed rate. Quantized channel gains are globally available through limited feedback signals. To eliminate multi-user interference, interference alignment scheme is performed based on the imperfect channel knowledge. The communication quality is affected by the channel quantization errors and interference leakage. We proposea power control algorithm, aiming to guarantee successful transmissions of each user while minimizing the transmission powerof the network. Our results show that even with limited number of feedback bits, by performing power control the considered interference alignment scheme can outperform the conventional time-division-multiple-access scheme.
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| 20. |
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| 21. |
- Goli, Zahra, et al.
(författare)
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Secure Simultaneous Information and Power Transfer for Downlink Multi-User Massive MIMO
- 2020
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Ingår i: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536 .- 2169-3536. ; 8, s. 150514-150526
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Tidskriftsartikel (refereegranskat)abstract
- In this article, downlink secure transmission in simultaneous information and power transfer (SWIPT) system enabled with massive multiple-input multiple-output (MIMO) is studied. A base station (BS) with a large number of antennas transmits energy and information signals to its intended users, but these signals are also received by an active eavesdropper. The users and eavesdropper employ a power splitting technique to simultaneously decode information and harvest energy. Massive MIMO helps the BS to focus energy to the users and prevent information leakage to the eavesdropper. The harvested energy by each user is employed for decoding information and transmitting uplink pilot signals for channel estimation. It is assumed that the active eavesdropper also harvests energy in the downlink and then contributes during the uplink training phase. Achievable secrecy rate is considered as the performance criterion and a closed-form lower bound for it is derived. To provide secure transmission, the achievable secrecy rate is then maximized through an optimization problem with constraints on the minimum harvested energy by the user and the maximum harvested energy by the eavesdropper. Numerical results show the effectiveness of using massive MIMO in providing physical layer security in SWIPT systems and also show that our closed-form expressions for the secrecy rate are accurate.
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| 22. |
- Hosseini, M., et al.
(författare)
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A model for electro-chemical neural communication
- 2020
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Ingår i: 15th International Conference on Body Area Networks, BodyNets 2020. - Cham : Springer Science and Business Media Deutschland GmbH. ; , s. 137-150
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Konferensbidrag (refereegranskat)abstract
- The neuro-spike communication is conducted using electro-chemical nervous signal transmissions between neurons and synapses. The nervous signal is composed of a sequence of electrically charged ions exchange in the neurons. It passes to other from one neuron to another one through the process of release and a combination of chemical substances in synapses. The neuro-spike communication is subject to disruptions due to different biological factors that impact the permanence of neural communications. In this paper, we investigate the performance of a neuro-spike communication between two neighboring neurons. We first present a mathematical model to capture the inherent biological characteristics of the nervous system. Next, the error probability of signal detection as a function of biological parameters has been characterized. Finally, we study the impacts of some specific medicines on the parameters of neuro-spike communication in the diseases of Multiple Sclerosis and Alzheimer’s.
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| 23. |
- Hosseini, Maryam, et al.
(författare)
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Game theory-based radio resource allocation in NOMA vehicular communication networks supported by UAV
- 2022
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Ingår i: Physical Communication. - : Elsevier BV. - 1874-4907 .- 1876-3219. ; 52, s. 101681-
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Tidskriftsartikel (refereegranskat)abstract
- Vehicular communication networks are emerging as a promising technology to provide high-quality internet service such as entertainment for road users via infrastructure-to-vehicle (I2V) communication, and to guarantee road users' safety via vehicle-to-vehicle (V2V) communication. Some technical issues that impact the performance of these networks are the lack of or poor communication paths between vehicles, and the limitation of radio resources. Unmanned aerial vehicles (UAVs) as promising solutions for supporting vehicular networks could provide communication coverage in hazardous environments and areas with no capacities for installation or maintenance of ground base stations (BSs). Also, non-orthogonal multiple access (NOMA) methods can improve spectral and energy efficiency and thereby allow more users to be connected to the desired network. In this paper, exploring the NOMA, we develop a scheme for optimum resource allocation in presence of a UAV that supports vehicular communications. Resource allocation for this scenario is formulated as a mixed-integer non-linear programming (MINLP) problem. Due to the high complexity of such problems, we propose two low-complexity near-optimal methods. First, we apply difference-of-concave-functions (DC) approximations to solve the problem in an iterative process. Next, we use Stackelberg game-based method for efficient solving, and then, closed-form expressions of optimal power allocations using KKT-conditions are derived. Simulations illustrate the effectiveness of the proposed scheme along with the Stackelberg game-based method.
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| 24. |
- Jacobsson, Sven, 1990, et al.
(författare)
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Beamformed transmission using a precoder
- 2023
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- There is provided mechanisms for beamformed transmission using a precoder. A method is performed by a radio transceiver device. The radio transceiver device comprises hard ware. The hardware impacts transmission of signals from the radio transceiver device. The method comprises acquiring channel conditions of a radio propagation channel between the radio transceiver device and at least one other radio transceiver device. The method comprises determining a precoder, in form of a linear precoding matrix, for beam formed transmission towards the at least one other radio transceiver device. The precoder is determined according to the channel conditions and a model of how the hardware impacts the transmission of signals from the radio transceiver device. The method comprises transmitting, using the precoder, a signal towards the at least one other radio transceiver device.
