Seamless handover in terrestrial radio access networks: a case study

Next-generation networks will overlay heterogeneous networking technologies. In order to enable seamless communications in such an environment, providing support for efficient handover between the various access technologies will play a crucial role. The present article provides a quantitative analysis of it Mobile IPv4-based WLAN-GPRS handover prototype, identifies a number of side effects related to the link layer and routing mechanisms, and presents the impact of handover on UDP and TCP data traffic as well as on Mobile IP signaling itself.     

HISNs: Distributed gateways for application-level integration of heterogeneous wireless networks

Integration of different kinds of wireless networks to provide people seamless and continuous network access services is a major issue in the B3G network. In this paper, we propose and implement a novel Heterogeneous network Integration Support Node design (HISN) and a distributed HISN network architecture for the integration of heterogeneous networks, under which the Session Mobility, Personal Mobility, and Terminal Mobility for mobile users can be maintained through the Session Management mechanism. Thus, the HISN node can serve as an agent for the user to access Internet services independent of underlying communication infrastructure. Our design is transparent to the bearer networks and the deployment of the HISN network does not need to involve the operators of the heterogeneous wireless networks. This paper is an extension of the work that won the championship of the Mobile Hero contest sponsored by Industrial Development Bureau of Ministry of Economic Affairs, Taiwan, R.O.C., and was awarded USD 30,000. The work of Lin, Chang and Cheng was supported in part by the National Science Council (NSC), R.O.C, under the contract number NSC94-2213-E-002-083 and NSC94-2213-E-002-090, and NSC 94-2627-E-002-001, Ministry of Economic Affairs (MOEA), R.O.C., under contract number 93-EC-17-A-05-S1-0017, the Computer and Communications Researches Labs/Industrial Technology Research Institute (CCL/ITRL), Chunghwa Telecom Labs, Telcordia Applied Research Center, Taiwan Network Information Center (TWNIC), and Microsoft Corporation, Taiwan. The work of Fang was supported in part by the US National Science Foundation Faculty Early Career Development Award under grant ANI-0093241 and US National Science Foundation under grant DBI-0529012. Phone Lin (M’02-SM’06) received his BSCSIE degree and Ph.D. degree from National Chiao Tung University, Taiwan, R.O.C. in 1996 and 2001, respectively. From August 2001 to July 2004, he was an Assistant Professor in Department of Computer Science and Information Engineering (CSIE), National Taiwan University, R.O.C. Since August 2004, he has been an Associate Professor in Department of CSIE and Graduate Institute of Networking and Multimedia, National Taiwan University, R.O.C. His current research interests include personal communications services, wireless Internet, and performance modeling. Dr. Lin is an Associate Editor for IEEE Transactions on Vehicular Technology, a Guest Editor for IEEE Wireless Communications special issue on Mobility and Resource Management, and a Guest Editor for ACM/Springer MONET special issue on Wireless Broad Access. He is also an Associate Editorial Member for the WCMC Journal. P. Lin’s email and website addresses are plin@csie.ntu.edu.tw and http://www.csie.ntu.edu.tw/∼plin, respectively. Huan-Ming Chang received the BSCSIE degree and Master CSIE degree from National Taiwan University, R.O.C. in 2003 and 2005, respectively. His current research interest includes wireless Internet. H.-M. Chang’s email address is r91114@csie.ntu.edu.tw. Yuguang Fang received a Ph.D. degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D. degree in Electrical Engineering from Boston University in May 1997. From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering at University of Florida where he got the early promotion to Associate Professor with tenure in August 2003 and to Full Professor in August 2005. He has published over 180 papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications and Networking Conference (WCNC’2000). Shin-Ming Cheng received the BSCSIE degree in 2000 from National Taiwan University, Taiwan, R.O.C., where he is currently working toward the Ph.D. degree in the Department of Computer Science and Information Engineering, National Taiwan University. His current research interests include mobile computing, personal communications services, and wireless Internet. S.-M. Cheng’s email and website addresses are shimi@pcs.csie.ntu.edu.tw and http://www.pcs.csie.ntu.edu.tw/∼shimi, respectively.     

