Why Latency Matters to Mobile Backhaul - O3b Networks

Why Latency Matters to Mobile Backhaul
Figure 12 shows that the maximum TCP throughput degrades rapidly as
latency increases.
The same illustration for an interactive service is considered: an HSPA
access over satellite to Internet service (c.f. Figure 9 and Figure 10 for detail
on each case).
The maximum throughput for TCP Reno will be 2.1 Mbps for O3b and
775 kbps for GEO satellite. This will be the maximum achievable rate for a
TCP connection, such as a single user communicating with a server. Table 5
estimates the transfer time for various media for both backhaul links for a
single TCP stream.
O3b
2 MB Song 10 seconds 28 seconds
1.5GB Movie 1.66 Hours 4.5 Hours
3.8GB HD Movie 4.25 Hours 11.4 Hours
Table 1: Estimated transfer time comparison between O3b and GEO backhaul
The subscriber QoE for these types of services is directly related to the
download time. The lower latency of the MEO case results in a huge
improvement in download times and subscriber QoE.
GEO
Non real time video streaming
Video streaming was traditionally transported over UDP, but major web
sites such as YouTube and DailyMotion now use either Adobe Flash Video or
HTML5:
− HTML5 is delivered using HTTP over TCP.
− Adobe Flash Video can be delivered using:
− FLW or SWF Files downloaded using a browser with HTTP over TCP
− Progressive download over HTTP over TCP
− Real Time Messaging Protocol over TCP directly or through HTTP tunnel
over TCP
− HTTP Live Streaming format over TCP.
With all the major providers of web video streaming now using TCP
transport for video streaming, the latency impact on the degraded user
experience will be exactly the same for Internet video streaming as it is for
data file transfer.
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