Jeounglak Ha

Dynamic load balancing architecture in heterogeneous wireless network environment

This paper discusses load balancing architecture among heterogeneous wireless networks (HWNs). Load balancing is an important issue for efficient use of radio resources not only in a single network but among different Radio Access Technologies (RATs) in HWNs. Cooperative management of radio resources among heterogeneous RATs is considered to reduce imbalance of utilization of radio resources and enhance availability of the system. For effective load balancing, we define a “community” concept, in which radio resources of various RATs are managed together. Radio resource management functional entities of RATs cooperatively work in the community. We present a load balancing architecture applied to 3GPP LTE, WiBro and WLAN and describe architectural considerations. We also present a straightforward load balancing algorithm that takes account of bandwidth usage and received signal to noise ratio. The load balancing algorithm of community radio resource management enhances utilization of radio resources and reduces call blocking probability of individual RATs in the community and further enhances average performance of the whole community.

Opportunistic Beamforming Communication With Throughput Analysis Using Asymptotic Approach

The opportunistic beamforming system (OBS) is currently receiving much attention in the field of downlink beamforming due to its simple random beamforming, low feedback complexity, and same throughput scaling obtained with perfect channel-state information using dirty paper coding at the transmitter. In this paper, we focus on its closed-form throughput evaluation over Rayleigh fading channels, based on the asymptotic theory of extreme order statistics. First, the throughput of a single-beam OBS is investigated, and an analytical solution tighter than the previously reported one is derived. Then, the asymptotic throughput bounds on a multibeam OBS are presented, and also, our analytical expression is shown to be very tight with the simulation results even with fewer users. After that, we argue that the reported conclusion that the single-beam OBS is much preferable to the multibeam OBS in the high-signal-to-noise-ratio (SNR) regime is inaccurate, but that, instead, it is satisfied only when the number of users is very small, due to its limited multiuser diversity gain. Finally, we show that four transmit beams is the most preferable in the multibeam OBS with a large number of users and moderate SNR, which arrives at the tradeoff between increasing spatial multiplexing gain and disappearing multiuser diversity gain.

Design and Implementation for Interactive Augmented Broadcasting System

In a typical augmented reality (AR), users can rotate, resize, or move AR objects, usually in application programs on handheld devices. In addition, users can instruct them to do an animation. Moreover, various types of application programs are provided and various ways of interactions are tried out for more natural user experience. On the other hand, in regular TV, an AR-applied TV program may be a composite video of original video and AR objects, which was already processed by the transmit side of broadcasting system and thus the TV viewer cannot influence the representation of TV program. Thus, until now, it can be said that an authentic AR service on TV broadcasting is not practically provided. In this paper, a new alternative paradigm of AR service in TV broadcasting is introduced. To provide an interactive AR experience to the viewer, first of all, we propose that the place where the original video and the augmented objects are composited needs to be moved from the transmit side to the TV terminal. Therefore, all augmented objects should be graphically rendered on the TV terminal. Considering the prerequisite, we propose an augmented broadcasting service system based on a hybrid framework that combines the conventional TV broadcasting and the broadband Internet. In the proposed system, the augmented objects are downloaded and rendered in compliance with instructions described in a metadata. The metadata includes the time information to synchronize the representation of the original video images and the rendered augmented-object images. And the metadata is delivered in compliance with MPEG-2 system. Inevitably, the architecture of the MPEG-2 transmission stream multiplexer should be slightly modified to insert the time information for the synchronously compositing. The metadata should be packetized in compliance with the MPEG-2 system. So, we propose a packetized elementary stream format for the metadata. Additionally, we propose an interaction mechanism using a second-screen device that supports touch-screen capability. With second-screen devices, TV viewers can manipulate the augmented objects displayed on TV screen. Moreover, a lot of additive contents synchronized or correlated to TV programs can be automatically popped up on the screen of second-screen device.

Unified control architecture for 5G convergence network

Future data traffic is expected to be tremendously increased. The huge traffic is necessary to be supported by various types of access networks rather than a single type of access network. The 5G network assumes fixed wireline and WiFi as access technologies as well as a new 5G Radio Access Technology (RAT). In this paper, we discuss a unified control architecture to provide access control and session control using a common signaling scheme in 5G. The proposed unified control minimizes access network dependency. The discussion of access control and session control reveals our study on their functionalities. Although the proposed architecture is not fully comply with 3GPP developing standard, our study on access control and session control reveals their functionalities.

Unified access control for 5G convergence network with DHCP

Traditionally wireline network and wireless network have been operated and managed separately. Future network will provide converged network service on wireline and wireless networks together. Service requirement for unified access to both wireline and wireless networks emerged as we experience more sophisticated network services. This paper discusses a unified access control for 5G convergence network with multiplicity of different access networks. With minor change onto Dynamic Host Configuration Protocol (DHCP) we can reuse authentication information among various access technologies on 5G convergence network. The proposed method enables us to reuse authentication information from one access network onto another access network. Authentication reuse and unified access control will reduce complexity of 5G convergence network access procedure with multiple access networks and provide consistent access procedure regardless what access technology a user chooses to use.

Design of TV context manager for TV call-up services

This paper describes a TV context managing system to provide a call-up service to TV users. In order to look up which user is using which TV terminal, TV context manager will manage N:N relationships among TV users and TV terminals, and various attributes of them. TV context manager includes a communicator to acquire context information from TV terminals and a controller to manage the acquired TV context information. TV context manager performs registering one or more TV terminals; acquiring context information from each TV terminals registered; and maintaining the acquired TV context information to provide TV call-up services to the TV users.

Design of user interface prototype for Augmented Broadcasting

Augmented Broadcasting (AB) service intends to provide personalized broadcasting service over a TV program. Each user may watch different augmented content (AC) overlaid on the same TV program. The restricted capability of the existing user interface technology limits handling of AC presented on the TV screen. This paper introduces prototypes of user interface (UI) devices for AB services. We realized AB UI devices from smart pads, to haptic gloves and to playing robots.

Probabilistic 1-D mobility model for multi-radio overlay networks simulation

Over the last few years we are deploying various kinds of radio access technologies (RATs). Different kinds of RATs are being deployed in overlay, providing different services in terms of their bandwidth, coverage, Quality of Service (QoS), price, etc. Under the multi-radio overlay network environment RAT selection becomes an important issue for efficient use of radio access networks. One of the most important parameters in RAT selection algorithms is user mobility. According to various user mobility pattern selected RAT may be different, even with the same other parameter sets including place and time. Wrong selection of RAT calls for ping pong or subsequent handover, which causes inefficient use of radio and network resources. In order to verify user mobility effects under multi-radio overlay environment a proper mobility model is crucial. Numbers of previous mobility models were considered but they lack probabilistic change of speed between zones which are of different mobility characteristics. In this paper we propose speed-changing probabilistic 1-D mobility model and show how the speed is changing from zone to zone comparing with previous works.

Asymptotic Throughput Analysis on Opportunistic Cophasing System with Single-Beam Transmission

Different from the opportunistic beamforming system (OBS) that randomizes both amplitude and phase of its beamforming vector, the opportunistic cophasing system (OCS) randomizes the phase only, which significantly reduces the demands on the dynamic range of power amplifiers. Focusing on the multi-user case of the OCS system, we give an asymptotic analysis on the system throughput under Rayleigh fading channels, based on the theory of extreme order statistics. Numerical and simulation results are presented to compare the OCS with the OBS system in throughput.