# Block Recovery Rate-Based Unequal Error Protection for Three-Screen TV
## 4 Experimental Results and Discussion  
### H.264 SVC Unequal Error Protection Using Reed-Solomon(RS) Codes without Layer Switching  
This section reveals simulation results of the proposed FEC algorithm for the performance analysis by using version 9 of the Joint Scalable Video Model [30]. We used common intermediate format (CIF) video sequences '_Foreman_' and '_Mobile_' sequences with a frame rate of 30 fps. The number of frames was 81 and the size of the group of pictures (GOP) was 16 frames.  
There were five temporal layers with one quality base layer and two quality enhancement layers. Quantization parameters (QPs) were set to be 40, 30, and 25. A two-state Markov channel model described in [31] was used for modeling the packet losses with the average burst length of \(Lb\) and the average packet loss rate of \(Pb\). The value of \(Lb\) is set as 2. Using different packet loss rates (5%-15%) the proposed unequal error protection method using block recovery rate in (3) (BRR-UEP) was compared with other unequal error protection schemes.  
* BRR-UEP: The proposed block recovery rate-based UEP (BRR-UEP) performs the unequal FEC assignment by calculating the block recovery rate for each layer through the hierarchical prediction structure analysis in quality and temporal layers including the packet loss rate.
* RD-UEP: For allocating unequal amount of FEC protection to different video packets, the rate-distortion based UEP (RD-UEP) method utilizes the simple rate-distortion model without considering the recovery rate for each block according to the current packet loss rate [15; 17].
* Equal EP: The equal error protection (EP) allocates an equal amount of FEC packets for all packets in different layers without considering the performance metric.  
Figure 8 shows the variations of \(R_{avg}\) in (3) according to the total number of FEC packets (\(T_{pik}\)) in variable channel environments. As the packet loss rates are increased, the block recovery rate is gradually decreased. Furthermore, it is observed that as the number of FEC packets is increased, the value of \(R_{avg}\) is increased.  
Figure 9 shows the distribution of \(F(t,q)\) for each temporal (\(t\)) and quality (\(q\)) layer at different packet loss rates \(Pb=5\%\) and \(Pb=15\%\), respectively. Redundant FEC packets are intensively assigned to the lower block index. This is because based on a hierarchical prediction structure in the scalable video, packet losses in lower blocks have stronger error propagation effects than those in the higher blocks.  
Figure 10 shows the peak signal-to-noise ratio (PSNR) comparisons of BRR-UEP, RD-UEP, and Equal EP. It is observed that Equal EP shows the lowest PSNR values. The proposed BRR-UEP scheme  
Figure 8: Variations of \(R_{avg}\) according to the total number of FEC packets (\(T_{pik}\)) in different packet loss rates.  
The proposed UEP method was validated using NS-3 network simulator [32]. The network topology was implemented as shown in Figure 11. The video server produces layer based scalable video packets with temporal and quality scalabilities and transmits real-time transport protocol/user datagram protocol/internet protocol (RTP/UDP/IP) packets to the corresponding receivers with various decoding capabilities through a wireless access point (AP). Exponential traffic using UDP packets is additionally added to simulate a congested environment.