Heterogeneous personal communications services: integration of PCSsystems

Personal communications services (PCS) are being introduced to offer ubiquitous communication. In its first phase PCS consists of a plethora of systems that address cellular, vehicular, cordless phone, and a variety of other services. The integration of these different systems is referred to as “heterogeneous PCS (HPCS)”. We describe the various PCS systems available and address in detail the issue of PCS systems integration. Key implementation issues for integrating PCS systems are defined and discussed     

A new FQPSK modem/radio architecture for PCS and mobile satellitecommunications

A newly developed constant envelope FQPSK modem/radio architecture, which employs a modified double-jump (DJ) filter in the cross-correlated FQPSK system, is proposed for personal communications systems (PCS) and mobile satellite applications. The power efficiency and spectrum efficiency of this system are investigated in a nonlinear amplified (NLA) environment. The bit error rate (BER) performance is evaluated in a noisy Rayleigh fading channel. We demonstrate that with the simplest threshold detectors (binary robust eye diagrams in I and Q channels), this system is 4-7 dB more power efficient than the US digital cellular and Japanese Handyphone standard π/4-QPSK (50%-100% more spectrally efficient than the recently adopted wireless local area network (LAN) standard GFSK and the European standard GMSK). The results indicate that the proposed DJ filtered FQPSK is a power and spectrally efficient modem/radio technique. By selecting different system parameters, this system can be optimized for a wide range of applications in PCS and mobile satellite communications     

Handoff with DSP Support: Enabling Seamless Voice Communications across Heterogeneous Telephony Systems on Dual-Mode Mobile Devices

In this paper we investigate the problem of voice communications across heterogeneous telephony systems on dual-mode (WiFi and GSM) mobile devices. Since GSM is a circuit-switched telephony system, existing solutions that are based on packet-switched network protocols cannot be used. We show in this paper that an enabling technology for seamless voice communications across circuit-switched and packet-switched telephony systems is the support of digital signal processing (DSP) techniques during handoffs. To substantiate our argument, we start with a framework based on the Session Initiation Protocol (SIP) for vertical handoffs on dual-mode mobile devices. We then identify the key obstacle in achieving seamless handoffs across circuit-switched and packet-switched systems, and explain why DSP support is necessary in this context. We propose a solution that incorporates time alignment and time scaling algorithms during handoffs for supporting seamless voice communications across heterogeneous telephony systems. We conduct testbed experiments using a GSM-WiFi dual-mode notebook and evaluate the quality of speech when the call is migrated from WiFi to GSM networks. Evaluation results show that such a cross-disciplinary solution involving signal processing and networking can effectively support seamless voice communications across heterogeneous telephony systems.     

A new cellular architecture based on an interleaved cluster concept

Personal communications services (PCSs) and future broad-band wireless systems are and will continue to be driven mainly by three challenging objectives: high-spectrum reuse efficiency, high-quality channels, and low infrastructure costs. We propose a new interleaved narrow-beam trisector cell (INBTC) architecture with a newly developed interleaved channel assignment (ICA) scheme to achieve these three objectives. Originating from the ICA scheme, we introduce the concept of interleaved cluster, within which a channel set can be assigned more than once. The INBTC architecture with interleaved clusters can enhance the performance of cellular/PCS systems from several perspectives. We demonstrate that to achieve high-spectrum efficiency, specifically in the range of reuse factors N=2-7, the INBTC system improves 3-5 dB at the 90th and 95th percentiles of signal-to-interference ratio (SIR) compared to conventional cellular systems. For a typical cellular environment, with a shadow fading standard deviation σ=8 dB and an SIR requirement of 17 dB at the 90th percentile, the INBTC system can increase system capacity by 75% over current systems. Because the INBTC architecture can utilize the base-station equipment of current cellular/PCS systems, implementing it should be simple and carry no attendant infrastructure costs. Hence, the proposed INBTC system (the cell layout plus the channel assignment scheme) has significant potential value in future cellular/PCS systems, as well as in broad-band wireless applications     

A Cross-Layer (Layer 2 + 3) Handoff Management Protocol for Next-Generation Wireless Systems

