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- Fröhle, Markus, 1984, et al.
(författare)
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Multi-Step Sensor Selection with Position Uncertainty Constraints
- 2014
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Ingår i: IEEE Globecom 2014 Workshop - Wireless Networking and Control for Unmanned Autonomous Vehicles. - 9781479974702 ; , s. 1439-1444
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Konferensbidrag (refereegranskat)abstract
- Research on localization systems has shifted from focusing mainly on accuracy towards a more cognitive design, accounting for communication constraints, energy limitations, and delay. This leads to a variety of sensor selection optimization problems that are solved using techniques from convex optimization. We provide a novel formulation of the sensor selectionproblem over an extended time horizon, aiming to minimize the sensing cost of an entire path while guaranteeing a certain position accuracy. We state algorithms for determining lower and upper bounds on the sensing cost and utilize these in a path selection problem for autonomous agents. Simulation results confirm the usefulness of our approach, where we observe a benefit of optimizing over longer time horizons in low to medium noise scenarios compared to a myopic sensor selection scheme.
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| 4. |
- Gustavsson, Ulf, 1975, et al.
(författare)
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On the Impact of Hardware Impairments on Massive MIMO
- 2014
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Ingår i: IEEE Globecom 2014 Workshop - Massive MIMO: From Theory to Practice, 2014-12-08, Austin, Texas, USA. - 9781479974702 ; , s. 294-300
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Konferensbidrag (refereegranskat)abstract
- Massive multi-user (MU) multiple-input multiple-output (MIMO) systems are one possible key technology for next generation wireless communication systems. Claims have been made that massive MU-MIMO will increase both the radiated energy efficiency as well as the sum-rate capacity by orders of magnitude, because of the high transmit directivity. However, due to the very large number of transceivers needed at each base-station (BS), a successful implementation of massive MU-MIMO will be contingent on of the availability of very cheap, compact and power-efficient radio and digital-processing hardware. This may in turn impair the quality of the modulated radio frequency (RF) signal due to an increased amount of power-amplifier distortion, phase-noise, and quantization noise. In this paper, we examine the effects of hardware impairments on a massive MU-MIMO single-cell system by means of theory and simulation. The simulations are performed using simplified, well-established statistical hardware impairment models as well as more sophisticated and realistic models based upon measurements and electromagnetic antenna array simulations.
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- Hossain, M. M. Aftab, et al.
(författare)
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Dimensioning of PA for massive MIMO system with load adaptive number of antennas
- 2014
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Ingår i: Globecom Workshops (GC Wkshps), 2014. - 9781479974702 ; , s. 1102-1108
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Konferensbidrag (refereegranskat)abstract
- This paper takes into consideration the non-ideal efficiency characteristics of realistic power amplifiers (PAs) along with the daily traffic profile in order to investigate the impact of power amplifier dimensioning on the energy efficiency of load adaptive massive MIMO system. A multicellular system has been considered where each base station (BS) is equipped with large number of antennas to serve many single antenna users. For a given number of users in a cell, the optimum number of active antennas maximizing energy efficiency (EE) has been derived where total BS downlink power is assumed to be fixed. Under the same assumption, the power amplifiers have been dimensioned in a way that maximize network energy efficiency not only for a for a single time snapshot but over twenty four hours of operation while considering dynamic efficiency characteristics of the PAs. In order to incorporate this daily load profile, each BS has been modeled as an M/G/c/c state dependent queue under the assumption that the network is dimensioned to serve a maximum number of users at a time corresponding to 100% cell traffic load. This load adaptive system along with the optimized PA dimensioning achieves 30% higher energy efficinecy compared to a base line system where the BSs always run with a fixed number of active antennas which are most energy efficient while serving 100% traffic load.
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- Khanzadi, M Reza, 1983, et al.
(författare)
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Oscillator Phase Noise and Small-Scale Channel Fading in Higher Frequency Bands
- 2014
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Ingår i: 2014 IEEE Globecom Workshops, GC Wkshps 2014; Austin; United States; 8 December 2014 through 12 December 2014. - 9781479974702 ; , s. 410-415
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the effect of oscillator phasenoise and channel variations due to fading on the performance of communication systems at frequency bands higher than 10GHz. Phase noise and channel models are reviewed and technology dependent bounds on the phase noise quality of radio oscillators are presented. Our study shows that, in general, both channel variations and phase noise can have severe effects on the system performance at high frequencies. Importantly, their relative severity depends on the application scenario and system parameters such as center frequency and bandwidth. Channel variations are seen to be more severe than phase noise when the relative velocity between the transmitter and receiver is high. On the other hand, performance degradation due to phase noise can be more severe when the center frequency is increased and thebandwidth is kept a constant, or when oscillators based on low power CMOS technology are used, as opposed to high powerGaN HEMT based oscillators.
