The next generation of mobile networks, 5G, introduces a paradigm shift towards a user and application centric technology framework. 5G hopes to bring increased download and upload speeds, decreased latency, and improved bandwidth. However, before 5G is implemented and available to the masses, LTE-Advanced is serving as a stepping stone, and is still vital to the current cellular network.
LTE-Advanced comprises multiple features enhancing the basic LTE technology firstly specified in 3GPP Release 8. LTE including the LTE-Advanced improvements was approved by ITU to comply with IMT-Advanced requirements and thus being a true 4G mobile communication system. The different technology components of LTE-Advanced have different market priorities and require different testing strategies.
Carrier aggregation (CA) is one key enabler of LTE-Advanced to meet the IMT-Advanced requirements in terms of peak data rates. It is a highly demanded feature from a network operator perspective, since it enables the aggregation of different spectrum fragments. However, significant design challenges exist on terminal side. Support of higher bandwidths and aggregation of carriers in different frequency bands increase complexity of transceiver circuits, including component design like wideband power amplifiers, highly efficient switches and tunable antenna elements. Further, the additional functionality provided to PHY/MAC layer and the adaptations to the RRC layer need to be thoroughly tested.
Two steps are required to achieve the spectral efficiency and requested peak data rates for downlink and uplink.
- Enhancing the multi-antenna capabilities in downlink (up to 8×8 Single-User MIMO2) and allowing multi-antenna support in the uplink (up to 4×4 Single-User MIMO).
- Applying carrier aggregation. LTE-Advanced as specified by 3GPP Release 10 (Rel-10), allows the aggregation of up to five component carriers, each with up to 20 MHz of bandwidth to attain a total transmission bandwidth of up to 100 MHz.
LTE-Advanced is a complex and powerful technology enhancement. The variances permitted in carrier aggregation increase mobile device complexity. The major design challenge is at the transceiver front end, which must support multiple band combinations. This requires the use of highly flexible switches, wideband power amplifiers and tunable antenna elements. That places exceptional performance requirements on test and measurement equipment. Without adequate planning during the selection process, test equipment can prove inadequate or quickly become obsolete.
The introduction of intra-band (contiguous, non-contiguous) and inter-band aggregation with two component carriers, for instance, calls for a single instrument that supports all 3GPP frequency bands that LTE can utilize. The tester should also be capable of handling all combinations of inter-band carrier aggregation, including 2×2 MIMO and support of different bandwidths per component carrier (up to 20 MHz each). Other test design challenges are at the PHY layer, signaling and mobility. Testing these functions requires a comprehensive set of test scenarios best provided by a test & measurement company with broad experience in physical-layer testing. Complexity increases additionally, when talking about mobility testing for carrier aggregation including multi-antenna technology, known as MIMO that is 2×2.
Multi-box setups, such as the R&SCMW500 Wideband Radio Communication Tester, are often used to simulate multiple cells of different technologies (such as LTE, 3G/WCDMA or 2G/GSM) for various types of mobility testing, PLMN and cell selection scenarios or neighbor cell measurements.
For more information, read Rohde & Schwarz’s application notes on:
September 18, 2019