Staff Profiles

Internet of Things (IoT), Artificial Intelligence, Machine Learning, Robotics

Wireless Communications, Heterogeneous Wireless Networks, Multimedia Wireless Communications

Intelligent Transportation Systems, Wireless Vehicular Access

Machine-to-Machine (M2M) Communications

Mobile Cloud Computing, Mobile Social Networks

Research group membership

Research grants and awards

EU FP7 MONICA (Mobile Cloud Computing: Networks, Services and Architecture) Project (295222), www.fp7-monica.eu. The consortium comprises 7 universities: Oxford Brookes University (Project Coordinator), Institut Télécom & Management SudParis (France), University of Muenster (Germany), University of Essex (UK), Huazhong University of Science & Technology (China), Jilin University (China), Xidian University (China). Brookes is the leading university. Role: Project Coordinator and Principal Investigator (PI). (Jan 2012 – Dec 2015)

Consultancy service for "Proposal for ETHOS Validation of on-street parking monitoring system", Mar-2016 – June 2016

TSB Funded KTP Project on Robust Wireless Communications between Road Studs, Vehicles and Roadside Equipment (KTP009072). The industrial partner is Clearview Traffic Group (www.clearviewtraffic.com). Role: Principal Investigator and the Academic Supervisor of the KTP Associate. (Jan 2013 – May 2015)

UK EPSRC (Engineering & Physics Science Research Council) project PANDA (Policy-based Model-driven Pervasive Service Creation and Adaptation).  15th December 2006 – 14th June 2009, Role: Internal Co-investigator

Journal articles

• Wang X, Wang K, Wu S, Di S, Jin H, Yang K, Ou S, 'Dynamic Resource Scheduling in Mobile Edge Cloud with Cloud Radio Access Network'
  IEEE Transactions on Parallel and Distributed Systems 29 (11) (2018) pp.2429-2445
  ISSN: 1045-9219
  Abstract

  Nowadays, by integrating the cloud radio access network (C-RAN) with the mobile edge cloud computing (MEC) technology, mobile service provider (MSP) can efficiently handle the increasing mobile traffic and enhance the capabilities of mobile devices. But the power consumption has become skyrocketing for MSP and it gravely affects the profit of MSP. Previous work often studied the power consumption in C-RAN and MEC separately while less work had considered the integration of C-RAN with MEC. In this paper, we present an unifying framework for the power-performance tradeoff of MSP by jointly scheduling network resources in C-RAN and computation resources in MEC to maximize the profit of MSP. To achieve this objective, we formulate the resource scheduling issue as a stochastic problem and design a new optimization framework by using an extended Lyapunov technique. Specially, because the standard Lyapunov technique critically assumes that job requests have fixed lengths and can be finished within each decision making interval, it is not suitable for the dynamic situation where the mobile job requests have variable lengths. To solve this problem, we extend the standard Lyapunov technique and design the VariedLen algorithm to make online decisions in consecutive time for job requests with variable lengths. Our proposed algorithm can reach time average profit that is close to the optimum with a diminishing gap (1/V) for the MSP while still maintaining strong system stability and low congestion. With extensive simulations based on a real world trace, we demonstrate the efficacy and optimality of our proposed algorithm.
  

