Technical Field
[0001]
10 The present invention relates to a path control method, a wireless
communication system, a path control device, and a non-transitory
computer readable medium, and more particularly to path control for use in
a mobile backhaul network.
Background Art
15 [0002]
As the information technology progresses in recent years, a demand
for data communication traffic by data communication or the like is
increasing. Under this circumstance, broadband communication in a
network and reduction in operation cost have been required. A network
20 constituted of radio links such as an FWA (Fixed broadband Wireless
Access) employing a wireless system utilizing a frequency of a millimeter
wave band or the like capable of broadband transmission is utilized in a
mobile phone network or the like.
[0003]
25 An FWA is a system configured to connect a plurality of locally
placed base stations to each other by wireless communication so as to
connect to a core network in a mobile communication system such as a
mobile phone. This system has the advantages that the work period can
be shortened, as compared with a wired network, and that the cost required
2
for cable placing can be reduced. In recent years, this system is
employed by mobile telecommunications carriers, as a connection line for
connecting between wireless base stations in a mobile network via a radio
link.
5 [0004]
A network for configuring an FWA is constituted of radio links.
Therefore, communication quality of the network varies according to an
SNR (Signal to Noise Ratio) of a receiving signal. In view of the above,
in order to implement further broadband communications using a radio link,
10 an adaptive modulation technique has been paid attention to. The
adaptive modulation technique is a technique, in which a modulation
method having a highest transmission efficiency is adaptively obtained
from a radio condition of a radio link for using the modulation method.
The adaptive modulation technique makes it possible to perform optimum
15 wireless communication depending on the radio environment, and
enhancement of frequency efficiency can be expected.
[0005]
PTL 1 discloses a path control method, in which a modulation
method capable of stably using a radio link is estimated from a history of
20 modulation methods in the past or the like, in view of a point that the band
of a radio link changes according to adaptive modulation, and
communication quality requested by traffic is secured by using the link
band of the estimated modulation method.
[0006]
25 However, selecting a radio link of modulation method capable of
being used stably under the consideration of stability may lower the traffic
accommodation efficiency. Further, according to the path control method
as described above, the number of times of hopping the path increases, and
the path is likely to be redundant, resulting in an increase in delay even in
3
a path having a high degree of stability.
Citation List
Patent Literature
[0007]
5 PTL 1: Published Japanese Translation of PCT International Publication
for Patent Application No. 2009-504090
Summary of Invention
Technical Problem
[0008]
10 In the related technique, it is not possible to secure efficient traffic
accommodation, while maintaining communication quality in computing a
path of traffic.
In view of the above-described problems, an object of the present
invention is to provide a path control method, a wireless communication
15 system, a path control device, and a non-transitory computer readable
medium which enable to secure efficient traffic accommodation, while
maintaining communication quality.
Solution to Problem
[0009]
20 A path control method according to an aspect selects one path from
among a plurality of path candidates with respect to a specific piece of
traffic in a network constituted of a radio link provided with an adaptive
modulation function. The path control method is provided with a
comparing step of comparing a requested band of the piece of traffic, and
25 an allocatable band allocatable to a first path candidate that is included in
the plurality of path candidates and that satisfies a degree of stability
requested by the piece of traffic by a first modulation method; and a
selecting step of giving a penalty cost due to transmission using a band
usable by a second modulation method whose degree of stability is lower
4
than the first modulation method to the first path candidate so that the first
path candidate is less likely to be selected, when the requested band of the
piece of traffic is larger than the allocatable band as a result of the
comparison for selecting one path from among the plurality of path
5 candidates.
