Efficient use of paired spectrum bands through TDD small cell deployments

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Traditionally, wireless cellular systems have been designed to operate in frequency division duplexing (FDD) paired bands that allocate the same amount of spectrum for both downlink (DL) and uplink (UL) communications. Such design is very convenient under symmetric DL/UL traffic conditions, as it used to be the case when voice transmission was predominant. However, due to the overwhelming advent of data services, which involves large asymmetries between DL and UL, the conventional FDD solution becomes inefficient. In this regard, flexible duplexing concepts aim to derive procedures to improve spectrum utilization by adjusting resources to actual traffic demand. In this work, we review these concepts and propose the introduction of time division duplexing (TDD) small eNBs (SeNB) to operate in the unused resources of an FDD-based system. This proposal alleviates the saturated DL/UL transmission commonly found in FDD-based systems through user offloading towards a TDD system based on SeNBs. In this context, the flexible duplexing concept is analyzed from three points of view: a) regulation, b) long term evolution (LTE) standardization, and c) technical solutions.Peer ReviewedPostprint (published version

Radio Resource Management in NB-IoT Systems:Empowered by Interference Prediction and Flexible Duplexing

NB-IoT is a promising cellular technology for enabling low cost, low power, long-range connectivity to IoT devices. With the bandwidth requirement of 180 kHz, it provides the flexibility to deploy within the existing LTE band. However, this raises serious concerns about the performance of the technology due to severe interference from multi-tier 5G HetNets. Furthermore, as NB-IoT is based on HD-FDD, the symmetric allocation of spectrum band between the downlink and uplink results in underutilization of resources, particularly in the case of asymmetric traffic distribution. Therefore, an innovative RRM strategy needs to be devised to improve spectrum efficiency and device connectivity. This article presents the detailed design challenges that need to be addressed for the RRM of NB-IoT and proposes a novel framework to devise an efficient resource allocation scheme by exploiting cooperative interference prediction and flexible duplexing techniques

Policy-Based Flexible Spectrum Usage for Next-Generation Mobile Communication Networks

Tato diplomová práce se zabívá návrhem algoritmu pro flexibilní sdílení spektra (FSU) založeného na pravidlech dohodnutých mezi operátory. V úvodu jsou uvedeny základní informace o mobilní komunikační síti nové generace ITM – Advanced. Po úvodní části je věnována pozornost technologiim vhodných pro implementaci flexibilního sdílení spektra. Pozornost je také věnována veličinám použitých pro vyhodnocení efektivity algoritmu flexibilního sdílení spektra. Je navrženo několik algoritmu flexibilního sdílení spektra využívajícího hodnot poměru signálu ku interferenci a šumu (SINR). Hodnoty SINR jsou použity pro vypořádání se se vzájemnou interferencí, která je způsobena koexistencí několika operátorů ve stejné zeměpisné oblasti, sdílejících společné frekvenční pásmo. V úvahu jsou také brány u každého operátora individuální potřeby datových přenosů a jejich kvality. Halvním cílem je maximálně zvýšit datovou propustnost každé buňky, stejně tak i rychlost přenosu dat pro jednotlivé uživatele připojených k domácí základové stanici (HBS). Pro simulaci navrženého algoritmu je použito rozmístění čtyř domácích základových stanic (HBS) v jednopatrové budově s náhodným počtem uživatelů z daného rozsahu. Každý operator dělá nezávislá rozhodnutí bez jakékoliv výměny signalizačních dat s ostatními operátory. Jediné možné informace, které může operátor využívat jsou získané snímáním spektra z jeho okolí. K řešení tohoto problému je předpokládáno využití kognitivního rádia (CR).This Master's thesis deals with proposal of Flexible Spectrum Usage (FSU) algorithm based on policy agreed among operators. The introduction presents basic information about properties of next generation mobile communication ITM-Advanced system. After the introductory part the attention is given to the items efficient for FSU implementation as well as parameters used for evaluation of FSU algorithm efficiency. Several variants policy based FSU algorithm utilize value of Signal to Interference plus Noise Ratio (SINR) is designed. The SINR information is used to combat with mutual interference which is caused by coexistence of several operators in the same geographical area sharing over the same spectrum pool. Individual needed as traffic and quality of service requirements of each operator is taken into consideration as well. The main aim is to maximize cell troughput as well as data- rates for each user of HBS. For simulation of proposal algorithm is considered deployment of four Currently Home Base Stations (HBS) in indoor loacal area scenerio with random number of users in given range. Each operator makes independent dicision without signalling exchange among other. The only considered information that HBS can use is gotten by scenning its environment. This problem soliving is considered to use Cognitive Radio (CR)

