Kumin Cho

Mobile caching policies for device-to-device (D2D) content delivery networking

We consider a mobile content delivery network (mCDN) in which a special form of mobile devices designated as caching servers (caching-server device: CSD) can provide the near-by devices with some popular contents on demand via device-to-device (D2D) communication links. On the assumption that mobile CSDs are randomly distributed by a Poisson point process (PPP), an optimization problem is formulated to determine the probability of storing the individual content in each server in a manner that minimizes the average caching failure rate. Further, we present a low-complexity search algorithm, optimum dual-solution searching algorithm (ODSA), for solving this optimization problem. We identify the important characteristics of the optimal caching policies in the mobile environment that would serve as a useful aid in designing an mCDN.

Transmission rate control of ASO-TDMA in multi-hop maritime communication network

We consider a ship ad-hoc network (SANET) that extends the service coverage for data communication with the multi-hop connectivity among the ships. In this paper, we propose two means of transmission rate control to maximize the system throughput subject to the reservation-based random access that is is inherent to the ad-hoc self-organizing TDMA (ASO-TDMA) protocol in SANET. It has been demonstrated that the proposed control schemes can maintain the maximum system throughput adaptively as the number of ships varies for the different hop ranges and their target attempt rates.

Joint scheduling with inter-cell cooperation for carrier aggregation in LTE-advanced system

By investigating the technical issues in the existing cell selection and scheduling scheme under some of carrier aggregation (CA) deployment scenarios discussed in LTE-Advanced system, we propose a distributed inter-cell cooperation scheme for joint scheduling that can improve the average system throughput when 6 different sectors are formed by deploying the sector antennas for each component carrier (CC) in the different direction. It has been shown by our system-level simulation that the proposed scheme roughly doubles the per-user average throughput for the cell-edge users, i.e., ones with the lowest 5% performance when the offered load is not too large.

The least-cost network selection scheme for delay-constrained transmission in the multi-band maritime communication system

As various types of wireless systems are characterized by its own individual reliability and transmission cost in the multi-band maritime communication network, a means of selecting a least-cost system is required for transmitting the shipment information within a pre-specified time constraint. In this paper, a simple decision criterion for a least-cost network selection has been derived with a stochastic Markov decision process, so as to warrant the delay-constrained transmission in a distributed manner. Our simulation results show that the proposed approach can reduce the transmission cost dramatically under the varying channel conditions of the different networks.

The Minimum-cost Network Selection Scheme to Guarantee the Periodic Transmission Opportunity in the Multi-band Maritime Communication System

This paper presents the minimum-cost network selection scheme which determines the transmission instance in the multi-band maritime communication system, so that the shipment-related real-time information can be transmitted within the maximum allowed period. The transmission instances and the corresponding network selection process are modeled by a Markov Decision Process (MDP), for the channel model in the 2-state Markov chain, which can be solved by stochastic dynamic programming. It derives the minimum-cost network selection rule, which can reduce the network cost significantly as compared with the straight-forward scheme with a periodic transmission.