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  • 301.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Hossein, Shokri-Ghadikolaei
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Fischione, Carlo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Nätverk och systemteknik.
    Petrova, Marina
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Ki Won, Sung
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Fast and Reliable Initial Access with Random Beamforming for mmWave NetworksManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Millimeter-wave (mmWave) communications rely on directional transmissions to overcome severe path loss. Nevertheless, the use of narrow beams complicates the initial access procedure and increase the latency as the transmitter and receiver beams should be aligned for a proper link establishment. In this paper, we investigate the feasibility of random beamforming for the cell-search phase of initial access. We develop a stochastic geometry framework to analyze the performance in terms of detection failure probability and expected latency of initial access as well as total data transmission. Meanwhile, we compare our scheme with the widely used exhaustive search and iterative search schemes, in both control plane and data plane. Numerical results show that, compared to the other two schemes, random beamforming can substantially reduce the latency of initial access with comparable failure probability in dense networks. We show that the gain of the random beamforming is more prominent in light traffics and low-latency services. Our work demonstrates that developing complex cell-discovery algorithms may be unnecessary in dense mmWave networks and thus shed new lights on mmWave network design.

  • 302.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Park, J.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    On the asymptotic behavior of ultra-densification under a bounded dual-slope path loss model2017Ingår i: European Wireless 2017 - 23rd European Wireless Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 8011320Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the impact of network densification on the performance in terms of downlink signal-to-interference (SIR) coverage probability and network area spectral efficiency (ASE). A sophisticated bounded dual-slope path loss model and practical user equipment (UE) densities are incorporated in the analysis, which have never been jointly considered before. By using stochastic geometry, we derive an integral expression along with closed-form bounds of the coverage probability and ASE, validated by simulation results. Through these, we provide the asymptotic behavior of ultra-densification. The coverage probability and ASE have non-zero convergence in asymptotic regions unless UE density goes to infinity (full load). Meanwhile, the effect of UE density on the coverage probability is analyzed. The coverage probability will reveal an U-shape for large UE densities due to interference fall into the near-field, but it will keep increasing for low UE densites. Furthermore, our results indicate that the performance is overestimated without applying the bounded dual-slope path loss model. The derived expressions and results in this work pave the way for future network provisioning.

  • 303.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Park, Jihong
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    On the Asymptotic Behavior of Ultra-Densificationunder a Bounded Dual-Slope Path Loss ModelManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we investigate the impact of networkdensification on the performance in terms of downlink signal-tointerference(SIR) coverage probability and network area spectralefficiency (ASE). A sophisticated bounded dual-slope path lossmodel and practical UE densities are incorporated in the analysis.By using stochastic geometry, we derive an integral expressionalong with closed-form bounds of the coverage probability andASE, validated by simulation results. Through these, we providethe asymptotic behavior of ultra-densification. The coverageprobability and ASE have non-zero convergence in asymptoticregions unless UE density goes to infinity (full load). Meanwhile,the effect of UE density on the coverage probability is analyzed.The coverage probability will suffer from decreasing with largeUE densities due to interference fall into the near-field, but it willkeep increasing with lower UE densites. Furthermore, we showthe performance is overestimated without applying the boundeddual-slope path loss model. Our study can give insights on efficientnetwork provisioning in the future.

  • 304.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Shi, Lei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Zander, Jens
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    On the Capacity of Wi-Fi System in TV White Space with Aggregate Interference Constraint2013Ingår i: Proceedings of the 2013 8th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCOM 2013, IEEE conference proceedings, 2013, s. 123-128Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a quantitative assessmentof the performance of a Wi-Fi like system in TV white space andcompare it with the traditional Wi-Fi system in the ISM band.Particular emphasis is given to the constraint on the aggregatesecondary interference on TV reception, which is regarded as thepremise of the link throughput analysis that followed. Numericalevaluation is performed over different scenarios where the TVreceive signal strength, number of unoccupied TV channels, userdensity are varied. Our results show that the primary interferenceconstraint has only significant impact on the secondary systemperformance in rural scenario with low TV receive signalstrength. In other cases, where higher transmit power does notguarantee better performance, the capacity of the system islimited by the secondary self-interference or collisions rather thanthe interference constraint. Therefore, efficient TV White Spaceutilization can be achieved by properly setting the secondarytransmit power adaptive to different environments.

  • 305.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Technical rate of substitution of spectrum in future mobile broadband provisioning2015Ingår i: 2015 IEEE International Symposium on Dynamic Spectrum Access Networks, DySPAN 2015, IEEE conference proceedings, 2015, s. 297-300Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dense deployment of base stations (BSs) and multi-antenna techniques are considered as key enablers for future mobile networks. Meanwhile, spectrum sharing techniques and utilization of higher frequency bands make more bandwidth available. An important question for future system design is which element is more effective than others. In this paper, we introduce the concept of technical rate of substitution (TRS) from microeconomics and study the TRS of spectrum in terms of BS density and antenna number per BS. Numerical results show that TRS becomes higher with increasing user data rate requirement, suggesting that spectrum is the most effective means of provisioning extremely fast mobile broadband.

