IEEE Transactions on Wireless Communications, 2021
5G mmWave MIMO systems enable accurate estimation of the user position and mapping of the radio e... more 5G mmWave MIMO systems enable accurate estimation of the user position and mapping of the radio environment using a single snapshot when both the base station (BS) and user are equipped with large antenna arrays. However, massive arrays are initially expected only at the BS side, likely leaving users with one or very few antennas. In this paper, we propose a novel method for single-snapshot localization and mapping in the more challenging case of a user equipped with a single-antenna receiver. The joint maximum likelihood (ML) estimation problem is formulated and its solution formally derived. To avoid the burden of a full-dimensional search over the space of the unknown parameters, we present a novel practical approach that exploits the sparsity of mmWave channels to compute an approximate joint ML estimate. A thorough analysis, including the derivation of the Cramér-Rao lower bounds, reveals that accurate localization and mapping can be achieved also in a MISO setup even when the direct line-of-sight path between the BS and the user is severely attenuated.
Reconfigurable intelligent surfaces (RISs) are one of the most promising technological enablers o... more Reconfigurable intelligent surfaces (RISs) are one of the most promising technological enablers of the next (6th) generation of wireless systems. In this paper, we introduce a novel use-case of the RIS technology in radio localization, which is enabling the user to estimate its own position via transmitting orthogonal frequency-division multiplexing (OFDM) pilots and processing the signal reflected from the RIS. We demonstrate that user localization in this scenario is possible by deriving CramérRao lower bounds on the positioning error and devising a lowcomplexity position estimation algorithm. We consider random and directional RIS phase profiles and apply a specific temporal coding to them, such that the reflected signal from the RIS can be separated from the uncontrolled multipath. Finally, we assess the performance of our position estimator for an example system, and show that the proposed algorithm can attain the derived bound at high signal-to-noise ratio values.
5G-NR New Radio (5G-NR) is destined to revolutionize the wireless communications as well<br>... more 5G-NR New Radio (5G-NR) is destined to revolutionize the wireless communications as well<br> as user wireless positioning. 5G-NR will be able to offer not only higher throughput and<br> higher available frequency bands of operation, but also improved services, including enhanced<br> Location Based Services. 5G systems will continue to use the Positioning Reference Signals<br> (PRS) employed now in 4G systems, in order to enable positioning with non-synchronized<br> Base Stations (BS) with an increased performance compared to 4G positioning. PRS are used<br> to measure the delays of the downlink transmissions by correlating the received signal from<br> the base station with a local replica in the receiver. In this paper, different PRS allocations<br> within the 5G frame are analysed and compared in order to find if the PRS distribution affects<br> the positioning performance, and, if this happens, which the best distribution is.
Millimeter-wave (mm-wave) and massive multiple-input-multiple-output technologies appear as key e... more Millimeter-wave (mm-wave) and massive multiple-input-multiple-output technologies appear as key enablers in future emerging wireless communication systems. Propagation in mmwave communications is well described by geometric channel models, where a clear relation between communication and positioning arises. On one hand, initial access, a procedure that precedes high data rate transmission and consists of beam selection and alignment between two devices, can benefit from position information. On the other hand, accurate positioning relies on high-quality communication links with proper beam alignment. This work analyzes the interplay between communication and positioning, proposes a new in-band position-aided beam selection protocol considering scenarios with line-of-sight and reflected paths, and possible beam alignment errors. Simulation results show significant reductions in latency with respect to standard beam selection protocols.
Navigation and communications capabilities become necessary in current wireless transmission syst... more Navigation and communications capabilities become necessary in current wireless transmission systems. The new mobile terminals demand higher requirements to satisfy high-data rate services, as well as new location-based applications. On one side, GNSS systems greatly succeed to provide precise positioning for new applications and services. On the other, multicarrier signals are widely used for high-capacity transmission, such as in xDSL, WiFi or WiMAX. Thus, the current commercial market proposes the combination of GNSS and communication systems to enhance performance. Nevertheless, the use of mobile terminals in harsh environments, such as urban or indoor areas, deteriorates the performance of GNSS receivers. Therefore, the application of multicarrier signals also for ranging purposes is proposed to achieve the required NAV-COM system. Although multicarrier signals have been widely adopted in communications, little attention has been paid to their potential application to navigatio...
