| 1. |
- Björnson, Emil, Professor, 1983-, et al.
(författare)
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Three Practical Aspects of Massive MIMO : Intermittent User Activity, Pilot Synchronism, and Asymmetric Deployment
- 2015
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Ingår i: 2015 IEEE GLOBECOM WORKSHOPS (GC WKSHPS). - : IEEE. - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- This paper considers three aspects of Massive MIMO (multiple-input multiple-output) communication networks that have received little attention in previous works, but are important to understand when designing and implementing this promising wireless technology. First, we analyze how bursty data traffic behaviors affect the system. Using a probabilistic model for intermittent user activity, we show that the spectral efficiency (SE) scales gracefully with reduced user activity. Then, we make an analytic comparison between synchronous and asynchronous pilot signaling, and prove that the choice between these has no impact on the SE. Finally, we provide an analytical and numerical study of the SE achieved with random network deployment.
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| 2. |
- Daniel, Ondrej, et al.
(författare)
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Hybrid Cooperative Positioning in Harsh Environments
- 2015
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Ingår i: IEEE Globecom Workshops. - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- Hybrid cooperative positioning involves the combination of satellite pseudoranges with measurements based on terrestrial radio signals, with the aim to improve both coverage and accuracy. This paper presents a theoretical analysis of hybrid cooperative positioning in low signal-to-noise ratio environments, explicitly accounting for scenarios where receivers can receive signals but cannot decode navigation messages. We propose an extended pseudorange model, suitable for evaluation of measurements made by the receiver in these scenarios, as well as extended cooperation across agents attempting to enable satellite navigation functionality of receivers operating below signal-to-noise ratio threshold required for proper message decoding. The advantages of such extended cooperation are illustrated on a realistic scenario by means of the Cramer-Rao lower bound.
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| 3. |
- Hossain, M. M. Aftab, et al.
(författare)
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Energy-Efficient Load-Adaptive Massive MIMO
- 2015
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Ingår i: 2015 IEEE GLOBECOM WORKSHOPS (GC WKSHPS). - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- Massive MIMO is a promising technique to meet the exponential growth of global mobile data traffic demand. However, contrary to the current systems, energy consumption of next generation networks is required to be load adaptive as the network load varies significantly throughout the day. In this paper, we propose a load adaptive massive MIMO system that varies the number of antennas following the daily load profile (DLP) in order to maximize the downlink energy efficiency (EE). A multi- cell system is considered where each base station (BS) is equipped with a large number of antennas to serve many single antenna users. In order to incorporate DLP, each BS is modeled as an M/G/m/m state dependent queue under the assumption that the network is dimensioned to serve a maximum number of users at the peak load. For a given number of users in a cell, the optimum number of active antennas maximizing EE is derived. The EE maximization problem is formulated in a game theoretic framework where the number of antennas to be used by a BS is determined through best response iteration. This load adaptive system achieves overall 19% higher EE compared to a baseline system where the BSs always run with the fixed number of antennas that is most energy efficient at peak load and that can be switched-off when there is no traffic.
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| 4. |
- Huang, Yezi, et al.
(författare)
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Rate-Boosting Using Strong Crosstalk in Next Generation Wireline Systems
- 2016
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Ingår i: 2015 IEEE Global Communications Conference (GLOBECOM). - 9781467395267 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Next-generation wireline systems may exploit fre- quencies up to several hundred MHz on short lines. Strong crosstalk coupling, comparable to the direct paths, is one of the main channel characteristics at high frequencies. Instead of fully cancelling all crosstalk, we utilize strong crosstalk paths to boost data-rate for active users. Two linear precoding schemes, based on maximum ratio-combining (MRC) and convex optimization, respectively, are proposed and applied to a common network topology. The precoding schemes exploit constructive crosstalk signals on unused lines or in unused parts of the spectrum on neighboring lines to boost data-rate while still complying with the regulated spectral power limits per line. More than 500 Mbps throughput gain per active user can be achieved compared to state-of-the-art linear precoding.
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| 5. |
- Karaca, Mehmet, et al.
(författare)
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An Opportunistic Backoff Scheme for Dense IEEE 802.11 WLANs
- 2016
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Ingår i: Proc. of the IEEE GLOBECOM'15 WS Enabling Technologies in Future Wireless Local Area Network (ETFWLALN). - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- In dense deployments, the performance of IEEE 802.11 Wireless Local Area Networks (WLANs) depends on the development of efficient contention resolution mechanisms since the collision probability can be high even with low number of users with the current 802.11 MAC mechanism. Also, the current 802.11 MAC is not opportunistic in the sense that it does not consider channel quality and traffic load of users, which can greatly degrade the network capacity. In this paper, we propose a new backoff scheme which performs well for dense networks resulting in low collision probability. Also, our backoff scheme opportunistically gives higher priority to users with high traffic load and better channel conditions, and thus reduces unnecessary contention. We analytically show that the performance of our backoff algorithm can be pushed to the maximum throughput in exchange for longer backoff delay, which is compensated with reduced number of collisions. We evaluate our algorithm in OMNeT++, and show that compared to the legacy 802.11 Distributed coordination Function (DCF) the aggregated network throughput can be increased up to 70\% by using our algorithm. Also, compared with legacy DCF, the maximum number of supportable users is much higher and the end-to-end delay performance is better with our backoff scheme for dense scenarios under the same traffic conditions.
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| 6. |
- Ploumidis, Manolis, et al.
