Enjie Liu

Access methods to WiMAX femtocells: A downlink system-level case study

Over the last two years, GSM and UMTS femtocell access points have been proposed as a solution to the poor indoor coverage problem experienced in certain areas. Research on these devices has shown that femtocells will not only increase indoor system coverage, but also system capacity. Femtocells will allow new services and business models to be offered to indoor users. Almost parallely, the WiMAX standard has emerged as a potential candidate technology for the future wireless networks. WiMAX femtocells are currently under development and will therefore play an important role in the world of indoor broadband wireless access. However, several aspects of this new technology, such as the access method and interference avoidance techniques play a crucial role in the amount of interference caused to co-channel deployed macrocells. This paper provides a framework for the study of WiMAX macro-femtocell hybrid scenarios. An in-depth description of the necessary radio coverage prediction and system-level simulation for this kind of scenarios is introduced. Simulations and numerical results for two different types of access methods (public and private) in the downlink are also presented.

Vehicular ad hoc networks (VANETs): Current state, challenges, potentials and way forward

Recent advances in wireless communication technologies and auto-mobile industry have triggered a significant research interest in the field of VANETs over the past few years. VANET consists of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications supported by wireless access technologies such as IEEE 802.11p. This innovation in wireless communication has been envisaged to improve road safety and motor traffic efficiency in near future through the development of Intelligent Transport Systems (ITS). Hence, government, auto-mobile industries and academia are heavily partnering through several ongoing research projects to establish standards for VANETs. The typical set of VANET application areas, such as vehicle collision warning and traffic information dissemination have made VANET an interested field of wireless communication. This paper provides an overview on current research state, challenges, potentials of VANETs as well the way forward to achieving the long awaited ITS.

Clinically driven design of multi-scale cancer models: the ContraCancrum project paradigm

The challenge of modelling cancer presents a major opportunity to improve our ability to reduce mortality from malignant neoplasms, improve treatments and meet the demands associated with the individualization of care needs. This is the central motivation behind the ContraCancrum project. By developing integrated multi-scale cancer models, ContraCancrum is expected to contribute to the advancement of in silico oncology through the optimization of cancer treatment in the patient-individualized context by simulating the response to various therapeutic regimens. The aim of the present paper is to describe a novel paradigm for designing clinically driven multi-scale cancer modelling by bringing together basic science and information technology modules. In addition, the integration of the multi-scale tumour modelling components has led to novel concepts of personalized clinical decision support in the context of predictive oncology, as is also discussed in the paper. Since clinical adaptation is an inelastic prerequisite, a long-term clinical adaptation procedure of the models has been initiated for two tumour types, namely non-small cell lung cancer and glioblastoma multiforme; its current status is briefly summarized.

Lifelogging Data Validation Model for Internet of Things Enabled Personalized Healthcare

Internet of Things (IoT) technology offers opportunities to monitor lifelogging data by a variety of assets, like wearable sensors, mobile apps, etc. But due to heterogeneity of connected devices and diverse human life patterns in an IoT environment, lifelogging personal data contains huge uncertainty and are hardly used for healthcare studies. Effective validation of lifelogging personal data for longitudinal health assessment is demanded. In this paper, lifelogging physical activity (LPA) is taken as a target to explore how to improve the validity of lifelogging data in an IoT enabled healthcare system. A rule-based adaptive LPA validation (LPAV) model, LPAV-IoT, is proposed for eliminating irregular uncertainties (IUs) and estimating data reliability in IoT healthcare environments. A methodology specifying four layers and three modules in LPAV-IoT is presented for analyzing key factors impacting validity of LPA. A series of validation rules are designed with uncertainty threshold parameters and reliability indicators and evaluated through experimental investigations. Following LPAV-IoT, a case study on a personalized healthcare platform myhealthavatar connecting three state-of-the-art wearable devices and mobile apps are carried out. The results reflect that the rules provided by LPAV-IoT enable efficiently filtering at least 75% of IU and adaptively indicating the reliability of LPA data on certain condition of IoT environments.

Clinically Oriented Translational Cancer Multilevel Modeling: The ContraCancrum Project

The ContraCancrum project aims at developing a composite multilevel platform for simulating malignant tumor development and tumor and normal tissue response to therapeutic modalities and treatment schedules. The project aims at having an impact primarily in (a) the better under-standing of the natural phenomenon of cancer at different levels of biocomplexity and most importantly (b) the disease treatment optimization procedure in the patient’s individualized context by simulating the response to various therapeutic regimens. Fundamental biological mechanisms involved in tumor development and tumor and normal tissue treatment response such as metabolism, cell cycle, tissue mechanics, cell survival following treatment etc. are modeled also addressing stem cells in the context of both tumor and normal tissue behavior. The simulators exploit several discrete and continuous mathematics methods such as cellular automata, the generic Monte Carlo technique, finite elements, differential equations, novel dedicated algorithms etc. The predictions of the simulators rely on the imaging, histopathological, molecular and clinical data of the patient. ContraCancrum deploys two important clinical studies for validating the models, one on lung cancer and one on gliomas. The crucial validation work is based on comparing the multi-level therapy simulation predictions with multi-level patient data, acquired before and after therapy. ContraCancrum aims to pave the way for translating clinically validated multilevel cancer models into clinical practice.

