US 7,411,924 B2Granted

Method for allocating subchannels in an OFDMA mobile communication system

AssigneesSamsung Electronics Co., Ltd., Korea Advanced Institute of Science and Technology

InventorsYoon-Ok Cho, Yong-Hoon Lee, Young-Ho Jung, Eung-Sun Kim, Jong-Hyeuk Lee, Jae-Hak Chung, Chang-Soo Hwang, Seung-Hoon Nam

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Abstract

An adaptive modulation scheme relating to an RA problem for maximizing the transmission rates of all users for maximum transmission rates in an OFDMA system including some users requiring to use services at fixed data rates. The scheme proposes introduction of an adaptive modulation using linear programming into an existing scheme for a system including a single kind of users, thereby enabling simultaneous execution of the adaptive modulation for all users in a system including two kinds of users. Further, the invention proposes another scheme of sequentially allocating subchannels to the users when the fixed transmission rate has a sufficiently small value, in order to reduce the complexity.

Claims15

Dependent claims

A method for allocating subchannels and bits to users in a mobile communication system including users requiring services of fixed transmission rates and users requiring services of variable transmission rates, for adaptive modulation, the method comprising the steps of:

determining a real number {z, ck} using a Lagrange Multiplier Method, the real number {z, ck} maximizing an objective equation in order to reconstruct a variable rate adaptive problem into a delivery problem;
solving the delivery problem through linear programming and allocating subchannels to the users;
and
allocating bits to the subchannels allocated to the users using a Greedy Algorithm,
wherein the Lagrange Multiplier Method is based on
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wherein ck denotes a number of bits to be allocated to a k-th user, Rk denotes a k-th user's data rate, PT denotes total allocated power, UFixed denotes a number of users requiring services of fixed transmission rates, URA denotes a number of users requiring services of variable transmission rates, ƒk(ck) denotes the K-th user's transmission power required for transmission satisfying a desired BER at a reception-side when a channel gain is 1, N denotes a number of the total subchannels, αk denotes a k-th user's channel gain, and λ and μ are parameters.

108 more elements

A method for allocating subchannels and bits in a mobile communication system including users that are using two different kinds of services for adaptive modulation, first users requiring services of fixed transmission rates and second users requiring services of variable transmission rates, the method comprising the steps of:

(1) allocating subchannels and bits to the second users;
(2) determining an initial number NMA of subchannels to be allocated to the first users;
(3) consequently releasing the determined initial number NMA of subchannels from among the subchannels previously allocated to the second users;
(4) reallocating the released subchannels to the first users;
(5) allocating bits for the first users to reallocated subchannels;
and
(6) repeating steps 3 through 5 a predetermined number of times for generating a number of non-initial released subchannels.

4 more elements

An apparatus for transmitting data to users through adaptive modulation in a mobile communication system including users requiring services of fixed transmission rates and users requiring services of variable transmission rates, the apparatus comprising:

a subchannel allocation and bit loading algorithm unit for determining a real number {z, ck} that maximizes an objective equation using a Lagrange Multiplier Method in order to reconstruct a variable rate adaptive problem into a delivery problem, solving the delivery problem through linear programming and allocating subchannels to each of the users, and allocating bits to the subchannels allocated to the users by using a Greedy Algorithm;
an adaptive modulator for adaptively modulating user data by means of the subchannels and bits allocated to the users and separately outputting the data for the allocated subchannels;
and
an Inverse Fast Fourier Transform (IFFT) unit for converting the separated user data into a time domain signal and outputting the time domain signal as a signal sequence,
wherein the Lagrange Multiplier Method is based on
max
z
,
c
k
⁢
(
z
,
c
k
,
λ
,
μ
)
=
z
-
λ
⁡
(
∑
k
∈
U
Fixed
⁢
⁢
f
k
⁡
(
c
k
)
·
R
M
/
α
k
2
⁢
c
k
+
∑
k
∈
U
RA
⁢
⁢
f
k
⁡
(
c
k
)
·
z
/
α
k
2
⁢
c
k
-
P
T
)
-
μ
⁡
(
∑
k
∈
U
Fixed
⁢
⁢
R
M
/
c
k
+
∑
k
∈
U
RA
⁢
⁢
z
/
c
k
-
N
)
wherein ck denotes a number of bits to be allocated to a k-th user, Rk denotes a k-th user's data rate, PT denotes a total allocated power, UFixed denotes a number of users requiring services of fixed transmission rates, URA denotes a number of users requiring services of variable transmission rates, ƒk(ck) denotes the K-th user's transmission power required for transmission satisfying a desired BER at a reception-side when a channel gain is 1, N denotes a number of the total subchannels, αk denotes a k-th user's channel gain, and λ and μ are parameters.

108 more elements

An apparatus for transmitting data to users through adaptive modulation in a mobile communication system including first users requiring services of fixed transmission rates and second users requiring services of variable transmission rates, the apparatus comprising:

a subchannel allocation and bit loading algorithm unit for allocating subchannels and bits to the second users, determining an initial number of subchannels to be allocated to the first users, releasing the initial number of subchannels from among the subchannels allocated to the second users, reallocating the released subchannels to the first users, and allocating bits for the first users to reallocated subchannels;
an adaptive modulator for adaptively modulating user data by means of the subchannels and bits allocated to the users and separately outputting the data for each of the allocated subchannels;
and
an Inverse Fast Fourier Transform (IFFT) unit for converting the separated user data into a time domain signal and outputting the time domain signal as a signal sequence,
wherein the subchannel allocation and bit loading algorithm unit repeats the process from the releasing of the initial number of subchannels to the allocation of the bits a predetermined number of times.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/996,699Filed 24 Nov 2004
Priority: KR 10-2003-008402925 Nov 2003
Published: US 2005/0180354 A118 Aug 2005
Granted: 12 Aug 2008
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H04L 5/023
Channels characterised by the type of signal: multiplexing of multicarrier modulation signals, e.g. multi-user orthogonal frequency division…
H04L 1/0003
By adapting the transmission rate: by switching between different modulation schemes
H04L 1/0015
Systems modifying transmission characteristics according to link quality, e.g. power backoff: characterised by the adaptation strategy
H04L 5/0044
Arrangements for allocating sub-channels of the transmission path: allocation of payload; Allocation of data channels, e.g. PDSCH or PUSCH

Family

US 2005/0180354 A1Pre-grant publication · published 18 Aug 2005
US 7,411,924 B2This patent

From the US filing history. Foreign family members aren’t listed.

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