# Transmitter Diversity Gain Technique Aided Irregular Channel Coding for Mobile Video Transmission
## 6 Results and Discussion
### EXIT Chart Analysis of the Constituent Decoders  
ISCD schemes operate on residual redundancy as a prime source of error protection in the coded video bitstream. More specifically, the decoder exchanges the information b/w the constituent decoders to obtain the highest possible information regarding the transmitted stream. The main goal of iterative channel decoding is to glean the highest possible extrinsic information \(\left[L_{IRCC}^{\text{extr}}(x_{i})\wedge L_{\text{URC}}^{\text{extr}}(x_{i})\right]\). The constituent inner and outer decoder in iterative channel decoding iteratively assist each other to extract the maximum possible extrinsic information. The idea of the EXIT chart is presented by [PERSON] in order to examine the exchange of mutual information between the constituent inner and outer decoders, employed in an iterative decoding fashion [47]. The detailed description regarding A-priori information (\(I_{A}\)), A-posteriori LLR(\(I_{E}\)), and Extrinsic Information (\(I_{E}\)) can be found in [30]. The results that are presented in the paper were obtained by employing Monte Carlo simulation model. The simulations were carried out using 45 frames of the \"AKIYO\" video sequence as input vide stream, while experiments were repeated for 260 times for the considered transmission conditions and its average considered as the expected outcome. The amount of available a-priori knowledge at the demapper dictates the extrinsic information transfer. EXIT chart is plotted between demapper and decoder for observing the exchange of extrinsic information. The channel inner extrinsic information output \(I_{E1}\) becomes the outer a-priori input \(I_{A2}\), while the outer extrinsic information output \(I_{E2}\) becomes the inner a-priori knowledge \(I_{A1}\), as plotted on the y-axis and x-axis, correspondingly. EXIT chart predictions are verified by the simulation results from the decoding trajectories. The decoding transfer characteristic is plotted for both IRCC unicode and IRCC multicode with precoder at \(E_{b}/N_{0}=1\) dB, and 2 dB, as shown in Figure 5a. The IRCC unicode intersect  
Figure 4: Extrinsic Information Transfer (EXIT) characteristic curves of IRCC 17 constituent subcodes. at lower mutual information, while the IRCC multicode intersects at higher mutual information, which shows that the IRCC multicode results in a wider open tunnel between the demapper and decoder. From Figure 4(b), the decoding transfer intersect and decoding trajectory of the IRCC unicode is stuck after five iterations at lower mutual information, which results in a higher BER rate at \(E_{b}/N_{0}=1\) dB, while, for the same IRCC unicode, the decoding trajectory intersects at slightly higher mutual information, but does not achieve the perfect convergence, such as \((I_{A},I_{E})=(1,1)\) at \(E_{b}/N_{0}=2\) dB. Similarly, Figures 4(c),d show the decoding trajectory for IREP-1 and IREP-2, correspondingly. For \(E_{b}/N_{0}\) of 1 dB, the decoding transfer has limited performance after five iterations, while, for \(E_{b}/N_{0}=2\) dB, due to an open EXIT tunnel, the performance gain is high, due to iterative convergence close to \((I_{E},I_{A})=(1,1)\) point. Figure 4(a) records and depicts the outer EXIT characteristic curves of the IRCC multicode and the IRCC unicode. The analysis shows that the IRCC multicode results in a relatively wider open tunnel in combination with the inner URC code as compared to that of the counterpart with the same 3/4 code-rate. Furthermore, the IRCC multicode has the innate irregular capability to irregularly treat the H.264/AVC coded stream having three different types of partitions with varying relative importance. Therefore, our system design with a IRCC multicode for a similar code rate as that of unicode would have the additional advantage of irregular treatment capability for the H.264/AVC coded stream.