  Website 
• Roman C, Liao R, Ball P, Ou S, de Heaver M, 'Detecting On-Street Parking Spaces in Smart Cities: Performance Evaluation of Fixed and Mobile Sensing Systems'
  IEEE Transactions on Intelligent Transportation Systems 19 (7) (2018) pp.2234-2245
  ISSN: 1524-9050 eISSN: 1558-0016
  Abstract As the number of vehicles continues to grow, parking spaces are at a premium in city streets. In addition, due to the lack of knowledge about street parking spaces, heuristic circling in the streets not only costs drivers’ time and fuel, but also increases city congestion. In the wake of the recent trend to build convenient, green and energy-efficient smart cities, common techniques adopted by high-profile smart parking systems are reviewed, and the performance of the various approaches are compared. A mobile sensing unit has been developed as an alternative to the fixed sensing approach. It is mounted on the passenger side of a car to measure the distance from the vehicle to the nearest roadside obstacle. By extracting parked vehicles’ features from the collected trace, a supervised learning algorithm has been developed to estimate roadside parking occupancy. Multiple road tests were conducted around Wheatley (Oxfordshire) and Guildford (Surrey) in the UK. In the case of accurate GPS readings, enhanced by a map matching technique, the accuracy of the system is above 90%. A quantity estimation model is derived to calculate the density of sensing units required to cover urban streets. The estimation is quantitatively compared to a fixed sensing solution. The results show that the mobile sensing approach can perform at the same level as fixed sensing solutions when accurate location information is available but substantially fewer sensors are needed compared to the fixed sensing system.Website 
• Liang K, Zhao LQ, Zhao XH, Wang Y, Ou SM, 'Joint Resource Allocation and Coordinated Computation Offloading for Fog Radio Access Networks'
  China Communications 13 (s2) (2016) pp.131-139
  ISSN: 1673-5447
  Abstract The cloud radio access network (C-RAN) and the fog computing have been recently proposed to tackle the dramatically increasing traffic demands and to provide better quality of service (QoS) to user equipment (UE). Considering the better computation capability of the cloud RAN (10 times larger than that of the fog RAN) and the lower transmission delay of the fog computing, we propose a joint resource allocation and coordinated computation offloading algorithm for the fog RAN (F-RAN), which takes the advantage of C-RAN and fog computing. Specifically, the F-RAN splits a computation task into the fog computing part and the cloud computing part. Based on the constraints of maximum transmission delay tolerance, fronthaul and backhaul capacity limits, we minimize the energy cost and obtain optimal computational resource allocation for multiple UE, transmission power allocation of each UE and the event splitting factor. Numerical results have been proposed with the comparison of existing methods.Website 
• Roman C, Ball P, Ou S, 'Multiple Interface Scheduling System for Heterogeneous Wireless Vehicular Networks: Description and Evaluation'
  EAI Endorsed Transactions on Wireless Spectrum 3 (11) (2016)
  ISSN: 2312-6620
  Abstract

  Reliable wireless communications between vehicles (V2V) and between vehicles and infrastructure (V2I) will
  play a key role in future transport networks. Where there is overlapping coverage of multiple Radio Access
  Technologies, with no cooperation between them, a vehicle can use the different technologies simultaneously.
  This paper proposes an uplink Multi Interface Scheduling System (MISS) located at an intermediate shim
  layer on the user side, to achieve efficient bandwidth aggregation, or lower end-to-end packet delay. MISS
  aims to find all the available networks that can meet multiple criteria based on user preference and required
  performance. Simulation results show that safety critical traffic can be prioritized where the resources are
  insufficient for all the services. Video delivery quality is also improved by prioritizing the most important
  frames. This algorithm is ideally suited to vehicular networks, where delivery of safety traffic and/or video is
  an essential requirement.

  Website 
• Roman C, Liao R, Ball P, Ou S, 'Mobility and Network Selection in Heterogeneous Wireless Networks: User Approach and Implementation'
  Network Protocols and Algorithms 8 (2) (2016) pp.107-122
  ISSN: 1943-3581
  Abstract The Intelligent Transport Systems (ITS) wireless infrastructure needs to support various safety and non-safety services for both autonomous and non-autonomous vehicles.The existing wireless infrastructures can already be used for communicating with different mobile entities at various monetary costs.A packet scheduler, included in a shim layer between the network layer and the medium access (MAC) layer, which is able to schedule packets between uncoordinated Radio Access Technologies (RATs) without modification of the wireless standards, has been devised and its performance evaluated.In this paper, we focus on the influence of mobility type in heterogeneous wireless networks.Three cases are considered based on the mobility in the city: walking, cycling, and driving. Realistic simulations are performed by generating mobility traces of Oxford from Google Maps and overlaying the real locations of existing WiFi Access Points. Results demonstrate that the shim layer approach can accommodate different user profiles and can be a useful abstraction to support Intelligent Transport Systems where there is no coordination between different wireless operators.Website 
• Liao R, Roman C, Ball P, Ou S, Chen L, 'Crowdsourcing On-street Parking Space Detection'
  arXiv (2016)
  ISSN: 2331-8422
  Abstract

