# US 8,149,933 B2 · Method and apparatus for subchannel assignment for suppressing interantenna interference in OFDMA system

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- Number: US 8,149,933 B2
- Document ID: US8149933B2
- Status: Granted
- Kind: B2
- Application number: 12/040,023
- Filed: 2008-02-29
- Published: 2008-09-04
- Granted: 2012-04-03
- Earliest claimed: 2007-03-02
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Shuangfeng Han; Seong-Taek Hwang; Zhunhui Zhou; Jing Wang; Ming Zhao; Zheng Xu
- Web page: https://patentgrep.com/patent/US8149933B2

## CPC

- H04L 27/2601: {Multicarrier modulation systems}
- H04L 5/0023: {Time-frequency-space}
- H04L 5/0032: {Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation}
- H04L 5/0037: {Inter-user or inter-terminal allocation}
- H04L 5/0062: {Avoidance of ingress interference, e.g. ham radio channels}
- H04L 5/023: {Multiplexing of multicarrier modulation signals, e.g. multi-user orthogonal frequency division multiple access [OFDMA] (multicarrier modulation H04L27/2601)}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Disclosed is a method and an apparatus for subchannel assignment for suppressing inter-antenna interference in an Orthogonal Frequency Division Multiplexing Access (OFDMA) system based distributed wireless communication system equipped with antennas that are randomly distributed in a geographical manner and can simultaneously communicate with multiple Subscriber Stations (SSs). The method includes selecting and obtaining access to distributed antennas which satisfy the data transmission rate that an SS requires and with which the SS can communicate; re-queuing a distributed antenna having the maximum transmitted power within the same cell in high priority; and assigning subchannels to the relevant distributed antennas in an order from the relevant distributed antenna having the high priority.

## Claims

### Claim 1

A method for subchannel assignment in an Orthogonal Frequency Division Multiplexing Access (OFDMA) system-based distributed wireless communication system equipped with antennas that are geographically distributed in a coverage area and can simultaneously communicate with multiple Subscriber Stations (SSs), the method comprising:
(a) selecting and obtaining access to antennas that satisfy a data transmission rate that an SS requires and with which the SS can communicate;
(b) re-queuing an antenna that transmits maximum power to the SS within the coverage area as a high priority antenna; and
(c) assigning subchannels to the highest priority antenna, wherein the assigning of subchannels comprises the steps of
finding subchannels used by adjacent antennas to the high priority antenna, located in sub areas adjacent to a sub area in which the high priority antenna is centered; and
assigning, to the high priority antenna, subchannels excluding those used by the adjacent antennas, while assigning other subchannels to the high priority antenna even if the other subchannels are used by antennas in the coverage area located in sub areas that are non-adjacent to the sub area of the high priority antenna.

### Claim 2 (depends on 1)

The method as claimed in claim 1, further comprising:
finding and assigning subchannels that are not used by the high priority antenna obtaining access to the SS when the data transmission rate required by the SS is not satisfied.

### Claim 3 (depends on 1)

The method as claimed in claim 1, further comprising:
providing information on the usable subchannels back to a Base Station (BS).

### Claim 4

An apparatus for subchannel assignment in an Orthogonal Frequency Division Multiplexing Access (OFDMA) system-based distributed wireless communication system having a plurality of distributed antennas for serving a coverage area and having a Base Station (BS) apparatus for subchannel assignment for controlling inter-antenna interference, the apparatus comprising:
a first assigning unit for finding subchannels used by a distributed antennas in the coverage area; and
a second assigning unit for specifying a distributed antenna that transmits maximum power to an SS as a high priority antenna, and assigning subchannels to the high priority antenna, wherein the assigning comprises assigning subchannels that are not the same as subchannels used by adjacent antennas located within sub areas adjacent to a sub area within which the high priority antenna is located, and assigning other subchannels to the high priority antenna for communication with the SS even if the other subchannels are in use by antennas in sub areas of the coverage area non-adjacent to the sub area of the high priority antenna.

### Claim 5 (depends on 4)

The apparatus as claimed in claim 4, wherein the BS further comprises:
a third assigning unit for finding and assigning subchannels that are not used by the relevant antenna obtaining access to the SS when the data transmission rate required by the SS is not satisfied.

### Claim 6

An apparatus for subchannel assignment in an Orthogonal Frequency Division Multiplexing Access (OFDMA) system-based distributed wireless communication system equipped with antennas that are geographically distributed in a coverage area and can simultaneously communicate with multiple Subscriber Stations (SSs), comprising:
a processor in communication with a memory, the memory including code providing instruction to said processor to execute:
(a) selecting and obtaining access to antennas that satisfy a data transmission rate that an SS requires and with which the SS can communicate;
(b) re-queuing an antenna that transmits maximum power to the SS within the coverage area as a high priority, antenna; and
(c) assigning subchannels to the high priority antenna, wherein the assigning of subchannels comprises the steps of
finding subchannels used by adjacent antennas to the high priority antenna, located in sub areas adjacent to a sub area in which the high priority antenna is centered; and
assigning, to the high priority antenna, subchannels excluding those used by the adjacent antennas, while assigning other subchannels to the high priority antenna even if the other subchannels are used by antennas in the coverage area located in sub areas that are non-adjacent to the sub area of the high priority antenna.

