| 1. |
- Brandt, Rasmus, 1985-, et al.
(author)
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Distributed Long-Term Base Station Clustering in Cellular Networks using Coalition Formation
- 2016
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In: IEEE TRANSACTIONS ON SIGNAL AND INFORMATION PROCESSING OVER NETWORKS. - : IEEE. - 2373-776X. ; 2:3
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Journal article (peer-reviewed)abstract
- Interference alignment (IA) is a promising technique for interference mitigation in multicell networks due to its ability to completely cancel the intercell interference through linear precoding and receive filtering. In small networks, the amount of required channel state information (CSI) is modest and IA is therefore typically applied jointly over all base stations. In large networks, where the channel coherence time is short in comparison to the time needed to obtain the required CSI, base station clustering must be applied however. We model such clustered multicell networks as a set of coalitions, where CSI acquisition and IA precoding is performed independently within each coalition. We develop a long-term throughput model which includes both CSI acquisition overhead and the level of interference mitigation ability as a function of the coalition structure. Given the throughput model, we formulate a coalitional game where the involved base stations are the rational players. Allowing for individual deviations by the players, we formulate a distributed coalition formation algorithm with low complexity and low communication overhead that leads to an individually stable coalition structure. The dynamic clustering is performed using only long-term CSI, but we also provide a robust short-term precoding algorithm which accounts for the intercoalition interference when spectrum sharing is applied between coalitions. Numerical simulations show that the distributed coalition formation is generally able to reach long-term sum throughputs within 10 % of the global optimum.
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| 2. |
- Brandt, Rasmus, 1985-, et al.
(author)
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Globally Optimal Base Station Clustering in Interference Alignment-Based Multicell Networks
- 2016
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In: IEEE Signal Processing Letters. - : IEEE. - 1070-9908 .- 1558-2361. ; 23:4, s. 512-516
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Journal article (peer-reviewed)abstract
- Coordinated precoding based on interference alignment is a promising technique for improving the throughputs in future wireless multicell networks. In small networks, all base stations can typically jointly coordinate their precoding. In large networks however, base station clustering is necessary due to the otherwise overwhelmingly high channel state information (CSI) acquisition overhead. In this work, we provide a branch and bound algorithm for finding the globally optimal base station clustering. The algorithm is mainly intended for benchmarking existing suboptimal clustering schemes. We propose a general model for the user throughputs, which only depends on the long-term CSI statistics. The model assumes intracluster interference alignment and is able to account for the CSI acquisition overhead. By enumerating a search tree using a best-first search and pruning sub-trees in which the optimal solution provably cannot be, the proposed method converges to the optimal solution. The pruning is done using specifically derived bounds, which exploit some assumed structure in the throughput model. It is empirically shown that the proposed method has an average complexity which is orders of magnitude lower than that of exhaustive search.
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| 3. |
- Brandt, Rasmus, 1985-, et al.
(author)
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Interference Alignment-Aided Base Station Clustering using Coalition Formation
- 2015
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In: Proceedings of the 49th Asilomar Conference on Signals, Systems and Computers. - Pacific Grove, CA, USA : IEEE conference proceedings.
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Conference paper (peer-reviewed)abstract
- Base station clustering is necessary in large interference networks, where the channel state information (CSI) acquisition overhead otherwise would be overwhelming. In this paper, we propose a novel long-term throughput model for the clustered users which addresses the balance between interference mitigation capability and CSI acquisition overhead. The model only depends on statistical CSI, thus enabling long-term clustering. Based on notions from coalitional game theory, we propose a low-complexity distributed clustering method. The algorithm converges in a couple of iterations, and only requires limited communication between base stations. Numerical simulations show the viability of the proposed approach.
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| 4. |
- Chong, Z., et al.
(author)
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Pricing in Noncooperative Interference Channels for Improved Energy Efficiency
- 2010
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In: EURASIP Journal on Wireless Communications and Networking. - : Springer. - 1687-1472 .- 1687-1499. ; 2010
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Journal article (peer-reviewed)abstract
- We consider noncooperative energy-efficient resource allocation in the interference channel. Energy efficiency is achieved when each system pays a price proportional to its allocated transmit power. In noncooperative game-theoretic notation, the power allocation chosen by the systems corresponds to the Nash equilibrium. We study the existence and characterize the uniqueness of this equilibrium. Afterwards, pricing to achieve energy-efficiency is examined. We introduce an arbitrator who determines the prices that satisfy minimum QoS requirements and minimize total power consumption. This energy-efficient assignment problem is formulated and solved. We compare our setting to that without pricing with regard to energy-efficiency by simulation. It is observed that pricing in this distributed setting achieves higher energy-efficiency indifferent interference regimes.
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| 5. |
- Dargie, W., et al.