[0010]
A wireless communication system according to another aspect is
provided with a device which controls a communication path by selecting
one path from among a plurality of path candidates with respect to a
10 specific piece of traffic in a network constituted of a radio link provided
with an adaptive modulation function. The wireless communication
system is provided with a comparing means which compares a requested
band of the piece of traffic, with an allocatable band allocatable to a first
path candidate that is included in the plurality of path candidates and that
15 satisfies a degree of stability requested by the piece of traffic by a first
modulation method; and a selecting means which gives a penalty cost due
to transmission using a band usable by a second modulation method whose
degree of stability is lower than the first modulation method to the first
path candidate so that the first path candidate is less likely to be selected,
20 when the requested band of the piece of traffic is larger than the
allocatable band as a result of the comparison for selecting one path from
among the plurality of path candidates.
[0011]
A path control device according to yet another aspect is provided
25 with a control unit having an adaptive modulation function, and a wireless
antenna which wirelessly communicates with a communication device.
The control unit controls a communication path by selecting one path from
among a plurality of path candidates with respect to a specific piece of
traffic in a network connected to the communication device by a radio link.
5
The path control device is further provided with a comparing means which
compares a requested band of the piece of traffic, with an allocatable band
allocatable to a first path candidate that is included in the plurality of path
candidates and that satisfies a degree of stability requested by the piece of
5 traffic by a first modulation method; and a selecting means which gives a
penalty cost due to transmission using a band usable by a second
modulation method whose degree of stability is lower than the first
modulation method to the first path candidate so that the first path
candidate is less likely to be selected, when the requested band of the piece
10 of traffic is larger than the allocatable band as a result of the comparison
for selecting one path from among the plurality of path candidates.
[0012]
A non-transitory computer readable medium storing a program
which causes a computer to execute path control according to still another
15 aspect is operative to select one path from among a plurality of path
candidates with respect to a specific piece of traffic in a network
constituted of a radio link provided with an adaptive modulation function.
The non-transitory computer readable medium stores the program which
causes the computer to execute: a comparing step of comparing a requested
20 band of the piece of traffic, and an allocatable band allocatable to a first
path candidate that is included in the plurality of path candidates and that
satisfies a degree of stability requested by the piece of traffic by a first
modulation method; and a selecting step of giving a penalty cost due to
transmission using a band usable by a second modulation method whose
25 degree of stability is lower than the first modulation method to the first
path candidate so that the first path candidate is less likely to be selected,
when the requested band of the piece of traffic is larger than the
allocatable band as a result of the comparison for selecting one path from
among the plurality of path candidates.
6
Advantageous Effects of Invention
[0013]
According to the present invention, it is possible to provide a path
control method, a wireless communication system, a wireless
5 communication device, and a non-transitory computer-readable medium
which are capable of securing efficient traffic accommodation, while
maintaining communication quality.
Brief Description of Drawings
[0014]
10 Fig. 1 is a diagram illustrating a configuration example of a
network according to an exemplary embodiment of the present invention;
Fig. 2 is a configuration diagram of a path control device and of a
communication device according to the exemplary embodiment of the
present invention; and
15 Fig. 3 is a flowchart illustrating a basic operation sequence of the
path control device according to the exemplary embodiment of the present
invention.
Description of Embodiments
[0015]
20 A path control method according to an exemplary embodiment of
the present invention is a method for controlling a communication path by
selecting one path from among a plurality of path candidates with respect
to a specific piece of traffic in a network constituted of a radio link
provided with an adaptive modulation function. The path control method
25 is implemented by a wireless communication system 200 for use in a
network, which is constituted of a path control device 100 and
communication devices 101 to 103, as illustrated in Fig. 1. A path
computation is performed by the path control device 100. The wireless
communication system 200 includes a wired or radio link 191 for
7
connecting between the path control device 100 and the communication
device 101, a radio link 111 for connecting between the communication
device 101 and the communication device 103, a radio link 112 for
connecting between the communication device 101 and the communication
5 device 102, and a radio link 113 for connecting between the
communication device 102 and the communication device 103.
[0016]
The path control device 100 manages the entirety of the network.
