Anais do XX Simpósio Brasileiro de Telecomunicações, 2003
In this work we propose a new receiver structure for space-time block-coded systems that decouple... more In this work we propose a new receiver structure for space-time block-coded systems that decouples the tasks of CCI cancellation and space-time decoding in two processing stages. The two-stage receiver consists of a multiple-input multiple-output (MIMO) minimum mean square error (MMSE) spatial filter for CCI cancellation connected to a modified time-reversal space-time decoder that is matched to the combined response of the channel of the desired user plus the MIMO-MMSE filter. A prefiltered MLSE detector is used for equalization. The two-stage receiver is compared to the one proposed in [10] for flat-fading channels. We show via computer simulation that the two-stage receiver effectively cancels CCI signals and still provides transmit diversity gain under frequency-selective fading.
2017 IEEE/AIAA 36th Digital Avionics Systems Conference (DASC), 2017
Aircraft designers believe that Power Line Communication (PLC) technology is a solution to reduce... more Aircraft designers believe that Power Line Communication (PLC) technology is a solution to reduce the number of cables aboard. One strategy to implement PLC networks in aircrafts is adapting commercial residential PLC solutions to the avionic environment. We propose in this paper a coupling architecture that improves PLC performance in terms of signal to noise ratio (SNR) when deployed on monofilar avionic networks. We also show that our proposal complies with the aeronautical electromagnetic standard (DO-160) through experimental validation. The proposed coupling architecture is investigated and validated through simulations and measurements. We analyze the performance of the PLC in terms of 3 parameters: S-parameters (transfer function), SNR and currents circulating on the aircraft circuit that must comply with the aeronautical electromagnetic regulations. The study also includes a real case scenario with the presence of a switch-mode power supply, which introduces distortion on the network and deteriorates the PLC performance. A comparison with a standard coupling circuit is performed and the results are promising.
2017 IEEE International Symposium on Power Line Communications and its Applications (ISPLC), 2017
Power Line Communication (PLC) systems are good candidates for next-generation aircraft communica... more Power Line Communication (PLC) systems are good candidates for next-generation aircraft communication channels. On-board power buses must meet stringent safety requirements that mandate the use of Transient Voltage suppressors (TVS) for lightning protection. These devices strongly degrade the performance of the communication channel. In this paper we analyze the impact of the lightning protection circuit used in aircraft power buses both theoretically and experimentally. It is shown that TVS devices are responsible for distortion and attenuation in the PLC signal band (1 MHz-100 MHz). We introduce a novel co-design strategy, matching PLC coupler to lightning protection conforming to air travel safety regulations. Our experimental results demonstrate that both constraints can be met using our proposed architecture.
In this work we present some MIMO transmission schemes that combine transmit diversity and spatia... more In this work we present some MIMO transmission schemes that combine transmit diversity and spatial multiplexing using four transmit antennas. Then, we show that the Bit-Error-Rate (BER) performance of these schemes can be considerably improved with the joint use of channel coding (at the transmitter) and soft-output detection (at the receiver). The SOVA approach is used to enhance performance of some detection layers that are not space-time coded. Both parallel and successive detection strategies are considered.
