• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.158-164
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• 2006

Mobile operators will face many challenges both economically and technically, as WLAN evolve through a bewildering number of different standards during the coming years. Potentially this will require several upgrades to the mobile infrastructure. A new approach for addressing these challenges is evaluated in this paper. It is based on a radio over fiber (RoF) technology that uses electro-absorption modulator (EAM) and optical single sideband (OSSB) modulation technique and it promises to provide solutions that will be transparent to changes in protocols and frequency of operation as well as reducing radio access infrastructure costs. This paper describes the development of prototype RoF system based on the 60GHz band CATV transport distribution system with EAM and the possibility of radio over fiber technology for use in the broadband convergence network (BcN) wireless access infrastructure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1B
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• pp.1-7
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• 2004

Increase of internet users and new type of applied traffic such as game, news, distributed computing, online image conference, and real time audio and video have leaded to demand for more bandwidth for each application. This algorithm represents a complex optical exchanger having typical wavelength switching function and time-slotted transmission function. Performance assessment of the proposed OXC (Optical Cross connect) sttucture defines LFS (Limit Frame Size) and VFS (Variable Frame Size) for classification by packet type and calculates the channel effect and loss probability depending the demanded bandwidth by access node increase. Optical exchanger in this type of structure can guarantee future network expansion as well as decrease of frame collision resulted from node increase.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.5
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• pp.25-34
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• 1997

Relatively slow tuning speed of optical device causes the unwanted delay in high speed single-hop multiwavelength networks. To lessen the overhead, we present a channel access protocol with dynamjic message scheduling. Th eframe structure of proposed protocol adopts hybrid multiaccess scheme in which WDMA is used as a basic multiaccess technique and TDMA is used to provide subchannels within a wavelength band. This architecture has two merits : the network extention is not limited by available number of wavelengths, and the transmission delay caused by optical device tuning time can to minimize the number of tunings. It schedules messages that require same wavelength channels sequencely, so the total transmission delay is reduced by decreasement of wavelength changes. The performance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The peformance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The numeric results show that the peformance of proposed protocol is better than that of previous one.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.457-465
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• 2003

In this paper, we analyze the performances of variable MAC (Medium Access Control) protocols and present an efficient MAC protocol for Ethernet PON (Passive Optical Network). We consider three MAC protocols: static TDMA, dynamic TDMA, and Interleaved polling. Static TDMA assigns an equal amount of bandwidth to all ONUs regardless of the request information but Dynamic TDMA dynamically allocates the bandwidth to each ONU considering its request. Interleaved Polling operates a cycle with variable time period and a polling method for informing a uplink transmission chance to each ONU. This paper theoretically analyzes the available bandwidth for each of three protocols. We also implement the simulation models for them by using OPNET and evaluates the performances under various bursty traffic environments. The results are compared and analyzed in terms of channel utilization and queueing delay.

• ETRI Journal
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• v.43 no.5
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• pp.799-811
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• 2021

This paper considers a challenging problem: to simultaneously optimize the cost and the quality of service in opaque wavelength division multiplexing (WDM) networks. An optimization problem is proposed that takes the information including network topology, traffic between end nodes, and the target level of congestion at each link/ node in WDM networks. The outputs of this problem include routing, link channel capacities, and the optimum number of switch ports locally added/dropped at all switch nodes. The total network cost is reduced to maintain a minimum congestion level on all links, which provides an efficient trade-off solution for the network design problem. The optimal information is utilized for dynamic traffic in WDM networks, which is shown to achieve the desired performance with the guaranteed quality of service in different networks. It was found that for an average link blocking probability equal to 0.015, the proposed model achieves a net channel gain in terms of wavelength channels (𝛾_w) equal to 35.72 %, 39.09 %, and 36.93 % compared to shortest path first routing and 𝛾_w equal to 29.41 %, 37.35 %, and 27.47 % compared to alternate routing in three different networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.573-578
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• 2000

