tx architecture for a LTE handset
the LTE will use several (up to 8) antennas with either a 2×2 or 4×4 implementation (2/4 transmit and 2/4 receive). Furthermore, these antennas will most likely use spatial multiplexing where each antenna will transmit at a different data stream to maximize upload and download datarates. The uplink modulation used for LTE is Single-carrier Frequency-division Multiple Access (SC-FDMA) whereas the downlink modulation is Orthogonal FDMA. The advantage for the SC-FDMA is that it reduces overall power consumption of the PA’s by lowering the peak average power ratios that is usually seen in OFDM. Therefore, the LTE handset should only use a single PA, unless there is an additional design reason for a second one.
In terms of the transmission itself, the MAC layer (layer 1) will use the Hybrid Automatic Repeat Query (HARQ) to ensure the delivery system between the peer entities. The RLC (layer 2) uses the Automatic Repeat Query (ARQ) to retransmit the IP packets for any error corrections in the upload or download path.