Emulation Architecture for Ad Hoc Networks

Abstract—The paper presents an emulation architecture working in the user space useful to implement and test routing protocols for ad hoc networks. The emulator creates an interface with the Simple Ad hoc siMulator (SAM) [1], where many routing protocols are present. The novelty with respect to SAM is the possibility to test the routing protocols with a real exchange of signaling and data packets between the hosts present in the network. With respect to a wireless live test, the emulator works on hosts connected each other via wired links and the wireless channel is simulated. To test the tool, many emulation trials have been performed by considering a simple routing protocol, and the final results are compared with those obtained by simulations

Performance Evaluation of a Wireless LAN Dynamic Multi Channel Allocation Strategy

This paper presents a Per-Packet Dynamic Channel Allocation algorithm with QoS support to be applied in a wireless multichannel environment. The strategy has been studied both in a simulative and in a more general analytical perspective. The results, concerning the packet drop probability D and the average number of used channel per non dropped activity U, show a high system efficiency in the resource use, with the possibility to be increased by simply grow the number of available channels; measured trend results linear and this indicates that quite good performance may be obtained by the system really outperforming the classical not cooperative solution

WIFE: WiFi Architecture for Ferrara Campus

Abstract—A WiFi network structure based on the extensive use of three levels of NAT is introduced. Such a system has been designed to avoid complex or proprietary roaming strategies and to keep very simple the system setup and configuration. Design constraints are related to the system scalability, to the transparency with respect to the actual in service network, to the possibility of offering location based service and to simply support mobility and in general access point handover. The proposed system has been implemented in the University of Ferrara campus and it is actually running. Some results regarding the first period user penetration and the system effectiveness are shown

A Per-Packet Based Channel Allocation Strategy: Preliminary Study

This work presents preliminary observations of a dynamic Per-Packet based Channel Allocation strategy, to be applied in multiple channels wireless networks in order to achieve advancements both in link connectivity speed and system QoS. The analyzed system model presents quite restrictive assumptions in order to simplify the complexity of an actual network and to just show the idea and give preliminary results regarding possible performance. Figures of merit considered are packet drop probability D and the average number of used channels per non dropped activity U . The obtained results show a higher system efficiency in the resource use in comparison to static channel allocation solutions; good performances, really outperforming classical not cooperative schemes, may be obtained by our channel allocation algorithm

Energy Efficient Unicast Routing Protocols over 802.11b

The paper compares the performance of the AODV, DSR, OESR classic routing protocols for ad hoc networks, when an IEEE 802.11b MAC protocol is used. The investigation, performed by means of simulations, evaluates the energy efficiency of these protocols and the effect of the 802.11b rate adaptation capability on the performance. The paper evaluates the effectiveness of a distributed power control (DPC) scheme (P. Bergamo et al., 2002) applied to the classic AODV, DSR and OESR routing algorithms. The DPC scheme, acting both at MAC and network layers, has the aim to reduce the overall power consumption of the network. In particular, DPC evaluates, hop-by-hop, the suitable transmit power level and then selects, end-to-end, for any destination, the path which minimizes the total transmit power required. A final comparison between classic and DPC routing protocols is also reported

Oligodeoxynucleotides antisense to c-abl specifically inhibit entry into S phase of CD34-positive hematopoietic cells and their differentation to granulocyte-macrophage progenitors

A number of experimental observations suggest that the proto-oncogene c-abl participates in the regulation of hematopoietic cell growth. We used an antisense strategy to study the relationship between c-abl expression and hematopoietic cell proliferation and differentiation. Purified normal human bone marrow-derived CD34+ cells were obtained by immunomagnetic selection and incubated with 18-base-unmodified antisense oligodeoxynucleotides complementary to the first six codons of the two alternative first exons of c-abl, la and lb. At the end of incubation, an aliquot of cells was assayed for clonogenic growth and the remainder was used for flow cytometric analyses. Cell kinetics were evaluated by means of both single parameter DNA and bivariate DNA/bromodeoxyuridine (BrdU) flow cytometry. Apoptosis was routinely studied by DNA flow cytometric analysis and, in some cases, also through DNA agarose gel electrophoresis for detection of oligonucleosomal DNA fragments. Expression of differentiation markers was studied by flow cytometry. Exposure to antisense oligonucleotides specifically inhibited the accumulation of c-abl mRNA in CD34+ cells. Preincubation with the c-abl antisense oligomers reduced the proportion of cells in S-phase from 19% +/- 5% (mean +/- SD) to 7% +/- 4% (P < .05), and BrdU labeling from 13% +/- 6% to 6% +/- 3% (P < .05). Flow cytometry and DNA agarose gel electrophoresis showed that treated CD34+ cells accumulated in the G0/G1 region of the DNA histogram with no evidence of either differentiation or apoptosis. By contrast, both growth factor deprivation and exposure of CD34+ cells to the tyrosine kinase inhibitor tyrphostin AG82 clearly induced apoptosis. When cells were preincubated with antisense oligonucleotides and then plated for evaluation of colony formation, this resulted in a significant inhibition of colony forming unit granulocyte-macrophage growth (from 44 +/- 15 to 22 +/- 9; P < .01) but had no effect on burst-forming unit erythroid growth (24 +/- 11 v 21 +/- 11; P < .05). These results suggest that c-abl expression is critical for entry of human CD34+ hematopoietic cells into S-phase and for their differentiation to granulocyte-macrophage progenitors. They also indicate that other tyrosine kinases besides p145c-alb are active in the prevention of apoptosis, so that inhibition of c-abl RNA accumulation arrests CD34+ cells in G0/G1 without activating programmed death