14589917
Frequent value compression in packet-based NoC architectures
The proliferation of Chip Multiprocessors (CMPs) has led to the integration of large on-chip caches. For scalability reasons, a large on-chip cache is often divided into smaller banks that are interconnected through packet-based Network-on-Chip (NoC). With increasing number of cores and cache banks integrated on a single die, the on-chip network introduces significant communication latency and power consumption. In this paper, we propose a novel scheme that exploits Frequent Value compression to optimize the power and performance of NoC. Our experimental results show that the proposed scheme reduces the router power by up to 16.7%, with CPI reduction as much as 23.5% in our setting. Comparing to the recent zero pattern compression scheme, the frequent value scheme saves up to 11.0% more router power and has up to 14.5% more CPI reduction. Hardware design of the FV table and its overhead are also presented.
13798358
A durable and energy efficient main memory using phase change memory technology
Using nonvolatile memories in memory hierarchy has been investigated to reduce its energy consumption because nonvolatile memories consume zero leakage power in memory cells. One of the difficulties is, however, that the endurance of most nonvolatile memory technologies is much shorter than the conventional SRAM and DRAM technology. This has limited its usage to only the low levels of a memory hierarchy, e.g., disks, that is far from the CPU.
 In this paper, we study the use of a new type of nonvolatile memories -- the Phase Change Memory (PCM) as the main memory for a 3D stacked chip. The main challenges we face are the limited PCM endurance, longer access latencies, and higher dynamic power compared to the conventional DRAM technology. We propose techniques to extend the endurance of the PCM to an average of 13 (for MLC PCM cell) to 22 (for SLC PCM) years. We also study the design choices of implementing PCM to achieve the best tradeoff between energy and performance. Our design reduced the total energy of an already low-power DRAM main memory of the same capacity by 65%, and energy-delay2 product by 60%. These results indicate that it is feasible to use PCM technology in place of DRAM in the main memory for better energy efficiency.
11399662
Adaptive Buffer Management for Efficient Code Dissemination in Multi-Application Wireless Sensor Networks
Future wireless sensor networks (WSNs) are projected to run multiple applications in the same network infrastructure. While such multi-application WSNs (MA-WSNs) are economically more efficient and adapt better to the changing environments than traditional single-application WSNs, they usually require frequent code redistribution on wireless sensors, making it critical to design energy efficient post-deployment code dissemination protocols in MA-WSNs. Different applications in MA-WSNs often share some common code segments. Therefore when there is a need to disseminate a new application from the sink node, it is possible to disseminate its shared code segments from peer sensors instead of disseminating everything from the sink node. While dissemination protocols have been proposed to handle code of each single type, it is challenging to achieve energy efficiency when the code contains both types and needs simultaneous dissemination. In this paper we utilize an adaptive buffer management approach to achieve efficient code dissemination in MA-WSNs. Our experimental results show that adaptive buffer management can reduce the completion time and the message overhead up to 10% and 20% respectively.
2961354
On Adding Link Dimensional Dynamism to CSMA/CA Based MAC Protocols
Though the popular IEEE 802.11 DCF is designed primarily for wireless LAN (WLAN) environments, today it is being widely used for wide area wireless mesh networking. The protocol parameters of IEEE 802.11 such as timeout values, interframe spaces, and slot durations, which are sufficient for a general WLAN environment need to be modified in order to efficiently operate in wide area wireless mesh networks. The current wide area wireless mesh network deployments use manual configuration of these parameters to the upper limit which essentially makes the networks operate at lower system efficiency. In this paper, we propose d802.11 (dynamic 802.11) which dynamically adapts the protocol parameters in order to operate at varying link distances. We present three strategies, (i) multiplicative timer back-off (MTB), (ii) additive timer back-off (ATB), and (iii) link RTT memorization (LRM), to adapt the ACK_TIMEOUT in d802.11 in order to provide better adaptation for varying link dimensions. Through extensive simulation experiments we observed significant performance improvement for the proposed strategies. We also theoretically modeled the maximum throughput as a function of the link dimension for the proposed system. Our results show that the LRM technique provides the best adaptation compared to all other schemes.
16634499
An Approximate Controller for Nonlinear Networked Control Systems with Time Delay
An approximation controller is developed to obtain an optimal control for nonlinear networked control systems (NCS) with time delay. In the approach only the non-linear compensating term, solution of a sequence of adjoint vector differential equations, is required iteration. By taking the finite iteration of non-linear compensating term of optimal solution sequence, a suboptimal control law for NCS can be obtained.
25182935
An efficient random access scheme for OFDMA systems with implicit message transmission
Random access channel (RACH) is usually used for initial channel access, bandwidth request, etc. In this paper, we analyze the throughput and access delay performance of the RACH in an orthogonal frequency division multiple access (OFDMA) system. A closed-form expression of the RACH throughput is presented and its mean access delays under both binary exponential and uniform backoff policies have also been derived. Moreover, to further improve the utilization of RACH in an OFDMA system, we propose a novel message transmission scheme in a shared RACH. The message in the proposed scheme can be sent implicitly in the cyclic-shifted preambles which make the transmission much more reliable in a contention based RACH. Meanwhile, performance of the preamble detection has also been improved by the redundant information conveyed in messages. Finally, simulation results will demonstrate performance gains of the proposed scheme.
16952040
A Speaker Verification System Based on EMD
Most of the speech utterance feature extraction methods are based on the assumptions: utterance signal is short-term stable and independent between each other adjacent frames. This approach ignores the dynamic characteristics of speech signal. For the time-varying characteristics of the speech utterance, we propose a new feature extraction method based on empirical mode decomposition EMD. We can extract the LPCC feature parameters from different stages of IMFs which are decomposed by EMD process. A speaker verification system based on EMD is proposed and it is shown that it is better performance than the one with traditional LPCC features based on short-term process.
6645019
An Energy Reporting Aggregation Method Based on EAFM and DTRM in WSN
Analyzed the energy consumption disciplinarian of the nodes in WSN, the node’s Energy Attenuation Forecast Model(EAFM) can be established. A Difference-threshold Reporting Mechanism (DTRM) is used to report the residual energy of nodes. The energy collection mechanism based on EAFM and DTRM can reduce energy data reporting times significantly,improve the efficient of energy data collection, save the node's energy at the same time. The experiments in the platform of telosb nodes show that the predicable rate is between 70% and85%, and this method can extend the node’s life by 1% ~ 4.5%.