| 1. |
- Alexandropoulos, G. C., et al.
(författare)
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A Comparative Study of Relaying Schemes with Decode and Forward over Nakagami-m Fading Channels
- 2011
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Ingår i: Journal of Computer Networks and Communications. - : Hindawi Limited. - 2090-715X .- 2090-7141. ; 2011
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Tidskriftsartikel (refereegranskat)abstract
- Although relaying can be very beneficial for wireless systems, understanding which relaying schemes can achieve specific performance objectives under realistic fading is crucial. In this paper we present a general framework for modeling and evaluating the performance of dual-hop decode-and-forward (DF) relaying schemes over independent and not necessarily identically distributed (INID) Nakagami-m fading channels. We obtain closed-form expressions for the statistics of the instantaneous output signal-to-noise ratio of repetitive transmission with selection diversity. Furthermore, we present a unified statistical overview of other three significant relaying schemes with DF, one based on repetitive transmission with maximal-ratio diversity and the other two based on relay selection (RS). To compare the considered schemes, we present closed-form and analytical expressions for the outage probability and the average symbol error probability under various modulation methods, respectively. Importantly, it is shown that when the channel state information for RS is perfect, RS-based schemes always outperform repetitive ones. Furthermore, when the direct link between the source and the destination nodes is sufficiently strong, relaying may not result in any gains, and it should be switched off.
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| 2. |
- Björnson, Emil, Professor, 1983-, et al.
(författare)
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On the impact of transceiver impairments on af relaying
- 2013
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Ingår i: 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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Konferensbidrag (refereegranskat)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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| 3. |
- Burr, Alister, et al.
(författare)
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MIMO Truncated Shannon Bound for System Level Capacity Evaluation of Wireless Networks
- 2012
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Ingår i: IEEE Wireless Communications and Networking Conference, Paris, France, Apr. 2012. - 9781467306829 ; , s. 268-272
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Konferensbidrag (refereegranskat)abstract
- We outline a general method for modelling the capacity of a MIMO link within a wireless, assuming that capacity of a link is a random function of SNR and signal to interference ratio (SIR), since the maximum link throughput depends on the random channel of both the user's signal and the interference. We show how a look-up table for the CDF of this random function can be obtained by link-level simulation in the presence of interference having the same characteristics as the interference found in the target network. We also exploit the Truncated Shannon Bound (TSB) to estimate the resulting capacity obtained in practice in a system using adaptive modulation and coding on the link level.
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| 4. |
- Carvalho, E. de, et al.
(författare)
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EU FP7 INFSO-ICT-317669 METIS, D3.1 Positioning of multi-node/multi-antenna technologies
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)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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| 5. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
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On the Potential of Broadcast CSI for Opportunistic Coordinated Multi-Point Transmission
- 2012
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Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. - 9781467325691 ; , s. 1262-1267
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Konferensbidrag (refereegranskat)abstract
- Coordinated Multi-Point transmission is a promising technique to improve the performance of the users at the cell-edge. To achieve this, in case of a centralized approach, users need to unicast the quantized channel state information (CSI), typically to the anchor base station (BS), and then each BS forwards this information to a central coordination node for precoding and scheduling. In the case of a decentralized approach, users broadcast the quantized CSI such that the coordinating BSs could simultaneously receive the CSI. The advantage of a decentralized approach is that it does not require a central coordination node, thereby not imposing stringent latency constraints on the backhaul. The CSI transmission over the erroneous feedback channel in the uplink gives rise to precoding loss and scheduling loss. In the decentralized framework, the feedback errors could result in BSs receiving a different version of the CSI. In this work, we propose a decentralized opportunistic scheduling approach, which only requires a minimal sharing of scheduling information between BSs. The results show that the sum rate achieved with the proposed method is comparable to that of the centralized approach even when there is a high bit error probability introduced by the feedback channel. We also show that when the bit error probabilities in the feedback channel are less than 10^{-4}, the decentralized approach achieves the sum rate of the centralized approach.
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| 6. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
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Scheduling for Backhaul Load Reduction in CoMP
- 2013
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Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. - 9781467359399 ; , s. 227-232
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Konferensbidrag (refereegranskat)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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| 7. |
- Li, Jingya, 1986, et al.
(författare)
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Performance evaluation of coordinated multi-point transmission schemes with predicted CSI
- 2012
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Ingår i: IEEE Conference on Personal, Indoor and Mobile Radio Communications, PIMRC, Sydney, Australien. - 9781467325691 ; , s. 1055-1060
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Konferensbidrag (refereegranskat)abstract
- Coordinated multi-point (CoMP) transmission is considered as an efficient technique to improve cell-edge performance as well as system spectrum efficiency. In CoMP-enabled systems, a cluster of coordinated base stations (BSs) are typically assumed to be connected to a control unit (CU) via backhaul links, and the provided performance gain relies heavily on the quality of the channel state information (CSI) available at the CU side. In this paper, we consider the downlink of a CoMP cluster and compare three different CoMP transmission schemes: zero-forcing coherent joint transmission, non-coherent joint transmission and coordinated scheduling. Moreover, for each of the analyzed schemes, the performance in terms of average sum rate of the CoMP cluster is studied with predicted CSI, considering the effects of the feedback and backhaul latency, as well as the user mobility. Compared to zero-forcing coherent joint transmission, we show that non-coherent joint transmission and coordinated scheduling are more robust to channel uncertainty. In addition, depending on the latency, user mobility and user locations, different schemes would achieve the highest average sum rate performance. Hence, a system could switch between the transmission schemes to improve the sum rate.
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| 8. |
- Marinchenko, Oleg, et al.
(författare)
-
BuNGee project overview
- 2011
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Ingår i: IEEE International Conference on Microwaves, Communications, Antennas and Electronic Systems (COMCAS 2011). - 9781457716928
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Konferensbidrag (refereegranskat)abstract
- The BuNGee FP7 project is looking at achieving throughput densities substantially higher than available with today‘s systems. The project addresses this goal by a combination of techniques: below-rooftop access base stations and a unique feeding architecture using a combination of licensed in-band and out-of-band license exempt spectrum. Very high capacity feeding hubs with high-order spatial reuse are created using multi-beam antennas and advanced MIMO techniques, using millimeter waves.
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| 9. |
- Matthaiou, Michail, 1981, et al.
(författare)
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Two-Way Relaying Under the Presence of Relay Transceiver Hardware Impairments
- 2013
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Ingår i: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2558 .- 1089-7798. ; 17:6, s. 1136-1139
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Mayer, Zoltán, et al.
(författare)
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On the Impact of Backhaul Channel Reliability on Cooperative Wireless Networks
- 2013
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Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467331227 ; , s. 5284-5289
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Konferensbidrag (refereegranskat)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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