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Seong-Lyun Kim

Publications and source records attributed to Seong-Lyun Kim.

88 records · Page 5Linked to original sources
arXiv2015

Resource Management and Cell Planning in Millimeter-Wave Overlaid Ultra-Dense Cellular Networks

This paper proposes a cellular network exploiting millimeter-wave (mmWave) and ultra-densified base stations (BSs) to achieve the far-reaching 5G aim in downlink average rate. The mmWave overlaid network however incurs a pitfall that its ample data rate is only applicable for downlink transmissions due to the implementation difficulty at mobile users, leading to an immense difference between uplink and downlink rates. We therefore turn our attention not only to maximize downlink rate but also to ensure the minimum uplink rate. With this end, we firstly derive the mmWave overlaid ultra-dense cellular network spectral efficiencies for both uplink and downlink cases in closed forms by using stochastic geometry via a lower bound approximation. In a practical scenario, such tractable results of the proposed network reveal that incumbent micro-wave ($μ$Wave) cellular resource should be mostly dedicated to uplink transmissions in order to correspond with the mmWave downlink rate improvement. Furthermore, increasing uplink rate via $μ$Wave BS densification cannot solely cope with the mmWave downlink/uplink rate asymmetry, and thus requires additional $μ$Wave spectrum in 5G cellular networks.

cs.NI↗
arXiv2015

Robotic Wireless Networks in a Narrow Alley: A Game Theoretic Approach

There are many situations where vehicles may compete with each other to maximize their respective utilities.We consider a narrow alley where two groups, eastbound and westbound, of autonomous vehicles are heading toward each of their destination to minimize their travel distance. However, if the two groups approach the road simultaneously, it will be blocked. The main goal of this paper is to investigate how wireless communications among the vehicles can lead the solution near to Pareto optimum. In addition, we implemented such a vehicular test-bed, composed of networked robots that have an infrared sensor, a DC motor, and a wireless communication module: ZigBee (IEEE 802.15.4).

cs.RO↗
arXiv2014

Asymptotic Behavior of Ultra-Dense Cellular Networks and Its Economic Impact

This paper investigates the relationship between base station (BS) density and average spectral efficiency (SE) in the downlink of a cellular network. This relationship has been well known for sparse deployment, i.e. when the number of BSs is small compared to the number of users. In this case the SE is independent of BS density. As BS density grows, on the other hand, it has previously been shown that increasing the BS density increases the SE, but no tractable form for the SE-BS density relationship has yet been derived. In this paper we derive such a closed-form result that reveals the SE is asymptotically a logarithmic function of BS density as the density grows. Further, we study the impact of this result on the network operator's profit when user demand varies, and derive the profit maximizing BS density and the optimal amount of spectrum to be utilized in closed forms. In addition, we provide deployment planning guidelines that will aid the operator in his decision if he should invest in densifying his network or in acquiring more spectrum.

cs.IT↗
arXiv2014

Optimization of Spectrum Allocation and Subsidization in Mobile Communication Services

Mobile traffic explosion causes spectrum shortage and polarization of data usage among users, which will eventually decrease user welfare in mobile communication services. Governments around the world are planning to make more spectrum available for mobile broadband use, and the key policy issue is to find an efficient spectrum allocation method that will improve user welfare. In this paper, we propose a data subsidy scheme where the regulator offers a spectrum price discount to mobile network operators (MNOs) in return for imposing the responsibility of providing a predefined data amount to users free of charge. To analyze the subsidy effect, we adopt the two-stage approach of Cournot and Bertrand competition, and find a Nash equilibrium of the competition. An interesting observation is that the increase in user welfare does not involve MNO profit loss and the increasing amount is higher than the regulator's expenses for implementing the data subsidy scheme. The most of the paper is for the duopoly competition, which is extended to the general case, finally.

cs.GT↗
arXiv2014

Spreading Information in Mobile Wireless Networks

Device-to-device (D2D) communication enables us to spread information in the local area without infrastructure support. In this paper, we focus on information spreading in mobile wireless networks where all nodes move around. The source nodes deliver a given information packet to mobile users using D2D communication as an underlay to the cellular uplink. By stochastic geometry, we derive the average number of nodes that have successfully received a given information packet as a function of the transmission power and the number of transmissions. Based on these results, we formulate a redundancy minimization problem under the maximum transmission power and delay constraints. By solving the problem, we provide an optimal rule for the transmission power of the source node.

