Map-Assisted Millimeter Wave Localization for Accurate Position Location

Non-orthogonal multiple access (NOMA) and mmWave are considered to be promising techniques for 5G and beyond cellular network communication systems. While the mmWave band provides a very wide under-utilized bandwidth, NOMA enhances the spectral efficiency compared to orthogonal multiple access (OMA). The combination of these two techniques could be considered as the key solution to the high required data rates in next-generation communication systems. The implementation of NOMA is studied and verified under an ideal condition with perfect knowledge of the channel state information (CSI) at the base station (BS). However, under the practical conditions, the fluctuation of the wireless channel makes perfect CSI unachievable at the BS. Hence, we proposed to use the angle of departure (AoD) as feedback information from UEs to the BS. We assume that, mobile users (UEs) perfectly estimate the channel by detecting the pilot signals. Then, UEs quantize the AoD and feed back to the BS. Finally, the BS uses the AoD to perform user clustering, power allocation and beamforming. To reduce the feedback overhead further, we proposed a user clustering algorithm which uses one-bit feedback to determine the change of the AoD. Numerical results demonstrate that the proposed NOMA system outperforms the conventional orthogonal multiple-access (OMA) system with the same amount of feedback information.

Based on the joint estimations of time of arrival (TOA), angle of arrival (AOA) and angle of departure (AOD) of two or more single-bounced multipaths from a single base station (BS) and an mobile station (MS) in an MIMO system, two schemes, closed-form total least squares solution (CF-TLS) and constraint-based grid-search approach (CB-GSA) are presented to locate an MS. The CF-TLS method is time saving and provides good location accuracy when two or more resolvable single-bounced multipaths are available. However, the CB-GSA method always provides better location accuracy than the CF-TLS method at a cost of large computational burden. When only two single-bounced multipaths can be observed or the range and angle measurement errors are large, the location accuracy of the CB-GSA method outperforms that of the CF-TLS method significantly. By executing the CF-TLS method to give an initial estimation of an MS position, the search area of the CB-GSA method is narrowed, and the location time is significantly reduced. Simulations verify the effectiveness of the two proposed methods.

Traditional cellular networks require the downlink (DL) and uplink (UL) of mobile users (MUs) to be associated with a single base station (BS). However, the power gap between BSs and MUs in different transmission environments results in the BS with the strongest downlink differing from the BS with the strongest uplink. In addition, the significant increase in the number of wireless machine type communication (MTC) devices accessing cellular networks has created a DL/UL traffic imbalance with higher traffic volume on the uplink. In this paper, a joint user association and resource partition framework for downlink-uplink decoupling (DUDe) is developed for a tiered heterogeneous cellular network (HCN). Different from the traditional association rules such as maximal received power and range extension, a coalition game based scheme is proposed for the optimal user association with DUDe. The stability and convergence of this scheme are proven and shown to converge to a Nash equilibrium at a geometric rate. Moreover, the DL and UL optimal bandwidth partition for BSs is derived based on user association considering fairness. Extensive simulation results demonstrate the effectiveness of the proposed scheme, which enhances the sum rate compared with other user association strategies.

Based on the results of an analysis of foreign publications of the last ten years in the field of device positioning in cognitive radio systems and networks of the fifth and sixth generations, we can state the emergence of a new scientific direction - personal radars. Their practical implementation became possible with the transition of transceivers to the range of millimeter and submillimeter waves, as well as due to the widespread use of multi-element antenna arrays both at base stations and on user devices. In mobile radio networks of the fourth and fifth generations, the problem of determining the location of user devices was solved centrally, predominantly using multi-position range and/or angle methods, when signals received or transmitted by several base stations served to collect primary measurements of signal time and/or angle of arrival/departure. In contrast to the centralized multi-position estimation of coordinates in existing com munication networks, the concept of a personal radar in promising sixth-generation cognitive radio systems with a device-centric architecture makes it possible to solve the problem of positioning a user device using a single-position method based on a signal from a singlebase station. The single-position method is based on the sparse property of a millimeter-wave radio channel, its representation in the beam space domain, as well as the use of a compressed sensing algorithm in space based on a set of departure and arrival angles. This work is devoted to the development of mathematical and simulation models to establish the accuracy limits and conditions for the practical feasibility of a single-position method for estimating the coordinates and orientation of user devices based on a signal from a single base station in sixth-generation cognitive radio systems operating on the principle of a personal radar. The presented mathematical formalization and software implementation of the single-position positioning method showed its performance on a plane when estimating the coordinates and orientation of the device with an accuracy of up to units of meters and units of degrees.

