| 1. |
- D’Amico, Valeria, et al.
(författare)
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EU FP7 INFSO-ICT-247223 ARTIST4G, D1.2 Innovative advanced signal processing algorithms for interference avoidance
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document provides an overview of the proposed innovations and activities in Task 1.1 of Work Package 1 (WP1) of the ARTIST4G project, related to interference avoidance. Focus is on the technical approaches applicable at the physical layer, which are grouped into four different classes of innovations related to single-cell multi-user MIMO schemes, multi-cell multi-user MIMOschemes, advanced 3D beamforming and enabling functionalities. Descriptions of the proposed innovations are given including basic ideas, potential of performance, simulation results, realization options and possible implementation restrictions.
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| 2. |
- D’Amico, Valeria, et al.
(författare)
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EU FP7 INFSO-ICT-247223 ARTIST4G, D1.4 Interference Avoidance Techniques and System Design
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this document we provide performance assessments of the most promising techniques that were studied within Work Package 1 (WP1) of the ARTIST4G project related to interference avoidance. The results are based on evolved techniques that were identified and classified in deliverable D1.1 and investigated in deliverable D1.2 and D1.3, as well as novel alternative techniques that are introduced and assessed in this document.Based on the insights from these performance results we provide a synthetic perspective over the most promising solutions for interference avoidance. We argue that these solutions can reach a satisfactory trade-off in terms of performance benefits vs complexity of implementation. Some of these techniques are also identified as complementary techniques towards an integrated interference avoidance concept.
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| 3. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
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Frequency Allocation in Non-Coherent Joint Transmission CoMP Networks
- 2014
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Ingår i: 2014 IEEE International Conference on Communications Workshops, ICC 2014. - 9781479946402 ; , s. 610-615
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the problem of joint transmission (JT) in coordinated multipoint (CoMP) networks from a new point of view where the system performance is optimized via frequency allocation for 5G small cells. Moreover, we investigate the implementation of hybrid automatic repeat request (HARQ), as an efficient scheme facing the feedback load problem in CoMP setups. The results are obtained for the cases with slow and fast fading conditions. Considering the channel state information (CSI) only at the receiver, we show that at low and medium signal to noise ratios (SNRs) sharing the frequency resources between users outperforms the case when the frequency resources are dedicated under non-coherent JT-CoMP setting. We find that the maximum long term throughput is achieved by either sharing the entire frequency resources between the users or allocating each user in a disjoint dedicated frequency resource. These extreme cases show the best performance in the SNR region of interest. Finally, as demonstrated analytically and numerically, HARQ feedback increases the long term throughput and reduces the outage probability substantially, with an affordable average delay.
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| 4. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Partial joint processing for frequency selective channels
- 2010
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424435746
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider a static cluster of base stations where joint processing is allowed in the downlink. The partial joint processing scheme is a user-centric approach where subclusters or active sets of base stations are dynamically defined for each user in the cluster. In frequency selective channels, the definition of the subclusters or active set thresholding of base stations can be frequency adaptive (per resource block) or non-adaptive (averaged over all the resource blocks). Frequency adaptive thresholding improves the average sum-rate of the cluster, but at the cost of an increased user data interbase information exchange with respect to the non-adaptive frequency thresholding case. On the other hand, the channel state information available at the transmitter side to design the beamforming matrix is very limited and rank deficiency problems arise for low values of active set thresholding and users located close to the base station. To solve this problem, an algorithm is proposed that defines a cooperation area over the cluster where the partial joint processing scheme can be performed, frequency adaptive or non-adaptive, for a given active set threshold value.
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| 5. |
- Aydin, Osman, et al.
(författare)
-
EU FP7 INFSO-ICT-317669 METIS, D 4.1 Summary on preliminary trade-off investigations and first set of potential network-level solutions
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- METIS WP4 covers research activities in network-level aspects of the advancement of wireless network technologies towards the year 2020 and beyond. The aim is to develop novel network-level technology concepts to address the challenges foreseen in future scenarios with regard to interference, traffic and mobility management issues. Moreover, another task of this work package is to propose functional enablers which can support the above potential solutions.This document provides* a report of the ongoing progress in WP4 regarding the research topics agreed upon in IR 4.1,* a high level description of the proposed concepts and approaches adopted by different partners.More specifically, the document describes, first set of potential network-level solutions and presents some first research results in order to position them with regards to the state of the art approaches. It also gives an overview of research activities to be considered later in WP4.
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| 6. |
- Aydin, Osman, et al.
