10867701
Asymptotic Capacity of Infrastructure Wireless Mesh Networks
An infrastructure wireless mesh network (WMN) is a hierarchical network consisting of mesh clients, mesh routers and gateways. Mesh routers constitute a wireless mesh backbone, to which mesh clients are connected as a star topology, and gateways are chosen among mesh routers providing Internet access. In this paper, the throughput capacity of infrastructure WMNs is studied. For such a network with Nc randomly distributed mesh clients, Nr regularly placed mesh routers and Ng gateways, assuming that each mesh router can transmit at W bits/s, the per-client throughput capacity has been derived as a function of Nc , Nr , Ng and W . The result illustrates that, in order to achieve high capacity performance, the number of mesh routers and the number of gateways must be properly chosen. It also reveals that an infrastructure WMN can achieve the same asymptotic throughput capacity as that of a hybrid ad hoc network by choosing only a small number of mesh routers as gateways. This property makes WMNs a very promising solution for future wireless networking.
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.
37285882
Dynamic adaptation of CSMA/CA MAC protocol for wide area wireless mesh networks
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, 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. In fact, in 802.11, a transmitter can face ACK/CTS timeout even when it started receiving ACK/CTS packet before the timeout value. We present three strategies, (i) multiplicative timer backoff (MTB), (ii) additive timer backoff (ATB), and (iii) link RTT memoization (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 link 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.
22092303
Nanotechnology as a field of science: Its delineation in terms of journals and patents
The Journal Citation Reports of the Science Citation Index 2004 were used to delineate a core set of nanotechnology journals and a nanotechnology-relevant set. In comparison with 2003, the core set has grown and the relevant set has decreased. This suggests a higher degree of codification in the field of nanotechnology: the field has become more focused in terms of citation practices. Using the citing patterns among journals at the aggregate level, a core group of ten nanotechnology journals in the vector space can be delineated on the criterion of betweenness centrality. National contributions to this core group of journals are evaluated for the years 2003, 2004, and 2005. Additionally, the specific class of nanotechnology patents in the database of the U. S. Patent and Trade Office (USPTO) is analyzed to determine if non-patent literature references can be used as a source for the delineation of the knowledge base in terms of scientific journals. The references are primarily to general science journals and letters, and therefore not specific enough for the purpose of delineating a journal set.
206599167
A Fuzzy Logic Expert System for Fault Diagnosis and Security Assessment of Power Transformers
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.
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.
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.