On adaptive frequency hopping to combat coexistence interference between bluetooth and IEEE 802.11b with practical resource constraints

In contrast to traditional frequency hopping techniques, Adaptive Frequency Hopping (AFH) is a low cost and low power solution to avoid interference dynamically. While each AFH algorithm proposed previously is shown to be efficient, a detailed performance analysis of various AFH mechanisms under realistic resource constraints is yet to be done. In particular, based on our performance study on Bluetooth systems presented in this paper, we have found that the AFH mechanism adopted by IEEE 802.15 Task Group 2 (TG2) is very sensitive to memory and power limitations. We then propose a novel Interference Source Oriented Adaptive Frequency Hopping (ISOAFH) approach based on a cross-layer design, in which the baseband layer of Bluetooth considers not only the instantaneous channels condition but also the physical layer transmission characteristics of potential interference sources in determining the hop sequence. In our simulations using detailed MATLAB Simulink modeling, we find that our proposed method is much more robust in that it is insensitive to memory and energy constraints. Indeed, our approach generally achieves a lower collision rate and higher ISM spectrum utilization.published_or_final_versio

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201

Regulatory and Policy Implications of Emerging Technologies to Spectrum Management

This paper provides an overview of the policy implications of technological developments, and how these technologies can accommodate an increased level of market competition. It is based on the work carried out in the SPORT VIEWS (Spectrum Policies and Radio Technologies Viable In Emerging Wireless Societies) research project for the European Commission (FP6)spectrum, new radio technologies, UWB, SDR, cognitive radio, Telecommunications, regulation, Networks, Interconnection

A performance study of packet scheduling algorithms for coordinating colocated Bluetooth and IEEE 802.11b in a Linux machine

Due to the proliferation of hand-held short-range communication devices, coexistence between Bluetooth and IEEE 802.11b has become a performance critical issue. In this study, we performed an actual implementation of a Linux based network access point (NAP), in which Bluetooth and IEEE 802.11b are colocated. Such a NAP is expected to be crucial in supporting 'hot-spot' systems targeted to serve nomadic users carrying either a Bluetooth or a IEEE 802.11b device. Specifically, the goal of our study is to investigate the efficacy of a software based interference coordination approach. We consider five most commonly used scheduling algorithms in a Linux environment. Our extensive experimental results obtained in a real environment indicate that a hierarchical scheduling approach exhibits the best performance in terms of aggregate bandwidth achieved by Bluetooth and IEEE 802.11b.published_or_final_versio

Survey of Spectrum Sharing for Inter-Technology Coexistence

Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and non-technical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e. (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions

Use of Time-Frequency Analysis and Neural Networks for Mode Identification in a Wireless Software-Defined Radio Approach

The use of time-frequency distributions is proposed as a nonlinear signal processing technique that is combined with a pattern recognition approach to identify superimposed transmission modes in a reconfigurable wireless terminal based on software-defined radio techniques. In particular, a software-defined radio receiver is described aiming at the identification of two coexistent communication modes: frequency hopping code division multiple access and direct sequence code division multiple access. As a case study, two standards, based on the previous modes and operating in the same band (industrial, scientific, and medical), are considered: IEEE WLAN 802.11b (direct sequence) and Bluetooth (frequency hopping). Neural classifiers are used to obtain identification results. A comparison between two different neural classifiers is made in terms of relative error frequency

Design of an Adaptive Frequency Hopping Algorithm Based On Probabilistic Channel Usage

Dealing with interference in the 2.4 GHz ISM band is of paramount importance due to an increase in the number of operating devices. For instance systems based on Bluetooth low energy technology are gaining lots of momentum due to their small size, reasonable cost and very low power consumptions. Thus the 2.4 GHz ISM band is becoming very hostile. Bluetooth specification enables the use of adaptive frequency hopping to improve performance in the presence of interference. This technique avoids the congested portions of the ISM band, however as the number of interferers increases for a given geographical environment, a greater number of bad channels are removed from the adapted hopping sequence. This results in longer channel occupancy, and consequently higher probability of collisions with coexisting devices, degrading their operation. At CoSa Research Group a novel algorithm, based on probabilistic channel usage of all channels (good and bad), is developed. The scheme is named Smooth Adaptive Frequency Hopping (SAFH) and uses an exponential smoothing filter to predict the conditions of the radio spectrum. Based on the predicted values, different usage probabilities are assigned to the channels, such as good channels are used more often than bad ones. The discrete probability distribution generated is then mapped to a set of frequencies, used for hopping. MATLAB/SIMULINK was used to investigate the performance of SAFH, in the presence of different types of interfering devices such as 802.11b , 802.15.4 and 802.15.1. Simulation study under different scenarios show, that our developed algorithm outperforms the conventional random frequency hopping as well as other adaptive hopping schemes. SAFH achieves lower average frame error rate and responds fast to changes in the channel conditions. Moreover it experiences smooth operation due to the exponential smoothing filter

Frequency hopping in wireless sensor networks

Wireless sensor networks (WSNs) are nowadays being used to collectively gather and spread information in different kinds of applications, for military, civilian, environmental as well as commercial purposes. Therefore the proper functioning of WSNs under different kinds of environmental conditions, especially hostile environments, is a must and a lot of research currently ongoing. The problems related to the initialization and deployment of WSNs under harsh and resource limited conditions are investigated in this thesis. Frequency hopping (FH) is a spread spectrum technique in which multiple channels are used, or hoped, for communications across the network. This mitigates the worst effects of interference with frequency agile communication systems rather than by brute force approaches. FH is a promising technique for achieving the coexistence of sensor networks with other currently existing wireless systems, and it is successful within the somewhat limited computational capabilities of the sensor nodes hardware radios. In this thesis, a FH scheme for WSNs is implemented for a pair of nodes on an application layer. The merits and demerits of the scheme are studied for different kinds of WSN environments. The implementation has been done using a Sensinode NanoStack, a communication stack for internet protocol (IP) based wireless sensor networks and a Sensinode Devkit, for an IPv6 over low power wireless personal area network (6LoWPAN). The measurements are taken from the developed test bed and channel simulator for different kinds of scenarios. The detailed analysis of the FH scheme is done to determine its usefulness against interference from other wireless systems, especially wireless local area networks (WLANs), and the robustness of the scheme to combat fading or frequency selective fading