(författare)
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Performance of Flow Allocation with Successive Interference Cancelation for Random Access WMNs
- 2015
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Ingår i: 2015 IEEE Globecom Workshops (GC Wkshps). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467395267 ; , s. 1-7
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Konferensbidrag (refereegranskat)abstract
- In this study we explore the gain that can be achieved by jointly allocating flow on multiple paths and employing successive interference cancelation (SIC), for random access wireless mesh networks with multi-packet reception capabilities. More precisely, we explore a distributed flow allocation scheme aimed at maximizing average aggregate flow throughput, while also providing bounded delay, when SIC is employed. Simulation results derived from three illustrative topologies show that the gain over treating interference as noise (IAN) for this scheme can be up to 15.2%, for an SINR threshold value equal to 0.5. For SINR threshold values as high as 2.0 however, SIC does not always result in higher throughput. In some scenarios explored, the gain of SIC over IAN is insignificant, while in some others treating interference as noise proves better. The reason is that, although SIC improves the throughput on a specific link, it also increases the interference imposed on neighbouring receivers. We also show that, the gain of applying SIC is more profound in cases of a large degree of asymmetry among interfering links.
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| 7. |
- Seifi, Nima, 1981, et al.
(författare)
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Elevation plane spatial multicell interference mitigation with No CSI sharing
- 2015
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Ingår i: IEEE Globecom Workshops, GC Wkshps 2015, San Diego, United States, 6-10 December 2015. - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- We study downlink transmission in a cellular network with multi-antenna base stations (BSs) and single-antenna users. We propose a novel coordinated transmission strategy that controls the intercell interference (ICI) via exploiting the elevation plane of the wireless channel. The key idea is to divide the area of each cell into two disjoint vertical regions and to serve the non-adjacent vertical regions in the neighboring cells according to a set of pre-determined coordinated transmission patterns. A scheduler is used to dynamically allocate the available time-slots among transmission patterns. By appropriately adapting the elevation angle of the antenna main beam, denoted as tilt, at the BSs in each pattern, ICI can be effectively suppressed. Unlike the state-of-the-art coordinated transmission schemes, the proposed technique requires no channel state information sharing among BSs and/or infeasible BS tilting capabilities, but achieves comparable performance.
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| 8. |
- Serror, Martin, et al.
(författare)
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Channel Coding vs. Cooperative ARQ : Reducing Outage Probability in Ultra-Low Latency Wireless Communications
- 2015
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Ingår i: 2015 IEEE Globecom Workshops, GC Wkshps 2015 - Proceedings. - : IEEE conference proceedings. - 9781467395267 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Nowadays wireless communications still lack the ability to provide high reliability and low latency, although mission-critical applications, such as found in industrial automation, rely on both requirements. The main challenge is that an improved reliability often comes at the price of an increased latency. It has been shown that cooperative schemes can effectively increase the reliability by leveraging spatial diversity. However, an important question remains how to integrate cooperative schemes when dealing with very short latency bounds and especially how much time should be reserved for potential retransmissions. In this work, we propose and evaluate a centralized communication system that uses cooperative ARQ to achieve high reliability under the constraint of a strict latency bound of 1 ms. We evaluate this system analytically, using an outage-capacity model with average channel state information, by varying the reserved time for retransmissions, where a shorter time for retransmissions allows to apply stronger channel codes in the original transmission. As a baseline, we use a system without cooperation mechanism, thus applying the given time for stronger channel codes in the direct transmission of a message. In case of cooperation, a third station may act as a relay if the original transmission failed. Our results reveal that an optimal size of the reserved retransmission time exists around 15% to 30% of the total frame time, increasing the reliability by several orders of magnitude, even for a large number of transmissions within a communication cycle.
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| 9. |
- Shahmansoori, Arash, et al.
(författare)
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5G Position and Orientation Estimation through Millimeter Wave MIMO
- 2015
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Ingår i: IEEE Globecom Workshops. - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- Millimeter wave and massive MIMO are considered enabling technologies for future 5G networks. While their benefits for achieving high-data rate communications are well-known, their potential advantages for accurate positioning are largely undiscovered. We derive sufficient conditions under which transmission from a single mm-wave base station leads to a non-singular Fisher information matrix associated with the position and orientation of a user terminal equipped with multiple antennas, which is in turn a prerequisite for joint estimation of the position and orientation.
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| 10. |
- Steinmetz, Erik, et al.
(författare)
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A stochastic geometry model for vehicular communication near intersections
- 2015
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Ingår i: 2015 IEEE Globecom Workshops (GC Wkshps). - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- Many traffic-related applications require the nodes in a vehicular ad-hoc network (VANET) to periodically broadcast their state information. As measurements campaigns or simulations to evaluate the reliability of packet transmission are slow and scenario-specific, we present an analytic performance assessment tool that accounts for the spatial statistics of the nodes on a road, in a scenario of crossing roads and fast fading. Based on stochastic geometry, our tool is able to capture a static two-dimensional road geometry and the effect of interference due to node clustering in the vicinity of an intersection. Numerical results reveal how packet transmission is affected as the receiver gets closer to the intersection.
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| 11. |
- Zhang, Siwei, et al.
(författare)
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Location-Aware Formation Control in Swarm Navigation
- 2015
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Ingår i: IEEE Globecom Workshops. - 9781467395267
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Konferensbidrag (refereegranskat)abstract
- Goal-seeking and information-seeking are canonical problems in mobile agent swarms. We study the problem of collaborative goal-approaching under uncertain agent position information. We propose a framework that establishes location-aware formations, resulting in a controller that accounts for agent position uncertainty with a realistic ranging model. Simulation results confirm that, as the outcome of the controller, the swarm moves towards its goal, while emerging formations conducive to high-quality localization.
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