Dynamic Capacity Enhancement using a Smart Antenna in Mobile Telecommunications Networks

This work describes an investigation into the performance of antennas for mobile base station applications and techniques for improving the coverage and capacity within a base station cell. The work starts by tracing the development of mobile systems, both in technical and commercial terms, from the earliest analogue systems to present day broadband systems and includes anticipated future developments. This is followed by an outline of how smart antenna systems can be utilised to improve cell coverage and capacity. A novel smart antenna system incorporating an array of slant ± 450 dual- polarised stacked patch elements four columns wide excited by a novel multi-beam forming and beam shaping network has been designed, simulated and implemented. It is found that for an ideal smart antenna array, four narrow overlapping beams, one wide “broadcast channel” beam and right and left shaped beams can be provided. Results are presented for the simulation of the smart antenna system using CST EM simulation software which inherently includes mutual coupling and the effects of a truncated ground plane on the element patterns. The results show some significant changes to the desired set of coverage patterns and various mutual coupling compensation techniques have been reviewed. An improved design technique has been developed for compensating the performance degrading effects of mutual coupling and finite ground plane dimensions in microstrip antenna arrays. The improved technique utilises combination of two previously known techniques: complex excitation weights compensation by inversion of the array mutual coupling scattering matrix and the incorporation of a WAIM (wide angle impedance matching) sheet. The technique has been applied to a novel multi-beam smart antenna array to demonstrate the efficacy of the technique by electromagnetic simulation. In addition, a demonstrator array has been constructed and tested which has yielded a positive conformation of the simulation results. For the developed demonstrator array which provides seven different beams, beams “footprints” have been predicted both for free space propagation and for urban propagation to evaluate the dynamic capacity performance of the smart antenna in a 3G mobile network. The results indicate that sector capacity can be dynamically tailored to user demand profiles by selection of the appropriate beam patterns provided by the novel smart antenna system