cs.NI↗
arXiv2014

Asymmetric-valued Spectrum Auction and Competition in Wireless Broadband Services

We study bidding and pricing competition between two spiteful mobile network operators (MNOs) with considering their existing spectrum holdings. Given asymmetric-valued spectrum blocks are auctioned off to them via a first-price sealed-bid auction, we investigate the interactions between two spiteful MNOs and users as a three-stage dynamic game and characterize the dynamic game's equilibria. We show an asymmetric pricing structure and different market share between two spiteful MNOs. Perhaps counter-intuitively, our results show that the MNO who acquires the less-valued spectrum block always lowers his service price despite providing double-speed LTE service to users. We also show that the MNO who acquires the high-valued spectrum block, despite charing a higher price, still achieves more market share than the other MNO. We further show that the competition between two MNOs leads to some loss of their revenues. By investigating a cross-over point at which the MNOs' profits are switched, it serves as the benchmark of practical auction designs.

cs.NI↗
arXiv2014

Content-Specific Broadcast Cellular Networks based on User Demand Prediction: A Revenue Perspective

The Long Term Evolution (LTE) broadcast is a promising solution to cope with exponentially increasing user traffic by broadcasting common user requests over the same frequency channels. In this paper, we propose a novel network framework provisioning broadcast and unicast services simultaneously. For each serving file to users, a cellular base station determines either to broadcast or unicast the file based on user demand prediction examining the file's content specific characteristics such as: file size, delay tolerance, price sensitivity. In a network operator's revenue maximization perspective while not inflicting any user payoff degradation, we jointly optimize resource allocation, pricing, and file scheduling. In accordance with the state of the art LTE specifications, the proposed network demonstrates up to 32% increase in revenue for a single cell and more than a 7-fold increase for a 7 cell coordinated LTE broadcast network, compared to the conventional unicast cellular networks.

cs.NI↗
arXiv2013

Random Basketball Routing for ZigBee based Sensor Networks

Random basketball routing (BR) \cite {Hwang} is a simple protocol that integrates MAC and multihop routing in a cross-layer optimized manner. Due to its lightness and performance, BR would be quite suitable for sensor networks, where communication nodes are usually simple devices. In this paper, we describe how we implemented BR in a ZigBee-based (IEEE 802.15.4) sensor network. In \cite{Hwang}, it is verified that BR takes advantages of dynamic environments (in particular, node mobility), however, here we focus on how BR works under static situations. For implementation purposes, we add some features such as destination RSSI measuring and loop-free procedure, to the original BR. With implemented testbed, we compare the performance of BR with that of the simplified AODV with CSMA/CA. The result is that BR has merits in terms of number of hops to traverse the network. Considering the simple structure of BR and its possible energy-efficiency, we can conclude that BR can be a good candidate for sensor networks both under dynamic- and static environments.

cs.NI↗
arXiv2013

Network Coded Rate Scheduling for Two-way Relay Networks

We investigate a scheduling scheme incorporating network coding and channel varying information for the two-way relay networks. Our scheduler aims at minimizing the time span needed to send all the data of each source of the network. We consider three channel models, time invariant channels, time varying channels with finite states and time varying Rayleigh fading channels. We formulate the problem into a manageable optimization problem, and get a closed form scheduler under time invariant channels and time varying channel with finite channel states. For Rayleigh fading channels, we focus on the relay node operation and propose heuristic power allocation algorithm resemblant to water filling algorithm. By simulations, we find that even if the channel fluctuates randomly, the average time span is minimized when the relay node transmits/schedules network coded data as much as possible.

cs.IT↗
arXiv2013

An Introduction to Socially Connected Machines: Characteristics and Applications

Due to the development of information and communication technologies, it is difficult to handle the billions of connected machines. In this paper, to cope with the problem, we introduce machine social networks, where they freely follow each other and share common interests with their neighbors. We classify characteristics and describe required functionalities of socially connected machines. We also illustrate two examples; a twit-bot and maze scenario.

