Energy-Efficient and Trust-aware Cooperation in Cognitive Radio - - PowerPoint PPT Presentation
Energy-Efficient and Trust-aware Cooperation in Cognitive Radio Networks Networks Ning Zhang Department of Electrical and Computer Engineering U i University of Waterloo i f W l 1 Outline Outline Introduction Introduction
Ning Zhang Department of Electrical and Computer Engineering U i i f W l University of Waterloo
1
Introduction
Motivation and objectives
– Trust values Stackelberg game – Stackelberg game
2
S i – Spectrum scarcity – Cognitive radio [1] primary users (PU) and secondary users (SU) – Spectrum holes
( l i h f di h d i ) – Inaccurate (multipath fading, shadowing) – Energy consumption – Dynamic
– Cooperative sensing (Cooperation among SUs) p g ( p g ) – Cooperation between PU and SU
[1] S. Haykin, Cognitive radio: brain‐empowered wireless communications, IEEE Journal on Selected Areas in Communications 23 (2) (2005) 201–220.
3
In [2], the PU gives its licensed bandwidth for a fraction of the transmission time to a subset of secondary transmitters in exchange for cooperation to increase its transmission rate.
where the PU selects some appropriate SUs as cooperative relays to increase its transmission rate and revenue. In return, an interval of time is gi en to the selected secondar rela s as a re ard given to the selected secondary relays as a reward.
transmits its signal in the first phase which is overheard by the SU Then transmits its signal in the first phase, which is overheard by the SU. Then the SU decodes and superimposes the PU’s signal with its own signal using a different power level to broadcast.
[2] O. Simeone. et al, “Spectrum leasing to cooperating secondary ad hoc networks,” Selected Areas in Communications, IEEE Journal on, 2008 4 [3] J. Zhang and Q. Zhang, “Stackelberg game for utility-based cooperative cognitive radio networks,” in Proceedings of the tenth ACM international symposium on Mobile ad hoc networking and computing. ACM, 2009. [4] Y. Han et al, “Cooperative decode-and-forward relaying for secondary spectrum access,” Wireless Communications,IEEE Transactions on, 2009.
All previous works assume that SUs are trustworthy and well behaved which All previous works assume that SUs are trustworthy and well-behaved, which may not be always true in reality. There may exist some dishonest users, even malicious ones in the system, corrupting or disrupting the normal operation of Cooperative CRN. p
Since the PU can transmit its data at any time, it may have an incentive to Since the PU can transmit its data at any time, it may have an incentive to cooperate for energy saving due to power limitation.
Motivation: We make an effort to guarantee and improve the performance of cooperation and SU selection, considering energy efficiency and security issues.
We try to answer the following questions: when to cooperate with whom to cooperate and how to cooperate ? when to cooperate, with whom to cooperate and how to cooperate ?
5
– PU communicates with the base station (BS) in TDMA mode. – The time slot duration for each PU’s transmission is T.
– Ad hoc network Ad hoc network
– Three-phase cooperation and Amplify-and-Forward (AF)
6
(a) Primary transmission (b) Cooperative transmission (c) Secondary transmission
Ch l d l d i d d l G i d – Channels are modeled as independent complex Gaussian random variables, constant within each slot, but generally varying over the slots. – A common control channel is assumed for exchanging information g g among PU, SU and BS. – There exist a trusted center keeping the trust values.
When a malicious SU is selected to cooperate with the PU it may – When a malicious SU is selected to cooperate with the PU, it may misbehave, e.g., it may drop PU’s data ,etc. – A dishonest SU may not obey the cooperation rule during the cooperative transmission to pursue more self-benefits. – Moreover, considering the mobility of SUs, the malicious or dishonest SUs may misbehave at one place then move to other places SUs may misbehave at one place then move to other places.
7
the channel gain between the PU and the BS; the channel gain between the PU and SUi; h h l i b SUi d h BS
pb
h
i ps
h
the channel gain between SUi and the BS; the channel gain between SUi and its corresponding receiver. transmit power of PU without cooperation
i sb
h
i s
h P
transmit power of PU without cooperation. transmit power of PU with cooperation. transmit power of SU in cooperative and secondary transmission 1
i s
P
c
P
d
P
the one-sided power spectral density of the independent additive white Gaussian noise at the both base station and secondary receivers.
N
1 This rule is enforced in order to ensure that the secondary users spend for cooperation at least the same power that they are willing to spend for their own transmission.
8
– Each SU will behave well with probability p, and misbehave with probability (1-p) – Posteriori probability estimate of the above binary events can be represented as beta distributions.
p ˆ
– let be the observed number of good behaviours.
v
– let be the observed number of misbehaviours.
