Apple has always had had Qualcomm as its modem supplier for nearly five years, it appears that this year apple has taken a different approach with their modem supplier. They selected two instead of one baseband chipset supplier.

Intel is the other option with Qualcomm, and this enabled two unique RF SKUs. Intel's modem would support (A1778, A1784) and is limited to GSM/WCDMA/LTE. On the other hand Qualcomm will support (A1660, A1661) with GSM/WCDMA/CDMA/TDSCDMA/LTE as per Cellular Insights. 

It turned out that due to poor network conditions the iPhone 7 plus does not perform well enough with Intel than the iPhone 7 plus with Qualcomm. Hence, the company that has relied with Qualcomm for several years had to consider a major change.

According to Phonescoop, with finest network conditions both Qualcomm and Intel equipped iphones showed an equal level of performance in maintaining connection and speed. But, with weak network conditions the Intel operational iPhone 7 plus demonstrated a 30 percent slower speed than the Qualcomm equipped iPhone 7 plus.

Due to the slower speed by Intel it is certain to experience dropped VoLTE calls, it seems that the Qualcomm modem's performance with the iPhone 7 plus has been significant.

There are only two possible outcomes with Intel in this cellular business either it will succeed or it will not, based on the performance it seems that the iphone 7 plus is not match for the Qualcomm modem. 

One main reason for dropped calls and timeouts is also the phone's OEM accomplishment; it also highly depends on the RF front end (RFFE) and the design of the antenna. 

Though apple is known to be with Qualcomm it has not revealed the reason behind selecting modems from two different suppliers for the iPhone 7 plus. Despite the major change it does not seem to have affected apple in any aspect.