University of the Witwatersrand

Displaying 1-22 of 22 results

  • White Papers // Apr 2013

    Dynamic Virtual Machine Allocation in Cloud Server Facility Systems with Renewable Energy Sources

    In this paper, the authors explore the problem of Virtual Machine (VM) allocation in a network of cloud server facilities which are deployed in different geographical areas. Each cloud server facility is connected to the conventional power grid network and in addition it is supported by an attached Renewable Energy...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2013

    Distributed Space-Time Coding of Over-the-Air Superimposed Packets in Wireless Networks

    In this paper, the authors propose a new cooperative packet transmission scheme that allows independent sources to superimpose over-the-air their packet transmissions. Relay nodes are used and cooperative diversity is combined with distributed Space-Time Block Coding (STBC). With the proposed scheme the participating relays create a ST code for the...

    Provided By University of the Witwatersrand

  • White Papers // Feb 2013

    Wireless Network Coding: Deciding When to Flip the Switch

    Network coding has been shown to offer significant throughput benefits over store-and-forward routing in certain wireless network topologies. However, the application of network coding may not always improve the network performance. In this paper, the authors provide a comprehensive analytical study, which helps in assessing when network coding is preferable...

    Provided By University of the Witwatersrand

  • White Papers // Oct 2012

    Link Scheduling in Cooperative Wireless Networks

    In this paper the authors propose link scheduling algorithms for a wireless network that employs different modes of cooperation at the PHYsical layer (PHY). In addition to a direct transmission, a cooperative transmission through a relay and cooperative transmission through Physical Layer Network Coding (PLNC) can also be employed by...

    Provided By University of the Witwatersrand

  • White Papers // Jun 2012

    Design and Implementation of Distributed Resource Management Mechanisms for Wireless Mesh Networks

    The wireless mesh networks are usually consisted of a static wireless backbone. The main wireless mesh routers serve the routing of the traffic, while the peripheral routers act as Access Points (APs). These APs are associated with the STAtions (STAs) in the network. The STA association/handoff procedures are very important...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2012

    An Efficient Probing Mechanism for Next Generation Mobile Broadband Systems

    Opportunistic scheduling exploits multiuser diversity for improving the performance of wireless systems. However, it requires instantaneous Channel State Information (CSI) to be available at the transmitter side. Since acquiring CSI is resource consuming, it always comes at a cost. The authors consider the problem of efficient channel state estimation in...

    Provided By University of the Witwatersrand

  • White Papers // Nov 2011

    Energy-Efficient Planning and Management of Cellular Networks

    The authors study base stations energy-efficient management algorithms in a cellular access network taking into account different planning strategies. To provide energy savings, sleep modes are adopted at the Base Stations (BSs). They propose two switch-off strategies that are based either on the cell load or the BS coverage overlap....

    Provided By University of the Witwatersrand

  • White Papers // Aug 2011

    Cooperative Sensing Reliability Improvement Algorithm for Primary Radio Signal Detection in Cognitive Radio Environment

    This paper addresses issues on cooperative spectrum sensing reliability improvement for primary radio signal detection in a cognitive radio environment. In particular, the paper extends previous studies on spectrum sensing time algorithm for predicting ideal sensing duration for detecting a primary radio signal in a cognitive radio environment. The extended...

    Provided By University of the Witwatersrand

  • White Papers // Aug 2011

    Analysis of the Impact of Some Network Parameters on the Accuracy of RSS-Based Geometric Positioning Methods

    The accuracy of Received Signal Strength (RSS)-based positioning methods is highly variable due to its dependence on various varying parameters such as the wireless environment, topology of the network, propagation model utilized etc. In this paper, simulated data was analyzed to examine the effect distances and number of BSs used...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2011

    Uncertainty for Privacy and 2-Dimensional Range Query Distortion

    In this paper, the authors study the problem of privacy-preserving data publishing in moving objects databases. In particular, the trajectory of a mobile user on the plane is no longer a polyline in a two-dimensional space, instead it is a two-dimensional surface of fixed width 2Amin, where Amin defines the...

    Provided By University of the Witwatersrand

  • White Papers // Nov 2010

    Foreign Direct Investment And The Internationalisation Of South African Mining Companies Into Africa

    The paper investigates the factors influencing the internationalization of mining firms into Africa and the strategies employed. The authors focus on the FDI of South African mining firms because of the dominance of this country in the extractive resources industry for over a century. A semi-structured interview survey process consisting...

