DL - 4G Americas

To enhance the measurement accuracy of the CSI-RS in the case of severe intercell interference that is
expected in heterogeneous deployment, the CSI-RS are time frequency division multiplexed with cellspecific
time/frequency shift within a cell cluster and the CSI RS are randomized among multiple cell
clusters.
Resource specific CQI measurement and report is needed to support the time frequency domain
interference variations expected in a heterogeneous deployment. In particular, the Radio link
management, Radio Resource management and channel state information measurements for LTE Rel-10
UEs are restricted to certain resources. RRC signaling is used to inform the UE across which resources
interference can be averaged for the measurement reports.
7.1.6 MBMS ENHANCEMENTS
For LTE Rel-10, two enhancements were made in the support of MBMS: MBMS counting and MBMS
Allocation and Retention Priority (ARP). For MBMS counting, 3GPP has agreed to use a new RRC
meassage. MBMS counting in LTE is used to determine if there are sufficient UEs interested in receiving
a service to enable the operator to decide if it is appropriate to deliver the service via MBSFN. It allows
the operator to choose between enabling or disabling MBSFN transmission for the service.
The MBMS ARP uses the Multi-cell/multicast coordination entity to pre-empt radio resources for other
radio radio bearer(s) of ongoing MBMS service(s).
MBMS local validity is targeted to be completed in Rel-11.
7.1.7 SON ENHANCEMENTS
SON technologies have been introduced in Rel-8/Rel-9 to help decrease the CAPEX and OPEX of the
system. The initial SON features in Rel-8 and Rel-9 assist operators in deploying LTE networks with
clusters of eNBs in existing 2G, 3G legacy networks to meet the initial coverage requirements. As LTE
networks expand towards more ubiquitous coverage, operator focus will shift towards network growth and
optimizing the capacity and coverage in a heterogeneous environment with Macros, Micros, Picos and
Femtos, with 2G and 3G RATs, and with multiple carriers per RAT. Features are being standardized in
3GPP Rel-10 that offer additional opportunities to further optimize the performance of heterogeneous
networks and further reduce OPEX. The following enhancements to existing SON features and new SON
features are being considered in Rel-10 SON.
Mobility Load Balancing. Enhancements to the Rel-9 inter-RAT load balancing signaling mechanisms
support load balancing between 2G, 3G and 4G networks to better utilize the air interface capacities of
the pooled RF carriers. The specific goals of these enhancements is to improve the reliability of mobility
load balancing in intra-LTE scenarios and improve the functionality of the mobility load balancing in inter-
RAT scenarios.
Mobility Robustness Optimization. Rel-10 defines enhancements to detect connection failures and
provide information needed for possible corrective actions also in cases that were not supported in Rel-9,
like the case of unsuccessful handover. Also, part of the MRO enhancement is enabling the detection of
unnecessary inter-RAT handovers and reporting that event back to the source eNB.
Inter-cell Interference Coordination. Rel-8 ICIC is the coordinated frequency resource allocation
between neighboring cells to reduce interference. Coordination of interference through fractional
frequency reuse can enhance cell edge rates. Self-configuration and self-optimization of control
www.4gamericas.org February 2011 Page 61