Next-generation wireless systems (NGWS) integrate different wireless networks, each of which is optimized for some specific services and coverage area to provide ubiquitous communications to the mobile users. It is an important and challenging issue to support seamless handoff management in this integrated architecture. The existing handoff management protocols are not sufficient to guarantee handoff support that is transparent to the applications in NGWS. In this work, a cross-layer (Layer 2 + 3) handoff management protocol, CHMP, is developed to support seamless intra and intersystem handoff management in NGWS. Cross-layer handoff management protocol uses mobile's speed and handoff signaling delay information to enhance the handoff performance of Mobile IP that is proposed to support mobility management in wireless IP networks. First, the handoff performance of Mobile IP is analyzed with respect to its sensitivity to the link layer (Layer 2) and network layer (Layer 3) parameters. Then, a cross-layer handoff management architecture is developed using the insights learnt from the analysis. Based on this architecture, the detailed design of CHMP is carried out. Finally, extensive simulation experiments are carried out to evaluate the performance of CHMP. The theoretical analysis and simulation results show that CHMP significantly enhances the performance of both intra and intersystem handoffs.     

ATM-based TH-SSMA network for multimedia PCS

Personal communications services (PCS) promise to provide a variety of information exchanges among users with any type of mobility, at any time, in any place, through any available device. To achieve this ambitious goal, two of the major challenges in the system design are: (i) to provide a high-speed wireless subsystem with large capacity and acceptable quality-of-service (QoS) and (ii) to design a network architecture capable of supporting multimedia traffic and various kinds of user mobility. A time-hopping spread-spectrum wireless communication system called ultra-wide bandwidth (UWB) radio is used to provide communications that are low power, high data rate, fade resistant, and relatively shadow free in a dense multipath environment. Receiver-signal processing of UWB radio is described, and performance of such communications systems, in terms of multiple-access capability, is estimated under ideal multiple-access channel conditions. A UWB-signal propagation experiment is performed using the bandwidth in excess of 1 GHz in a typical modern office building in order to characterize the UWB-signal propagation channel. The experimental results demonstrate the feasibility of the UWB radio and its robustness in a dense multipath environment. A ATM network is used as the backbone network due to its high bandwidth, fast switching capability, flexibility, and well-developed infrastructure. To minimize the impact caused by user mobility on the system performance, a hierarchical network-control architecture is postulated. A wireless virtual circuit (WVC) concept is proposed to improve the transmission efficiency and simplify the network control in the wireless subsystem. The key advantage of this network architecture and WVC concept is that the handoff can be done locally most of the time, due to the localized behavior of PCS users     

A spectrally efficient constant envelope modulation technique forPCS and mobile communications

A newly developed constant envelope FQPSK modem/radio architecture, which employs a modified double-jump (DJ) filter in the cross-correlated FQPSK system, is proposed for personal communications systems (PCS) and mobile radio applications. Power efficiency, spectrum efficiency, BER, and system capacity of this system are investigated in a non-linear amplified (NLA) Rayleigh fading environment. We demonstrate that with the simplest threshold detectors (binary robust eye diagrams in I and Q channels), this system is 4-7 dB more power efficient than the US digital cellular and Japanese Handyphone standard π/4-QPSK, 50%-100% more spectrally efficient than the European standard GMSK, and it almost double the capacity of GMSK     

Polling deregistration for unlicensed PCS

The FCC has allocated the spectrum between 1850-1910 and 1930-1990 MHz for licensed personal communications services (PCS) and the band between 1920-1930 MHz for unlicensed PCS (UPCS). This paper describes a polling deregistration protocol for a wireless access communications network which would support interoperability between licensed personal communications services (PCS) and unlicensed-PCS (UPCS). We show how the protocol can be efficiently implemented in the personal access communications system (PACS) for licensed PCS and in the PACS-Unlicensed Version B (PACS-UB). An analytical model is proposed to analyze the performance of the polling protocol. A cost function is derived, which can be used to estimate the optimal polling frequency     

