Linear space-time modulation in multiple-antenna channels

This thesis develops linear space–time modulation techniques for (multi-antenna) multi-input multi-output (MIMO) and multiple-input single-output (MISO) wireless channels. Transmission methods tailored for such channels have recently emerged in a number of current and upcoming standards, in particular in 3G and "beyond 3G" wireless systems. Here, these transmission concepts are approached primarily from a signal processing perspective. The introduction part of the thesis describes the transmit diversity concepts included in the WCDMA and cdma2000 standards or standard discussions, as well as promising new transmission methods for MIMO and MISO channels, crucial for future high data-rate systems. A number of techniques developed herein have been adopted in the 3G standards, or are currently being proposed for such standards, with the target of improving data rates, signal quality, capacity or system flexibility. The thesis adopts a model involving matrix-valued modulation alphabets, with different dimensions usually defined over space and time. The symbol matrix is formed as a linear combination of symbols, and the space-dimension is realized by using multiple transmit and receive antennas. Many of the transceiver concepts and modulation methods developed herein provide both spatial multiplexing gain and diversity gain. For example, full-diversity full-rate schemes are proposed where the symbol rate equals the number of transmit antennas. The modulation methods are developed for open-loop transmission. Moreover, the thesis proposes related closed-loop transmission methods, where space–time modulation is combined either with automatic retransmission or multiuser scheduling.reviewe

Performance analysis of multi-antenna and multi-user methods for 3G and beyond

Performance of cellular networks has become an issue with forecasted growing public demand for medium and high data rate services. Motivated by these expectations multi-antenna techniques such as transmit diversity (TD), channel-aware scheduling and multiple-input multiple-output (MIMO) transceivers have received a lot of enthusiasm within wireless communications community. We first focus on closed-loop (CL) TD and introduce extended mode 1 and 2 (e-mode 1 and 2) algorithms that are designed based on universal terrestrial radio access (UTRA) frequency division duplex (FDD) CL mode 1 and 2. We derive analytical performance results for e-mode 1 and 2 in terms of signal to noise ratio (SNR) gain, link capacity and bit error probability (BEP). We also consider the effect of feedback errors to the performance of closed-loop system. In the analysis of channel-aware scheduling we focus on on-off scheduling (OOS) where user's feedback consists of only a single bit. Performance results in both downlink and uplink clearly indicate that most of the achievable gain from channel-aware scheduling can be obtained with very scarce channel state information (CSI). Results also show that the design of feedback channel is of great importance because feedback errors may seriously degrade the system performance. The third topic of the thesis concentrates on MIMO techniques that can be implemented in UTRA FDD uplink without major revisions to the current air interface. We show that the UTRA FDD uplink coverage and capacity performance can be boosted by single-input multiple-output (SIMO) and MIMO transceivers. The information MIMO employing parallel multiplexing instead of transmit diversity shows its potential when extremely high user data rates are needed.Solukkoverkkojen suorituskyky on noussut tärkeään rooliin nopeiden datapalveluiden kasvuennusteiden myötä. Näiden kasvuodotusten perusteella moniantennitekniikat kuten lähetysdiversiteetti, kanavan huomioon ottava lähetyksen aikataulutus sekä useaa samanaikaista datavirtaa tukevat lähetinvastaanotinmenetelmät ovat saaneet osakseen paljon kiinnostusta langattoman tietoliikenteen tutkijayhteisössä. Tutkimuksessa keskitytään aluksi suljettua säätöä käyttäviin lähetysdiversiteettimenetelmiin, missä yhteydessä esitellään laajennetut moodien 1 ja 2 algoritmit, jotka on aiemmin kehitetty kolmannen sukupolven WCDMA järjestelmän suljetun säädön moodien 1 ja 2 pohjalta. Laajennetuille moodien 1 ja 2 algoritmeille johdetaan analyyttisiä suorituskykytuloksia käyttäen mittarina signaali-kohinasuhteen parannusta, linkin kapasiteettia sekä bittivirheiden todennäköisyyttä. Myös säätövirheiden vaikutusta järjestelmän suorituskykyyn tarkastellaan. Lähetyksen aikataulutuksen analyysi painottuu kytkettyyn aikataulutukseen, missä käyttäjän säätöinformaatio sisältyy yhteen bittiin. Sekä ylä- että alalinkin suorituskykytulokset osoittavat selvästi, että suurin osa mahdollisesta parannuksesta voidaan saavuttaa hyvin karkeaan kanavatilan informaatioon perustuen. Tulokset osoittavat myös, että säätökanavan suunnittelu on tärkeää, koska säätövirheet voivat vakavasti heikentää järjestelmän suorituskykyä. Kolmannessa aihealueessa keskitytään moniantennitekniikoihin, jotka voidaan toteuttaa WCDMA järjestelmän ylälinkissä ilman perustavanlaatuisia muutoksia nykyiseen ilmarajapintaan. Tutkimuksessa osoitetaan, että ylälinkin peittoa ja kapasiteettia voidaan parantaa tutkituilla moniantennitekniikoilla olipa lähettimessä yksi tai useampia antenneja. Menetelmä, jossa informaatio jaetaan useisiin rinnakkaisiin datavirtoihin sen sijaan että käytettäisiin vain yhtä datavirtaa, osoittautuu erityisen lupaavaksi kun tarvitaan hyvin nopeita tiedonsiirtoyhteyksiä.reviewe