SHARE: seamless handover architecture for 3G-WLAN roaming environment

For the transition from 3G communication systems to 4G communication systems, 3G-WLAN interworking systems can be a reference model for 4G communication systems. In this paper, we identify challenging problems in 3G-WLAN interworking systems and propose a loosely coupled architecture called SHARE. In SHARE, each WLAN hotspot access point (AP) is equipped with a 3G radio transmission module to generate radio signals for control channels of 3G networks in addition to a WLAN radio module. Consequently, base stations of the 3G networks share their control channels with hotspot APs. By monitoring these channels, mobile nodes can easily detect available WLAN hotspots without probe delay for handovers.

An intelligent agent-based scheme for vertical handover management across heterogeneous networks

Advances in technology have enabled a proliferation of mobile devices and a broad spectrum of novel and outbreaking solutions for new applications and services. The increasing demand for all time and everywhere services requires the network operators to integrate different kinds of wireless and cellular networks. To enable this integration, it is important that users can roam freely across networks. As different technologies are involved in the current infrastructure, the problem of vertical handover needs to be addressed. To cope with the problem of seamless connectivity, several solutions have been presented. But most of them either lack intelligence or are not adaptable for reducing the packet loss and delay involved in the handover procedure. An intelligent technique is needed in order to perform the service continuity in the heterogeneous environment. This paper presents a cooperative agent based approach for the vertical handover using a knowledge plane. We propose to introduce the agents in the mobile nodes and access points to collect the necessary information from the environment. Based on this information, agents take a handover decision. A selection function is also introduced in this work which helps in choosing a best network from the available ones for handover. Finally, the proposed approach is validated with the help of simulations.     

LTE连接状态下E-UTRAN内切换研究

移动性管理功能的作用是为了持续追踪UE的当前位置并提供持续的接入服务。该功能分为两大类：空闲状态的移动性管理和连接状态的移动性管理,在移动通信系统中有非常重要的作用。本课题的主要内容为LTE系统内连接状态下的移动性管理功能,重点为E-UTRAN内切换。     

Signal threshold adaptation for vertical handoff in heterogeneous wireless networks

