Critical analysis of multi-antenna systems in the LTE downlink

Long Term Evolution (LTE) is an emerging 4G wireless access technology. It is showing a lot of promise in field trials and gaining acceptance among the major wireless vendors such as Verizon-Vodafone, NTT-Docomo, KDDI, China Mobile, T-Mobile and others. Multi-Antenna or Multiple-Input Multiple-Output (MIMO) systems which involve the use of more than one antenna at the transmitter and receiver are a primary enabler of the high spectral efficiency and data rate sought to be achieved by LTE. This paper is novel in the following 2 aspects: (A) It provides deep physical interpretations into the function and performance of MIMO in LTE. Such insights would not have been published elsewhere in the literature (B) Performance evaluation of MIMO obtained from simulation results based on a full fidelity implementation of the latest version of the LTE Radio Interface standards (3GPP TS 36.211 and 36.213). MIMO performance is explained for various ITU channel models (Pedestrian A, Vehicular A, Typical Urban), Doppler spreads (5, 70, 300 Hz) and antenna correlation conditions (High, Low). The treatment is fully complaint with the specifications laid down in the LTE performance standards 3GPP TS 36.101 and 36.104. The simulated MIMO performance is compared against a twofold system: Theoretical expectations that are derived in this paper and LTE 3GPP performance benchmarks. The author has also compared simulated results with data provided by the LTE-SAE Trial Initiative (LSTI) an industry partnership of telecom vendors and operators. The data show a close match. Due to its proprietary nature, such data is not shown in this paper. Readers with access to LSTI data are encouraged to compare them with results provided in this paper.