Power control for WCDMA

This project tries to introduce itself in the physical implementations that make possible the denominated third generation mobile technology. As well as to know the technology kind that makes possible, for example, a video-call in real time. During this project, the different phases passed from the election of WCDMA like the access method for UMTS will appear. Its coexistence with previous network GSM will be analyzed, where the compatibility between systems has been one of the most important aspects in the development of WCDMA, the involved standardization organisms in the process, as well as the different protocols that make the mobile communications within a network UTRAN possible. Special emphasis during the study of the great contribution that has offered WCDMA with respect to the control of power of the existing signals will be made. The future lines that are considered in the present, and other comment that already are in their last phase of development in the field of the mobile technology. UMTS through WCDMA can be summarized like a revolution of the air interface accompanied by a revolution in the network of their architecture

Over-the-air test configurations for MIMO in Long Term Evolution

One of the main challenges for the mobile industry is the growing demand for the high speed mobile data. The 3GPP (3rd Generation Partner Project) is the organization that specifies most mobile data communication standards used globally. For the demand for high data rates, 3GPP has specified LTE (Long Term Evolution). One solution included in LTE among many is the MIMO (Multiple Input Multiple Output) technology. This thesis discusses the basic features included in LTE Release 9 focusing on MIMO-technology. This thesis also discusses the MIMO-OTA (Over-the-Air) testing configurations introduced in 3GPP Technical Report 37.976. These configurations are divided into two main types: anechoic chamber-based environments and reverberation chamber-based environments. 3GPP divides these two methods into five different anechoic chamber methods and two reverberation chamber methods. Testing MIMO-technology in LTE introduces new requirements for OTA-testing. While test requirements for GSM and WCDMA networks have included TRS (Total Radiated Sensitivity) and TRP (Total Radiated Power), the LTE MIMO testing adds the requirements for throughput testing. When using MIMO-configurations, the throughput depends on power transmitted to UE (User Equipment) that depends on the position of the UE. Addition to that, the throughput also depends on used TM (Transmission Mode). So test specifications need to include throughput tests for all TMs. Performance of TMs and the overall performance of MIMO cannot be tested in traditional OTA-measurement chambers because the transmission channels in traditional OTA-chambers are configured to be as simple as possible, so that the power and sensitivity measurements could be repeatable. Suggestions for LTE testing chambers have included configuring the transmission channel to be more versatile. This has been achieved by methods such as using multiple antennas or including a channel emulator to the system. Using these methods, the UE’s MIMO performance can be tested in different channel environments in laboratory, therefore improving possibilities for research and development.Opinnäytetyössä tutkittiin LTE-teknologian perusperiaatteita keskittyen siihen sisälletyn MIMO-tekniikan toimintaan. Opinnäytetyö tutki myös 3GPP:n TR 37.976 -raportissa esiteltyjä testausympäristövaihtoehtoja. Nämä jakautuvat 2 pääkategoriaan: kaiuttoman kammion järjestelmiin ja heijastavan kammion järjestelmiin. 