Information Technology Reference
In-Depth Information
Mobile Peers
Among the parameters, δ and γ are parameters
for ACP. To find the optimal values for δ and γ,
we conducted detailed experiments to learn the
effects of them on ACP's performance. We find
that ACP performs best when δ and γ are set to
values between 0.3 and 0.6. In the experiments
presented as follows, we use 0.3 and 0.5 as optimal
values of δ and γ. The parameters of DGCoca are
not listed here. We follow (Chow, 2005) to assign
values to DGCoca's parameters.
A variant of the “random waypoint” is used as
the mobile peers' movement pattern. A mobile
peer first randomly chooses a destination in
the modeled area and a speed which is around
MoveSpeed
m/s. Then the mobile peer moves to
the destination with that speed. After arriving
at the destination, the mobile peer pauses for
PauseTime
seconds. The mobile peer repeats the
aforementioned steps.
We call the set of data objects that a mobile
peer is interested in as its access range. Access
range consists of access regions (an access region
is used to model a cluster of data objects related
to one interest topic) that the mobile peer is in-
terested in. The size of a mobile peer's access
range is
AccessRange
, and the size of an access
region is
RegionSize
, thus the number of access
regions for each mobile peer is
AccessRange
/
RegionSize
. We assign a Zipf distribution with a
skewness parameter
θ
to each mobile peer's ac-
cess regions. The data objects within an access
region have the same probability to be accessed.
When assigning access distributions to the access
regions, the access regions from faster disks get
higher access probabilities.
A mobile peer's queries are generated accord-
ing to its access distributions. A query is simply
an access request for a data object. The time
interval between a mobile peer's two consecu-
tive queries is
ThinkTime
broadcast units. Each
mobile peer generates
NumQuery
queries during
the simulation.
The size of each mobile peer's cache space is
CacheSize
, which is a fraction of the size of the
peer's
AccessRange
. For example, if the size of
AccessRange
is 1000 and the
CacheSize
is 20%,
then the peer's cache space can hold 200 data
objects.
Table 1. Simulation model parameters
Parameter
Default Value
Range
Unit
System
Parameters
Area (X*Y)
1500*1500
m
2
bb
(broadcast
bandwidth)
10
Mbps
sb
(short-range
bandwidth)
2
Mbps
n
(num of clients)
100
Server
m
(num of disks)
3
DiskSizes
[500,1500,3000]
Data
objects
Δ
3
[0-4]
DataSize
10
[10-100]
KB
Mobile Peer
TransRange
250
[0-250]
m
AccessRange
1000
Data
objects
RegionSize
50
Data
objects
CacheSize
20%
[1%-50%]
MoveSpeed
2
[0-20]
m/s
PauseTime
30
s
NumQuery
3000
θ (Zipf)
0.5
[0-1.0]
ThinkTime
10
Broadcast
Unit
ACP specific
δ
List of Parameters
0.3
[0-1.0]
γ
0.5
[0-1.0]
The parameters for the simulation model and their
values are summarized in Table 1.
Search WWH ::
Custom Search