Efficient utilization of radio resources within
an access network is performed by the radio resource management
entity. The mobile WiMAX RRM is based on a generic architecture. The RRM
defines mechanisms and procedures to share radio resource related
information between BS and ASN-GW. The RRM procedures allow different BSs
to communicate with each other or with a centralized RRM
entity residing in the same or a different ASN to
exchange information related to measurement and management of radio
resources. Each BS performs radio resource measurement locally based on
a distributed RRM mechanism. It is also possible to deploy RRM in an
ASN using base stations with RRM function, as well as a centralized RRM
entity that does not reside in the BS and collects and updates radio
resource indicators such as choice of target BS, admission or rejection of
service flows, etc., from several BSs. The RRM procedures facilitate
the following WiMAX network functions:
• MS admission control and connection admission control,
i.e., whether the required radio resources are available at a candidate
target BS prior to handover;
• Service flow admission control, i.e., creation or modification
of existing/additional service flows for an existing MS in the network,
selection of values for admitted and active QoS parameter sets
for service flows;
• Load balancing by managing and monitoring system
load and use of counter-measures to enable the system back to normal
loading condition;
• Handover preparation and control for improvement/maintenance
of overall performance indicators (for example, the RRM may assist
in system load balancing by facilitating selection of the most
suitable BS during a handover).
The RRM is composed of two functional entities, i.e.,
radio resource agent (RRA) and radio resource control (RRC). The radio
resource agent is a functional entity that resides in the BS. Each
BS includes a radio resource agent. It maintains a database of
collected radio resource indicators. An RRA entity is responsible for
assisting local radio resource management, as well as communicating
to the RRC to collect and measure radio resource indicators from the
BS and from a plurality of mobile terminals served by the BS using MAC
management procedures as specified by the IEEE 802.16 specifications.
It also communicates RRM control information over the air interface to the
MS, as defined by the IEEE 802.16 specifications. An example of such
RRM control information is a list of neighbor BSs and their parameters. It
further performs signaling with RRC for radio resource management
functions, as well as controlling the radio resources of the serving BS,
based on the local measurements and reports received by the BS
and information received from the RRC functional entity.
The local resource control includes power
control, monitoring the MAC and PHY functions, modifying the contents
of the neighbor advertisement message, assisting the local service flow
management function and policy management for service flow
admission control, making determinations and conducting actions based
on radio resource policy, assisting the local handover functions.
The radio resource control functional entity may reside
in BS, in ASN-GW, or as a standalone server in an ASN, and is responsible
for collection of radio resource indicators from associated RRAs. The
RRC can be collocated with RRA in the BS. The RRC functional entity
may communicate with other RRCs in neighboring BSs which may be in the
same or different ASN. The RRC may also reside in the ASN-GW and
communicate to other RRAs across R6 reference point. When the RRC is
located in the ASN, each RRA is associated with exactly one RRC.
The RRC relay functional entity may reside in ASN-GW for the purpose
of relaying RRM messages. The RRC relay cannot terminate RRM messages, but
only relays them to the final destination RRC. Standard RRM
procedures are required between RRA and RRC, and between RRCs across
network interfaces to ensure interoperability. These procedures
are classified into two types: information reporting procedures for
delivery of BS radio resource indicators from RRA to RRC; and between RRCs
and decision support procedures from RRC to RRA for communicating
recommendations on aggregated RRM status (e.g., in neighboring BSs) for
various purposes.
The RRM primitives can be used either to report radio
resource indicators (i.e., from RRA to RRC or between RRCs) or to
communicate decisions from RRC to RRA. The former type of primitive is
called information reporting primitive and the latter is called
decision support primitive. The available radio resource information
provided by the RRAs to RRC is used by RRC for load balancing. The RRC
may interact with the handover controller to ensure load balance.
