simply cooperative
DESCRIPTION
SIMPLY COOPERATIVE. Anthony Ephremides Pompeu Fabra University April 29, 2010 Barcelona, Catalunia. THE “COAT OF ARMS”. S : source. D : destination. THE “COAT OF ARMS”. R : relay. S : source. D : destination. THE “COAT OF ARMS”. l 2. R : relay and source. l 1. S : source. - PowerPoint PPT PresentationTRANSCRIPT
SIMPLY COOPERATIVE
Anthony Ephremides
Pompeu Fabra University
April 29, 2010
Barcelona, Catalunia1
THE “COAT OF ARMS”
S: source D: destination
2
THE “COAT OF ARMS”
R: relay
S: source D: destination
3
THE “COAT OF ARMS”
R: relay and source
S: source D: destination
4
THE “COAT OF ARMS”
R: relay and source
S: source D: destination
“ether” medium
5
THE “HISTORY”
6
THE “HISTORY”− “RELAY” CHANNEL (Van der Meulen ’60’s)
Key differencesNo “source” traffic from RNo “ether”Classical information-theoretic quest for capacity – backlogged S
reservoir
S D
R
7
THE “HISTORY”− “RELAY” CHANNEL (Van der Meulen ’60’s)
Key differencesNo “source” traffic from RNo “ether”Classical information-theoretic quest for capacity – backlogged S
− “REVISED” RELAY CHANNEL (wireless) − Laneman/Tse/Wornell
− Sendonaris /Erkip/Aazhang− Kramer/ Gastpar/Gupta− Kramer/Maric/Yates
Basic idea: Cooperative Diversity (variety of schemes) Objective: Again, Capacity (backlogged S)
(
)
reservoir
S D
R
8
……………………
A “WIRELESS” NETWORK PERSPECTIVE
9
A “WIRELESS” NETWORK PERSPECTIVE
• “PACKETS” THROUGHPUT
10
A “WIRELESS” NETWORK PERSPECTIVE
• “PACKETS” THROUGHPUT
• “BURSTY TRAFFIC” DELAY
11
A “WIRELESS” NETWORK PERSPECTIVE
• “PACKETS” THROUGHPUT
• “BURSTY TRAFFIC” DELAY
− STABLE THROUGHPUT
12
A “WIRELESS” NETWORK PERSPECTIVE
• “PACKETS” THROUGHPUT
• “BURSTY TRAFFIC” DELAY
− STABLE THROUGHPUT− COGNITION (sensing)
13
A “WIRELESS” NETWORK PERSPECTIVE
• “PACKETS” THROUGHPUT
• “BURSTY TRAFFIC” DELAY
− STABLE THROUGHPUT− COGNITION (sensing)
Q: CAN’T WE STILL CO-OPERATE?
14
DIGRESSION: THE VIRTUE OF THE SINGLE QUEUE
(STATISTICAL MULTIPLEXING)or
1
2
M
D
1+2+…+M
DS
S1
S2
SM
15
“VIRTUAL” QUEUE
THE “PRIMITIVE” IDEA (Sadek, Liu, Ephremides 2007)
1
2
M
i
Relay
Source Terminals
Destination
S1
S2
Si
SM
R D
• NO CONTENTION (e.g. TDMA)
• PERFECT CHANNEL SENSING
• INSTANT ERROR-FREE “ACKs”
• SINR > • FADING CHANNELS (i.e. packet erasure
channels)
0
2||Pr
N
PhP ab
ab
16
hid
hir
hrd
17
COOPERATION METHOD 1• Each terminal transmits HOL packet in its assigned slot (if empty,
slot is free)
• If D receives successfully, it sends ACK (heard by both the relay and the user)
• If D does not succeed but R does: at first sensed empty slot R transmits to D the failed packet
• If neither D nor R succeed, packet gets retransmitted by the terminal in next frame
• Relay does not keep packets after the end of the frame
1. Relay has always a finite queue (M packets Max)
2. Terminal queues “interact”
Remarks:
Idle slots are utilized!
18
COOPERATION METHOD 2• Each terminal transmits HOL packet in its assigned slot (if empty,
slot is free)
• If D receives successfully, it sends ACK (heard by both the relay and the user)
• If D does not succeed but R does: at first sensed empty slot R transmits to D the failed packet
• If neither D nor R succeed, packet gets retransmitted by the terminal at next opportunity
• Relay keeps all packets it receives correctly
1. Relay has a possibly growing queue
2. Terminal queues do not interact
Remarks:
Again: Idle slots are utilized!
