Higher education computer science programs traditionally focus on teaching a fairly common set of foundational programming and data structures concepts. While these foundational skills are necessary to prepare students for success as computer science or software engineering professionals, they are often insufficient to engage, inspire, and ensure persistence among the many students from first generation, low income and under-represented minority backgrounds who are pursuing degrees in computer science today. Within most academic programs there is limited opportunity for students to actually practice applying the skills they are learning to solve problems or to work with large existing code bases. Additionally, the focus on learning these foundational skills - often in discrete courses on discrete assignments - lacks the context and bigger picture that allows students to begin to develop a sense of belonging in the computer science profession. Revising the curricula within individual CS departments across multiple institutions to address these limitations would be extremely challenging and time-consuming. A viable alternative might be a scalable, non-institution-specific learning pathway that complements the knowledge and skills covered in most CS curriculum. In that vain, the Computing Talent Initiative (CTI), an institute at California State University Monterey Bay, has been offering a fully online program, called Accelerate, that is available for free to students studying CS from community colleges and state universities throughout California. The team is wrapping up the second year of offering this program, which has demonstrated promising results in helping students develop the skills and self-efficacy to make meaningful contributions to large, real-world software projects.

3D point cloud maps are an accumulation of laser scans obtained at different positions and times. Since laser scans represent a snapshot of the surrounding at the time of capture, they often contain moving objects which may not be observed at all times. Dynamic objects in point cloud maps decrease the quality of maps and affect localization accuracy, hence it is important to remove the dynamic objects from 3D point cloud maps. In this paper, we present a robust method to remove dynamic objects from 3D point cloud maps. Given a registered set of 3D point clouds, we build an occupancy map in which the voxels represent the occupancy state of the volume of space over an extended time period. After building the occupancy map, we use it as a filter to remove dynamic points in lidar scans before adding the points to the map. Furthermore, we accelerate the process of building occupancy maps using object detection and a novel voxel traversal method. Once the occupancy map is built, dynamic object removal can run in real-time. Our approach works well on wide urban roads with stopped or moving traffic and the occupancy maps get better with the inclusion of more lidar scans from the same scene.

CSin3 is a cohort-based, three-year computer science bachelor's degree program that has increased graduation rates of traditionally underrepresented computer science students. A collaborative effort between a community college and a public university, CSin3 provides a clear pathway for upward socio-economic mobility into the high-paying technology industry. CSin3 students are 90% from traditionally underrepresented groups, 80% first-generation, 32% female, and have a three-year graduation rate of 71%, compared to a 22% four-year graduation rate for traditional computer science students. Upon graduation, CSin3 students score similarly on a standardized exam of computer science knowledge as compared to traditional students who graduate in 4 years or more. The first graduates had a job placement rate of 78% within two months of graduation, including positions at large technology companies like Apple, Salesforce, and Uber. By implementing a cohort-based learning community, a pre-defined course pathway, just-in-time academic and administrative support, comprehensive financial aid, and a focus on 21st century skills, the CSin3 program has demonstrated promising results in addressing the capacity, cost, quality, and diversity challenges present in the technology industry.

A variety of network deployments in disaster recovery, fire fighting and military scenarios create networks that do not form a connected network all the time. In such scenarios, paths between a source and destination may be created over time when nodes encounter each other due to node mobility. Many routing algorithms that can route messages in such delay-tolerant networking (DTN) settings have been proposed. Each of these proposals presents simulation and/or analytical results to demonstrate improved performance in comparison with other known protocols. This paper proposes a common framework that defines multiple important components through which performance of these protocols can be compared using simulation experiments. This framework includes performance metrics that can be used for comparison, simulation environment, new mobility models and results in organizing the various known protocols based on their ability to predict a path. In a case study using the framework, we demonstrate how the predictive ability of PROPHET may or may not result in significant performance gains, depending on the mobility model.

This thesis presents a vertical handover decision (VHD) scheme for optimizing the efficiency of vertical handover processes in the Fourth Generation (4G) heterogeneous wireless networks. The scheme consists of three closely integrated modules: Handover necessity estimation, handover target selection, and handover triggering condition estimation. Handover necessity estimation module determines whether a handover is necessary to an available network. Handover target selection module chooses the ``best'' network among the available candidates based on a set of criteria. Finally, handover triggering condition estimation module determines the right moment to initiate a handover out of the currently connected network. 4G wireless networks are expected to support mechanisms for tight integration and cooperation of divergent access network technologies. In such networks of heterogeneous nature, roaming users will experience frequent handovers across network boundaries. Thus, to ensure seamless roaming and efficient resource usage over dissimilar networks, intelligent VHD algorithms need to be used extensively. The research project presented in this thesis report focuses on this problem and provides an optimized VHD scheme, which minimizes the handover failures, unnecessary handovers and connection breakdowns whilst maintaining users' satisfaction at high levels. In addition, the scheme also provides mechanisms for mobile applications to control the tradeoff between the usage of the preferred access network and number of handovers or connection breakdowns. Simulation based performance evaluations demonstrate that the scheme reduces the number of handover failures, unnecessary handovers and connection breakdowns by up to 80%, 70% and 70%, respectively. They also show an increase of up to 50% in the satisfaction level of users.