  As the number of vehicles continues to grow, parking spaces are at a premium in city streets. Additionally, due to the lack of knowledge about street parking spaces, heuristic circling the blocks not only costs drivers' time and fuel, but also increases city congestion. In the wake of recent trend to build convenient, green and energy-efficient smart cities, we rethink common techniques adopted by high-profile smart parking systems, and present a user-engaged (crowdsourcing) and sonar-based prototype to identify urban on-street parking spaces. The prototype includes an ultrasonic sensor, a GPS receiver and associated Arduino micro-controllers. It is mounted on the passenger side of a car to measure the distance from the vehicle to the nearest roadside obstacle. Multiple road tests are conducted around Wheatley, Oxford to gather results and emulate the crowdsourcing approach. By extracting parked vehicles' features from the collected trace, a supervised learning algorithm is developed to estimate roadside parking occupancy and spot illegal parking vehicles. A quantity estimation model is derived to calculate the required number of sensing units to cover urban streets. The estimation is quantitatively compared to a fixed sensing solution. The results show that the crowdsourcing way would need substantially fewer sensors compared to the fixed sensing system.
  

  Website 
• Ou S, Yang K, Zhu H, 'Dynamic algorithms for autonomic pervasive services in mobile wireless environments'
  International Journal of Autonomic Computing 1 (4) (2010) pp.391-407
  ISSN: 1741-8569
  Abstract Pervasive services have attracted numerous attentions from both industries and academia. Its very high adaptability demand makes autonomic computing (AC), and in particular, personal autonomic computing (PAC), an ideal enabling technology. Some generic AC frameworks have been proposed in the literature but without considering the dynamic deployment and re-configuration of pervasive service components in a self-controlled manner. Further, very little attention has been paid to providing autonomic pervasive services in mobile wireless environments. This paper addresses above issues. In particular, a service component self-deployment algorithm using partitioning techniques is proposed and evaluated; a simple service re-configuration algorithm is also presented; and a service self-healing mechanism is proposed. In addition, an AC environment is proposed and its major building blocks being discussed. This AC environment serves as the container of the proposed service component self-deployment, self-configuration and self-healing mechanisms. A prototype of the system has been designed and implemented. Experiment results have shown the effectiveness of the proposed mechanisms.Website 
• Ou S, 'QoS-aware Two-level Dynamic Uplink Bandwidth Allocation Algorithms in IEEE 802.16j Based Vehicular Networks'
  Wireless Personal Communications 56 (3) (2010) pp.417-433
  ISSN: 0929-6212 eISSN: 1572-834X
  Abstract Wireless communications play an important role in improving transportation environment safety and providing Internet access for vehicles. This paper proposes a QoS-aware two-level uplink dynamic bandwidth allocation (DBA) algorithm for IEEE 802.16j-based vehicular networks. IEEE 802.16j is an extension of standard IEEE 802.16 to support relay mode operation where traffics from/to subscriber stations (SS) are relayed to/from a base station (BS) via a relay station (RS). In such a vehicular network, the IEEE 802.16j BSs are installed along a highway, RSs are installed in large vehicles such as coaches, and the 802.16j interface is equipped on SSs such as individual passengers" mobile devices within a moving coach. In the proposed DBA algorithm, a utility function, which considers characteristics of different types of services, is designed. The objective of the proposed two-level DBA algorithm is to allocate bandwidth to different types of services from BS to RSs and then from a RS to SSs with given quality of service (QoS) requirements. It aims at maximizing the utility of the overall network and minimizing the average queuing delay of the overall network. The simulation results show the effectiveness and efficiency of the proposed DBA algorithm.Website 
• Fei R, Yang K, Ou S, 'A QoS-aware dynamic bandwidth allocation algorithm for relay station in IEEE 802.16j-based vehicular networks'
  IEEE Wireless Communications and Networking Conference (WCNC) (2010)
  ISSN: 1525-3511
  Abstract

  IEEE 802.16 has been regarded as a promising broadband wireless access technology for its large coverage, quality of service (QoS) support for different types of application, and easy deployment. IEEE 802.16j is an extension of IEEE 802.16 to support relay mode operation. This paper applies IEEE 802.16j to vehicular network to provide Internet access for high-way vehicles. In particular, it proposes a dynamic bandwidth allocation (DBA) algorithm specifically for relay stations (RS) to support QoS requirements of different types of service. The objective of the proposed DBA is to allocate bandwidth from relay station to its serving subscriber stations (SSs) with QoS consideration. The simulation results have shown the effectiveness and efficiency of the proposed DBA algorithm.