  • 306.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Tradeoff between spectrum and densification for achieving target user throughput2015Ingår i: IEEE Vehicular Technology Conference, IEEE , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dense deployment which brings small base stations (BS) closer to mobile devices is considered as a promising solution to the booming traffic demand. Meanwhile, the utilization of new frequency bands and spectrum aggregation techniques provide more options for spectrum choice.Whether to increase BS density or to acquire more spectrum is a key strategic question for mobile operators. In this paper, we investigate the relationship between BS density and spectrum with regard to individual user throughput target. Our work takes into account load-dependent interference model and various traffic demands. Numerical results show that densification is more effective in sparse networks than in already dense networks. In sparse networks, doubling BS density results in almost twofold throughput increase. However, in dense networks where BSs outnumber users, more than 10 times of BS density is needed to double user throughput. Meanwhile, spectrum has a linear relationship with user throughput for a given BS density. The impact of traffic types is also discussed. Even with the same area throughput requirement, different combination of user density and individual traffic amount leads to different needs for BS density and spectrum.

  • 307.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Park, J.
    Kim, S. -L
    Kim, K. S.
    Cooperative transmissions in ultra-dense networks under a bounded dual-slope path loss model2017Ingår i: 2017 European Conference on Networks and Communications (EuCNC), Institute of Electrical and Electronics Engineers (IEEE), 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In an ultra-dense network (UDN) where there are more base stations (BSs) than active users, it is possible that many BSs are instantaneously left idle. Thus, how to utilize these dormant BSs by means of cooperative transmission is an interesting question. In this paper, we investigate the performance of a UDN with two types of cooperation schemes: Non-coherent joint transmission (JT) without channel state information (CSI) and coherent JT with full CSI knowledge. We consider a bounded dual-slope path loss model to describe UDN environments where a user has several BSs in the near-field and the rest in the far-field. Numerical results show that non-coherent JT cannot improve the user spectral efficiency (SE) due to the simultaneous increment in signal and interference powers. For coherent JT, the achievable SE gain depends on the range of near-field, the relative densities of BSs and users, and the CSI accuracy. Finally, we assess the energy efficiency (EE) of cooperation in UDN. Despite costing extra energy consumption, cooperation can still improve EE under certain conditions.

  • 308.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Park, Jihong
    Kim, Seong-Lyun
    Kim, Kwang Soon
    Cooperative Transmissions in Ultra-Dense Networks under a Bounded Dual-Slope Path Loss ModelManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    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.

  • 309.
    Yang, Yanpeng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Hybrid Fiber and Microwave Protection for Mobile Backhauling2014Ingår i: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 6, nr 10, s. 869-878Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several studies have shown that optical-fiber-based backhauling offers a future proof solution to handle rapidly increasing traffic in wireless access networks and outperforms other existing backhauling technologies, such as microwave and copper, in terms of capacity, scalability, and sustainability. However, the deployment cost of fiber infrastructure is relatively high and it may be difficult to provide a cost efficient and flexible protection strategy for a fiber backhauling network. Considering that protection is very important to avoid service interruption in a high-capacity mobile backhauling network, in this paper we propose a hybrid fiber and microwave protection scheme for mobile backhauling based on a passive optical network (PON). The proposed reliable architecture is compatible with any wavelength division multiplexing (WDM)based PON, e. g., pure WDM PON and a hybrid time and wavelength division multiplexing (TWDM) PON, offering high flexibility and relatively low deployment cost. The backup for the feeder fiber is provided by dual homing, while the protection of the distribution section can be established via a microwave connection between two base stations in case high reliability performance is required, e. g., for macrocells covering large service areas. We have carried out an extensive assessment of our approach in terms of connection availability, failure impact, complexity, and flexibility in providing resiliency. We also show a comparison with other existing solutions. The evaluation results confirm that our scheme can achieve relatively high flexibility and reliability performance while maintaining low complexity compared with the existing approaches.