The convergence of heterogeneous wireless access technologies has been envisioned to characterize the next generation wireless networks. In such converged systems, the seamless and efficient handoff between different access technologies (vertical handoff) is essential and remains a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics results in handoff asymmetry that differs from the traditional intra-network handoff (horizontal handoff) problem. In the case where one network is preferred, the vertical handoff decision should be carefully executed, based on the wireless channel state, network layer characteristics, as well as application requirements. In this paper, we study the performance of vertical handoff using the integration of 3G cellular and wireless local area networks as an example. In particular, we investigate the effect of an application-based signal strength threshold on an adaptive preferred-network lifetime-based handoff strategy, in terms of the signalling load, available bandwidth, and packet delay for an inter-network roaming mobile. We present an analytical framework to evaluate the converged system performance, which is validated by computer simulation. We show how the proposed analytical model can be used to provide design guidelines for the optimization of vertical handoff in the next generation integrated wireless networks. This article is the extended version of a paper presented in IFIP Networking 2005 Ahmed H. Zahran is a Ph.D. candidate at the Department of Electrical and Computer Engineering, University of Toronto. He received both his M.Sc. and B.Sc. in Electrical Engineering from Electronics and Electrical Communication Department in the Faculty of Engineering, Cairo University in 2002 and 2000 respectively, where he was holding teaching and research positions. Since September 2003, he has been working as a research assistant in the Department of Electrical and Computer Engineering, University of Toronto under the supervision of Professor Ben Liang. His research interest is wireless communication and networking with an emphasis on the design and analysis of networking protocols and algorithms. Ben Liang received honors simultaneous B.Sc. (valedictorian) and M.Sc. degrees in Electrical Engineering from Polytechnic University in Brooklyn, New York, in 1997 and the PhD degree in Electrical Engineering with Computer Science minor from Cornell University in Ithaca, New York, in 2001. In the 2001–2002 academic year, he was a visiting lecturer and post-doctoral research associate at Cornell University. He joined the Department of Electrical and Computer Engineering at the University of Toronto as an Assistant Professor in 2002. His current research interests are in the areas of mobile networking and wireless multimedia systems. He is a member of Tau Beta Pi, IEEE, and ACM and serves on the organization and technical program committees of a number of major conferences each year. Aladdin Saleh earned his Ph.D. degree in Electrical Engineering from London University, England. Since March 1998, Dr. Saleh has been working in the Wireless Technology Department of Bell Canada, the largest service provider of wireless, wire-line, and Internet in Canada. He worked as a senior application architect in the wireless data group working on several projects among them the wireless application protocol (WAP) and the location-based services. Later, he led the work on several key projects in the broadband wireless network access planning group including planning of the IEEE 802.16/ Wimax, the IEEE 802.11/ WiFi, and the integration of these technologies with the 3G cellular network including Mobile IP (MIP) deployment. Dr. Saleh also holds the position of Adjunct Full Professor at the Department of Electrical and Computer Engineering of Waterloo University, Canada since January 2004. He is currently conducting several joint research projects with the University of Waterloo and the University of Toronto on IEEE 802.16-Wimax, MIMO technology, interworking of IEEE 802.11 WLAN and 3G cellular networks, and next generation wireless networks. Prior to joining Bell Canada, Dr. Saleh worked as a faculty member at different universities and was Dean and Chairman of Department for several years. Dr. Saleh is a Fellow of IEE and a Senior Member of IEEE.     

基于媒体独立切换并提供QoS保证的跨UMTS和WiMAX无线异构网络的网络切换方案

The rapid growth and innovation of the various mobile communication technologies have caused a change in the paradigm of internet access. Wireless technologies such as WiMAX, WiFi and UMTS/LTE networks have shown great potential in dominating the wireless access markets. The existence of various access technologies requires a means for seamless internetworking to provide anywhere, anytime services without interruption in the ongoing session, especially in multimedia applications with rigid Quality of Services (QoS) requirements. The IEEE 802.21 Media Independent Handover (MIH) working group was formed to develop a set of mechanisms under a standard framework with the capability to support migration of mobile users across heterogeneous networks. Therefore, the implementation of handover is extremely important in the heterogeneous network environment. In order to guarantee various QoS requirements during handover execution especially in multimedia applications, in this paper we propose a novel MIH-based capacity estimation algorithm to execute handover with QoS provision supporting both horizontal and vertical handovers across UMTS and WiMAX networks. Simulation shows that the proposed mechanism achieves lower call dropping rate (highest approximate 3% ) and higher system throughput (average 92% ) than the basic handover method does.     

Robust resource allocation for NOMA-assisted heterogeneous networks

As a promising technology to improve spectrum efficiency and transmission coverage, Heterogeneous Network (HetNet) has attracted the attention of many scholars in recent years. Additionally, with the introduction of the Non-Orthogonal Multiple Access (NOMA) technology, the NOMA-assisted HetNet cannot only improve the system capacity but also allow more users to utilize the same frequency band resource, which makes the NOMA-assisted HetNet a hot topic. However, traditional resource allocation schemes assume that base stations can exactly estimate direct link gains and cross-tier link gains, which is impractical for practical HetNets due to the impact of channel delays and random perturbation. To further improve energy utilization and system robustness, in this paper, we investigate a robust resource allocation problem to maximize the total Energy Efficiency (EE) of Small-Cell Users (SCUs) in NOMA-assisted HetNets under imperfect channel state information. By considering bounded channel uncertainties, the robust resource optimization problem is formulated as a mixed-integer and nonlinear programming problem under the constraints of the cross-tier interference power of macrocell users, the maximum transmit power of small base station, the Resource Block (RB) assignment, and the quality of service requirement of each SCU. The original problem is converted into an equivalent convex optimization problem by using Dinkelbach's method and the successive convex approximation method. A robust Dinkelbach-based iteration algorithm is designed by jointly optimizing the transmit power and the RB allocation. Simulation results verify that the proposed algorithm has better EE and robustness than the existing algorithms.     

