Resource Allocation in Heterogeneous Networks

May, 2014 – Slide 1 Communication & Network Lab
Resource Allocation in Heterogeneous
Networks
Master’s Thesis Presentation
May 23rd 2014
By Trung Kien Vu
Advisor: Prof. Sungoh Kwon
Committee: Prof. Chong-Koo An, (chair)
Prof. Sungoh Kwon,
Prof. Sunghwan Kim.

Research Interests:
- Interference management and resource allocation: Heterogeneous
and Small Cell Networks.
 Trung Kien Vu and Sungoh Kwon, “eICIC-based Interference Mitigation in Small Cell
Networks”. [In preparation].
- Routing protocols: Mobile Ad-hoc Networks and Wireless Sensor
Networks.
 Trung Kien Vu and Sungoh Kwon, “Mobility-Assisted On-Demand Routing Algorithm
for MANETs in the Presence of Location Errors”, The Scientific World Journal, vol.
2014, Article ID 790103, 11 pages, 2014.

Outline:
1. Introduction
2. Problem and Contributions
3. System Model
4. Proposed Algorithms
5. Simulation Results
6. Conclusions

Introduction:
 The demand for mobile data traffic
 Solution: Heterogeneous Networks (HetNets)

Introduction:
 What is HetNet?
 Consisting of multiple types of access nodes such as macro cells
and smallcells (picocells and femtocells).
 Smallcells are deployed under the coverage of macrocell.
 Smallcells provide the indoor and outdoor wireless services by
extending the network coverage and increasing the network
capacity.
Node types Transmission Power Coverage
Macrocells 43-46 dBm Few Km
Picocells 23-30 dBm ≤ 300 m
Femtocells ≤ 23 dBm ≤ 50m

Problem:
 HetNet consists of Macrocells and Femtocells.
 Macrocells and Femtocells share the same radio frequency
 It causes the cross-layer interference between Macrocells and
Femtocells
Macrocells
Picocells Femtocells

Problem: Example
 Macro base station: MeNB
 Femto base station: HeNB
 Macro User: MUE
 Femto User: HUE
Figure 2: System

Previous work:
 Enhanced Inter-Cell Interference Coordination eICIC is introduced
to address cross-layer interference between macro and femtocells.
 Almost Blank Subframe ABSF is one of eICIC techniques in which
the interfering cell will stop using some subframes in order to
reduce the ICI.
No Transmission Transmission
Figure 3: ABSF subframes

Previous work:
 Previous work use fixed ABSF pattern and all HeNBs are globally
set to same ABSF based on number of users.
 There is no coordination mechanism between femtocell base
stations HeNBs.
 How many and which subframes should be muted ?

Contributions:
 In this paper, our contributions include:
 Dynamically optimal ABSF Selection Algorithm for each
HeNB based on the Quality of Service of macro users.
 Interference HeNB Coalition Algorithm to reduce the mutual
interference.

System Model: Objective
 Find the optimal muted rate 𝛼 𝑚 for each MUE m.
(defined as number of muted subframes (ABSF) over number of all subframes)
 That satisfies the Signal-to-Interference-and-Noise Ratio (SINR)
𝛾 𝑚 of MUE m.
Minimize 𝛼 𝑚
Subject to 𝛾 𝑚≽ 𝛾0 , m  ℳ
𝛾0 : SINR threshold
ℳ : Set of MUEs

System Model:
 The SINR 𝛾 𝑚 at link ℒ 𝑚 between the MeNB and the MUE m is
calculated as
P(m) and G(M,m) : the transmission power of MeNB and path gain
between MeNB and MUE.
𝑃(𝐹𝑓 and 𝐺(𝐹𝑓, 𝑚 : the transmission power of HeNB and path
gain between HeNB and MUE. ℱ is a set of HeNB.
𝜎 𝑚 : the thermal noise at macro user m.
( , ) ( )
m
m
G M m P m



The received power from MeNB
Total interference and noise
( ) ( , )m f f f m
P F G F m 
 F

System Model:
 ℒ : the set of links from the MeNB to their serving MUEs,
ℒ = (ℒ1, . . ; ℒℳ).
 The constraint 𝛾 𝑚≽ 𝛾0 can be transformed in matrix form as
 𝐅 𝑚, 𝑓 =
𝐺 𝐹 𝑓,𝑚 𝛾0
𝐺(𝑀,𝑚
, 𝐏ℱ = (P(1), … , P(𝐹𝑓 )) 𝑇
 𝐏ℳ = (P(1), … , P(ℳ)) 𝑇
,
 𝒃 = (b(1), … , b(ℳ)) 𝑇
such that 𝑏(𝑚 =
𝛾0 𝜎 𝑚
𝐺(𝑀,𝑚
 FP P bF M