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| 25. |
- Lozano, Rafael, et al.
(författare)
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Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
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Tidskriftsartikel (refereegranskat)abstract
- Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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| 26. |
- Moghadam, N. N., 1986-, et al.
(författare)
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Optimal power allocation for pilot-assisted interference alignment in MIMO interference networks: Test-bed results
- 2015
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Ingår i: IEEE International Conference on Digital Signal Processing, DSP 2015, Singapore, 21-24 July. - : IEEE. - 9781479980581 ; 2015-September, s. 585-589
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Konferensbidrag (refereegranskat)abstract
- This paper addresses channel training and data communication over multi-input multi-input (MIMO) interference networks. We consider a pilot-assisted interference alignment scheme in which part of radio resources are allocated to channel training and the remaining resources are used for data transmission. A more accurate channel estimation can be obtained by increasing pilot transmission power. Since each transmitter has limited energy budget, this implies that less power is available for data transmission. Clearly, there is a trade off between the allocated power for channel training and the one for data communication. In order to investigate this trade off, first we compute an achievable sum-rate, and next we find the optimum power allocation to pilot transmission and data transmission. Finally, we verify these theoretical results with experimental measurements on USRP-based test-bed.
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| 27. |
- Moghadam, Nima N., et al.
(författare)
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Test-Bed Implementation of Iterative Interference Alignment and Power Control for Wireless MIMO Interference Networks
- 2014
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Ingår i: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC). - : IEEE. - 9781479949038 ; , s. 239-243
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Konferensbidrag (refereegranskat)abstract
- This paper presents for the first time the testbed implementation of an iterative interference alignment and power control algorithm for downlink transmission in a multiple-input multiple-output (MIMO) cellular network. The network is composed of three cells where within each cell one base station (BS) communicates with one mobile station (MS). Each terminal is equipped with two antennas. All the BSs transmit at the same time and the same frequency band. Transmitter beamforming vectors and receiver filtering vectors are computed according to the interference alignment concept, and power control is performed to guarantee successful communication of each BS-MS pair at a desired fixed rate. The indoor measurements performed on an universal software radio peripheral (USRP) based test-bed, show that the power can be reduced by at least 4 dB, 90% of the time, while at the same time reducing the bit-error-rate (BER).
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| 28. |
- Najari Moghadam, Nima, 1986-, et al.
(författare)
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An energy efficient communication technique for medical implants/micro robots
- 2016
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Ingår i: 10th International Symposium on Medical Information and Communication Technology (ISMICT). - : IEEE Computer Society. ; 2016-June
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Konferensbidrag (refereegranskat)abstract
- Biomedical implanted sensors and medical micro robots are emerging devices which facilitate health monitoring, medical therapies, and minimally invasive surgeries. The success of these devices highly relies on establishing reliable communication links between inside and outside the body in the presence of severe constraints on energy consumptions. We develop an energy efficient pilot-assisted data transmission technique for communication between a single-antenna medical sensor/micro-robot inside the body to multi-antenna receiver on the body surface though non-homogeneous propagation environment.
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| 29. |
- Najari Moghadam, Nima, 1986-, et al.
(författare)
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Interference Alignment — Practical Challenges and Test-bed Implementation
- 2014
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Ingår i: Contemporary Issues in Wireless Communications. - : INTECH. - 9789535117322 ; , s. 51-77
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Bokkapitel (refereegranskat)abstract
- Data traffic over wireless communication networks has experienced a tremendous growth in the last decade, and it is predicted to exponentially increase in the next decades. Enabling future wireless networks to fulfill this expectation is a challenging task both due to the scarcity of radio resources (e.g. spectrum and energy), and also the inherent characteristics of the wireless transmission medium. Wireless transmission is in general subject to two phenomena: fading and interference. The elegant interference alignment concept reveals that with proper transmission signalling design, different interference signals can in fact be aligned together, such that more radio resources can be assigned to the desired transmission. Although interference alignment can achieve a larger data rate compared to orthogonal transmission strategies, several challenges should be addressed to enable the deployment of this technique in future wireless networks For instance, to perform interference alignment, normally, global channel state information (CSI) is required to be perfectly known at all terminals. Clearly, acquiring such channel knowledge is a challenging problem in practice and proper channel training and channel state feedback techniques need to be deployed. In addition, since the channels are time-varying proper adaptive transmission is needed. This chapter review recent advances in practical aspects of interference alignment. It also presents recent test-bed implementations of signal processing algorithms for the realization of interference alignment.
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| 30. |
- Schrammar, Nicolas, et al.