In this paper, we investigate the downlink achievable ergodic spectral efficiency (SE) of a single-cell multi-user millimeter wave system, in which a uniform rectangular array is used at the base station (BS) to serve multiple single-antenna users. We adopt a three-dimensional channel model by considering both the azimuth and elevation dimensions under single-path propagation. We derive the achievable ergodic SE for this system in with maximum ratio transmission precoding. This analytical expression enables the accurate and quantitative evaluation of the effect of the number of BS antennas, signal-to-noise ratio (SNR), and the crosstalk (squared inner product between different steering vectors) which is a function of the angles of departure (AoD) of users and the inter-antenna spacing. Results show that the achievable ergodic SE logarithmically increases with the number of BS antennas and converges to a value in the high SNR regime. To improve the achievable ergodic SE, we also propose a user scheduling scheme based on feedback of users’ AoD information and obtain the maximum achievable ergodic SE. Furthermore, we consider a dense user scenario where every user’s AoD becomes nearly identical and then derive the system’s minimum achievable SE.

This paper studies feedback resource allocation in the downlink of a Frequency Division Duplex (FDD) multichannel wireless system. We consider a downlink network with a single base station, L shared channels and N mobile users. Throughput optimal algorithms like the MaxWeight scheduling in general require the complete channel state information (with N × L link states) for scheduling, which could be unaffordably expensive when the number of users is large. In this paper, we consider the scenario where the base station allocates only limited uplink resource for acquiring channel state information. We first show that to support a fraction (1 - ε) of the full throughput region (the throughput region with full channel state information), the base station needs to acquire at least Θ(L) link states at each time slot. We then propose a Weight Based Feedback allocation, named WBF, and show that WBF together with the MaxWeight scheduling achieves a fraction (1 - ε) of the full throughput region by acquiring at most Θ(L log 1 ⁄ ε) link states per time slot.

Millimeter-wave (mmWave) bands is considered for fifth-generation (5G) cellular systems because abundant spectrum is available for mobile broadband communications. In mmWave communication systems, accurate beamforming is important to compensate for high attenuation in the mmWave frequency band and to extend the transmission range. However, with the existing beamformers in mmWave cellular systems, the mobile station (MS) cannot identify the source (base station; BS) of the received beam because there are many neighboring BSs transmitting their training signals, requiring a large overhead. This paper proposes a new beam weight generation method for transmitting (Tx) beamformers at the BS in mmWave cellular systems during a beam training period. Beam weights are generated for Tx beamformers at neighboring BSs, so that a mobile station (MS) can estimate the source (cell ID; CID) and angle of departure (AoD) for each BS in multi-cell environments. A CID and AoD estimation method for mmWave cellular systems in a line-of-sight (LOS) dominant condition is presented using the beam weights generated by Zadoff-Chu sequence. A simulation is conducted in a LOS dominant condition to show that the performances of CID detection and AoD estimation are similar for both the proposed and conventional methods. In the conventional methods, the DFT-based beamforming weight is used for Tx beamformer at the BS and orthogonal matching pursuit (OMP) algorithm is used for AoD estimation at the MS. The proposed method significantly reduces the processing time (1.6–6.25%) required for beam training compared to the conventional method.

Simultaneous localization and mapping (SLAM) is a key technology that provides user equipment (UE) tracking and environment mapping services, enabling the deep integration of sensing and communication. The millimeter-wave (mmWave) communication, with its larger bandwidths and antenna arrays, inherently facilitates more accurate delay and angle measurements than sub-6 GHz communication, thereby providing opportunities for SLAM. However, none of the existing works have realized the SLAM function under the 5G new radio (NR) standard due to specification and hardware constraints. In this study, we investigate how 5G mmWave communication systems can achieve situational awareness without changing the transceiver architecture and 5G NR standard. We implement 28-GHz mmWave transceivers that deploy OFDM-based 5G NR waveform with 160-MHz channel bandwidth, and we realize beam management following the 5G NR. Furthermore, we develop an efficient successive cancellation-based angle extraction approach to obtain angles of arrival and departure from the reference signal received power measurements. On the basis of angle measurements, we propose an angle-only SLAM algorithm to track UE and map features in the radio environment. Thorough experiments and ray tracing-based computer simulations verify that the proposed angle-based SLAM can achieve submeter-level localization and mapping accuracy with a single base station and without the requirement of strict time synchronization. Our experiments also reveal many propagation properties critical to the success of SLAM in 5G mmWave communication systems.

In this paper, we consider a system with K single-antenna client users, n/sub B/ base stations (each base station has n/sub B/ antennas) as well as a centralized controller. All the base stations operate at the same frequency and have optimal multi-user detection per base-station. A client user could be associated with a single base station at any time. We consider a general problem of uplink macroscopic scheduling where the centralized controller dynamically determines an appropriate association mapping of the K users with respect to the n/sub B/ base stations over a macroscopic time scale. We propose a novel analytical framework for the above macroscopic scheduling problems. A simple rule is to associate a user with the strongest base station (camp-on-the-strongest-cell) and this has been widely employed in conventional cellular systems. However, based on the optimization framework, we found that this conventional approach is in fact not optimal when multi-user detection is employed at the base station. We show that the optimal macroscopic scheduling algorithm is of exponential complexity and we propose a simple greedy algorithm as a feasible solution. It is shown that the macroscopic scheduling gain relative to the conventional approach increases with increasing n/sub B/ (due to the extra degree of freedom introduced by multiple antennas) and decreasing path loss exponent (due to large area of overlapping).

