The following figure shows that, using relays can extend communication distances. Assume the Decode-and-Forward relays are utilized, and application traffic is FTP/TCP. The peak Throughput (TP) is 42 Mbps for a single Access Point (AP) without using relays. Briefly explain why the peak Throughput (TP) drops to around 20 Mbps using 1 relay, around 14 Mbps using 2 relays and approximate 10 Mbps using 3 relays.

Throughput with fixed relays at different distances 45 TP at AP TP at relay 1 at 100 m (20 dB receive antenna gain) TP at relay 2 at 200 m (20 dB receive antenna gain) TP at relay 3 at 300 m (20 dB receive antenna gain) Maximum acheivable TP 40 35 30 25 High bit rate due to receive antenna gain at fixed relays 20 10 0 0 50 100 150 200 250 300 350 400 450 500 Distance (m) AP Relay 1 Relay 2 Relay 3 Throughput with fixed relays at different distances 45 TP at AP TP at relay 1 at 100 m (20 dB receive antenna gain) TP at relay 2 at 200 m (20 dB receive antenna gain) TP at relay 3 at 300 m (20 dB receive antenna gain) Maximum acheivable TP 40 35 30 25 High bit rate due to receive antenna gain at fixed relays 20 10 0 0 50 100 150 200 250 300 350 400 450 500 Distance (m) AP Relay 1 Relay 2 Relay 3