## 4 A Hybrid Algorithm for Power Allocation in Macrocell/Femtocell Architecture
This is due to the power allocation method that tries to decrease the power according to the Equations (7) and (11). The PLR is so high when there is no power allocation as interfered users will experience a very bad channel quality, compared to the utility method. Figure 4: Average number of measurement reports sent by macrocell user equipments and femtocell user equipments. Figure 3: Throughput of the video traffic. As for the QoE experienced by the users, the Mean Opinion Score (MOS) was used in relation with the objective metric mainly the PSNR. According to [30; 31], the relationship between PSNR and MOS may be approximated by the bounded logarithmic function:

\[MOS_{x}(PSNR_{x})= \begin{cases}1,&:PSNR_{x}\leq PSNR_{1.0},\\ d\log PSNR_{x}+e,&:PSNR_{1.0}\leq PSNR_{x}\leq PSNR_{4.5},\\ 4.5,&:PSNR_{x}\geq PSNR_{4.5},\end{cases}  \tag{17}\]

with

\[d=\frac{3.5}{\log PSNR_{4.5}-\log PSNR_{1.0}}, \tag{18}\]

\[e=\frac{\log PSNR_{4.5}-4.5\log PSNR_{1.0}}{\log PSNR_{4.5}-\log PSNR_{ 1.0}}.\]

The parameters \(PSNR_{1.0}\) and \(PSNR_{4.5}\) denote the PSNR, which means that the perceived quality drop to \"not acceptable\" (MOS = 1.0) and exceeds \"very satisfied\" (MOS = 4.5), respectively. Figure 5: Percentage of satisfied users in terms of throughput. Figure 6: Packet loss ratio vs. number of users. Form Figure 7, it is depicted that the MOS score for our method is higher than the other scores for other methods even when the number of users is increasing. The hybrid algorithm for power allocation is playing a good role in having good MOS since it is related to the data rate of the video. Then, as long as the data rate is high, the MOS score is better. This would mean better quality of PSNR, which is according to Equation (15), has a strict relation with MOS score. To interpret the simulation results, it is clear that the algorithms that are not using power allocation have lower MOS scores since the users who are experiencing interference will not have big data rates, and, consequently, lower PSNR and MOS scores. The conclusion can be even deduced from the relationship between Figures 6 and 7. ## 7 Conclusions

In this article, we proposed a rate adaptive solution for a video streaming in an interference scenario based HetNet. We suggested a complete framework that first performs interference mitigation based on a hybrid method. This hybrid method is based on power control that is achieved in a combination of centralized and distributed schemes depending on the clustering method used to divide the network into clusters and sub-clusters of femtocell. Once the interference is mitigated, then the rate adaptation is carried out through the allocation of an appropriate number of resource blocks to the base layer of the video streaming traffic. This would guarantee the best quality for the video in terms of throughput and latency in terms of QoS. As for QoE, we studied the perception of the end user to the quality of the image that he/she received through a logarithmic relationship between MOS and PSNR. We proved that our method delivers the best QoS and QoE to the interfered users comparing to different methods in the literature. [PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the experiments; [PERSON] and [PERSON] analyzed the data and the simulation results; [PERSON] wrote the literature review section while [PERSON] wrote the system design and the simulation results sections. The authors declare no conflict of interest. ## References

* [PERSON] et al. (2008) [PERSON]; [PERSON]; [PERSON] Femtocell Networks: A Survey. _IEEE Commun. Mag._**2008**, 46, 59-67, doi:10.1109/MCOM.2008.4623708. * [PERSON] et al. (2009) [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON] OFDMA Femtocells: A Roadmap on Interference Avoidance. _IEEE Commun. Mag._**2009**, 47, 41-48, doi:10.1109/MCOM.2009.5277454. Figure 7: MOS vs. number of users. * (3) [PERSON] _Understanding LTE and Its Performance_, 1 st ed. ; Springer: New York, NY, USA, 2011; pp. 1-244, ISBN 978-1-4419-6457-1.