Apparatus and method for allocating frequency resource to micro UE in a mobile communication system

1. A method for allocating frequency resources to each micro User Equipment (UE) at a micro Base Station (BS) in mobile communication system of a hierarchical cell structure, the method comprising:

acquiring information about traffic of each macro UE or a macro BS in a frequency resource allocated to the each macro UE or the macro BS, first Signal-to-Noise Ratio (SNR) information about an SNR of a signal from the each macro UE or the macro BS, measured at each micro UE and second SNR information about an SNR of a signal from the each micro UE, measured at the micro BS;

calculating throughput of the each micro UE using the traffic information, the first SNR information and the second SNR information;

determining a frequency resource to be allocated to the each micro UE using information about the calculated throughput; and

allocating the determined frequency resource to the each micro UE.

2. The method according to claim 1 , wherein the traffic information of the each macro UE or a macro BS includes information {λ m } about an average arrival rate of packets of the each macro UE or the macro BS and information {μ m } about an average service rate of packets of the each macro UE or the macro BS.

3. The method according to claim 2 , wherein the first SNR information is information about SNRs of signals from the each macro UE or the macro BS in first to M th frequency resources, measured at first to N th micro UEs and expressed as an M×N matrix.

4. The method according to claim 3 , wherein the second SNR information is information about SNRs of signals from the first to N th micro UEs in the first to M th frequency resources and expressed as an M×N matrix.

5. The method according to claim 2 , wherein the throughput calculation comprises calculating the throughput of the each micro UE so that interference caused to the each micro UE satisfies a preset condition.

6. The method according to claim 5 , wherein the throughput calculation comprises calculating using the throughput of the each micro UE using the information {λ m } about the average arrival rate of packets of the each macro UE or the macro BS, the information {μ m } about the average service rate of packets of the each macro UE or the macro BS, a preset ratio of a busy period corresponding to data transmission period of the each macro UE to a total period of the each macro UE, a non-false alarm probability being a probability of correctly detecting, through spectrum sensing, that the each macro UE or the macro BS is not using an m th frequency resource by an n th micro UE, and a channel capacity that the n th micro UE can achieve when the n th micro UE transmits a signal without interference through successful spectrum sensing.

7. The method according to claim 6 , wherein the calculated throughput is expressed as the following [Equation A],

c

m

,

n

=

P

m

Idle

⁢

n

P

-

n

D

n

P

⁢

(

1

-

P

FA

m

,

n

)

⁢

C

m

,

n

[

Equation

⁢

⁢

A

]

where P m Idle denotes a ratio of an idle period of the each macro UE or the macro BS to a total period of the each macro UE or

the macro BS, calculated using the information {λ m } about the average arrival rate of packets of the each macro UE or the macro BS,

n D denotes a sensing slot period, n r denotes a sample period,

n

P

-

n

D

n

P

denotes the preset ratio of the busy period to the total period, 1−P FA m,n denotes the non-false alarm probability calculated using the first SNR information and C m,n denotes the channel capacity calculated using the second SNR information.

8. The method according to claim 7 , wherein the ratio of the idle period to the total period is calculated using the information {λ m } about the average arrival rate of packets of the each macro UE or the macro BS and the information {μ m } about the average service rate of packets of the each macro UE or the macro BS.

9. The method according to claim 7 , wherein a false alarm probability P FA m,n is calculated using the first SNR information, a spectrum sensing time period of the each micro UE and a target detection probability of a signal from the each micro UE or the micro BS.

10. The method according to claim 9 , wherein

the false alarm probability P FA m,n is calculated using the following (Equation B),

P

FA

m

,

n

=

Q

⁡

(

n

D

⁢

γ

m

,

n

P

+

(

1

+

γ

m

,

n

P

)

⁢

Q

-

1

⁡

(

P

D

t

)

)

[

Equation

⁢

⁢

B

]

where a Q function is a monotonically decreasing function for x, given as

Q

⁡

(

x

)

=

1

2

⁢

π

⁢

∫

x

∞

⁢

ⅇ

-

t

2

/

2

⁢

ⅆ

t

,

Q −1 denotes inverse of the Q function, P D t denotes the target detection probability of a signal from the each micro UE or the micro BS

and γ m,n p denotes the firt SNR information.

11. The method according to claim 7 , wherein the channel capacity C m,n is calculated using the following [Equation C],

C m,n =log 2 (1+γ m,n s ),  [Equation C]

where {γ m,n s } denotes the second SNR information.

12. The method according to claim 1 , wherein the frequency resource determination comprises determining a frequency resource that can maximize a sum throughput of the each micro UE.

13. The method according to claim 12 , wherein the determined frequency resource is calculated using the following [Equation D],

max

⁢

∑

m

=

0

M

-

1

⁢

∑

n

=

0

N

-

1

⁢

c

m

,

n

⁢

x

m

,

n

⁢

⁢

s

.

t

.

