| 1. |
- Kim, Jeemin, et al.
(author)
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Millimeter-Wave Interference Avoidance via Building-Aware Associations
- 2018
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In: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 6, s. 10618-10634
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Journal article (peer-reviewed)abstract
- Signal occlusion by building blockages is a double-edged sword for the performance of millimeter-wave (mmW) communication networks. Buildings may dominantly attenuate the useful signals, especially when mmW base stations (BSs) are sparsely deployed compared with the building density. In the opposite BS deployment, buildings can block the undesired interference. To enjoy only the benefit, we propose a building-aware association scheme that adjusts the directional BS association bias of the user equipments (UEs), based on a given building density and the concentration of UE locations around the buildings. The association of each BS can thereby be biased: 1) toward the UEs located against buildings for avoiding interference to other UEs or 2) toward the UEs providing their maximum reference signal received powers. The proposed association scheme is optimized to maximize the downlink average data rate derived by stochastic geometry. Its effectiveness is validated by simulation using real building statistics.
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| 2. |
- Kim, Seong-Lyun, et al.
(author)
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Wireless Communications in Networked Robotics
- 2009
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In: IEEE wireless communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1284 .- 1558-0687. ; 16:1, s. 4-5
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Journal article (peer-reviewed)
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| 3. |
- Yang, Yanpeng, 1987-, et al.
(author)
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Cooperative Transmissions in Ultra-Dense Networks under a Bounded Dual-Slope Path Loss Model
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Other publication (other academic/artistic)abstract
- In an Ultra-dense network (UDN) where there aremore base stations (BSs) than active users, it is possible thatmany BSs are instantaneously left idle. Thus, how to utilizethese dormant BSs by means of cooperative transmission is aninteresting question. In this paper, we investigate the performanceof a UDN with two types of cooperation schemes: non-coherentjoint transmission (JT) without channel state information (CSI)and coherent JT with full CSI knowledge. We consider a boundeddual-slope path loss model to describe UDN environments wherea user has several BSs in the near-field and the rest in thefar-field. Numerical results show that non-coherent JT cannotimprove the user spectral efficiency (SE) due to the simultaneousincrement in signal and interference powers. For coherent JT, theachievable SE gain depends on the range of near-field, the relativedensities of BSs and users, and the CSI accuracy. Finally, weassess the energy efficiency (EE) of cooperation in UDN. Despitecosting extra energy consumption, cooperation can still improveEE under certain conditions.
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| 4. |
- Berggren, Fredrik, et al.
(author)
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Energy-Effcient Control of Rate and Power in DS-CDMA Systems
- 2004
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In: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 3:3, s. 725-733
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Journal article (peer-reviewed)abstract
- The quality of service in DS-CDMA can be controlled by a suitable selection of processing gain and transmission powers. In this paper, distributed control of rate and power for best effort data services is considered. In particular, we elaborate on the problem of how to control the transmission rates for maximizing system throughput while simultaneously minimizing the transmission powers. We assume a practical scenario, where every user has a finite set of discrete transmission rates and propose a simple heuristic rate allocation scheme, greedy rate packing (GRP), applicable in both upand downlink. The scheme can be interpreted as a practical form of water-filling, in the sense that high transmission rates are allocated to users having high link gains and low interference. We show that under certain conditions, GRP will give maximum throughput and that it can be extended to guarantee a minimum data rate while maximizing network excess capacity. We suggest and analyze a distributed power control control algorithm to control the intercell interference when GRP is applied to a multicellular system. Numerical results show that the proposed transmission scheme can significantly decrease the power levels while maintaining high throughput.
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| 5. |
- Berggren, Fredrik, et al.
(author)
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Energy-Efficient Downlink Power Control and Scheduling for CDMA Non-Real Time Data
- 2000
-
Conference paper (peer-reviewed)abstract
- The performance of CDMA systems highly depends on the success in managing interference arising from both intercell and intra-cell transmissions. Interference management in terms of power control has been widely studied. In this paper we consider non-real time data services, where in addition to power control, there is the possibility of scheduling intra-cell transmissions. One such schedule is to use time division so that users transmit in a one-by-one fashion within each cell. We com- bine this form of scheduling with a suggested distributed power control algorithm for the inter-cell interference management. We show that the algorithm converges to a power allocation that supports the non-real time data users with the minimum power while meeting requirements on average data rate.
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| 6. |
- Cho, Jeong-woo, 1978-, et al.
(author)
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Capacity of Interference-Limited Ad Hoc Networks with Infrastructure Support
- 2006
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In: IEEE Communications Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1089-7798 .- 1558-2558. ; 10:1, s. 16-18
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Journal article (peer-reviewed)abstract
- In this letter, we consider the capacity of ad hoc networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Θ(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Θ(1) is still achievable when the number of access points grows linearly with respect to the number of nodes.
