WMI Voice+Video Bluetooth

8/9/2019 WMI Voice+Video Bluetooth

1/15

Ad Hoc Networking with Bluetoot

Wireless Mobile Internet

Mobicom, Rome, Italy, July 2001.

Mario Gerla, Rohit Kapoor,

Manthos Kazantzidis (UCLA),

Per Johansson (Ericsson)


2/15

Focus of the Paper

Focus on the single PAN environment

Communication occurs only inside a PAN (No inter-

PAN comm.)

Such a scenario may be typical in an ad-hoc groupcollaboration

Each PAN may correspond to single user or

Members of same team may sit nearby and interact with

each other (exchange files, video-conference etc)

Evaluate multimedia support in such an

environment


3/15

Focus of the Paper

Two candidates for role of MAC layer in

PANs:

IEEE 802.11- We assume use of DCFmode, which is the mode implemented in

the WaveLAN cards.

Bluetooth We investigate only ACL links


4/15

Simulation Environment

Simulation environment is NS-2

It supports the 802.11 in the DCF mode

We augmented NS with the Bluetooth model

Bluetooth model MAC layer implements features like FH, TDD, Multi-

slot packets, ARQ etc.

Channel model takes into account path loss, shadowing

and fading. Slave polling strategy is the one used by Capone et.al.

(Efficient Polling Schemes for Bluetooth picocells,

ICC 2001)


5/15

Case Study

Conference Hall

Assume no infrastructure in the form of access points

Bluetooth or WaveLAN devices wanting to

communicate

Simulation parameters

50m * 100m room; nodes randomly distributed

For Bluetooth, piconets formed by clustering nodes

close enough to each other; number of slaves in eachpiconet chosen randomly

Piconets may overlap, causing collisions

Traffic consists of mix of TCP, Video and Voice


6/15

Case Study (cont)

Voice Model

Brady model On-off Voice sources, on and off times

exponentially distributed, with mean 1sec and 1.35 sec

respectively Voice coding rate is 8 Kbit/s, packetisation period 20ms

TCP connections are large file transfers, 500-byte

packets

TCP, Voice, Video connections in the ratio 1:1:1

Experiments performed for different values of

number of nodes and connections


7/15

Video Traffic

Video sources Real traces (Star Wars trailer clip, encoded using Intels

H.263 compatible codec)

Traces smoothed a frame returned by the codec is

distributed uniformly in time using a target of 200-bytepackets

Figure 1: A few seconds from the H263 source trace (sec, bytes)


8/15

Video Traffic

Adaptive and non-adaptive video

Non-adaptive video average rate 256Kbps

Adaptive video

Uses average rates of 48, 64, 80, 128 and 256 Kbps Adaptation is based on end-to-end periodic (1sec)

feedback of number of pkts received in the interval

Server adapts its sending rate using max/min threshold

If loss rate < min threshold(=5%), server increases rate If loss rate > max threshold(=15%), server reduces

rate, choosing a rate that is appropriate to support the

reported loss rate


9/15

Video Traffic Experiment

Experiment targets at showing adaptive behaviorof video with 802.11 and Bluetooth

Experiment parameters

30 nodes, 60 connections

90% of connections start at 8.6s and finish at 16.6s Others start at 0.5s and run till 32s (end of simulation)

We study the adaptive behavior of a video connectionthat lasts throughout

When more connections are added (8.6s) WaveLAN downgrades to lowest possible rate due tohigh loss rates

Bluetooth downgrades gradually since loss rates arelower


10/15

End-to-End Adaptation

Fewer packets get lost for Bluetooth, but their

delay is increased:

WaveLAN retransmits a collided packet a finite no. of

times and then drops it; high collisions lead to large no.

of packet drops

In Bluetooth, collisions are low due to FH; fewer

dropped packets

Bluetooth WaveLAN


11/15

Conference Hall experiment for different number of

nodes and connections - Non-Adaptive Video

Loss Rates for video connections

for H.263(x-axis is no. of nodes/

no. of connections)

256Kbps H263 Streams - Loss rates

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

30/30 30/60 50/30 50/60

Wavelan

Bluetooth


12/15

Conference Hall experiment for different number of

nodes and connections - Adaptive Video

Video

Loss rates higher for

WaveLAN In Bluetooth, loss rates

are less than 1%

Loss rates are reduced in

WaveLAN compared tonon-adaptive video

Adaptiv - rat

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

30/30 30/

0 50/30 50/

0

WaveLan

Bl

et

t


13/15

Voice Results 30 nodes, 60 connections

A play-out buffer of 350msmay be needed for a packet loss

ratio of less than 5%

Since the scenario is of a

congested network, uncontrolledaccess to channel causes large

no. of collisions

A play-out buffer of 80 msachieves the same loss rate

Voice delays lower for

Bluetooth

Controlled access of BTachieves keeps delays low

ComplementaryCumulative Delay Distribution for

Voice in WLan

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.80.9

10 30 50 70 90 110

130

150

170

190

210

230

250

350

450

600

Delay (ms) --->

Fraction

ofPkts--->

Compl ment r Cumul ti e el i tri ution

for oi e inBluetooth

0

0.

0.

0.

0.

0.

0.

0.

0.

0.

0 14 18 22 24 28 40 60 80 100

Del

(ms) ---

r

tion

of

ts

---

!


14/15

Results

Aggregate throughput Higher in WaveLAN for small number of nodes

For larger no. of nodes, BT increases capacity

For larger no. of connections, more collisions in WaveLAN

cause throughput to be lower TCP and Video share bandwidth better in Bluetooth

Useful" andw idt # s

$

it#

Adaptive%

ideo

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

30/30 W v 30/30 B t 30/&

0 W v 30/&

0 B t 50/30 W v 50/30 B t 50/&

0 W v 50/&

0 B t

TCP

Vid eo

Total

Loss Rates for adaptive video connections for H.263(x-axis

is no. of nodes/ no. of connections)


15/15

Conclusion

Bluetooth performs well in mixed data and real-

time traffic scenarios

Gives better delays to voice traffic; lower loss rates for

video Bandwidth is shared better between Video and TCP;

TCP does not show capture effect in Bluetooth

WaveLAN has higher system throughput for small

number of nodes, but Bluetooth catches up when

number of nodes is increased

Experiments performed with DCF mode of

802.11; in future, we plan to repeat for PCF mode

Date post:	30-May-2018
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WMI Voice+Video Bluetooth

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