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to in 3GPP. 117 The simulation scenario considered is Case One: 2X2 MIMO, three Type 1 RNs per cell
and with 25 UEs per cell. The eNB can schedule the RNs on six subframes and schedule UEs on 10
subframes while the RN can schedule UEs on four subframes. The results show that significant gain in
both the cell edge and cell average throughputs are possible with only three relay nodes per cell. Note
that additional gain is possible with additional relay nodes in the system with more antennas at the eNB
and/or the relay and a better backhauling design.
Figure 7.4. The Potential System Gain in LTE-A with Relays 118 .
7.1.5 HETEROGENEOUS NETWORK SUPPORT
The heterogeneous network can be characterized by deployments where low power nodes are placed as
an underlay throughout a macrocell deployment. These low power nodes include micro, pico, Remote
Radio Heads (RRH), relay and femto nodes. The most challenging aspect in the deployment of
heterogeneous networks is the interference issues generated by sharing the carrier with the overlaid
macro nodes.
In LTE Rel-10, two methods have been defined for the support of Heterogeneous network in LTE Rel-10:
carrier aggregation-based and non-carrier aggregation-based. For carrier aggregation based support,
cross-carrier scheduling is used to avoid the interference of PDCCH between macro cell and small cell
(Figure 7.5). In particular, the PDCCH to schedule the multiple component carriers in a macro cell is
located in one component carrier while the PDCCH to schedule the multiple component carriers in the
small cell is located in another component carrier.
117 3GPP TR 36.814, Further Advancements for E-UTRA, Physical layer Aspects.
118 Further information on these results can be found in 3GPP R1-100270.
www.4gamericas.org February 2011 Page 59