a channel self-organizing protocol for multi-cell plc networks · sharing transmission capacity (2)...

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A Channel Self-Organizing Protocol for Multi-Cell PLC Networks

Le Phu DoITG-FG-5.2, 07 Oct. 2010


2Contents

• PLC Networks with Multi-Cell Structure

• Sharing Transmission Capacity between Multiple PLC Cells

• Realization of Channels

• Solution Proposal– Communication between Cells– Algorithm Description– Example Results

• Conclusions

Broadband-PLC Network

Low voltage power supply network

High or medium voltage

PLC access network

In house network

Telecommunication backbone network

BS

RP

CB

Transformer station

Base station

Repeater

Cable box

BS

RP

CB

data signal line

power supply line

3


Multi-Cell PLC Access Network Examples

• LV: Low Voltage

• MV: Medium Voltage

• HV: High Voltage

MV/LVMV/LVMV/LVMV/LV

LV LV LV LV

MV/LV Subst.

MV/LV Subst.

MV/LV Subst.

MV/LV Subst.

Backbone

The different colors indicate traffic coming from different LV PLC cells. MV/LVMV/LVMV/LVMV/LV

LV LV LV LV

HV/MV

MV/LV Subst.

MV/LV Subst.

MV/LV Subst.

MV/LV Subst.

MV/LV

LVHV/MV

MV/LV Subst.

MV/LV

LV

MV/LV Subst.

MV/LVMV/LV

LV LV

MV/LV Subst.

MV/LV Subst.

Backbone

Source: OPERA

4


Transmission Capacity and Coexistence

21 22 23

24 25

5

6 46 47 48

43 44 45

739 40 41 42

• Interference: In-Line and In-Space

• The Inter Phy Protocol (IPP)*: Idear: Detection of the neighbor cells by listening to the beacon signal from the neighbors

Sys.1

Sys.2

Sys.1

Time frame t

Control Beacon period

* Specified in the IEEE P1901

5



6Organization of Channels

F

t


CH1

CH2

CH3

CH4

…

… CHF

CHF-1CH1

CH2

…

…

time frame (TF)

• A Resource Unit (Channel-CH) is configured as– Time Slot and

Frequency Band

• Dynamic reservation/ allocation of channels to each cell based on its number of active users

• To be investigated – Channel Reuse: to improve possible transmission capacity

– Fairness: same reservation resource per active users, in different cells


7Objectives

• Sharing available transmission resource by all cells

• Maximizing the channel reuse: maximizing the transmission capacity of the network

• Fairness between active users in the cells: Same P for all cells

• Calculation of P: Number of allocated channels per number of active users:

i Ci iP B N=

Ni: =1 if no active user, =number of active users otherwise

BCi: Number of allocated channels in cell Ci


8Sharing Transmission Capacity

• Static Distribution: Each cell is allocated a fixed amount of channels– User changes status (active/idle/off) dynamically -> may be unfair

between users in different cells

CH1, CH2

CH3, CH4

CH1, CH2

CH1,

CH2

Sharing Transmission Capacity (2)

• Dynamic Distribution: Channels of each cell will be varied according to the resource requirement– Centralized (like in the GSM system)

• Global control of the total capacity, need a control center

• Require resources for transmission between the control center and the HEs

– Distributed• Require communication between neighbor

cells

• Sharing the channel status with neighbors– Cell informs its status to its neighbors (in

beacon period)

– Processing received information to allow “moving” channels between cells

CH1, CH2

CH3, CH4

CH1

CH5

9


10Between Cells Communication Issues

• Common Slot and Collision– One slot is reserved for inter-cell communications (in beacon period)

• Format– Regular broadcast the “channel announce” message (CA-Msg)

• Random transmission protocol– No collision detection mechanism

• Effect of collision

ID #D List_Ch (fi)

CA CA

TTF

t


AC

Traffic demand: #Active Users

AC: 1 Byte: Access or InHomeID: 6 Byte: Address of the Master#D: 1 Byte: ‚ of active usersList_Ch(fi): 2 bit for a channel• 0: Channel is free• 1: occupied by this cell• 2: used by one neighbor cell• 3: used by more than one neighbor cells

(length of a CA-Msg is 18 Byte for 80 channels)


11Communication Between Cells

• Broadcasting of the CA-Msgs– Can be carried out by border nodes

• Sending of the CA-Msgs: – Randomly select a Beacon TS– No ACK

CPEHE

HE

RP

CPE 1

RP

CPE 3CPE 2

CPE4

Cell 3

Cell 1Cell 4

Cell 2

Transmission in downlink

Transmission in beacon period

Transmission in uplink

HE: Head endRP: RepeaterCPE: Customer Premise

Equipment

Cell 1 Cell 2

Send status

make decision

on channels,

send status

Make decision on channels

CA-Msg

CA-Msg

Between Cells Communication Issues

Cj

11

send ( i )j

i

pH

=+

• Probability to select a slot (1 neighbor has Hi neighbors)

1 11( j )

i

sendj

Cj i

pH H

= ⋅+∑

• Probability to select a slot

Ci

Cin

Cim

Ci2

Ci2n

Ci2m

Ci3Ci3n

Ci3m

12



13Master Station: Decision on Channels

• Two objectives⇒Two procedures– Maximizing the number of

channels allocated in all cells⇒ Seize Channels

– Same P – fairness (in different cells)

⇒ Release Channels

High-P

Low-P

Equil

P>min{PNB} “release”

P<min{PNB}“seize”

Transmit CA-Msg

Receive CA-Msg

Remove interferences

PNB: P of neighbor

i j

i

C j C iC

i j

B N B NB

N N−

−⎢ ⎥= ⎢ ⎥

+⎢ ⎥⎣ ⎦

Cj: neighbor of Ci , which has lowest P


14An Example with the Procedures

• Channel seize– Combine channel in use by

its neighbors– seize the “unused” channel

• Channel release– Compare channel/demand

with neighbor (Cj) which has lowest channel/demand

– Find number of channels has to be released: can be obtained by Cj

• Not used by neighbors (except this cell) of Cj

• Validity of channel information

– Each channel announce message has a limit validity – time out

CH1 CH2 Ch3 Ch4 Ch5 Ch6

C1

C3

Used

C2 2 3 2 1 3 3

CH1 CH2 Ch3 Ch4 Ch5 Ch6

C1

C2 2 3 2 1 3 3

Ne(C2)

C1 Rel.