THE CRITERION STABLE THROUGHPUT:
arrival rate service rate
Q(t): queue size at time t
0)(Prlim NtNtQ ~ “positive recurrence”
Loynes: If arrival process and service process are jointly stationary,
the queue is stable iff <
max stable throughput
19
THE CRITERION (cont.)1
2
Q1(t)
Q2(t)
service
Problem: When Q1(t) and Q2(t) “interact”, stationary “service rate” cannot be identified.
Solution: STOCHASTIC DOMINANCE (Rao, Ephremides 1988)
Set of ’s such that Q1 and Q2 are stable
λ
1
2
Q1
Q2
1 1 1
1 1 1
1 1 1
2
2
2
2 2
2 2
2 2
1 1 1
1 1 1
2 2
2 2
1' 1' 1'2'
2'
2'
1 '≠ 1
2 '≠ 2
20
BACK TO THE “PRIMITIVE” SYSTEM• COOP METHOD 1• COOP METHOD 2• RANDOM ACCESS• TDMA• SELECTIVE “DECODE-AND-FORWARD” ---NETWORK VIEW
EVERY PACKETUSES TWO SLOTS
OR
EVERY PACKETUSES TWO “HALF-SLOTS”AS TWICE THE RATE
i.e.
21
nocooperation
BACK TO THE “PRIMITIVE” SYSTEM• COOP METHOD 1• COOP METHOD 2• RANDOM ACCESS• TDMA• SELECTIVE “DECODE-AND-FORWARD” ---NETWORK VIEW
EVERY PACKETUSES TWO SLOTS
OR
EVERY PACKETUSES TWO “HALF-SLOTS”AS TWICE THE RATE
i.e.
attention22
nocooperation
23
RESULT FOR 2-USERS
Comparison
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
1
2TDMA
COOP2DF
ALOHA
COOP1
24
DF: Relay transmits at the same rate and utilizes two time slots.
DF: Relay transmits at twice the rate and utilizes one time slots. (Rate and SNR-threshold are related through the Gaussian mutual information formula.
0 5 10 15 20 25 30 350
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
SNR Thresold () [dB]
Aggr
egat
e M
axim
um S
tabl
e Th
roug
hpt
TDMA=COOP1COOP2DFALOHA
1 2 3 4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
R [b/s/Hz]
Aggr
egat
e M
ax S
tabl
e Th
roug
hput
TDMACOOP2DFALOHA
25
DELAY• Notoriously difficult for interacting queues• Symmetric System: 2-users
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.410 0
10 1
10 2
10 3
10 4
10 5
1
Aver
age
Dela
y
TDMACOOP1COOP2DF
ALOHA
WHY?VIRTUE OF THE SINGLE QUEUE
1
2
M
D
S1
S2
SM
PARTIAL CONCENTRATION INTO SINGLE QUEUEIN METHOD 2
R
26
BUTS1
DS2
SM
R
27
BUTS1
DS2
SM
R DS2
SM
S1
28
BUTS1
DS2
SM
R DS2
SM
S1
1 N2 D =(N+1)
piNpND
ANY TERMINAL COULD PLAY THE ROLE OF THE RELAY
Pij: Packet success probability from i to j (increasing in i, decreasing in j, for i < j)
or, simply (PiD increasing in i)
TANDEM IS BORN piD
29
i
HENCE, BACK TO THE ‘COAT OF ARMS”
NEW ISSUE:
ACCESS POLICY:
PRIORITY ORDER IN SERVING QUEUES AT “2”− AFFECTS DELAY (NOT THROUGHPUT)
−“ANY” CONFLICT-FREE “WORK-CONSERVING”−TDMA (MAXIMUM STABLE THROUGHPUT REGION: SAME)−RANDOM OR SCHEDULED ACCESS WITH MULTIPACKET RECEPTION (B. Rong, A. Ephremides 2009)
1
2
1
2
3=D
p12
p13
p23
30
STABLE THROUGHPUT REGION
31
• Both policies yield same stable throughput regions under cooperation
• N users simultaneously increase stable throughput rates
• kmax1 ≤ k ≤ N-1
max
• p1,2 increases region increases
85.0,6.0,4.0,8.0,3.0 2,13,23,1 ppp
LESSON TAUGHT− GAIN BY ALL USERS BECOMES
MOTIVATION FOR COOPERATION
32
LESSON TAUGHT− GAIN BY ALL USERS BECOMES
MOTIVATION FOR COOPERATION or