(författare)
-
EU FP7 INFSO-ICT-317669 METIS, D4.2 Final report on trade-off investigations
- 2014
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Research activities in METIS WP4 include several aspects related to the network-level of future wireless communication networks. Thereby, a large variety of scenarios is considered and solutions are proposed to serve the needs envisioned for the year 2020 and beyond. This document provides vital findings about several trade-offs that need to be leveraged when designing future network-level solutions. In more detail, it elaborates on the following trade-offs:• Complexity vs. Performance improvement• Centralized vs. Decentralized• Long time-scale vs. Short time-scale• Information Interflow vs. Throughput/Mobility enhancement• Energy Efficiency vs. Network Coverage and CapacityOutlining the advantages and disadvantages in each trade-off, this document serves as a guideline for the application of different network-level solutions in different situations and therefore greatly assists in the design of future communication network architectures.
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| 7. |
- Botella Mascarell, Carmen, 1979, et al.
(författare)
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EU FP7 INFSO-ICT-247223 ARTIST4G, D1.3 Innovative scheduling and cross-layer design techniques for interference avoidance
- 2011
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document provides an overview of the proposed innovations and activities in Task 1.2 of Work Package 1 (WP1) of the ARTIST4G project, related to interference avoidance. Focus is on the technical approaches applicable at layer 2, which are grouped into five different classes of innovations related to clustering & user grouping, inter-cell interference coordination, coordinated scheduling, scheduling for joint processing and gametheory based scheduling. Descriptions of the proposed innovations are given including basic ideas, potential of performance, simulation results, realization options and possible implementation restrictions.
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| 8. |
- Calabuig, D., et al.
(författare)
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Resource and Mobility Management in the Network Layer of 5G Cellular Ultra-Dense Networks
- 2017
-
Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 55:6, s. 162-169
-
Tidskriftsartikel (refereegranskat)abstract
- The provision of very high capacity is one of the big challenges of the 5G cellular technology. This challenge will not be met using traditional approaches like increasing spectral efficiency and bandwidth, as witnessed in previous technology generations. Cell densification will play a major role thanks to its ability to increase the spatial reuse of the available resources. However, this solution is accompanied by some additional management challenges. In this article, we analyze and present the most promising solutions identified in the METIS project for the most relevant network layer challenges of cell densification: resource, interference and mobility management.
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| 9. |
- Carvalho, E. de, et al.
(författare)
-
EU FP7 INFSO-ICT-317669 METIS, D3.1 Positioning of multi-node/multi-antenna technologies
- 2013
-
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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| 10. |
- Fantini, R, et al.
(författare)
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EU FP7 INFSO-ICT-317669 METIS, D3.2 First performance results for multi-node/multi-antenna transmission technologies
- 2014
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable describes the current results of the multi-node/multi-antenna technologies investigated within METIS and analyses the interactions within and outside Work Package 3. Furthermore, it identifies the most promising technologies based on the current state of obtained results. This document provides a brief overview of the results in its first part. The second part, namely the Appendix, further details the results, describes the simulation alignment efforts conducted in the Work Package and the interaction of the Test Cases. The results described here show that the investigations conducted in Work Package 3 are maturing resulting in valuable innovative solutions for future 5G systems.
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| 11. |
- Lakshmana, Tilak Rajesh, 1980
(författare)
-
Coordinated MultiPoint Transmission with Incomplete Information
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand for higher data rates and efficient use of various resources has been an unquenchable thirst across different generations of cellular systems, and it continues to be so. Aggressive reuse of frequency resources in cellular systems gives rise to intercell interference which severely affects the data rate of users at the cell-edge. In this regard, coordinated multipoint (CoMP) is one of the ways to mitigate interference for these cell-edge users. In the downlink, joint transmission (JT) CoMP involves the cooperation of two or more geographically separated base stations to jointly transmit to these users by treating the interfering signal as useful signal.To realize the gains of JT-CoMP in a frequency division duplex system, the users need to feedback the channel state information (CSI) to its serving base station. This needs to be aggregated at the central coordination node for mitigating interference via precoding. However, the process of aggregation poses tremendous burden on the backhaul. One of the ways to reduce this burden is to use relative thresholding, where the users feed back the CSI of only those links that fall within a threshold relative to the strongest base station. The side effect of thresholding results in limited or incomplete CSI for precoding. Efficient backhauling is achieved when the quantity of CSI available for certain links at the central coordination node be correspondingly equivalent to the quantity of precoding weights generated for the same links. The incomplete CSI poses problems for the simple zero-forcing precoder to mitigate interference and also achieve efficient backhauling. In this thesis, the main problem of simultaneously mitigating interference and achieving efficient backhauling is addressed with a layered approach. Our physical (PHY) layer precoding approach solves the problem and allowes the medium access control (MAC) layer scheduler to be simple. The PHY layer precoding algorithms such as successive second order cone programming are proposed using convex optimization in [Paper A], and particle swarm optimization based on stochastic optimization is proposed in [Paper B]. Also, we exploit the use of long term channel statistics for the incomplete CSI and characterize the promising performance of the proposed precoder using numerical bounds. Based on our results, we observed that the swarm algorithm struggles with the increase in the problem size. The MAC layer approach exploits scheduling to solve the problem keeping a simple PHY layer zero-forcing precoder [Paper C]. Our proposed constrained scheduling approach provides the best tradeoff in terms of average sum rate per backhaul use compared to other MAC layer techniques. These results can be applied to a variant of the baseband hotel, a centralized architecture. In a distributed architecture, the CSI is exchanged periodically between the base stations over the backhaul for JT-CoMP. Any CSI feedback update from the user must be immediately exchanged over the backhaul to preserve the gains of JT-CoMP. We propose an improved decentralized local precoder design where the base station with new local CSI can design the local precoding weights in between the CSI exchange between base stations [Paper D]. With our approach some of the gains of JT-CoMP can still be preserved without the need to burden the backhaul.
