Communication Latency

8/13/2019 Communication Latency

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Latency minimization

in data communication

Presented By: Ishita Akhter

Date: 11/07/2013


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Introduction: Latency Overview

Latency Sources

Latency background

Latency research motivations

The research project

Intended timeline

Tasks performed

Current simulation setup

Observations

Discussions

Future targets

Conclusions

References

Presentation topics


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Definition

Delay between a command and corresponding reaction

Prominently used in Psychology, Biology, Computer Science,

Communication Networking etc.

Focus of current discussion is Communication Latency

The time duration of exchanging a packet (APDU) within a

communication network

One-way delay or RTT (Round Trip Time)

Example evident inSlow audio/video transmission, lateresponse in gaming commands, delayed arrival of data files

etc.

Introduction: Latency Overview

Source:

o D. Delaney, T. Ward and S. McLoone, "On consistency and network latency in distributed interactive

applications: A survey-Part I," Presence: Teleoperators & Virtual Environments, vol. 15, no. 2, pp. 218-234,

2006.


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Processing Delay: Preparation time on each arriving packet, before being queued (Typically within srange)

Queuing Delay: Waiting time for processed packet to be transmitted into the physical link

(Expressed as, QD =Used memory

Packet processing speed, Typically within s - ms range)

Transmission delay: Transfer time for all bits of a packet into the start of physical link (Expressed as, TD

= 1Interface speed , Typically within s - ms range) Propagation delay: Travelling time for packet all through the physical link towards destination node

(Expressed as, SPD =Packet travelling distance

Propagation speed , Typically within ms range)

Figure: Communication network scenario

Latency Sources

Source:

o J. F. Kurose and W. R. Keith, Computer Networking: A Top-Down Approach, Essex: Pearson, 2013.

o ONPATH Technologies, "White Papers - Physical layer switching," 2013. [Online]. Available:

http://www.onpathtech.com/assets/WhitePapers/ONPATHLatencyWP.pdf. [Accessed 20 6 2013].


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Earliest latency observationdelay in repetitive sound generationof volcano eruptions (19121916)

Latency observation within circuit-switched telephone networks(1930s1960s)

Latency investigation in packet-switched communications (1970spresent)

Network performance issues over the last thirty years

Table: Comparison of network performance issues

Recent latency-oriented researches focus on measurement,estimation, possible solutions etc.

Latency background


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Latency effects

Reduced efficiency in real-time interactivity

Data congestion and loss of information

Complicates relevant system/application design

Overall network performance degraded

Less favourable user experience

General latency improvement policies

Better hardware with lesser processing times

Congestion control mechanisms to downsize queuing

Better compression techniques for faster transmission

Relocating network equipment to reduce propagation time

Latency research motivations


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Latency investigation schemes

End-to-end latency measurements

Wireless network latency estimations

Online gaming latency dimensions

Miscellaneous latency observations (IPV6, channel,positioning, satellite, telemedicine etc.)

Significant latency improvement initiatives

Remote access latency minimization

Mobile environment latency improvements

Packet-switching latency enhancements

Developing low-latency communication mechanisms/systems

Latency research motivations (cont.)


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Latency-based research mostly around layer- 3 (Network layer)

Insignificant latency observation for layers 1 & 2 (physical &

data link layer)

Effects on latency with physical layer modulation schemes-

unexplored initiative in physical layer

Latency by MAC header processing-not observed for data

link layer

Latency due to data coding techniques-still offering scopes of

in-depth observations

Not enough attempts to relate energy consumption and latency

Not enough observation of individual layer latencies

Latency research motivations (cont.)


