De acuerdo con ciertas formas de realizacion, un metodo implementado en un dispositivo inalambrico (110A-C) para configurar brechas de medicion y conmutacion de senales de sonido de referencia (SRS) incluye obtener una primera... more
De acuerdo con ciertas formas de realizacion, un metodo implementado en un dispositivo inalambrico (110A-C) para configurar brechas de medicion y conmutacion de senales de sonido de referencia (SRS) incluye obtener una primera configuracion para transmitir al menos una primera senal radioelectrica sujeta a conmutacion SRS. Se obtiene una segunda configuracion que indica una brecha de medicion para recibir al menos una segunda senal radioelectrica. La primera configuracion esta adaptada para transmitir la al menos una primera senal radioelectrica sujeta a conmutacion SRS mientras se aplica la segunda configuracion. La al menos una primera senal radioelectrica sujeta a conmutacion SRS se transmite de acuerdo con la primera configuracion adaptada mientras se aplica la segunda configuracion.
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In a pre-coded Multi User Multiple Input Multiple Output (MU-MIMO) system, the channelization can be done either by using any of the two basic access tech-niques, namely Orthogonal Frequency Division Multiple Access (OFDMA) and Space... more
In a pre-coded Multi User Multiple Input Multiple Output (MU-MIMO) system, the channelization can be done either by using any of the two basic access tech-niques, namely Orthogonal Frequency Division Multiple Access (OFDMA) and Space Division Multiple Access (SDMA), or by combining them. From resource allocation point of view, choice of any technique will require different fairness conditions among users. In this paper, we have studied these different fairness conditions when combined with basic or joint access schemes mentioned above, while applied in a MU-MIMO based UTRA-LTE system. We have evaluated the resource allocation fairness issue when two well-known linear MU-MIMO precoding is used on a UTRA-LTE system. User grouping issue is dealt with when SDMA component is considered in the system. The results in this work provides an indicative analysis of the usability of different channelization techniques for considered system. I.
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In future Time Division Duplex (TDD)-based broad-band wireless systems, it will be possible to exploit the channel reciprocity to implement Channel State Information (CSI)-based Multi User Multiple Input Mul-tiple Output (MU-MIMO)... more
In future Time Division Duplex (TDD)-based broad-band wireless systems, it will be possible to exploit the channel reciprocity to implement Channel State Information (CSI)-based Multi User Multiple Input Mul-tiple Output (MU-MIMO) techniques, which will ensure highly efficient spectrum usage. To increase the cell cov-erage while ensuring the Quality of Service (QoS) for all UEs across the cell area, fairness should be maximized as much as possible. This paper presents a novel way to help improving fairness performance in the physical layer, via fair power allocation together with resource allocation, in MU-MIMO precoding scenarios where the common approach of guaranteeing fairness at MAC layer is not feasible. The results presented in this paper show that the proposed algorithm is able to reduce the system outage event to a large extent, thus increases fairness. I.
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and other research outputs Impact of nonlinear power amplifier on link adaptation algorithm of OFDM systems Conference Item How to cite:
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In an Orthogonal Frequency Division Multiplexing (OFDM) system, downlink beamforming can be implemented either before IDFT (frequency domain) or after IDFT (time domain) module in a base station transmitter. We denote the former scheme as... more
In an Orthogonal Frequency Division Multiplexing (OFDM) system, downlink beamforming can be implemented either before IDFT (frequency domain) or after IDFT (time domain) module in a base station transmitter. We denote the former scheme as PreIDFT downlink beamforming, and the latter as Post-IDFT downlink beamforming. In this work, we have compared Pre-IDFT downlink beamforming with Space-Time Block coded and Space-Frequency block coded transmit diversity schemes for 4× 1 downlink multi-user OFDM (OFDM-TDMA and OFDMA) systems. The study is performed for indoor micro and pico cells and urban macro cells. Regardless of the multiple access scheme, it is found that beamforming always performs better in outdoor environment, where angular spread is lower, thus spatial correlation is higher. Similarly, indoor environment (high angular spread and low spatial correlation) suggests that transmit diversity schemes performs better than beamforming strategies. Keywords— Multi-user OFDM, Beamformi...
