AnkitSharma_IBFD_SelfBH_ICC2016

PERFORMANCE ANALYSIS OF FULL DUPLEX SELF-
BACKHAULING CELLULAR NETWORK
DEPT. OF ELECTRICAL ENGINEERING,
INDIAN INSTITUTE OF TECHNOLOGY, MADRAS
Ankit Sharma, Radhakrishna Ganti, Klutto MillethIIT-Madras, India

Agenda
IEEE ICC 2016 | Performance Analysis Of Full Duplex Self-Backhauling Cellular Network
• Broader Meaning
• In-Band Full Duplex communication
• Motivation – Use in Networks
• Proposed Sytem
• System Evaluation
• Results
• Conclusion
2

Title Breakup
In-Band Full Duplex, Small Cells, Self-Backhauling
 In-Band Full Duplex – refers to a device capable of transmitting and
receiving on the same channel, simultaneously
 Small Cells – refers to cells with smaller coverage/ Tx. Power overlaid with
macro cells
 Self-Backhauling – a cell backhauling itself over the wireless channel with
another cell that has an ideal backhaul to the core network
3

In-Band Full Duplex (IBFD)
Communication
Digital Coding &
Modulation DAC Baseband to Passband
Tx. Ant.
Digital Demodulation
& Decoding ADC Passband to Baseband
Rx. Ant.
Tx. Signal (~25dBm)
Rx. Signal(~-75dBm)
Isolation(~20dB)
Self-Interference(~5dBm)
Self-Interference ≈ Rx. Signal + 80 dB !!
4

Motivation – Why IBFD?
IBFD transceiver has been
demonstrated
A. Sachin Katti et al., “Practical, real-time,
full duplex wireless”
B. Sabharwal et al., “Full-duplex wireless
communications using off-the-shelf
radios: Feasibility and first results”
C. R Ganti et al., “A Linearization
Technique for Self-Interference
Cancellation in Full-Duplex Radios”
5
IBFD transceiver achieved! What next?
• IBFD radio design justified only if it helps
solve ‘NETWORK’ problems
• Several new use cases for such a radio
opening up with 5G
• We focus on a use of IBFD radio at
small cells
• Small cell self-backhauls itself with a
macro tier leveraging its IBFD
capability

System Picture
Proposed vs. Conventional
Core Network Core Network
IBFD!
Conventional Proposed
6

Proposed System
The use of FD radios to increase coverage/rates in cellular networks
1

System Setup
1. IBFD Self-
Backhaul
Spectrum Reuse
Vs.
Increased
interference
2. Interplay needs
MODEL !!
 Two-tier HetNet with macro BS (MBS) and operator deployed
pico BS (PBS)
 PBS backhauls itself with the MBS over the wireless channel
 As PBS is IBFD, backhaul carrier frequency from MBSPBS is
same as that of PBSUE
 Implication for Operators: (1) Get a free backhaul spectrum!
(2) Free from scourge of laying fiber for ultra-dense HetNets
 Results in increased spectral efficiency along with increased
interference
8

BW & Frequency Allocation
9
2W Hz
2W Hz
(η/n) W Hz
(1-η) W Hz
Given 2W Hz spectrum
 Entire 2W Hz used by PBS and MBS
 2W Hz  UL and DL of W Hz each
 At MBSs, W Hz further divided as ηW Hz
and (1 −η)W Hz, 0 ≤ η ≤ 1
 Each MBS backhauls n PBSs on an
average
 Each MBS to PBS link limited in BW to (η
/n)W Hz

Related Work
 S. Hong, J. Brand, J. Choi, M. Jain, J. Mehlman, S. Katti, and P. Levis,
“Applications of self-interference cancellation in 5G and beyond,”
Communications Magazine, IEEE, vol. 52, pp. 114–121, February 2014.
 B. Li and P. Liang, “Small cell in-band wireless backhaul in massive MIMO
systems: A cooperation of next-generation techniques,” CoRR, vol.
abs/1402.2603, 2014.
 I. Atzeni and M. Kountouris, “Full-duplex MIMO Small-Cell
Networks:Performance analysis,” arXiv preprint arXiv:1509.05506, 2015.
 S. Singh, M. Kulkarni, A. Ghosh, and J. Andrews, “Tractable model for rate
in self-backhauled millimeter wave cellular networks,” 2014.
10

System Evaluation
Evaluate FD Self-Backhauling architecture for performance metrics
2

System Model
 IBFD network is modeled by spatial Poisson point processes
 Two independent homogeneous PPPs Φm, Φs with density λm and λs
denote the MBS and PBS point processes respectively
 Macro and Small cells transmit with powers Pm and Ps
 Biases Bm and Bs associated with the macro and small cells
12

System Model (contd.)
 User-cell association based on max received biased power
 If closest MBS and PBS to typical user are at distances rm and rs,
then, user associates with PBS if,
αα −−
> |||| mmmsss rBPrBP
α
1
, 