C1

C1

C2 1 3 1 1 3 3

C3

C2 C3C1

Sys.

C2

C1

Sys.


15Evaluation Metrics

Given: Set of channels: F={1,..,F} , Set of cells: C={1,..,S}, Cell Ci contains Ni active users, Same traffic demand from each active user

Channel status:• Channel usage vector in each Master (Head end-HE): ChCi=(ai,1, ai,2, ai,3, … ai,F)

where ai,f=1: Ci uses channel f, ai,f=0: otherwiseTo be evaluated:• Channel reuse factor:

• Number of allocated channels

• Fairness index: –– 1: perfect, greater is better

• Interferences

,1 1 1

S S F

All Ci i fi i f

B B a= = =

= =∑ ∑∑

AllCR

BfF

=

, , ,11 1

( · )S F S

All i f i j j fji f j i

I a i a=

= = ≠

= ∨∑∑

2

12

1

SCi

i iAll S

Ci

i i

BN

FBSN

=

=

⎛ ⎞⎜ ⎟⎝ ⎠=

⎛ ⎞⋅ ⎜ ⎟

⎝ ⎠

∑

∑

1 1AllFS ≤ ≤

Small Network for Analysis

• Two cells (Ci=2), are neighbors (ii,j=1)• F=80

• C2 with fixed number of users N2 = 9• C1 with increasing and decreasing

number of users over the time (every 100TF), between 1 and 9

•

Cell 1

Cell 21 2 0.5send sendp p= =

16


Small Network for AnalysisB C

1

#time frame (TTF)N

1#time frame (TTF)

Cha

nnel

-reu

se, f

CR

Fairn

ess,

F ALL

17


0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

1

2

3

4

5

6

7

8

9

10

11

12#Channels

#Users

0

0.5

1

1.5

2

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

1

2

Small Network for AnalysisB C

1

#time frame (TTF)N

1#time frame (TTF)

Cha

nnel

-reu

se, f

CR

Fairn

ess,

F ALL

18


0

10

20

30

40

50

60

1000 1200 1400 1600 1800 2000 0

1

2

3

4

5

6

7

8

9

10

11

12#Channels

#Users

0

0.5

1

1.5

2

1000 1200 1400 1600 1800 2000 0

1

2

Example Network

MV/LV

MV/LV

MV/LV

MV/LV

LV

HV/MV

MV/LV Subst.

MV/LV Subst.

MV/LV Subst.

MV/LV Subst.

MV/LV

HV/MV

MV/LV Subst.

MV/LV

MV/LV Subst.

Backbone

MV/LV

MV/LV Subst.

MV/LV

MV/LV Subst.

MV/LV

MV/LV Subst.

LV

LV

LV

LV

LV

LV

MV/LV

MV/LV Subst.

MV/LV

MV/LV Subst.

MV/LV

MV/LV Subst.

MV/LV

MV/LV Subst.LV

LV LV

LV LV

LV

Cell 1

Cell 2

Cell 3

Cell 4

Cell 5Cell

6Cell

7

Cell 8

Cell 9

Cell 10

• Ring of 10 cells• Interferences with two neighbors• 9 users/cell with on/off model: • On and Off phases Geo

– E{TON}= 100TF– E{TOFF}= 100TF

19


Simulation Results

0

0.5

1

1.5

2

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

1

2

3

4

5

6Fairness

Reuse

0

10

20

30

40

50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

1

2

3

4

5

6

7

8

9

10Num Channels

Num Users

Cell1

B C1

#time frame (TTF)

N1

#time frame (TTF)

Cha

nnel

-reu

se, f

CR

Fairn

ess,

F ALL

20


Simulation ResultsA

ver.

Cha

nnel

/use

r

Ave

r. U

ser/C

ell

E.g. If a channel can be used to transmit 1Mbps → Average speed/user ≈8.2Mbps

0

10

20

30

40

50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0

1

2

3

4

5

6

7

8

9

10Avg. Channels Per User

Avg. Users Per Cell

#time frame (TTF)

21


#cha

nnel

s

0

100

200

300

400

500

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

InterferenceEffective

#time frame (TTF)

#effective channels = #allocated channels - #interfering channels

Conclusions

• Model for dynamic channel allocation for Multi-Cell PLC supports for changing of traffic demands (user’s status)

• Allow channel self-organizing between cells with the distributed negotiation strategy: No need addition central control unit

• Required the realization of channel announce messages between neighbor cells

• Can be applied to Access PLC, In-Home PLC

22



23

Thank You!

Ref: L. P. Do, R. Lehnert, "Distributed Dynamic Resource Allocation for Multi-Cell PLC Networks", 13th IEEE International Symposium on Power-Line Communications and Its Applications (IEEE-ISPLC 2009), Dresden, Germany. 29 Mar-01 Apr. 2009.

a channel self-organizing protocol for multi-cell plc networks · sharing transmission capacity (2)...

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