Nowadays, Wireless and mobile communications technologies are the most important areas, which are rapidly expanding
either in horizontal or vertical directions. WiMAX is trying to compete with WiFi in coverage and data rate, while the
inexpensive WiFi still very popular in both personal and business use. Efficient bandwidth usage, Multi-Standard
convergence and Wireless Mesh Networks (WMN) are the main vertical tends in the wireless world. WiMAX-WiFi
convergence as an ideal technology that provides the best of both worlds: WiMAX new features and the low cost of the
WiFi. In order to create a heterogeneous network environment, differences between the two technologies have been
investigated and resolved. In the Multi-Carrier WiMAX-WiFi Convergence, the mismatch between the fixed WiMAXOFDM
(Nfft=256) and the WiFi-OFDM (Nfft=64) has been confirmed as a physical layer issue that will never be solved as
MAC layer problem; therefore the current proposal is how to build what we called the "Convergence-Bridge". This
bridge is like an extra thin layer, which is responsible for harmonizing the mismatch. For the WiFi-OFDM physical
layer, the paper has selected the IEEE 802.11n OFDM standard while it is being developed. The proposal does not
suggest changing the standard itself but modifying some functions to be configurable. The IEEE 802.11 standard has
fixed the configurations for WiFi mode only, while our proposal is to set up these functions for WiFi and WiMAX
modes.
KEYWORDS: Network security, Information security, Computer simulations, Cryptography, Device simulation, Wireless communications, Mobile communications, Data transmission, Computer security, Mobile devices
Existing Ad Hoc routing protocols are mostly based on efficiency-driven protocols. Malicious nodes can easily impair
the performance of wireless ad hoc networks as a result of different actions such as packet dropping or black hole attacks
without being detected. It is virtually impossible to find out these kinds of malicious before they attack, therefore it
would be sensible to base detection of malicious nodes on post route discovery stage, i.e. when packets are transmitted
on discovered routes. In this paper we shall review existing techniques for secure routing and propose to use credibility
based route finding protocols. Each node would monitor its neighbors' pattern of delivering packets and regularly update
their "credibility" according to certain criteria. The level of trust in any route will be based on the credits associated with
the neighbor belonging to the discovered route. We shall evaluate the performance of the proposed scheme by modifying
our simulation system so that each node has a dynamic changing "credit list" for its neighbors' behavior. We shall
conduct a series of simulations with and without the proposed scheme and compare the results. We will demonstrate that
the proposed mechanism is capable of isolating malicious nodes and thereby counteracting black hole attacks. We will
discuss problems we encountered and our solutions. We would also further develop the protocol, to investigate the
possibility of using the unique prime factorization theory to enable nodes acquiring more trust knowledge beyond its
immediate neighborhood. Such an approach helps to further secure route-finding procedures.
Horizontal developments in communication systems have led to the emergence of new wireless technologies like
WiMAX, 3G and 4G. These expansions can provide new opportunities for further advances and exciting applications in
particular if we can integrate different technology standards into heterogeneous wireless networks. WiMAX and WiFi
wireless networks are two examples of different standard technologies that cannot communicate with each other using
existing protocols. These two standards differ in frequency, protocol and management mechanisms, and hence to
construct a heterogeneous network using WiFi and WiMAX devices these differences need to be harmonised and
resolved. Synchronization is the first step towards in such a process. In this paper we propose a private synchronization
technique that enables WiFi and WiMAX devices to communicate with each other. Precise time synchronization in the
micro second resolution range is required. The CPU clock is used as a reference for this private synchronization.
Our private synchronization solution is based on interposing an extra thin layer between MAC and PHY layers in both
WiFi and WiMAX. This extra thin layer will assign alternate synchronization and other duties to the two systems.
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