Coverage Performance in MIMO-ZFBF Dense HetNets with Multiplexing and LOS/NLOS Path-Loss Attenuation

The performance of multiple-input multiple-output (MIMO) multiplexing heterogenous cellular networks are often analyzed using a single-exponent path-loss model. Thus, the effect of the expected line-of-sight (LOS) propagation in densified settings is unaccounted for, leading to inaccurate performance evaluation and/or inefficient system design. This is due to the complexity of LOS/non-LOS models in the context of MIMO communications. We address this issue by developing an analytical framework based on stochastic geometry to evaluate the coverage performance. We focus on the zero-forcing beamforming where the maximum signal-to-interference ratio is used for cell association. We analytically derive the coverage. We then investigate the cross-stream interference correlation, and develop two approximations of the coverage: Alzer Approximation (A-A) and Gamma Approximation (G-A). The former is often used in the single antenna and single-stream MIMO. We extend A-A to a MIMO multiplexing system and evaluate its utility. We show that the inverse interference is well-fitted by a Gamma random variable, where its parameters are directly related to the system parameters. The accuracy and robustness of G-A is higher than that of A-A. We observe that depending on the multiplexing gain, it is possible to attain the best coverage probability by proper densification

Impact of Beam Misalignment on Hybrid Beamforming NOMA for mmWave Communications

This paper analyzes the effect of beam misalignment on rate performance in downlink of hybrid beamforming-based non-orthogonal multiple access (HB-NOMA) systems. First an HB-NOMA framework is designed in multiuser millimeter wave (mmWave) communications. A sum-rate maximization problem is formulated for HB-NOMA, and an algorithm is introduced to design digital and analog precoders and efficient power allocation. Then, regarding perfectly aligned line-of-sight (LoS) channels, a lower bound for the achievable rate is derived. Next, when the users experience misaligned LoS or non-LoS (NLoS) channels, the impact of beam misalignment is evaluated. To this end, a misalignment factor is modeled and each misaligned effective channel is described in terms of the perfectly aligned effective channel parameters and the misalignment factor. Further, a lower bound for the achievable rate is extracted. We then derive an upper bound for the rate gap expression between the aligned and misaligned HB-NOMA systems. The analyses reveal that a large misalignment can remarkably degrade the rate. Extensive numerical simulations are conducted to verify the findings

Outage probability formulas for cellular networks (contributions for MIMO, CoMP and time reversal features)

L étude de dimensionnement d un réseau cellulaire est une phase de conception qui doit permettre de déterminer les performances d un système dans une configuration donnée. Elle inclut l étude de couverture et l analyse de trafic. De complexes simulations sont possibles pour connaître les paramètres de performances d un réseau mais seules les études analytiques fournissent des résultats rapides. Par ailleurs, pour faire face à la demande de hauts débits, à la rareté du spectre fréquentiel et à l impossibilité d émettre à de plus fortes puissances, de nouvelles techniques de transmissions sont apparues. Nous sommes ainsi passés d un système classique à une seule antenne à des systèmes à multiple antennes et même à des scénarios de coopération entre stations de base. Dans cette thèse, nous proposons des modèles analytiques pour l étude des performances, notamment en termes de probabilités de coupure, de ces évolutions des réseaux cellulaires. Dans une première phase, nous considérons des systèmes multicellulaires à une antenne émettrice et une antenne réceptrice (SISO). Nous proposons deux méthodes d étude de l impact conjoint de l affaiblissement de parcours, de l effet de masque et des évanouissements rapides. Nous étudions, par la suite, un système à large bande utilisant le retournement temporel comme technique de transmission. Dans une deuxième phase, nous considérons des systèmes multicellulaires à antennes multiple à l émission ou à la réception (MISO/MIMO) implémentant les schémas de diversité Alamouti et de combinaison par rapport maximal (MRC). Ensuite, nous considérons un système multicellulaire multi-utilisateurs à précodage de forçage à zéro (ZFBF).The implementation of cellular systems have aroused issues related to the design of cellular networks termed to as network dimensioning. It includes the coverage estimation and thetraffic analysis. Simple models and methods are required to reduce the time consumption of these two analysis. At the same time, the growing demand for higher data rates constrained by the scarcity of frequency spectrum, and the requirements in terms of power consumption reduction make the telecommunication community think about new transmission techniques moving from the classical single antenna systems to multiple antenna systems and even the newly envisaged cooperative systems. In this thesis, we provide analytical models to assess the performance of these different cellular network evolutions in terms of outage probabilities. In a first study, we consider multicellular single input single output (SISO) systems. First, we propose two accurate methods to study the joint impact of path-loss, shadowing and fast fading. This system has so far been studied either considering the only impact of path-loss and Rayleigh fading, or considering the same channel model as in our case but providing very complex outage probability expressions. Then, we provide an outage probability expression in a wideband communication context implementing the Time Reversal (TR) transmission technique considering the impact of fast fading. In a second study, we focus on multiple antenna systems. We study the performance of a Multiple Input Multiple Output (MIMO) system implementing a transmit and a receivediversity schemes namely the Alamouti code and the Maximum Ratio Combining (MRC).PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF

