Indoor Planning in Broadband Cellular Radio Networks

The capacity requirements of cellular networks continue to grow. This has forced cellular operators to seek new ways of improving the availability and transmission rate experienced by users. The majority of cellular network data users are located inside buildings, where coverage is difficult to ensure due to high penetration loss. Indoor users also cause high load to outdoor networks, reducing the quality and availability for outdoor users. This has given rise to a growing need for implementing dedicated indoor systems, and further optimizing their performance to provide high capacity. It was estimated that in 2011 there were 5.37 billion mobile subscriptions in 3GPP-supported GSM, UMTS/HSPA and LTE networks, of which 890.7 million were using UMTS/HSPA. Currently, UMTS is the leading standard for providing mobile broadband, although LTE is becoming increasingly popular. The planning of radio networks is well known and documented. However, the planning and optimization of indoor networks has not been widely studied, although clear improvements in both coverage and capacity can be achieved by optimizing cell- and antenna line configuration. This thesis considers the special characteristics of the indoor environment with regard to radio propagation and radio network planning. The aspects of radio network planning are highlighted especially for WCDMA radio access technology. The target is to provide guidelines for indoor radio network planning and optimization using an outdoor-to-indoor repeater or a dedicated indoor system with various antenna and cell configurations. The studies conducted here are intended to provide better understanding of the indoor functionality and planning of WCDMA radio access, and UMTS cellular system including the latest HSPA updates. The studies show that the indoor performance of a high data rate WCDMA system can be improved by increasing the antenna density in the distributed antenna system, or by utilizing uplink diversity reception. It is also shown how system capacity can be further improved by adding more indoor cells to a single building. The inter-cell interference is analyzed, and the limits for cell densification are discussed. The results show that compared to dedicated indoor systems, similar indoor performance can be provided by extending macrocellular coverage inside buildings using an outdoor-to-indoor repeater. However, good performance of repeater implementation needs careful repeater antenna line and parameter configuration. Nevertheless, capacity is in any case borrowed from an outdoor mother cell. Sharing frequencies between outdoor and indoor systems is often necessary due to high capacity demand and limited available frequency band. A co-channel indoor system was measured to affect both uplink and downlink performance of an outdoor cell. In the uplink, a clear increase in uplink intercell interference was observed. Throughput degradation was also measured in downlink, but the affect is limited to the area close to the indoor system. However, the added high capacity of an indoor network usually justifies performance degradation. The results can help mobile operators design their networks to provide better coverage, higher capacity and better quality for indoor users. After taking into account the implementation costs, the results also help operators to reach a techno-economic trade-off between the various deployment options

Passive Intermodulation in Indoor Radio Networks

Energiankulutuksen vähentäminen ja uusiutuvista lähteistä peräisin olevan energian käyttö rakennusalalla ovat tällä hetkellä tärkeitä toimenpiteitä. Käytännössä tämä näkyy rakentamisessa tiukentuneina energiatehokkuusvaatimuksina. Radiotaajuuksien näkökulmasta katsottuna tämä ilmenee kehittyneinä rakennusmateriaaleina, jotka sisältävät erilaisia metallipinnoitteita – tai kerroksia. Edellä mainittujen seikkojen johdosta, voidaan tehdä päätelmä, että asuinrakennusten kattavaan peittoon ja tulevaisuuden kasvaviin kapasiteettivaatimuksiin pystytään vastaamaan vain rakennusten sisäisillä antenniverkoilla, niin sanotuilla DAS-järjestelmillä (Distributed Antenna System). Tutkimuksen mittaukset koostuivat kolmesta selkeästä osakokonaisuudesta, joista kaikista suoritettiin omat mittaukset: Peittomittaukset, passiivisen keskinäismoduulation mittaukset ja antennin säteilytehon mittaukset. Edellä mainitut kolme osa-aluetta liittyvät vahvasti toisiinsa ja luovat selkeän kokonaisuuden. Peittomittausten tavoitteena oli tarkoitus arvioida sisäverkon antennien erilaisten sijoituspaikkojen vaikutusta asuinkerrostalojen eri huoneistojen signaalitasoihin. Tutkimuksessa kalibroitiin kenttämittausten avulla kaupallinen simulaattori, jonka avulla havaittiin, että Säteilyturvakeskuksen rajoittamalla 33 dBm lähetysteholla saadaan yhden asuinkerroksen kattava peitto. Passiivisen keskinäismodulaation tutkimuksessa oli tarkoituksena mitata todellisen verkon PIM–arvoja käyttämällä sisäverkkojen verkonrakennuksessa tavallisimmin asennettavia komponentteja sekä löytää suosituksia antennien valintaan ja asennustapaan PIM–särön välttämisen näkökulmasta. Tutkimuksessa havaittiin, että käytävän leveys ja antennin lähikentässä oleva metallinen materiaali vaikuttavat merkittävästi PIM-arvon suuruuteen. Tulosten perusteella löydettiin viitteellinen antennin sijoituspaikkaohje, jonka perusteella antenni tulisi kapealla käytävällä (alle 160 cm leveä) sijoittaa 0-20 cm etäisyydelle käytävän välikatosta ja seinästä. Leveällä käytävällä (yli 160 cm leveä) antenni tulisi sijoittaa 15-30 cm etäisyydelle katosta ja 10-30 cm etäisyydelle seinästä. Antennin säteilytehon mittausten tutkimuksen osassa oli tarkoitus arvioida nykypäivänä suunniteltavien DAS-sisäverkkojen yksittäisten antennien todellista säteilytehoa. Tutkimuksen perusteella voidaan sanoa, että antennin hyötysuhde on keskimäärin noin 80 %. Lisäksi antennin sijoittaminen sisätiloihin laskee tätä arvoa, sillä antennin lähikentässä oleva metallinen materiaali vaikuttaa negatiivisesti antennin ominaisuuksiin. Mittaustulosten perusteella saatiin selville, että mittauksissa käytetyillä antenneilla syöttötehon tulisi olla 2,23–2,80 W, mikäli halutaan saavuttaa 2 W säteilyteho

