Free space optic communications – a review of quality parameters

The optical telecommunications have paved the way for a massive expansion in global telecommunications networks over the past few decades. There has been a tremendous explosion in bandwidth demand and requirements. For the end user to access and utilize the broad array of services made available through these developments, network designers must provide a flexible and cost-effective solution for the "last mile" between the LANs, MANs, or WANs. High bandwidth, rapid installation, higher security, and non-binding accessibility are some of the features that describe Free Space Optical (FSO) Technology. As such, FSO would be able and solve many problems faced by today's traditional wireless communications, from security, bandwidth limitations to last mile problem. Considering that FSO Technology uses optical signals, the performance of FSO links happen to be highly dependent on weather conditions more than microwave radio link

Performance evaluation of Free-Space-Optic (FSO) links

Once the knowledge about the basic performance parameters is gained it is possible to evaluate the performance of FSO links. Such is done firstly by evaluating all possible losses present in the channel, such as geometric, atmospheric and optical losses [1, 2]. Geometric losses are greatly dependent on the divergence angle and distance while atmospheric losses are created due to the signal's weakening due to atmospheric influence, or due to external performance factors mentioned earlier [3, 4]. Optical losses on the other hand are due to the physical configuration of each FSO terminal, and in some cases are negligible, as will be explained later in text. Knowing the losses or attenuation within the channel it is then possible to evaluate received power level and link margin, the main figures needed in order to evaluate the performance ofFSO link

Reliability evaluation of scalable complex networks through delta-star conversion

Exact reliability evaluation of large size complex networks becomes intractable with conventional techniques due to the exponential scaling of the computation complexity as the size of network scales up. In this paper we develop a scalable model for the exact evaluation of system reliability of scalable complex networks of the n-tuple bridge type based on scaled delta-star conversion. The number of steps as well as the computation overhead is kept within practical limits as they scale up linearly with the size of the network. The proposed model enables simple numerical evaluation either manually or through spread-sheets

Recovery modeling in MPLS networks

Transmission of QoS based traffic over packet switched network typically requires resource reservation or differentiated treatment to guarantee an acceptable level of performance. But it is also essential to bound the disruption caused by failure of nodes or links for a real time traffic to a limit that is acceptable by the application. In this paper, a simulation platform models the impact of the MPLS recovery/protection schemes on the QoS traffic parameters including disruption time and number of out of order packets arriving at the destination. The simulation considers measures to alleviate drawbacks caused by recovery process

Enhancement of bluetooth security authentication using hash-based message authentication code (HMAC) algorithm

Recently, Bluetooth technology is widely used by organizations and individuals to provide wireless personal area network (WPAN). This is because the radio frequency (RF) waves can easily penetrate obstacles and can propagate without direct line-of-sight (LoS). These two characteristics have led to replace wired communication by wireless systems. However, there are serious security challenges associated with wireless communication systems because they are easier to eavesdrop, disrupt and jam than the wired systems. Bluetooth technology started with a form of pairing called legacy pairing prior to any communication. However, due to the serious security issues found in the legacy pairing, a secure and simple pairing called SPP was announced with Bluetooth 2.1 and later since 2007. SPP has solved the main security issue which is the weaknesses of the PIN code in the legacy pairing, however it has been found with some vulnerabilities such as eavesdropping and man-in-the-middle (MITM) attacks. Since the discovery of these vulnerabilities, some enhancements have been proposed to the Bluetooth Specification Interest Group (SIG) which is the regulatory body of Bluetooth technology; nevertheless, some proposed enhancements are ineffective or are not yet implemented by Manufacturers. Therefore, an improvement of the security authentication in Bluetooth connection is highly required to overcome the existing drawbacks. This proposed protocol uses Hash-based Message Authentication Code (HMAC) algorithm with Secure Hash Algorithm (SHA-256). The implementation of this proposal is based on the Arduino Integrated Development Environment (IDE) as software and a Bluetooth (BT) Shield connected to an Arduino Uno R3 boards as hardware. The result was verified on a Graphical User Interface (GUI) built in Microsoft Visual Studio 2010 with C sharp as default environment. It has shown that the proposed scheme works perfectly with the used hardware and software. In addition, the protocol thwarts the passive and active eavesdropping attacks which exist during SSP. These attacks are defeated by avoiding the exchange of passwords and public keys in plain text between the Master and the Slave. Therefore, this protocol is expected to be implemented by the SIG to enhance the security in Bluetooth connection

Availability analysis of terrestrial free space optical link under the impact of rain condition

Availability is one of the main factors to measure the QoS of any telecommunication networks. An accurate availability prediction for Free Space Optical link of carrier class grade is needed. In tropical areas, rain is the most dominant factor affecting the FSO link availability. In this paper, the effect of rain attenuation on the availability of FSO links is analyzed by examining the impact distance of different FSO systems. As the rain attenuation of FSO is independent of wavelength, the analysis of rain attenuation will be based on rain intensity. ITU-R (Carbonneau and Japan) models have been used for the analysis. From the results; Carrier class availability with good enough resolution for estimated availability can be predicted. This paper provides recommendations to FSO researchers in general and local telecom service provider in particular about possible availability figures that can be useful for deployment of FSO link as a last mile solution, back-up for fiber optic and other applications

Atmospheric effects on free space earth-to-satellite optical link in tropical climate

Free Space Optic (FSO) vulnerability towards atmospheric phenomena is becoming a main issue towards its implementation. A lot of studies have been conducted to estimate the climatological effects on FSO links but most of them are based on terrestrial link with short path lengths and centred in temperate regions.Hence, this paper aims to analyse the performance of FSO links from earth-to-LEO satellite in tropical regions where rain and haze are the main concerns. This analysis is based on available methods and data to predict earth-to-satellite FSO links with the scaled up data from the measurement on terrestrial FSO link installed at International Islamic University Malaysia (IIUM) Kuala Lumpur campus. Data collected from terrestrial link are FSO received signal levels, corresponding rain intensity and visibility variations. The measured data are scaled up to the effective distance of slant path lengths and then compared with the predicted values. These findings will be very useful for FSO earth-space communication link designers and can be as a benchmark of FSO system design

Design and performance analysis of multiple transmitters/receivers on Free Space Optics(FSO) link

Free Space Optics is the concept of transmitting very high bandwidth information using the optical beam from one point to another through the atmosphere. This technology offers various advantages to both telecommunication users and providers. It provides a high data rates up to several Gbps, has immunity to radio frequency interferences, requires no licensing, gives a highly secured communication link due to the usage of a very narrow beam angle, and offers an inexpensive, fast and easy deployment when compared to the fiber optic installatio