In order to realize high precision comparison between the time of remote user and UTC (NTSC), the National Time Service Center has built a set of high accuracy remote time common-view system based on the satellite common view time transfer method, the underlying system comprised with a base station and some calibration stations and a data processing center. Among them, the base station provides a reference measurement value for the whole system, namely the bias of UTC (NTSC) and the satellite clock. The calibration stations are used to provide a measurement value of the measured stations, namely the bias of local time of calibration station and the satellite clock. The data processing center is responsible for completing the time deviation between the local time of calibration stations and UTC (NTSC). In view of the importance of base station in the system, this paper has designed two kinds of configuration scheme, the single base station and multiple base stations. According to this a large number of tests has been analyzed. The results of experiment describe the single base station is easy to use, its timing accuracy is about 10ns, multi-base stations with higher availability and reliability, and its timing accuracy is 3 ∼ 5ns.

Today more and more bus companies are providing real-time bus locations to their riders to improve passenger experience and increase ridership. Most of the existing bus localization systems rely on the Global Navigation Satellite System (GNSS), such as the Global Positioning System (GPS). However, it is costly to install GNSS receivers and retrofit existing buses to power them, which prevents them to be adopted by those bus operators with tight budgets. There has been increasing interest in developing GPS-free localization schemes that leverage the wireless signals transmitted by the buses to localize them. Such schemes often require the received signal strength (RSS) measured at multiple base stations and therefore are not applicable to a small transportation service with a single base station, such as the shuttle service for a university campus. This paper presents a novel approach that leverages the LoRa link characteristics measured by a single base station and deep learning to localize a campus shuttle when it approaches a stop. Experimental results show that our solution provides a detection accuracy of no less than 92.07% and significantly outperforms all baselines without requiring new hardware and introducing additional communication overhead.

Non-visual effects of office light environment: Field evaluation, model comparison, and spectral analysis

Network MIMO is a technology being developed towards lifting the interference limits on wireless network through collaborative transmissions from multiple base stations. However its great potential is shadowed by the stringent requirement of high speed/capacity backbones facilitating information exchange, including data, control signals, and channel state information amongst the base stations. In this paper, we propose a user-selective collaboration scheme to mitigate the backbone requirement by reducing the information exchange required. We define a certain threshold for users in each base station and only those users exceeding the threshold will be served by multiple base stations collaboratively. The other users will be served by a single base station as in a conventional non-collaborative transmission. The threshold is determined in such a way that the users with collaborative transmissions enjoy maximized sum rates whereas the others without collaborative transmissions sacrifice only marginal potential collaboration gain in terms of achievable maximized sum rates. As the amount of information to be exchanged will be a square function of the number of users served by the collaborative base stations, the user-selective scheme can reduce the backhaul overhead significantly.

Abstract. PPP-RTK has been widely investigated to take the advantages of both real-time kinematic (RTK) and precise point positioning (PPP) techniques. Prior to PPP-RTK, the conventional RTK based on the use of a single base station, on the one hand, has been extended to work within a regional network of multiple base stations, known as network RTK (NRTK). The RTK and NRTK enable fast ambiguity resolution over a short baseline or a local region. PPP, on the other hand, eliminates the need to establish any local network like NRTK, which is able to work in a single receiver mode but it suffers long convergence time in ambiguity resolution. PPP-RTK therefore can provide fast ambiguity resolution capability like RTK and NRTK. Current PPP-RTK techniques however still face challenges in supporting mass-market applications such as mobile devices and autonomous vehicles. Although PPP-RTK system (a combination of RTK and PPP technologies) can help expand the coverage of RTK and speed up the ambiguity resolution in PPP, the deployment and maintenance of a dense network of permanent base stations and a central data processing infrastructure for generation of SSR corrections increases not only the system cost but also the system complexity. This is particularly an obstacle for mass-market applications. In this paper, a new RTK approach is described. First it is based on a single base station state-space-representation (SSR) correction generation strategy to support fast ambiguity resolved PPP. Further it presents a new peer-to-peer propagation strategy to form a real-time dynamically generated network of base stations to support mass-market application users with unbounded coverage. As a result, the new approach eliminates the need to deploy and maintain a dense network of permanent base stations and central data processing infrastructure as required in a conventional PP-RTK system.

An analytical space-time fading correlation for the multi-input-multi-output (MIMO) channel, as a function of antenna spacing, angle spread, and Doppler spread, is derived and is verified with deterministic simulations. We investigate the performance of the uplink spatial fading correlation of a MIMO channel. We consider four uniform circular array (UCA) elements at both mobile station and base station. The angle of arrival and the angle of departure at the base station and the mobile station are distributed by truncated Gaussian and uniform probability distribution function(s) respectively. For large values of N, the simulation and analytical results agree. The results show that spatial separation between antenna elements can be minimized at the base station by employing two or more antennas at the mobile station