| 1. |
- Björnson, Emil, Professor, 1983-, et al.
(author)
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On the impact of transceiver impairments on af relaying
- 2013
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In: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 4948-4952, s. 4948-4952
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Conference paper (peer-reviewed)abstract
- Recently, it was shown that transceiver hardware impairments have a detrimental impact on the performance of communication systems, especially for high-rate systems. The vast majority of technical contributions in the area of relaying assume ideal transceiver hardware. This paper quantifies the impact of transceiver hardware impairments in dual-hop Amplify-and-Forward (AF) relaying, both for fixed and variable gain relays. The outage probability (OP) in this practical scenario is a function of the instantaneous end-to-end signal-to-noise-and-distortion ratio (SNDR). This paper derives closed-form expressions for the exact and asymptotic OPs under Rayleigh fading, accounting for hardware impairments at both the transmitter and the relay. The performance loss is small at low spectral efficiency, but can otherwise be very substantial. In particular, it turns out that for high signal-to-noise ratio (SNR), the instantaneous end-to-end SNDR converges to a deterministic constant, called the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in stark contrast to the ideal hardware case for which the end-to-end SNDR grows without bound in the high SNR regime.
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| 2. |
- Carvalho, E. de, et al.
(author)
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EU FP7 INFSO-ICT-317669 METIS, D3.1 Positioning of multi-node/multi-antenna technologies
- 2013
-
Reports (other academic/artistic)abstract
- This document describes the research activity in multi-node/multi-antenna technologies within METIS and positions it with respect to the state-of-the-art in the academic literature and in the standardization bodies. Based on the state-of-the-art and as well as on the METIS objectives,we set the research objectives and we group the different activities (or technology components) into research clusters with similar research objectives. The technologycomponents and the research objectives have been set to achieve an ambidextrous purpose. On one side we aim at providing the METIS system with those technological components that are a natural but non-trivial evolution of 4G. On the other side, we aim at seeking for disruptivetechnologies that could radically change 5G with respect to 4G. Moreover, we mapped the different technology components to METIS’ other activities and to the overall goals of theproject.
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| 3. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(author)
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Scheduling for Backhaul Load Reduction in CoMP
- 2013
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In: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. - 9781467359399 ; , s. 227-232
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Conference paper (peer-reviewed)abstract
- Coordinated multi-point (CoMP) transmission has received a lot of attention, as a way to improve the system throughput in an interference limited cellular system. For joint processing in CoMP, the user equipments (UEs) need to feed back the channel state information (CSI), typically to their serving base stations (BSs). The BS forwards the CSI to a central coordination node (CCN) for precoding. These precoding weights need to be forwarded from the CCN to the corresponding BSs to serve the UEs. In this work, a feedback load reduction technique is employed via partial joint processing to alleviate the CSI feedback overhead. Similarly, to achieve backhaul load reduction due to the precoding weights, scheduling approaches are proposed. The state of the art block diagonalization solution is compared with our proposed constrained and unconstrained scheduling. Our main contribution is the method of choosing the best subset of the BSs and UEs at the CCN that yields the best sum rate under the constraint of efficient backhaul use. In particular, with constrained scheduling, the choice of a smaller subset proportionally reduces the backhaul load. Simulation results based on a frequency selective WINNER II channel model, show that our proposed constrained scheduling outperforms the block diagonalization approach in terms of the average sum rate per backhaul use.
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| 4. |
- Matthaiou, Michail, 1981, et al.
(author)
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Two-Way Relaying Under the Presence of Relay Transceiver Hardware Impairments
- 2013
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In: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2558 .- 1089-7798. ; 17:6, s. 1136-1139
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Journal article (peer-reviewed)abstract
- Hardware impairments in physical transceivers are known to have a deleterious effect on communication systems; however, very few contributions have investigated their impact on relaying. This paper quantifies the impact of transceiver impairments in a two-way amplify-and-forward configuration. More specifically, the effective signal-to-noise-and-distortion ratios at both transmitter nodes are obtained. These are used to deduce exact and asymptotic closed-form expressions for the outage probabilities (OPs), as well as tractable formulations for the symbol error rates (SERs). It is explicitly shown that non-zero lower bounds on the OP and SER exist in the high-power regime-this stands in contrast to the special case of ideal hardware, where the OP and SER go asymptotically to zero.
