DSpace at VNU: Exact outage analysis of underlay cooperative cognitive networks with maximum transmit-and-interference power constraints and erroneous channel information

TRANSACTIONS ON EMERGING TELECOMMUNICATIONS TECHNOLOGIES
Trans. Emerging Tel. Tech. (2013)
Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ett.2719

RESEARCH ARTICLE

Exact outage analysis of underlay cooperative
cognitive networks with maximum
transmit-and-interference power constraints and
erroneous channel information
Khuong Ho-Van*
HoChiMinh City University of Technology, 268 Ly Thuong Kiet street, District 10, HoChiMinh City, Vietnam

ABSTRACT
This paper presents exact analysis of interference probability and outage probability of underlay cooperative cognitive networks under quite general conditions such as imperfect channel information, maximum transmit-and-interference power
constraints, correlation among received signal-to-noise ratios and non identically distributed fading channels. In addition,
asymptotic outage analysis at either large maximum transmit power or large maximum interference power is proposed
to have useful insights into performance limits of underlay cooperative cognitive networks. Analytical results reveal that
underlay cooperative cognitive networks dramatically suffer outage saturation phenomenon, and saturation degree significantly depends on channel estimation quality. Moreover, the performance of both licenced network in terms of interference
probability and unlicenced network in terms of outage probability is considerably deteriorated by channel estimation
error. Furthermore, optimum relay position is dependent of several factors such as maximum transmit power, maximum
interference power, licensee position and channel estimation quality. Copyright © 2013 John Wiley & Sons, Ltd.
*Correspondence
Khuong Ho-Van, HoChiMinh City University of Technology, 268 Ly Thuong Kiet street, District 10, HoChiMinh City, Vietnam.
E-mail:
Received 28 June 2013; Revised 11 August 2013; Accepted 4 September 2013

1. INTRODUCTION
Underlay decode-and-forward (DF* ) cooperative† cognitive network is a feasible-and-efficient solution to problems of spectrum scarcity, spectrum under-utilisation
and coverage extension [1–4]. For system design optimization such as power allocation optimization, channel
information must be available. However, it is almost

impossibly expected to have full knowledge of channel
information from existing channel estimation algorithms.
As such, the investigation on the impact of imperfect
channel information on the system performance is necessary. On the other hand, outage probability is a useful
metric in providing insights into the information-theoretic

* Popularly, the relay in most cooperative relaying schemes operates in
either DF or amplify-and-forward type [33, 34].
†
Multi-hop communication (e.g. [2], [6]) differs from cooperative
relaying (e.g. [7, 8]) in that the former bypasses the direct channel between the source and the destination while for enhanced space
diversity, the latter does.

Copyright © 2013 John Wiley & Sons, Ltd.

performance limit [5]. As a result, a general outage
analysis framework for underlay DF cooperative cognitive networks, accounting for multiple practical operation
conditions such as imperfect channel information on all
channels, two maximum transmit-and-interference power
constraints, non-identically distributed (i.d.) fading channels and the correlation among received signal-to-noise
ratios (SNRs) is urgent and essential. Nevertheless, current
publications have not considered all these conditions concurrently. For instances, the authors in [2–4, 6–8], [9–32]
partially investigated them.
More specifically, the authors in [3, 7, 8], [16–20],
[22–25] analysed the outage performance of underlay DF
cooperative cognitive networks‡ in different aspects under
the assumption of perfect channel information: (i) about

‡

This paper studies underlay DF cooperative cognitive networks, and
hence, the works on other modes (e.g. the interweave mode in [31]),
error probability analysis (e.g. [4], [27–30]), the amplify-and-forward
type (e.g. [14, 32]), and multi-hop communications (e.g. [2,Â
à s N v Â
Ã
r
F1 0
tF 1
2IT
1
SL
2Pt
1C
e
I0
2
rF 1
.1
ÁO SL ÁSL
SL / Pt

2

0s

1
.N
s
C

r/
N
I
T
4e
A
F2 D e
Q@
2Pt
0s
1
s
.sF 2 C rF 2 / N0 v A
tF 2 @ .sF 2 rF 2 / N0 v
Q
;
C
rF 2
2Pt
2Pt
Â
à s N v Â
Ã
F2 0
tF 2
1
IT p 2
2Pt
1C
e

I0
sN
rN 2
2
rF 2
2Pt
˛SR ˇSR v

(72)

˛SR N0 v
Pt

Trans. Emerging Tel. Tech. (2013) © 2013 John Wiley & Sons, Ltd.
DOI: 10.1002/ett

.Ns

r/
N IT
;
2Pt

(73)

s

(74)

K. Ho-Van

Meanwhile, with the aid of [45, Equation (24)], the F3
term is represented in closed form as
F3 D

2Q .uF 3 ; vF 3 /
sF 3
˛SR N0 v
sI
N
C 2PT
Pt
t

e

sF 3
2IT

Â
I0
where
IT
sF 3 D
N0 v

sÂ

Á

(75)
r

SL / Pt

.1

˛SR N0 v
sN
C
IT
2

Ã2

SL

Ã

ÁO SL ÁSL

4

SL .ÁO SL ÁSL /
2
.1
SL /

1

(76)

s
uF 3 D
s
vF 3 D

N0 v
Pt
N0 v
Pt

Â

Ã

˛SR C

sN IT
2N0 v

˛SR C

sN IT
C sF 3
2N0 v

Â

sF 3

(77)

Ã
(78)

By plugging Equations (60), (65) and (66) into Equation
(59), one achieves the closed form of W.

ACKNOWLEDGEMENTS
This research is funded by Vietnam National Foundation
for Science and Technology Development (NAFOSTED)
under grant number 102.04-2012.39

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