    Provided By University of the Witwatersrand

  • White Papers // Jul 2010

    Using Public Cellular Networks to Provide Wireless Access in a Campus Environment

    Students of today require computer and network access to be as widespread as possible. Universities have responded by deploying campus wide Wi-Fi networks, but in many cases the capital and operational costs prohibit this solution. This paper proposes a low cost alternative that utilises public cellular network infrastructure as a...

    Provided By University of the Witwatersrand

  • White Papers // Jul 2010

    Performance Analysis of RSS-Based Geometric Positioning Methods in GSM Networks

    Location-based services are fast becoming popular in different areas of the world due to the availability of smart phones and investments by mobile operators in satisfying requests from users. The Quality of Service (QoS) offered in LBS is dependent on the amount mobile users and the mobile network operators are...

    Provided By University of the Witwatersrand

  • White Papers // Apr 2010

    Managing the Converged Reconfigurable Radio System Architecture

    Heterogeneous wireless networks are created through the integration of numerous independently standardised Radio Access Technologies (RATs). This integration is achieved through the use of interworking network entities such as gateways. This approach to integration does not enable network operators to leverage the full capabilities of their combined radio resources. Reconfigurable...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2010

    Formalising the NGN Application Layer

    Development of applications based on call/session signalling such as SIP is limited as it requires software programmers to possess detailed knowledge of telecommunications technologies. In addition, this type of application development leads to a telecommunications application layer with limited structure. This paper proposes a service development approach based on direct...

    Provided By University of the Witwatersrand

  • White Papers // Oct 2009

    Downlink Transmission Optimization and Statistical Feedback Strategies in a Multi-User IEEE 802.16m System

    A multi-user MIMO/OFDMA system for the next generation Broadband Wireless Access (BWA) networks is studied, in which the Base Station (BS) has only knowledge of the statistics of the channel. A combination of MIMO, OFDMA and FDD could be suitable to increase spectral efficiency in a high speed network. The...

    Provided By University of the Witwatersrand

  • White Papers // Jul 2009

    A Computational Ecology Based Approach to Routing in Communication Networks

    The routing and flow control problems in communication networks are considered in this progress report. The problem is cast into an agent/resource allocation model referred to as a computational ecology. To achieve this, data packets are considered as agents and outgoing links from nodes as resources. The paper covers the...

    Provided By University of the Witwatersrand

  • White Papers // Jun 2009

    Direct Feedback Based on Cellular Technology to Support Demand-Side Energy Management

    The century-old power grids do not meet many of the requirements of modern economies. The invisibility of the details of electricity consumption is the prime cause behind much of the wastage of domestic electricity. Utilities are also not able to log detailed information about the consumption patterns of each of...

    Provided By University of the Witwatersrand

  • White Papers // Jun 2009

    Detection of Primary Radio Signals in Cognitive Radio Environment

    This paper presents a work in progress on adaptive cognitive radio system. The paper discusses an approach towards the sensing and detection of primary radio signals using modulation identification technique. Cognitive radio is visualized and realized as an intelligent software package simply referred to as a cognitive engine. In carrying...

    Provided By University of the Witwatersrand

  • White Papers // May 2009

    A Modular Approach for the Development of a Reconfigurable Access Network Architecture

    The existence of numerous competing mobile standards forces network operators and subscribers to either upgrade or purchase new mobile equipment whenever new standards are developed. This is an inherent weakness within the standards development methodology. The reconfigurability concept attempts to solve this problem by providing the means to implement or...

    Provided By University of the Witwatersrand

  • White Papers // May 2009

    Broadcast Erasure Channel with Feedback - Capacity and Algorithms

    The authors consider the two-user broadcast erasure channel where feedback in the form of ack messages is fed back to the transmitter. They provide an upper bound to the capacity region of this sys-tem. They then present two algorithms whose rate region (information bits per transmitted bit) becomes arbitrarily close...

    Provided By University of the Witwatersrand

  • White Papers // Apr 2009

    Identifying Unsafe Routes for Network-Based Trajectory Privacy

    In this paper, the authors propose a privacy model that offers trajectory privacy to the requesters of Location-Based Services (LBSs), by utilizing an underlying network of user movement. The privacy model has been implemented as a framework that reconstructs the user movement from a series of independent location updates, identifies...