(författare)
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Average Throughput in AWGN Cognitive Fading Interference Channel with Multiple Secondary Pairs
- 2012
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Ingår i: Proceedings of the 2012 7th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCOM 2012. - : IEEE Computer Society. - 2166-5370. - 9781936968558 - 9781467329767 ; , s. 158-162
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Konferensbidrag (refereegranskat)abstract
- We consider the additive white Gaussian noise (AWGN) cognitive fading interference channel consisting of one primary and multiple secondary transmitter-receiver pairs. The secondary transmitters have non-causal knowledge of the primary message. We find a tuple of achievable rates by utilizing the discrete superposition model (DSM), which is a simplified, deterministic channel model. The coding scheme devised for the DSM can be translated into a coding scheme for the AWGN model, where the rate achieved in the AWGN model is at most a constant gap below the rate achieved in the DSM. We then calculate the average throughput of the secondary pairs under the assumption of Rayleigh fading channels. The main result is that our scheme performs well in the weak interference regime. The sum-throughput increases with the number of secondary pairs.
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| 31. |
- Tarighati, Alla, 1986-, et al.
(författare)
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Performance Analysis of Noisy Message-Passing Decoding of Low-Density Parity-Check Codes
- 2010
-
Ingår i: 6th International Symposium on Turbo Codes & Iterative Informayion Processing.
-
Konferensbidrag (refereegranskat)abstract
- A noisy message-passing decoding scheme isconsidered for low-density parity-check (LDPC) codes overadditive white Gaussian noise (AWGN) channels. The internaldecoder noise is motivated by the quantization noise in digitalimplementations or the intrinsic noise of analog LDPC decoders.We modelled the decoder noise as AWGN on the exchangedmessages in the iterative LDPC decoder. This is shown to renderthe message densities in the noisy LDPC decoder inconsistent.We then invoke Gaussian approximation and formulate a twodimensionaldensity evolution analysis for the noisy LDPCdecoder. This allows for not only tracking the mean, but also thevariance of the message densities, and hence, quantifying thethreshold of the LDPC code. According to the results, a decodernoise of unit variance, increases the threshold for a regular (3,6) code by 1.672dB.
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| 32. |
- Wang, Chao, et al.
(författare)
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Achieving the Degrees of Freedom of Wireless Multi-User Relay Networks
- 2012
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 60:9, s. 2612-2622
-
Tidskriftsartikel (refereegranskat)abstract
- We study the available degrees of freedom (DOF) of a class of wireless single-antenna multi-user relay networks. In these networks the communications between M unconnected source-destination pairs are provided by a large number of half-duplex relays. To conduct the communications we propose a cluster successive relaying protocol that divides the relays into two equal-size clusters. Unlike the conventional orthogonal relaying protocol that demands all the relays to simultaneously assist the sources, we require the two relay clusters to take turns forwarding the source messages to more efficiently use the channel. In a time-varying fading environment, through appropriate interference alignment the negative impact of inter-user interference can be effectively minimized. Thus the two clusters of half-duplex relays can mimic a cluster of full-duplex relays. When the number of relays is infinitely large, we show that the M-user half-duplex relay networks have M DOF, i.e. their sum capacity can be characterized as C-Sigma(SNR) = M log(SNR)+ o(log(SNR)). This result implies that allowing only distributed processing and half-duplex operation is able to provide the same DOF performance as permitting joint processing and full-duplex operation in wireless relay networks.
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| 33. |
- Wang, Chao, et al.
(författare)
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On the Degrees of Freedom of Parallel Relay Networks
- 2010
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Ingår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010. - 1930-529X. - 9781424456383 - 9781424456369
-
Konferensbidrag (refereegranskat)abstract
- We study the degrees of freedom (DOF) of a single-antenna M-user time-varying parallel relay network, where the communications between M pairs of unconnected sources and destinations are provided by a large number of half-duplex decode-and-forward (DF) relays. Unlike the conventional relaying strategy which demands all the relays to simultaneously assist the sources, we divide the relays into two clusters and permit them to take turns forwarding the source messages. With appropriate interference alignment design, it is proved that the M-user time-varying relay network has M DOF, provided that the number of relays is infinitely large.
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| 34. |
- Yetis, Cenk M., et al.
(författare)
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Interference Alignment Testbeds
- 2017
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Ingår i: IEEE Communications Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 0163-6804 .- 1558-1896. ; 55:10, s. 120-126
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Tidskriftsartikel (refereegranskat)abstract
- Interference alignment has triggered high impact research in wireless communications since it was proposed nearly 10 years ago. However, the vast majority of research is centered on the theory of interference alignment and is hardly feasible in view of the existing state-of-the-art wireless technologies. Although several research groups have assessed the feasibility of interference alignment via testbed measurements in realistic environments, the experimental evaluation of interference alignment is still in its infancy since most of the experiments were limited to simpler scenarios and configurations. This article summarizes the practical limitations of experimentally evaluating interference alignment, provides an overview of the available interference alignment testbed implementations, including the costs, and highlights the imperatives for succeeding interference alignment testbed implementations. Finally, the article explores future research directions on the applications of interference alignment in the next generation wireless systems.
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