Hwang-Cheng Wang

A Proxy Mobile IPv6 Based Global Mobility Management Architecture and Protocol

This paper specifies a global mobility management architecture and protocol procedure called GPMIP, which is based on Proxy Mobile IPv6. In GPMIP, mobility management is performed by the network entity rather than individual mobile nodes. The benefit is the elimination of the wireless link data delivery tunnel overhead between a mobile node and the access router. To compare with the well known Hierarchical Mobile IPv6 mobility management protocol, the location update, packet delivery, and total cost functions generated by a mobile node during its average domain residence time are formulated for each protocol based on fluid flow mobility model. Then, the impacts of various system parameters on the cost functions are analyzed. The analytical results indicate that the proposed global mobility management protocol can guarantee lower total costs. Furthermore, a qualitative comparison between GPMIP and some other global management protocols is also investigated.

Inductively Coupled Loop Antenna Design for UHF RFID on-Body Applications

This paper presents a one-wavelength loop antenna fed by an inductively coupled loop for on-body applications. An equivalent circuit for the inductively coupled loop antenna is proposed to synthesize the antenna system with a microchip. The designed tag is printed on a PVC substrate and placed close to a four-layer stratifled elliptical cylinder human model. The card-type tag measures 85:5 £ 54 £ 0:76mm 3 and is suitable for use on a student ID card for a broad range of applications. The impedance bandwidth of the inductively coupled loop tag antenna is 60MHz (880{940MHz, 6.6%), which covers the operating UHF bands in U.S. and Taiwan. The measured reading distance ranges from 2.7 to 5.7 meters when placed at difierent positions on the chest of a human body in the open site.

Energy-Efficient DRX Scheduling for QoS Traffic in LTE Networks

LTE has been touted as a leading-edge mobile communication technology offering high data rate and low latency. However, with a sophisticated physical layer to boost performance, the processing demand on user equipment (UE) is tremendous, which implies that the energy consumption is heavy. To curb undesirable energy waste and extend battery life, a variety of energy-conserving measures have been developed, among which discontinuous reception (DRX) is shown to be useful. This paper introduces the light sleeping mode in order to further improve the performance of DRX for traffic with QoS requirements in LTE networks. The key idea of light sleeping is to turn off the power amplifier but leave the other components in the transceiver on to cut down energy consumption while allowing fast wakeup. Quantitative analysis shows that the proposed method can substantially reduce energy consumption and satisfy the delay requirement of QoS traffic.

An accurate power analysis model based on MAC layer for the DCF of 802.11n

The 802.11 wireless local area network technology is popular in power-sensitive devices such as smart phones and personal digital assistants. In this article, we present an accurate power consumption model based on the Bianchi model and power measurement in the physical layer to predict the power consumption of 802.11n and multiple-input–multiple-output mode of 802.11n. In this model, we calculate the total energy consumption by summing up several components: the idle listening energy consumed in the distributed inter-frame space period and backoff stages, the energy consumed in transmitting a frame, the idle listening energy consumed in the short inter-frame space turnaround time, the energy consumed in receiving an acknowledgment frame from the access point, and the energy consumed in collisions for one frame transmission. The probability of successful frame transmission and medium access control (MAC) efficiency of 802.11n are also analyzed as a function of the number of active stations and different choices of frame transmission probability by each active station. Finally, the impact of imperfect channels on energy consumption and MAC efficiency is explored.

Robust LTE uplink scheduling based on call admission control

In LTE system, it is difficult for an eNB to properly allocate uplink resource blocks (RBs) to UEs as many factors complicate the issue. So far, most research has focused on maximizing system throughput. However, this is often achieved by downgrading other performance metrics and may result in the waste of resources. In this paper, a resource allocation scheme for LTE uplink is proposed which takes into account the data rate granted by call admission control (CAC). Data rate is defined based on exponentially weighted moving average (EWMA). The scheme leads to a close match between user demand and resources actually allocated, thereby making better use of the resources. In addition, robust modulation-coding is considered in resource allocation. Results obtained via simulation show that the proposed scheme demonstrates good performance in important aspects compared to other resource allocation methods.

Task Migration for Energy Conservation in Real-Time Multi-processor Embedded Systems

In recent years, portable devices and tablet PCs grow fast and become more convenient and mobile. Applications like multimedia, SIP, and 3D movies become more diverse than before. However, the complex architecture and heavy computing demands increase energy consumption. Therefore, how to extend the standby and usage time of the devices has become an important issue. In this paper we propose a task scheduling algorithm in a real-time multi-processor system. We reduce the workload in high speed processors with the aid of task migration so that the entire system can switch to low speed as soon as it can in order to reduce energy consumption. A distinctive feature is that actual execution time is used in the decision instead of worst-case execution time, which allows for more effective task migration. Performance results based on realistic processor power consumption models are promising. Effects of parameter values on the performance are also examined.