In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system for the ... more 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 L-band Digital Aeronautical Communication System (L-DACS), which will be responsible for the continental communications. This proposed candidate is named L-DACS2 and is foreseen to use part of the L-band spectrum (960 to 1164 MHz) allocated to the Aeronautical Mobile Service reserved for communications relating to safety and regularity of flight. Despite its potentially large spectrum, the L-band is a challenging environment for aeronautical communications because of the channel propagation characteristics and the dense spectral occupation by a large number of aeronautical systems. On the other hand, the RFC characterizes the electromagnetic compatibility between two radio systems and determines if they can coexist in the same electromagnetic environment. For this reason, the RFC is one of the main issues for L-DACS deployment and if it is not satisfied, the flight safety could be endangered. Hence, we propose to study in this paper the impact of the L-DACS on the Distance Measuring Equipment (DME), which is a very important equipment that has been using this band for decades. According to recent studies performed in the frequency domain , that is assuming continuous transmissions and no time domain variations, the achieved RFC level seems insufficient. The main objective of this work is to analyze the RFC between L-DACS2 and DME taking into account the time domain aspects of both systems. The idea is to verify and quantify the impact of the radio-frequency signals generated by a L-DACS2 interferer on the performance of a DME victim receiver. The study is performed for the co-site case (i.e. when both equipments are onboard of the same airplane), which is the most critical interference scenario due to the proximity of both systems. The results are obtained through computer simulations as well as laboratory measurements. They present the DME performance degradation for some values of the Signal to Interference Ratio, assuming a constant DME signal level and different L-DACS2 interference powers.
2012 IEEE First AESS European Conference on Satellite Telecommunications (ESTEL), 2012
In the last decade, the aeronautical authorities expressed their need to develop a new system for... more In the last decade, the aeronautical authorities expressed their need to develop a new system for aeronautical radiocommunications. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the future system that will be operating in a part of the aeronautical L-band (960−1164 M Hz), already occupied by a large number of radio-frequency legacy systems. This paper aims at studying the L-DACS impact on a legacy system, the Distance Measuring Equipment (DME), under two critical situations. Such topics are fundamental in aeronautics, as any communication or radionavigation dysfunction may endanger flight and passengers security. Some obtained results will be used for the L-DACS standardization and its specifications finalization. For the first scenario (air-to-air scenario), we propose a deterministic algorithm to compute the interference level in the frequency domain. Since this seems to be insufficient for the second scenario (co-site scenario), we develop a time-frequency approach to analyze the interference using an aeronautical RFC test-bed that we implemented at Supelec.
2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, 2009
General and commercial aviation authorities have been using amplitude modulation communication sy... more General and commercial aviation authorities have been using amplitude modulation communication systems for more than 70 years. Due to the great increase of air traffic during the last years, the VHF band tends towards saturation, whereas the aeronautical community faces new requirements: data rate, spectral efficiency and network capacity (maximum number of aircrafts simultaneously connected). Recently, the development of a new digital aeronautical communication system, named L-DACS, was proposed. This system will operate in the L band part allocated to aeronautics. There were many proposals but only two candidates have been pre-selected by the ITU and ICAO for this future communication system: L-DACS1 and L-DACS2. The deployment of this new system is expected to start after 2020. Among other issues, one important aspect is the impact of L-DACS on legacy systems. Actually, there are many onboard systems operating in L band, and any disfunction can put in danger the flight safety. This paper studies the maximum interference level generated by the two L-DACS candidates on a generic onboard receiver. Taking into account the antenna radiation pattern and the specific transmission mask of both candidates, the study determines the worst interference level and the corresponding spatial positions of the aircrafts around the receiver. The results show that the interference level can be determined by considering the several nearest aircrafts to the victim.
2009 9th International Conference on Intelligent Transport Systems Telecommunications, (ITST), 2009
The aeronautical community has recently decided to develop a new digital aeronautical communicati... more The aeronautical community has recently decided to develop a new digital aeronautical communication system, named L-DACS, in order to fulfill the new air traffic requirements. This system, which will operate in the L frequency band (960 to 1164 MHz), would be internationally deployed from 2020. Many technologies were considered for this new aeronautical system but only two among them were
In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system within f... more In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system within future aeronautical communication infrastructure, being developed since 2004 to accommodate the evolution of the aeronautical environment. The system presented in this paper is one of the two preselected proposals for the L-band Digital Aeronautical Communication System (L-DACS), in charge of the continental communications. It is named L-DACS2 and will use the 960 to 1164 MHz band, allocated to the Aeronautical Mobile Service reserved for communications relating to safety and regularity of flight. This band is characterized by a very dense spectral occupation by a large number of aeronautical systems. The RFC (branch of electrical science that studies the coexistence of radio systems in the same electromagnetic environment) is very important for L-DACS deployment and if it is not satisfied, the flight safety could be endangered. We propose to study in this paper the impact of the LDACS2 on the Distance Measuring Equipment (DME), which has been using the L-band for decades. According to recent studies performed in the frequency domain (continuous transmissions and no time domain variations), the achieved RFC level seems insufficient. The objective of this work is to analyze the RFC between LDACS2 and DME considering the time domain aspects of both systems. The idea is to quantify the impact of the radio-frequency signals generated by L-DACS2 interferer (transmitter) on the performance of a DME victim (receiver). The study is performed for the co-site case (equipments onboard of the same aircraft). To study the RFC between the two systems, we investigate various modulations for the future communication system. The results are obtained through computer simulations and laboratory measurements with an aeronautical testbed using a commercial DME unit. The DME performance degradation is evaluated for some values of the Signal to Interference Ratio.