D3.2 First performance results for multi -node/multi -antenna transmission technologies

This deliverable describes the current results of the multi-node/multi-antenna technologies investigated within METIS and analyses the interactions within and outside Work Package 3. Furthermore, it identifies the most promising technologies based on the current state of obtained results. This document provides a brief overview of the results in its first part. The second part, namely the Appendix, further details the results, describes the simulation alignment efforts conducted in the Work Package and the interaction of the Test Cases. The results described here show that the investigations conducted in Work Package 3 are maturing resulting in valuable innovative solutions for future 5G systems.Fantini. R.; Santos, A.; De Carvalho, E.; Rajatheva, N.; Popovski, P.; Baracca, P.; Aziz, D.... (2014). D3.2 First performance results for multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675

Distributed Massive MIMO in Millimetre Wave Communication

This thesis considers a distributed massive MIMO (D-MaMIMO) system for millimetre wave (mmWave) communication for an outdoor coverage area, as the wavelength of mmWave makes it easier and the free space path loss necessitates the use of relatively large distributed antenna arrays. We assume that the line-of-sight (LoS) links are available between the access points (APs) and user equipment (UEs). We have examined different AP arrangements to serve a given square area using the beamforming (BF) for a single user case. Furthermore, the zero-forcing (ZF) pre-coding is applied at a central processing unit (CPU) on the downlink to separate multiple users. We focus on these multi-user scenarios with varying numbers of APs to demonstrate the extent to which closely spaced users can be separated by ZF processing. We examine the determinant of the effective composite channel matrix to demonstrate the conditions under which the ZF problem may become ill-conditioned. We then show that nearly perfect separation is attainable, even when the UEs are only a few metres apart. Subsequently, an eigenvalue decomposition (EVD) based ZF is proposed to improve the performance of multi-antenna UEs. It has been observed that 3DBF has limited scope in circumstances when users are distributed horizontally, near to the same height as the APs and it is advantageous to employ non-square AP antenna arrays to maximize azimuth separation, especially for multi-user environments. The throughput per UE indicates how many users could be served effectively using the aforementioned schemes and AP arrangements for these multi-user cases. We further explore the significant issue of multipath propagation characteristics for mmWave communication and propose the novel distinction between the effective and the environmental K-factor for Ricean channels. A closed-form approximation for the effective K-factor is derived and corroborated by comparison with numerical results

COMPARATIVE ANALYSIS OF USER-CELL ASSOCIATION METHODS FOR MILIMETER WAVE MASSIVE MIMO BY DEVELOPING A SYSTEM LEVEL SIMULATOR FOR HETNETS

Massive multiple-input-multiple-output (MIMO) base station deployments and millimeter wave (mmWave) spectrum utilization have been identified as promising disruptive technologies, along with ultra-dense Heterogeneous Networks (UDHNs) to meet the exponential data requirement of the next generation cellular networks. With the proliferation of UDHNs, optimal user-cell association in cellular networks, which is a well-known open problem, will be exacerbated due to the power differential of macro and small cells. This study investigates the user-cell association problem for ultra-dense two-tier networks with massive MIMO deployment and small cells operating in mmWave spectrum. The association problem is modeled as a convex utility maximization problem, adapted from [11], and is a function of the user throughput. The problem is solved through a centralized subgradient algorithm. Additionally, a game theoretical user-centric distributed load balancing algorithm, inspired from [32], where each user chooses its serving base station to maximize its user throughput selfishly, is also evaluated. Moreover, these adapted algorithms are compared against smallest pathloss and maximum downlink data rate association methods and it is demonstrated via extensive simulations that both the centralized and user-centric approaches almost equally outperform the smallest pathloss and maximum downlink data rate association methodologies in terms of user throughput and cell load distribution. The results exhibit average throughput gains between 20% and 40% for the majority of users if massive MIMO UDHN deployments are operated in the mmWave spectrum as compared to existing sub-6 GHz bands under the optimal user-cell association schemes

D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies

This document provides the most recent updates on the technical contributions and research challenges focused in WP3. Each Technology Component (TeC) has been evaluated under possible uniform assessment framework of WP3 which is based on the simulation guidelines of WP6. The performance assessment is supported by the simulation results which are in their mature and stable state. An update on the Most Promising Technology Approaches (MPTAs) and their associated TeCs is the main focus of this document. Based on the input of all the TeCs in WP3, a consolidated view of WP3 on the role of multinode/multi-antenna transmission technologies in 5G systems has also been provided. This consolidated view is further supported in this document by the presentation of the impact of MPTAs on METIS scenarios and the addressed METIS goals.Aziz, D.; Baracca, P.; De Carvalho, E.; Fantini, R.; Rajatheva, N.; Popovski, P.; Sørensen, JH.... (2015). D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675