(author)
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A topology control protocol based on eligibility and efficiency metrics
- 2011
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In: Journal of Systems and Software. - : Elsevier. - 0164-1212. ; 84:1, s. 2-11
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Journal article (peer-reviewed)abstract
- The question of fairness in wireless sensor networks is not studied very well. It is not unusual to observe in the literature fairness traded for low latency or reliability. However, a disproportional use of some critical nodes as relaying nodes can cause premature network fragmentation. This paper investigates fairness in multi-hop wireless sensor networks and proposes a topology control protocol that enables nodes to exhaust their energy fairly. Moreover, it demonstrates that whereas the number of neighboring nodes with which a node should cooperate depends on the density of the network, increasing this number beyond a certain amount does not contribute to network connectivity.
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| 6. |
- Dargie, W., et al.
(author)
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A Topology Control Protocol for 2D Poisson Distributed Wireless Sensor Networks
- 2009
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Conference paper (peer-reviewed)abstract
- Topology control in a wireless sensor network is useful for ensuring that the network remains connected in the presence of nodes that exhaust their energy or become altogether dysfunctional (for whatever reasons). It also ensures that all the link that can be established are energy-efficient links and the nodes utilize their energy fairly. In this paper, we propose a fair and energy efficient topology control protocol for a two-dimensional random sensor deployment in which the nodes can estimate the distances to their neighbors and vary their transmission power accordingly. The protocol applies a neighbor eligibility metric in order to ensure a fair distribution of energy in the network. We introduce the notion of weighted relaying regions defined over the plane of a searching node to drop out inefficient links. Unlike most topology control protocols that rely on nearest neighbor approaches, we use a distance measure that is radio characteristic and channel condition dependent. We verify the performance of the protocol through simulation results on network graph properties and energy consumption.
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| 7. |
- Ghauch, Hadi, et al.
(author)
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Distributed precoding and user selection in MIMO interfering networks
- 2015
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In: 2015 IEEE 6th International Workshop on Computational Advances in Multi-Sensor Adaptive Processing, CAMSAP 2015. - : IEEE conference proceedings. - 9781479919635 ; , s. 461-464
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Conference paper (peer-reviewed)abstract
- In this work we shed light on the problem of precoding and user selection in MIMO networks. We formulate the problem using the framework of stable matching, whereby a set of users wish to be matched to a set of serving base stations, such as to maximize the sum-rate performance of the system. Though the problem is NP-hard, we propose a suboptimal heuristic that tackles the problem in a distributed fashion: we apply a many-to-one stable matching algorithm to generate a sequence of matchings, and the Weighted MMSE algorithm to perform the precoding. We benchmark our algorithm againt the recently proposed Weighted MMSE with User Assignment algorithm [1].
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| 8. |
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| 9. |
- Ho, K. M. Z., et al.
(author)
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Beamforming on the MISO interference channel with multi-user decoding capability
- 2010
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Conference paper (peer-reviewed)abstract
- This paper considers the multiple-input-single-output interference channel (MISO-IC) in which transmitters and receivers share the same time and frequency resources. We consider receivers with interference decoding capability (IDC) so that the interference signal can be decoded and subtracted from the received signal. On the MISO-IC with single user decoding, transmit beamforming vectors are designed to mitigate interference at the receivers. With IDC, receivers can potentially decode interference which yields a higher data rate. Yet, decoding interference pose a rate constraint on the interferer and in turn on the sum rate of the system. This brings some interesting questions: when should the Txs mitigate interference and when should Txs amplify interference? Under what situations should Txs change from mitigating interference to amplifying interference? We answer these questions in this paper.
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| 10. |
- Holfeld, B., et al.
(author)
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Stable Matching for Adaptive Cross-Layer Scheduling in LTE Downlink
- 2013
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In: 2013 IEEE 77TH VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING). - : IEEE conference proceedings. - 9781467363372
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Conference paper (peer-reviewed)abstract
- Resource allocation from base stations to mobile users in realistic MIMO-OFDMA systems such as the 3GPP Long Term Evolution (LTE) downlink is based on limited and quantized channel feedback over a fine-granular resource grid of multiple dimensions. This allows for opportunistic scheduling but impedes application of enhanced cross-layer strategies due to the discrete and combinatorial problem space. Integer optimization for this allocation problem is strongly complex and prohibits use of efficient algorithms. Provided solutions in practice are given by sub-optimal greedy heuristics. In this paper, we apply two-sided stable matchings for adaptive multi-user scheduling. Our framework gives Pareto-efficient allocations and yields a tunable tradeoff between system throughput and user fairness. We form stable pairings of system resources and users based on queue-and channel-aware lists of preferred matches. The derived concept aims to find a stable matching state under presence of non-strict preference relations if such exist or redefines the allocation problem to a solvable strict problem instance. A performance evaluation for scheduling is done by system level simulations for high traffic loads in a realistically modeled LTE deployment.
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