2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications, 2008
Channel Division Multiple Access (ChDMA) is a promising multiple access scheme for Ultra-Wide Ban... more Channel Division Multiple Access (ChDMA) is a promising multiple access scheme for Ultra-Wide Band (UWB) systems based on the use of the Channel Impulse Responses (CIR) as user signatures. In this work, we modeled the UWB-CIR as linear combinations of continuous impulses of finite duration randomly delayed. Two different channels are considered: the first, very simplistic, generates multipaths that are uniformly distributed over the time; the second model, which introduces correlation between the delay and the energy of the paths, is built based on the channel power profile. The capacity is investigated assuming no Channel State Information (CSI) at the transmitters and perfect CSI at the receiver. As results, we derive the asymptotic capacity of the ChDMA scheme when the number of users and the number of frequency dimensions (which is proportional to the bandwidth) go to infinity with constant ratio. As a consequence, we observe that the asymptotic spectral efficiency depends only on the system load, the power delay profile, the noise variance and the pulse signal. The results are validated in certain conditions and compared with known results on CDMA systems.
2014 International Wireless Communications and Mobile Computing Conference (IWCMC), 2014
In this contribution we study the challenging issue of WiMedia solution which the ability to supp... more In this contribution we study the challenging issue of WiMedia solution which the ability to support high data rate applications but is limited to three piconets simultaneously communicating in the same area. For this reason we analyze the suitability of Channel Division Multiple Access (ChDMA) approach for Multiband Orthogonal Frequency Division Multiplexing (MBOFDM) Ultra Wide Band (UWB) (MB-UWB) system over IEEE 802.15.3a (UWB) channel model. ChDMA approach exploits the characteristics of MB-UWB system to separate the piconets. Each piconet employs its own Channel Frequency Response (CFR) as a signature code which introduces diversity. We have presented analytical analysis in terms of spectral efficiency (bits/s/Hz) assuming that the receiver knows the channel. Numerical analysis is run over IEEE 802.15.3a high data rate channel justified the importance of ChDMA solution to improve the spectral efficiency of MB-UWB system. Then, performance evaluation is investigated when minimum mean square error (MMSE) and matched filter (MF) receiver is applied. Simulations results show the importance of MMSE receiver to improve the performance of MB-UWB ChDMA system.
2006 Fortieth Asilomar Conference on Signals, Systems and Computers, 2006
In this contribution 1 , some results on the downlink capacity of MIMO Multiuser Networks are pro... more In this contribution 1 , some results on the downlink capacity of MIMO Multiuser Networks are provided when only the scattering environment (and not the channel realization) is known at the transmitter. Considering a multiuser system where each terminal employs multiple antennas (including the Base Station), asymptotic (in the number of antennas) analytical expressions of the system capacity are presented and studied in three different cases: equal time sharing, equal power sharing and optimum time-power scheduling. Interestingly, based only on the knowledge at the base station of the number of scatterers at each receiver link and not the full instantaneous channel realization (which can be fed back with limited overhead), one is able to derive optimal power and time scheduling policies which enhance the performance with respect to uniform time and power allocation. Simulations provided in the case of a small number of antennas confirm the asymptotic claims.