Location-aware communication systems are expected to play a pivotal part in the next generation o... more Location-aware communication systems are expected to play a pivotal part in the next generation of mobile communication networks. Therefore, there is a need to understand the localization limits in these networks, particularly, using millimeter-wave technology (mmWave). Towards that, we address the uplink and downlink localization limits in terms of 3D position and orientation error bounds for mmWave multipath channels. We also carry out a detailed analysis of the dependence of the bounds of different systems parameters. Our key findings indicate that the uplink and downlink behave differently in two distinct ways. First of all, the error bounds have different scaling factors with respect to the number of antennas in the uplink and downlink. Secondly, uplink localization is sensitive to the orientation angle of the user equipment (UE), whereas downlink is not. Moreover, in the considered outdoor scenarios, the non-line-of-sight paths generally improve localization when a line-of-sight path exists. Finally, our numerical results show that mmWave systems are capable of localizing a UE with sub-meter position error, and sub-degree orientation error.
Recently, localization for 5G millimeter-wave communication systems has been shown to provide hig... more Recently, localization for 5G millimeter-wave communication systems has been shown to provide highaccuracy performance, with error being in the order of tens of centimeters. However, most of the literature assumes a high level of synchronization, which is not always the case practically. To address this matter, we investigate a distributed two-way localization protocol (DLP) that relieves the need for tight timing synchronization. We derive the position and orientation bounds, when localization is initiated and carried out by the base station. Our simulation results show that the performance of DLP is identical to that of the synchronized one-way localization. We thus conclude that the considered 5G localization is limited by the estimation of the angles rather than the delay. The results also imply that orientation estimation is more challenging than position estimation.
IEEE Transactions on Wireless Communications, 2021
5G mmWave MIMO systems enable accurate estimation of the user position and mapping of the radio e... more 5G mmWave MIMO systems enable accurate estimation of the user position and mapping of the radio environment using a single snapshot when both the base station (BS) and user are equipped with large antenna arrays. However, massive arrays are initially expected only at the BS side, likely leaving users with one or very few antennas. In this paper, we propose a novel method for single-snapshot localization and mapping in the more challenging case of a user equipped with a single-antenna receiver. The joint maximum likelihood (ML) estimation problem is formulated and its solution formally derived. To avoid the burden of a full-dimensional search over the space of the unknown parameters, we present a novel practical approach that exploits the sparsity of mmWave channels to compute an approximate joint ML estimate. A thorough analysis, including the derivation of the Cramér-Rao lower bounds, reveals that accurate localization and mapping can be achieved also in a MISO setup even when the direct line-of-sight path between the BS and the user is severely attenuated.
Reconfigurable intelligent surfaces (RISs) are one of the most promising technological enablers o... more Reconfigurable intelligent surfaces (RISs) are one of the most promising technological enablers of the next (6th) generation of wireless systems. In this paper, we introduce a novel use-case of the RIS technology in radio localization, which is enabling the user to estimate its own position via transmitting orthogonal frequency-division multiplexing (OFDM) pilots and processing the signal reflected from the RIS. We demonstrate that user localization in this scenario is possible by deriving CramérRao lower bounds on the positioning error and devising a lowcomplexity position estimation algorithm. We consider random and directional RIS phase profiles and apply a specific temporal coding to them, such that the reflected signal from the RIS can be separated from the uncontrolled multipath. Finally, we assess the performance of our position estimator for an example system, and show that the proposed algorithm can attain the derived bound at high signal-to-noise ratio values.