  • 310.
    Zander, Jens
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    "4G" and the wireless world 2015 - Challenges in system architectures and communication paradigms2006Ingår i: Radio Des. Nanometer Technol., 2006, s. 3-10Konferensbidrag (Refereegranskat)
  • 311.
    Zander, Jens
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Rasmussen, Lars K.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Maehoenen, Petri
    Petrova, Marina
    Jantti, Riku
    Kronander, Jonas
    On the scalability of cognitive radio:: Assessing the commercial viability of secondary spectrum access2013Ingår i: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 20, nr 2, s. 28-35Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report results from the recently finished QUASAR project, which has studied overall system aspects of cognitive radio technologies and has paid attention particularly to the economic viability of different use cases. We find that successful secondary sharing goes far beyond the detection of spectrum holes. Large-scale commercial success requires that secondary systems are scalable so that a large number of users can be served in an economically viable fashion. Our key finding is that secondary spectrum use is not an attractive method for most of the commercially interesting scenarios, from neither a business nor technical perspective. Perhaps somewhat surprisingly, the likely commercial "sweet spot" for secondary sharing in the lower frequency bands is short-range indoor communications. We also find that regulation does not currently present a significant barrier in Europe or the United States.

  • 312.
    Zhang, P.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Costa, J.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Tekeusso, Boris
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Wahlstrand, N.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Carmona, O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    M2M Communications in LTE SystemsIngår i: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    In wide-area applications, low-cost and massive machine to machine (M2M) communications provided bycellular networks will be one main driver for the success of future Internet of Things (IoT) development. The first directconsequence of the proliferation of IoT is that large numbers of devices will produce huge quantities of sporadic data andsignificantly higher capacity of cellular networks will be needed - not in terms of megabits transported, but the numberof machines sustained. In this paper, we will investigate the support of M2M communications in LTE systems. The goalof this paper is to survey how the existing LTE architecture supports M2M traffic in terms of capacity, coverage, andsignaling, assuming a certain usage scenario and traffic pattern. Solutions are suggested for issues that arise whena large amount of M2M traffic is transported over an LTE network. We will show that the capacity and coverage arenot the key issues; instead the signaling is the main bottleneck, especially the ones related to the RACH. Finally, as atypical illustrating example, we will study in detail how Smart Metering application can be supported in LTE systems andinvestigate thoroughly solutions to the key bottlenecks in this paper.

  • 313.
    Zhang, Peng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Miao, Guowang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Energy-Efficient Clustering Design for M2M Communications2014Ingår i: 2014 IEEE Global Conference on Signal and Information Processing (GlobalSIP), 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Machine-to-machine (M2M) communications in cellular networks enables Internet of Things in the macro geographical regions and is a promising technique in next-generation wireless networks. In this paper, we study energy-efficient clusteringdesign in cellular networks to maximize the overall network battery life time.

    We propose a new clustering design which finds the optimal number of clusters in a cellular network, and maximizes the network energy efficiency, meanwhile rulesof selecting and rotating cluster heads. Different from existing clustering designs, we consider both transmission and circuit energy consumption in this paper. The network performance will be both rigorously analyzed and evaluated using simulations withrespect to dead device ratio, residual energy, and network life. The simulation results show that by using the proposed clustering approach, the network battery life can be improved significantly.

  • 314.
    Zografos, Alexandros
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Wireless Sensor-based Agricultural Monitoring System2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Idag när energiresurser blir allt knappare och knappare blir de även mer värdefulla. I samband med befolkningstillväxten under förra århundradet har behovet av att hitta nya, mer effektiva och hållbara metoder inom jordbruket och livsmedelsproduktion blivit av allt större vikt. . För att underlätta denna process har vi designat, byggt och utvärderat ett system för precisionsjordbruk som ger bönder mer användbara data om jorden, vattenförsörjning och det allmänna tillståndet i sina områden på ett användarvänligt och lättillgängligt sätt. Vårt system syftar till att göra odling och bevattning effektivare då bonden kan fatta bättre underbyggda beslut och därmed spara tid och resurser.

    Mångfalden av läget och jordbrukets klimatpåverkan, tillsammans med andra miljöparametrar över tiden gör bondens beslutsprocess mer komplicerad än tidigare och kräver ytterligare empirisk kunskap. Att tillämpa trådlösa sensornätverk för övervakning av dessa parametrar och att presentera? denna information med en användarvänlig skräddarsydd webbtjänst kan göra det möjligt för jordbrukare att utnyttja på ett effektivt sätt nåde bästa resultaten från sitt jordbruk. Systemet kan skala utifrån varje bondes krav och den insamlade data kan utgöra en värdefull resurs för ett framtida jordbruk, utöver dess användning för dagens bondes beslut. Utformningen av systemet för precisionsjordbruk innehåller en prototyplösning avseende sensorplattformen och en anpassningsbar tjänst som kan användas på olika sätt och av flera enheter.

