Non-coherent slot synchronization techniques for WCDMA systems

This Thesis investigates a host of new synchronization techniques for WCDMA. We assume the presence of more than one base station (BS) (multi-target) in the vicinity of the mobile station (MS), and consider the effects of multipath, Raleigh fading, and different carrier frequency offsets. Through the Thesis, we concentrate on the first stage of the three-stage cell search procedure which is slot synchronization. The slot synchronization stage has been always the most challenging stage since it deals with the largest amount of uncertainty in the cell search, and it determines the timing resolution to the other two stages. We also introduce the concept of using parallel code verification circuits to be added to the state of art pipelined techniques to yield better synchronization results. The received WCDMA synchronization codes are combined in different scenarios according to the proposed non-coherent synchronization technique. The results are compared with recent approaches of combining the WCDMA synchronization codes. The comparison reveals some improvements in the mean synchronization time for some of our rules herein. It also shows superiority of the new rules for different carrier frequency offsets especially at low signal to interference ratios

Indoor Radio Measurement and Planning for UMTS/HSPDA with Antennas

Over the last decade, mobile communication networks have evolved tremendously with a key focus on providing high speed data services in addition to voice. The third generation of mobile networks in the form of Universal Mobile Telecommunications System (UMTS) is already offering revolutionary mobile broadband experience to its users by deploying High Speed Downlink Packet Access (HSDPA) as its packet-data technology. With data speeds up to 14.4 Mbps and ubiquitous mobility, HSDPA is anticipated to become a preferred broadband access medium for end-users via mobile phones, laptops etc. While majority of these end-users are located indoors most of the time, approximately 70-80% of the HSDPA traffic is estimated to originate from inside buildings. Thus for network operators, indoor coverage has become a necessity for technical and business reasons. Macro-cellular (outdoor) to indoor coverage is a natural inexpensive way of providing network coverage inside the buildings. However, it does not guarantee sufficient link quality required for optimal HSDPA operation. On the contrary, deploying a dedicated indoor system may be far too expensive from an operator\u27s point of view. In this thesis, the concept is laid for the understanding of indoor radio wave propagation in a campus building environment which could be used to plan and improve outdoor-to-indoor UMTS/HSDPA radio propagation performance. It will be shown that indoor range performance depends not only on the transmit power of an indoor antenna, but also on the product\u27s response to multipath and obstructions in the environment along the radio propagation path. An extensive measurement campaign will be executed in different indoor environments analogous to easy, medium and hard radio conditions. The effects of walls, ceilings, doors and other obstacles on measurement results would be observed. Chapter one gives a brief introduction to the evolution of UMTS and HSDPA. It goes on to talk about radio wave propagation and some important properties of antennas which must be considered when choosing an antenna for indoor radio propagation. The challenges of in-building network coverage and also the objectives of this thesis are also mentioned in this chapter. The evolution and standardization, network architecture, radio features and most importantly, the radio resource management features of UMTS/HSDPA are given in chapter two. In this chapter, the reason why Wideband Code Division Multiple Access (WCDMA) was specified and selected for 3G (UMTS) systems would be seen. The architecture of the radio access network, interfaces with the radio access network between base stations and radio network controllers (RNC), and the interface between the radio access network and the core network are also described in this chapter. The main features of HSDPA are mentioned at the end of the chapter. In chapter three the principles of the WCDMA air interface, including spreading, Rake reception, signal fading, power control and handovers are introduced. The different types and characteristics of the propagation environments and how they influence radio wave propagation are mentioned. UMTS transport, logical and physical channels are also mentioned, highlighting their significance and relationship in and with the network. Radio network planning for UMTS is discussed in chapter four. The outdoor planning process which includes dimensioning, detailed planning, optimization and monitoring is outlined. Indoor radio planning with distributed antenna systems (DAS), which is the idea and motivation behind this thesis work, is also discussed. The various antennas considered and the antenna that was selected for this thesis experiment was discussed in chapter five. The antenna radiation pattern, directivity, gain and input impedance were the properties of the antenna that were taken into consideration. The importance of the choice of the antenna for any particular type of indoor environment is also mentioned. In chapter six, the design and fabrication of the monopole antennas used for the experimental measurement is mentioned. The procedure for measurement and the equipment used are also discussed. The results gotten from the experiment are finally analyzed and discussed. In this chapter the effect of walls, floors, doors, ceilings and other obstacles on radio wave propagation will be seen. Finally, chapter seven concludes this thesis work and gives some directions for future work