Proceedings of the 2nd International ICST Conference on Performance Evaluation Methodologies and Tools, 2007
This paper investigates the situation where a (large) group of terminals can be connected simulta... more This paper investigates the situation where a (large) group of terminals can be connected simultaneously to several base stations using distinct wireless technologies. We introduce and solve the problem of optimally sharing the mobile transmit power between different systems. Key results from asymptotic random matrix theory (when the number of users and the dimensions of different systems increase) allow us to derive the best power allocation scheme in the sense of the sum-capacity of the overall system, for which the uplink is equivalent to a parallel fading multiple access channel. Moreover, we provide an iterative algorithm to solve the power allocation algorithm. Simulations for a finite number of users validate the asymptotic claims.
2007 4th International Symposium on Wireless Communication Systems, 2007
This work presents some initial results concerning the MIMO channel capacity of real wireless cha... more This work presents some initial results concerning the MIMO channel capacity of real wireless channels in the UMTS-TDD band using the Eurecom MIMO Openair Sounder (EMOS). This paper describes the necessary steps to estimate in real-time the wireless MIMO environment, offering the possibility to identify reliable MIMO channels as well as instantaneous channel capacity. In particular, the problems related to additive and phase-shift noise are solved by employing OFDMA technology. Finally, based on measurements, we analyze the impact of polarization on the capacity performance.
Ultra-WideBand (UWB) has been recently presented as a promising radio technology due to the large... more Ultra-WideBand (UWB) has been recently presented as a promising radio technology due to the large bandwidth available. This feature enables point to point high data rates at short range as well as high temporal resolution with long Channel Impulse Responses (CIR). Due to the their large bandwidth, UWB systems enables high temporal resolution with long CIR. In this paper, we evaluate an original multiple access scheme called Channel Division Multiple Access (ChDMA), where we use the CIR as a user signature. The signature code is given by the channel and the users are separated by their position: this signature is uniquely determined by the user's position, which changes from one position to another. This signature locationdependent property provides decentralized flexible multiple access as the codes are naturally generated by the radio channel. The framework is analyzed and validated by capacity assessments using UWB measurements performed at Eurecom and compared with classical CDMA schemes with random spreading codes. The analysis is focused on the impact of the user's asynchronism and the period of symbol on system performance. Two structures are considered at the receiver: single-user matched filter and MMSE receiver with Gaussian and BPSK signaling schemes.
2014 International Conference on Multimedia Computing and Systems (ICMCS), 2014
In this contribution, we study the performance analysis of the Multiband Orthogonal Frequency Div... more In this contribution, we study the performance analysis of the Multiband Orthogonal Frequency Division Multiplexing Ultra Wide Band (MBOFDM UWB) high data rate system. The major problem of the MBOFDM UWB high data rate system is the cohabitation of more than three piconets sharing the same group of subbands over the same channel. As an alternative way to enhance the spectral efficiency of MBOFDM UWB system, the Channel Division Multiple Access (ChDMA) could be employed to explore the high diversity of UWB channels. The idea behind the ChDMA is to assimilate the channel impulse response (CIR) related to each user as a CDMA code signature. This approach increases the performance of the system by guarantying simultaneous access. Simulations are run over UWB indoor channel model and it is shown that MBOFDM UWB ChDMA outperforms MBOFDM UWB in respect of the metric of capacity. The simulations are performed through Minimum Mean Square Error receivers (MMSE) and the performance is evaluated based on the tradeoff between spectral efficiency (bit/s/Hz) and the ratio of number of users and “code” length. Numerical results show the advantage of ChDMA approach to enhance spectral efficiency of MBOFDM UWB high data rate system based on the accommodation of simultaneous operating piconets (SOPs).