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An anti-blocking agent comprising silicon dioxide or mixtures of silicon dioxide and zeolite is described, which is characterized in that it has a bimodal pore size distribution, the first maximum of the bimodal pore size distribution... more
An anti-blocking agent comprising silicon dioxide or mixtures of silicon dioxide and zeolite is described, which is characterized in that it has a bimodal pore size distribution, the first maximum of the bimodal pore size distribution being in the pore size range 6 nm. The anti-blocking agent is obtainable by micronizing a mixture comprising silicon dioxide of a certain pore size and silicon dioxide and/or zeolite having a different pore size. It can be produced together with lubricating agent as a combined anti-blocking and lubricating agent. Incorporation of the anti-blocking agent or of the combined anti-blocking agent and lubricating agent into a polymer in the form of a master batch is preferable. In addition to a better dispersion and distribution of the anti-blocking agent particles in films and the improved optical properties associated therewith, the particular advantage of the anti-blocking agent according to the invention is that the adsorption of lubricating agent is avo...
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This paper presents the design of an efficient low complexity residual phase tracking algorithm for Orthogonal Frequency Division Multiplexing (OFDM) based Wireless Local Area Network receivers. In this paper the focus is on mitigation of... more
This paper presents the design of an efficient low complexity residual phase tracking algorithm for Orthogonal Frequency Division Multiplexing (OFDM) based Wireless Local Area Network receivers. In this paper the focus is on mitigation of the residual carrier frequency synchronization offset and sampling frequency offset. We propose a novel algorithm that uses piecewise linear approximation to estimate the complex exponential of the phase angle at pilot locations instead of estimating the actual phase angle by highly complex (costly) angle computation and search functions. This helps in reducing the implementation cost of an OFDM receiver. By means of analysis and simulation we show that our design combines both high performance and low complexity.
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The system requirements for IMT-A are currently being specified by the ITU. Target peak data rates of 1 Gb/s in local areas and 100 Mb/s in wide areas are expected to be provided by means of advanc...
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The next generation mobile communication networks (4G) have the challenging target of providing a peak data rate of 1 Gigabit per second local area and 100 Megabit per second wide area. The ability to offer such high data rates in 100MHz... more
The next generation mobile communication networks (4G) have the challenging target of providing a peak data rate of 1 Gigabit per second local area and 100 Megabit per second wide area. The ability to offer such high data rates in 100MHz bandwidth requires overall a very high spectral efficiency, and hence the need for multi-antenna techniques (MIMO) with spatial multiplexing, fast dynamic link adaptation and packet scheduling, wideband access techniques, and most likely non-contention based spectrum sharing among multiple operators. Many of these required technology components and techniques are well researched and established. "Adaptive PHY-MAC Design for Broadband Wireless Systems" explains how one can integrate and optimise their use in providing the target cell data rates with high availability. The authors address the ability to cope with interference and enhanced physical layer processing, and simultaneously, the multifaceted system level design. Focus is also on th...
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A frequency resource operating apparatus and method for transmitting and receiving data at a different hopping pattern speed according to a CSI in a BWA communication system are provided. In a method of transmitting and receiving data... more
A frequency resource operating apparatus and method for transmitting and receiving data at a different hopping pattern speed according to a CSI in a BWA communication system are provided. In a method of transmitting and receiving data using CSI in a mobile communication system, a BS sets the CSI of an MS to an initial CSI and sends data to the MS according to the initial CSI. The MS sends a downlink CSI to the BS. The BS groups the MS based on the downlink CSI and sends data to the MS according to a hopping pattern ...
Single-and Multi-Carrier MIMO A Transmission for Broadband Wireless Systems Authors Ramjee Prasad Muhammad Imadur Rahman Suvra Sekhar Das ... Single-and Multi-Carrier MIMO Transmission for Broadband Wireless Systems ... RIVER PUBLISHERS... more
Single-and Multi-Carrier MIMO A Transmission for Broadband Wireless Systems Authors Ramjee Prasad Muhammad Imadur Rahman Suvra Sekhar Das ... Single-and Multi-Carrier MIMO Transmission for Broadband Wireless Systems ... RIVER PUBLISHERS SERIES IN ...