SATELLITE-ENHANCED PERSONAL COMMUNICATIONS EXPERIMENTS

Users of future generation wireless information services will have diverse needs for voice, data, and potentially even video communications in a wide variety of circumstances. For users in dense, inner-city areas, low power personal communications services (PCS) technology should be ideal. Vehicular-based users travelling at high speeds will need high-power cellular technology. For users in remote or inaccessible locations, or for applications that are broadcast over a wide geographic area, a satellite technology would be the best choice. Packet data networks provide an excellent solution for users requiring occasional small messages, whereas circuit switched networks provide more economical solutions for larger messages. To provide ubiquitous personal communications service, it is necessary to capitalize on the strength of each wireless technology and network to create one seamless internetwork including both current and future wired and wireless networks. As an initial step in exploring the opportunities afforded by the merging of satellite and terrestrial networks, Bellcore and JPL conducted several experiments. These experiments utilized Bellcore's experimental personal communications system (including several messaging applications with adaptations to wireless networks), NASA's advanced communications technology satellite (ACTS), JPL's ACTS mobile terminal, and various commercial data networks (such as the wireline Internet and the RAM wireless packet data network). Looking at loss of bits, packets and higher layer blocks (over the satellite-terrestrial internetworks with mobile and stationary users under various conditions) our initial results indicate that the communication channel can vary dramatically, even within a single network. We show that these conditions necessitate powerful and adaptive protocols if we are to achieve a seamless internetworking of satellite and terrestrial networks.     

Interoperability criteria, mechanisms, and evaluation of system performance for transparently interoperating WLAN and UMTS-HSDPA networks

The main challenge in the development of future wireless communication systems is to provide users with a wide range of services across different radio access technologies through a single mobile terminal, while maintaining the minimum QoS requirements, and ideally with no limits on the coverage area, mobility or radio conditions. Thus, the need for seamless interworking between heterogeneous wireless communication systems consisting of multiple radio access technologies and overlapping networks emerges. In this article we address the main issues that arise while implementing the interoperability mechanisms between two different radio access networks, with emphasis on UMTS-HSDPA and WLAN (HIPERLAN/2). Two interoperability mechanisms are introduced and described in detail: initial user assignment (optimal network selection) and intersystem handover. Both mechanisms are activated via the optimization of a suitably defined cost function which takes into account all the appropriate system level parameters that trigger the interoperability process. Finally, we investigate the overall performance of the proposed mechanisms by means of a software simulation platform. A number of simulations have been carried out in order to demonstrate the performance enhancements achieved by the proposed mechanisms in terms of unsatisfied users, dropped handovers, and system throughput.     

A dynamic location management scheme for next-generation multitierPCS systems

Global wireless networks enable mobile users to communicate regardless of their locations. One of the most important issues is location management in a highly dynamic environment because mobile users may roam between different wireless systems, network operators, and geographical regions. A location-tracking mechanism is introduced that consists of intersystem location updates and intersystem paging. Intersystem update is implemented by using the concept of boundary location area, which is determined by a dynamic location update policy in which the velocity and the quality of service are taken into account on a per-user basis. Also, intersystem paging is based on the concept of a boundary location register, which is used to maintain the records of mobile users crossing the boundary of systems. This mechanism not only reduces location-tracking costs, but also significantly decreases call-loss rates and average-paging delays. The performance evaluation of the proposed schemes is provided to demonstrate their effectiveness in multitier personal communication systems     

Intelligent network: a key platform for PCS interworking andinteroperability

The Tl and TIA standards committees in the United States have worked jointly on the development of the first phase of personal communication services (PCS) standards, which were approved in December 1995. PCS systems based on these standards are currently under development. As these systems are deployed, the variety of wireless systems will grow, making interworking and interoperability a key challenge. This article provides an overview of PCS standards and explores how the different types of wireless systems (PCS and cellular) will utilize the capabilities of the intelligent network to provide seamless roaming     

Universal broadband mobility target for post-TINA infrastructure:toward the fourth generation

Future universal broadband mobile services present a challenge for telecommunications architectures, control, and management. The focus of the future mobile (fourth) generation vision is turned from capacity to services, from radio to network-wide issues. New types of applications will evolve that should be supported by an adequate programmable intelligent telecommunications infrastructure. A convergence between telecom and datacom networks will happen based on the communications middleware concept, which will provide universal secure connectivity between mobile users and their applications. Actual specifications of TINA-C do not address all such necessary issues. There is a need for technology evolution, enhancement, and integration to meet these new requirements at different levels. The author the concept of the universal broadband mobile telecommunications systems (UBMTS, or simply UBM) described as fourth-generation mobile systems. The UBMTS objective is both to extend mobile user access to the range of broadband services that will exist for broadband integrated services digital network (B-ISDN) users, and to extend the customization of new services related to personal communications systems (PCS) users     

A portable multimedia terminal

A personal communications system (PCS) that centers on integration of services to provide access to data and communications using a specialized, wireless multimedia terminal is described. The possible applications and support systems for such a terminal are outlined. Several of the major design issues behind portable multimedia terminals, including spectrally efficient picocellular networking, low-power digital design, video data compression, and integrated wireless RF transceivers, are discussed. It is argued that optimizing performance in each of these areas is crucial in meeting the performance requirements of the overall system and providing a small, lightweight terminal for personal communications     

