Specifically, there is a Qualcomm-based LTE modem (MDM9645M) within the GSM/CDMA A1660 and A1661 models, and a GSM-only Intel-based (XMM7360) LTE modem within the A1778 and A1784 models. In the United States, Verizon Wireless uses the GSM/CDMA Qualcomm chip, while AT&T uses the GSM-only Intel chip. As a result, AT&T’s, and other carrier’s iPhones, that use the Intel chip are not compatible with as many different carriers as the GSM/CDMA chip that Verizon, and some other carriers, offer.
Now, on top of that, testing from Cellular Insights shows that there might be a bit more of a difference between the two LTE modems.
The tests show that, in some areas, the Qualcomm LTE modem outperforms the Intel LTE modem by a significant margin. Cellular Insights put together an in-depth test, utilizing a variety of different components to simulate varying LTE performance at different distances from a cellular tower. That included an R&S TS7124 RS Shielded box, two R&S CMW500, a single R&S CMWC controller, and four separate Vivaldi antennas. The devices in question were both iPhone 7 Plus units, one equipped with the Qualcomm LTE modem, and the other outfitted with Intel’s LTE modem.
“The goal of the test was to measure the highest achievable LTE throughput starting at a Reference Signal Received Quality of -85dBm (a strong signal) and gradually reducing the power level to simulate moving away from a cellular tower where signal is weaker. Three LTE bands were tested: Band 12, Band 4 (the most common band in North America), and Band 7.”
In the process of testing, Cellular Insights discovered that, in optimal conditions, and when dealing with the strongest connection to the cellular tower, both LTE modems performed similarly. However, moving further away from the cellular tower showed “unexplainable sharp dips in performance” in regards to the Intel LTE modem. The gap they discovered was “north of 30%” in performance comparisons between the two modems. As the tests went on, the Qualcomm LTE modem showed higher throughput speeds than the Intel modem as signal strength decreased.
“Both iPhone 7 Plus variants perform similarly in ideal conditions. At -96dBm the Intel variant needed to have Transport Block Size adjusted as BLER well exceeded the 2% threshold. At -105dBm the gap widened to 20%, and at -108dBm to a whopping 75%. As a result of such a huge performance delta between the Intel and Qualcomm powered devices, we purchased another A1784 (AT&T) iPhone 7 Plus, in order to eliminate any possibility of a faulty device. The end result was virtually identical. […]
At -121dBm, the Intel variant performed more in line with its Qualcomm counterpart. Overall, the average performance delta between the two is in the 30% range in favor of the Qualcomm”
The tests all showed the same results: The iPhone 7 Plus outfitted with the Qualcomm LTE modem indicated a “significant performance edge” over the Intel LTE modem.
Yo can read the full results right here.[via Cellular Insights]