Improved decoder metrics for DS-CDMA in practical 3G systems

While 4G mobile networks have been deployed since 2008. In several of the more developed markets, 3G mobile networks are still growing with 3G having the largest market -in terms of number of users- by 2019. 3G networks are based on Direct- Sequence Code-Division Multiple-Access (DS-CDMA). DS-CDMA suffers mainly from the Multiple Access Interference (MAI) and fading. Multi-User Detectors (MUDs) and Error Correcting Codes (ECCs) are the primary means to combat MAI and fading. MUDs, however, suffer from high complexity, including most of sub-optimal algorithms. Hence, most commercial implementations still use conventional single-user matched filter detectors. This thesis proposes improved channel decoder metrics for enhancing uplink performance in 3G systems. The basic idea is to model the MAI as conditionally Gaussian, instead of Gaussian, conditioned on the users’ cross-correlations and/or the channel fading coefficients. The conditioning implies a time-dependent variance that provides enhanced reliability estimates at the decoder inputs. We derive improved log-likelihood ratios (ILLRs) for bit- and chip- asynchronous multipath fading channels. We show that while utilizing knowledge of all users’ code sequences for the ILLR metric is very complicated in chip-asynchronous reception, a simplified expression relying on truncated group delay results in negligible performance loss. We also derive an expression for the error probability using the standard Gaussian approximation for asynchronous channels for the widely used raised cosine pule shaping. Our study framework considers practical 3G systems, with finite interleaving, correlated multipath fading channel models, practical pulse shaping, and system parameters obtained from CDMA2000 standard. Our results show that for the fully practical cellular uplink channel, the performance advantage due to ILLRs is significant and approaches 3 dB

WCDMA Mobility Troubleshooting Studies and Enhancements

Mobiliteetti on yksi WCDMA-teknologian menestyksen avaintekijöistä. Saumattoman liikkuvuuden ylläpitämiseksi radioresurssien hallinnan algoritmit ovat tärkeässä roolissa verkon hallinnassa. Yhdessä pääsyvalvonnan, kuormavalvonnan, pakettiskedulerin, resurssimanagerin ja tehovalvonnan kanssa kanavanvaihtoalgoritmit vastaavat laadukkaan, katkeamattoman yhteyden ylläpidosta. Nämä algoritmit on toteutettu radioverkko-ohjaimen (RNC) ohjelmistossa. Ohjelmiston elinkaaren aikana ohjelmiston eri osissa kohdataan erilaisia haasteita. Ohjelmiston lisäksi ongelmia voi löytyä myös radioverkon suunnittelusta, verkkolaitteistosta tai päätelaitteista. Kaikkien näiden ongelmien analysointiin vaaditaan kokeneita R&D-insinöörejä, eikä ongelmien varsinaisen aiheuttajan löytäminen usein ole yksinkertaista. Tämän takia erilaiset vianetsintätyökalut ovat ohjelmistokehityksessä ensisijaisen tärkeitä. Tämä diplomityö analysoi jo käytössä olevia vianetsintämenetelmiä NSN-WCDMA-Control Plane-Handover Algorithm -ryhmässä sekä esittää erilaisia paranneltuja ratkaisuja näihin menetelmiin. Tämän diplomityön tuloksena muutamia paranneltuja ratkaisuja toteutettiin ja muutamia muita ratkaisumalleja analysoitiin. Vianetsintätyökalujen sekä -menetelmien kehitys jatkuu tarkastellussa ohjelmistokehitysryhmässä myös tämän diplomityön valmistumisen jälkeen.Mobility is the key success area in WCDMA technology. To maintain seamless mobility, Radio Resource Management algorithms are essential in network management. Together with Admission Control, Load Control, Packet Scheduler, Resource Manager and Power Control algorithms, Handover Control algorithms are responsible for high quality seamless communication. These algorithms take place in the Radio Network Controller software. In software life-cycle there can be challenges related with different software program blocks. Other than software problems there can also be radio network planning problems, hardware problems and user-equipment related problems. Those issues have to be analyzed by experienced R&D engineers. Usually it is not straightforward to investigate what is the root cause. Because of this reason troubleshooting tools play a vital role in software development. This thesis analyzes the existing troubleshooting solutions in NSN-WCDMA-Control Plane-Handover Algorithm team and proposes enhanced solutions for those needs. As a result of this thesis, some of the enhanced solutions are implemented and analyses for the other solutions are provided. Development of troubleshooting tools and methodology will continue in the software development team after the completion of this thesis

