Nowadays IEEE 802.11 wireless local area networks (WLANs) support multiple transmission rates. To achieve the best performance, transmitting stations adopt the various forms of automatic rate fallback (ARF). However, ARF suffers from severe performance degradation as the number of transmitting stations increases. In this paper, we propose a new rate adaptation scheme which adjusts the ARF’s up/...

Based on Stanek’s results [1] we know that in model with integer rate PGV like compression functions no high speed collision resistant compression functions exist. Thus we try to study more general multiple block ciphers based model of compression functions with rational rate, like 6/5. We show a new upper bound of the rate of collision resistant compression functions in this model. 1 Motivatio...

The 802.11 MAC protocol used in Mobile Ad Hoc Networks is designed to eliminate the hidden node problem through the use of the four way handshake RTS/CTS/DATA/ACK and to reduce packet drops due to collisions by listening to the channel before transmitting data. However, this protocol can lead to unfair channel utilisation among different flows, as some of the nodes may capture the channel for a...

OBJECTIVES Initiatives to increase active school transportation are popular. However, increased walking to school could increase collision risk. The built environment is related to both pedestrian collision risk and walking to school. We examined the influence of the built environment on walking to school and child pedestrian collisions in Toronto, Canada. METHODS Police-reported pedestrian c...

This paper proposes a construction for collision resistant 2n-bit hash functions, based on n-bit block ciphers with 2n-bit keys. The construction is analysed in the ideal cipher model; for n = 128 an adversary would need roughly 2 units of time to find a collision. The construction employs “combinatorial” hashing as an underlying building block (like Universal Hashing for cryptographic message ...

Langevin described a model for the interaction between an ion and a neutral nearly a century ago and since then, many modifications have been introduced to adjust for specific circumstances. This work discusses the induced dipole–induced dipole interaction between an ion and a neutral without a permanent dipole and introduces an anisotropic adjustment. A point polarizable ion model (PPI) and an...

In Wireless Local Area Network, wireless node will suffer due to the hidden terminal node. This hidden terminal node leads to high collision, high drop rate of packets and high delay. To avoid this hidden terminal node, wireless nodes use the control messages to know the status of the destination nodes. Another issue in the WLAN is less coverage range with lesser number of nodes. To increase th...

The security of iterated hash functions relies on the properties of underlying compression functions. We study highly efficient compression functions based on block ciphers. We propose a model for highrate compression functions, and give an upper bound for the rate of any collision resistant compression function in our model. In addition, we show that natural generalizations of constructions by...

Cross sections and rate constants for total elastic, diffusion and transfer of metastability for collisions between He(11S)–He(23S) and He(11S)–He(23P) atoms over a wide range of energies and temperatures are presented. The rate constant for spin metastability excitation in He(11S)–He(23P) collision is several orders of magnitude larger than that for He(11S)–He(23S) collision at cold temperatur...