− IT IS IN THE INTEREST OF THE RICH TO HELP THE POOR
33
LESSON TAUGHT− GAIN BY ALL USERS BECOMES
MOTIVATION FOR COOPERATION or
− IT IS IN THE INTEREST OF THE RICH TO HELP THE POOR
Deeper and Far-reaching Interpretation:FOR BURSTY TRAFFIC IN SHARED CHANNELS, REDUCTION OF THE PRESENCE OF COMPETITION IS BENEFICIAL
34
SEQUEL• STABLE THROUGHPUT REGION
“BACKLOGGED” THROUGHPUT REGION
35
(FOR SCHEDULED ACCESS AND PRIORITY TO “NOT-TO-RELAY”)
− COMMON PHENOMENON
• FOR RANDOM ACCESS (q1,q2) ON COLLISION CHANNEL, COOPERATION MAY HELP
IF
vs
2231312
1313122313
1
)1(
ppp
ppppp
TS
NCS
COOPS
(B. Rong, A. Ephremides ISIT 2009)
S
T
MULTI-PACKET RECEPTION CAPABILITY
• CRITERION: SINR > (simplest)• NEW SET OF SUCCESS PROBABILITIES• NO SIMULTANEOUS “TRANSMIT” AND “RECEIVE” BY R (initially)• PSR AS BEFORE• PRD > PRD/S new
PSD > PSD/R new
and of course PRD > PSD (Denote these probabilities by )
• R KNOWS WHETHER QS=0
36
(B. Rong, A. Ephremides 2009)
COOPERATION POLICY: I. R MIXES OWN AND S’s PACKETSII. IF QS=0, R TRANSMITS w.p. 1 (IF QR>0)III.IF QS>0, S TRANSMITS w.p. 1 AND R w.p. q (IF QR>0)
p
“Standard” channel(J. Luo & A. Ephremides 2006)
R
S D
RESULT (MPR)
A REGION OF VALUES OF THE PACKET
SUCCESS PROBABILITIES, ,SUCH THAT
① IF
② IF for q=0
37
Λ
Λp NCS
COOPS
Λp NCS
COOPS
for suitable values of q
(i.e., scheduled transmission or “conventional” cooperation )
RESULT (cont.)
38
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.450
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1 [packets/slot]
2 [pac
kets
/slo
t]
NC
CC, C-OPP
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.450
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1 [packets/slot]
2 [pac
kets
/slo
t]
NC
CC
C-OPP
If , opportunistic scheme results in improved stability region
If , the optimal strategy is the conventional cognitive cooperation
Resulting stability regions
Λp Λp
--- AND MORE• SIMILAR RESULTS FOR FULL TANDEM (MORE
THAN TWO SOURCE TERMINALS)
• ENHANCEMENT WITH PHYSICAL-LAYER IMPROVEMENTS– COMBINE WITH DYNAMIC DECODE-AND-FORWARD
(K. Azarian, H. El Gamal, P. Schniter 2005)
– COMBINE WITH ADAPTIVE SUPERPOSITION CODING
(T. Cover 1972)
39
(B.Rong, I. Krikidis, A. Ephremides 2009)
RESULT
40
NC: no cooperation CC: conventional cooperationS-CC: conventional cooperation with superposition codingNC-DDF: non-cognitive DDF C-DDF: cognitive DDFSC-DDF: cognitive DDF with superposition coding
WHAT ABOUT NETWORK CODING?
41
S
R
1
2
D
QR1
QR2
transmits random linear combinations of contents of QR1 , QR2 (packet-by-packet)
−NO IMPROVEMENT
--BUT: (i) IF THERE ARE MULTIPLE DESTINATIONS AND / OR (ii) CONTENTS OF BUFFERS ARE COMBINED IN THEIR ENTIRETY
− POSSIBLE IMPROVEMENT (under investigation)
R:
CONCLUSION− RELAY-BASED COOPERATION AT THE
PACKET LEVEL CAN BE BENEFICIAL FOR DIFFERENT REASONS (NOT DIVERSITY-RELATED)
42
CONCLUSION− RELAY-BASED COOPERATION AT THE
PACKET LEVEL CAN BE BENEFICIAL FOR DIFFERENT REASONS (NOT DIVERSITY-RELATED)
43
SIMPLY COOPERATIVE
−TERMINALS CAN BE