Page 127 - From GMS to LTE

Universal Mobile Telecommunications System (UMTS) and High-Speed Packet Access (HSPA) 113

discuss all of them in this book the following sections give a quick introduction to the
most important UMTS features of each release. These are then discussed in more detail
in the remainder of this chapter. For a complete overview of all features of each release
refer to [1].

3.1.1 3GPP Release 99: The First UMTS Access Network Implementation
Initially, 3GPP specification releases were named after the year of ratification, while
later on a version number was used. This is why the first combined 3GPP GSM/UMTS
release was called Release 99, while subsequent versions were called Release 4, Release
5, Release 6 and so on. At the time of publication, 3GPP is in the process of working on
Release 15, which combines GSM, UMTS, LTE and 5G.
Release 99 contains all the specifications for the first release of UMTS. The main
improvement of UMTS compared to GSM in this first step was the completely rede-
signed radio access network, which the UMTS standards refer to as the UMTS
Terrestrial Radio Access Network (UTRAN). Instead of using the time‐ and frequency‐
multiplexing methods of the GSM air interface, a new method called Wideband Code
Division Multiple Access (WCDMA) was introduced. In WCDMA, users are no longer
separated from each other by timeslots and frequencies but are assigned a unique code.
Furthermore, the bandwidth of a single carrier was significantly increased compared to
GSM, enabling a much faster data transfer than was previously possible. This allowed a
Release 99 UTRAN to send data with a speed of up to 384 kbit/s per user in the down-
link direction and also up to 384 kbit/s in the uplink direction. In the first few years,
however, uplink speeds were limited to 64–128 kbit/s.
For the overall design of the UTRAN, the concept of base stations and controllers was
adopted from GSM. While these network elements are called base transceiver station
(BTS) and base station controller (BSC) in the GSM network, the corresponding
UTRAN network elements are called Node‐B and Radio Network Controller (RNC).
Furthermore, the mobile station (MS) also received a new name and is now referred to
as the User Equipment (UE). In this chapter, the UE is commonly referred to as the
mobile device.
In Europe and Asia, 12 blocks of 5 MHz each have been assigned to UMTS for the
uplink direction in the frequency range between 1920 and 1980 MHz. This frequency
range is just above the range used by DECT cordless phones in Europe. For the down-
link direction, that is, from the network to the user, another 12 blocks of 5 MHz each
have been assigned in the frequency range between 2110 and 2170 MHz.
In North America, no dedicated frequency blocks were initially assigned for third‐
generation networks. Instead, UMTS networks shared the frequency band between
1850 and 1910 MHz in the uplink direction and between 1930 and 1990 MHz in the
downlink direction with 2G networks such as GSM and CDMA. Later, additional spec-
trum was assigned for 3G in the range of 1710–1755 MHz in the uplink direction and
2110–2155 MHz in the downlink direction. While the downlink of this frequency allo-
cation overlaps with the downlink in Europe and Asia, a completely different frequency
range is used for the uplink.
Despite being in use for many years the technology for the GSM circuit‐switched core
network was chosen as the basis for voice and video calls in UMTS. It was decided not
to specify major changes in this area but to rather concentrate on the access network.