Dual connectivity in heterogeneous cellular networks
Methods and systems for assigning users to nodes include assigning user devices to respective macro nodes in a wireless network. Each of the user devices is assigned to a respective pico node in the wireless network. Each respective pico node is associated with the same macro node that the respective user device is assigned to. Resource allocation fractions are assigned to all pico nodes and all macro nodes in the wireless network based on the assignment of each of the plurality of user devices respective macro nodes and pico nodes.
1. A method for assigning users to nodes, comprising:
assigning a plurality of user devices to respective macro nodes in a wireless network by solving a single optimization problem defined as:
max
x
u
,
b
∈
{
0
,
1
}
∀
u
∈
U
,
b
∈
S
{
∑
u
∈
U
∑
b
∈
S
x
u
,
b
ln
(
R
u
,
b
)
-
∑
b
∈
S
(
∑
k
∈
U
x
k
,
b
)
ln
(
∑
k
∈
U
x
k
,
b
)
}
s
.
t
.
∑
b
∈
S
x
u
,
b
=
1
,
∀
u
∈
U
where x u,b represents an assignment of a user u to a node b, x k,b represents an assignment of a user k to a node b, U represents the set of all users, S represents the set of all macro nodes and pico nodes, and R u,b represents an average peak rate that a user u can receive from a node b;
assigning each of the plurality of user devices to a respective pico node in the wireless network, each respective pico node being associated with the same macro node that the respective user device is assigned to; and
assigning resource allocation fractions to all pico nodes and all macro nodes in the wireless network based on the assignment of each of the plurality of user devices respective macro nodes and pico nodes.
2. The method of claim 1 , wherein assigning each of the plurality of user devices to a respective pico node comprises assigning each of the plurality of user devices to a pico node that has a highest received signal strength among all pico nodes associated with the same macro node that the user device is assigned to.
3. The method of claim 1 , wherein assigning resource allocation fractions to all pico nodes comprises solving an optimization problem for each macro node.
4. The method of claim 1 , wherein assigning the plurality of user devices to respective macro nodes and to respective pico nodes comprises generating initial assignments using a greedy approach and refining the initial assignments using an enhanced local search.
5. The method of claim 4 , wherein the enhanced local search comprises determining a best swap, deletion, and addition operation for a set of input assignments and performing whichever of the best swap, deletion, and addition operation provides the best improvement.
6. A system for assigning users to nodes, comprising:
a control module in communication with a plurality of macro nodes and a plurality of pico nodes in a wireless network, each of said plurality of pico nodes being associated to a respective one of the plurality of macro nodes, configured to communicate user associations and resource allocation fractions to the plurality of macro nodes and the plurality of pico nodes;
a node association module comprising a processor configured to assign a plurality of user devices to respective macro nodes by solving a single optimization problem and to assign each of the plurality of user devices to a respective pico node, each respective pico node being associated with the same macro node that the respective user device is assigned to, wherein the single optimization problem is defined as
max
x
u
,
b
∈
{
0
,
1
}
∀
u
∈
U
,
b
∈
S
{
∑
u
∈
U
∑
b
∈
S
x
u
,
b
ln
(
R
u
,
b
)
-
∑
b
∈
S
(
∑
k
∈
U
x
k
,
b
)
ln
(
∑
k
∈
U
x
k
,
b
)
}
s
.
t
.
∑
b
∈
S
x
u
,
b
=
1
,
∀
u
∈
U
where x u,b represents an assignment of a user u to a node b, x k,b represents an assignment of a user k to a node b, U represents the set of all users, S represents the set of all macro nodes and pico nodes, and R u,b represents an average peak rate that a user u can receive from a node b; and
an allocation fraction module configured to assign resource allocation fractions to all pico nodes and all macro nodes based on the assignment of each of the plurality of user devices' respective macro nodes and pico nodes.
7. The system of claim 6 , wherein the node association module is further configured to assign each of the plurality of user devices to a pico node that has a highest received signal strength among all pico nodes associated with the same macro node that the user device is assigned to.
8. The system of claim 6 , wherein the allocation fraction module is further configured to solve an optimization problem for each macro node to assign resource allocation fractions to all pico nodes and all macro nodes.
9. The system of claim 6 , wherein the node association module is further configured to generate initial assignments using a greedy approach and refining the initial assignments using an enhanced local search.
10. The system of claim 9 , wherein the node association module is further configured to determine a best swap, deletion, and addition operation for a set of input assignments and to perform whichever of the best swap, deletion, and addition operation provides the best improvement.