Design,Implementation and Evaluation of Programmable Handoff in Mobile Networks

We describe the design, implementation and evaluation of a programmable architecture for profiling, composing and deploying handoff services. We argue that future wireless access networks should be built on a foundation of open programmable networking allowing for the dynamic deployment of new mobile and wireless services. Customizing handoff control and mobility management in this manner calls for advances in software and networking technologies in order to respond to specific radio, mobility and service quality requirements of future wireless Internet service providers. Two new handoff services are deployed using programmable mobile networking techniques. First, we describe a multi-handoff access network service, which is capable of simultaneously supporting multiple styles of handoff control over the same physical wireless infrastructure. Second, we discuss a reflective handoff service, which allows programmable mobile devices to freely roam between heterogeneous wireless access networks that support different signaling systems. Evaluation results indicate that programmable handoff architectures are capable of scaling to support a large number of mobile devices while achieving similar performance to that of native signaling systems.     

Editorial

Future integrated microsystems will benefit significantlyfrom progress in the VLSI field. Two key elements will boostthe implementation of new micro-integrated architectures: progressin batch-manufactured silicon sensors and the introduction ofnew circuit techniques for designing interface circuits. Thesetwo factors will be essential in favoring the transition fromthe present research driven speculations to customer drivenactivities. This paper discusses the key issues in realizingmicrosensors and the most suitable circuit techniques for interfacingand processing their output signals. A number of examples ofintegrated structures will illustrate present problems and possiblesolutions.     

SMART — improving customer service

The quality and consistency of customer service offered by telecommunications providers is now a key differentiator in the residential market-place. BT has introduced the SMART customer handling system to provide competitive advantage through worldclass levels of customer service. A large-scale, three-tier client/server system, SMART exploits the existing functionality, data and security mechanisms of an established mainframe system and adds ease-of-use, reduced error rates and a focus on service and selling. The development and deployment experiences of the SMART programme provide lessons in the delivery of large-scale distributed systems in a business-critical environment. The key issues of security, performance, resilience and operability are discussed and the solutions implemented for SMART are presented.     

The discrete Einstein relation

In this paper the connection between massM, resistance and commute time for random walks on graphs is further explored, and the relation=2M · is proved. An extension of the result is made to multigraphs, which are an extension of the graph concept where a black box is treated like an edge.     

BT Middleware — software as infrastructure

BT Middleware has been in production use since 1987. Every working day a user population of 60 000 people execute 25 million transactions on systems that generate in excess of 70% of BTs revenues. BT Middleware is installed on 32 production mainframe instances.BT Middleware provides both a development and run-time environment for applications that is controlled and manageable. Application standards can be enforced providing reuse of common code as well as common look and feel user interfaces. The use of BT Middleware has allowed the rapid implementation of leading edge solutions to pressing business requirements and Middleware is evolving to allow BTs operational support systems (OSS) to participate seamlessly in complex distributed architectures.The future for BTs OSS lies in their ability to integrate with new applications developed on open systems platforms. BT Middleware has been evolving to provide the required interconnection capabilities and now supports numerous batch and on-line interfaces via strategic infrastructure products. This paper describes the major Middleware infrastructure components developed and supported by BTs London Software Engineering Centre that allow the companys huge investment in OSS to be exploited in todays environment.     

The Problem with Disruption

Back in January 1995 Clayton Christensen and Joseph Bower wrote an article, Disruptive Technologies: catching the wave, in the Harvard Business Review, in which they argued: No matter the industry, a corporation consists of business units with finite life spans: the technological and market bases of any business will eventually disappear. Good businesses will often be adept at managing a process of incremental improvement, but this kind of incremental change, what they call sustaining technologies, is not the focus of this paper but rather disruptive technologies, which change the rules and leave established businesses with nowhere to go.     

The Supply Chain

One of the most visible examples of ubiquitous computing poised for implementation can be found in the retail industry. Radio frequency identification (RFID) tags are being billed as the replacement for barcoding, the all-pervasive technology which has underpinned supply chains for the past 35 years. The standards allow for up to thirty trillion, trillion, trillion unique addresses, and the ultimate goal is to create an Internet of things in which everyday physical items are networked together. Concerted research effort over the past five years has developed the technology and reduced cost to a point where deployment is now possible. However, the recent heated debate centred on spy chips has highlighted the fact that one person's ubiquitous computing is another person's Big Brother state.     