  • 315.
    Östermark, Filip
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Performance Optimization of Virtualized Packet Processing Function for 5G RAN2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Med den annalkande femte generationen av mobila nätverk (5G) följer en rad utmaningar för att uppnå de krav som ställs av kommande standarder. Den femte generationens Radioaccessnätverk (RAN) har flera funktioner som måste vara väloptimerade för att prestera enligt ökade krav. En sådan funktion är Packet Processing-funktionen (PPF), vilken måste kunna bearbeta paket med hög genomströmning och låg latens. En avgörande faktor i jakten på högre genomströmning och lägre latens är anpassningsbarhet hos 5Gteknologin.  Ericsson har därför utvecklat en prototyp av en PPF för 5G RAN som en virtuell nätverksfunktion (VNF) med hjälp av DPDK:s Eventdev-ramverk, som kan köras på en dator avsedd för allmän användning. I detta projekt optimeras genomströmningen och latensen hos Ericssons 5G RAN PPF-prototyp med hjälp av ett antal verktyg för prestandamätning och kodprofilering för att hitta flaskhalsar i pakethanteringsvägen, och därefter minska flaskhalsarnas negativa effekt på PPFens prestanda genom att ändra dess konfiguration.

    I experimenten användes IxNetwork för att generera 2 flöden med GTP-u/UDP/IPv4-paket som bearbetades av PPFen. IxNetwork användes även för att mäta genomströmning och latens.

    Resultaten visade att den maximala genomströmningen kunde ökas med 40.52% med en genomsnittlig latens på 97.59% jämfört med den ursprungliga PPF-prototypkonfigurationen i testfallet, genom att omfördela processorkärnor, sammanslå paketbearbetningssteg, och att patcha RSS-funktionen hos mottagardrivaren.

  • 316.
    Özyagci, Ali
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Zander, Jens
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Effect of propagation environment on area throughput of dense WLAN deployments2013Ingår i: 9th IEEE Broadband wireless access workshop (BWA 2013), IEEE Computer Society, 2013, s. 333-338Konferensbidrag (Refereegranskat)
    Abstract [en]

    Indoor wireless LAN deployments have become ubiquitous. As WLAN deployments become increasingly dense, WLANs start to cause more and more contention and interference to each other, to the point that they cause significant throughput degradation to other WLANs. Since WLANs are one of the most commonplace solutions to provide indoor broadband data access, it is crucial to assess the throughput limits of WLANs in order to understand at what demand level novel broadband access mechanisms will be critically needed. The amount of contention and interference that coexisting WLANs create on each other is influenced by the indoor propagation environment such as existence of walls or clutter. Although the indoor propagation environment has a significant impact on the interaction between WLANs, and consequently on the area throughput, the relationship between the indoor propagation environment and achievable area throughput has not received much attention. In this paper, we investigate the area throughput of densely deployed WLANs in different indoor propagation environments by conducting detailed MAC layer simulations using OPNET. The results show that the propagation conditions have a profound impact on achievable area throughput; as much as several tens of times increase in highly cluttered environments compared to open areas.

  • 317.
    Özyagci, Ali
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Zander, Jens
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Selfish multi-channel random access in heterogeneous channelsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We analyze the behavior of selfish users in a multichannel random access system in which the propagation characteristics of the available channels in the system exhibit different statistics. We formulate the behavior of the selfish users as a Bayesian game and identify the transmission strategies at the Nash equilibria. Following this, we propose a simple iterative algorithm to obtain the transmission probabilities of the selfish uses at the Nash equilibria and investigate the convergence properties of this algorithm. Using the transmission probabilities of the selfish users at the Nash equilibria, we analyze the performance of the MRA system with selfish users in terms of sum and per-user utilities and compare this system with its cooperative and scheduling system counterparts. We find that selfish behavior results in significant performance loss compared to scheduling and cooperative systems, which increases as the system load increases.

  • 318.
    Čelik, Haris
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab). KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth.
    Joint transmission with dummy symbols for dynamic TDD in ultra-dense deployments2017Ingår i: EuCNC 2017 - European Conference on Networks and Communications, IEEE, 2017, artikel-id 7980720Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dynamic time-division duplexing (TDD) is considered a promising solution to deal with fast-varying traffic often found in ultra-densely deployed networks. At the same time, it generates more interference which may degrade the performance of some user equipment (UE). When base station (BS) utilization is low, some BSs may not have an UE to serve. Rather than going into sleep mode, the idle BSs can help nearby UEs using joint transmission. To deal with BS-to-BS interference, we propose using joint transmission with dummy symbols where uplink BSs serving uplink UEs participate in the precoding. Since BSs are not aware of the uplink symbols beforehand, any symbols with zero power can be transmitted instead to null the BS-to-BS interference. Numerical results show significant performance gains for uplink and downlink at low and medium utilization. By varying the number of participating uplink BSs in the precoding, we also show that it is possible to successfully trade performance in the two directions.

  • 319.
    Čelik, Haris
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Sung, Ki Won
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Radio Systems Laboratory (RS Lab).
    Scalable Resource Allocation for Dynamic TDD with Traffic and Propagation Awareness2018Manuskript (preprint) (Övrigt vetenskapligt)
4567 301 - 319 av 319
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