Anais do XX Simpósio Brasileiro de Telecomunicações, 2003
In this work we propose a new receiver structure for space-time block-coded systems that decouple... more In this work we propose a new receiver structure for space-time block-coded systems that decouples the tasks of CCI cancellation and space-time decoding in two processing stages. The two-stage receiver consists of a multiple-input multiple-output (MIMO) minimum mean square error (MMSE) spatial filter for CCI cancellation connected to a modified time-reversal space-time decoder that is matched to the combined response of the channel of the desired user plus the MIMO-MMSE filter. A prefiltered MLSE detector is used for equalization. The two-stage receiver is compared to the one proposed in [10] for flat-fading channels. We show via computer simulation that the two-stage receiver effectively cancels CCI signals and still provides transmit diversity gain under frequency-selective fading.
2017 IEEE/AIAA 36th Digital Avionics Systems Conference (DASC), 2017
Aircraft designers believe that Power Line Communication (PLC) technology is a solution to reduce... more Aircraft designers believe that Power Line Communication (PLC) technology is a solution to reduce the number of cables aboard. One strategy to implement PLC networks in aircrafts is adapting commercial residential PLC solutions to the avionic environment. We propose in this paper a coupling architecture that improves PLC performance in terms of signal to noise ratio (SNR) when deployed on monofilar avionic networks. We also show that our proposal complies with the aeronautical electromagnetic standard (DO-160) through experimental validation. The proposed coupling architecture is investigated and validated through simulations and measurements. We analyze the performance of the PLC in terms of 3 parameters: S-parameters (transfer function), SNR and currents circulating on the aircraft circuit that must comply with the aeronautical electromagnetic regulations. The study also includes a real case scenario with the presence of a switch-mode power supply, which introduces distortion on the network and deteriorates the PLC performance. A comparison with a standard coupling circuit is performed and the results are promising.
2017 IEEE International Symposium on Power Line Communications and its Applications (ISPLC), 2017
Power Line Communication (PLC) systems are good candidates for next-generation aircraft communica... more Power Line Communication (PLC) systems are good candidates for next-generation aircraft communication channels. On-board power buses must meet stringent safety requirements that mandate the use of Transient Voltage suppressors (TVS) for lightning protection. These devices strongly degrade the performance of the communication channel. In this paper we analyze the impact of the lightning protection circuit used in aircraft power buses both theoretically and experimentally. It is shown that TVS devices are responsible for distortion and attenuation in the PLC signal band (1 MHz-100 MHz). We introduce a novel co-design strategy, matching PLC coupler to lightning protection conforming to air travel safety regulations. Our experimental results demonstrate that both constraints can be met using our proposed architecture.
In this work we present some MIMO transmission schemes that combine transmit diversity and spatia... more In this work we present some MIMO transmission schemes that combine transmit diversity and spatial multiplexing using four transmit antennas. Then, we show that the Bit-Error-Rate (BER) performance of these schemes can be considerably improved with the joint use of channel coding (at the transmitter) and soft-output detection (at the receiver). The SOVA approach is used to enhance performance of some detection layers that are not space-time coded. Both parallel and successive detection strategies are considered.
In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system for the ... more 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 L-band Digital Aeronautical Communication System (L-DACS), which will be responsible for the continental communications. This proposed candidate is named L-DACS2 and is foreseen to use part of the L-band spectrum (960 to 1164 MHz) allocated to the Aeronautical Mobile Service reserved for communications relating to safety and regularity of flight. Despite its potentially large spectrum, the L-band is a challenging environment for aeronautical communications because of the channel propagation characteristics and the dense spectral occupation by a large number of aeronautical systems. On the other hand, the RFC characterizes the electromagnetic compatibility between two radio systems and determines if they can coexist in the same electromagnetic environment. For this reason, the RFC is one of the main issues for L-DACS deployment and if it is not satisfied, the flight safety could be endangered. Hence, we propose to study in this paper the impact of the L-DACS on the Distance Measuring Equipment (DME), which is a very important equipment that has been using this band for decades. According to recent studies performed in the frequency domain , that is assuming continuous transmissions and no time domain variations, the achieved RFC level seems insufficient. The main objective of this work is to analyze the RFC between L-DACS2 and DME taking into account the time domain aspects of both systems. The idea is to verify and quantify the impact of the radio-frequency signals generated by a L-DACS2 interferer on the performance of a DME victim receiver. The study is performed for the co-site case (i.e. when both equipments are onboard of the same airplane), which is the most critical interference scenario due to the proximity of both systems. The results are obtained through computer simulations as well as laboratory measurements. They present the DME performance degradation for some values of the Signal to Interference Ratio, assuming a constant DME signal level and different L-DACS2 interference powers.
