Page 132 - From GMS to LTE

118 From GSM to LTE-Advanced Pro and 5G

In cities, UMTS cells usually cover an area with a diameter of less than 1 km. This is
due to the higher frequencies used compared to GSM and because of the high population
density in such areas. In some countries, for example Australia, where the population
density is very low in rural areas, UMTS is used by some operators in the 850 MHz
band, which allows for very large coverage areas. However, where the landscape is flat,
the maximum cell range of 60 km is no longer sufficient, so that in Release 7 the 3GPP
standards were extended to allow for cell ranges of up to 180 km.

3.1.6 3GPP Release 8: LTE, Further HSPA Enhancements and Femtocells
In 3GPP Release 8, a number of features were introduced that had a significant impact
on wireless networks. First, Release 8 introduced the successor of the UMTS radio network,
the E‐UTRAN, and the successor architecture of the core network, the EPC. Together
they are commonly known as LTE, although technically this is not quite correct. As LTE
is a revolution in many ways it is discussed separately in Chapter 4.
In the UMTS domain, this release of the standard also contains some notable enhancements
to keep pace with the rising data traffic. To reach even higher data speeds, Release 8
introduces the aggregation of two adjacent UMTS carriers to get a total bandwidth of
10 MHz. This is referred to as Dual‐Cell or Dual‐Carrier operation. Also, the simultaneous
use of 64‐QAM and MIMO has entered the standards for single carrier operation.
Under ideal radio conditions, a peak throughput of 42 Mbit/s in the downlink direction
can be reached.
One small but important functionality specified in 3GPP Release 8 is ‘In Case of
Emergency’ (ICE). Devices that implement this functionality allow the user to store
information on the subscriber identity module (SIM) card that can be accessed in a
standardized way in emergency situations where the user of the phone is unable to
identify himself or to contact their relatives. Unfortunately, the feature has not found
widespread adoption so far.
And finally, 3GPP Release 8 laid the groundwork for Femtocell management, referred
to as Home Node‐Bs in the standard, and Self‐Organizing Network (SON) functionality
to ease deployment and maintenance of base stations.

3.1.7 3GPP Release 9: Digital Dividend and Dual‐Cell Improvements
For UMTS, Release 9 brought a number of further speed enhancements in both
uplink and downlink directions. In the uplink direction, aggregation of two adjacent
5 MHz carriers has been specified in a similar way as in the downlink direction in the
previous release. This in effect again doubles the theoretical peak uplink datarate to
over 20 Mbit/s. In the downlink direction, dual‐carrier operation can now be com-
bined with MIMO operation, increasing the peak throughput to 84 Mbit/s.
Furthermore, a new work item removed the dual‐carrier limitation that the two
carriers had to be adjacent to each other. With this addition, carriers can now be in
different frequency bands.
As has been shown in Chapter 1, pre‐Release 9 GSM and GPRS security mechanisms
have not been changed in quite some time and vulnerabilities have been discovered.
With this release, 3GPP has added an additional ciphering algorithm, A5/4. Together
with doubling of the ciphering key (CK) length to 128 bits, this is considered to be a
major security upgrade.