一种基于SIP与移动IPV6的异构网络切换方法

随着移动通信技术的发展,诞生了各种可供接入的网络,如GPRS,WALN等.它们传输速率和原理各不相同,不同异质接入网络之间的切换已经成为对下一代无线网络的一个基本要求.本文介绍了一种新的切换机制,首先分别介绍了SIP技术与移动IPv6技术的原理,然后结合SIP与移动IPv6技术提出一种全新的无缝切换机制,最后总结并提出了有待进一步研究的相关问题.     

A seamless soft handover management scheme in NGEO satellite networks

Satellite networks can provide extensive geographic coverage to diverse user population, but handovers of active communications should be controlled considering the satellites' high speed. Mobile IP and many other handover algorithms have been proposed for terrestrial wireless networks. However, the satellite network exhibits several unique features compared with the terrestrial wireless networks, such as the long delay. This paper proposes a seamless soft handover scheme (S2H) for satellite networks. S2H designs an identity locator split addressing to solve the multihoming problem and applies the network coding scheme during handover. This manner is able to reduce the interference opportunity, save transmissions, and achieve low handover delay, short queue length, and high throughput. Relying on the simulation results, S2H is able to achieve better performance compared with the proposed handover algorithms in the satellite environment when there are multiple traffic flows. Copyright © 2013 John Wiley & Sons, Ltd.     

A Proxy MIPv6 Handover Scheme for Vehicular Ad-hoc Networks

With the rapid growth in the number of mobile devices, such as cellular phones, PDAs and laptops, the need for seamless and ubiquitous Internet connectivity is tangible. Vehicular ad-hoc network (VANET) is a rapidly developing technology, which makes vehicle-to-vehicle and vehicle-to-infrastructure communication feasible. However, when a vehicle travels from one point of attachment to another, handoff delays and provision of seamless connectivity are considered as important issues. Ubiquitous and integrated Internet connectivity can be achieved if on road moving vehicles are connected. However, when vehicle density is small and/or vehicle velocities are different, end users may suffer from a high level of connection failure. IP mobility protocols are designed by Internet Engineering Task Force to provide acceptable levels of continuous Internet connectivity, maintaining mobile node communications as they travel amongst points of attachments. However, the current IP mobility approaches applied on VANET did not resolve the connection failure issues efficiently. Therefore, in this paper a new effective solution is proposed in order to eliminate the large amount of handover latency and eventually high packet loss ratio.     

A framework for seamless roaming across cellular and wireless local area networks

In the future, wireless and mobile users will have increased demands for seamless roaming across different types of wireless networks, quality of service guarantees, and support for a variety of services. This awareness has led to research activities directed toward intersystem and global roaming, and can be noticed in numerous products like multimode handsets, interworking gateways, and ongoing standards and research work on intersystem roaming. The authors of this article proposed a global mobility management framework to support seamless roaming across heterogeneous wireless networks. In this article we provide details on the use of the framework to support roaming across cellular and wireless local area networks. Highlights of the framework include a robust architecture for mobility management for varying user mobility spans, provisioning for QoS mapping, intersystem message translation, and mechanisms in the WLAN to support user-subscribed services. Performance aspects related to handoff delays, data redirection, and processing overheads are presented and discussed. Performance comparison of intersystem roaming between cellular and WLAN with and without the framework is presented.     

Analysis and design of a frequency-hopped spread-spectrumtransceiver for wireless personal communications

Personal communications services (PCS) require low-power radio technologies. One such transceiver architecture employing frequency-hopped spread-spectrum techniques is presented. System features such as antenna diversity with equal-gain combining and sequential hop combining are incorporated into the transceiver design to achieve robust wireless digital data transmission over fading channels. A direct-conversion architecture from radio frequency (RF) to baseband reduces the overall power consumption by eliminating intermediate frequency (IF) components. High-rate frequency hopping with frequency-shift keying (FSK) modulation is implemented using a direct digital frequency synthesis technique. A multiplierless correlation FSK detector, suitable for direct-conversion receivers, has been designed for quadrature noncoherent detection. Robust acquisition algorithms based on energy detection and pattern matching and tracking architectures using digital phase-locked loops are also described for system synchronization. The proposed transceiver is well-suited for low-power PCS applications and other portable wireless communications