Optimal resource allocation solutions for heterogeneous cognitive radio networks

Cognitive radio networks (CRN) are currently gaining immense recognition as the most-likely next-generation wireless communication paradigm, because of their enticing promise of mitigating the spectrum scarcity and/or underutilisation challenge. Indisputably, for this promise to ever materialise, CRN must of necessity devise appropriate mechanisms to judiciously allocate their rather scarce or limited resources (spectrum and others) among their numerous users. ‘Resource allocation (RA) in CRN', which essentially describes mechanisms that can effectively and optimally carry out such allocation, so as to achieve the utmost for the network, has therefore recently become an important research focus. However, in most research works on RA in CRN, a highly significant factor that describes a more realistic and practical consideration of CRN has been ignored (or only partially explored), i.e., the aspect of the heterogeneity of CRN. To address this important aspect, in this paper, RA models that incorporate the most essential concepts of heterogeneity, as applicable to CRN, are developed and the imports of such inclusion in the overall networking are investigated. Furthermore, to fully explore the relevance and implications of the various heterogeneous classifications to the RA formulations, weights are attached to the different classes and their effects on the network performance are studied. In solving the developed complex RA problems for heterogeneous CRN, a solution approach that examines and exploits the structure of the problem in achieving a less-complex reformulation, is extensively employed. This approach, as the results presented show, makes it possible to obtain optimal solutions to the rather difficult RA problems of heterogeneous CRN.     

Detection of mobile targets on the plane and in space using heterogeneous sensor networks

Detection of targets moving within a field of interest is a fundamental service Wireless Sensor Network (WSN) service. The WSN’s target detection performance is directly related to the placement of the sensors within the field of interest. In this paper, we address the problem of deterministic sensor deployment on the plane and in space, for the purpose of detecting mobile targets. We map the target detection problem to a line-set intersection problem and derive analytic expressions for the probability of detecting mobile targets. Compared to previous works, our mapping allows us to consider sensors with heterogeneous sensing capabilities, thus analyzing sensor networks that employ multiple sensing modalities. We show that the complexity of evaluating the target detection probability grows exponentially with the network size and, hence, derive appropriate lower and upper bounds. We also show that maximizing the lower bound on the probability for target detection on the plane and in space, is analogous to the problem of minimizing the average symbol error probability in two-dimensional and three-dimensional digital modulation schemes, respectively, over additive white Gaussian noise. These problems can be addressed using the circle packing problem for the plane, and the sphere packing problem for space. Using the analogy to digital modulation schemes, we derive sensor constellations from well known signal constellations with low average symbol error probability.

Design of an enhanced access point to optimize TCP performance in Wi-Fi hotspot networks

In the last years, the number of Wi-Fi hotspots at public venues has undergone a substantial growth, promoting the WLAN technologies as the ubiquitous solution to provide high-speed wireless connectivity in public areas. However, the adoption of a random access CSMA-based paradigm for the 802.11 MAC protocol makes difficult to ensure high throughput and a fair allocation of radio resources in 802.11-based WLANs. In this paper we evaluate extensively via simulations the interaction between the flow control mechanisms implemented at the TCP layer and the contention avoidance techniques used at the 802.11 MAC layer. We conducted our study considering initially M wireless stations performing downloads from the Internet. From our results, we observed that the TCP downlink throughput is not limited by the collision events, but by the inability of the MAC protocol to assign a higher chance of accessing the channel to the base station. We propose a simple and easy to implement modification of the base station’s behavior with the purpose of increasing the TCP throughput reducing useless MAC protocol overheads. With our scheme, the base station is allowed to transmit periodically bursts of data frames towards the mobile hosts. We design a resource allocation protocol aimed at maximizing the success probability of the uplink transmissions by dynamically adapting the burst length to the collision probability estimated by the base station. By its design, our scheme is also beneficial to achieve a fairer allocation of the channel bandwidth among the downlink and uplink flows, and among TCP and UDP flows. Simulation results confirm both the improvement in the TCP downlink throughput and the reduction of system unfairness.     

