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Distributed beamforming is a form of collaborative communication, in which wireless nodes adjust the phases of their transmitted signals so that the signals are combined coherently at the destination. This enhances the received signal power and extends the communication range. In this paper, we propose a transmit beamforming method that does not require any explicit feedback information from the receiver...
Frame Synchronization (FS) is required in several communication standards in order to recover the individual frames that have been aggregated in a burst. This paper proposes a low-delay and reduced-complexity Sliding Trellis (ST)-based FS technique, compared to our previously proposed trellis-based FS method. Each burst is divided into overlapping windows in which FS is performed. Useful information...
In wireless networks, it is important to determine the outcome of packet transmissions for networking protocols. In this paper, we design a transmission outcome classifier for IEEE 802.15.4 wireless networks based on received signal strength indicator and link quality indicator values. Our classifier performs loss differentiation by analyzing statistical differences between weak signal and collision...
Orthogonal Frequency Division Multiplexing (OFDM) uses pilot tones to estimate the channel's frequency response and perform equalization. It is commonly known that jamming pilot tones is more efficient than broadband attacks against an entire OFDM signal. This paper builds on this idea and introduces the pilot nulling attack, which is considerably more efficient than simple pilot jamming, by driving...
Interference at the radio receiver is a key source of degradation in quality of service of wireless communication systems. In this paper, we address the impact of imperfect inter-cell synchronization on the performance of orthogonal frequency division multiplexing (OFDM) and filter bank based multicarrier (FBMC) multi-cellular networks. Based on computing the moment generating functions of the asynchronous...
In multi-hop cooperative communications, multiple relay stations are used at each hop in order to enhance transmission performance. In previous studies, transceivers have been used to evaluate the transmission performance of multi-hop cooperative communications involving the use of a space-time block code, in real propagation channels. In the present study, an experiment involving multi-hop cooperative...
We study the capacity of discrete memoryless channels with synchronization errors and additive noise. We show that with very large alphabets, their capacity can be achieved by i.i.d. input sources, and prove tight lower and upper capacity bounds. An interesting result is that as long as the input sequences are not completely deleted, the capacity of channels with large alphabets corrupted by discrete...
In this paper, we introduce a low overhead scheme for the uplink channel allocation within a single cell of Cognitive Radio Wireless Mesh Network (CR-WMNs). The scheme does not rely on using a Common Control Channel (CCC). The mechanism is based on Physical layer Network Coding (PNC), in which two Secondary Users (SUs) are allowed to transmit synchronously over a randomly selected channel from a set...
This paper presents a novel SSS detection method for the second step of neighbor cell search in 3GPP LTE TDD systems. The proposed method is based on coherent detection and contains two stages. At the first stage, SSS is detected by using estimated channel response at PSCH. Owing to the difference of channels between PSCH and SSCH in TDD mode, the channel response estimated from PSCH does not exactly...
Current CSMA-based MAC protocols for wireless sensor networks (WSNs) do not support prioritized channel access and often suffer from varying degrees of starvation and fairness problems. That is, with a little bad luck, a sensor node might have to wait arbitrarily long to send its frame, and thus results in the invisibility of some sensed area. In this paper we introduce a simple, but yet well performing...
Long Term Evolution (LTE) physical layer identity can be recognized either in frequency domain or time domain. In this paper we serve some comparisons in term of complexity, latency, and recognition probability. As a result, frequency domain detection has superiority on performance for SNR higher than 3dB on all channel models, as well as lower latency than time domain scheme one. However, it requires...
A synchronization error is unavoidable in mobile wireless multihop networks, especially in sparse networks, due to the lack of effective synchronization algorithms. Fortunately, some level of clock synchronization is possible among nodes. In this paper, we propose a distributed semi-asynchronous sleep scheduling protocol (DSA) considering loosely synchronized clocks in sparse mobile wireless networks...
This paper proposes a game-theoretic approach to the problem of resource allocation for the uplink of a CDMA wireless communication network, in which terminals code-locked to the access point (in-sync users) coexist with some terminals still in the code acquisition stage (out-of-sync users). To capture the tradeoff between obtaining good performance and saving as much energy as possible for both classes,...
Synchronization in Decode and Forward (DF) cooperative communication systems is a complex and challenging task requiring estimation of many independent timing and carrier offsets at each relay in the broadcasting phase and multiple timing and carrier offsets at the destination in the relaying phase. This paper presents a scheme for blind channel, timing and carrier offset estimation in a DF cooperative...
A key issue in physical-layer network coding (PNC) is how to deal with the asynchrony between signals transmitted by multiple transmitters. That is, symbols transmitted by different transmitters could arrive at the receiver with symbol misalignment as well as relative carrier-phase offset. In this paper, 1) we propose and investigate a general framework based on belief propagation (BP) that can effectively...
In this paper, we present a dual-radio framework for implementing MAC protocols in wireless sensor networks. The framework is based on the observation that MAC operations can be categorized into time-dependent and bandwidth-dependent. Unlike existing dual-radio systems, we do not propose a new MAC protocol. Instead, we show how a given MAC protocol can be re-implemented using a dual-radio framework...
The support for mobility is a major requirement for the next Internet. Although several mobility solutions are proposed, none of them has been largely deployed, due to various impediments, among which, non being economically viable, we believe is the principal one. We propose a business oriented mobility framework - Mobility Support Service (MSS), that will facilitate mobility on the Internet. MSS...
In a typical macrocell network, all macrocell mobile stations (mMSs) are synchronized to the macrocell base station (mBS) during the uplink. The mMSs that are closer to the mBS transmit their signals at a later time instant so that signals of all the all mMSs arrive at the mBS at the same time. However, signals of the mMSs reach at the femtocell base stations (fBSs) with different delays, which may...
In vectored DSL systems, a disorderly leaving event (DLE) occurs when one user suddenly unplugs or turns off the CPE. The impedance on the CPE side is suddenly changed and it thereby changes the crosstalk channel from the disorderly leaving line to the other vectored lines. The mismatch between the precoder and the changed crosstalk channel could make some of the other vectored lines to retrain. However,...
In this paper we present an energy efficient priority based MAC protocol for Wireless Sensor Networks (WSNs). We abbreviate it as PRIMA. The PRIMA protocol consists of two phases; a clustering phase and a channel access phase. Clustering the senor network makes the MAC protocol to handle well network scalability issues. The channel access is composed of a hybrid mode of TDMA and CSMA. CSMA mode is...
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