3GPP jakaa nämä vielä 5:een eri kaiuttoman kammion järjestelmään ja 2:een heijastamattoman kammion järjestelmään. MIMO-tekniikan testaaminen LTE-teknologiassa asettaa suuria vaatimuksia OTA-testaamiselle. GSM- ja WCDMA-verkkojen testaamiseen ovat riittäneet vain herkkyysmittaukset (Total Radiated Sensitivity, TRS) ja tehomittaukset (Total Radiated Power, TRP). LTE:n MIMO-tekniikka lisää testausvaatimuksiin tiedonsiirtonopeuden, joka on MIMO-tekniikkaa käytettäessä riippuvainen herkkyydestä ja lähetetystä sekä vastaanotetusta tehosta, jotka riippuvat puhelimen asennosta. Näiden lisäksi tiedonsiirtonopeus riippuu myös MIMO:n käyttämien siirtotapojen (Transmission Mode, TM) toiminnasta. Siirtotapojen ja MIMO:n toimintaa ei pystytä testaamaan perinteisissä OTA-mittauskammioissa, sillä näissä siirtokanava on yritetty tehdä yksinkertaiseksi, jotta tehojen ja herkkyyden mittaukset olisivat mahdollisimman toistettavia. LTE:n MIMO-testauksen vaatimissa mittauskammioissa on pyritty tekemään siirtokanavasta mahdollisimman monimuotoinen. Tähän on pyritty eri ympäristövaihtoehdoissa erilaisin menetelmin, kuten käyttäen useaa antennia tai kanavaemulaattoria. Tällöin pystytään testaamaan laitteen MIMO:n toimintaa erilaisissa reaalimaailman ympäristöissä laboratorio-olosuhteissa

Studies on 6-sector-site deployment in downlink LTE

Mobile data traffic is expected to increase massively in the following years. Consequently, service operators are induced to increase the capacity of their networks continually to attract more subscribers and maximize their revenues. At the same time, they want to minimize operational costs and capital expenditures. Among the alternatives that aim to increase the network capacity, higher order sectorization, and in particular a six sectorized configuration, is nowadays attracting a lot of attention for LTE macro-cell deployments since a higher number of sectors per site results in improved site capacity and coverage. A six sectorized configuration is attractive for both roll-out phase and growth phase of the network. In the roll-out phase, the radio access network is planned with 6-sector sites instead of 3-sector sites with the advantage that less sites are needed for the same capacity and coverage requirements. In the growth phase, the six sectorized configuration can be used to upgrade existing 3-sector sites where the traffic grows beyond the current sites' capabilities. Therefore, no additional expensive and time consuming contracts need to be signed for the locations of the new sites, while the existing sites are used more efficiently. However, although potentially a 6-sector site can offer a double capacity than a 3-sector site, several factors prevent the capacity from growing proportionately to the number of sectors. Consequently, there is an uncertainty on whether the capacity gain is high enough to justify the extra costs of the additional equipment and, more specifically, whether the 6-sector-site deployment is more economically attractive than a 3-sector-site deployment. The aim of this report is to solve this uncertainty. First, we present the main factors that affect the capacity gain. Next, we quantify the impact of these factors on the capacity gain in downlink LTE with the use of a system level simulator. Finally, we use the results of the simulation study as inputs for an economic study to access the reasons for a possible deployment of 6-sector sites instead of 3-sector sites for LTE

Adaptive Beamforming and Adaptive Modulation-Assisted Network Performance of Multiuser Detection-Aided FDD and TDD CDMA Systems