### Claim 7 (depends on 6)

The apparatus as claimed in claim 6, wherein the processor further executing code for:
finding and assigning subchannels that are not used by the antenna obtaining access to the SS when the data transmission rate required by the SS is not satisfied.

### Claim 8 (depends on 6)

The apparatus as claimed in claim 6, wherein the processor executing code for:
receiving information on the usable subchannels.

### Claim 9

A computer program stored in a tangible non-transitory computer readable medium causing a processor in an Orthogonal Frequency Division Multiplexing (OFDM) type wireless communications system to execute the steps of:
(a) selecting and obtaining access to antennas that satisfy a data transmission rate that an SS requires and with which the SS can communicate by determining:
c
k
,
p
=
1
N
⁢
∑
n
=
1
N
⁢
c
k
,
n
,
p
,
∀
p
;
wherein ck,p represents the number of bits per symbol;
p
′
=
arg
⁢
⁢
max
p
⁢
(
c
k
,
p
)
wherein p represents an antenna;
(b) re-queuing an antenna that transmits maximum power to an SS within a coverage area as a high priority antenna, as:
p
′
=
arg
⁢
⁢
max
p
⁢
(
c
k
,
p
)
wherein p represents an antenna; and
c
p
=
1
N
⁢
∑
k
=
k
1
k

K
p

⁢
c
k
,
p
(c) assigning subchannels to the highest priority antenna wherein the assigning comprises
finding subchannels used by antennas located in adjacent sub areas to a sub area within which the high priority antenna is centered;
assigning subchannels different from the found subchannels to the high priority antenna and expressed as;
n
′
=
arg
⁢
⁢
max
n
∈
(
U
-
V
p
-
U
p
)
⁢
(
c
k
,
n
,
p
)
,
where
Up is a set of subchannels assigned to the antenna p, and
Vp is a set of subchannels used by antennas adjacent to the antenna p); and
assigning other subchannels to the high priority antenna even if the other subchannels are used by antennas located in sub areas of the coverage area that are non-adjacent to the sub area of the high priority antenna.

### Claim 10 (depends on 9)

The program as claimed in claim 9, wherein the processor further executing:
finding and assigning subchannels that are not used by the antenna obtaining access to the SS when the data transmission rate required by the SS is not satisfied.

### Claim 11 (depends on 9)

The program of claim 9, further comprising:
receiving information on the usable subchannels.

### Claim 12

A method for determining subchannels associated with each of a plurality of geographically distributed antennas in a coverage area of an Orthogonal Frequency Division Multiplexing type wireless communication system serving a plurality of Subscriber Stations (SSs), comprising:
receiving information regarding each of the antennas for determining the data transmission rate required;
designating an antenna transmitting maximum power to an SS as a high priority antenna;
re-queuing each of the remaining antennas in an order with regard to the designated antenna;
assigning subchannels to the high priority antenna by finding subchannels used by antennas located in adjacent sub area to a sub area within which the high priority antenna is centered and assigning subchannels to the high priority antenna excluding the found subchannels while assigning other subchannels to the high priority antenna even if the other subchannels are used by antennas in the coverage area located in sub areas that are non-adjacent to the sub area of the high priority antenna.

### Claim 13 (depends on 12)

The method of claim 12, further comprising:
finding and assigning subchannels that are not used by the antenna obtaining access to the SS when the data transmission rate required by the SS is not satisfied.

### Claim 14

An apparatus for determining subchannels associated with each of a plurality of geographically distributed antennas in a coverage area of an Orthogonal Frequency Division Multiplexing type wireless communication system serving a plurality of Subscriber Stations (SSs), comprising:
a processor in communication with a memory, the memory containing code which when accessed by the processor causes the processor to execute the steps of:
receiving information regarding each of the antennas for determining the data transmission rate required;
designating an antenna transmitting maximum power to an SS as a high priority antenna;
re-queuing each of the remaining antennas in an order with regard to the designated antenna;
assigning subchannels to the high priority antennas by finding subchannels used by antennas located in adjacent sub areas to a sub area within which the high priority antenna is centered and assigning subchannels to the high priority antenna excluding the found subchannels while assigning other subchannels to the high priority antenna even if the other subchannels are used by antennas in the coverage area located in sub areas that are non-adjacent to the sub area of the high priority antenna.

### Claim 15 (depends on 14)

The apparatus of claim 14, wherein the processor further execute code for:
finding and assigning subchannels that are not used by the antenna obtaining access to the SS when the data transmission rate required by the SS is not satisfied.