Laajakaistaisen CDMA solukkoverkon kapasiteetti makrosoluympäristössä

Tämän diplomityön tarkoitus on tutkia kuormitetun laajakaistaiseen koodijakomenetelmään perustuvan makrosoluverkon kapasiteettia. Työn tavoitteena on selvittää simulointien avulla, miten solukkoverkon palvelemien matkaviestinten käyttäjien eri tiedonsiirtonopeudet ja liikkumisnopeudet vaikuttavat järjestelmän kokonaiskapasiteettiin. Tehonsäädön ja samalla taajuudella olevien solujen välisen kanavananvaihdon toiminnallisuuksien ja parametrien vaikutuksia tutkitaan verkon kapasiteetin kannalta Tutkimus alkaa hajaspektriteknologian perusteiden ja UMTS:n (Universal Mobile Telecommunications System) FDD (Frequency Division Duplex) osan esittelyillä. Laajakaistaisen koodijakoon perustuvan verkon kapasiteetin ominaisuudet esitellään. Makrosoluympäristö määritellään ja sen perusominaisuudet esitellään. Laajakaistaista koodijakoon perustuvaa UMTS-järjestelmää mallintava simulointiohjelmisto kuvaillaan ennen tämän diplomityön simulointien ja tulosten esittelyä ja analysointia. Tämän tutkimuksen simuloinnit suoritetaan yksinkertaisessa esikaupunkityyppisessä makrosoluympäristössä. Laajakaistaisen koodijakoon perustuvan järjestelmän kapasiteetti käyttäytyy hyvin dynaamisesti. Kapasiteetti riippuu käyttäjien jakaumasta verkossa, tiedonsiirtonopeuksista, liikkumisnopeudesta, häiriön määrästä ja tehonsäädön ja samalla taajuudella olevien solujen kanavanvaihdon parametrien valinnasta. Puhekäyttäjien lisäys vaikuttaa enemmän suuria tiedonsiirtonopeuksia kuin alhaisia tiedonsiirtonopeuksia käyttävien tilaajien palvelun laatuun. Solujen väliset häiriöt vaikuttavat merkittävästi verkon kapasiteettiin. Alhaiset tehonsäädön virheet eivät vaikuta merkittävästi hitaasti liikkuvien käyttäjien saamaan palvelun laatuun. Samalla taajuudella olevien solujen kanavanvaihdon kynnysarvo tulisi optimoida, jotta voitaisiin saavuttaa verkon suurin mahdollinen kapasiteetti ja minimoida häiriöt

Cell search in frequency division : duplex WCDMA networks.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2006.Wireless radio access technologies have been progressively evolving to meet the high data rate demands of consumers. The deployment and success of voice-based second generation networks were enabled through the use of the Global System for Mobile Communications (GSM) and the Interim Standard Code Division Multiple Access (lS-95 CDMA) networks. The rise of the high data rate third generation communication systems is realised by two potential wireless radio access networks, the Wideband Code Division Multiple Access (WCDMA) and the CDMA2000. These networks are based on the use of various types of codes to initiate, sustain and terminate the communication links. Moreover, different codes are used to separate the transmitting base stations. This dissertation focuses on base station identification aspects of the Frequency Division Duplex (FDD) WCDMA networks. Notwithstanding the ease of deployment of these networks, their asynchronous nature presents serious challenges to the designer of the receiver. One of the challenges is the identification of the base station identity by the receiver, a process called Cell Search. The receiver algorithms must therefore be robust to the hostile radio channel conditions, Doppler frequency shifts and the detrimental effects of carrier frequency offsets. The dissertation begins by discussing the structure and the generation of WCDMA base station data along with an examination of the effects of the carrier frequency offset. The various cell searching algorithms proposed in the literature are then discussed and a new algorithm that exploits the correlation length structure is proposed and the simulation results are presented. Another design challenge presented by WCDMA networks is the estimation of carrier frequency offset at the receiver. Carrier frequency offsets arise due to crystal oscillator inaccuracies at the receiver and their effect is realised when the voltage controlled oscillator at the receiver is not oscillating at the same carrier frequency as that of the transmitter. This leads to a decrease in the receiver acquisition performance. The carrier frequency offset has to be estimated and corrected before the decoding process can commence. There are different approaches in the literature to estimate and correct these offsets. The final part of the dissertation investigates the FFT based carrier frequency estimation techniques and presents a new method that reduces the estimation error