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| 7. |
- Cho, Jeong-woo, 1978-, et al.
(author)
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Infrastructure Support Increases the Capacity of Ad Hoc Wireless Networks
- 2005
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In: VTC2005-FALL: 2005 IEEE 62ND VEHICULAR TECHNOLOGY CONFERENCE, 1-4, PROCEEDINGS. - : IEEE Press. - 0780391527 ; , s. 2663-2668
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Conference paper (peer-reviewed)abstract
- In ad hoc wireless networks, one of the hottest research directions has been to increase the throughput capacity scaling with respect to the number of nodes n. Gupta and Kumar (2000) introduced a fixed random network model and showed that the throughput per source-destination pair is Theta(1/root nlogn) when the network is coordinated by a centralized entity. Grossglauser and Tse (2001) introduced a mobile random network model and showed that a source-destination pair acquires a constant throughput of Theta(1) assuming that delays incurred by mobile nodes with low mobility are tolerable.In this paper, we consider the capacity of ad hoc wireless networks with infrastructure support. Although Grossglauser-Tse mobile network model enables Theta(1) per-node throughput scaling, the mobility assumption may be too unrealistic to be accepted in some practical situations. One of the key observations we acquired is that the infrastructure support plays the same role played by the mobility in the Grossglauser-Tse model. We show that nodes can utilize the randomly located infrastructure support instead of mobility when nodes are nearly static. In this case, we show that the per-node throughput of Theta(1) is still achievable when the number of access points grows linearly with respect to the number of nodes. Furthermore., we show that there is additional per-node throughput improvement of Theta(1) when nodes are mobile.
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| 8. |
- Hwang, YoungJu, et al.
(author)
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On the throughput gain of device-to-device communications
- 2015
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In: ICT Express. - : Elsevier. - 2405-9595. ; 1:2, s. 67-70
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Journal article (peer-reviewed)abstract
- In an uplink underlaid device-to-device (D2D) cellular network, this paper considers its two aspects of throughput improvement. The two-fold gain comprises the throughput increase by offloading downlink cellular traffic to D2D communications, duplexing gain, and the increase by reusing uplink resources of D2D transmissions, capacity gain. Both impacts are investigated by exploiting stochastic geometry. On the basis of the analysis, a throughput optimal D2D operation guideline is provided for different network congestion environments.
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| 9. |
- Hwang, Youngju, et al.
(author)
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Scenario making for assessment of secondary spectrum access
- 2012
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 19:4, s. 25-31
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Journal article (peer-reviewed)abstract
- Secondary spectrum access, through which secondary users opportunistically access the underutilized radio spectrum, has emerged as a solution to cope with the perceived spectrum scarcity. The potential of secondary spectrum has therefore attracted industry players and regulators worldwide. To assess the real-life benefits of the secondary spectrum, it is crucial to estimate the amount of spectrum available for secondary use. This estimation requires a well defined set of models and parameters, which are collectively termed a scenario. In this article, we demonstrate the importance of scenario making in the quantitative assessment of secondary spectrum access. We first describe the elements that constitute a comprehensive secondary access scenario: a primary system and spectrum, a secondary system and usage, and the methods and context of spectrum sharing. Then we demonstrate how the assessment results of the spectrum availability differ depending on the scenario elements. We also illustrate the crucial aspects of a scenario in the business analysis, which, together with the technical assessment, is the input for the regulatory decision.
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| 10. |
- Jäntti, Riku, et al.
(author)
-
Second-Order Power Control with Asymptotically Fast Convergence
- 2000
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In: IEEE Journal on Selected Areas in Communications. - New York : IEEE. - 0733-8716 .- 1558-0008. ; 18:3, s. 447-457
-
Journal article (peer-reviewed)abstract
- This paper proposes a distributed power control algorithm that uses power levels of both current and previous iterations for power update. The algorithm is developed by applying the successive overrelaxation method to the power control problem. The gain from such a second-order algorithm is in faster convergence. Convergence analysis of the algorithm in case of feasible systems is provided in this paper. Using the distributed constrained power control (DCPC) as a reference algorithm, we carried out computational experiments on a DS-CDMA system. The results indicate that our algorithm significantly enhances the convergence speed of power control. A practical version of the proposed algorithm is provided and compared with the bang-bang type algorithm used in the IS-95 and the WCDMA systems. The results show that our algorithm also has a high potential for increasing the radio network capacity. Our analysis assumes that the system is feasible in the sense that we can support every active user by an optimal power control. When the system becomes infeasible because of high traffic load, it calls for other actions such as transmitter removal, which is beyond the scope of the present paper.
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