In this paper, we have studied the potential for secondary usage of radar bands by 3GPP LTE eNB devices in different scenarios, such as HeNB transmitters located at street level, HeNB transmitters located at high-rise buildings, macro LTE... more
In this paper, we have studied the potential for secondary usage of radar bands by 3GPP LTE eNB devices in different scenarios, such as HeNB transmitters located at street level, HeNB transmitters located at high-rise buildings, macro LTE transmitter, etc. Different pathloss models are used to best suite the scenarios. By using different types of radar characteristics (e.g. radio navigations
ABSTRACT The number of mobile subscribers is expected to exceed 5 billion by the end of 2015: a key to attract such a huge number of users is to make them experience new multimedia services with a very high bit rate. In fact, the... more
ABSTRACT The number of mobile subscribers is expected to exceed 5 billion by the end of 2015: a key to attract such a huge number of users is to make them experience new multimedia services with a very high bit rate. In fact, the currently available bit rates do not encourage usage of today’s services like video downloading, as the video downloads can take tens of minutes, if not hours.
Page 1. The 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC'07) Impact of MIMO Co-Channel Interference Muhammad Imadur Rahman, Elisabeth de Carvalho, Ramjee ...
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Abstract Cyclic delay diversity can be used to increase the frequency selectivity of the wireless channel seen from the receiver. In this work, we have used this simple technique on top of a spatial multiplexing based orthogonal frequency... more
Abstract Cyclic delay diversity can be used to increase the frequency selectivity of the wireless channel seen from the receiver. In this work, we have used this simple technique on top of a spatial multiplexing based orthogonal frequency division multiplexing system. In ...
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Research Interests: Wireless Systems, Wireless Mobile Charger, Fading, Error Analysis, Wireless Sensor and Mobile Adhoc Networks, and 11 moreBit Error Rate, Adaptive modulation, BER, Throughput, Link Adaptation, Interference, Spectral Efficiency, Signal to Noise Ratio, Orthogonal Frequency Division Multiplexing, Signal strength, and OFDM modulation
Research Interests: OFDM, Antenna arrays, Wimax, Error Analysis, Adaptive modulation, and 11 moreThroughput, Link Adaptation, Power allocation, Power Distribution, Dynamic Channel Allocation, System performance, Signal to Noise Ratio, Orthogonal Frequency Division Multiplexing, Channel State Information, Channel Allocation, and OFDM modulation
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ABSTRACT We study how UE-to-UE interference impacts the performance, considering transmitter out-of-band (OOB) emissions and receiver blocking characteristics for homogenous 20 MHz LTE systems. For co-existing TDD systems on different... more
ABSTRACT We study how UE-to-UE interference impacts the performance, considering transmitter out-of-band (OOB) emissions and receiver blocking characteristics for homogenous 20 MHz LTE systems. For co-existing TDD systems on different carrier frequencies within the same band, UE-to-UE interference may occur in certain situations. The impact of such interference is evaluated for a hotspot scenario and compared to a uniform user distribution scenario, and is found to be significantly worse. When the number of scheduled users in the aggressor cell is high (e.g. >; 2), then receiver blocking impact, rather than the OOB emission, dominates the interference performance in hotspot scenario. Consequently, guard bands cannot be used to mitigate the receiver blocking impacts.
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ABSTRACT In LTE TDD there is typically no one-to-one association between UL and DL subframes, and for DL heavy asymmetries with more DL than UL subframes, ACK/NACK reports for multiple DL subframes need to be transmitted in an UL... more
ABSTRACT In LTE TDD there is typically no one-to-one association between UL and DL subframes, and for DL heavy asymmetries with more DL than UL subframes, ACK/NACK reports for multiple DL subframes need to be transmitted in an UL subframe. To improve uplink control channel performance, ACK/NACK bundling, where multiple ACK- NACKs are combined to a single ACK/NACK response for several DL subframes, is supported. In this paper, we study the impact on downlink performance of ACK/NACK bundling on link-level for LTE TDD systems both for SIMO and MIMO systems. It is found that the expected loss due to ACK/NACK bundling is rather small and hence bundling can be a good solution in many scenarios.