    Provided By University of the Witwatersrand

  • White Papers // Nov 2010

    Foreign Direct Investment And The Internationalisation Of South African Mining Companies Into Africa

    The paper investigates the factors influencing the internationalization of mining firms into Africa and the strategies employed. The authors focus on the FDI of South African mining firms because of the dominance of this country in the extractive resources industry for over a century. A semi-structured interview survey process consisting...

    Provided By University of the Witwatersrand

  • White Papers // Jun 2009

    Direct Feedback Based on Cellular Technology to Support Demand-Side Energy Management

    The century-old power grids do not meet many of the requirements of modern economies. The invisibility of the details of electricity consumption is the prime cause behind much of the wastage of domestic electricity. Utilities are also not able to log detailed information about the consumption patterns of each of...

    Provided By University of the Witwatersrand

  • White Papers // Jun 2009

    Detection of Primary Radio Signals in Cognitive Radio Environment

    This paper presents a work in progress on adaptive cognitive radio system. The paper discusses an approach towards the sensing and detection of primary radio signals using modulation identification technique. Cognitive radio is visualized and realized as an intelligent software package simply referred to as a cognitive engine. In carrying...

    Provided By University of the Witwatersrand

  • White Papers // May 2009

    A Modular Approach for the Development of a Reconfigurable Access Network Architecture

    The existence of numerous competing mobile standards forces network operators and subscribers to either upgrade or purchase new mobile equipment whenever new standards are developed. This is an inherent weakness within the standards development methodology. The reconfigurability concept attempts to solve this problem by providing the means to implement or...

    Provided By University of the Witwatersrand

  • White Papers // Jul 2009

    A Computational Ecology Based Approach to Routing in Communication Networks

    The routing and flow control problems in communication networks are considered in this progress report. The problem is cast into an agent/resource allocation model referred to as a computational ecology. To achieve this, data packets are considered as agents and outgoing links from nodes as resources. The paper covers the...

    Provided By University of the Witwatersrand

  • White Papers // Jul 2010

    Using Public Cellular Networks to Provide Wireless Access in a Campus Environment

    Students of today require computer and network access to be as widespread as possible. Universities have responded by deploying campus wide Wi-Fi networks, but in many cases the capital and operational costs prohibit this solution. This paper proposes a low cost alternative that utilises public cellular network infrastructure as a...

    Provided By University of the Witwatersrand

  • White Papers // Jul 2010

    Performance Analysis of RSS-Based Geometric Positioning Methods in GSM Networks

    Location-based services are fast becoming popular in different areas of the world due to the availability of smart phones and investments by mobile operators in satisfying requests from users. The Quality of Service (QoS) offered in LBS is dependent on the amount mobile users and the mobile network operators are...

    Provided By University of the Witwatersrand

  • White Papers // Apr 2010

    Managing the Converged Reconfigurable Radio System Architecture

    Heterogeneous wireless networks are created through the integration of numerous independently standardised Radio Access Technologies (RATs). This integration is achieved through the use of interworking network entities such as gateways. This approach to integration does not enable network operators to leverage the full capabilities of their combined radio resources. Reconfigurable...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2012

    An Efficient Probing Mechanism for Next Generation Mobile Broadband Systems

    Opportunistic scheduling exploits multiuser diversity for improving the performance of wireless systems. However, it requires instantaneous Channel State Information (CSI) to be available at the transmitter side. Since acquiring CSI is resource consuming, it always comes at a cost. The authors consider the problem of efficient channel state estimation in...

    Provided By University of the Witwatersrand

  • White Papers // Aug 2011

    Cooperative Sensing Reliability Improvement Algorithm for Primary Radio Signal Detection in Cognitive Radio Environment

    This paper addresses issues on cooperative spectrum sensing reliability improvement for primary radio signal detection in a cognitive radio environment. In particular, the paper extends previous studies on spectrum sensing time algorithm for predicting ideal sensing duration for detecting a primary radio signal in a cognitive radio environment. The extended...

    Provided By University of the Witwatersrand

  • White Papers // Aug 2011

    Analysis of the Impact of Some Network Parameters on the Accuracy of RSS-Based Geometric Positioning Methods

    The accuracy of Received Signal Strength (RSS)-based positioning methods is highly variable due to its dependence on various varying parameters such as the wireless environment, topology of the network, propagation model utilized etc. In this paper, simulated data was analyzed to examine the effect distances and number of BSs used...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2010

    Formalising the NGN Application Layer

    Development of applications based on call/session signalling such as SIP is limited as it requires software programmers to possess detailed knowledge of telecommunications technologies. In addition, this type of application development leads to a telecommunications application layer with limited structure. This paper proposes a service development approach based on direct...