This paper presents a noble optical access system using shared laser and LED light sources, which is based on WDM-PON technologies. This system adopts an external modulation of the shared laser sources for high-speed downstream and a direct modulation of the LED sources for low-speed upstream. To split or combine the transmission channels, AWG(Arrayed Wave-guide Grating) devices are used in the optical cable section. The proposed system is attractive for low cost implementation. The laser light sources can share the optical carriers in the downstream scheme. Also, in upstream, the LED sources can afford to make simple of the circuits for controlling light source and of standardization for ONU(Optical Network Unit). The feasibility of the proposed system is demonstrated by several experiments. Our results show that the system operates well at 2.SGbps for downstream and up to 622.08Mbps for upstream.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.1-7
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• 2020

The secure access the lighting, Heating, ventilation, and air conditioning (HVAC), fire safety, and security control boxes of building facilities is the primary objective of future smart buildings. This paper proposes an authorized user access to the electrical, lighting, fire safety, and security control boxes in the smart building, by using color grid coded optical camera communication (OCC) with face recognition Technologies. The existing CCTV subsystem can be used as the face recognition security subsystem for the proposed approach. At the same time a smart device attached camera can used as an OCC receiver of color grid code for user access authentication data sent by the control boxes to proceed authorization. This proposed approach allows increasing an authorization control reliability and highly secured authentication on accessing building facility infrastructure. The result of color grid code sequence received by the unauthorized person and his face identification allows getting good results in security and gaining effectiveness of accessing building facility infrastructure. The proposed concept uses the encoded user access authentication information through control box monitor and the smart device application which detect and decode the color grid coded informations combinations and then send user through the smart building network to building management system for authentication verification in combination with the facial features that gives a high protection level. The proposed concept is implemented on testbed model and experiment results verified for the secured user authentication in real-time.

• ETRI Journal
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• v.34 no.6
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• pp.838-846
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• 2012

This paper proposes a cost-effective hybrid-type power budget extender (PBEx) that can provide a high power budget of over 45 dB in an asymmetric 10-Gb/s Ethernet passive optical network (10/1G-EPON). The hybrid-type 10/1G-EPON PBEx comprises a central office terminal (COT) and remote terminal (RT) module supporting four channels and uses a coarse wavelength division multiplexing (CWDM) technology between the COT and RT for a reduction of fiber cost and efficient access network design. The proposed 10/1G-EPON PBEx can provide over a 40-km reach and 128-way split per CWDM wavelength with no modification of a legacy 10/1G-EPON system and can satisfy the error-free service in $10^{10}$ packet transmission.

• Electronics and Telecommunications Trends
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• v.32 no.5
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• pp.97-106
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• 2017

The introduction of new access technologies in 5G radio networks has had a considerable impact on the design of transport networks. Research activities are underway on new transport technologies in both the wireless and optical domains to support 5G transport. This paper provides an overview of the concept and requirements of a fronthaul. We also discuss the research activities of a new fronthaul interface for future 5G networks, a 5G integrated fronthaul/backhaul transport network (5G-Crosshaul), a next-generation fronthaul interface (NGFI), a mobile xhaul network (MXN), and a next-generation mobile fronthaul architecture with multi-IF carrier transmission scheme.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.31-40
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• 1997

This paper presents a hybrid WDM/TDM channel acess protocol for high speed WDM networks based on passive double star topology. In the proposed scheme, all nodes in a network are splitted into groups forming passive double star topology and each node has a tunable transmitter and a fixed receiver. WDM channels are allocated to the groups, which are used as home channels to transmit or receive packets. TDM frames of the WDM channel are composed of the same number of slots as that of groups, and all nodes in a group transmit packets simultaneously at each slot. The proposed scheme reduces the system complexity and the number of the required WDM channels. It was proved that the proposed protocol is less sensitive to the propagation delay and maintaining its superior transmission performance by employing the efficient transmission schedule based on passive double star topology.