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206 From GSM to LTE-Advanced Pro and 5G

26.267. This way the defined Minimum Set of Data (MSD), i.e. the eCall message, is
transmitted in either 1.3 seconds (fast mode) or 2.6 seconds (robust mode). During
transmission, the voice channel at the destination side is muted.
In practice the data transfer works as follows. When an eCall is automatically estab-
lished, the eCall message shall only be sent after a request has been received from the
emergency center. If the emergency center does not request the data the eCall device
can also send an ‘invitation’ to the emergency center to request the data. In addition, the
message can be repeated if not correctly received.

3.15 UMTS and CDMA2000

While UMTS is the dominant 3G technology in Europe, it shares the market with a
similar system called CDMA2000 in other parts of the world, for example, in North
America. This section compares CDMA2000 and its evolution path to the GSM, GPRS
and UMTS evolution path that has been discussed in Chapters 1 to 3.
IS‐95A, which is also referred to as CDMAOne, was designed, similar to GSM, to be
mostly a voice‐centric mobile network. Like GSM, it offers voice and circuit‐switched
data services of speeds up to 14.4 kbit/s. However, IS‐95A and evolutions of that stand-
ard are not based on GSM and as a consequence both radio and core network infra-
structure and protocols are fundamentally different. In particular, the radio network is
fundamentally different from GSM, as it is not based on FTDMA. IS‐95A was the first
system to use the CDMA approach for the air interface that was later also used in the
UMTS standards, where it is referred to as Wideband Code Division Multiple Access or
WCDMA for short.
IS‐95B is a backward‐compatible evolution of the system, which offers increased user
datarates and packet data transmission of up to 64 kbit/s. Thus, it can be roughly com-
pared to a GSM network that offers GPRS services. Similar to the earlier CDMAOne
version, it uses carriers with a bandwidth of 1.25 MHz, which multiple subscribers share
by code multiplexing.
The next step in the evolution path was CDMA2000 1xRTT (Radio Transmission
Technology), which can roughly be compared to UMTS Release 99. While offering
theoretical datarates of 307 kbit/s in the downlink direction, most deployments limited
the maximum speed to about 150 kbit/s. From the overall system point of view, there
are many similarities between CDMA2000 and UMTS. These include:
the use of CDMA on the air interface;
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the use of QPSK for modulation;
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variable length codes for different datarates;
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soft handover;
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continuous uplink data transmission.
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As both UMTS and CDMA2000 need to be backward compatible with their respec-
tive evolution paths, there are also many differences between them, which include the
following:
UMTS uses a WCDMA carrier with a bandwidth of 5 MHz while CDMA2000 uses a
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multicarrier approach with bandwidths of multiples of 1.25 MHz. This was done to
enable use of CDMA2000 in the already available spectrum for IS‐95, while UMTS