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- Li, Jingya, 1986, et al.
(författare)
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Performance Analysis and Cooperation Mode Switch in HARQ-based Relaying
- 2014
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Ingår i: IEEE Global Communications Conference (GLOBECOM) workshop, Austin, TX, December 2014. - 9781479974702 ; , s. 930-935
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Konferensbidrag (refereegranskat)abstract
- We study the optimal, in terms of power-limited outage probability (OP), placement of the relay and investigatethe effect of relay placement on the optimal cooperation mode of the source and the relay nodes. Using hybrid automatic repeat request (HARQ) based relaying techniques, general expressions for the OP and the average transmit power are derived. The results are then particularized to the repetition time diversity (RTD) protocol. The analytical expressions are used to find thetransmit powers minimizing the power-limited OP. Our results demonstrate that adaptive power allocation reduces the OP significantly. For instance, consider a Rayleigh fading channel, an OP of 10^-3 and a maximum of 2 RTD-based retransmissions. Then, compared to equal power allocation, the required transmission signal-to-noise ratio (SNR) is reduced by 5 dB, if adaptivepower allocation is utilized. Another important observation is that, depending on the relay positions and the total power budget, the system should switch between the single-node transmission mode and the joint transmission mode, in order to minimize the outage probability.
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- Li, Yuan, et al.
(författare)
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Resilient topology design for free space optical cellular backhaul networking
- 2014
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Ingår i: 2014 IEEE Globecom Workshops (GC Wkshps). - : IEEE Press. - 9781479974702 ; , s. 487-492
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Konferensbidrag (refereegranskat)abstract
- With cellular networks' densification, backhaul solutions tend to go wireless to reduce costs. Free space optic (FSO) links are becoming an appealing, secure and high rate alternative to RF. To ensure a reliable cellular backhaul, redundancy provisions for disjoint paths between the nodes must be made in the network design phase. This paper presents cost-effective solutions, using FSO links and mirrors, that can be employed to upgrade a cellular backhaul with pre-deployed optical fibers. An integer programming model is introduced to approach optimal FSO backhaul design, guaranteeing K-disjoint paths between each node pair. We use realistic scenarios to demonstrate some optimal backhaul topologies by solving the model. We also illustrate the impact of K and the number of optical fibers on optimal solutions.
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| 9. |
- Lin, P. -H, et al.
(författare)
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Clean relaying in cognitive radio networks with variational distance secrecy constraint
- 2014
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Ingår i: 2014 IEEE Globecom Workshops, GC Wkshps 2014. - : IEEE. - 9781479974702 ; , s. 1337-1342
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the cooperative secure communication in a four-node cognitive channel where the secondary receiver is treated as a potential eavesdropper with respect to the primary transmission with variational distance constraint. And the primary user's secrecy rate is required to be unchanged. We propose the clean relaying with the cooperative jamming scheme to achieve this goal, where the secondary transmitter splits its transmitting phase into two non-overlapped intervals after successfully decoding the primary message. Due to the considered secrecy metric, we resort to the information spectrum method, to derive the achievable secrecy rates for the primary user. Then we formulate the secondary user's rate maximization problem over the power allocation and time splitting at the cognitive transmitter under the constraint that primary user's secrecy rate is unchanged. Numerical results show that the secondary transmitter can choose clean relaying or pure cooperative jamming according to the relative positions of the nodes to achieve better performance than the one without any clean phase.
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| 10. |
- Perotti, Alberto G., et al.
(författare)
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Downlink Overloaded Multiple Access Based on Constellation Expansion
- 2015
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Ingår i: 2014 IEEE Globecom Workshops. - Piscataway, Nj : IEEE Communications Society. - 9781479974702 ; , s. 977-982
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Konferensbidrag (refereegranskat)abstract
- A new overloaded multiple access scheme for the downlink of wireless systems is presented. It performs simultaneous transmission of multiple data streams intended for users experiencing similar signal-to-noise ratios (SNR). The proposed scheme performs stream multiplexing by mapping the coded bits of each stream onto the labels of an expanded constellation according to a time-varying pattern designed for providing the same level of protection against errors to all streams. Using this scheme, multiple data streams can be concurrently transmitted on the same time-frequency resource blocks of OFDMA systems, thus achieving a higher aggregate spectral efficiency and tighter delay constraints.
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