2012 IEEE First AESS European Conference on Satellite Telecommunications (ESTEL), 2012
In the last decade, the aeronautical authorities expressed their need to develop a new system for... more In the last decade, the aeronautical authorities expressed their need to develop a new system for aeronautical radiocommunications. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the future system that will be operating in a part of the aeronautical L-band (960−1164 M Hz), already occupied by a large number of radio-frequency legacy systems. This paper aims at studying the L-DACS impact on a legacy system, the Distance Measuring Equipment (DME), under two critical situations. Such topics are fundamental in aeronautics, as any communication or radionavigation dysfunction may endanger flight and passengers security. Some obtained results will be used for the L-DACS standardization and its specifications finalization. For the first scenario (air-to-air scenario), we propose a deterministic algorithm to compute the interference level in the frequency domain. Since this seems to be insufficient for the second scenario (co-site scenario), we develop a time-frequency approach to analyze the interference using an aeronautical RFC test-bed that we implemented at Supelec.
2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, 2009
General and commercial aviation authorities have been using amplitude modulation communication sy... more General and commercial aviation authorities have been using amplitude modulation communication systems for more than 70 years. Due to the great increase of air traffic during the last years, the VHF band tends towards saturation, whereas the aeronautical community faces new requirements: data rate, spectral efficiency and network capacity (maximum number of aircrafts simultaneously connected). Recently, the development of a new digital aeronautical communication system, named L-DACS, was proposed. This system will operate in the L band part allocated to aeronautics. There were many proposals but only two candidates have been pre-selected by the ITU and ICAO for this future communication system: L-DACS1 and L-DACS2. The deployment of this new system is expected to start after 2020. Among other issues, one important aspect is the impact of L-DACS on legacy systems. Actually, there are many onboard systems operating in L band, and any disfunction can put in danger the flight safety. This paper studies the maximum interference level generated by the two L-DACS candidates on a generic onboard receiver. Taking into account the antenna radiation pattern and the specific transmission mask of both candidates, the study determines the worst interference level and the corresponding spatial positions of the aircrafts around the receiver. The results show that the interference level can be determined by considering the several nearest aircrafts to the victim.
2009 9th International Conference on Intelligent Transport Systems Telecommunications, (ITST), 2009
The aeronautical community has recently decided to develop a new digital aeronautical communicati... more The aeronautical community has recently decided to develop a new digital aeronautical communication system, named L-DACS, in order to fulfill the new air traffic requirements. This system, which will operate in the L frequency band (960 to 1164 MHz), would be internationally deployed from 2020. Many technologies were considered for this new aeronautical system but only two among them were
In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system within f... more In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system within future aeronautical communication infrastructure, being developed since 2004 to accommodate the evolution of the aeronautical environment. The system presented in this paper is one of the two preselected proposals for the L-band Digital Aeronautical Communication System (L-DACS), in charge of the continental communications. It is named L-DACS2 and will use the 960 to 1164 MHz band, allocated to the Aeronautical Mobile Service reserved for communications relating to safety and regularity of flight. This band is characterized by a very dense spectral occupation by a large number of aeronautical systems. The RFC (branch of electrical science that studies the coexistence of radio systems in the same electromagnetic environment) is very important for L-DACS deployment and if it is not satisfied, the flight safety could be endangered. We propose to study in this paper the impact of the LDACS2 on the Distance Measuring Equipment (DME), which has been using the L-band for decades. According to recent studies performed in the frequency domain (continuous transmissions and no time domain variations), the achieved RFC level seems insufficient. The objective of this work is to analyze the RFC between LDACS2 and DME considering the time domain aspects of both systems. The idea is to quantify the impact of the radio-frequency signals generated by L-DACS2 interferer (transmitter) on the performance of a DME victim (receiver). The study is performed for the co-site case (equipments onboard of the same aircraft). To study the RFC between the two systems, we investigate various modulations for the future communication system. The results are obtained through computer simulations and laboratory measurements with an aeronautical testbed using a commercial DME unit. The DME performance degradation is evaluated for some values of the Signal to Interference Ratio.