⁢

∑

m

=

0

M

-

1

⁢

x

m

,

n

≤

1

,

n

=

1

,

…

⁢

,

N

⁢

⁢

∑

n

=

0

N

-

1

⁢

x

m

,

n

≤

1

,

m

=

1

,

…

⁢

,

M

⁢

⁢

x

m

,

n

≥

0

,

∀

m

,

n

[

Equation

⁢

⁢

D

]

where

∑

m

=

0

M

-

1

⁢

∑

n

=

0

N

-

1

⁢

c

m

,

n

⁢

x

m

,

n

denotes a sum throughput of all cases in which an m th frequency resource is allocated to an n th micro UE,

∑

m

=

0

M

-

1

⁢

x

m

,

n

≤

1

is a constraint that up to one frequency resource should be allocated to each micro UE,

∑

n

=

0

N

-

1

⁢

x

m

,

n

≤

1

is a constraint that up to one micro UE should be allocated to each frequency resource and x m,n ≧0 indicates that a frequency resource should be allocated (x m,n =1) or not allocated (x m,n =0).

14. The method according to claim 12 , wherein the determined frequency resources are expressed as a frequency resource allocation matrix and the frequency resource determination comprises calculating the frequency resource allocation matrix using an auction algorithm or a Hungarian algorithm.

15. The method according to claim 12 , wherein the frequency resource allocation comprises allocating one determined frequency resource to only one micro UE.

16. A micro Base Station (BS) for allocating frequency resources to each micro User Equipment (UE) in mobile communication system of a hierarchical cell structure, the micro BS comprising:

an initial information acquisition module for acquiring information about traffic of each macro UE or a macro BS in a frequency resource allocated to the each macro UE or the macro BS, first Signal-to-Noise Ratio (SNR) information about an SNR of a signal from the each macro UE or the macro BS, measured at each micro UE and second SNR information about an SNR of a signal from the each micro UE, measured at the micro BS;

a throughput calculation module for calculating throughput of the each micro UE using the traffic information, the first SNR information and the second SNR information;

a frequency resource decision module for determining a frequency resource to be allocated to the each micro UE using information about the calculated throughput; and

a frequency resource allocation module for allocating the determined frequency resource to the each micro UE.

17. The micro BS according to claim 16 , wherein the traffic information of the each macro UE or a

macro BS included information {λ m } about an average arrival rate of packets of the each macro UE or the macro BS and

information {μ m } about an average service rate of packets of the each macro UE or the macro BS.

18. The micro BS according to claim 17 , wherein the first SNR information is information about SNRs of signals from the each macro UE or the macro BS in

first to M th frequency resources, measured at first to N th micro UEs and expressed as an M×N matrix.

19. The method according to claim 18 , wherein the second SNR information is information about SNRs of signals from the first to N th micro UEs in the first to M th frequency resources and is expressed as an M×N matrix.

20. A method for allocating frequency resources to each micro User Equipment (UE) in a micro Base Station (BS) in mobile communication system of a hierarchical cell structure, the method comprising:

acquiring information about traffic of each macro UE or a macro BS in a frequency resource allocated to the each macro UE or the macro BS and Signal-to-Noise Ratio (SNR) information about an SNR of a signal from the micro BS, measured at the each micro UE;

calculating throughput of the each micro UE using the traffic information and the SNR information;

determining a frequency resource to be allocated to the each micro UE using information about the calculated throughput; and

allocating the determined frequency resource to the each micro UE.

21. The method according to claim 20 , wherein the traffic information of the each macro UE or the macro BS includes information {λ m } about an average arrival rate of packets of the each macro UE or the macro BS and information {μ m } about an average service rate of packets of the each macro UE or the macro BS.

22. The method according to claim 21 , wherein the SNR information is information about SNRs of a signal from the micro BS in first to M th frequency resources, measured by first to N th micro UEs and expressed as an M×N matrix.

23. The method according to claim 21 , wherein the throughput calculation comprises calculating the throughput of the each micro UE so that interference caused to the each micro UE satisfies a preset condition.

24. The method according to claim 23 , wherein the throughput calculation comprises calculating the throughput of the each micro UE using the information {λ m } about the average arrival rate of packets of the each macro UE or the macro BS, the information {μ m } about the average service rate of packets of the each macro UE or the macro BS, a preset ratio of a busy period corresponding to data transmission period of the macro UE to a total period of the each macro UE and a channel capacity that an n th micro UE can achieve when the n th micro UE transmits a signal in an m th frequency resource without interference through successful spectrum sensing.

25. The method according to claim 24 , wherein the calculated throughput is expressed as the following

[Equation E],

c

m

,

n

=

P

m

Idle

⁢

n

P

-

n

D

n

P

⁢

(

1

-

P

FA

m

,

n

)

⁢

C

m

,

n

[

Equation

⁢

⁢

E

]

where P m Idle denotes a ratio of an idle period of the each macro UE or the macro BS to a total period of the each macro UE or

the macro BS, calculated using the information {λ m } about the average arrival rate of packets of the each macro UiE or the macro BS and the information {μ m } about the average service rate of packets of the each macro LE or the macro BS, n D denotes a sensing slot period, n P denotes a sample period,

n

P

-

n

D

n

P

denotes the preset ratio of the busy period to the total period and C m,n denotes the channel capacity calculated using the SNR information.