  Website 
• Ou S, Yang K, Chen H-H, 'Integrated dynamic bandwidth allocation in converged passive optical networks and IEEE 802.16 networks'
  IEEE Systems Journal 4 (4) (2010) pp.467-476
  ISSN: 1932-8184
  Abstract

  IEEE 802.16 and Passive Optical Network (PON) are two promising broadband access technologies for high-capacity wireless access networks and wired access networks, respectively. The convergence of 802.16 and PON networks can take the mobility feature of wireless communications and the bandwidth advantage of optical networks jointly. Dynamic bandwidth allocation (DBA) plays an important role in each of these two networks for QoS assurance. In converged 802.16 and PON networks, the integration of the DBA schemes in both networks plays an even more critical role, since bandwidth request/grant mechanisms used in 802.16 and PON are different and the performance of the integrated DBA directly determines the overall system performance. In this paper, we investigate integrated dynamic bandwidth allocation schemes and their signaling overhead. First, this paper starts with discussing the converged network architecture and especially the issues on integrating optical network unit (ONU) and 802.16 base station (BS). Second, it proposes a slotted DBA (S-DBA) scheme and its performance analytic model. The S-DBA scheme takes into account the specific features of the converged network, aiming to reduce signaling overhead caused by cascaded bandwidth requests and grants. The simulation results show that the proposed S-DBA scheme can effectively reduce signaling overhead and increase channel utilization.

  Website 
• Ou S, 'A utility-based dynamic bandwidth allocation algorithm in IEEE802.16 networks to minimize average queuing delay'
  Wireless Communications and Mobile Computing 3 (2009) pp.349-353
  ISSN: 1530-8669
  Abstract This paper starts with detailing the IEEE 802.16 network architecture and the quality of service (QoS) architecture; followed by a network utility function, which is related to the average queuing delay of each subscriber station (SS); and then a dynamic bandwidth allocation (DBA) algorithm is proposed. This algorithm takes into consideration the QoS requirements of different traffic types and makes use of a utility function to minimize the average queuing delay. Simulation results have shown the efficiency of the DBA.Website 
• Ou S, Yang K, Chen H-H, Galis A, 'A selective downlink scheduling algorithm to enhance the quality of VOD services for WAVE networks'
  EURASIP Journal on Wireless Communications and Networking - (-) (2009) pp.1-12
  ISSN: 1687-1472
  Abstract

  Providing quality-of-service- (QoS-) guaranteed video on demand (VOD) services over wireless access in vehicular environments (WAVEs) is a challenge as WAVE adopts enhanced distributive channel access (EDCA), a contention-based channel access mechanism, for air interface access control. This paper proposes a selective downlink scheduling (SDS) algorithm to enhance the quality of VOD for WAVE networks. According to the importance of video decoding, video packets are categorized into high and low priorities. The categorized packets are put into different queues in roadside units (RSUs) to contend for transmission opportunities. Aiming to improve video playback quality and reduce video playback delay, the proposed SDS algorithm schedules video packets based on their importance, playback deadline, and their real-time parameters of receiving onboard units (OBUs), such as velocity and remaining dwelling time. The effectiveness of SDS algorithm is verified by simulations.

  Website 
• Yang K, Ou S, Guild K, Chen H-H, 'Convergence of ethernet PON and IEEE 802.16 broadband access networks and its QoS-Aware dynamic bandwidth allocation scheme'
  IEEE Journal on Selected Areas in Communications 27 (2) (2009) pp.101-116
  ISSN: 0733-8716
  Abstract