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Co-Channel Interference (CCI) caused by different Multiple Input Multiple Output (MIMO) signalling schemes impact the same or other MIMO schemes in different ways. Due to the symbol-by- symbol processing in a desired Single Input Multiple... more
Co-Channel Interference (CCI) caused by different Multiple Input Multiple Output (MIMO) signalling schemes impact the same or other MIMO schemes in different ways. Due to the symbol-by- symbol processing in a desired Single Input Multiple Output (SIMO) link, an interfering Space-Time Block Code (STBC) link may become equivalent to an interfering Spatial Multiplexing (SM) link. Using this knowledge and understanding, we propose an interference cancellation receiver robust to different types of MIMO interferers at cell edge for the Downlink (DL) of cellular systems. The receiver systematically performs a multiple symbol processing: this is the appropriate processing when the signal of interest or the signal of interferer is correlated across symbols, which is the case for STBC transmission. We evaluated different link combinations in terms of Signal to Interference and Noise Ratio (SINR) statistics and Bit Error Rate (BER) performance in cellular Orthogonal Frequency Division Multiple Access (OFDMA) . We have found that the proposed multiple-symbol linear interference cancellation receiver performs satisfactorily when any kind of single 'logical' stream MIMO scheme is present as interferer.
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ABSTRACT In this work, we have combined quasi-orthogonal space-frequency block code (QSFBC) and spatial multiplexing (SM) in one joint diversity and multiplexing (JDM) structure. Minimum mean square error (MMSE) and zero forcing (ZF)... more
ABSTRACT In this work, we have combined quasi-orthogonal space-frequency block code (QSFBC) and spatial multiplexing (SM) in one joint diversity and multiplexing (JDM) structure. Minimum mean square error (MMSE) and zero forcing (ZF) nulling based ordered successive interference cancellation (OSIC) receivers are derived for above mentioned JDM scheme. Performance comparison is done in realistic wireless scenario. It is observed through simulations that our JDM scheme performs very well in presence of spatial correlation caused by antenna separation and by line of sight (LOS) situation. The gains in frame error rate (FER) and outage spectral efficiency for JDM schemes with studied receivers are very high compared to corresponding SM only schemes.
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We propose a novel algorithm to allocate heterogeneous users in a wideband orthogonal frequency division multiple access (OFDMA) system. The heterogeneity among users originate from different channel statistics experienced by the users.... more
We propose a novel algorithm to allocate heterogeneous users in a wideband orthogonal frequency division multiple access (OFDMA) system. The heterogeneity among users originate from different channel statistics experienced by the users. The total available spectrum is divided into a number of bands equal to the number of groups. For efficient time-frequency resource allocation, sub-carrier hopping and band hopping is
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ABSTRACT This paper investigates the feasibility and broad implications of the use of 3GPP LTE systems in license-exempt situations. License-exempt use can occur in traditional unlicensed bands or in secondary usage of white space... more
ABSTRACT This paper investigates the feasibility and broad implications of the use of 3GPP LTE systems in license-exempt situations. License-exempt use can occur in traditional unlicensed bands or in secondary usage of white space spectrum. Various scenarios for license- exempt use are listed with a particular focus on spectrum access as a secondary user. Regulatory requirements devised by Federal Communications Commission (FCC) for TV white space usage are described and tabulated. General principles and recommendations for license ex- empt spectrum usage are proposed with some important scenarios being identified. Additional requirements arise out of the need to share the spectrum with other potential users in a fair manner. System simulation results in an indoor setting are used to estimate spectral efficiencies under such conditions. We conclude that LTE can be used in license-exempt secondary usage scenario with only minor modifications, such as fair sharing proce- dures, and could benefit from support for higher order modulations.
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In this report, we are going to outline several choices of Multiple Access (MA) techniques for Uplink (UL) and Downlink (DL) for the 4, Generation (4G) systems. The basic characteristics of the schemes,are described. Possible scenarios... more
In this report, we are going to outline several choices of Multiple Access (MA) techniques for Uplink (UL) and Downlink (DL) for the 4, Generation (4G) systems. The basic characteristics of the schemes,are described. Possible scenarios and system parameters for 4G systems is also presented. The goal is to discuss the basic principles of the available MA techniques. In no way, this report is intended to become a complete guide for studying the techniques. Interested authors are requested to refer to the relevant references in the bibliography. Acknowledgement: The author would like to acknowledge,the cooperation of Huan Cong Nguyen