| Having dealt with in-depth analysis of SS#7, GSM and GPRS networks I started to monitor
UTRAN interfaces approximately four years ago. Monitoring interfaces means decoding
the data captured on the links and analysing how the different data segments and messages
are related to each other. In general I wanted to trace all messages belonging to a single
call to prove if the network elements and protocol entities involved worked fine or if there
had been failures or if any kind of suspicious events had influenced the normal call
proceeding or the call’s quality of service. Cases showing normal network behaviour have
been documented in Kreher and Ruedebusch (UMTS Signaling. John Wiley & Sons, Ltd,
2005), which provides examples for technical experts investigating call flows and network
procedures.
While still writing the last paragraphs of UMTS Signaling it became obvious that the focus
of leading UMTS technology experts was changing more and more from the investigation of
functional behaviour to the analysis of huge data streams supplied by signalling information
and user data/payload. As a result the idea of a second book was already born before the first
one was ready to be published. Some major customer projects I have been involved in
pushed my ideas and knowledge further into this field. Indeed, if one compares radio-related
information in UMTS and GSM radio access network protocols, e.g. the contents of
measurement reports sent to the network by mobile stations and base stations, it is obvious
that in UMTS much more radio-specific measurements are executed. Reports are sent more
frequently and by using more sophisticated methods than in GSM to guarantee the quality of
service in UMTS networks.
The radio technology behind UMTS is seen in two different varieties: frequency duplex
division (FDD, also known as WCDMA), where uplink and downlink data is transmitted on
two different frequency bands; and time division duplex (TDD), where uplink and downlink
channels are separated using timeslots. TDD is actually beyond the scope of this book,
because it has not been introduced in European and North American networks so far. The
Chinese solution of a low chip rate TDD (TD-SCDMA) has not yet been deployed in the
field, and although deployment may start during 2006 it will take a while before performance
measurement becomes crucial for TD-SCDMA operators. First they have to set emphasis on
the execution of functional tests. Nevertheless, many measurement definitions and key
performance indicators presented in this book will also be valid in TDD networks apart from
mostly radio-related measurements and soft handover analysis, because there is no soft
handover in TDD. |