  IEEE 802.16 and Ethernet Passive Optical Network (EPON) are two promising broadband access technologies for high-capacity wireless access networks and wired access networks, respectively. They each can be deployed to facilitate connection between the end users and the Internet but each of them suffers from some drawbacks if operating separately. To combine the bandwidth advantage of optical networks with the mobility feature of wireless communications, we propose a convergence of EPON and 802.16 networks in this paper. First, this paper starts with presenting the converged network architecture and especially the concept of virtual ONU-BS (VOB). Then, it identifies some unique research issues in this converged network. Second, the paper investigates a dynamic bandwidth allocation (DBA) scheme and its closely associated research issues. This DBA scheme takes into consideration the specific features of the converged network to enable a smooth data transmission across optical and wireless networks, and an end-to-end differentiated service to user traffics of diverse QoS (Quality of Service) requirements. This QoS-aware DBA scheme supports bandwidth fairness at the VOB level and class-of-service fairness at the 802.16 subscriber station level. The simulation results show that the proposed DBA scheme operates effectively and efficiently in terms of network throughput, average/maximum delay, resource utilization, service differentiation, etc.

  Website 
• Ou S, 'An effective offloading service for Resource-Constrained mobile devices running heavier mobile internet applications'
  IEEE Communications Magazine 46 (1) (2008) pp.56-63
  ISSN: 0163-6804 eISSN: 1558-1896
  Abstract Rapid advances in wireless mobile network technologies and mobile handsets (MHs) facilitate ubiquitous infrastructure that can support a range of mobile services and applications in addition to conventional mobile Internet access. One recent trend is to effectively run desktop PC-oriented heavier applications on MHs. However, due to their miniature, portable size, MHs are resource-constrained and therefore, running these applications directly on an MH is not satisfactory given a user's expectations. To cope with this problem, this article proposes a novel offloading service that can seamlessly offload some of the tasks of a mobile application from an MH to nearby, resource-rich PCs (called surrogates). The system architecture and key components of the proposed offloading service are presented, prototyped, and evaluated. The results of experiments and simulations have demonstrated the effectiveness and efficiency of this offloading service for mobile applications.Website 

Conference papers

• Roman C, Ball P, Ou S, 'Evaluating the benefit of a smart scheduler in a non-cooperative, multi-user heterogeneous wireless ITS environment'
  (2018)
  Abstract Heterogeneous wireless networks will play a significant role in providing multiservice connectivity in ITS, and in particular vehicular networks. This paper describes a smart scheduling approach that allows end user nodes to direct packets over the best available wireless access technologies and set priorities for selected services. The performance of this smart scheduler has been simulated in a non-cooperative multi user environment and the results show that, for the prioritised services, the scheduler can provide a lower average packet delay and a higher average packet delivery ratio for all users than a wireless system that selects on signal strength alone.Website 
• Alshudukhi J, Ou S, Ball P, 'A MAC Protocol for Wireless Sensors in a Fixed Chain Topology'
  (2017) pp.29-35
  ISBN: 978-1-4673-9791-9
  Abstract This paper presents a time division multiple access MAC protocol that is specifically designed for applications requiring periodic sensing of the sensor field. Numerical analysis is conducted to investigate the optimum transmission scheduling based on the signal to interferencenoise-ratio (SINR) for ground level propagation model applied on wireless chain topology. The optimised transmission schedule considers the SINR value to enable simultaneous transmission from multiple nodes. The most significant advantages of this approach are reduced delay and improve the Packet Received Ratio PRR. Simulation is performed to evaluate the proposed protocol for intelligent transport system applications. The simulation results validate the MAC protocol for a fixed chain topology compared with the similar protocols. Website 
• Ball P, Liao R, Roman C, Ou S, Pow E, 'Analysis of Fixed and Mobile Sensor Systems for Parking Space Detection'
  (2016)
  ISBN: 978-1-5090-2527-5 eISBN: 978-1-5090-2526-8
  Abstract This paper analyses the relative merits of fixed and mobile sensor solutions for monitoring street car parking availability. A fixed sensor solution requires placement of sensors under each allocated parking space. The mobile approach uses a ranger mounted on a moving vehicle which continuously monitors the presence of parked cars and spaces. One of the challenges of the mobile sensor solution is to account for the variability of the position of the vehicle across the road. This paper proposes a dual detector solution using sonar and lidar together with differential detection system to mitigate the uncertainty.
   
