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Now showing items 1 - 15 of 15

  • Hierarchical Slotted Wireless Random Channel Access with Power Control

    Karouit, Abdelillah   Orozco Barbosa, Luis   Ramirez-Mireles, Fernando   Haqiq, Abdelkrim  

    This paper introduces a hierarchical Wireless Random Access scheme based on power control where intelligence is split among the mobile users in order to drive the outcome of the system towards an efficient point. The hierarchical game is obtained by introducing a special user who plays the role of altruistic leader whereas the other users assume the role of followers. We define the power control scheme in such a way that the leader first chooses the lowest power to transmit its packets among.. available levels whereas the followers re-transmit by randomly choosing a power level picked from N - 1 higher distinct power levels. Using a 3D Markovian model, we compute the steady state of the system and derive the average system throughput and expected packet transmission delay. Our numerical results show that the proposed scheme considerably improves the global performance of the system avoiding the well known throughput collapse at high loads commonly characterizing most random channel access mechanisms.
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  • A Novel Multicast Collision Prevention Mechanism for IEEE 802.11

    Angeles Santos, M.   Villalon, Jose   Ramirez-Mireles, Fernando   Orozco-Barbosa, Luis   Delicado, Jesus  

    In this letter, we introduce a novel Multicast Collision Prevention (MCP) mechanism for IEEE 802.11 WLANs. The proposed MCP mechanism has been designed following the operation principles of the IEEE 802.11 standard. Our analysis shows that the proposed MCP mechanism effectively improves the reliability and efficiency of the multicast mechanism defined by the IEEE 802.11 standard. Simulation results also show that our proposal properly interoperates with the 802.11 unicast mechanism.
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  • A Case Study on the Power-Aware Protocol Framework for Wireless Sensor Networks

    Diaz, Pedro   Royo, Fernando   Olivares, Teresa   Ramirez-Mireles, Fernando   Orozco-Barbosa, Luis  

    The proliferation of wireless sensor networks is one of the main hardware components enabling the creation of the Internet of Things. As sensor nodes are being deployed in a wide variety of indoor and outdoor environments, they are in general battery-powered devices. In fact, power provisioning is one of the main challenges faced by engineers when deploying IoT-based applications. This paper develops crosslayer architecture, integrating smart and power-aware protocols with a low-cost and high-efficiency power management module, which is the basis of long-lasting of self-powered WSNs. The main physical components of the proposed architecture are a wireless node comprising a set of small solar cells responsible for harvesting the energy and an ultracapacitor as storage device. Energy consumption is reduced significantly by varying the sleep/wake duty cycle of the radio module. For environments with only a few hours of sunlight per day we present the feasibility of ensuring long-lasting operation by means of adapting the duty cycle scheme according to the energy stored in the ultracapacitor. Our experiments prove the feasibility of a long-endurance outdoors operation with a low-complexity power management unit. This is an important advance towards the development of novel IoT-based applications.
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  • UWB-FSK: Performance Tradeoffs for High and Low Complexity Receivers

    Ramirez-Mireles, Fernando   Cooklev, Todor   Paredes-Orozco, Gustavo A.  

    In this work we explore flexible modulations to allow demodulation using receivers with different complexity and cost. More specifically, we study pulse-based ultra wideband (UWB) communications over channels with dense multipath effects using frequency shift keying (FSK) data modulation. Our aim is to explore the performance tradeoffs between high and low complexity receivers. For this purpose we determine the performance of coherent, non-coherent and mismatched (e. g., non-coherent detection using templates consisting of a single path) demodulators. We take into account the influence of the frequency response of the antenna system and the effects of the frequency selectivity of the multipath channel. Given a specific channel condition, we derive expressions for the bit error rate for coherent, non-coherent and mismatched reception of correlated FSK signals with unequal energies, and calculate the signal-to-noise ratio (SNR) degradation for different receiver's complexities with a given FSK frequency deviation We show that UWB-FSK has a SNR degradation similar to other low-complexity receivers studied in the literature(1).
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  • Some M-ary Sequence Designs for Pulse-Based UWB and Other Systems Based on PPM