=∆∆<
mm
ss
ms
BP
BP
rr
13

System Model (contd.)
 Fading is Rayleigh distributed between any two nodes
 Simple path loss model as |x|-α , α > 2
 SIR for a user located at origin and associated to PBS is thus,
where Is and Im denote the interference to typical user by all the other
PBSs and all MBSs
sm
sors
II
rhP
SIR s
+
=
−α
||
14

Anatyical Framework
Mathematical model for coverage and rate in the proposed FD architecture
2.1

Analytical Framework - Coverage
εm , εs: events of MBS, PBS association;
Tm, Ts, Tb: coverage SIR thresholds for user-MBS, user-PBS and PBS-
MBS links
]|,[].[]|[].[=[Coverage] ssmm εεεε bsmsusmum TSIRTSIRPPTSIRPPP >>+>
16

SIR – Macro Cell Association
O Small Cell
Macro Cell
ms rr '∆≡
mr'
1≥∆ )()(
'
)'( ^^
'
oIoI
rhP
rSIR
ms
morm
mum
m
+
=
−α
∑
∆Φ∈
−
=
c
ms roBz
ozss zhPoI
)',(
^
)(

α
∑
Φ∈
−
=
c
mm roBz
ozmm zhPoI
)',(
^
)(

α
17
*J. Andrews et al., “A tractable approach to coverage and rate in cellular networks“.

SIR – Small Cell Association
α
α
−
−
++
=
mormms
sors
msus
rhPoIoI
rhP
rrSIR
m
s
)()(
),(
ssmss
smrrm
mssm
PrIrI
rrhP
rrSIR ms
β
α
++
−
=
−
)()(
),(
∑
Φ∈
−
−=
c
ss roBz
xzss xzhPxI
),(
)(

α
( )
∑
−∆Φ∈
−
−
−=
c
smsm rrxBroBz
xzmm xzhPxI
),(),( 1
)(

α
O Small Cell
Macro Cell
sr
mr
r
1−
∆sr
1≥∆
18

Coverage Probability
Need the joint PDF of the distance pair
]|,[].[]|[].[=[Coverage] ssmm εεεε bsmsusmum TSIRTSIRPPTSIRPPP >>+>
∫∫>>
>>
0,0
dd),(],|,[
ms rr
msmsmsbsmsus rrrrfrrTSIRTSIRP
⇒ ),( ms rr
19

Small Cell Association
Network Topology
(A) Zero Intersection (B) Finite Intersection (C) Engulfment
20

Joint Probability Density Function
Access-Backhaul Distance Pair
Calculate an equivalent joint on distance pair (rs , r) instead of (rs , rm) using
void probabilities* of PPP
( )
( )






∆
+≥






∆
+<≤





∆
−
∂∂
∂






∆
−<<
∆
+∆
+−
−+∆−−
∆++−
−
1
1,4
1
1
1
1,
1
10,
)(4
22
21
2212
222
2
)),(lens)((
2
))/((22
s
rr
ssm
ss
s
MMrrr
s
rr
smsm
rrerr
rrr
rr
ee
rr
err
ssm
smss
smsm
λλπ
ππλπλ
λλλπ
λλπ
λλλπ
=),( rrf s
*R. K. Ganti "Stochastic geometry and wireless networks". SPCOM 2012 tutorial
21

Numerical Results
Results from evaluation of FD Self-Backhauling architecture
3

Coverage
Coverage Probability. Tm = Tb = −10 dB, λs = 4λm, Bs = 22 dB
23

Coverage (contd.)
Tm = Tb = Ts = −10 dB, Left: Bs = 34 dB. Right: λs = 4λm, Bs = 22 dB
24

Coverage (contd.)
Coverage Probability. Tm = Tb = Ts = −10 dB, λs = 4λm
25

Covered Rate
26
Tm = Tb = Ts = −10 dB. Left: λs = 4λm. Right: Bs = 22 dB

Conclusion
Deductions from employing IBFD self-backhauling in cellular networks
3

Summary
Conclusion
 Proposed IBFD-enabled self-backhauling HetNet architecture
 Modeled interplay between increased interference and high
spectral efficiency mathematically
 Average rates (~ 2x) at the cost of coverage
 Inter-tier interference and bandwidth division main bottlenecks
Way Forward
 Calls for amalgamation of IBFD with other 5G candidates like
massive MIMO
28

Any questions ?
Ankit Sharma
ankitsharma@ee.iitm.ac.in
Radha Krishna Ganti
rganti@ee.iitm.ac.in
Thanks!

Joint Probability Density Function
Access-Backhaul Distance Pair (contd.)
 Probability of zero intersection is
negligibly small
 In the limit of Bs , Engulfment case
(Case (C)) occupies the major
probability
 Probability of finite intersection
eventually  0
30

AnkitSharma_IBFD_SelfBH_ICC2016

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