2008 IEEE 9th Workshop on Signal Processing Advances in Wireless Communications, 2008
Channel Division Multiple Access (ChDMA) is a promising multiple access scheme for Ultra-Wide Ban... more Channel Division Multiple Access (ChDMA) is a promising multiple access scheme for Ultra-Wide Band (UWB) systems based on the use of the Channel Impulse Responses (CIR) as user signatures. In this work, we modeled the UWB-CIR as linear combinations of continuous impulses of finite duration randomly delayed. Two different channels are considered: the first, very simplistic, generates multipaths that are uniformly distributed over the time; the second model, which introduces correlation between the delay and the energy of the paths, is built based on the channel power profile. The capacity is investigated assuming no Channel State Information (CSI) at the transmitters and perfect CSI at the receiver. As results, we derive the asymptotic capacity of the ChDMA scheme when the number of users and the number of frequency dimensions (which is proportional to the bandwidth) go to infinity with constant ratio. As a consequence, we observe that the asymptotic spectral efficiency depends only on the system load, the power delay profile, the noise variance and the pulse signal. The results are validated in certain conditions and compared with known results on CDMA systems.
2014 International Wireless Communications and Mobile Computing Conference (IWCMC), 2014
In this contribution we study the challenging issue of WiMedia solution which the ability to supp... more In this contribution we study the challenging issue of WiMedia solution which the ability to support high data rate applications but is limited to three piconets simultaneously communicating in the same area. For this reason we analyze the suitability of Channel Division Multiple Access (ChDMA) approach for Multiband Orthogonal Frequency Division Multiplexing (MBOFDM) Ultra Wide Band (UWB) (MB-UWB) system over IEEE 802.15.3a (UWB) channel model. ChDMA approach exploits the characteristics of MB-UWB system to separate the piconets. Each piconet employs its own Channel Frequency Response (CFR) as a signature code which introduces diversity. We have presented analytical analysis in terms of spectral efficiency (bits/s/Hz) assuming that the receiver knows the channel. Numerical analysis is run over IEEE 802.15.3a high data rate channel justified the importance of ChDMA solution to improve the spectral efficiency of MB-UWB system. Then, performance evaluation is investigated when minimum mean square error (MMSE) and matched filter (MF) receiver is applied. Simulations results show the importance of MMSE receiver to improve the performance of MB-UWB ChDMA system.
2006 Fortieth Asilomar Conference on Signals, Systems and Computers, 2006
In this contribution 1 , some results on the downlink capacity of MIMO Multiuser Networks are pro... more In this contribution 1 , some results on the downlink capacity of MIMO Multiuser Networks are provided when only the scattering environment (and not the channel realization) is known at the transmitter. Considering a multiuser system where each terminal employs multiple antennas (including the Base Station), asymptotic (in the number of antennas) analytical expressions of the system capacity are presented and studied in three different cases: equal time sharing, equal power sharing and optimum time-power scheduling. Interestingly, based only on the knowledge at the base station of the number of scatterers at each receiver link and not the full instantaneous channel realization (which can be fed back with limited overhead), one is able to derive optimal power and time scheduling policies which enhance the performance with respect to uniform time and power allocation. Simulations provided in the case of a small number of antennas confirm the asymptotic claims.
