Chia-Lung Liu

Industrial Technology Research Institute

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Woei Lin

National Chung Hsing University

Chin‐Chi Wu

Nan Kai University of Technology

Hsi-Lu Chao

National Yang Ming Chiao Tung University

Kuei-Li Huang

Industrial Technology Research Institute

Chun-Kai Tseng

National Yang Ming Chiao Tung University

Gan Chai-Hien

Chao Hsi-Lu

Wu Sau-Hsuan

Ding‐Jyh Tsaur

National Chung Hsing University

Chai‐Hien Gan

Industrial Technology Research Institute

Cooperative Institutions

National Yang Ming Chiao Tung University

Industrial Technology Research Institute

National Taiwan University

National Chung Hsing University

National Cheng Kung University

National Taiwan University of Science and Technology

National Taipei University

Czech Academy of Sciences, Institute of Computer Science

Nan Kai University of Technology

China Medical University

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A Local IP Access Mechanism for VoIP Service in LTE Home eNodeB Systems

Chia-Hsuan Chang Hsi-Lu Chao Chia-Lung Liu Kuei-Li Huang Yi‐Bing Lin

The need for multimedia communication through wireless media brings development of 4G cellular wireless networks. Long Term Evolution (LTE) is one of 4G standards and specified in 3GPP. In an LTE system, home base station (HeNB) is designed for indoor usage. Since packets are always routed back to the core network before to destination, if two user equipments (UEs) stay in the same HeNB, the routing path is detour and results in longer packet delivery delay, jitters and thus lower data throughput. As a result, the idea of local IP Access (LIPA) was drawn and two solutions have been proposed. However, the two solutions would suffer from poor voice quality in a VoIP application. We propose a novel solution which establishes an additional data radio bearer (DRB) between UE and HeNB to detect local packets. Once local packets are detected, the data radio bearer is then responsible for local packet delivery. Simulation results show that our method outperforms the other two solutions in terms of packet delivery delay and mean opinion score (MOS).

EnodeB

LTE Advanced

Radio Link Protocol

Core network

10.1109/imis.2013.10

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Citations (3)

A DDRR-Based Scheduler to Achieve Proportional Delay Differentiation in Terabit Network

Chin‐Chi Wu Hsien-Ming Wu Chia-Lung Liu Woei Lin

In recent years much attention has been given to providing the proportional delay differentiation through the packet scheduling. The issue of the performance of the scheduling algorithms also increases in importance when the line speed increases significantly as a result of the optical technology. In this paper we propose an efficient packet scheduling scheme modified from the dynamic deficit round-robin (DDRR) scheduling algorithm. The new scheme not only provides the tuning knob for adjusting the relative QoS in the packet delay but also performs scheduling at O(1) complexity and with very small overhead. Simulation results show the effectiveness of the modified algorithm.

Terabit

10.1109/aina.2005.18

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Citations (4)

高密度スモールセルネットワークにおける協調マルチポイント伝送のための効果的なアンテナ割当【Powered by NICT】

IEEE Conference Proceedings (2016)

Chun-Kai Tseng Wu Sau-Hsuan Chao Hsi-Lu Chia-Lung Liu Gan Chai-Hien

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Performance Evaluation of the Parallel Packet Switch with a Sliding Window Scheme

Lecture notes in computer science (2006)

Chia-Lung Liu Chiou Moh Chin‐Chi Wu Woei Lin

Sliding window protocol

Packet Switching

Fast packet switching

10.1007/11751588_118

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An Effective Antenna Allocation for CoMP Transmission in Dense Small Cell Networks

2015 IEEE Global Communications Conference (GLOBECOM) (2016)

Chun-Kai Tseng Sau-Hsuan Wu Hsi-Lu Chao Chia-Lung Liu Chai‐Hien Gan

Despite that network capacity can increase with cell densification, interferences from adjacent cells may deteriorate the throughput of users close to cell edges. To alleviate this problem and to offer a service quality with no significant cell edge degradation, we propose a feasible coordinated multi-point (CoMP) transmission architecture from a new look on antenna allocation in dense small cell networks (DSN). The CoMP idea is based on a two-step mechanism; the first step partitions the entire service region into multiple areas, and the second step adjusts the number of active users for each area. We then develop an antenna allocation algorithm to enhance the cell-edge user throughput, making use of the spatial multiplexing (SM) gain, array gain and cooperative diversity gain. Simulation results show that applying SM to DSN plays a crucial role to enhance the user throughput. And one of our proposed cooperative schemes is shown to have a great potential to improve the throughput for a large portion of users or the cell service area.