Proposed Algorithm – ABSF Selection:
 When the HeNBs stop transmission on some subframes, the (SINR)
𝛾 𝑚 at link ℒ 𝑚 can be rewritten as
 The received power from HeNbs is reduced in order to increase the
SINR of MUE m.
( , ) ( )
( ) ( , )(1 )
m
f f f m m
G M m P m
P F G F m

 

  F
Reduced interference rate

Proposed Algorithm – ABSF Selection:
 Now, our objective can be transformed as
Minimize 𝛼 𝑚
Subject to 𝐀𝛼 𝑚 ≽ 𝐁
 where
 A unique solution to this problem is
 Now, we already get the optimal muted rate for MUE
,
.

  
A P
B P P b
F
F M
F
1
( ) .T T
m
 
 A AA B

Proposed Algorithm – Interfering HeNB Coalition
 To group the mutual interfering HeNB to cooperate in
ABSF mode efficiently.
Figure 4: Coalition Example

 Including 2 mechanisms:
 Mechanism 1: to find the victim MUEs affected by
each HeNB.
 Mechanism 2: to group HeNBs having same Victim
MUE.

 Mechanism 1: to find the victim MUEs affected by
each HeNB.
 Detect the Victim MUEs
 Report interfering HeNB’s list to MeNB.
 Do set intersection algorithm by MeNB having the
same HeNBs.
 Send Victim MUE’s list to HeNB

 Mechanism 2: to group HeNBs having same Victim
MUE.
 Exchange the VMUE’s list to neighbor HeNBs
 Do set intersection algorithm having the same VMUE.
 Set the muted rate for HeNB.
 Active the ABSF mode.

Simulation Results
 Simulation Parameters
Parameter Values
System bandwidth 10 MHz
Channel Model Urban Macro-Femto Scenario Model
MeNB Tx 46 dBm
Number of MUEs 20-100
HeNB Tx 23 dBm
Number of HeNBs 40-400
Number of MUE 40-400
Thermal Noise -174 dBm/Hz
Noise Figure 9 dB
Simulation Run Times 1000

Simulation Results
 Algorithm Notations
Names Notice
Non ABSF Without eICIC
Optimal ABSF eICIC with optimal muted rate
Fixed ABSF - I eICIC with muted rate: 1/10
Fixed ABSF - II eICIC with muted rate: 2/10
Fixed ABSF – III eICIC with muted rate: 3/10
Each step Distance between HeNB and MUE is
gradually increased in order to reduce
interference

Simulation Results
Figure 5: The required muted rate
0 5 10 15 20 25 30 35 40 45 50
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Step
AvgMutedRateRequiredforallVMUEs
Optimal Muted Rate

Simulation Results
Macro users Throughput Femto users Throughput
Figure 6: The user throughput –
performance balance between Macro and Femto users
0 5 10 15 20 25 30 35 40 45 50
1300
1350
1400
1450
1500
1550
1600
Step
AvgThroughputofFemtocellUsers[Kbps] Optimal ABSF
Non ABSF
Fixed ABSF - I
Fixed ABSF - II
Fixed ABSF - III
0 5 10 15 20 25 30 35 40 45 50
400
500
600
700
800
900
1000
Step
AvgThroughputofMacrocellUsers[Kbps]
Optimal ABSF
Non ABSF
Fixed ABSF - I
Fixed ABSF - II
Fixed ABSF - III

Simulation Results
0 5 10 15 20 25 30 35 40 45 50
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Step
OutageProbabilityofMacroUsers
Non ABSF
Fixed ABSF - I
Fixed ABSF - II
Fixed ABSF - III
Optimal ABSF
Figure 7: Outage Probability.
# 𝑜𝑓 𝑈𝑛𝑠𝑎𝑡𝑖𝑠𝑓𝑖𝑒𝑑 𝑈𝑠𝑒𝑟𝑠
# 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑈𝑠𝑒𝑟𝑠

Conclusions
 To address the cross-layer interference between macro and femto
cell layers by
 Propose a dynamically optimal ABSF eICIC framework based
on the quality of service of macro users.
 Group interfering HeNBs in ABSF mode to reduce mutual
interference among HeNBs
 The simulation results show that our algorithms outperform
previous work and bring good solutions for smallcell networks.

Thank you for your time !

Resource Allocation in Heterogeneous Networks

More Related Content

What's hot (20)

Viewers also liked (12)

Similar to Resource Allocation in Heterogeneous Networks (20)

Recently uploaded (20)

Resource Allocation in Heterogeneous Networks