) 1 ( ) 1 (
) ˆ 1 ( ˆ ) 1 ( ) 1 ( ) 2 ( ) , | ˆ (
l k
p p v v l k p f
) 1 ( ) 1 ( v
i
Tr
2 1 ) ˆ ( v p E
Beta function of event after 7 observations of good behaviors and 1 observation of misbehaviors.
9
b d it h th i ht t d id th t ( i d P ) t band, it has the right to decide the parameters ( i, and Pc) so as to maximize its own utility in terms of energy efficiency.
maximize the transmission rate without spending too much energy.
Leader: PU i and Pc
Leader: PU i , and Pc Follower: SU transmission power
10
Without cooperation, the primary user’s direct transmission rate
) 1 ( log
2
h P W R
pb d
Through cooperation with SUi the achievable cooperative rate [5]
) 1 ( log
2
N W Rd (1)
Through cooperation with SUi, the achievable cooperative rate
)] , ( 1 [ log 2
2 2 2 2 i sb i s i ps i c pb i c i i c
h P h P f N h P W a R (2)
2 2 2 2 2 2
1 ) , ( N h P h P h P h P N h P h P f
i sb i s i ps i c i sb i s i ps i c i sb i s i ps i c
(2)
In order to maintain PU’s transmission rate:
d c
R R
11
[5] J. Laneman, D. Tse, and G. Wornell, “Cooperative diversity in wireless networks: Efficient protocols and outage behavior,” Information Theory, IEEE Transactions on, 2004
The PU uses to transmit for a period of . Energy consumption is
d
P
T
T P
d
The PU cooperates with SUi , it uses to transmit for a period of . Th i i
i c
P
T a
i
2 T ai
The energy consumption is
reduction and the total power dissipation without cooperation:
2 T a P
i i c
p p p
2 1 2 1 2
i i d i c i d i i c d i
a P P a T P T a P T P
d i i c
P P
, PU chooses cooperation with SUi PU doesn’t choose cooperation with SUi
i
i c
P
d
P
1
i
1
, PU doesn t choose cooperation with SUi
1
i
) 1 (
i i i
a Tr U Expected energy saving ) 2 1 (
i p
Tr U
12
Expected energy saving
being aware of the parameters of primary user .
) , (
i i
a
corresponding receiver is given by
i s
R
i
SU
) 1 ( log ) 1 ( ) , (
2 2
N h P W a a R
i s i s i i i i s
transmission energy .
T a P c
i i s
) 2 1 (
2
T a P c N h P W a a U
i i s i s i s i i i i s
) 2 1 ( ) 1 ( log ) 1 ( ) , (
2 2
13
and how it cooperates with this SUi (time allocation coefficient and power allocation coefficient ) to maximize its utility.
i
a
i
a ) 2 1 ( max
, , i i i i p a i
a Tr U
i i
) 1 ( log )] ( 1 [ log
2 2 2 2
h P W h P h P f h P W a
pb d i i i i pb i c i
t s
) 1 ( log )] , ( 1 [ log 2
2 2
N W h P h P f N
sb s ps c
. .t s
p i i i
S SU a , 1 , 1
i p a i i i
U b a i
i i
, , * * *
max arg , ,
14
Given , selects the transmission power to maximize its own utility,
i i
a ,
i
SU
, p y, which can be formulated as the following optimization problem
i i
a ,
i
SU
T a P c N h P W a a U
i i s i s i s i i i i s Pi
s
) 2 1 ( ) 1 ( log ) 1 ( ) , ( max
2 2
i max
P Pi
s
} , ) 1 ( min{
max 2
P N W a P
i i s
. .t s
} , 2 ln ) 2 1 ( {
max 2
h a c
i s i s
15
– Normalizing the distance between PU and BS, the SU is approximately placed at the distance from the PU and 1-d from the BS
) 1 ( d
placed at the distance from the PU and 1-d from the BS. – The channel gains can be calculated based on a simple path loss model.
) 1 , ( d
We choose the path loss coefficient to be 2.
16
a smaller power than Pd through cooperation . (2) and turn to be optimal when reaches its maximum value.
tend to increase with the distance d
a
* *
a
(2) A better channel gain between the SU and its corresponding receiver comes with a better energy saving of the PU and a wider
, a
gy g cooperation range
17 Fig 1 Fig 2
p p p , g energy efficiency of the PU and trustworthiness of SUs. f l h d f d i i ki S k lb
The analysis of the game provides the PU with the best strategy for partner selection, spectrum access time allocation and transmission power determination.
PU can obtain high energy saving through the cooperation by selecting the g gy g g p y g most suitable SU.
18
Misbehavior detection in a fading environment.
Decode-and-Forward cooperative mode Distributed beamformming or Space-Time coding
We have not considered the whole signaling procedure including signaling We have not considered the whole signaling procedure, including signaling exchange for the SU selection and evaluation.
19
20