  Website 
• Roman C, Sapienza M, Ball P, Ou S, Cuzzolin F, Torr PHS, 'Heterogeneous Wireless System Testbed for Remote Image Processing in Automated Vehicles'
  (2016)
  ISBN: 978-1-5090-2526-8
  Abstract Automated vehicles will carry computing and communication platforms, and will have enhanced sensing capabilities. Safety around people along with obstacle detection and avoidance systems are key to their success. In controlled environments, automated vehicles can benefit from a remote processing approach to reduce cost and accelerate deployment on larger scales. In this paper we present a section of our intelligent transport systems testbed which evaluates the remote image processing approach with a novel heterogeneous wireless communication system. Hardware implementation is carried out for an experimental evaluation and comparison with the simulation results.Website 
• Roman C, Ball P, Ou S, 'Performance Evaluation of Dynamic Scheduler in Multiple Queue Shim Layer for Heterogeneous Vehicular Communications'
  (2015)
  ISBN: 978-1-4673-9526-7
  Abstract

  Reliable wireless communications between vehicles (V2V) and between vehicles and infrastructure (V2I) will play a key role in future transport networks. Where there is overlapping coverage of multiple Radio Access Technologies, with no cooperation between them, a vehicle can use the different technologies simultaneously to enhance performance and improve resilience. This paper proposes an uplink Multi Interface Scheduling System (MISS) that incorporates intelligent interface selection, located at an intermediate shim layer on the user side, to achieve efficient bandwidth aggregation, or lower delay. Rather than finding the best alternative amongst different technologies, this paper’s algorithm aims to find all the available networks that can meet multiple criteria. Simulation has been carried out to determine the performance of the system in the presence of a range of different service types. The simulation results show that safety critical traffic can be prioritized in terms of throughput and delay where the resources are insufficient for all the services. This algorithm is ideally suited to vehicular networks, particularly where delivery of safety traffic is an essential requirement.

  Website 
• Roman C, Ball P, Ou S, 'A Shim Layer for Heterogeneous Wireless Communications Scheduling in Intelligent Transport Systems'
  (2015) pp.174-179
  ISBN: 978-1-4673-7194-0
  Abstract
  Given the future context of fully integrated Intelligent Transport Systems, reliable wireless communications is a necessity. Traditionally, a single wireless technology is selected for communication but by using heterogeneous wireless communication, advantage can be taken of the different transmission characteristics. This paper proposes a novel Multiple Interface Scheduling Algorithm (MISA) which schedules uplink packets over multiple technologies for which no coordination is required among access networks. The algorithm incorporates a dynamic scoring approach for each of the available networks based on selected system performance parameters. A key feature of the proposed scheduler is that it is located between the IP layer and the MAC layer, hence a single IP address is used, and it is not necessary to modify the wireless standards. A model has been developed to simulate the proposed algorithm and the system performance for three multi radio transmission diversity schemes. The results show the advantage that can be gained in throughput by cooperatively using multiple technologies.
  Website 
• Alshudukhi J, Ou S, Ball P, Zhao L, Zhao G, 'Energy Efficiency Metrics for Low-Power Near Ground Level Wireless Sensors'
  (2015) pp.329-335
  ISBN: 978-1-4673-7701-0
  Abstract

  This paper proposes green energy efficiency metrics for low-power wireless sensors operating at ground level. The metrics are derived from our previous work on energy efficiency analysis for general wireless networks and a radio propagation model for near ground level wireless sensors. A numerical analysis is carried out to investigate the utilization of the green energy efficiency metrics for ground level communication in wireless sensor networks. The proposed metrics have been developed to calculate the optimal sensor deployment, antenna height and energy efficiency level for the near ground wireless sensor. As an application of the proposed metrics, the relationship between the energy efficiency and the spacing between the wireless sensor nodes is studied. The results provide an accurate guidance for energy efficient deployment of near ground level wireless sensors. 

  Website 
• Alshudukhi J, Ou S, Ball P, 'A Ground Level Radio Propagation Model for Road-based Wireless Sensor Networks'
  (2014) pp.146-151
  ISBN: 978-1-4799-2581-0
  Abstract

  Abstract— this paper investigates the use of a wireless sensor network (WSN) for communicating between road-based nodes. These nodes are situated at ground level and two-way wireless communication is required between the nodes and from the nodes to a roadside control unit. Measurements have been carried out to examine the propagation close to the ground to determine the maximum distance between roadbased nodes as a function of the antenna height. The results show that for a frequency of 2.4 GHz, a range of up to 8m is achievable with 2mW EIRP. An empirical near-ground level radio propagation model is derived and the predicted results from this model are shown to match closely to the measured results.