Control of The Over-The-Air measurements system

Abstract. Mobile technology is constantly on the move, and it is constantly under development as more efficient and sophisticated telecommunication solutions are needed. As the technology evolves the measurement systems needs to evolve as well. The mobile technology is on the brink of upheaval as we are moving from 4th Generation of wireless communication systems (4G) to 5th Generation of wireless communication systems (5G). The new mobile technology 5G brings new higher frequency bands and new technologies such as massive multiple-input multiple-output and beamforming (BF). In 5G, over-the-air (OTA) measurements are more important because it is virtually impossible to obtain reliable measurement results of BF performance. As the number of antenna elements increases and the antenna spacing decreases, it is very difficult to connect each antenna element to the measuring device with a cable. In this thesis we made tool to control a whole OTA measurement system. The tool is Python code that is run from the Windows desktop with access to the OTA measurement system. The Python code controls which antennas are taken into measurement, connects those to spectrum analyser, configures spectrum analyser and vector signal analyser and measures the power level for the desired beam set. Once the measurement results are collected, it draws a heatmap that visualizes the performance of the BF. The measurements were done by using different number of transmitted beams on the same radio unit. Each configuration was measured multiple times to ensure the stability and reliability of the system. The number of transmitted beams in measurement were 2, 4 and 6. From the plotted heatmaps it was concluded that in all measurements all synchronization signal block (SSB) beams were visible and the directions of the SSB beams were as expected. However, in all measurements the power of SSB beam 1 was slightly lower than the other SSB beams which refers to minor issue in beamforming. As expected, when the number of transmitted beams were 2, the half-power bandwidth (HPBW) was wider and the directivity lower than with 4 or 6 transmitted beams. In measurement results with 2 beams, we had unexpected power drop in the location of antenna 2 in the second SSB beam. With 4 or 6 transmitted beams we measured approximately same HPBW and directivity. The radiation patterns were also as expected. The performance with 6 beams were better in terms of coverage. With 6 transmitted beams we observed more closely mapped beams which ensures that the user equipment can seamlessly move from beam to another without drop in the signal-to-noise ratio. With 6 beams we also observed slightly wider sector coverage than with 4 transmitted beams. Ilmarajapinta mittausten ohjaus. Tiivistelmä. Mobiiliteknologia on jatkuvasti liikkeellä ja sitä kehitetään jatkuvasti, kun tarvitaan entistä tehokkaampia ja kehittyneempiä tietoliikenneratkaisuja. Tekniikan kehittyessä myös mittausjärjestelmiä on kehitettävä. Mobiiliteknologia on mullistuksen partaalla, kun olemme siirtymässä 4. sukupolven langattomista viestintäjärjestelmistä (4G) 5. sukupolven langattomiin viestintäjärjestelmiin (5G). Uusi mobiiliteknologia 5G tuo uusia korkeampia taajuuskaistoja ja uusia teknologioita, kuten massiivinen moniantennitekniikka ja keilanmuodostus (BF). 5G:ssä ilmarajapinta (OTA) -mittaukset ovat tärkeämpiä, koska pelkästään kaapeleilla on käytännössä mahdotonta saada luotettavia mittaus tuloksia BF-suorituskyvystä. Kun antennielementtien määrä kasvaa ja niiden väliset etäisyydet pienenevät, on hyvin vaikeaa liittää jokainen antennielementti mittauslaitteeseen. Tässä opinnäytetyössä teimme työkalun koko OTA-mittausjärjestelmän ohjaamiseen. Työkalu on Python-koodi, joka ajetaan Windowsin työpöydältä, jolla on pääsy OTA-mittausjärjestelmään. Python-koodilla ohjataan mitkä antennit otetaan mittaukseen, kytkee ne spektrianalysaattoriin, konfiguroi spektrianalysaattorin ja vektorisignaalianalysaattorin sekä mittaa tehotason halutulle keilaryhmälle. Kun mittaustulokset on kerätty, se piirtää lämpökartan, joka visualisoi BF:n suorituskyvyn. Mittaukset tehtiin lähettämällä eri määrä keiloja eri mittauksessa samalla radioyksiköllä. Jokainen säteilykuvio mitattiin useita kertoja järjestelmän vakauden ja luotettavuuden varmistamiseksi. Lähetettyjen keilojen lukumäärät olivat kaksi, neljä ja kuusi. Piirretyistä lämpökartoista pääteltiin, että kaikissa mittauksissa kaikki synkronointisignaalilohkon (SSB) keilat olivat näkyvissä ja SSB-keilojen suunnat olivat kuten odotettu. Kuitenkin kaikissa mittauksissa ensimmäisen SSB-keilan teho oli hieman pienempi kuin muiden SSB-keilojen, mikä viittaa lievään vikaan keilanmuodostuksessa. Kuten odotettiin, kahdella lähetetyllä SSB-keilalla puolen tehon kaistanleveys (HPBW) oli leveämpi ja suuntaavuus pienempi kuin neljällä ja kuudella lähetetyllä SSB-keilalla. Kun lähetettiin vain kaksi SSB-keilaa, havaittiin odottamaton tehon putoaminen toisen antennin kohdalla toisen SSB-keilan mittauksessa. Neljällä ja kuudella lähetetyillä SSB-keiloilla oli suunnilleen sama HPBW ja suuntaavuus. Molempien tapauksien säteilykuvio oli odotusten mukainen. Kuudella lähetetyllä keilalla suorituskyky oli parempi kattavuuden suhteen. Keilat olivat myös mittauksessa tiiviimmin yhdessä, mikä varmistaa, että käyttäjä voi siirtyä saumattomasti keilasta toiseen ilman signaali-kohinasuhteen putoamista. Kuudella lähetetyllä keilalla myös sektoripeitto oli hieman laajempi kuin neljällä lähetetyllä keilalla

