Combined ICA and FCA Schemes for a Hierarchical Network

A combined idle channel assignment (ICA) and fixed channel assignment (FCA) scheme is proposed to improve the traffic performance in a hierarchical network. This dual-mode network integrates the Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes of the Universal Mobile Telecommunication System (UMTS) and Terrestrial Radio Access (UTRA) in a given cell. This approach includes a high traffic load area and a blocked area as an example to evaluate the traffic performance. The ICA threshold and network timeout period effects on the traffic performance of this integrated dual-mode network are also investigated. The analytical results show that the handoff failure probabilities of the integrated dual-mode network can be reduced significantly with a minimal increase in the new call blocking probability when the combined ICA and FCA scheme replaces the FCA scheme. The integrated dual-mode network using the combined ICA and FCA scheme also increases the carried traffic. The traffic performance improvements for non-uniformly generated new calls are more significant than those for uniformly generated new calls when the combined ICA and FCA scheme is used. An increase in the high ICA threshold will result in an increase in the total carried traffic and an increase in the new call blocking and handoff failure probabilities for higher-tiered and low-tiered systems located in the high traffic load area. The traffic performance was evaluated using the discrete time simulation method to validate the analysis results.     

FLC-Based MBWIMA/UMTS Protocol for Multimedia Services in UTRA TDD Mode

An intelligent medium access control (MAC) protocol based on fuzzy logic control (FLC) is proposed and compared with a general packet radio system in UMTS (GPRS/UMTS), priority scheme and the movable boundary wireless integrated multiple access in UMTS (MBWIMA/UMTS) protocols. The integrated video/voice/data services of UMTS in UTRA TDD mode have different transmission properties. By fuzzy logic control, the resources of the wireless communication can be intelligent assigned for different types of mediums. The voice-video dropping probability and data packet delay are input to FLC to optimally select the maximum number of voice/video slots. Voice activity detector (VAD) and multiple access interference in single cell are also considered in the simulations.     

Intelligent MBWIMA/UMTS Protocol Using SDMA Scheduling in UTRA TDD Mode

The intelligent medium access control (MAC) protocol based on cascade fuzzy logic control (CFLC) using the first-duplicated space division multiple access (SDMA) scheduling for UTRA TDD mode is presented in this paper. Voice, data and video are integrated for transmission using CFLC-based movable boundary wireless multiple access in the UMTS (MBWIMA/UMTS) protocol. The CFLC-based MBWIMA/UMTS protocol performance with data rate control is optimized using the CFLC to generate the proper maximum number of voice/video slots and a suitable data rate. The first-duplicated SDMA scheduling, which provides the SDMA scheduling management, can increase the wireless mobile system capacity and reduce the voice-video dropping probability. The simulation results demonstrate that the CFLC-based MBWIMA/UMTS protocol using the first-duplicated SDMA scheduling can greatly improve both the voice-video dropping probability and data packet delay, compared with the MBWIMA/UMTS and GPRS/UMTS protocols using the first-duplicated SDMA scheduling at the expense of a small decrease in data packet throughput. Jeich Mar received the M.S. degree in electrical engineering from the National Taiwan University, Taiwan, R.O.C., in 1974 and the Ph.D. degree in electrical engineering from the University of Southern California, Los Angeles, in 1981. From 1981 to 1991, he worked as a Scientist in the Chung-Shang Institute of Science and Technology, Taiwan, where the worked on the development of a signal processor for phased array radar. He is currently a Professor in the Department of Communications Engineering, Yuan-Ze University, Taoyuan, Taiwan. His research interests include mobile communication and ap-plications of signal processing in Radar and Communication. Chih-Yang Kao was born in Hualien, Taiwan, Republic of China, 1974. He received the B.S., M.S. and Ph.D degree in electrical engineering from Yuan-Ze University, Taiwan in 1996, 1998 and 2004, respectively. He is now with Computer & Communications Research Laboratories, Industrial Technology Research Institute (CCL-ITRI). His current research interests include digital video broadcasting and wireless medium access control of next-generation mobile communication systems.     

