MACA-P: A MAC for Concurrent Transmissions in Multi-hop Wireless Networks

Abstract: This paper presents the initial design and performance study of MACA-P, a RTS/CTS based MAC protocol that enables simultaneous transmissions in multihop ad-hoc wireless networks. Providing such low-cost multihop and high performance wireless access networks is an important enabler of pervasive computing. MACA-P is a set of enhancements to the 802.11 DCF that allows parallel transmissions in many situations when two neighboring nodes are either both receivers or both transmitters, but a receiver and a transmitter are not neighbors. Like 802.11, MACA-P contains a contention-based reservation phase prior to data transmission. However, the data transmission is delayed by a control phase interval, which allows multiple sender-receiver pairs to synchronize their data transfers, thereby avoiding collisions and improving system throughput. II. I

DCMA: A Label-Switching MAC for efficient packet forwarding in multi-hop wireless networks

Special Issue on “Multi-Hop Wireless Mesh Networks”</p

High-performance architectures for IP-based multihop 802.11 networks

The concept of a forwarding node, which receives packets from upstream nodes and then transmits these packets to downstream nodes, is a key element of any multi-hop network, wired or wireless. While high-speed IP router architectures have been extensively studied for wired networks, the concept of a “wireless IP router ” has not been addressed so far. In this paper, we examine the limitations of the IEEE 802.11 MAC protocol in supporting a low-latency and high-throughput IP datapath comprising multiple wireless LAN hops. We first propose a wireless IP forwarding architecture that uses MPLS with modifications to the 802.11 MAC to significantly improve the packet forwarding efficiency. We then study further enhancements to the 802.11 MAC that improve the system throughput by allowing a larger number of concurrent packet transmissions in multi-hop 802.11-based IP networks. With 802.11 poised to be the dominant technology for wireless LANs, we believe a combined approach to MAC, packet forwarding and transport layer protocols is needed to make highperformance multi-hop 802.11 networks practically viable. 1

Assessment of genetic diversity among 16 promising cultivars of ginger using cytological and molecular markers