26. The method according to claim 25 , wherein the channel capacity C m,n is calculated using the following [Equation F],

C m,n =log 2 (1+γ m,n s ),  [Equation F]

where {γ m,n s } denotes the SNR information.

27. The method according to claim 20 , wherein the frequency resource determination comprises determining a frequency resource that can maximize a sum throughput of the each micro UE.

28. The method according to claim 27 , wherein the determined frequency resource is calculated using the following [Equation G],

max

⁢

∑

m

=

0

M

-

1

⁢

∑

n

=

0

N

-

1

⁢

c

m

,

n

⁢

x

m

,

n

⁢

⁢

s

.

t

.

⁢

∑

m

=

0

M

-

1

⁢

x

m

,

n

≤

1

,

n

=

1

,

…

⁢

,

N

∑

n

=

0

N

-

1

⁢

x

m

,

n

≤

1

,

m

=

1

,

…

⁢

,

M

x

m

,

n

≥

0

,

∀

m

,

n

[

Equation

⁢

⁢

G

]

where

∑

m

=

0

M

-

1

⁢

∑

n

=

0

N

-

1

⁢

c

m

,

n

⁢

x

m

,

n

denotes a sum throughput of all cases in which an m th frequency resource is allocated to an n th micro UE,

∑

m

=

0

M

-

1

⁢

x

m

,

n

≤

1

is a constraint that up to one frequency resource should be allocated to each micro UE,

∑

n

=

0

N

-

1

⁢

x

m

,

n

≤

1

is a constraint that up to one micro UE should be allocated to each frequency resource and x m,n ≧0 indicates that a frequency resource should be allocated (x m,n =1) or not allocated (x m,n =0).

29. The method according to claim 28 , wherein the frequency resource allocation comprises allocating one determined frequency resource to only one micro UE.

30. A micro Base Station (BS) for allocating frequency resources to each micro User Equipment (UE) in mobile communication system of a hierarchical cell structure, the micro BS comprising:

an initial information acquisition module for acquiring information about traffic of each macro UE or a macro BS in a frequency resource allocated to the each macro UE or the macro BS and Signal-to-Noise Ratio (SNR) information about an SNR of a signal from the micro BS, measured at the each micro UE;

a throughput calculation module for calculating throughput of the each micro UE using the traffic information and the SNR information;

a frequency resource decision module for determining a frequency resource to be allocated to the each micro UE using information about the calculated throughput;

and a frequency resource allocation module for allocating the determined frequency resource to the each micro UE.

31. The micro BS according to claim 30 , wherein the traffic information includes information {λ m } about an average arrival rate of packets of the each macro UE or the macro BS and information {μ m } about an average service rate of packets of the each macro UE or the macro BS.

32. The micro BS according to claim 31 , wherein the SNR information is information about SNRs of a signal from the micro BS in first to M th frequency resources, measured from first to N th micro UEs and expressed as an M×N matrix.

33. The micro BS according to claim 31 , wherein the throughput calculation module calculates the throughput of the each micro UE so that interference caused to the each micro UE satisfies a preset condition.

34. The micro BS according to claim 33 , wherein the throughput calculation module calculates the throughput of the each micro UE using the information {λ m } about the average arrival rate of packets of the each macro UE or the macro BS, the information {μ m } about the average service rate of packets of the each macro UE or the macro BS, a preset ratio of a busy period corresponding to data transmission period of the each macro UE to a total period of the each macro UE and a channel capacity that an n th micro UE can achieve when the n th micro UE transmits a signal in an m th frequency resource without interference through successful spectrum sensing.

35. The micro BS according to claim 30 , wherein the frequency resource decision module comprises determining a frequency resource that can maximize a sum throughput of the each micro UE.

36. The micro BS according to claim 35 , wherein the frequency resource decision module calculates the frequency resource using the following [Equation H],

max

⁢

∑

m

=

0

M

-

1

⁢

∑

n

=

0

N

-

1

⁢

c

m

,

n

⁢

x

m

,

n

⁢

⁢

s

.

t

.

∑

m

=

0

M

-

1

⁢

x

m

,

n

≤

1

,

n

=

1

,

…

⁢

,

N

∑

n

=

0

N

-

1

⁢

x

m

,

n

≤

1

,

m

=

1

,

…

⁢

,

M

x

m

,

n

≥

0

,

∀

m

,

n

[

Equation

⁢

⁢

H

]

where

∑

m

=

0

M

-

1

⁢

∑

n

=

0

N

-

1

⁢

c

m

,

n

⁢

x

m

,

n

denotes a sum throughput of all cases in which an m th frequency resource is allocated to an n th micro UE,

∑

m

=

0

M

-

1

⁢

x

m

,

n

≤

1

is a constraint that up to one frequency resource should be allocated to each micro UE,

∑

n

=

0

N

-

1

⁢

x

m

,

n

≤

1

is a constraint that up to one micro UE should be allocated to each frequency resource and x m,n ≧0 indicates that a frequency resource should be allocated (x m,n =1) or not allocated (x m,n =0).

37. The micro BS according to claim 36 , wherein the frequency resource allocation module allocates a determined one frequency resource to only one micro UE.