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Project title

Latency minimization in data communications

Primary directive

Investigating latency in first 3 OSI reference model layers

Initial attempt

Spectral efficiency & latency relation in physical layer

Simulator tool

Simulink by Mathworks

The research project


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Research directives Timeline

Literature review on communication latency in

OSI layers

Month(s) 1- 2: (November 2012

December 2012)

Selecting research project focus areas andfinalizing on tasks & tools to be used

Month(s) 3 - 4: (January 2013February 2013)

Building-up skills on software for system

simulations, e.g. Simulink

Month(s) 5 - 6: (March 2013April

2013)

Designing & simulating systems on different

modulation schemes

Month(s) 6 - 10: (May 2013August

2013)

Experimenting with the developed systems,

possible paper publication

Month(s) 11- 12: (September 2013

October 2013)

Preparation for the PhD conversion Month(s) 13: (November 2013)

Intended timeline


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Literature review on latency publications

Research project defining

Finalizing on tasks & tools

Building-up software skills

Designing & simulating on different modulation schemes

Tasks performed


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System components: Source, transmitter, ideal/noisy channel, receiver,destination, result scopes, BER calculator and delay calculator

Simulated systems: OOK, ASK, BPSK & BFSK

Experimental setup


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Transmitted modulated signal

= (), 1(), 0 Signal passes through communication channel, reaches receiver side as

received signal

= , + , , = noise signal is multiplied with a reference unit-energy wave = () (),

to become = Integrating for the period (0, Tb), where Tb= bit transmission time, to

get signal,= Integrated signal passes through the decision device, compared to

threshold

if > , bit detected as 1 and if < , bit detected as 0

Experimental setup (contd.)

Source:

o R. C. T. Lee, M. C. Chiu and J. S. Lin, "Digital Modulation Techniques," in Communications Engineering:

Essentials for Computer Scientists and Electrical Engineers, 2008, pp. 135-188.

o D. Silage, "Bandpass Modulation and Demodulation," in Digital Communication Systems Using MATLAB andSimulink, Bookstand Pub., 2009.


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Observations

Figure: Example of delay comparison


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Initial observation

Component-by-component approach showing delay for

ideal/noisy channels

Non-coded information transmission/reception performed forsingle-level modulation schemes

Delay seen at demodulation, specifically just before integration

Simulating with ideal software blocks provide no delay

Further results expected with ongoing system-build up using

higher order modulations

Observations (contd.)


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Modulationscheme

Constellationpoints (M= 2k)

Bit transmissionrate (k)

Spectral efficiency(bps/Hz)

Delay(Samples)

OOK 2 1 1 1

ASK 2 1 1 1

BPSK 2 1 1 1

BFSK 2 1 1 1

Discussions

Systems simulated have the same spectral efficiency, exhibiting same amount of

delay

Same results obtained for both noisy/ideal channels (component-by-component

approach)

Delay possibly in order to detect transient behaviour of incoming signal Default simulator blocksets solve systems ideally with numerical method

Further designs are being developed with modulation schemes having higher

spectral efficiencies and additional coding components

Source:

o S. Tomazic, "Spectral Efficiency," in Encyclopedia of Wireless and Mobile Communications, 2008, pp. 1095-

1099.o Mathworks, Simulink documentation, 2012.


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Latency observation by

Building higher-order modulation systems & observing

spectral efficiency and latency relation

Inclusion & observation of latency in MAC layer processing

Observation of system energy consumptions in relation with

latency

Relate above observations with established findings on

network layer

Future targets


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Addressed issues so far

Defined latency, its sources

Provided latency research background/history

Explained latency-based research motivations Summarized the research project, along with

intended workplan/timeline

Elaborated on tasks performed

Explained experimental setup, observations andrelated discussions

Described future targets within the scope of theproject

Conclusion


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Questions/comments??

Thankyou


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References


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[11] ONPATH Technologies, "White Papers - Physical layer switching," 2013. [Online]. Available:

http://www.onpathtech.com/assets/WhitePapers/ONPATHLatencyWP.pdf. [Accessed 20 6 2013].

[12] Cisco Systems, Inc., "Design Best Practices for Latency Optimization," Financial Services Technical Decision Maker

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References


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References


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[52] Mathworks, Simulink documentation, 2012.

References

Documents

Communication Latency