5G-NR New Radio (5G-NR) is destined to revolutionize the wireless communications as well<br>... more 5G-NR New Radio (5G-NR) is destined to revolutionize the wireless communications as well<br> as user wireless positioning. 5G-NR will be able to offer not only higher throughput and<br> higher available frequency bands of operation, but also improved services, including enhanced<br> Location Based Services. 5G systems will continue to use the Positioning Reference Signals<br> (PRS) employed now in 4G systems, in order to enable positioning with non-synchronized<br> Base Stations (BS) with an increased performance compared to 4G positioning. PRS are used<br> to measure the delays of the downlink transmissions by correlating the received signal from<br> the base station with a local replica in the receiver. In this paper, different PRS allocations<br> within the 5G frame are analysed and compared in order to find if the PRS distribution affects<br> the positioning performance, and, if this happens, which the best distribution is.
Millimeter-wave (mm-wave) and massive multiple-input-multiple-output technologies appear as key e... more Millimeter-wave (mm-wave) and massive multiple-input-multiple-output technologies appear as key enablers in future emerging wireless communication systems. Propagation in mmwave communications is well described by geometric channel models, where a clear relation between communication and positioning arises. On one hand, initial access, a procedure that precedes high data rate transmission and consists of beam selection and alignment between two devices, can benefit from position information. On the other hand, accurate positioning relies on high-quality communication links with proper beam alignment. This work analyzes the interplay between communication and positioning, proposes a new in-band position-aided beam selection protocol considering scenarios with line-of-sight and reflected paths, and possible beam alignment errors. Simulation results show significant reductions in latency with respect to standard beam selection protocols.
Navigation and communications capabilities become necessary in current wireless transmission syst... more Navigation and communications capabilities become necessary in current wireless transmission systems. The new mobile terminals demand higher requirements to satisfy high-data rate services, as well as new location-based applications. On one side, GNSS systems greatly succeed to provide precise positioning for new applications and services. On the other, multicarrier signals are widely used for high-capacity transmission, such as in xDSL, WiFi or WiMAX. Thus, the current commercial market proposes the combination of GNSS and communication systems to enhance performance. Nevertheless, the use of mobile terminals in harsh environments, such as urban or indoor areas, deteriorates the performance of GNSS receivers. Therefore, the application of multicarrier signals also for ranging purposes is proposed to achieve the required NAV-COM system. Although multicarrier signals have been widely adopted in communications, little attention has been paid to their potential application to navigatio...
Location-aware communication systems are expected to play a pivotal part in the next generation o... more Location-aware communication systems are expected to play a pivotal part in the next generation of mobile communication networks. Therefore, there is a need to understand the localization limits in these networks, particularly, using millimeter-wave technology (mmWave). Towards that, we address the uplink and downlink localization limits in terms of 3D position and orientation error bounds for mmWave multipath channels. We also carry out a detailed analysis of the dependence of the bounds of different systems parameters. Our key findings indicate that the uplink and downlink behave differently in two distinct ways. First of all, the error bounds have different scaling factors with respect to the number of antennas in the uplink and downlink. Secondly, uplink localization is sensitive to the orientation angle of the user equipment (UE), whereas downlink is not. Moreover, in the considered outdoor scenarios, the non-line-of-sight paths generally improve localization when a line-of-sight path exists. Finally, our numerical results show that mmWave systems are capable of localizing a UE with sub-meter position error, and sub-degree orientation error.
Recently, localization for 5G millimeter-wave communication systems has been shown to provide hig... more Recently, localization for 5G millimeter-wave communication systems has been shown to provide highaccuracy performance, with error being in the order of tens of centimeters. However, most of the literature assumes a high level of synchronization, which is not always the case practically. To address this matter, we investigate a distributed two-way localization protocol (DLP) that relieves the need for tight timing synchronization. We derive the position and orientation bounds, when localization is initiated and carried out by the base station. Our simulation results show that the performance of DLP is identical to that of the synchronized one-way localization. We thus conclude that the considered 5G localization is limited by the estimation of the angles rather than the delay. The results also imply that orientation estimation is more challenging than position estimation.
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Papers by Gonzalo Seco