    Ramirez-Mireles, Fernando  

    This paper describes various block waveform encoded (M-ary) signal designs using pulse-position-modulation (PPM) that are useful in pulse-based ultra wideband (UWB) communications in wireless, cable and twisted-pair wire channels, and in other systems based on PPM (not necessarily of UWB nature). This work is focused in four interesting M-ary PPM signal designs: Orthogonal, Equicorrelated, N-orthogonal, and Generic Correlation designs. The designs are based on algebraic constructions with favorable correlation properties, mapping the algebraic constructions into sequences of time shifts to get PPM signals with good correlation properties. For each signal design, the normalized correlation properties are described, the design method is given, and examples of the designs are presented.
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  • Performance of UWBSSMA using orthogonal PPM-TH over dense multipath channels

    Ramirez-Mireles, Fernando  

    In this work we study ultra wideband (UWB) communications over dense multipath channels using orthogonal pulse position modulation (PPM) for data modulation and time-hopping (TH) for code modulation. We consider the effects of the multiple access interference (MUI) in asynchronous spread spectrum multiple access (SSMA) based on random TH codes. We use a realistic multipath channel to analyze the effects of the transmission rate in the number of users for different bit error rate (BER) values.
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  • Quantifying the degradation of combined MUI and multipath effects in impulse-radio UWB

    Ramirez-Mireles, Fernando  

    We study pulse-based ultra wideband (UWB) communications over multipath channels using asynchronous spread spectrum (SS) multiple access (MA) based on time-hopping (TH) and pulse position modulated (PPM) signals. More specifically, we analyze the signal-to-interference (SIR) degradation in the presence of additive white Gaussian noise (AWGN), multi-user interference (MUI), and dense multipath effects (DME) with line-of-sight (LOS) and non-line-of-sight (NLOS). In particular, we define a degradation margin factor for the combined MUI and multipath effects and also find an expression for the maximum number of simultaneous radio links N-u in terms of the operating SIR, the SS processing gain, and the bit transmission rate R-b. We consider both cases with perfect and imperfect power control.
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  • A Team Study of a Multiple-Power Wireless Random Channel Access Mechanism with Capture Effect

    Karouit, Abdelillah   Sabir, Essaid   Ramirez-Mireles, Fernando   Orozco Barbosa, Luis   Haqiq, Abdelkrim  

    We present a team analysis of a slotted random wireless channel access mechanism. Under the proposed scheme, denoted wireless random access mechanism with multiple power levels (MPL-WRA), each mobile station contends for a transmission opportunity following the principles of a slotted access mechanism incorporating a random transmitting power value selected among various available power levels. In this way, a capture effect may be produced allowing the packet to be decoded whenever the signal-to-interference-plus-noise ratio is higher than a given threshold. In order to analyze the performance and optimization of the proposed setup, we build aMarkovian model integrating the wireless access mechanism supplemented by the use of multiple power levels in an attractive and simple cross-layer fashion. We follow a team problem approach allowing us to fine tune the design parameters of the overall system configuration. Throughout an extensive numerical analysis, our main results set the basis for the social optimal system configuration of the proposed mechanism taking into account the physical constraints of using multiple power levels and the actual practical implementation of a slotted access mechanism. We end the paper with concluding remarks and future research directions including guidelines for the actual implementation of our proposal.
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  • Outage Capacity for Secondary Users Due to Bandwidth Fluctuations: Multicarrier Versus Single Carrier

