System Level Performance Analysis of Advanced Antenna ... - Centers

Introduction
term user equipment (UE) refers to the terminal. In the sequel, the UMTS terminology
presented here will be used.
The Radio Network Controller (RNC) owns and controls the radio resources in its
domain (the set of Node-Bs connected to it), and it takes care of the following RRM
algorithms: uplink (UL) outer loop power control (OLPC), handover control (HC), packet
scheduling (PS), admission control (AC), load control (LC) and resource manager (RM).
When a UE is connected to the UMTS network (i.e., when it is not in idle mode [1]), its
identity is known by its serving RNC 1 . Moreover, the RNC interacts with the core network
and also terminates the Radio Resource Control (RRC) protocol that defines the messages and
procedures between the UE and the UMTS network. In fact, most of the control signalling
between the UE and the network is based on RRC messages, which carry all parameters to set
up, modify and release connections. For example, all the measurements reports and
commands related to UE mobility across the network are conveyed by means of RRC
signalling. For more details, see some practical examples of the use of RRC messages in
Section 4.3.4.
The Node-B converts the data flow between the Iub and the Uu interfaces [1], and it is
responsible for fast UL closed loop power control (CLPC) and fast LC. Furthermore, the UE
is responsible for fast downlink (DL) CLPC and DL OLPC. As shown in Figure 1.1, a UE can
be connected to several Node-Bs via soft handover (SHO), no matter which RNC each
Node-B is connected to. Furthermore, RRM algorithms can be classified into cell specific and
connection specific. The connection specific RRM algorithms are: UL/DL OLPC, UL/DL
CLPC and HC. The rest of them are cell specific.
UE
Radio Network
Controller (RNC)
Node-B
Uu
Iub
Iu
Core network
Iur
Figure 1.1: UMTS system architecture.
• UL outer loop power control
Handover control
Admission control
Packet scheduling
Load control
Resource manager
UL closed loop power
control
Fast load control
DL closed loop power
control
DL outer loop power
control
1
For simplicity, the possibility of having a UE connected to several RNCs is not considered in this preliminary
discussion. Thus, further clarification of concepts such as serving and drift RNC is not required. For further
information in this respect, see [1].
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