The path control device 100 performs all the operations such as receiving a
10 new flow and finishing the flow. The path control device 100
periodically acquires information relating to link quality of a radio link (a
bit error rate, a modulation method in use) from each of the communication
devices 101 to 103. The path control device 100 computes a degree of
stability with respect to each modulation method for each link, and
15 performs a path computation.
[0017]
Fig. 2 is a configuration diagram of the path control device 100 and
of the communication device 101. The path control device 100 is
provided with a control unit 50 having an adaptive modulation function,
20 and a wireless antenna 51 for wirelessly communicating with the
communication device 101. The communication device 101 is provided
with a control unit 55 for selecting a communication path, and a wireless
antenna 56 for wirelessly communicating with the path control device 100
and with the communication devices 102 and 103. The wireless devices
25 102 and 103 also have the same configuration as the wireless device 101.
[0018]
Next, a processing to be carried out by the path control device 100
is described using Fig. 3. The path control device 100 executes cost
computation of each radio link, and thereafter, executes a path computation,
8
on the basis of a result of the cost computation.
The path control device 100 periodically calculates a degree of
stability with respect to each modulation method for each radio link, and
computes a degree of stability with respect to each allocated band.
5 The degree of stability of a link is computed in the same method as
the computation method disclosed in PTL 1, for instance. The degree of
stability Avail(m) of the modulation method m is obtained from a ratio of
time used by the own modulation method m or used by a modulation
method of higher order than the own modulation method m with respect to
10 a predetermined time T.
[0019]
A case is described, in which a relationship between the modulation
methods ml, m2, m3, and m4 is such that ml requested band of traffic + allocated
20 band
This is a case, in which the transmission rate is equal to or larger
than the sum of the requested band of traffic and the allocated band. In
other words, this is a case, in which transmission can be sufficiently
performed by the modulation method Ml.
25 In this case, a difference between the current requested band and
the allocated band, or an inverse of a value based on the usable unused
band is used as a link cost (Step S204). In this example, a difference
between the current requested band and the allocated band, or an inverse of
a value based on the usable unused band is used as a link cost.
10
Alternatively, it is possible to carry out a processing of calculating a link
cost in such a manner that the link cost decreases, as the usable unused
band increases. As a method for calculating a link cost, it is also possible
to obtain the value of a link cost, on the basis of the usable unused band
5 and using a table in which the usable unused band and the value of a link
cost are associated with each other in advance.
[0022]
B) When transmission rate < requested band of traffic +
allocated band
10 This is a case, in which the transmission rate is smaller than the
sum of the requested band of traffic and the allocated band. In other
words, this is a case, in which transmission by the modulation method Ml
is insufficient. In this case, when transmission is performed using the
same path, it is necessary to transmit by a modulation method (e.g. M2)
15 having a lower degree of stability than the modulation method Ml and
capable of accommodating the requested band of traffic. For this reason,
a penalty cost is set so as to apply a weight which makes it difficult to
select a path in path selection, taking into consideration that
communication quality is degraded due to transmission by the modulation
20 method (e.g. M2) having a low degree of stability relative to the
modulation method (e.g. Ml) having a high degree of stability.
In this case, marking is applied to a radio link in which a penalty
cost is set (Step S205). In other words, information representing that a
target radio link is a radio link in which a penalty cost is set is associated
25 with the identification information of the radio link.
[0023]
Next, a path is computed.
4) The link cost of the radio link marked as a radio link in
which a penalty cost is set is set (Step S206).
11
A value obtained by multiplying a tradeoff coefficient x with a
worst value of the link cost set in the other radio links is set as the penalty
cost. When all the radio links are marked as a radio link in which a
penalty cost is set, " 1 " is used as the tradeoff coefficient x.
5 [0024]
The tradeoff coefficient x to be used in the link cost regarding the
penalty cost is computed as a value representing an index indicating how
much the traffic prioritizes a shortest path over reliability. In other
words, the tradeoff coefficient x is computed as a coefficient (weight) to
10 be used when traffic is accommodated in a link whose degree of stability is
lower than the requested degree of stability.
