An effective full-system virtual prototype is critical for early-stage systems design exploration. Generally, however, traditional acceleration approaches of virtual prototypes cannot accurately analyze system performance and model non-deterministic inter-component interactions due to the unpredictability of simulation progress. In this paper, we propose an effective virtualization-assisted approach for modeling and performance analysis. First, we develop a deterministic synchronization process that manages the interactions affecting the data dependency in chronological order to model inter-component interactions consistently. Second, we create accurate timing and bus contention models based on runtime operation statistics for analyzing system performance. We implement the proposed virtualization-assisted approach on an off-the-shelf System-on-Chip (SoC) board to demonstrate the effectiveness of our idea. The experimental results show that the proposed approach runs 12~77 times faster than a commercial virtual prototyping tool and performance estimation is only 3~6% apart from real systems.

Accurate orientation information is the key in many applications, ranging from map reconstruction with crowdsourcing data, location data analytics, to accurate indoor localization. Many existing solutions rely on noisy magnetic and inertial sensor data, leading to limited accuracy, while others leverage multiple, dense anchor points to improve the accuracy, requiring significant deployment efforts. This paper presents LiCompass, the first system that enables a commodity camera to accurately estimate the object orientation using just a single optical anchor. Our key idea is to allow a camera to observe varying intensity level of polarized light when it is in different orientations and, hence, perform estimation directly from image pixel intensity. As the estimation relies only on pixel intensity, instead of the location of the anchor in an image, the system performs reliably at long distance, with low resolution images, and with large perspective distortion. LiCompass' core designs include an elaborate optical anchor design and a series of signal processing techniques based on trigonometric properties, which extend the range of orientation estimation to full 360 degrees. Our prototype evaluation shows that LiCompass produces very accurate estimates with median errors of merely 2.5 degrees at 5 meters and 7.4 degrees at 2.5 meters with an irradiance angle of 55 degrees.

In this paper we extend the concept of the traditional transactor, which focuses on correct content transfer, to a new timing-coherent transactor that also accurately aligns the timing of each transaction boundary so that designers can perform precise concurrent system behavior analysis in mixed-abstraction-level system simulations which are essential to increasingly complex system designs. To streamline the process, we also developed an automatic approach for timing-coherent transactor generation. Our approach is actually applied in mixed-level simulations and the results show that it achieves 100% timing accuracy while the conventional approach produces results of 25% to 44% error rate.

Recent literatures have demonstrated the feasibility and applicability of light-to-camera communications. They either use this new technology to realize specific applications, e.g., localization, by sending repetitive signal patterns, or consider non-line-of-sight scenarios. We however notice that line-of-sight light-to-camera communications has a great potential because it provides a natural way to enable visual association, i.e., visually associating the received information with the transmitter's identity. Such capability benefits broader applications, such as augmented reality, advertising, and driver assistance systems. Hence, this paper designs, implements, and evaluates RollingLight, a line-of-sight light-to-camera communication system that enables a light to talk to diverse off-the-shelf rolling shutter cameras. To boost the data rate and enhance reliability, RollingLight addresses the following practical challenges. First, its demodulation algorithm allows cameras with heterogeneous sampling rates to accurately decode high-order frequency modulation in real-time. Second, it incorporates a number of designs to resolve the issues caused by inherently unsynchronized light-to-camera channels. We have built a prototype of RollingLight with USRP-N200, and also implemented a real system with Arduino Mega 2560, both tested with a range of different camera receivers. We also implement a real iOS application to examine our real-time decoding capability. The experimental results show that, even to serve commodity cameras with a large variety of frame rates, RollingLight can still deliver a throughput of 11.32 bytes per second.

Multicore instruction-set simulation (MCISS) has become more and more important due to tremendous increase in number of multicore designs. To boost the speed of MCISS, one of the most effective and commonly used approaches is parallel simulation. However, timing synchronization must be applied to ensure accurate simulation results of parallel MCISS, and may induce huge synchronization overhead. In this paper, we propose a highly efficient and effective parallel MCISS approach by synchronizing timing before each synchronization function (SF) call. We improve the applicability of the state-of-the-art critical-section-level simulation approach with a generic blocking/nonblocking send/receive model covering all types of SFs. To further reduce synchronization overhead, we also introduce optimization methods such as a hybrid scheduling technique and provide an analysis algorithm that helps the designers to choose the host platform with the best simulation performance. Experiments show that the proposed approach attains a simulation speed of up to 285 MIPS, while producing accurate timing and functional results.

This paper proposes a Critical-Section-Level timing synchronization approach for deterministic Multi-Core Instruction-Set Simulation (MCISS). By synchronizing at each lock access instead of every shared-variable access and using a simple lock usage status managing scheme, our approach significantly improves simulation performance while executing all critical sections in a deterministic order. Experiments show that our approach performs 295% faster than the shared-variable synchronization approach on average and can effectively facilitate system-level software/hardware co-simulation.

This paper proposes using a non-intrusive timing synchronization interface approach to facilitate shared-data synchronization for fast and accurate hardware-assisted HW/SW co-simulation. Our synchronization interface device is specially designed for non-transparent components. With the device, we can systematically monitor shared-data accesses on a bus and control the progressing time of hardware-assisted components for fast and accurate system co-simulation. Experiments show that our approach is 10 to 140 times faster than the cycle-based hardware-assisted co-simulation approach.