Seoul, South Korea

1. Cooperative Multi-Small Cells
with Imperfect CSIT
Toha Ardi Nugraha, Soo Young Shin
Department of IT Convergence
Kumoh National Institute of Technology

2. Outlines
•
•
•
•
•
•
Introduction
Related Works
Objectives
System Model
Simulation Result
Conclusion and future works

3. Introduction
• Cooperative communications are some cells that in a network
can work together
– ex. joint transmit power from many cells.
– To improve the system capacity
• Cooperative system can be impractical in realistic settings due
to perfect channel state information at the transmitter (CSIT),
• But sometimes, CSIT may not be available due to the channel
estimation problems

4. Cooperative Small-Cells
Small cell is generally implemented at home or
office areas,
Easily implemented on cooperative
communication scheme
connected via a high-speed optical fiber backbone to the gateway

5. Cooperative Small-Cells
C
N t   nt ,1
(1)
i 1
N
N r   nr ,1 (2)
u j 1
Example :
• Source Nt = 4
• Destination Nr = 2
1
H u j   H u j ...

ℎ11 ℎ12 ℎ13 ℎ14
𝐻=
ℎ21 ℎ22 ℎ22 ℎ14
H uCj  (3)

2𝑥4

6. ).
CSI Channel state information (CSI)
• Channel state information (CSI) refers to known channel
properties of a communication link.
Channel Estimation Problems
• A model for the Channel Estimation Problems:
– Example : a noiseless, error-free, and delay-free feedback channel.

7. Imperfect CSIT
C
Imperfect CSIT
C
yu j   H w u   H ui j
i 1
i
uj
*
H uj 
i i
uj uj

u n u j , u n 
CN(0, )
i 1

unu j ,un 
e
H un H un
i i
wun uun
(5)
(6)
e
Error channel matrices
Power allocation for indoor propagation model
N
2
1
2  2


Pu j   
  Pc  
(8)

Lossu j N 
u j 1 Lossu j  Lossu j


 Pu  *
j
uj
Ru j  B *log 2 1 

2



 (9)




8. Simulation Setup
• Cooperative small cells with the number of
small cell = 3
– Max N_transmitter (Nt) = 2
– Max N_receiver (Nr) = 2
• Indoor Propagation Model : Cost 231 MWM
PLind  38.5  20log(d )  Lwalls

9. Simulation Result
Imperfect CSIT, when Nt = 3 and Nr =
6, the average throughput almost
same with perfect CSIT

10. Conclusion
• This paper shows the impact of imperfect CSIT on the performance
of cooperative small cells with deterrent Nr and NT.
• A power allocation based on water-filling algorithm is also
implemented in this system.
• the cooperative cells at the networks that has imperfect CSIT show
bad performances compare to cooperative small cells with perfect
CSIT.
• The more number of Nt and Nr can maintains the system capacity
Future Works
• will be extended with the extended preceding algorithm

11. 감사합니다