1. Figure 2.1. Systematic form of a codeword of a block code

2. Figure 2.2. Block diagram of a FEC system

3. Figure 2.3. Bit error probability for the three times repetition code

4. Figure 2.4. Block diagram of an ARQ system

5. Figure 2.5. Stop and Wait ARQ scheme

6. Figure 2.6. A Go-Back N ARQ scheme

7. Figure 2.7. Selective Repeat ARQ Scheme

8. Figure 2.8. Efficiency relative to for Stop-and-Wait, Go-Back-N and Selective Repeat ARQ schemes, with rb=262; k=262 n=254, N=4, 32 and 128 (Go-Back-N); and for td=0.01, 0.1 and 1 (Stop-and-Wait)

9. Figure 2.9. First alternative of the hybrid-ARQ Type 2 iterative scheme

10. Figure 2.10. Second alternative of the hybrid-ARQ Type 2 iterative scheme