Quality Determination for Gate Delay Fault Tests Considering Three-State Elements

Most industrial digital circuits contain three-state elements besides pure logic gates. This paper presents a gate delay fault simulator for combinational circuits that can handle three-state elements like bus drivers, transmission gates and pulled busses. The well known delay faults--slow-to-rise and slow-to-fall--are considered as well as delayed transitions from isolating signal state high impedance to binary states 0 and 1 and vice versa. The presented parallel delay fault simulator distinguishes between non-robust, robust and hazard free tests and determines the quality of a test. Experimental results for ISCAS85/89 benchmark circuits are presented as well as results for industrial circuits containing three-state elements.     

Strategic Network Topology and a Capacity Planning Tool-Kit for Core Transmission Systems

This paper describes a state-of-the-art network planning tool-kit for core transmission systems. The tool-kit has been used extensively within the BT Group over the past 5 years to provide a forward-looking view of the capacity requirements based on a rolling two-year forecast for the BT core transmission narrowband and broadband networks. The tool-kit also has the capability to perform retrospective design as well as evolve the design of new networks — the only constraint being the physical infrastructure, i.e. ducts.The tool-kit provides the capability to audit designs and configuration data proposed by a network supplier. It has an in-built routing engine as well as state-of-the-art optimisation algorithms that have been applied to SDH and ATM, as well as optical WDM-based networks.Application of this functionality has had an inpact on key strategic decisions to the value of around a £15–20M saving within the BT Group over the past two years alone.     

Year 2000 — a Sytems Integration challenge

BT, along with virtually every other IT-dependent business worldwide, is tackling a problem which is quite unique and if not corrected could be disastrous. The problem, sometimes known as the Year 2000 bug or millennium time bomb, has been caused by the use of two digits to represent the year in the majority of our systems and applications. The problem is technically not difficult to fix but the volume of changes occurring, and the need to potentially test every system to ensure that it is year 2000 proof, presents unique and challenging difficulties for integration and testing. Why this is the case, what problems need to be addressed, and an overview of some of the proposed integration and test strategies to tackle these problems, is the subject of this paper.     

Current Operational Amplifier (COA): CMOS Realization and Active Compensation

A methodology for analysis and synthesis of lowpass sigma-delta () converters is presented in this paper. This method permits the synthesis of modulators employing continuous-time filters from discrete-time topologies. The analysis method is based on the discretization of a continuous-time model and using a discrete simulator, which is more efficient than an analog simulator. In our analysis approach, the influence of the sample and hold block and non-idealities of the feedback DAC can be systematically modeled by discrete-time systems. Finally, a realistic design of a second-order modulator with a compensation of the non-ideal behavior of the DAC is given. Moreover, simulation results show a good agreement with the theoretical predictions.     

Corporate multimedia communications

IP-based communications technology will enable people to work in a virtual way and from anywhere in the world. This is already true for data services and applications where IP has become the universal networking technology. Although voice over IP is still a relatively new technology, it has laid the path for new and innovative voice and multimedia communications. This paper looks at new and emerging technology that will tempt business and corporate organisations to adopt IP as a single communications infrastructure for both data and real-time communications.     

Performance Monitoring for In-life Capacity Management

The key to providing a meaningful management view of the performance of complex systems lies in having a co-ordinated process for data collection, analysis and presentation. TeleMarketing Services, such as the Freefone service, provide a good example. Managers of diverse, remote subsystems receive summarised performance and customer service information, mostly in the form of simple graphs, in exchange for providing reliable data. The aim is to bring together a structured view of all the components, including a red-amber-green status table, for use by senior customer-facing staff. Generally, the analyses focus on capacity, forecast and measurement, covering a flexible range of parameters. Managers then have an early view of service degradation, potential capacity exhaustion, workload imbalance and resource wastage, enabling timely remedial action, fault clearance and system enhancements.     

Firewalling the Net

To connect any stand-alone enterprise network to the Internet in a safe and secure manner, it is necessary to erect a firewall at the interface between the internal and external networks. We review the current state of firewall technology and describe the principles behind the solutions that are being adopted by BT. We also describe how companies are presently utilising the bandwidth of the Internet to extend their internal intranets using cryptographic techniques and indicate some of the directions in which firewall research will be going in the next few years.     

