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Improving Communication Quality with Reed Solomon Code in Internet Voice Broadcasting System . Shingo Kashima Kyushu University, Japan. Asia-Pacific Advanced Network 2003 January 21-24, 2003 Fukuoka, Japan. Plan of Presentation. Background (Existing Issue) Objective Icecast

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improving communication quality with reed solomon code in internet voice broadcasting system

Improving Communication Qualitywith Reed Solomon Codein Internet Voice Broadcasting System

Shingo Kashima

Kyushu University, Japan

Asia-Pacific Advanced Network 2003

January 21-24, 2003

Fukuoka, Japan

plan of presentation
Plan of Presentation
  • Background (Existing Issue)
  • Objective
  • Icecast
  • Solution of Issue
  • FEC and Reed Solomon Code
  • Proposal of System
  • Evaluation
  • Future Work
  • Summary
background 1 of 2
Background [1 of 2]
  • Music Delivery in Real Time
    • 1 to 1 communication using client-server model
background 2 of 2

Modify existing applications

  • Expensive
Background [2 of 2]
  • Issues in the Current Model
    • A heavy load is applied at the network between client and server.
    • The number of clients is limited by bandwidth of network between client and server.
    • Sound is interrupted or noise occurs.
  • Solution
objective
Objective
  • Improve the communication quality ofa large scale real time voice broadcasting on the Internet without modifying the existing applications.
icecast
Icecast
  • Audio streaming server
  • Developed under the GNU General Public License
  • Support MP3, HTTP / TCP
  • Support many client applications
    • ex. WindowsMediaPlayer, Winamp, XMMS, etc
  • Relay function (described later)
issues in the current model
Issues in the Current Model
  • A heavy load is applied at the network between client and server.
  • The number of clients is limited by bandwidth of network between client and server.
  • Sound is interrupted or noise occurs.
issues in the current model8
Issues in the Current Model
  • A heavy load is applied at the network between client and server.
  • The number of clients is limited by bandwidth of network between client and server.
  • Sound is interrupted or noise occurs.
solution of issues i ii

m

n

n

m

n

n×m

Solution of Issues I, II
  • Distributed Delivery by Relay Server
    • The load of network is reduced.
    • The number of clients increases.
issues in the current model10
Issues in the Current Model
  • A heavy load is applied at the network between client and server.
  • The number of clients is limited by bandwidth of network between client and server.
  • Sound is interrupted or noise occurs.
solution of issue iii 1 of 5

Delay by Retransmission of TCP

  • TCP ・・・ Transmission Control Protocol
Solution of Issue III [1 of 5]
  • Factor of Issue III
solution of issue iii 2 of 5

Ack nowledgement

Ack nowledgement

Ack nowledgement

Ack nowledgement

Ack nowledgement

Ack nowledgement

Solution of Issue III [2 of 5]
  • The Communication with TCP

Client has received

the packet.

solution of issue iii 3 of 5

LOSS!

Solution of Issue III [3 of 5]
  • The Communication with TCP

Ack nowledgement ??

Ack nowledgement ??

Ack nowledgement ??

Ack nowledgement ??

Ack nowledgement ??

When a packet is lost.

solution of issue iii 3 of 514
Solution of Issue III [3 of 5]
  • The Communication with TCP

No ack nowledgement!

Retransmission

When a packet is lost.

solution of issue iii 4 of 5

Buffer data at clients

  • Replace TCP with UDP in transport layer
    • UDP has no Retransmission Control
    • UDP ・・・ User Datagram Protocol
Solution of Issue III [4 of 5]
  • Delay by Retransmission Control of TCP
solution of issue iii 5 of 5

Need to guarantee for packet loss in application layer

  • FEC (Forward Error Correction)
    • FEC resotores lost packets
Solution of Issue III [5 of 5]
  • UDP is not reliable for arrival of packet
slide17
FEC

×

×

×

Burst

Error

Reed Solomon code

reed solomon code

×

×

errors

divide into 4 blocks every 4 bits

encode

correct 2 error blocks

Reed Solomon Code
  • 4bit (8, 4) RS code

available in the network with knowing packet loss rate

proposal of system 1 of 4

little packet loss

little packet loss

little packet loss

much

packet loss

Do not

modify applications

Proposed System

Proposal of System [1 of 4]
  • Provide Gateways

Existing System

proposal of system 2 of 4

RS code/UDP

HTTP/TCP

HTTP/TCP

HTTP/TCP

HTTP/TCP

RS decoding

RS code/UDP

RS encoding

UDP→TCP

TCP→UDP

HTTP/TCP

HTTP/TCP

HTTP/TCP

RS decoding

UDP→TCP

Proposal of System [2 of 4]
  • The Stream of Sound Data
proposal of system 3 of 4
Proposal of System [3 of 4]
  • RS encoding and division into packets
proposal of system 4 of 4
Proposal of System [4 of 4]
  • Packet Format
    • block number
      • position of the packet
    • number in a block
      • position of the packet in a block
    • real data size
      • date size of a block brefore encoding(generally 4096 bytes)
evaluation 1 of 5
Evaluation [1 of 5]
  • Compare the communication quality in the proposed model with the existing model
    • Interruption and Noise
    • Connect-able Time
evaluation 2 of 5

mesure connect-able time

listen to

noise or interruption

Evaluation [2 of 5]
  • Evaluating environment
    • server ・・・ Internet Radio Station FOR (in IPU)
    • router ・・・ 20
    • MP3 bitrate ・・・ 32kbps
    • Reed Solomon code ・・・ 8 bits (32, 16) RS
    • packet loss rate ・・・ unknown
evaluation 3 of 5

less interruption and noise

Evaluation [3 of 5]
  • Interruption and Noise

experimental time : 300 seconds

evaluation 4 of 5

more difficult to disconnect

Evaluation [4 of 5]
  • Connect-able Time(connection between client and relay server)
    • Existing model
      • 5 minutes at the worst
    • proposed model
      • never disconnect (300 minutes)
evaluation 5 of 5
Evaluation [5 of 5]
  • Interruption and Noise
    • decreased
  • Connect-able Time
    • increased

Communication quality improved in the real network

without knowing packet loss rate.

future work
Future Work
  • Value-added services provided between a server and relay servers
    • bitrate conversion for bandwidth constraint environment (ex. PHS, mobile user)
    • different Commercial Message for each relay server

Value-added Servive

summary
Summary
  • The issue of Interruption and Noise
  • UDP and Reed Solomon code
  • Provided gateways using Reed Solomon code into the existing system.
    • Not modify the existing applications.
  • The communication quality improved in the proposed system than the existing system
    • In the real network without knowing packet loss rate