Small cell

Antenna diversity

Spatial multiplexing

10.1109/glocom.2016.7841585

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Performance enhancement of contention-based bandwidth request mechanism in IEEE 802.16 WiMAX networks

Shih-Fan Chou Jen-Hsi Liu Hsi-Lu Chao Tzu-Chi Guo Chia-Lung Liu

The IEEE 802.16 standard is a promising technology for 4G mobile networks. Though supporting versatile service classes, best effort (BE) service class is expected to dominate WiMAX networks, due to operational simplicity. One of bandwidth request mechanisms that subscriber stations (SS) can utilize to issue bandwidth requests (BW-REQ) for BE connections is contention-based random access. An SS starts a timer T16 when transmitting a BW-REQ. If getting a grant before timer expiration, the SS transmits data packets at the allocated time slots; otherwise it performs truncated binary exponential backoff process for BW-REQ retransmission. The default value of T16 is one frame time. However, T16 impacts on contention and request collision significantly. In the paper, we develop an analytical model for T16 timer setting. Besides, we derive analytical expressions for the average number of tries per BW-REQ and the average packet delay. We compare the theoretical results of fixed and adjustable timers. The results show that adjusting timer reduces both the number of collision and the average packet delay.

Timer

Exponential backoff

Retransmission

WiMAX

10.1109/pimrc.2010.5672025

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Citations (8)

Sum Throughput-Improved Resource Allocation for LTE Uplink Transmission

Ching-Hsu Chang Hsi-Lu Chao Chia-Lung Liu

Long Term Evolution (LTE) is a promising technology for 4G mobile networks. Due to utilize OFDMA in downlink and SC-FDMA in uplink, the LTE system is expected to provide significantly high throughput with 20 MHz spectrum allocation. To increase the cell throughput and multi-user diversity gain, channel dependent scheduling (CDS) is implemented for the OFDMA-based multi-user scenario to allocate resource blocks (RBs) to users experiencing better channel conditions. Nevertheless, CDS may not perform well in SC-FDMA due to its two inherent constraints one is contiguous RB assignment and the other is robust modulation and coding mode. In this paper, the formulation of resource allocation for a SC-FDMA system upon considering two inherent constraints is proposed. Since the optimization problem of resource allocation in SC-FDMA is NP-hard, we further propose two heuristic algorithms to find feasible solutions. We evaluate the proposed formulation and heuristic algorithms by conducting simulation. The simulation results show that our methods achieve significant performance improvement not only in system sum throughput but also in transmission delay.

Frequency-division multiple access

LTE Advanced

Diversity scheme

Channel allocation schemes

Diversity gain

10.1109/vetecf.2011.6093138

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Citations (23)

A Study on the Mechanical Behavior of All-Casing Pile Ultimate Bearing Capacity

Chia-Lung Liu 劉家隆

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An Effective Antenna Allocation for CoMP Transmission in Dense Small Cell Networks

IEEE Conference Proceedings (2016)

Chun-Kai Tseng Wu Sau-Hsuan Chao Hsi-Lu Chia-Lung Liu Gan Chai-Hien

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Evaluation and Analysis of the Sliding-Window Parallel Packet Switch

Chia-Lung Liu Woei Lin Chin‐Chi Wu

This work analyzes the performance of the parallel packet switch (PPS) with a sliding window (SW) method under bursty data traffic. The PPS comprises multiple packet switches operating independently and in parallel. The typical PPS dispatch algorithm uses a round-robin method (RR) (Iyer, 2003). The class of PPS is characterized by deployment of parallel center-stage switches that all memory buffers run slower than the external line rate. A novel SW packet switching method for PPS, called SW-PPS, is proposed. Under identical bursty data traffic, the SW-PPS provided improved performance when compared to RR-PPS. A mathematical, analytical model for SW-PPS is proposed. In addition, a novel bursty data traffic model is proposed: a packet-based bursty data traffic model. This packet-based bursty data traffic model can emulate more realistic network, and thus, produces more realistic simulation results.

Sliding window protocol

Packet Switching

Fast packet switching

Traffic model

10.1109/aina.2005.176

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Citations (2)