  Website 
• Ou S, 'A Utility-based Dynamic Bandwidth Allocation Algorithm with QoS Guarantee for IEEE 802.16j-enabled Vehicular Networks'
  (2009) pp.200-205
  Abstract In this paper, we propose a utility-based uplink dynamic bandwidth allocation (DBA) algorithm for the IEEE 802.16j-enabled vehicular network. In the proposed DBA algorithm, a utility function, which considers characteristics of different types of service, is designed, and the utility of the total network is formulated. The objective of the proposed DBA algorithm is to allocate bandwidth to different types of service with quality of service (QoS) considered, by maximizing the utility of the overall network and further minimizing the average queuing delay of the overall system, with reasonable consideration to the required minimum bandwidth of different types of service, rtPS, nrtPS and BE. The solution to the problem of maximizing the utility of the total network is solved by using Lagrange multipliers with relaxed constraints. The simulation results have shown the effectiveness and efficiency of the proposed DBA algorithm.Website 
• Ou S, Liu D, Yang K, 'Dynamic algorithms for self-deployment and self-configuration of pervasive service components'
  (2009) pp.525-530
  Abstract Pervasive services have attracted numerous attentions from both industries and academia. Its very high adaptability demand makes autonomic computing (AC), and in particular, personal autonomic computing (PAC), an ideal enabling technology. Some generic AC framework has been proposed in the literature but without considering the dynamic deployment and re-configuration of pervasive service components in a self-controlled manner. This paper makes some preliminary attempts towards these two issues. In particular, a service component self-deployment algorithm using partitioning techniques is proposed and evaluated. A simple service reconfiguration algorithm is also presented. In addition, an AC environment is proposed and its major building blocks being discussed. This AC environment serves as the container of the proposed service component self-deployment and self-configuration mechanisms. A prototype of the system has been designed and implemented. Experiment results have shown the effectiveness of the proposed mechanismsWebsite 
• Ou S, 'Performance analysis of fault-tolerant offloading systems for pervasive services in mobile wireless environments'
  (2008) pp.1856-1860
  Abstract Offloading (also known cyber-foraging) is an approach to leverage the severity of resource constrained nature of mobile devices (such as PDAs) by migrating part of the computation of applications to some nearby resource-rich surrogates (e.g., desktop PCs). It is an essential mechanism for the execution of pervasive applications. However, the mobile nature of mobile devices and the unstable connectivity of wireless links all render a less predictability of the performance of a pervasive application running under the control of offloading systems. This paper proposes an analytical model to express the performance of fault- tolerant offloading systems in mobile wireless environments. We model the failure recovery time and total execution time of pervasive applications that run under the control of the fault- tolerant offloading systems. The model is analyzed numerically and primarily evaluated based on a real application.Website 
• Ou S, Yang K, Farrera M, Okonkwo C, Guild K, 'A control bridge to automate the convergence of passive optical networks and IEEE 802.16 (WiMAX) wireless networks'
  (2008) pp.514-521
  ISSN: 978-1-4244-2391-0 eISBN: 978-1-4244-2392-7
  Abstract IEEE 802.16 and Passive Optical Network (PON) are two promising broadband access technologies for high-capacity wireless and wired access networks, respectively. In order to better understand the co-existence of both network technologies and to determine whether closer cooperation in the bandwidth provisioning process is advantageous, an access network that utilizes a Gigabit PON (GPON) to backhaul 802.16 network traffic is evaluated. Typical to many network deployments, the equipment is from different manufacturers and has different management and control interfaces. This paper proposes the use of a control bridge that overlooks the operations of both the GPON and 802.16 networks in order to: (1) provide dynamic QoS mapping so as to reduce traffic delivery cost; and (2) to improve overall channel utilization through coordinated dynamic bandwidth allocation. The performance of the converged network under the control of the proposed control bridge is evaluated in terms of cost of data delivery, channel utilization, and service differentiation.Website