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| 12. |
- Lakshmana, Tilak Rajesh, 1980
(författare)
-
Efficient Backhauling in Cooperative MultiPoint Cellular Networks
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The efficient use of the spectrum in cellular systems has given rise to cell-edge user equipments (UEs) being prone to intercell interference. In this regard, coordinated multipoint (CoMP) transmission is a promising technique that aims to improve the UE data rates. In a centralized network architecture, the users need to feed back the channel state information (CSI) to its anchor base station (BS). The CSI is then forwarded to a central coordination node (CCN) for precoder design to jointly mitigate interference. However, feeding back the CSI consumes over-the-air uplink resources as well as backhaul resources. To alleviate this burden, the quantity of CSI being fed back is limited via relative thresholding. That is, the CSI feedback is limited to those BSs whose signal strength fall above a threshold relative to the strongest BS. Moreover, with limited CSI, efficient backhauling of the precoding weights is necessary, as the user data is routed based on the path taken by the precoding weights from the CCN to the corresponding BSs. The focus of this thesis is mainly on a physical (PHY) layer and a medium access control (MAC) layer approach for reducing the backhaul load in a CoMP system, with minimal penalty on the potential CoMP gains. Furthermore, broadcasting the CSI in a decentralized network architecture is considered in order to reduce backhaul latency.In the PHY layer approach, the precoder design is based on stochastic optimization such as particle swarm optimization (PSO). This method has no constraints on the scheduling of the UEs. The PSO based precoder design was also applied to field measurement data with CSI imperfections due to prediction errors and quantization errors. It was found to perform the best compared to other robust precoders de- veloped in the EU FP7 ARTIST4G consortium. With the MAC layer approach, a simple zero forcing precoder is assumed, which focuses on how to schedule the UEs in such a way that they achieve the backhaul load reduction. Lastly, the decentralized network architecture is explored, where the UEs broadcast the CSI. The BSs coordinate by sharing minimal scheduling information, thereby achieving data rates comparable to the centralized network architecture.In this thesis, the backhauling is defined to be efficient when the total number of CSI coefficients aggregated at the CCN is equal to the total number of precoding weights for a given time-frequency resource, in a centralized architecture with the PHY layer approach. In the MAC layer approach, the total number of precoding weights is less than or equal to the total number of CSI coefficients. In the decentralized network architecture, the CCN does not exist. The BSs can coordinate over a less stringent backhaul, thereby reducing the backhaul load and latency.
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| 13. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Improved Local Precoder Design for JT-CoMP With Periodical Backhaul CSI Exchange
- 2016
-
Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 20:3, s. 566 - 569
-
Tidskriftsartikel (refereegranskat)abstract
- Joint transmission (JT) in coordinated multipoint (CoMP) systems can be used to significantly improve the data rate of the cell-edge users (UEs) via cooperation of base stations (BSs). In a frequency division duplex system, the UEs need to feedback the channel state information (CSI) to its strongest BS. In a distributed JT-CoMP setup, the exchanging of CSI can occur periodically over the backhaul. Any feedback of CSI would need to trigger immediate exchange of CSI among the BSs to preserve the gains of JT-CoMP. We propose to utilize the newly available local CSI to locally improve the precoding performance. This is performed in-between the triggered periodic CSI exchange between BSs. We characterize the performance between exchanging and not exchanging the CSI for local precoder design (LPD) in terms of the average sum rate with UE mobility and different feedback intervals. We solve the decentralized LPD for weighted sum rate maximization with partial new CSI, and show that significant part of the JT-CoMP gains can still be preserved.