Adaptive DRX Scheme for beyond 3G Mobile Handsets

Beyond 3G mobile networks will be data service centric. It is anticipated that UE will stay in the Connected State relatively long while supporting data services, so efficient power saving mechanisms for the Connected State are more significant in order to prolong the active time of a handset. Discontinuous Reception (DRX) is a dominant approach for power saving in the Idle State and the Connected State. In this paper, a novel Counter-Driven Adaptive DRX (CDA-DRX) scheme is proposed and analyzed. It intends to present a generic and easy-to-implement adaptive DRX scheme that keeps up with the change of user activity level. This autonomous and adaptive power saving scheme distinguishes itself from all other researches surveyed so far from literature by minimizing signaling overhead and easy balancing between packet delivery latency and power saving performance according to QoS requirement of established data services.

A Two-Stage RESTful Web Service Composition Method Based on Linear Logic

RESTful web services, which are declarative, light-weight and easy-to-access, have attracted increasing interest from industry and are already widely used for exposing their services on the Internet. However, the formalism of RESTful web services, especially in terms of automatic composition, is still under explored compared to the extensive research in RPC-style web services. This paper introduces a formal definition of RESTful web services and proposes a method for RESTful web service composition based on Linear Logic. This is a two-stage proof-searching method that finds composition services at both resource and service invocation method levels. It greatly improves the searching efficiency and guarantees the correctness and completeness of the service composition process.

Healthcare-Event driven semantic knowledge extraction with hybrid data repository

In this paper, we introduce a Healthcare-Event (H-event) based knowledge extraction approach on a hybrid data repository. The repository collects (with individual users permission) dynamic and large volume healthcare related data from various resources such as wearable sensors, social media Web APIs and our application itself. The proposed extraction approach relies on two data processing processes. One is the data integration process to dynamically retrieving the large data using public data service APIs. The first process also generates a set of big knowledge bases and stored in NoSQL storage. This paper will focus on the second extraction process that is the H-Event based ontological knowledge extraction for detecting and monitoring users healthcare related situations, such as medical symptoms, treatments, conditions and daily activities from the NoSQL knowledge bases. The second process can be seen as post-processing step to detect more explicit healthcare knowledge about personalised health conditions and represent the knowledge using RDF formats in a semantic triple repository to enhance further data analytics.

Dynamic user equipment-based hysteresis-adjusting algorithm in LTE femtocell networks

In long-term evoluation (LTE) femtocell networks, hysteresis is one of the main parameters which affects the performance of handover with a number of unnecessary handovers, including ping-pong, early, late and incorrect handovers. In this study, the authors propose a hybrid algorithm that aims to obtain the optimised unique hysteresis for an individual mobile user moving at various speeds during the inbound handover process. This algorithm is proposed for two-tier scenarios with macro and femto. The centralised function in this study evaluates the overall handover performance indicator. Then, the handover aggregate performance indicator (HAPI) is used to determine an optimal configuration. Based on the received reference signal-to-interference-plus-noise ratio, the distributed function residing on the user equipment (UE) is able to obtain an optimal unique hysteresis for the individual UE. Theoretical analysis with three indication boundaries is provided to evaluate the proposed algorithm. A system-level simulation is presented, and the proposed algorithm outperformed the existing approaches in terms of handover failure, call-drop and redundancy handover ratios and also achieved better overall system performance.

An efficient interference mitigation approach via quasi-access in two-tier macro-femto heterogeneous networks

Summary Two-tier heterogeneous networks, where the current cellular networks, that is, macrocells, are overlapped with a large number of randomly distributed femtocells, can potentially bring significant benefits to spectral utilization and system capacity. In a two-tier network, the cross-tier interference needs to be handled properly. Unlike the downlink interference, the uplink (UL) interference at femtocell caused by macrocell user equipment (MUE) has not been addressed sufficiently. When an MUE is located near the coverage of femtocell, its transmit power may cause UL interference to the femtocell receiver, especially for the closed subscriber group femtocells that share the entire frequency spectrum with macrocell. We propose a novel quasi-access strategy, which allows the interfering MUE to connect with the interfered femtocell access point (FAP) while only via UL. It can significantly alleviate the UL interference at the FAP as well as its neighbors, in the meantime, benefit the macro-tier. Copyright