Spatio-Temporal processing for Optimum Uplink-Downlink WCDMA Systems

The capacity of a cellular system is limited by two different phenomena, namely multipath fading and multiple access interference (MAl). A Two Dimensional (2-D) receiver combats both of these by processing the signal both in the spatial and temporal domain. An ideal 2-D receiver would perform joint space-time processing, but at the price of high computational complexity. In this research we investigate computationally simpler technique termed as a Beamfom1er-Rake. In a Beamformer-Rake, the output of a beamfom1er is fed into a succeeding temporal processor to take advantage of both the beamformer and Rake receiver. Wireless service providers throughout the world are working to introduce the third generation (3G) and beyond (3G) cellular service that will provide higher data rates and better spectral efficiency. Wideband COMA (WCDMA) has been widely accepted as one of the air interfaces for 3G. A Beamformer-Rake receiver can be an effective solution to provide the receivers enhanced capabilities needed to achieve the required performance of a WCDMA system. We consider three different Pilot Symbol Assisted (PSA) beamforming techniques, Direct Matrix Inversion (DMI), Least-Mean Square (LMS) and Recursive Least Square (RLS) adaptive algorithms. Geometrically Based Single Bounce (GBSB) statistical Circular channel model is considered, which is more suitable for array processing, and conductive to RAKE combining. The performances of the Beam former-Rake receiver are evaluated in this channel model as a function of the number of antenna elements and RAKE fingers, in which are evaluated for the uplink WCDMA system. It is shown that, the Beamformer-Rake receiver outperforms the conventional RAKE receiver and the conventional beamformer by a significant margin. Also, we optimize and develop a mathematical formulation for the output Signal to Interference plus Noise Ratio (SINR) of a Beam former-Rake receiver. In this research, also, we develop, simulate and evaluate the SINR and Signal to Noise Ratio (Et!Nol performances of an adaptive beamforming technique in the WCDMA system for downlink. The performance is then compared with an omnidirectional antenna system. Simulation shows that the best perfom1ance can be achieved when all the mobiles with same Angle-of-Arrival (AOA) and different distance from base station are formed in one beam

Dynamic capacity enhancement using a smart antenna in mobile telecommunications networks

This work describes an investigation into the performance of antennas for mobile base station applications and techniques for improving the coverage and capacity within a base station cell. The work starts by tracing the development of mobile systems, both in technical and commercial terms, from the earliest analogue systems to present day broadband systems and includes anticipated future developments. This is followed by an outline of how smart antenna systems can be utilised to improve cell coverage and capacity. A novel smart antenna system incorporating an array of slant ± 450 dual- polarised stacked patch elements four columns wide excited by a novel multi-beam forming and beam shaping network has been designed, simulated and implemented. It is found that for an ideal smart antenna array, four narrow overlapping beams, one wide “broadcast channel” beam and right and left shaped beams can be provided. Results are presented for the simulation of the smart antenna system using CST EM simulation software which inherently includes mutual coupling and the effects of a truncated ground plane on the element patterns. The results show some significant changes to the desired set of coverage patterns and various mutual coupling compensation techniques have been reviewed. An improved design technique has been developed for compensating the performance degrading effects of mutual coupling and finite ground plane dimensions in microstrip antenna arrays. The improved technique utilises combination of two previously known techniques: complex excitation weights compensation by inversion of the array mutual coupling scattering matrix and the incorporation of a WAIM (wide angle impedance matching) sheet. The technique has been applied to a novel multi-beam smart antenna array to demonstrate the efficacy of the technique by electromagnetic simulation. In addition, a demonstrator array has been constructed and tested which has yielded a positive conformation of the simulation results. For the developed demonstrator array which provides seven different beams, beams “footprints” have been predicted both for free space propagation and for urban propagation to evaluate the dynamic capacity performance of the smart antenna in a 3G mobile network. The results indicate that sector capacity can be dynamically tailored to user demand profiles by selection of the appropriate beam patterns provided by the novel smart antenna system.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

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