Come fa la latenza del WiFi a paragonarsi alla Ethernet cablata?

On my home netwrok, here is the result of ping from my wired desktop computer to the router using a 50 foot long Ethernet cable.

1. addola@LinuxBox:~$ ping -c 8 192.168.1.1 
2. PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data. 
3. 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.265 ms 
4. 64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=0.299 ms 
5. 64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=0.272 ms 
6. 64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=0.276 ms 
7. 64 bytes from 192.168.1.1: icmp_seq=5 ttl=64 time=0.286 ms 
8. 64 bytes from 192.168.1.1: icmp_seq=6 ttl=64 time=0.261 ms 
9. 64 bytes from 192.168.1.1: icmp_seq=7 ttl=64 time=0.251 ms 
10. 64 bytes from 192.168.1.1: icmp_seq=8 ttl=64 time=0.275 ms 
11. --- 192.168.1.1 ping statistics --- 
12. 8 packets transmitted, 8 received, 0% packet loss, time 7171ms 
13. rtt min/avg/max/mdev = 0.251/0.273/0.299/0.016 ms 

This is the ping results from my MacBook Pro to the router that is connected with 5 Ghz WIFI. The laptop is in the same room.

1. adil@Darwin:~$ ping -c 8 192.168.1.1 
2. PING 192.168.1.1 (192.168.1.1): 56 data bytes 
3. 64 bytes from 192.168.1.1: icmp_seq=0 ttl=64 time=2.069 ms 
4. 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=1.250 ms 
5. 64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=2.038 ms 
6. 64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=2.208 ms 
7. 64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=2.115 ms 
8. 64 bytes from 192.168.1.1: icmp_seq=5 ttl=64 time=1.354 ms 
9. 64 bytes from 192.168.1.1: icmp_seq=6 ttl=64 time=2.020 ms 
10. 64 bytes from 192.168.1.1: icmp_seq=7 ttl=64 time=1.402 ms 
11. --- 192.168.1.1 ping statistics --- 
12. 8 packets transmitted, 8 packets received, 0.0% packet loss 
13. round-trip min/avg/max/stddev = 1.250/1.807/2.208/0.371 ms 

This is for 2.4 Ghz

1. adil@Darwin:~$ ping -c 8 192.168.1.1 
2. PING 192.168.1.1 (192.168.1.1): 56 data bytes 
3. 64 bytes from 192.168.1.1: icmp_seq=0 ttl=64 time=1.372 ms 
4. 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=2.108 ms 
5. 64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=1.351 ms 
6. 64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=2.209 ms 
7. 64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=1.335 ms 
8. 64 bytes from 192.168.1.1: icmp_seq=5 ttl=64 time=1.392 ms 
9. 64 bytes from 192.168.1.1: icmp_seq=6 ttl=64 time=1.445 ms 
10. 64 bytes from 192.168.1.1: icmp_seq=7 ttl=64 time=2.106 ms 
11. --- 192.168.1.1 ping statistics --- 
12. 8 packets transmitted, 8 packets received, 0.0% packet loss 
13. round-trip min/avg/max/stddev = 1.335/1.665/2.209/0.371 ms 

The wired connection has an advantage of only 1.5ms.

However, keep in mind that WiFi latency will fluctuate more than wired connections. Questo si chiama "jitter"

Possiamo analizzare l'effetto che la larghezza di banda ha sulla latenza, dal momento che il WiFi che ho supporta 300 Mbps contro 1 Gbps o 10 Gbps per la connessione Wired ethernet. Tuttavia, per un pacchetto di 64 Bytes il ritardo di trasmissione (tempo che impiega il dispositivo di rete a spingere i dati nel mezzo è calcolato come segue:

Per 300 Mbps

[math]\frac{8 \times 64 Bytes} {300 \times 2^{20} bps} = 0.0000016276 \textbf{ secondi} = 0.0016276 \textbf{ ms} [/math]

E se la larghezza di banda è di 10 Gbps, allora per un pacchetto di 64 Bytes è:

[math]\frac{8 \volte 64 Bytes} {10 \volte 2^{30} bps} = 0.0000000476837 \textbf{ secondi} = 0.0000476837 \textbf{ ms} [/math]

Quindi non è la larghezza di banda che fa la grande differenza. Il ritardo di propagazione è il ritardo dominante qui.