A car-following collision prevention control device based on the cascaded fuzzy inference system

A car-following collision prevention control device based on the cascaded fuzzy inference system (CFIS), consisting of a velocity fuzzy controller and an acceleration fuzzy controller, to nonlinearly control car acceleration or deceleration rate is proposed. The distance and speed relative to the car in front are measured using spread spectrum radar and applied to the collision prevention control device. The output acceleration or deceleration rate obtained from the CFIS car-following collision prevention system is based on the characteristics of the vehicle. The simulation results demonstrate that the presented CFIS control device can solve the oscillation problems for final relative distance between the lead vehicle (LV) and following vehicle (FV) and relative speed. When the LV applies the brake suddenly or a stationary obstacle appears in front of vehicle moving at high speed on the roadway, the CFIS control device can safely avoid a collision. The CFIS car-following collision prevention control device proposed in this paper can provide a safe, reasonable and comfortable drive.     

Performance analysis of WIMA/SAD protocol for integrated voice/data wireless networks

In this paper, the “Wireless Integrated Multiple Access (WIMA) with Speech Activity Detector (SAD)” protocol for Time Division Duplex (TDD) and Frequency Division Duplex (FDD) hierarchies is proposed and analyzed. This scheme is based on a mixture of movable-boundary WIMA protocol and speech activity process. Both voice and data traffic are handled on a packet reservation basis. The access slot of every uplink frame is allocated on the last slot to save the waiting time of queuing data. The expected data-packet delay for fixed-boundary WIMA, movable-boundary WIMA, and WIMA/SAD protocols are evaluated. Numerical results illustrate the dependence of performance on the system parameters, and demonstrate that the WIMA/SAD protocol provides a lower expected data-packet delay than the movable-boundary WIMA protocol for the values of voice-call completion probability ( μ _v) less than 0.1. As μ _v increases, the expected data-packet delay of the WIMA/SAD protocol approaches to movable-boundary WIMA protocol. The maximum data throughput of WIMA/SAD protocol has smaller variation than that of the movable-boundary WIMA protocol when voice-call completion ratio is changed. This revised version was published online in June 2006 with corrections to the Cover Date.     

FPGA Implementation of SDR Based CFO Estimation and Compensation Circuit for OFDM System

Based on software defined radio (SDR) architecture, this paper develops a reconfigurable CORDIC vectoring module (CVM) and CORDIC rotation module (CRM) in FPGA to implement the carrier frequency offset (CFO) estimation and compensation circuits of an orthogonal frequency division multiplexing (OFDM) system. The experimental results show that the proposed SDR-pipelined architecture can save power and hardware resource compared with conventional pipelined architecture, because the designed CVM and CRM modules can be reused in the processing modules of CFO estimation and compensation circuit. The performance trade-off for CVM and CRM implemented with different quantized float number in FPGA is presented. Furthermore, the hardware reconfiguration function of CVM and CRM is also validated.     

The Complementary Use of 3G WCDMA and GSM/GPRS Cellular Radio Networks

The traffic performance of integrated 3G wide-band code division multiple access (WCDMA) and GSM/GPRS network is evaluated. This type of network links two cellular radio systems which have different set of frequency bands and the same coverage size. The base station of 3G WCDMA is installed on an existing GSM/GPRS site. Dual-mode mobile terminals use handoff to establish calls on the better system. The soft handoff or inter-frequency hard handoff occurs when mobile terminals of 3G WCDMA or GSM/GPRS move between two adjacent cells, respectively. The inter-system hard handoffs are used between 3G WCDMA and GSM/GPRS systems. The data rate conversions between different systems, soft handoff region size, multiple data rate multimedia services, and the effect of the mobile terminal mobility on the user mean dwell time in each system are considered in the study. The simulation results demonstrate that a great traffic performance improvement on the complementary use of 3G WCDMA and GSM/GPRS cellular radio networks compared with the use of GSM/GPRS cellular radio networks. When high-data rate transmission is chosen for low-mobility subscribers, both the handoff failure probability, and carried traffic rates increase with the new call generation rate. However, both rates decrease conversely with the increasing new call generation rate as soon as the new call generation rate exceeds a critical value. This causes the integrated networks saturation. The higher mean speed for the mobile terminals produces lower new call blocking probabilities and total carried traffic. The new call blocking probabilities and total carried traffic increase with the size of the soft handoff region.