The increasing popularity of Internet wide overlay networks require mechanisms for delay prediction between any given pair of nodes without having to actually measure the delay. Internet Coordinate Systems (ICS) have been proposed to enable such delay prediction. Most of the known ICS mechanisms require a set of landmark servers for hosts to measure their distance with and use those mea- surements to derive their coordinates. For P2P systems, it is preferable to use a distributed scheme where deployment of landmarks are not required. Vivaldi is such a distributed scheme. We propose an improved scheme in which hosts dynamically change the set of neighbors with which they measure distances. Our proposed improvement to the Vi- valdi algorithm reduces the bandwidth consumption by up to 50% while maitaining the same accuracy of the delay es- timations. We introduce a new metric named relative delay loss (rdl) that captures how well the coordinate system picks the closest node between two given nodes and captures the magnitude of the error when the pick is wrong. Our pro- posed scheme presents a significant improvement measured with this new metric.

Due to the broadcast nature of wireless signals, a wireless transmission intended for a particular destination station can be overheard by other neighboring stations. A focus of recent research activities in cooperative communications is to achieve spatial diversity gains by requiring these neighboring stations to retransmit the overheard information to the final destination. In this paper we demonstrate that such cooperation among stations in a wireless LAN (WLAN) can achieve both higher throughput and lower interference. We present the design for a medium access control protocol called CoopMAC, in which high data rate stations assist low data rate stations in their transmission by forwarding their traffic. In our proposed protocol, using the overheard transmissions, each low data rate node maintains a table, called a CoopTable, of potential helper nodes that can assist in its transmissions. During transmission, each low data rate node selects either direct transmission or transmission through a helper node in order to minimize the total transmission time. Using analysis, simulation and testbed experimentation, we quantify the increase in the total network throughput, and the reduction in delay, if such cooperative transmissions are utilized. The CoopMAC protocol is simple and backward compatible with the legacy 802.11 system. In this paper, we also demonstrate a reduction in the signal-to-interference ratio in a dense deployment of 802.11 access points, which in some cases is a more important consequence of cooperation

authors calculate the maximum number of VoIP calls that a WiFi (VoFi) network can support. In this paper we extend their analysis to calculate the maximum number of VoFi calls when two-hop forwarding is used in order to avoid rate adaptation at nodes with reduced received signal strength. We calculate this number for different combinations of data rates for slow node transmissions and potential two-hop transmissions. These calculations demonstrate that the use of two-hop forwarding increases the maximum number of VoIP calls in a multi-rate 802.11b network. We validate the analysis by means of simulation of G711 codec sources in a 802.11b network. Even though the earlier discussions focus on specific combinations of high data rate two-hop and low data rate one-hop transmissions in an 802.11b network, we conclude the paper by calculating the maximum number of VoIP calls that can be supported with uniform node distri-bution in 802.11b and 802.11g networks. These calculations show a significant increase in the number of VoIP calls when two-hop forwarding is used in an 802.11g network. This sig-nificant increase is due to the higher data rates and the low PHY overhead of the 802.11g MAC.

A wide range of applications from file sharing to VoIP communications have been developed and deployed using peer-to-peer (p2p) networks. With the increased use of p2p communication systems like Skype, the ability to leave a message for an offline recipient is needed to complete the user experience. Without this ability, p2p communication systems cannot provide the widely used set of services avail- able in traditional communication systems. In this paper, we present design issues for a p2p multimedia messaging service and focus on the scalability of such service. We present an analysis for the probability of successful retrieval with re- spect to the number of replication required and bandwidth cost. Conversely, we tabulate the number of mailboxes re- quired to achieve a particular reliability level. Applying the layered or scalable coding methods developed for images or video, we also consider three types of message replica- tion schemes: whole message replication where the complete message is stored in all the selected peers, progressive layer- ing based replication where individual layers are stored in independent peers, and hierarchical layering based replica- tion where a collection of layers are stored in each peer. A sample JPEG image is used for concrete cost calculation and comparison. Our analysis demonstrates that the expected savings in bandwidth cost due to layering is dependent on the distribution of information content in the layers. So, based on the coding scheme available for the particular type of media, developing layering-aware replication for P2P sys- tems holds significant promise in terms of bandwidth cost savings leading to a more scalable messaging service. In our analysis, assuming a disproportionate amount of informa- tion content per bit in lower layers, we were able to observe up to 30% saving in the bandwidth cost with the layering

