Resource Allocation in HetNets [Master thesis PPT]

May, 2014 – Slide 1 Communication & Network Lab

Resource Allocation in Heterogeneous Networks

Master’s Thesis PresentationMay 23rd 2014

By Trung Kien Vu

Advisor: Prof. Sungoh KwonCommittee: 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. Introduction2. Problem and Contributions3. System Model4. Proposed Algorithms5. Simulation Results6. 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 CoverageMacrocells 43-46 dBm Few KmPicocells 23-30 dBm ≤ 300 mFemtocells ≤ 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 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)

of MUE m.

Minimize Subject to , m

: SINR threshold : Set of MUEs


System Model: The SINR at link 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.

and : the transmission power of HeNB and path gain between HeNB and MUE. is a set of HeNB.

: the thermal noise at macro user m.

( , ) ( )m

m

G M m P m

The received power from MeNBTotal interference and noise

( ) ( , )m f f f mP F G F m F


System Model: : the set of links from the MeNB to their serving MUEs, = ( . . ; ). The constraint can be transformed in matrix form as

= = , = such that

FP P bF M


Proposed Algorithm – ABSF Selection: When the HeNBs stop transmission on some subframes, the (SINR)

at link 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 mP F G F m

F

Reduced interference rate


Proposed Algorithm – ABSF Selection: Now, our objective can be transformed as

Minimize Subject to

where

A unique solution to this problem is

Now, we already get the optimal muted rate for MUE

,.

A PB P P b

F

F M

F

1( ) .T Tm 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 ParametersParameter ValuesSystem bandwidth 10 MHzChannel Model Urban Macro-Femto Scenario ModelMeNB Tx 46 dBmNumber of MUEs 20-100HeNB Tx 23 dBmNumber of HeNBs 40-400Number of MUE 40-400Thermal Noise -174 dBm/HzNoise Figure 9 dBSimulation Run Times 1000


Simulation Results

Algorithm NotationsNames NoticeNon ABSF Without eICICOptimal ABSF eICIC with optimal muted rateFixed ABSF - I eICIC with muted rate: 1/10Fixed ABSF - II eICIC with muted rate: 2/10Fixed ABSF – III eICIC with muted rate: 3/10Each 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 45 500

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Step

Avg

Mut

ed R

ate

Req

uire

d fo

r all

VM

UEs

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 501300

1350

1400

1450

1500

1550

1600

Step

Avg

Thr

ough

put o

f Fem

toce

ll U

sers [K

bps]

Optimal ABSFNon ABSFFixed ABSF - IFixed ABSF - IIFixed ABSF - III

0 5 10 15 20 25 30 35 40 45 50400

500

600

700

800

900

1000

Step

Avg

Thr

ough

put o

f Mac

roce

ll U

sers

[Kbp

s]

Optimal ABSFNon ABSFFixed ABSF - IFixed ABSF - IIFixed ABSF - III


Simulation Results

0 5 10 15 20 25 30 35 40 45 500

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Step

Out

age

Prob

abili

ty o

f Mac

ro U

sers

Non ABSFFixed ABSF - IFixed ABSF - IIFixed ABSF - IIIOptimal ABSF

Figure 7: Outage Probability.


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 !

Engineering

Resource Allocation in HetNets [Master thesis PPT]