cs.SI↗
arXiv2013

Game-theoretic Understanding of Price Dynamics in Mobile Communication Services

In the mobile communication services, users wish to subscribe to high quality service with a low price level, which leads to competition between mobile network operators (MNOs). The MNOs compete with each other by service prices after deciding the extent of investment to improve quality of service (QoS). Unfortunately, the theoretic backgrounds of price dynamics are not known to us, and as a result, effective network planning and regulative actions are hard to make in the competitive market. To explain this competition more detail, we formulate and solve an optimization problem applying the two-stage Cournot and Bertrand competition model. Consequently, we derive a price dynamics that the MNOs increase and decrease their service prices periodically, which completely explains the subsidy dynamics in the real world. Moving forward, to avoid this instability and inefficiency, we suggest a simple regulation rule which leads to a Pareto-optimal equilibrium point. Moreover, we suggest regulator's optimal actions corresponding to user welfare and the regulator's revenue.

cs.GT↗
arXiv2013

Worst-case User Analysis in Poisson Voronoi Cells

In this letter, we focus on the performance of a worst-case mobile user (MU) in the downlink cellular network. We derive the coverage probability and the spectral efficiency of the worst-case MU using stochastic geometry. Through analytical and numerical results, we draw out interesting insights that the coverage probability and the spectral efficiency of the worst-case MU decrease down to 23% and 19% of those of a typical MU, respectively. By applying a coordinated scheduling (CS) scheme, we also investigate how much the performance of the worst-case MU is improved.

cs.IT↗
arXiv2013

Downlink Capacity and Base Station Density in Cellular Networks

There have been a bulk of analytic results about the performance of cellular networks where base stations are regularly located on a hexagonal or square lattice. This regular model cannot reflect the reality, and tends to overestimate the network performance. Moreover, tractable analysis can be performed only for a fixed location user (e.g., cell center or edge user). In this paper, we use the stochastic geometry approach, where base stations can be modeled as a homogeneous Poisson point process. We also consider the user density, and derive the user outage probability that an arbitrary user is under outage owing to low signal-to-interference-plus-noise ratio or high congestion by multiple users. Using the result, we calculate the density of success transmissions in the downlink cellular network. An interesting observation is that the success transmission density increases with the base station density, but the increasing rate diminishes. This means that the number of base stations installed should be more than $n$-times to increase the network capacity by a factor of $n$. Our results will provide a framework for performance analysis of the wireless infrastructure with a high density of access points, which will significantly reduce the burden of network-level simulations.

cs.NI↗
arXiv2013

Cost-Effective Broadcast in Cellular Networks

In recent years, video-related services such as YouTube and Netflix have generated huge amounts of traffic and the network neutrality debate has emerged as a major issue. In this paper, we consider feasibility of using a hybrid of unicast and broadcast in cellular networks for high-traffic services (e.g., video streaming), from the perspective of cost effectiveness. To reflect spatial characteristics of base stations (BSs) and mobile users (MUs), we use the stochastic geometry approach where BSs and MUs are modeled as independent homogeneous Poisson point processes (PPPs). With these assumptions and results, we show how to cope with the trade-off between broadcast and unicast for providing the service with affordable cost levels and reduced network load. Moreover, we propose the so called periodic broadcasting service, where popular video contents are periodically broadcast over cellular networks. This service will make a positive impact on the network neutrality debate by stimulating cooperation between mobile network operators (MNOs) and content providers (CPs).

cs.NI↗
arXiv2011

Mobility Control for Machine-to-Machine LTE Systems

In this paper, we propose an efficient mobility control algorithm for the downlink multi-cell orthogonal frequency division multiplexing access (OFDMA) system for co-channel interference reduction. It divides each cell into several areas. The mobile nodes in each area find their own optimal position according to their present location. Both the signal to interference plus noise ratio (SINR) and the capacity for each node are increased by the proposed mobility control algorithm. Simulation results say that, even the frequency reuse factor (FRF) is equal to 1, the average capacity is improved after applying the mobility control algorithm, compared to existing partial frequency reuse (PFR) scheme.

cs.NI↗