Experimental evaluation of flexible duplexing in multi-tier MIMO networks

In this paper, we present an experimental evaluation of the performance benefits provided by flexible duplexing, an access technique that allows uplink and downlink cells to coexist within the same time-frequency resource blocks. In order to replicate a wireless multi-tier network composed of 1 macro-cell and 2 small cells, a measurement campaign has been conducted using an indoor wireless testbed comprised of a total of 6 multiple-input multiple-output (MIMO) software-defined radio (SDR) devices. Since each cell has a single active user, each uplink/downlink configuration can be identified with a different interference channel, over which interference alignment (IA) is used as an inter-cell interference management technique and compared to other existing methods. The obtained results show that flexible duplexing clearly outperforms the conventional time-division duplex (TDD) access approach, where all cells operate synchronized either in uplink or dowlink mode. Additionally, interference alignment consistently provides better results in most of the interference regimes when compared to minimum means quare error (MMSE)-based schemes. The impact of channel estimate quality on the different communication strategies is also studied. It is worth highlighting that the presented over-the-air (OTA) experiments represent the first implementation of IA with real-time precoding and decoding.The work of Jacobo Fanjul, Jesús Ibáñez and Ignacio Santamaria has been supported by the Ministerio de Economía, Industria y Competitividad (MINECO) of Spain, and AEI/FEDER funds of the E.U., under grant TEC2016-75067-C4-4-R (CARMEN), grant PID2019-104958RB-C43 (ADELE), and FPI grant BES-2014-069786. The work of José A. García-Naya has been funded by the Xunta de Galicia (ED431G2019/01), the Agencia Estatal de Investigación of Spain (TEC2016-75067-C4-1-R, RED2018-102668-T), and ERDF funds of the E.U. (AEI/FEDER, UE)

Signal-timing offset compensation in dense TDD OFDM-based networks

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Orthogonal Frequency Division Multiplexing (OFDM)-based networks rely on time synchronization to obtain their best performance. Time synchronization with neighboring nodes can be satisfied by increasing the cyclic prefix (CP) length (at the expenses of spectral efficiency reduction) We show that by optimizing the transmit pre-compensation and receive post-compensation we can meet the time synchronization constraints and keep the CP at its minimum value. This concept is applied to paired-bands Frequency Division Duplexing (FDD) systems which tend to show inefficient occupancy of the uplink (UL)-band due to the traffic asymmetry. We consider the possibility of deploying multiple Time Division Duplexing (TDD) small eNBs (SeNBs) in the unused UL spectrum. In this scenario, time synchronization with macro eNB (MeNB) and neighboring SeNBs becomes essential. Two algorithms are proposed in order to ensure orthogonality of OFDM transmissions network-wide.Peer ReviewedPostprint (author's final draft

Power minimization in multi-tier networks with flexible duplexing

In this paper we present an algorithm to minimize transmit power in multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) with flexible duplexing, a promising strategy that allows the coexistence of uplink and downlink cells within the same time and frequency resource block. First, the proposed algorithm minimizes transmit power for a given uplink/downlink (UL/DL) combination, and afterwards, the optimal solution out of the explored UL/DL combinations is selected. To reduce the computational cost of exploring all the UL/DL settings, we propose a hierarchical switching (HS) approach that considers a reduced subset of transmit directions. By means of Monte Carlo simulations, we show that the proposed technique provides significant power savings with respect to a conventional time-division duplex (TDD) scheme.This work has been supported by the MINECO of Spain and AEI/FEDER funds from the EU, under grant TEC2016-75067-C4-4-R (CARMEN project) and FPI grant BES-2014-069786