Base stations have faithfully evolved as cellular telecommunications networks migrated from second- to third-generation (2G to 3G) technologies. As cellular networks migrate to 3.9G or even fourth-generation (4G) technologies, however, base-transceiver-station (BTS) transmitters must be reinvented. From what was originally a single-carrier, narrowband design for 2G GSM/TDMA networks, they evolved into multi-carrier wideband designs (3/3.5G) and now will have to transition to a software-defined-radio (SDR) architecture. In a five-page application note, Agilent Technologies provides guidance on how multi-standard-radio (MSR) base-station transmitter devices can be tested quickly, accurately, and efficiently.
Titled “Solutions for Testing Multi-Standard Radio Base Stations,” the note explains that next-generation base-station transmitters and receivers will support wider bandwidths. In addition, they will include multiple carriers (MCs) of a single radio format as well as multiple formats in one transmitter path. For example, the MSR base station can simultaneously transmit different radio-access technologies (RATs) from a single unit. While such capabilities will drive down base-station cost and size, they also invite a challenge: the conformance testing of MSR base stations in accordance with the 3GPP Release 9 (TS37 series) standard.
The TS37 document covers the MSR MC combinations of 3GPP frequency-division-duplexing (FDD) and time-division-duplexing (TDD) formats. Transmitter conformance tests have to be performed under MSR MC allocating scenarios. The document defines MSR RF test requirements by specifying measurement of the following when testing MSR MC-active configurations: channel power, error vector magnitude (EVM), frequency error, spurious emissions, and spectrum emission mask (SEM).
To provide a realistic use scenario, base-station manufacturers may also want to test each single-format single carrier. Such testing calls for measurement of the adjacent-channel leakage ratio (ACLR), occupied bandwidth, and time alignment between transmitter branches. The note provides details of how all of this testing can be done in an optimized manner using signal analyzers and vector-signal-analyzer (VSA) software. With the accurate and efficient testing of MSR base-station transmitter devices, the note emphasizes that it is possible to ensure their successful deployment.
Agilent Technologies, Inc., 5301 Stevens Creek Blvd., Santa Clara, CA 95051; (877) 424-4536, www.agilent.com.