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| 14. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
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On the Potential of Broadcast CSI for Opportunistic Coordinated Multi-Point Transmission
- 2012
-
Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. - 9781467325691 ; , s. 1262-1267
-
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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| 15. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Partial Joint Processing with Efficient backhauling in Coordinated MultiPoint Networks
- 2012
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781467309905
-
Konferensbidrag (refereegranskat)abstract
- Joint processing between base stations is a promising technique to improve the quality of service to users at the cell edge, but this technique poses tremendous requirements on the backhaul signaling capabilities. Partial joint processing is a technique aimed to reduce feedback load, in one approach the users feed back the channel state information of the best links based on a channel gain threshold mechanism. However, it has been shown in the literature that the reduction in the feedback load is not reflected in an equivalent backhaul reduction unless additional scheduling or precoding techniques are applied. The reason is that reduced feedback from users yields sparse channel state information at the Central Coordination Node. Under these conditions, existing linear precoding techniques fail to remove the interference and reduce backhaul, simultaneously, unless constraints are imposed on scheduling. In this paper, a partial joint processing scheme with efficient backhauling is proposed, based on a stochastic optimization algorithm called particle swarm optimization. The use of particle swarm optimization inthe design of the precoder promises efficient backhauling with improved sum rate.
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| 16. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Partial joint processing with efficient backhauling using particle swarm optimization
- 2012
-
Ingår i: Eurasip Journal on Wireless Communications and Networking. - : Springer Science and Business Media LLC. - 1687-1499 .- 1687-1472. ; 2012
-
Tidskriftsartikel (refereegranskat)abstract
- In cellular communication systems with frequency reuse factor of one, user terminals(UT) at the cell-edge are prone to intercell interference. Joint processing is one of the coordinated multipoint transmission techniques proposed to mitigate this interference. In the case of centralized joint processing, the channel state information fed back by the users need to be available at the central coordination node for precoding. The precoding weights (with the user data) need to be available at the corresponding base stations to serve the UTs. These increase the backhaul traffic. In this article, partial joint processing (PJP) is considered as a general framework that allows reducing the amount of required feedback. However, it is difficult to achieve a corresponding reduction on the backhaul related to the precoding weights, when a linear zero forcing beamforming technique is used. In this work, particle swarm optimization is proposed as a tool to design the precoding weights under feedback and backhaul constraints related to PJP.The precoder obtained with the objective of weighted interference minimization allows some multiuser interference in the system, and it is shown to improve the sum rate by 66% compared to a conventional zero forcing approach, for those users experiencing low signal to interference plus noise ratio.
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| 17. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Precoder Design With Incomplete Feedback for Joint Transmission
- 2016
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 15:3, s. 1923-1936
-
Tidskriftsartikel (refereegranskat)abstract
- A centralized coordinated multipoint downlink joint transmission in a frequency division duplex system requires channel state information (CSI) to be fed back from the cell-edge users to their serving BS, and aggregated at the central coordination node for precoding, so that interference can be mitigated. The control signals comprising of CSI and the precoding weights can easily overwhelm the backhaul resources. Relative thresholding has been proposed to alleviate the burden; however, this is at the cost of reduction in throughput. In this paper, we propose utilizing the long term channel statistics comprising of pathloss and shadow fading in the precoder design to model the statistical interference for the unknown CSI. In this regard, a successive second order cone programming (SSOCP) based precoder for maximizing the weighted sum rate is proposed. The accuracy of the solution obtained is bounded with the branch and bound technique. An alternative optimization framework via weighted mean square error minimization is also derived. Both these approaches provide an efficient solution close to the optimal, and also achieve efficient backhauling, in a sense that the precoding weights are generated only for the active links. For comparison, a stochastic approach based on particle swarm optimization is also considered.
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| 18. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
-
Scheduling for Backhaul Load Reduction in CoMP
- 2013
-
Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. - 9781467359399 ; , s. 227-232
-
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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| 19. |
- Tahmasebi Toyserkani, Arash, 1978, et al.
(författare)
-
A Low-Complexity Semi-Analytical Approximation to the Block Error Rate in Nakagami-m Block Fading Channels
- 2010
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424435746
-
Konferensbidrag (refereegranskat)abstract
- There are few analytical formulas that can be usedfor calculating the block error rate (BLER) in block fadingchannels. Thus, an estimate of the BLER is often obtained usingnumerical methods. One such method is the threshold methodwhich assigns 0 or 1 to the instantaneous BLER given the signalto noise ratio (SNR) level. It has been shown that utilizing sucha method results in an accurate approximation of the BLER inNakagami-m block fading channels for a wide range of m.In this work, we consider a recently proposed simple method ofobtaining the threshold and study the effect of adopting differentphysical layer and channel parameters on that threshold. Weshow that, while the value of this threshold depends on themodulation, coding, and block size, it is almost unaffected bythe m parameter of Nakagami-m channels for a wide range ofpractical values. In addition, for a given modulation and codingmethod, the threshold is shown to be a simple function of blocksize. As a result, the computational complexity required to obtainthe threshold can be significantly reduced.
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