The network performance of a frequency division duplex and time division duplex (TDD) code division multiple access (CDMA)-based system is investigated using system parameters similar to those of the Universal Mobile Telecommunication System. The new call blocking and call dropping probabilities, the probability of low-quality access, and the required average transmit power are quantified both with and without adaptive antenna arrays (AAAs), as well as when subjected to shadow fading. In some of the scenarios investigated, the system’s user capacity is doubled with the advent of adaptive antennas. The employment of adaptive modulation techniques in conjunction with AAAs resulted in further significant network capacity gains. This is particularly so in the context of TDD CDMA, where the system’s capacity becomes poor without adaptive antennas and adaptive modulation owing to the high base station (BS) to BS interference inflicted as a consequence of potentially using all time slots in both the uplink and downlink of the emerging wireless Internet. Index Terms—Adaptive beamforming, adaptive modulation, code division multiple access (CDMA) systems, Universal Mobile Telecommunication System Terrestrial Radio Access (UTRA), wireless network performance

Antenna arrays for the downlink of FDD wideband CDMA communication systems

The main subject of this thesis is the investigation of antenna array techniques for improving the performance of the downlink of wideband code division multiple access (WCDMA) mobile communication systems. These communication systems operate in frequency division duplex (FDD) mode and the antenna arrays are employed in the base station. A number of diversity, beamforming and hybrid techniques are analysed and their bit error ratio (BER) versus signalto- noise ratio (SNR) performance is calculated as a function of the eigenvalues of the mean channel correlation matrix, where this is applicable. Also, their BER versus SNR performance is evaluated by means of computer simulations in various channel environments and using different numbers of transmit antenna elements in the base station. The simulation results of the techniques, along with other characteristics, are compared to examine the relationship among their performance in various channel environments and investigate which technique is most suitable for each channel environment. Next, a combination of the channel correlation matrix eigenvalue decomposition and space-time processing is proposed as a possible open loop approach to the downlink data signal transmission. It decomposes the channel into M components in the form of eigenvectors (M is the number of transmit antennas in the base station), and attempts to minimise the transmit power that is needed to achieve a target BER at the mobile receiver by employing the optimum number of these eigenvectors. The lower transmit power and the directional transmission by means of eigenvectors are expected to lower interference levels to non-desired users (especially to those users who are not physically close to the direction(s) of transmission). Theoretical and simulation results suggest that this approach performs better than other presented open loop techniques, while the performance gain depends on M and the channel environment. In simulations it is usually assumed that the base and mobile station have access to perfect estimates of all needed parameters (e.g. channel coecients). However, in practical systems they make use of pilot and/or feedback signals to obtain estimates of these parameters, which result in noisy estimates. The impact of the noisy estimates on the performance of various techniques is investigated by computer simulations, and the results suggest that there is typically some performance loss. The loss depends on the parameter that is estimated from pilot signals, and may be a function of M, SNR and/or the channel environment. In certain beamforming techniques the base station operates the transmit antenna array in an open loop fashion by estimating the downlink weight vector from the directional information of the uplink channel. Nevertheless, in FDD systems this results in performance loss due to the separation between the uplink and downlink carrier frequencies (`FDD gap'). This loss is quantified and the results show that it is a function of M and the FDD gap. Also, a very simple technique for compensating this loss is proposed, and results obtained after its application suggest that it eliminates most of the loss. Comparison of the proposed technique with an existing compensation technique suggests that, even though the latter is more complex than the former, it yields very little additional improvement

An adaptive step size power control with transmit power control command aided mobility estimation

Power control is one of the most important mechanisms influencing on the maximum capacity and performance of Wideband Code Division Multiple Access (WCDMA) systems. Power control algorithms used in Universal Mobile Telecommunication System (UMTS) are based on fixed step size algorithms. The algorithms adjust their transmitted power based on Transmit Power Control (TPC) commands. In this paper, we show that there is a significant correlation between TPC sequences and user mobility. We then introduce a new parameter called Consecutive TPC Ratio (CTR), which will be varied by user speeds. A new adaptive power control algorithm is also proposed. This new power control algorithm uses CTRs to adjust power control step sizes. The result shows that the proposed algorithm outperforms fixed step power control