AirSync: Enabling Distributed Multiuser MIMO with Full Spatial Multiplexing

The enormous success of advanced wireless devices is pushing the demand for higher wireless data rates. Denser spectrum reuse through the deployment of more access points per square mile has the potential to successfully meet the increasing demand for more bandwidth. In theory, the best approach to density increase is via distributed multiuser MIMO, where several access points are connected to a central server and operate as a large distributed multi-antenna access point, ensuring that all transmitted signal power serves the purpose of data transmission, rather than creating "interference." In practice, while enterprise networks offer a natural setup in which distributed MIMO might be possible, there are serious implementation difficulties, the primary one being the need to eliminate phase and timing offsets between the jointly coordinated access points. In this paper we propose AirSync, a novel scheme which provides not only time but also phase synchronization, thus enabling distributed MIMO with full spatial multiplexing gains. AirSync locks the phase of all access points using a common reference broadcasted over the air in conjunction with a Kalman filter which closely tracks the phase drift. We have implemented AirSync as a digital circuit in the FPGA of the WARP radio platform. Our experimental testbed, comprised of two access points and two clients, shows that AirSync is able to achieve phase synchronization within a few degrees, and allows the system to nearly achieve the theoretical optimal multiplexing gain. We also discuss MAC and higher layer aspects of a practical deployment. To the best of our knowledge, AirSync offers the first ever realization of the full multiuser MIMO gain, namely the ability to increase the number of wireless clients linearly with the number of jointly coordinated access points, without reducing the per client rate.Comment: Submitted to Transactions on Networkin

IST-2000-30148 I-METRA: D3.1 Design, analysis and selection of suitable algorithms

This deliverable contains a description of the space-time coding algorithms to be simulated within the I-METRA project. Different families of algorithms have been selected and described in this document with the objective of evaluating their performance. One of the main objectives of the I-METRA project is to impact into the current standardisation efforts related to the introduction of Multiple Input Multiple Output (MIMO) configurations into the High Speed Downlink and Uplink Packet Access concepts of UMTS (HSDPA and HSUPA). This required a review of the current specifications for these systems and the analysis of the impact of the potential incorporation of the selected MIMO schemes.Preprin

The new enhancement of UMTS: HSDPA and HSUPA

During the last two decades, the world of the mobile communications grew a lot, as a consequence of the increasing necessity of people to communicate. Now, the mobile communications still need to improve for satisfies the user demands. The new enhancement of UMTS in concrete HSDPA and HSUPA is one of these improvements that the society needs. HSDPA and HSUPA which together are called HSPA, give to the users higher data rates in downlink and uplink. The higher data rates permit to the operators give more different types of services and at the same time with better quality. As a result, people can do several new applications with their mobile terminals like applications that before a computer and internet connection were required, now it is possible to do directly with the mobile terminal. This thesis consists in study these new technologies denominated HSDPA and HSUPA and thus know better the last tendencies in the mobile communications. Also it has a roughly idea about the future tendencies

Energy-efficient wireless communication

In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters

LTE Multicodeword-MIMO; Hybrid-ARQ performance studies

Langattomassa tiedonsiirrossa on tällä hetkellä meneillään suuria muutoksia, sitten ensimmäisen matkapuhelinsukupolven käyttöönoton. Uusia datapuhelimia, kuten myös kämmentietokoneita käytetään internetin selaamiseen, videoiden katselemiseen ja pelaamiseen matkapuhelinverkon kautta. Voidaakseen tyydyttämään kuluttajien vaatimukset, tarve uusien langattoman tiedonsiirron normien luomiseen on merkittävä. Long Term Evolution (LTE) on, Third Generation Partership Project:in (3GPP) johtama, ehdokas seuraavaksi matkapuhelinsukupolven standardiksi. LTE:n ominaisuuksiin kuuluvat mm. korkea suoritusteho, matala latenssi, yksinkertaisuus ja alhaiset kustannukset. Tulevassa standardissa on aihealueita, joita ei ole varsinaisesti tutkittu akateemisessa maailmassa kuten Hybrid Automatic Repeat Request:in (HARQ) suorituskykyä. Koska langaton tiedonsiirto on epälineaarinen prosessi, sitä mallinnetaan simulaattorin avulla. Simulaattori on tehty MATLAB ympäristössä LTE:n standardien mukaisesti. Kolme eri Multiple Input Multiple Output (MIMO) downlink HARQ skenaariota luotiin ja niiden suorituskykyä arvioitiin. Pääpaino työn tutkimukselle kohdistuu kolmen HARQ:n suorituskykyyn, tosin simulaattorimallin todistaminen on myös keskeinen osa tätä työtä.Mobile communication is going through major changes since the introduction of first generation mobile phones. Not only phones, but various handheld devices are starting to use the mobile communication network for internet browsing, multimedia or even online gaming. There is a high need for fast mobile connection and therefore new standards and specifications need to be created to satisfy the consumer requirements. Long Term Evolution (LTE) is the latest candidate for the next mobile communication standard led by Third Generation Partnership Project (3GPP). LTEs main features are high throughput, low latency, simple architecture and low operating costs. Since mobile data transmission is a non linear process, a simulator is built to model the procedure. Simulator made for this thesis was written in MATLAB meeting the 3GPPs set standards for LTE. Three different Multiple Input Multiple Output (MIMO) downlink HARQ scenarios were created and their performance was evaluated. The main focus of this thesis is the performance comparison of the three downlink scenarios; however the verification of the simulator model plays also a significant role in this work

