  We propose two novel schemes to level up the sum--rate for a two-tier network
with femtocell where the backhaul uplink and downlink connecting the Base
Stations have limited capacity. The backhaul links are exploited to transport
the information in order to improve the decoding of the macrocell and femtocell
messages. In the first scheme, Quantize-and-Forward, the Femto Base Station
(FBS) quantizes what it receives and forwards it to the Macro Base Station
(MBS). Two quantization methods are considered: Elementary Quantization and
Wyner-Ziv Quantization. In the second scheme, called Decode-and-Forward with
Quantized Side Information (DFQSI) to be distinguished with the considered
conventional Decode-and-Forward (DF) scheme. The DFQSI scheme exploits the
backhaul downlink to quantize and send the information about the message in the
macrocell to the FBS to help it better decode the message, cancel it and decode
the message in the femtocell. The results show that there are interesting
scenarios in which the proposed techniques offer considerable gains in terms of
maximal sum rate and max minimal rate.
