Verizon 4G LTE Phones to Be Incompatible with AT&T’s LTE Network Chuong Nguyen07/15/2011 Here’s yet another reason right now to not be an early adopter of 4G LTE technology despite the fast speeds that the mobile broadband standard is promising: the lack of roaming options. While 3G CDMA and GSM (HSPA) smartphones have been able to roam worldwide thanks to chipsets that support compatibility with various networks on various different spectrums and frequencies, so far 4G LTE will be implemented on a variety of spectrums both in the U.S. and abroad limiting the phone’s ability to roam, at least while the technology is still new. Users who have adopted Verizon’s first batch of 4G Android smartphones should know that the carrier has gone on record to say that it doesn’t anticipate that its 4G phones will be compatible with AT&T’s forthcoming 4G LTE network. The problem right now is that Verizon and AT&T will operate on different spectrums, so phones from one network won’t be able to tap into spectrum from the other network. According to PC Mag, “Verizon and AT&T both run their LTE networks in the 700-MHz band. But Verizon’s network is mostly in 746-787MHz, while AT&T’s will be primarily in 704-746MHz. Some Verizon and AT&T spectrum overlaps in an area called the “lower B block,” but not much.”Advertisement The problem here is that it will at least keep 4G limited to major cities, at least initially while both AT&T and Verizon Wireless are building out their LTE networks as the carriers cannot offer roaming agreements to overlap and augment each other’s network where it doesn’t have coverage. In order to achieve roaming compatibility, manufacturers would have to support both Verizon’s and AT&T’s network on devices. As it stands, 4G chips aren’t yet integrated into the processor and require an external, expensive chipset on the phone so that chances of integration right now at this nascent stage is probably unlikely as it would add to the size of the overall device as well as the cost. Additionally, even if 4G roaming was supported in a hypothetical and ideal situation, phones then would have to support GSM, CDMA, HSPA/WCDMA/UMTS, EV-DO in order for there to be true roaming on AT&T and Verizon. As it stands, Verizon’s phones right now offer simultaneous voice and data through a hybrid radio system where data would be utilized on the faster LTE network while voice would be handled on CDMA. In the future, Verizon had said that it would explore the possibility of doing Voice over LTE (VoLTE) in a mechanism similar to delivering VoIP or using data to transmit voice so that it doesn’t need to have the CDMA radio active alongside the LTE radio. The result of VoLTE is that phones would last longer as both radios won’t have to be fired up concurrently while on a voice and data call.Advertisement And that’s just the situation in the U.S. with the top two national carriers. In addition to Verizon and AT&T, there’s also MetroPCS, which is a regional carrier that utilizes the 1700 MHz frequency. Then, there’s the issue of international carrier and the result of 4G LTE may be as confusing as trying to figure out the right wall plugs and adapters for frequent flyers who travel internationally.Advertisement PC Mag reports that at this time, AT&T doesn’t even know if its devices will be compatible with Verizon’s network. Though the carrier had announced two mobile data devices for LTE, it has yet to announce any phone products. If you thought that 4G was confusing before with LTE, HSPA+, and WiMax, now we can all breathe a sigh of oy vey!