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| 5. |
- Mayer, Zoltán, et al.
(author)
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On the Impact of Backhaul Channel Reliability on Cooperative Wireless Networks
- 2013
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In: IEEE International Conference on Communications. - 1550-3607. - 9781467331227 ; , s. 5284-5289
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Conference paper (peer-reviewed)abstract
- We study the effect of unreliable backhaul links on the performance of Coordinated Multi-Point (CoMP) techniques. CoMP has emerged as a powerful scheme to mitigate co-channel interference. Economically viable deployment of Heterogeneous Networks (HetNets) will require the use of lower-performance backhaul options, e.g. non-line-of-sight microwave links. Motivated by HetNets, a backhauling model is introduced, by assigning Link Failure Probability (LFP) to backhaul links, for the cooperative clusters. In this paper we analyze the centralized and semi-distributed CoMP architectures. We investigate the probability of deficient backhaul links reducing quality of service, by impeding transmission. By valuating the average sum rate of users within a CoMP cluster, we show how backhaul link reliability affects the performance of the cooperative cluster. We conclude, that the performance gains offered by CoMP quickly diminish, as the unreliability of the backhaul links grows.
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| 6. |
- Yutao, Sui, 1984, et al.
(author)
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Moving cells : A promising solution to boost performance for vehicular users
- 2013
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In: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 51:6, s. 62-68
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Journal article (peer-reviewed)abstract
- In future wireless networks, a significant number of users accessing wireless broadband will be vehicular (i.e., in public transportation vehicles like buses, trams, or trains). The Third Generation Partnership Project has started to investigate how to serve these vehicular users cost-effectively, and several solutions have been proposed. One promising solution is to deploy a moving relay node (MRN), on a public transportation vehicle that forms its own cell inside the vehicle to serve vehicular users. By proper antenna placement, an MRN can reduce or even eliminate the vehicular penetration loss that affects communication. Moreover, MRNs can exploit various smart antenna techniques and advanced signal processing schemes, as they are less limited by size and power than regular user equipment. However, there are also challenges in using MRNs, such as designing efficient interference management techniques as well as proper mobility management schemes to exploit the benefit of group handovers for vehicular UE devices served by the same MRN. Nevertheless, initial system-level evaluation results indicate that a dedicated MRN deployment shows great potential to improve the vehicular user experience, and thereby can potentially bring significant benefits to future wireless communication systems.
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| 7. |
- Yutao, Sui, 1984, et al.
(author)
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The energy efficiency potential of moving and fixed relays for vehicular users
- 2013
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In: IEEE Vehicular Technology Conference. - 1550-2252. - 9781467361873
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Conference paper (peer-reviewed)abstract
- In future wireless networks a significant number of wireless broadband users will be vehicular, i.e., they will be in public transportation vehicles like buses, trams or trains. In this paper, we show that the efficient use of relay nodes to serve vehicular users can greatly improve the energy efficiency of the network while maintaining the required quality-of-service (QoS). We consider vehicular users moving along a road within the coverage of a base station (BS). Communication can take place in a single-hop fashion (baseline case) or can be assisted by a single relay node (dual-hop), which can either be a fixed relay node (FRN) deployed at a specific position on the road or a moving relay node (MRN) mounted on top of the vehicle. We compare the required overall transmit energy for direct transmission, FRN and MRN assisted transmission in a noise limited system under Rayleigh fading while assuming an outage probability (OP) target. A lower bound is derived for the required energy of the FRN assisted transmission. It is shown that as the vehicular penetration loss (VPL) increases, both FRN and MRN assisted transmission can significantly lower the overall transmit energy compared to the conventional one-hop case. Moreover, transmission relying on an MRN outperforms the FRN assisted case when VPL is moderate to high.
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