Proceedings of the 2nd International ICST Conference on Performance Evaluation Methodologies and Tools, 2007
This paper investigates the situation where a (large) group of terminals can be connected simulta... more This paper investigates the situation where a (large) group of terminals can be connected simultaneously to several base stations using distinct wireless technologies. We introduce and solve the problem of optimally sharing the mobile transmit power between different systems. Key results from asymptotic random matrix theory (when the number of users and the dimensions of different systems increase) allow us to derive the best power allocation scheme in the sense of the sum-capacity of the overall system, for which the uplink is equivalent to a parallel fading multiple access channel. Moreover, we provide an iterative algorithm to solve the power allocation algorithm. Simulations for a finite number of users validate the asymptotic claims.
2007 4th International Symposium on Wireless Communication Systems, 2007
This work presents some initial results concerning the MIMO channel capacity of real wireless cha... more This work presents some initial results concerning the MIMO channel capacity of real wireless channels in the UMTS-TDD band using the Eurecom MIMO Openair Sounder (EMOS). This paper describes the necessary steps to estimate in real-time the wireless MIMO environment, offering the possibility to identify reliable MIMO channels as well as instantaneous channel capacity. In particular, the problems related to additive and phase-shift noise are solved by employing OFDMA technology. Finally, based on measurements, we analyze the impact of polarization on the capacity performance.
Ultra-WideBand (UWB) has been recently presented as a promising radio technology due to the large... more Ultra-WideBand (UWB) has been recently presented as a promising radio technology due to the large bandwidth available. This feature enables point to point high data rates at short range as well as high temporal resolution with long Channel Impulse Responses (CIR). Due to the their large bandwidth, UWB systems enables high temporal resolution with long CIR. In this paper, we evaluate an original multiple access scheme called Channel Division Multiple Access (ChDMA), where we use the CIR as a user signature. The signature code is given by the channel and the users are separated by their position: this signature is uniquely determined by the user's position, which changes from one position to another. This signature locationdependent property provides decentralized flexible multiple access as the codes are naturally generated by the radio channel. The framework is analyzed and validated by capacity assessments using UWB measurements performed at Eurecom and compared with classical CDMA schemes with random spreading codes. The analysis is focused on the impact of the user's asynchronism and the period of symbol on system performance. Two structures are considered at the receiver: single-user matched filter and MMSE receiver with Gaussian and BPSK signaling schemes.
2014 International Conference on Multimedia Computing and Systems (ICMCS), 2014
In this contribution, we study the performance analysis of the Multiband Orthogonal Frequency Div... more In this contribution, we study the performance analysis of the Multiband Orthogonal Frequency Division Multiplexing Ultra Wide Band (MBOFDM UWB) high data rate system. The major problem of the MBOFDM UWB high data rate system is the cohabitation of more than three piconets sharing the same group of subbands over the same channel. As an alternative way to enhance the spectral efficiency of MBOFDM UWB system, the Channel Division Multiple Access (ChDMA) could be employed to explore the high diversity of UWB channels. The idea behind the ChDMA is to assimilate the channel impulse response (CIR) related to each user as a CDMA code signature. This approach increases the performance of the system by guarantying simultaneous access. Simulations are run over UWB indoor channel model and it is shown that MBOFDM UWB ChDMA outperforms MBOFDM UWB in respect of the metric of capacity. The simulations are performed through Minimum Mean Square Error receivers (MMSE) and the performance is evaluated based on the tradeoff between spectral efficiency (bit/s/Hz) and the ratio of number of users and “code” length. Numerical results show the advantage of ChDMA approach to enhance spectral efficiency of MBOFDM UWB high data rate system based on the accommodation of simultaneous operating piconets (SOPs).
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Papers by Raul Lacerda