    Provided By University of the Witwatersrand

  • White Papers // Jun 2012

    Design and Implementation of Distributed Resource Management Mechanisms for Wireless Mesh Networks

    The wireless mesh networks are usually consisted of a static wireless backbone. The main wireless mesh routers serve the routing of the traffic, while the peripheral routers act as Access Points (APs). These APs are associated with the STAtions (STAs) in the network. The STA association/handoff procedures are very important...

    Provided By University of the Witwatersrand

  • White Papers // Nov 2011

    Energy-Efficient Planning and Management of Cellular Networks

    The authors study base stations energy-efficient management algorithms in a cellular access network taking into account different planning strategies. To provide energy savings, sleep modes are adopted at the Base Stations (BSs). They propose two switch-off strategies that are based either on the cell load or the BS coverage overlap....

    Provided By University of the Witwatersrand

  • White Papers // Oct 2009

    Downlink Transmission Optimization and Statistical Feedback Strategies in a Multi-User IEEE 802.16m System

    A multi-user MIMO/OFDMA system for the next generation Broadband Wireless Access (BWA) networks is studied, in which the Base Station (BS) has only knowledge of the statistics of the channel. A combination of MIMO, OFDMA and FDD could be suitable to increase spectral efficiency in a high speed network. The...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2013

    Distributed Space-Time Coding of Over-the-Air Superimposed Packets in Wireless Networks

    In this paper, the authors propose a new cooperative packet transmission scheme that allows independent sources to superimpose over-the-air their packet transmissions. Relay nodes are used and cooperative diversity is combined with distributed Space-Time Block Coding (STBC). With the proposed scheme the participating relays create a ST code for the...

    Provided By University of the Witwatersrand

  • White Papers // Oct 2012

    Link Scheduling in Cooperative Wireless Networks

    In this paper the authors propose link scheduling algorithms for a wireless network that employs different modes of cooperation at the PHYsical layer (PHY). In addition to a direct transmission, a cooperative transmission through a relay and cooperative transmission through Physical Layer Network Coding (PLNC) can also be employed by...

    Provided By University of the Witwatersrand

  • White Papers // May 2009

    Broadcast Erasure Channel with Feedback - Capacity and Algorithms

    The authors consider the two-user broadcast erasure channel where feedback in the form of ack messages is fed back to the transmitter. They provide an upper bound to the capacity region of this sys-tem. They then present two algorithms whose rate region (information bits per transmitted bit) becomes arbitrarily close...

    Provided By University of the Witwatersrand

  • White Papers // Feb 2013

    Wireless Network Coding: Deciding When to Flip the Switch

    Network coding has been shown to offer significant throughput benefits over store-and-forward routing in certain wireless network topologies. However, the application of network coding may not always improve the network performance. In this paper, the authors provide a comprehensive analytical study, which helps in assessing when network coding is preferable...

    Provided By University of the Witwatersrand

  • White Papers // Apr 2009

    Identifying Unsafe Routes for Network-Based Trajectory Privacy

    In this paper, the authors propose a privacy model that offers trajectory privacy to the requesters of Location-Based Services (LBSs), by utilizing an underlying network of user movement. The privacy model has been implemented as a framework that reconstructs the user movement from a series of independent location updates, identifies...

    Provided By University of the Witwatersrand

  • White Papers // Apr 2013

    Dynamic Virtual Machine Allocation in Cloud Server Facility Systems with Renewable Energy Sources

    In this paper, the authors explore the problem of Virtual Machine (VM) allocation in a network of cloud server facilities which are deployed in different geographical areas. Each cloud server facility is connected to the conventional power grid network and in addition it is supported by an attached Renewable Energy...

    Provided By University of the Witwatersrand

  • White Papers // Mar 2011

    Uncertainty for Privacy and 2-Dimensional Range Query Distortion

    In this paper, the authors study the problem of privacy-preserving data publishing in moving objects databases. In particular, the trajectory of a mobile user on the plane is no longer a polyline in a two-dimensional space, instead it is a two-dimensional surface of fixed width 2Amin, where Amin defines the...

    Provided By University of the Witwatersrand