THIS PAST JUNE, the latest version of Release 8 of the 3rd Generation Partnership Project (3GPP) was unveiled. Many expect Long-Term Evolution (LTE) to be the long-term, high-speed data solution for all 3GPP-based wireless networks, such as GSM and WCDMA. Although LTE can be built on major carriers' existing infrastructure, it differs from current technologies. To help engineers grasp the basic aspects of LTE and how system performance will be measured, Rohde & Schwarz has released a white paper titled, "Understanding Long-Term Evolution Fundamentals and Measurement Challenges."
The 15-page document begins by describing what sets LTE apart from other wireless communications standards. In systems employing multiple-input multiple-output (MIMO), for example, the transmitter and receiver use multiple antennas to increase data throughput. They do not need additional bandwidth or higher transmit power. MIMO systems also achieve higher transmission robustness by increasing the signal-to-noise ratio (SNR) for terminals at the cell edge. In addition, LTE stands out for its use of Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink. OFDMA provides multiple access by assigning subsets of subcarriers to individual users. In doing so, it allows simultaneous multi-user, low-data-rate transmission.
For component or entity testing, LTE demands standard instruments like signal generators and signal and spectrum analyzers. Radio communication testers can verify the RF and protocol stack of a device under test (DUT). They allow specific services of interest to run on the Internet Protocol (IP) layer. Yet the testing of LTE is complex, as MIMO has not previously been deployed as a core technology in both the infrastructure and user equipment of a personal communications system. During the development, manufacturing, installation, and maintenance of LTE infrastructure and user equipment, changes will therefore be made to the test specifications as well as how tests are conducted.
The white paper includes sections on physicallayer, data-path, functional, performance, and production testing. It explains when each type of testing is done and the critical steps to make sure they are done correctly. The note then moves on to specific primary tests and how they can be configured. RF integrated circuits (RFICs) are used as an example. This work emphasizes that ratification of the LTE standard is just the first step in the evolutionary process that will unfold as infrastructure and user equipment are developed. When the first LTE systems are deployed, more will be learned about how they actually compare to the predicted and actual performance of LTE networks.
Rohde & Schwarz, Mhldorfstrae 15, 81671 Mnchen, Germany; +49 89 41 29 0, FAX: +49 89 41 29 12 164, Internet: www.rohde-schwarz.com.