[0025]
The tradeoff coefficient x can be calculated as follows, when
Avail(M2) represents a degree of stability of a usable band in the target
15 link, and Avail(tr) represents a degree of stability requested by traffic,
y=log(l -Avail(M2))-log(l -Avail(tr))=
log((l -Avail(M2))/(l -Avail(tr))
x=pref(y) ... (2)
where M2 is a modulation method of lowest order having a degree of
20 stability required for accommodating the requested band of traffic by the
radio link, and y is a degree of reducing the degree of stability in the target
link. A logarithm is required in order to match the dimensions
numerically in comparing with another link cost. Further, the function
pref(y) is an arbitrary increasing function. The value of the tradeoff
25 coefficient x increases, as the degree of stability of M2 is lowered.
[0026]
The function pref(y) is a factor for use in determining the penalty
cost. The function pref(y) is a value reflecting a degree of stability,
which is determined in accordance with a difference in the relative height
12
between a degree of stability of the modulation method (e.g. Ml) that
satisfies a degree of stability requested by traffic in a path candidate to be
computed, and a degree of stability of the modulation method (e.g. M2)
capable of accommodating the requested band of the traffic in the path
5 candidate. The value reflecting a degree of stability is a value reflecting
a negative factor that affects communication quality by a change from a
modulation method having a sufficiently high degree of stability to a
modulation method having a low degree of stability. It is conceived that
when the difference between the two degrees of stability is large, the
10 negative factor that affects communication quality is large. Therefore,
the value reflecting a degree of stability becomes a large value. As the
difference in the degree of stability between the two modulation methods
increases, the penalty cost increases. As a result, a path candidate other
than the path candidate to be computed is likely to be selected.
15 [0027]
For instance, the following functions are used as an equation for
obtaining the tradeoff coefficient x.
function 1: x=pref(y)=y+2 function 2: x=pref(y)=y+0.5 ... (3)
When the function 1 is used, the penalty cost increases, as
20 compared with the case of using the function 2. Therefore, among the
path candidates, a path whose penalty cost is computed using the function
1 is less likely to be selected, as compared with the other paths.
[0028]
Further, in the pref function, which one of the functions is to be
25 applied is determined in advance for each piece of traffic. Any one of the
functions is notified from the path demander to the path control device
when the path of traffic is set. Alternatively, the path control device may
determine the pref function to be applied in accordance with the types of
data to be transmitted in the traffic (such as voice data or text data).
13
[0029]
5) The path with minimum cost is computed (Step S207)
When a path includes a radio link in which a penalty cost is used in
path setting, the path control device 100 causes the communication devices
5 101 to 103 on the target radio link to mark the piece of traffic using the
path. Then, the communication devices 101 to 103 on the target radio
link set the degree of priority of the marked piece of traffic one rank lower
than the other piece of traffic having the same degree of priority. With
this configuration, when there is a traffic jam between the target piece of
10 traffic and the other piece of traffic, a packet in the target piece of traffic
is not selected, because the degree of priority of the target piece of traffic
is lower than the degree of priority of the other piece of traffic. In other
words, the order of priority of the packet in the target piece of traffic is set
to be low.
15 [0030]
A path control method according to the exemplary embodiment of
the present invention is described referring to a specific example of
computation. In this example, it is assumed that a network is configured
as illustrated in Fig. 1. In other words, a network is constituted of the
20 path control device 100, and the communication devices 101 to 103 under
the control of the path control device 100. The path control device 100
manages the entirety of the network, including all the operations such as
receiving a new flow and finishing the flow. The path control device 100
periodically acquires information relating to link quality of a radio link (a
25 bit error rate, a modulation method in use) from each of the communication
devices 101 to 103. The path control device 100 computes a degree of
stability with respect to each modulation method for each link, and
performs a path computation.