Floor acquisition multiple access (FAMA) in single‐channel wireless networks

The FAMANCS protocol is introduced for wireless LANs and adhoc networks that are based on a single channel and asynchronous transmissions (i.e., no time slotting). FAMANCS (for floor acquisition multiple access with nonpersistent carrier sensing) guarantees that a single sender is able to send data packets free of collisions to a given receiver at any given time. FAMANCS is based on a threeway handshake between sender and receiver in which the sender uses nonpersistent carrier sensing to transmit a requesttosend (RTS) and the receiver sends a cleartosend (CTS) that lasts much longer than the RTS to serve as a busy tone that forces all hidden nodes to back off long enough to allow a collisionfree data packet to arrive at the receiver. It is shown that carrier sensing is needed to support collisionfree transmissions in the presence of hidden terminals when nodes transmit RTSs asynchronously. The throughput of FAMANCS is analyzed for singlechannel networks with and without hidden terminals; the analysis shows that FAMANCS performs better than ALOHA, CSMA, and all prior proposals based on collision avoidance dialogues (e.g., MACA, MACAW, and IEEE 802.11 DFWMAC) in the presence of hidden terminals. Simulation experiments are used to confirm the analytical results.     

Detection of Defects Using Fault Model Oriented Test Sequences

This paper analyzes the possibilities and limitations of defect detection using fault model oriented test sequences. The analysis is conducted through the example of a short defect considering the static voltage test technique. Firstly, the problem of defect excitation and effect propagation is studied. It is shown that the effect can be either a defective effect or a defect-free effect depending on the value of unpredictable parameters. The concept of Analog Detectability Interval (ADI) is used to represent the range of the unpredictable parameters creating a defective effect. It is demonstrated that the ADIs are pattern dependent. New concepts (Global ADI, Covered ADI) are then proposed to optimize the defect detection taking into account the unpredictable parameters. Finally, the ability of a fault oriented test sequence to detect defect is discussed. In particular, it is shown that the test sequence generated to target the stuck-at faults can reasonably guarantee short defect detection till a limit given by the Analog Detectability Intervals.     

High Dynamic Range Design for ΣΔM with Wide Input Ranges

A new design algorithm is introduced to improve the input ranges of Sigma-Delta Modulation (M). Modified digital error correction techniques are proposed and employed to carry out the wide range DAC of a modulator. This design algorithm includes the advantages from both single-bit M and multi-bit M. This paper utilizes a second order lowpass modulator as an explanatory example to demonstrate our design process as well as the performance improvement. The analytical results from a quasilinear model are described to offer a theoretical explanation of the system performance. This algorithm can also be applied to bandpass and MASH architectures.     

A scalable wireless virtual LAN

This paper presents a Wireless Virtual Local Area Network (WVLAN) to support mobility in IPoverATM local area networks. Mobility is handled by a joint ATMlayer handoff for connection rerouting and MAClayer handoff for location tracking, such that the effects of mobility are localized and transparent to the higherlayer protocols. Different functions, such as Address Resolution Protocol (ARP), mobile location, and ATM connection admission are combined to reduce protocol overhead and frontend delay for connectionless packet transmission in connectionoriented ATM networks. The proposed WVLAN, through the use of ATM technology, provides a scalable wireless virtual LAN solution for IP mobile hosts.     

CBC MACs for Arbitrary-Length Messages: The Three-Key Constructions

We suggest some simple variants of the CBC MAC that enable the efficient authentication of arbitrary-length messages. Our constructions use three keys, K1, K2, K3, to avoid unnecessary padding and MAC any message M {0,1}* using max{1, |M|/n} applications of the underlying n-bit block cipher. Our favorite construction, XCBC, works like this: if |M| is a positive multiple of n then XOR the n-bit key K2 with the last block of M and compute the CBC MAC keyed with K1; otherwise, extend Ms length to the next multiple of n by appending minimal 10 padding ( 0), XOR the n-bit key K3 with the last block of the padded message, and compute the CBC MAC keyed with K1. We prove the security of this and other constructions, giving concrete bounds on an adversarys inability to forge in terms of his inability to distinguish the block cipher from a random permutation. Our analysis exploits new ideas which simplify proofs compared with prior work.     

A service system for BT‘s major customers

Customer service excellence is regarded as one of the key differentiators of BTs product and service protfolio. This paper discusses, from a technical perspective, the major customer service system (MCSS), and how it is helping to achieve excellent customer service for BTs global and major customers.