Open-Loop Algorithms - Scalable Continuous Media Streaming Systems - page 318

18.5 Performance Comparisons
To illustrate the performance trade-offs in various open-loop algorithms, we present in this
section performance results of Consonant Broadcasting together with Skyscraper Broadcast-
ing (SB), Greedy Disk-Conserving Broadcasting (GDB), Staircase Data Broadcasting (SDB),
Poly-harmonic Broadcasting (PHB), and Pagoda Broadcasting (PB). In computing the numeri-
cal results, we use a media stream of length L

00 seconds (2 hours) and assume the client
access bandwidth is equal to twice the media bit-rate, i.e., 2 b . For example, if the media bit-
rate is 3Mbps, then the client access bandwidth is 6Mbps, within the limit of current 10Mbps
Ethernet. All open-loop algorithms are optimized using procedure proposed by the original
studies [2-4, 6, 7] to configure their operating parameters. The following sections compare
these algorithms in terms of start-up latency and client buffer requirement, with respect to the
network bandwidth required.

= 72 ,

18.5.1 Start-up Latency versus Network Bandwidth
Start-up latency is defined as the maximum time from a client entering the system to the time
media playback starts. With a client access bandwidth of 2 b , we plot in Figure 18.2 the start-up
latency versus the network bandwidth ranging from 2 b to 10 b .
The results in Figure 18.2 show that PHB achieves the lowest start-up latency, close to the
theoretical lower bound when configured with large value of m (e.g., 16). Similarly, PB also
achieves very good performance, comparable to CB with m 1. However, unlike the other

schemes, we did not apply the client access bandwidth constraint in computing results for PHB

=

10

CB, m= 1
CB, m= 2
CB, m= 4
CB, m= 16

SB : Skyscraper Broadcasting
GDB3 : Greedy Disk-Conserving Broadcasting 2

SDB : Staircase Data Broadcasting
PHB : Poly-harmonic Broadcasting
CB : Consonant Broadcasting
PB : Pagoda Broadcasting
LB : Lower Bound

8

PHB, m=16
( without client
access bandwidth
constraint )
PHB, m=1
( without client
access bandwidth
constraint )

GDB3

6

PB

SB

4

SDB

2

LB

0

2 b 4 b 6 b 8 b 10 b

Network bandwidth (multiples of video bit-rate b ) wi le )

Figure 18.2 Start-up latency versus network bandwidth at large latency range