In wireless LANs that provide multi-rate support (IEEE 802.11a, 802.11b), stations that experience poor channel quality tend to use low transmission rates to reduce the bit-error-rate (BER) of each transmission. This phenomenon usually leads to a throughput fairness problem between the stations with good channel quality and those without. This fairness problem has been shown to result in throughput degradation for the whole network [8]. The MAC protocol proposed in [5] addresses this issue using an efficient cooperative scheme. Under this scheme, low rate stations are assisted by a high rate station, referred to as helper stations, in its transmissions. With such assistance, the low rate station will be able to transmit data at a higher rate in a two-hop manner using the helper station. We implemented this new protocol in a Linux testbed. This paper describes the assumptions, the implementation process and the challenges we were presented with. We evaluated the protocol using our testbed through experiments. The implementation of the protocol shows that it performs efficiently in supporting TCP applications.

Real-time multimedia transport has stringent quality of service requirements, which are generally not supported by current network architectures. In emerging mobile ad hoc networks, frequent topology changes and link failures cause severe packet losses, which degrade the quality of received media. However, in such mesh networks, there usually exist multiple paths between any source and destination nodes. Such path diversity has been demonstrated to be effective in combating congestion and link failures for improved media quality. In this paper, we present a new protocol to facilitate multipath transport of real-time multimedia data. The proposed protocol, the multiflow real-time transport protocol (MRTP), provides a convenient vehicle for real-time applications to partition and transmit data using multiple flows. We demonstrate through analysis that data partitioning, which is an essential function of MRTP, can effectively reduce the short-range dependence of multimedia data, thus improving its queueing performance in underlying networks. Furthermore, we show that a few flows are sufficient for MRTP to exploit most of the benefits of multipath transport. Finally, we present a comprehensive simulation study on the performance of MRTP under a mobile ad hoc network. We show that with one additional path, MRTP outperformed single-flow RTP by a significant margin.

The mobile IPv6 handover process consists of three major stages: movement detection, duplicate address detection and binding signaling. Most of the research efforts for optimizing the handover process focuses on minimizing the delays caused by the first two stages. The delay introduced by binding signaling is largely ignored since the correspondent node is assumed to be stationary. However, this delay can be significant when two communicating nodes are both mobile and may roam across different networks simultaneously. mobile IPv6 requires that the binding signaling exchanged between the mobile node and the correspondent node to be authenticated using a procedure called return mutability test. The signaling involved in the return routability procedure is mandated to be redirected through the home agents to the most up-to-date addresses of the communicating nodes. This may result in a longer handover duration if the mobile and correspondent nodes are both far from their home agent, In this paper, we present our recommendation on the use of direct signaling without the need to have any redirection from a network element. We also present an analysis of the cost involved in utilizing direct and indirect signaling mechanisms.

IEEE 802.11 specifies two modes of operation, an infrastructure mode where nodes communicate to/through an access point, and an ad-hoc mode, where nodes communicate with each other directly. Neither mode supports multiple hop transmissions between these nodes. In this paper we present two advantages in extending 802.11 MAC to support multiple hops in the infrastructure mode. One advantage is higher available bandwidth in a multi-rate 802.11 network. IEEE 802.11 allows hosts to select different transmission rates based on the quality of the signal received by the host. Based on performance results both from analytical modeling and simulations, we demonstrate that the total available bandwidth can be improved by using multiple hops instead of reducing the transmission rates of nodes. We present the results in terms of both the increase in total throughput of the network and the available throughput for the forwarding node. The second advantage presented is that by using multi-hop transmissions, the power of transmission at the edges of 802.11 cells can be reduced resulting in lower interference with nodes at the edges of other 802.11 cells. This leads to a more uniform coverage, with increased throughput experienced by nodes at the cell edges.

A novel quality of service (QoS) scheduling mechanism suitable for transporting variable bit rate video in the upstream direction over a DOCSIS (data over cable system interface specification)-compliant cable network is presented. It is shown, via simulation using real life video traces, that the proposed scheduling service provides significant improvements as compared to the existing DOCSIS QoS scheduling services, with regard to bandwidth utilization and latency distribution. The proposed scheduling service is also applicable to transport integrated services over the Internet and can be utilized by other emerging multimedia applications, where data are bursty in nature and variable in bit rate.