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Snapdragon X24 Doubles Gigabit LTE

February 27, 2018

Author: Linley Gwennap

Even with the debut of 5G in sight, Qualcomm continues to push the limits of 4G. Its next-generation Snapdragon X24 LTE modem supports a peak download speed of 2.0Gbps, nearly double the speed of today’s X20 design. To help operators achieve such high rates, the 7nm chip can aggregate up to seven carriers. The X24 currently sampling, and we expect it to reach production late this year.

Achieving the maximum Category 20 data rate requires 20 streams, each using QAM-256 on a 20MHz channel. By stacking four streams per channel using 4x4 MIMO, the X24 can reach 20 streams using five channels. Several operators already employ unlicensed spectrum to increase their data rates. The X24 supports four unlicensed carriers using LAA, shifting more traffic into unlicensed bands. The unlicensed carriers, however, can achieve only 2x2 MIMO. Given the limited amount of licensed spectrum available, the new modem practically requires LAA to reach its maximum data rate.

Qualcomm also doubled the peak uplink speed to 316Mbps, which requires 3x carrier aggregation and QAM-256; the X20 is limited to 2xCA and QAM-64 on the uplink. As more smartphone users upload photos and video, they appreciate uplink improvements. In addition, the company supplies a companion RF transceiver that enables seven receive carriers and three transmit carriers in a single chip. Qualcomm also provides a new envelope tracker (QET5100) that can optimize power across three 20MHz carriers.

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