IIDWBA algorithm for integrated hybrid PON with wireless technologies for next generation broadband access networks

Optical and wireless technology integration has been proposed as one of the most promising nominees for the next-generation broadband access networks for quite some time. Integration scheme merges the high-speed and high-capacity of the optical networks with the low-cost, wide-coverage and mobility features of the wireless counterparts for the Subscriber Stations (SSs). It is also financially viable for the telecommunication service providers, particularly in the rural area where the development of optical infrastructure or expansion of the existing telecommunication solutions such as Digital Subscriber Line (DSL), Cable Modem (CM) or T-1/E-1 networks are either too costly or unreachable. In order to successfully integrate the two technologies, there are some technical concerns in terms of Architectural aspects, Physical Layer features and Media Access Control (MAC) related issues, which need to be addressed efficiently in order to provide the smooth end-to-end (e2e) integration. This paper is mainly focused upon the analysis of the key topics in MAC-related issues such as E2E wavelength/bandwidth requests and allocations over the converged scenario. It proposes an Inter-channel and Intra-channel Dynamic Wavelength/Bandwidth Allocation (IIDWBA) algorithm where the hybrid Passive Optical Network (PON) acts as a back haul technology for the wireless counterpart. The proposed algorithm works in three phases, namely, Initialisation, Intra-channel bandwidth allocations and Inter-channel bandwidth allocations and is capable of allocating wavelength/bandwidth efficiently and effectively over the converged scenario. Performance of the proposed algorithm is evaluated through conducted simulation scenarios under different simulation parameters, traffic patterns and load values. According to the captured results, IIDWBA algorithm shows a better performance when it is compared to the scenario in which it has not been employed.     

Political disagreement and ambivalence in new information environment: Exploring conditional indirect effects of partisan news use and heterogeneous discussion networks on SNSs on political participation

This study investigates the (de)mobilizing influences of political (dis)agreement in the news and in political discussion on political attitudes and participation in new information environments. Results demonstrate the mediating functions of political ambivalence in that exposure to proattitudinal news reduces ambivalence and thereby promotes political participation, whereas exposure to counter-attitudinal news increases ambivalence and thereby discourages participation. Importantly, the effect of exposure to counter-attitudinal news on ambivalence was moderated by heterogeneous discussion networks on social network sites, such that the combination of exposure to counter-attitudinal news and to heterogeneous discussion networks amplifies ambivalence additively, and thereby augments the tendency toward demobilization. These results are interpreted as suggesting that changing media contexts may lead to complex roles of news and political discussion.     

Moving toward seamless mobility: state of the art and emerging aspects in standardization bodies

The challenge to provide seamless mobility in the near future emerges as a key topic in various standardization bodies. This includes first of all the support of seamless handover between homogeneous networks. Distinct technologies—such as IEEE 802.11WLANs (Wi-Fi) and IEEE 802.16 MANs WiMAX—have recently augmented such support to existing standards to enable seamless homogeneous handover. Cellular networks, in contrast, already included this inherently from the start. Currently considerable effort goes into coupling of different radio access technologies. Therefore, the second key topic in standardization is seamless heterogeneous handovers. IEEE, IETF, as well as 3GPP consider different approaches toward architectures and protocols enabling seamless mobility management. In this work, we discuss recent and on-going standardization activities within IEEE, IETF, and 3GPP toward seamless homogeneous as well as heterogeneous mobility support.