    Ramirez-Mireles, Fernando  

    In this work we study the channel capacity from the point of view of a secondary user that shares the bandwidth of the channel with a primary user using dynamic spectrum access in cognitive radio.The secondary user sees bandwidth fluctuations (i.e, at any given time the bandwidth can be available or not) that impact its channel capacity. We study the outage capacity for the secondary user considering two scenarios in which the secondary user uses either a single carrier modulation for the case in which bandwidth fluctuates over the complete transmission band, and a multicarrier modulation for the case in which bandwidth fluctuations are over various transmission subbands. We derive expressions for the outage capacity of the secondary user for both single carrier and multicarrier. Results show that: (1) The outage capacity for single carrier can be higher than for multicarrier, but with a higher outage probability for single carrier than for multicarrier. In fact, a low value of outage probability for single carrier requires a duty cycle for the secondary user close to one, but this has the problem that it leaves a very short duty cycle for the primary user. (2) Although for the secondary user the outage capacity for multicarrier is smaller than for single carrier, for multicarrier lower values of the outage probability can be achieved even for short values of the duty cycle of the secondary user, allowing larger duty cycle values of the primary user. (3) For multicarrier, the outage capacity is more sensitive to changes in the duty cycle than to changes in the outage probability. To obtain a larger outage capacity with low values of both the outage probability and the duty cycle, it requires the use of a large number of subbands.
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  • [IEEE IEEE Globecom 2006 - San Francisco, CA, USA (2006.11.27-2006.12.1)] IEEE Globecom 2006 - WLC26-5: An Investigation of Antenna and Multipath Effects on Pulse-Based UWB Using FSK

    Ramirez-Mireles, Fernando   Cooklev, Todor  

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  • [IEEE Electronics, Robotics and Automotive Mechanics Conference (CERMA'06) - Cuernavaca, Morelos (2006.9.26-2006.9.26)] Electronics, Robotics and Automotive Mechanics Conference (CERMA'06) - Patents in Telecommunications Standards

    Ramirez-Mireles, Fernando  

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  • [IEEE 2013 IEEE Latin-America Conference on Communications (LATINCOM) - Santiago, Chile (2013.11.24-2013.11.26)] 2013 IEEE Latin-America Conference on Communications - Dynamic multiple access efficiency of Aloha and UWB with and without detect and avoid

    Ramirez-Mireles, Fernando  

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  • [IEEE MILCOM 2012 - 2012 IEEE Military Communications Conference - Orlando, FL, USA (2012.10.29-2012.11.1)] MILCOM 2012 - 2012 IEEE Military Communications Conference - Analysis of M-ary UWB FSK detected using two passband filters considering antenna and multipath effects

    Ramirez-Mireles, Fernando  

    We study ultra wideband (UWB) communications over dense multipath channels with M-ary frequency shift keying (FSK) data modulation and low complexity receivers. We model the signal transmission-reception taking into account the effects of both the frequency response of the antenna system and the frequency selectivity of the multipath channel. We derive an expression for the bit error rate (BER) when detection is achieved using a pair of passband filters. While other low complexity binary receivers reported in the literature present a large signal-to-noise ratio (SNR) degradation with respect to the binary coherent detection, using our signal design and filter-based detection the loss with respect to the binary coherent detection is only 3.5 dB using a binary receiver with no channel estimation.
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  • [IEEE MILCOM 2008 - 2008 IEEE Military Communications Conference (MILCOM) - San Diego, CA, USA (2008.11.16-2008.11.19)] MILCOM 2008 - 2008 IEEE Military Communications Conference - Analysis of filter-based non-coherent detection of UWB FSK with antenna and multipath effects

    Ramirez-Mireles, Fernando   Cooklev, Todor   Sablatash, Michael  

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  • [IEEE 2008 5th International Conference on Electrical Engineering, Computing Science and Automatic Control (CCE) - Mexico City, Mexico (2008.11.12-2008.11.14)] 2008 5th International Conference on Electrical Engineering, Computing Science and Automatic Control - Testing the Gaussianity of UWB TH-PPM MUI with imperfect power control and multipath

    Ramirez-Mireles, Fernando   Almada, Angel  

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