On-board processing satellite network architecture and control study

The market for telecommunications services needs to be segmented into user classes having similar transmission requirements and hence similar network architectures. Use of the following transmission architecture was considered: satellite switched TDMA; TDMA up, TDM down; scanning (hopping) beam TDMA; FDMA up, TDM down; satellite switched MF/TDMA; and switching Hub earth stations with double hop transmission. A candidate network architecture will be selected that: comprises multiple access subnetworks optimized for each user; interconnects the subnetworks by means of a baseband processor; and optimizes the marriage of interconnection and access techniques. An overall network control architecture will be provided that will serve the needs of the baseband and satellite switched RF interconnected subnetworks. The results of the studies shall be used to identify elements of network architecture and control that require the greatest degree of technology development to realize an operational system. This will be specified in terms of: requirements of the enabling technology; difference from the current available technology; and estimate of the development requirements needed to achieve an operational system. The results obtained for each of these tasks are presented

Link-to-System Interfaces for System Level Simulations Featuring Hybrid ARQ

Projecte de final de carrera fet en col.laboració amb Technische Universität München. Lehrstuhl für KommunikationsnetzeWithin the continuous evolution of wireless communications, new and ambitious requirements are planned to be met by next generation of mobile communications. In order to achieve those requirements, new technologies and mechanisms that work well over broadband frequency, like OFDM and OFDMA, need to be investigated, developed and tested in simulators. New cellular systems designs are based on exploiting instantaneous channel conditions, improving the system performance. Due to this, system level simulations must support a Physical Layer (PHY) abstraction which accurately predicts the instantaneous performance of the link layer. In order to accomplish this, a new link-to-system (L2S) interface has been developed and implemented in OpenWNS, a system level simulator for evaluation of OFDM systems developed at RWTH, Aachen. This interface is mainly realized through a set of mapping mechanisms, used to provide a BLER given a received coded block SINR. Together with the theoretical study and evaluation of these mappings mechanisms, this thesis will analyze and evaluate Hybrid Automatic Repeat Request mechanisms (H-ARQ), and how these protocols can be implemented in system level simulators working together with the L2S interface. This thesis shows how the new L2S interface is more accurate than past approaches, providing a gain of around 3 dB. Concerning H-ARQ protocols, the results show how the use of these new techniques provides a considerable gain with respect to normal ARQ or not using any such techniqu

Subcarrier and Power Allocation in WiMAX

Worldwide Interoperability for Microwave Access (WiMAX) is one of the latest technologies for providing Broadband Wireless Access (BWA) in a metropolitan area. The use of orthogonal frequency division multiplexing (OFDM) transmissions has been proposed in WiMAX to mitigate the complications which are associated with frequency selective channels. In addition, the multiple access is achieved by using orthogonal frequency division multiple access (OFDMA) scheme which has several advantages such as flexible resource allocation, relatively simple transceivers, and high spectrum efficient. In OFDMA the controllable resources are the subcarriers and the allocated power per subband. Moreover, adaptive subcarrier and power allocation techniques have been selected to exploit the natural multiuser diversity. This leads to an improvement of the performance by assigning the proper subcarriers to the user according to their channel quality and the power is allocated based on water-filling algorithm. One simple method is to allocate subcarriers and powers equally likely between all users. It is well known that this method reduces the spectral efficiency of the system, hence, it is not preferred unless in some applications. In order to handle the spectral efficiency problem, in this thesis we discuss three novel resources allocation algorithms for the downlink of a multiuser OFDM system and analyze the algorithm performances based on capacity and fairness measurement. Our intensive simulations validate the algorithm performances.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Link abstraction models based on mutual information for LTE downlink

Postprint (author’s final draft