Editing UMTS (section)

== Interoperability and global roaming ==
UMTS phones (and data cards) are highly portable{{snd}} they have been designed to roam easily onto other UMTS networks (if the providers have roaming agreements in place). In addition, almost all UMTS phones are UMTS/GSM dual-mode devices, so if a UMTS phone travels outside of UMTS coverage during a call the call may be transparently handed off to available GSM coverage. Roaming charges are usually significantly higher than regular usage charges.

Most UMTS licensees consider ubiquitous, transparent global [[roaming]] an important issue. To enable a high degree of interoperability, UMTS phones usually support several different frequencies in addition to their GSM fallback. Different countries support different UMTS frequency bands{{Snd}}Europe initially used 2100&nbsp;MHz while the most carriers in the USA use 850&nbsp;MHz and 1900&nbsp;MHz. T-Mobile has launched a network in the US operating at 1700&nbsp;MHz (uplink) /2100&nbsp;MHz (downlink), and these bands also have been adopted elsewhere in the US and in Canada and Latin America. A UMTS phone and network must support a common frequency to work together. Because of the frequencies used, early models of UMTS phones designated for the United States will likely not be operable elsewhere and vice versa. There are now 11 different frequency combinations used around the world{{snd}} including frequencies formerly used solely for 2G services.

UMTS phones can use a [[Universal Subscriber Identity Module]], USIM (based on GSM's [[SIM card]]) and also work (including UMTS services) with GSM SIM cards. This is a global standard of identification, and enables a network to identify and authenticate the (U)SIM in the phone. Roaming agreements between networks allow for calls to a customer to be redirected to them while roaming and determine the services (and prices) available to the user. In addition to user subscriber information and authentication information, the (U)SIM provides storage space for phone book contact. Handsets can store their data on their own memory or on the (U)SIM card (which is usually more limited in its phone book contact information). A (U)SIM can be moved to another UMTS or GSM phone, and the phone will take on the user details of the (U)SIM, meaning it is the (U)SIM (not the phone) which determines the phone number of the phone and the billing for calls made from the phone.

Japan was the first country to adopt 3G technologies, and since they had not used GSM previously they had no need to build GSM compatibility into their handsets and their 3G handsets were smaller than those available elsewhere. In 2002, NTT DoCoMo's FOMA 3G network was the first commercial UMTS network{{snd}}using a pre-release specification,<ref>{{citation|author=Hsiao-Hwa Chen|publisher=John Wiley and Sons|year=2007|title=The Next Generation CDMA Technologies|isbn=978-0-470-02294-8|pages=105–106}}</ref> it was initially incompatible with the UMTS standard at the radio level but used standard USIM cards, meaning USIM card based roaming was possible (transferring the USIM card into a UMTS or GSM phone when travelling). Both NTT DoCoMo and SoftBank Mobile (which launched 3G in December 2002) now use standard UMTS.

=== Handsets and modems ===
{{update section|date=August 2015}}
[[Image:Nokia6650 unlocked.jpg|thumb|right|The [[Nokia 6650]], an early (2003) UMTS handset]]

All of the major 2G phone manufacturers (that are still in business) are now manufacturers of 3G phones. The early 3G handsets and modems were specific to the frequencies required in their country, which meant they could only roam to other countries on the same 3G frequency (though they can fall back to the older GSM standard). Canada and USA have a common share of frequencies, as do most European countries. The article UMTS frequency bands is an overview of UMTS network frequencies around the world.

Using a [[cellular router]], PCMCIA or USB card, customers are able to access 3G broadband services, regardless of their choice of computer (such as a [[Tablet computer|tablet PC]] or a [[Personal digital assistant|PDA]]). Some software [[self installing|installs itself]] from the modem, so that in some cases absolutely no knowledge of technology is required to get [[online]] in moments. Using a phone that supports 3G and Bluetooth 2.0, multiple Bluetooth-capable laptops can be connected to the Internet. Some smartphones can also act as a mobile [[WLAN access point]].

There are very few 3G phones or modems available supporting all 3G frequencies (UMTS850/900/1700/1900/2100&nbsp;MHz). In 2010, Nokia released a range of phones with [[Multi-band|Pentaband]] 3G coverage, including the [[Nokia N8|N8]] and [[Nokia E7-00|E7]]. Many other phones are offering more than one band which still enables extensive roaming. For example, Apple's [[iPhone 4]] contains a quadband chipset operating on 850/900/1900/2100&nbsp;MHz, allowing usage in the majority of countries where UMTS-FDD is deployed.