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# Ieek fall Conference 2013

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### Ieek fall Conference 2013

1. 1. Cooperative Multi-Small Cells with Imperfect CSIT Toha Ardi Nugraha, Soo Young Shin Department of IT Convergence Kumoh National Institute of Technology
2. 2. Outlines • • • • • • Introduction Related Works Objectives System Model Simulation Result Conclusion and future works
3. 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. 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. 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. 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. 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. 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. 9. Simulation Result Imperfect CSIT, when Nt = 3 and Nr = 6, the average throughput almost same with perfect CSIT
10. 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. 11. 감사합니다