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...icant amount of research, devoted to their modeling, analysis and evaluation. Early work modeled 802.11 MAC layer using Markov chains and developed an analytical formulation for saturation throughput =-=[10]-=-. Despite the CHAPTER 4. SWIFI: WI-FI NETWORK ANALYSIS WITH SDR 87 elegant formulation and analytical power, these results were limited to a simple interference model that assumes that all nodes are w...

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...ated. Rate Adaptation Algorithms (RAA) adjust the physical layer transmission rate to the channel characteristics; ideally selecting a low rate MCS for a low SNR channel and a high rates for high SNR =-=[11, 51, 58, 61, 68, 71, 79, 117, 120]-=-. To illustrate the criticality of hiding the communication rate, we first provide some insights into rate adaptation attacks. The key idea in the highly efficient RAA-attack is to force a device to u...

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... the interleaving functions are generated using a key-hashed pseudorandom function h with secret key K applied on the packet number s and block index i, the coefficients A and B are indistinguishable =-=[7]-=-, thus the interleaved symbol sequences are also indistinguishable.The header is also semantically secure due to the use of random R with AES encryption. CHAPTER 3. CBM – CONCEALING RATE INFORMATION A...

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...a new seed for every block of coded symbols. Alternatively, another FPE approach called prefix cipher can be used, where symbol indices are encrypted and then ranked to produce a new ordered sequence =-=[12]-=-. Nevertheless, this provably-secure solution requires more overhead with m operations required per m-symbol block plus m logm comparisons for ranking. In the following, we will describe our solution,...

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...loped at the physical layer [104] include directional antennas [60], spread spectrum communication, and power, modulation, and coding control. More recently, research has also addressed higher layers =-=[4, 9, 25, 29, 41, 56, 59, 66, 67, 86, 105, 107, 108, 119, 122, 123]-=-. However, given the ease of building high power jamming devices, there is still a strong need for efficient and flexible techniques operating at the physical layer. There is a demand for low-cost sol...

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...loped at the physical layer [104] include directional antennas [60], spread spectrum communication, and power, modulation, and coding control. More recently, research has also addressed higher layers =-=[4, 9, 25, 29, 41, 56, 59, 66, 67, 86, 105, 107, 108, 119, 122, 123]-=-. However, given the ease of building high power jamming devices, there is still a strong need for efficient and flexible techniques operating at the physical layer. There is a demand for low-cost sol...

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...ain b of the residual signal is considered as a new channel gain of the signal after removing the jamming signal. Therefore, the data can be decoded by the decoder with well-known decoding techniques =-=[16, 88]-=- in software-defined radio. Consequently, estimation of b is not required. 2.4.3 Practical Issues In practice, we need to address the issue of frequency offset between the received signals which are u...

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...ation accuracy because a channel distortion on training and pilot sequences results in a critical impact on the data subcarrier channel recoverability. The principle of Decision Directed equalization =-=[17, 92]-=- is to use the statistical characteristics of data subcarriers to estimate the channel. In particular, each subcarrier is decoded according to the known modulation of the current OFDM symbol, and the ...

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...signal identification and channel estimation. The closest related work to our approach consists of phased array antennas and MIMO systems. Phased array antennas were very well studied since the 1950s =-=[18, 19, 60, 111]-=-. Likewise, MIMO systems were also very well studied since the mid 90s [112]. Our design and approach have unique characteristics that distinguishes them from prior work. Similar performance phased ar...

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... devise explicit codes with higher coding gain than traditional codes conforming to uniformity. By Cryptographic Interleaving, CBM also helps mitigating passive attacks against users traffic analysis =-=[3]-=-. Our simulation results show that in most cases this modulation hiding scheme has the side effect of boosting resiliency by up to seven times in comparison to regular rate-exposing systems. However, ...

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...ignals to 4MHz) [6], several efforts have been made to enable Wi-Fi communications on low-cost SDR platforms such as the Utah University FPGA-assisted implementation [34], or the more recent attempts =-=[14, 15]-=-. However, to the best of our knowledge none of these platforms exceeds QPSK modulation in terms of design and have very limited performance even for these low rates. A unique characteristic of higher...

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...ignals to 4MHz) [6], several efforts have been made to enable Wi-Fi communications on low-cost SDR platforms such as the Utah University FPGA-assisted implementation [34], or the more recent attempts =-=[14, 15]-=-. However, to the best of our knowledge none of these platforms exceeds QPSK modulation in terms of design and have very limited performance even for these low rates. A unique characteristic of higher...

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... a $50 microwave oven’s magnetron that can generate a 1KWatt interfering signal (covering hundreds of meters) and can be tuned to a wide range of frequencies by slightly modifying its resonant cavity =-=[19, 83]-=-. In contrast, the communication nodes’ regulated power is usually limited to 100mW. This type of jamming can completely block the ongoing transmission between communication nodes. CHAPTER 1. INTRODUC...

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...tion of choice for anti-jamming, it suffers from a need for preshared secrets between the communicating nodes. Several solutions were recently proposed for alleviating the need for pre-shared secrets =-=[2, 22, 41, 56, 65, 67, 107, 108]-=-. However, they are not designed to tackle powerful jammers (meaning jammer with power 4-5 orders of magnitude higher than the transmitting node). Other recent work has demonstrated mechanisms for can...

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...ed for analyzing Wi-Fi networks in the wild. In parallel, several researchers developed measurement-driven approaches to analyze and experiment with dense Wi-Fi networks in real world setting such as =-=[20]-=-. Measurement-driven approaches to Wi-Fi led to better protocols for frequency/channel auto-configuration, load-balancing, powercontrol, and rate adaptation [73, 102, 121]. However, most of the early ...

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...the comeback to higher rates is slow. Finally, the equiprobability of transmission CHAPTER 1. INTRODUCTION 6 among devices enables the adversary to focus on a single link to degrade the whole network =-=[21]-=-. Previous work [74, 81, 86] demonstrated both analytically and experimentally that knowledge of the rate used in a transmission enables selective jamming of packets resulting in link degradation (e.g...