Ginger (Zingiber officinale Roscoe) is an economically important plant, valued all over the world. The existing variation among 16 promising cultivars as observed through differential rhizome yield (181.9 to 477.3 g) was proved to have a genetic basis using different genetic markers such as karyotype, 4C nuclear DNA content and random amplified polymorphic DNA (RAPD). The karyotypic analysis revealed a differential distribution of A, B, C, D and E type of chromosomes among different cultivars as represented by different karyotype formulas. A significant variation of 4C DNA content was recorded in ginger at an intraspecific level with values ranging from 17.1 to 24.3 pg. RAPD analysis revealed a differential polymorphism of DNA showing a number of polymorphic bands ranging from 26 to 70 among 16 cultivars. The RAPD primers OPC02, OPA02, OPD20 and OPN06 showing strong resolving power were able to distinguish all 16 cultivars. The extent of genetic diversity among these cultivars was computed through parameters of gene diversity, sum of allele numbers per locus and Shannon&apos;s information indices. Cluster analysis, Nei&apos;s genetic similarity and genetic distances, distribution of cultivars into special distance classes and principal coordinate analysis and the analysis of molecular variance suggested a conspicuous genetic diversity among different cultivars studied. The genetic variation thus detected among promising cultivars of ginger has significance for ginger improvement programs. Key words: Ginger, Karyotype, RAPD Introduction Zingiber officinale is rich in secondary metabolites such as oleoresin. It possesses an unique combination of properties like anti-inflammatory, aphrodisiac, antioxidant and antibacterial activity S. Nayak et al. · Genetic Diversity among Ginger Cultivars In the past decade, DNA polymorphism has become the marker of choice for the identification and characterization of plants. It is a relatively reliable, generally applicable method to obtain large samples of markers from any species of plant. However, each marker system samples a different fraction of the genomes and therefore has a different resolving power, range of applicability and probability of homology. The random amplified polymorphic DNA (RAPD) technique has been widely used in cultivar identification programs The objectives of this study were to (1) fingerprint ginger cultivars for identification and (2) detect the genetic diversity and relatedness of 16 cultivars sampled from different geographical regions using karyotypic analysis, 4C DNA content and RAPD analysis. In this study, many analytical procedures such as a n-j method, bootstrapping, spatial genetic structure analysis (SGS), and analysis of molecular variance (AMOVA) have been widely used to derive genetic distances among cultivars and to assess the structure of genetic data in a reduced dimensional space. Materials and Methods Plant materials Sixteen promising cultivars of ginger (Zingiber officinale) were included in the present study which were collected from the turmeric germplasm collection of the Orissa University of Agriculture and Techology (OUAT), Bhubaneswar, Orissa, India. These cultivars were initially collected from different parts of India Karyotype analysis Young and healthy root-tips of different cultivars of ginger were pre-treated in a (0.02 m) hydroxyquinoline mixture (1:1) for 3.5 h at 14 ∞C followed by overnight fixation in propionic ethanol. Chromosome staining was made in 2% lacto propionic orcin after cold hydrolysis in 5 n HCl for 7 min. Root-tips were squashed in 45% propionic acid. Ten well scattered metaphase plates were selected for karyotype analysis of each species. The chromosome morphology was determined following the method of 4C DNA content For Feulgen cytophotometric estimation of 4C DNA, ten fixed root-tips from each cultivar (2n = 22 chromosomes) were hydrolysed in 1 n HCl for 12 min at 60 ∞C, washed in distilled water and stained in Schiff&apos;s reagent for 2 h at 14 ∞C; each root-tip squash was prepared in 75% acetic acid. Ten scorings were made from each slide and the 4C DNA content was estimated from metaphase chromosomes using a NIKON Optiphot microscope with a microspectrophotometer following the method of Sharma and Sharma (1980) with monochromatic light at 550 nm. In situ DNA values were obtained on the basis of optical density measurements which were converted to picograms (pg) using Vant Hoff&apos;s 4C nuclear DNA value (67.1 pg) for Allium cepa as standard Isolation of DNA Total plant DNA was isolated from fresh and young leaves. The leaves were harvested freshly and washed thoroughly with cold autoclaved distilled water and then blotted to dry. About 2 g leaf was excised from the upper tip portion of the buds. DNA extraction was done on the day of collection. The genomic DNA was isolated following the protocol of Doyle and Doyle (1990) with a little modification. Insoluble poly(vinylpyrrolidone) was added to the leaf tissue prior to grinding. The crude DNA was purified with RNase A (@ 60 µg ml Ð1 of DNA solution) followed by washing with S. Nayak et al. · Genetic Diversity among Ginger Cultivars 487 purified chloroform/isoamylalcohol (24:1). To test the quality and quantity of the purified DNA, the samples were electrophoresed in a 0.8% agarose gel along with a known amount of uncut lambda DNA (Bangalore Genei Pvt. Ltd, Bangalore, India) as standard. The sample DNA was diluted as 25 ng µl Ð1 for RAPD-PCR analysis. RAPD amplification Twenty random decamer primers (Operon Tech., USA) from A, C, D and N series (OPA02, 03, 04, 08, 16; OPAF14; OPC02, 05; OPD03, 07, 08, 18, 20; and OPN02, 03, 04, 06, 07, 10, 12) were used for RAPD analysis. RAPD assays were performed in a final volume of 25 µl containing 10 mm Tris-HCl [tris(hydroxymethyl)aminomethane], pH 9.0, 1.5 mm MgCl 2 , 50 mm KCl and 0.01% gelatin, 200 µm of each dNTPs, 0.4 µm primer, 25 ng template DNA and 0.5 unit of Taq DNA polymerase (Bangalore Genei, Bangalore, India). The RAPD analysis was performed as per the methodology described by The amplification products were electrophoresed in 1.5% agarose gel containing ethidium bromide (@ 0.5 µg ml Ð1 ) in TAE buffer (40 mm Tris base, 20 mm sodium acetate, 20 mm EDTA, glacial acetic acid to pH 7.2) for 3 h at 60 V. A total of 2.5 µl loading buffer (1.0 X TAE, 50% glycerol, 0.25% bromophenol blue and 0.25% xylene cyanol) was added to each reaction before electrophoresis. After electrophoresis, the gels were observed under an UV-transilluminator, documented in Gel-Doc 2000 (Bio-Rad) and photographed. Resolving power According to Prevost and Wilkinson (1999) the resolving power (Rp) of a primer is: Rp = Σ IB, where IB (band informativeness) takes the value of: 1-[2 ¥ (0.5 Ð p)], p being the proportion of the 16 genotypes (ginger cultivars analyzed) containing the band. Data collection and analysi

Proceedings of the Sixth International Workshop on Web Caching and Content Distribution

OVERVIEW The International Web Content Caching and Distribution Workshop (WCW) is a premiere technical meeting for researchers and practitioners interested in all aspects of content caching, distribution and delivery on the Internet. The 2001 WCW meeting was held on the Boston University Campus. Building on the successes of the five previous WCW meetings, WCW01 featured a strong technical program and record participation from leading researchers and practitioners in the field. This report includes all the technical papers presented at WCW'01. Note: Proceedings of WCW'01 are published by Elsevier. Hardcopies of these proceedings can be purchased through the workshop organizers. As a service to the community, electronic copies of all WCW'01 papers are accessible through Technical Report BUCS‐TR‐2001‐017, available from the Boston University Computer Science Technical Report Archives at http://www.cs.bu.edu/techreps. [Ed.note: URL outdated. Use http://www.bu.edu/cs/research/technical-reports/ or http://hdl.handle.net/2144/1455 in this repository to access the reports.]Cisco Systems; InfoLibria; Measurement Factory Inc; Voler

Acharya A. Multiplayer networked gaming with the session initiation protocol. Elsevier Computer Networks 2005

been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). Copies may be requested from IBM T. J. Watson Research Center, P