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In order to counteract hostile communication based on the advanced Orthogonal Frequency Division Multiplexing (OFDM) technology, an efficient and unrecognizable jamming technique by failing the OFDM cyclic prefix (CP) functionality is developed in the paper. CP is introduced into OFDM systems to prevent interference caused by the multipath fading, as long as it is no shorter than the channel delay...
Military communications face increasingly congested environments requiring spectrally efficient approaches capable of contending with many users and interference. We evaluate the over-the-air performance of recently designed minimum total squared correlation (MinTSC) signature sets compared to maximal length pseudorandom binary spreading sequences (m/PN) under a variety of interference conditions...
As professional mobile radio (PMR) networks evolve to a new generation based on Long Term Evolution (LTE), a new direct communication mode needs to be developed. Not only in PMR networks, but the increase of proximity services due to the explosion of the internet of things bring us to a new communication paradigm. The PMR users have very specific requirements and one of those is the ability to communicate...
In this paper, we focus on a X channel; a system with two transmitters and two receivers each equipped with a single antenna, where independent messages need to be conveyed over channels from each transmitter to each receiver. A key concept of that arises in the context of the X channel is interference alignment (IA) that refers to an overlap of signal spaces occupied by undesired interference at...
Cooperative Multiple Point (CoMP) transmission aided Distributed Antenna Systems (DAS) are proposed for increasing the received Signal-to-Interference-plus-Noise-Ratio (SINR) in the cell-edge area of a cellular system employing Fractional Frequency Reuse (FFR) in the presence of realistic imperfect Channel State Information (CSI) as well as synchronisation errors between the transmitters and the receivers...
Low-Rate Wireless Personal Area Network (LR-WPAN) technologies are more widely applied in industrial applications, posing additional challenges for reliability due to harsh conditions. Efficient and manageable testing methods and tools to support building and maintaining reliable communication are inevitable though currently not so well existing. The goal of our work is to derive a systematic approach...
In cognitive radio networks, secondary users conduct local sensing to use underutilized spectrum bands. However, every secondary user's local sensing usually gives rise to much sensing overhead. Moreover, a globally synchronized quiet period cannot be determined in a decentralized network. In this paper, we propose a zone-based distributed sensing scheme, in which multiple secondary users alternate...
For non-contiguous OFDM (NC-OFDM) based cognitive radio (CR) systems, one of huge challenges is to establish spectrum synchronization before data transmissions. In this paper, we propose a novel active subchannel detection scheme for the NC-OFDM receiver without out-of-band spectrum synchronization information. The key idea of the proposed scheme is to employ the received training symbol to calculate...
In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system for the future aeronautical communication infrastructure. This infrastructure is being developed within the International Civil Aviation Organization since 2004, to accommodate the air traffic load and improve the aerial security. The system presented in this paper is one of the two preselected proposals for the...
This paper addresses the effect of timing synchronization errors for two different multicarrier techniques CPOFDM and FBMC. Such errors degrade the performance of the reference receiver by causing multi user interference. This interference occurs when the signals from different transmitters arrive at a given receiver with arbitrary timing misalignments, leading to the destruction of orthogonality...
In this paper, a novel scheme for achieving fast synchronization in interleave division multiple access (IDMA), called spreading-IDMA (S-IDMA), is investigated. By introducing an extra despreader after the interleaver, S-IDMA can exploit the advanced techniques from code division multiple access (CDMA) and derives signal to interference-plus-noise ratio (SINR) improvement before iteration detection...
A short-range 1 Mb/s 3.8 GHz IR-UWB transceiver in 90 nm CMOS uses 1.5 pulse/bit synched-OOK modulation, enabling low-complexity 200 pJ/b digital demodulation and synchronization. An interference-robust asynchronous energy detector receiver can tolerate interferers up to -5 dBm. The power-gated oscillator-based transmitter has a power efficiency of 10.4%.
The paper deals with femtocell in context of next generation wireless systems. Actually, in the framework of the ITU, the definition of IMT.ADVANCED systems is on-going and all the candidates already investigate the usage of femtocells to improve system capacity. On the other hand, femtocell market is still at its early stage, facing the competition of low-cost, easy to use WiFi equipments. This paper...
In this paper we consider a multiuser DS-PPM UWB transmission system with comb filter based energy detection and its improvement for the case of interchip and interuser interference. DS-PPM UWB provides good performance in WBAN environments under the assumption that the channel dispersion is shorter than one chip period. The performance could be highly degraded if this assumption is violated. To cope...
One of the major challenges to cognitive radios is the synchronization of distributed radios onto the same spectrum white spaces which vary in time and space. In this paper, we propose a frequency-hopping spread spectrum transmission scheme which works reliably without any a priori handshaking assumption. Each cognitive radio independently detects white spaces, and then selects one of them to transmit...
With collaborative transmission we propose a novel transmission scheme that utilizes constructive interference between transmitted signals of wireless sensor nodes. Similar to cooperative transmission approaches we are able to drastically extend the transmission range of a wireless sensor network. We show that synchronization of received signal components is feasible without inter-node communication...
There is a general belief that in CSMACA-based wireless sensor networks (WSN) a significant number of collisions happen only because of hidden terminals. The situation when nodes start transmissions almost at the same time is considered negligible. Our experiments with motes with CC2420 radio shows that a significant number of collisions can occur even when transmitters can hear each other. The CCA...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
We propose QUEST (QUality ESTimation), a new method that accurately estimates IEEE 802.11 wireless link quality with no in-band signaling overhead. Existing link quality estimation methods either are based on hello exchanges by fixing or varying transmission rates or rely on the history (e.g., delivery ratio) of previously sent data packets in a per-rate/-neighbor manner. QUEST on the other hand,...
This paper deals with the chip-level equalization technique for large area synchronized-code division multiple access (LAS CDMA) system communications. In the downlink of LAS CDMA, frequency-selective multi-path channel often destroys the orthogonality of spread codes at receivers between users and introduces inter-path interference (IPI), inter-symbol interference (ISI) and multi-path access interference...
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