An Accurate Power Analysis Model Based on MAC Layer for the DCF of 802.11n

802.11 Wireless Local Area Network (WLAN) technology is now common in power sensitive devices like smart phones and personal digital assistants (PDAs). In this article, we present an accurate power consumption model based on the Bianchi model [13] and the power measurement in PHY layer [9] to predict the power consumption of 802.11n and Multiple-Inputs-Multiple-Outputs (MIMO) mode of 802.11n. In this model, we calculate the total power consumption by summing six consumed powers: the idle listening power consumed in the DIFS period, the back-off stage, the power consumed in transmitting a frame, the idle listening power consumed in the SIFS turn-around time, the power consumed in receiving an ACK frame from AP and the power consumed in the collision for one frame transmission. Our analyses and simulations show that the power consumed in idle listing will dominate the total power consumption when the number of the active stations is large. The successful possibility and MAC efficiency of 802.11n are also analyzed and simulated in this article. The imperfect channel scenario will be evaluated, too. This power analysis model to our knowledge has not been presented in the previous works so far.

Energy-efficient tasks scheduling algorithm for real-time multiprocessor embedded systems

In recent years, applications like multimedia, video and audio stream communications, 3D movies, to name a few, have spurred the proliferation of multiprocessor systems, particularly for real-time embedded systems. However, the complex architecture and heavy computing demands of such systems increase power consumption. Therefore, energy conservation has become a critical issue. In this paper, we propose a novel tasks scheduling algorithm for real-time multiprocessor systems. The algorithm works by reducing the workload in high speed processors with the aid of task migration so that the entire system can switch to low speed/low voltage as soon as it can reduce power consumption. The overhead of transitioning to low voltage is also analyzed and used as a criterion to determine whether the transition is beneficial. The effect of important parameters such as task granularity on the performance is also investigated, and simulation results based on realistic processor power consumption models are shown to be promising.

Design and implementation of a hybrid MIPv6/PMIPv6-based mobility management architecture

As two of the most promising candidate solutions for realizing the next-generation all-IP mobile Internet, Mobile IPv6 (MIPv6) is a host-based protocol supporting global mobility, while Proxy Mobile IPv6 (PMIPv6) is a network-based protocol supporting localized mobility. In order to take full advantage of both and enhance the mobility performance, a hybrid MIPv6/PMIPv6-based mobility management architecture is proposed in this paper. First, the optimized coexistence architecture of MIPv6 and PMIPv6 is presented. Based on this architecture, the Hybrid scheme is proposed, in which localized mobility and global mobility are handled by PMIPv6 and MIPv6 respectively to improve the efficiency. Then we propose the Hybrid+ scheme based on the Hybrid scheme. The Hybrid+ scheme incorporates a protocol selection algorithm, which takes into account the mobility characteristics of mobile nodes (MN) and network conditions. This allows it to select the most suitable mobility supporting protocol between the basic MIPv6 and the Hybrid scheme. Performance analysis using a two-layer hierarchical network model reveals that the Hybrid scheme reduces the signaling costs by more than 20% compared to the basic MIPv6 and Hierarchical Mobile IPv6 (HMIPv6). In addition, we have implemented the proposed mobility management architecture in a test-bed. The experimental results show that our Hybrid scheme can improve the handover performance of UDP and TCP sessions over the other mobility management protocols. Moreover, when the protocol selection algorithm is adopted as in the Hybrid+ scheme, the performance can be further improved by more than 50% under various scenarios.

Differentiating and Scheduling LTE Uplink Traffic Based on Exponentially Weighted Moving Average of Data Rate

The importance of uplink resource allocation in ensuring the Quality of Service (QoS) of guaranteed bit rate (GBR) bearers has led to the development of numerous resource allocation schemes. The criteria used in the development of such schemes include maximizing system throughput or fairness and the ability to take transmission power or user priority into account. After accepting a GBR bearer, the eNodeB (eNB) must allocate sufficient resource blocks (RBs) to guarantee the requested QoS. In order to achieve high utilization of radio resource, eNB also must allocate remaining RBs to non-GBR bearers. The QoS is generally specified by the data rate (throughput) or packet delay; however, the 3rd Generation Partnership Project (3GPP) has not specified the means by which data rates for a GBR bearer are to be measured. In this paper, we define the measurement of data rates based on the exponentially weighted moving average (EWMA), thereby enabling the eNB to perform scheduling tasks with greater accuracy. We also present an AAG-2 (Allocate As Granted-version 2) scheme capable of supporting the QoS for GBR bearers, while enabling the efficient allocation of RBs to non-GBR bearers. The existence of parties seeking superior levels of service makes it necessary for telecommunications operators to provide options with regard to QoS. This study proposes a revision of the AAG-2 scheme referred to as AAG-D to accommodate such demands. Simulation results demonstrate the efficacy of the new scheme in achieving goals related to throughput and average packet delay.