Yun-Joo Kim

QoS provisioning in domain based mobile IP networks

In this paper, we propose a scalable domain-level call admission control (CAC0 algorithm supporting a novel dynamic reservation method in mobile IP (MIP) enable Internet. MIP tunnels enable for a mobile node to move to another subnet on a session. In order to prevent a service quality from being degraded in MIP networks, it is necessary to deliberate the quality of service (QoS) provisioning on the MIP tunnels especially for roaming mobile nodes (MNs) to foreign networks Our CAC algorithm keeps a handoff dropping probability (HDP) below a pre-defined value without regard to overloads of mobility agents (MAs). Our proposed scheme uses the number of calls that will be handed off from neighboring MAs and the number of calls in the current MA. We assume that each class has both a HDP and a desired bandwidth. The proposed admission control algorithm can be expanded to serve not only single class but also multi-class with different QoS requirements. Furthermore, we introduce an aggregated dynamic resource allocation method to reflect incoming call patterns and to reduce the number of reservation signals for the tunnels which can cause the increase in network traffics and the data loss during the handoff processing. We show that our scheme guarantees the given HDP and reduces the number of reservation signals comparing trunk reservation methods.

Design and FPGA implementation of MIMO-OFDM based WLAN Systems

For higher data rate wireless communication, multiple antenna and orthogonal frequency division multiplexing (OFDM) schemes are considered as a key technology. In IEEE 802.11 TGn (Task Group n), multiple input multiple output-OFDM (MIMO-OFDM) methods, including spatial division multiplexing (SDM), are adopted for a higher throughput solution in the next generation wireless local area network (WLAN) physical (PHY) layer. In this paper, we design a transmission architecture based on dual-band and MIMO-OFDM schemes and media access control (MAC) layer using the enhanced distributed channel access (EDCA) including a block acknowledgement (ACK) method. Moreover, test results of this prototype system implemented with field programmable gate arrays (FPGA) are introduced

Power aware wireless receiver design utilizing carrier sensing based on cross-correlation

Advancing technology has made it possible to integrate millions of transistors on a very small die and to clock these transistors at very high speeds. Power consumption has become the limiting factor for portable high-performance wireless applications. In this paper, we propose a system level technique to improve the power efficiency of the wireless receiver design. The proposed clock gating scheme utilizing carrier sensing based on cross-correlation is a very effective power-saving technique to reduce the dynamic power dissipation of the inactive circuit blocks and their local clock buffers.

Multi-Gigabit MAC Structure Design for IMT-Advanced Wireless Nomadic Access

In this paper, a new IMT-Advanced wireless communication system employing the proposed MAC frame structures was implemented and demonstrated. The proposed MAC frame structures are designed to provide Gbps data service under the nomadic environment. The implemented system provided near 1.8Gbps MAC throughput. It is shown that the implemented system with the proposed MAC frame structures can meet IMT-Advanced wireless access requirements and it is one of the promising solutions for the future multi-gigabit wireless communication systems.

MAC implementation for IMT-advanced multi-gigabit nomadic systems

In this paper, high performance MAC is designed and implemented to support multi-gigabit nomadic access systems. New algorithms and Control channels are introduced for low MAC latency and high MAC throughput. The new multi-gigabit nomadic/local area wireless access, called NoLA, is implemented using the proposed MAC. NoLA demonstrated the multi-gigabit service with full HD video streams where the proposed high performance MAC supports the 84 full HD video streams in real time. The implemented NoLA system shows near 1.8 Gbps MAC throughput, which can meet the requirements of the gigabit IMT-advanced wireless nomadic access. It is proved that the proposed high performance MAC used in NoLA can be one of the promising solutions for the future multi-gigabit wireless communication systems.

Photonic-Frame-Based TCP proxy architecture in optically interconnected data center networks

Abstract Optical switching is a good candidate for achieving the key requirements of high scalability, low latency and low power consumption in future large-scale data center networks (DCNs). However, circuit-based optical switching has a disadvantage of a long reconfiguration time. Packet-based optical switching also faces challenges such as the complexity of optical header processing and the difficulty of buffering in optical switches to resolve contention. To address these problems, we present a packet-switched optical network architecture design with a photonic frame wrapper that can generate variable-size photonic frames for optically interconnected intra-DCN. The proposed architecture forms hybrid DCN architecture consisting of a flattened optical switch layer for the data path and a conventional electrical switch layer for the control path. The photonic frame wrapper can increase bandwidth utilization by minimizing guard-time insertion in the optical switch domain. We also introduce a photonic frame wrapper with proxy solution to fully exploit the gain of the proposed architecture even in inter-DCN communication with long delays, which is compliant with standard TCP instances at end nodes. In intra-DCN, the average queuing delay is analyzed to find the efficient combinations between the guard time and time-slot length for the variable-sized photonic frame. We also analyzed the bandwidth overhead of guard time, to show it is comparable to that of Ethernet based DCN. In inter-DCN, the proxy solution demonstrates a noticeable TCP performance enhancement compared with the photonic frame wrapper in terms of bandwidth efficiency and end-to-end delay by theoretical and OPNET simulation analyses.

A fully-hardwired implementation of large vocabulary continuous speech recognizer

This article presents the hardware implementation of the speech recognition for real time performance and high-level accuracy. The stand-alone speech recognizer should simultaneously achieve the requirements, which are the low-latency performance and the low-power dissipation in an environment that cannot connect to the network. So, we made a speech recognizer as the hardware accelerator based on the hidden Markov model for reducing the load of the system processor without the cloud computing. Our overall design has the fully hardwired operation flow from the generation of the speech feature to the generation of the recognized words. Our design showed low-latency performance as the real time factor of 0.4 ~ 0.5 on FPGA, which operates at 100MHz operating frequency and uses the resource of 10%.

The hardware accelerator of the automatic speech recognition for the continuous Korean words

This paper describes the hardware of the speech recognition. The embedded speech recognizer should meet two conditions for the low-latency performance and the low-power dissipation. So, we made the fully-hardwired speech recognizer as the hardware accelerator to offload the system processor without the support of the remote computing environment. Our overall design was designed and implemented on FPGA board. Our design showed speedy response as the real time factor of 0.4 ~ 0.5 at 100MHz operating frequency and uses the HW resource of 10.

Multi-Gbps MAC Design and Real-Time Experiment for IMT-Advanced Wireless Nomadic Access

In this paper, high performance MAC is designed and implemented to support multi-gigabit physical layer. New algorithms and Control channels are introduced for low MAC latency and high MAC throughput. The new multi-gigabit nomadic/local area wireless access, called NoLA, is implemented using the proposed MAC. NoLA demonstrated the multi-gigabit service with full HD video streams where the proposed high performance MAC supports the 84 full HD video streams in real time. The implemented NoLA system shows near 1.8Gbps MAC throughput, which can meet the requirements of the gigabit IMT-Advanced wireless nomadic access. It is proved that the proposed high performance MAC used in NoLA can be one of the promising solutions for the future multi-gigabit wireless communication systems.

Next generation wireless LAN system design and implementation based on MIMO-OFDM

Multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) is regarded as a promising technology enabling higher data rate wireless communications in frequency selective fading channels. This paper proposes the next generation wireless local area network (WLAN) physical (PHY) layer transmission technology using dual-band and MIMO-OFDM schemes and media access control (MAC) layer based on the enhanced distributed channel access (EDCA) scheme. Also it shows test results of MIMO-OFDM prototype system implemented with field programmable gate arrays (FPGA). This design targets over 200 Mbps of the maximum PHY data rate in 40 MHz