Advanced receivers for high data rate mobile communications

Improving the spectral efficiency is a key issue in the future wireless communication systems since the spectrum is a scarce resource. Both the number of users as well the demanded data rates are increasing all the time. Furthermore, in mobile communications the wireless link is required to be reliable even when the mobile is in a fast moving vehicle. Using Multiple-Input Multiple-Output (MIMO) antennas is a well known technique to provide higher spectral efficiency as well as better link reliability. Additionally, higher order modulation methods can be used to provide higher data rates. In order to benefit from these enhancements in practise, sophisticated signal processing methods as well as accurate estimates of time-varying wireless channel parameters are needed. This thesis addresses the problem of designing multi-antenna receivers in high data rate systems. The case of multiple transmit antennas is also considered. System specific features of High Speed Downlink Packet Access (HSDPA) which is part of 3rd generation (3G) Wideband Code Division Multiple Access (WCDMA) evolution are exploited in channel estimation methods and in MIMO receiver design. Additionally, complexity reduction methods for Minimum Mean Square Error (MMSE) equalization are addressed. Blind channel estimation methods are spectrally efficient, since no extra resources are needed for pilot signals. However, in mobile communications accurate estimates are needed also in fast fading channels. Consequently, semi-blind channel estimation methods where the receiver combines blind and pilot based channel estimation are an appealing alternative. In this thesis blind and semi-blind channel estimation methods based on knowledge of multiple spreading codes are derived. A novel semi-blind combining scheme for code multiplexed pilot signal and blind estimation is proposed. Another important factor in receiver design criteria is the structure of interference in the received signals. Interference mitigation techniques in MIMO systems have been shown to be potential methods for providing improved performance. A chip level inter-antenna interference cancellation method has been developed in this thesis for HSDPA. Furthermore, this multi-stage ordered interference canceler is combined with the semi-blind channel estimation scheme to enhance the system performance further.Langattomassa tiedonsiirrossa radiospektrin tehokas käyttö on tulevaisuuden suuria haasteita. Taajuuksia on käytössä vain rajoitetusti, kun taas käyttäjien määrä sekä vaaditut siirtonopeudet kasvavat jatkuvasti. Lisäksi langattomien yhteyksien on toimittava luotettavasti myös nopeasti liikkuvissa kulkuneuvoissa. Moniantennijärjestelmät, joissa on useita antenneita sekä tukiasemissa että päätelaitteissa mahdollistavat radiospektrin tehokkaamman käytön sekä parantavat yhteyksien laatua. Tiedonsiirtonopeutta voidaan myös kasvattaa erilaisilla modulaatiotekniikoilla. Hyötyjen saavutamiseksi käytännössä tarvitaan sekä kehittyneitä vastaanotinrakenteita että tarkkoja estimaatteja aikamuuttuvasta radiokanavasta. Tässä työssä on kehitetty vastaanotinrakenteita ja kanavan estimointimenetelmiä kolmannen sukupolven (3G) nopeiden datayhteyksien (HSPA) järjestelmissä. Työssä on johdettu menetelmiä, jotka hyödyntävät HSPA järjestelmien erikoispiirteitä tehokkaasti. Lisäksi on kehitetty laskennallisesti tehokkaita menetelmiä vastaanottimien signaalinkäsittelyyn. Ns. sokeat menetelmät mahdollistavat taajuuskaistan tehokkaan käytön, koska ne eivät vaadi tunnettuja harjoitussignaaleja. Mobiileissa tietolikennejärjestelmissä radiokanava saattaa kuitenkin muuttua hyvin nopeasti, jonka vuoksi kanavan estimoinnissa on tyypillisesti hyödynnetty tunnettua pilottisignaalia. Yhdistämällä pilottipohjainen ja sokea kanavaestimointimenetelmä, voidaan saavuttaa molempien menetelmien edut. Tässä työssä kehitettiin sokeita kanavaestimointimenetelmiä, jotka hyödyntävät useita tunnettuja hajoituskoodeja. Sokean ja koodijakoiseen pilottisignaaliin pohjautuvien kanavan estimaattien yhdistämiseksi kehitettiin uusi menetelmä. Signaalin laatua ja siten vastaanottimen suorituskykyä voidaan langattomissa järjestelmissä parantaa vaimentamalla interferenssiä eli häiriöitä. Vastaanottimen toimintaa voidaan tehostaa oleellisesti, jos häiriösignaalin rakenne tunnetaan. Käytettäessä useampaa lähetysantennia HSPA järjestelmissä vastaanotetussa signaalissa olevia häiriötä voidaan kumota usealla eri tasolla. Tässä työssä on kehitetty chippitasolla häiriöitä kumoava vastaanotinrakenne, joka hyödyntää HSPA järjestelmän ominaisuuksia. Vastaanottimen suorituskykyä on edelleen parannettu yhdistämällä se aiemmin esitettyyn puolisokeaan kanavan estimointimenetelmään.reviewe