Verify and Visualize Your TD-LTE Beamforming Signals

A common theme in modern wireless communications is the use of multi-antenna techniques , such as beamforming and spatial multiplexing in order to improve the cell capacity and throughput. A common problem encountered by customers today, is the inability to verify and visualize the signal at the RF antenna. This white paper will summarize multi-antenna techniques, before introducing the concept of beamforming, along with its advantages and specific use within the 3GPP TD-LTE wireless communication system. It will discuss multi-antenna beamforming measurement challenges from an eNB base station test perspective. It will also highlight the importance of calibration when it comes to testing the performance of a beamforming transmission system. As part of this TD-LTE beamforming discussion an introduction to the Agilent N7109A Multi-Channel Signal Analyzer is provided, along with the Agilent 89600 VSA software installed with the TD-LTE measurement application. Together this test and measurement solution will enable you to verify and visualize your TD-LTE beamforming signals. 3 A summary of multi-antenna techniques employed by various modern wireless communications systems is shown in Figure 1, which captures the concept of Single-Input Single-Output (SISO), Single-Input Multiple-Output (SIMO), Multiple-Input Single-Output (MISO), and Multiple-Input Multiple-Output (MIMO). SISO being the most basic radio channel access mode sets the baseline for minimum transmission performance and provides no diversity protection against channel fading. SIMO provides additional receive antenna redundancy compared to the SISO baseline, allowing the use of receive diversity techniques such as maximum ratio combining in the receiver. This improves SINR observed at the device receiver, and can help improve robustness under channel fading conditions. MISO provides additional transmit antenna redundancy, allowing the use of transmit diversity techniques such as Alamouti symbol coding, or Space Frequency Block Coding (SFBC) as is the case for LTE. Similar to SIMO this also provides an improvement in the observed SINR at the device receiver, and can again help provide protection against channel fading. In contrast MIMO provides both additional transmit and receive antenna redundancy. This redundancy can be used to improve the SINR at the device receiver using transmit and/ or receive diversity techniques. Alternatively some or all of the potential SINR performance improvement can instead be traded off in order to obtain an improved spectral efficiency, by employing spatial multiplexing transmission techniques. This improved spectral efficiency can be realized either in the form of increased data rate throughput for a single user device using Single-User MIMO …