Comparison of Picocell and DAS Configuration with HSPA Evolution

As demand of mobile data services has grown exponentially, it has increased pressure on mobile operators to enhance capacity in dense urban areas. Usage of internet and services related to mobile network has grown up. UMTS specification has been updated in order to cope with an increased amount of mobile data traffic. These upgrades and releases are based on international standards. HSDPA and HSUPA technologies are previous upgrades of UMTS network but now HSPA Evolution (HSPA+) is the upgraded version for UMTS. HSPA+ improves performance of mobile data transmission in downlink direction. Previously UMTS enabled user data of 384 kbps that was upgraded to 14.4 Mbps in downlink and 5.76 Mbps in uplink data rate by HSPA. But still the demand of data rate is increasing so HSPA+ upgraded UMTS to 21.1 Mbps in downlink and 5.76 Mbps in uplink. Due to these improvements in data rates, HSPA+ has become one of the striking choices for mobile operators. It has been forecasted that amount of data users will increase in future and this will set new challenges for mobile operators. The network is planned in such a way that more capacity is provided to places where more users are present. Most of the network traffic in dense urban area is generated by indoor users. Indoor planning is mostly done with multiple picocells or DAS configuration. The main differences between these two configurations are interference, total capacity, cost of the equipment and implementation. In this Master’s thesis, the main focus is to compare picocells and DAS configuration for HSPA+ by simulations and measurements. Several mobile terminals were used to generate low and high loads for HSPA+ network. These comparisons were made by analyzing the results for signal to interference ratio, total network throughput and several other indicators. The results showed that DAS outperforms picocells in low/high load conditions in terms of SIR, cell throughput and modulation technique. DAS is good choice for medium sized building due to handover free regions and smooth coverage. /Kir1

HSDPA measurements for Indoor DAS

The target of the paper is to study performance of HSDPA in indoor environment, and to provide guidelines for HSDPA coverage and capacity planning and antenna configurations selection. Field measurements with a HSDPA data card, field measurement software, and a fully functional HSDPA enabled UMTS network were performed. Indoor corridor environment was used to study the impact of different distributed antenna configurations on a HSDPA performance. In addition, pico cell configuration is compared to corresponding distributed antenna configuration, and the effect of coverage limitations on HSDPA capacity is studied. The results show, that ensuring sufficient coverage is the key factor in planning HSDPA indoor network. Signal quality can be enhanced by increasing the number of antennas in DAS, which is also visible as improved capacity. Better signal level can be achieved by pico base stations, but taking benefit of added capacity is problematic. The measurement results show that distributed antenna configuration provides better performance compared to pico cells. As a conclusion, adequate coverage planning plays an important role in planning indoor networks for HSDPA, and some additional capacity can be gained by antenna configuration optimization.Peer reviewe