[0031]
14
The wireless communication system 200 includes the wired or radio
link 191 for connecting between the path control device 100 and the
communication device 101, the radio link 111 for connecting between the
communication device 101 and the communication device 103, the radio
5 link 112 for connecting between the communication device 101 and the
communication device 102, and the radio link 113 for connecting between
the communication device 102 and the communication device 103.
[0032]
In the following description, a path that directly connects the
10 communication device 101 and the communication device 103 is called as
"the radio link 111", and a path that connects the communication device
101 and the communication device 103 via the communication device 102
is called as "the radio links 112 and 113". The radio link 111 has the
number of times of hopping of 1, and the radio links 112 and 113 have the
15 number of times of hopping of 2. In this example, as the number of times
of hopping increases, the transmission delay amount increases.
[0033]
Table 1 illustrates a degree of stability and a securable band of each
modulation method for each of the radio links 111, 112, and 113. In the
20 following, as examples of the modulation method, QPSK (Quadrature
Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), and
32QAM (32 Quadrature Amplitude Modulation) are used.
[0034]
[Table 1]
25 Modulation method and degree of stability in radio link
Modulation method
Securable band [Mbps]
Degree of stability [%]
QPSK
40
99.99
16QAM
40
99.9
32QAM
28
99.5
[0035]
15
The following is the degrees of stability requested by the pieces of
traffic, each of which has a degree of priority, with respect to each degree
of priority of traffic in accordance with the degree of stability of each
modulation method i.e. 99.99%, 99.9%, and 99.5%.
5 Degree of priority 1: 99.99%
Degree of priority 2: 99.9%
Degree of priority 3: 99.5%
In other words, the piece of traffic, whose degree of priority is 1 i.e.
the order of priority is highest, requests the degree of stability 99.99% by
10 the modulation method QPSK. Further, the piece of traffic, whose degree
of priority is 2 i.e. the order of priority is second highest, requests the
degree of stability 99.9% by the modulation method 16QAM.
Furthermore, the piece of traffic, whose degree of priority is 3 i.e. the
order of priority is lowest, requests the degree of stability 99.5% by the
15 modulation method 32QAM.
[0036]
A) Path computation 1
A path computation for the piece of traffic whose requested band is
30 Mbps (the degree of priority: 1, the degree of stability: 99.99%), the
20 degree of stability which is possible with modulation method QPSK) is
performed between the radio links 101 to 103. First of all, a modulation
method which satisfies the degree of stability 99.99% is searched in each
link. All the links satisfy the condition that the modulation method
QPSK is usable. Then, it is checked whether a piece of traffic having a
25 high order of priority can be accommodated by the transmission rate of
QPSK in each link. Table 1 shows that there is a sufficiently wide unused
band so that a link cost is computed.
Link cost=l/(unused band that satisfies the specified degree of
stability). The link cost of each link is calculated as follows.
16
(radio link 111, radio link 112, radio link 113): 1/40 ...(4)
[0037]
The cost of a path of the radio links 112 and 113 which connect the
communication device 101 and the communication device 103 via the
5 communication device 102 is 1/40+1/40=2/40.
Further, the cost of a path of the radio link 111 which directly
connects the communication device 101 and the communication device 103
is 1/40. When the costs of the two path candidates are compared, the cost
of the path of the radio link 111 is lower than the cost of the path of the
10 radio links 112 and 113 so that the path of the radio link 111 is selected.
30 Mbps out of 40 Mbps, which can be secured by the modulation method
QPSK in the radio link 111, is allocated to the piece of traffic.
The allocated band of each radio link in a state where the path
computation 1 is completed is as illustrated in Table 2.
15 [0038]
[Table 2]
Allocated band
Link
Allocated band (QPSK)
Allocated band (16QAM)
Allocated band (32QAM)
111
30
0
0
112
0
0
0
113
0
0
0
[0039]
B) Path computation 2
20 Next, a path computation for the piece of traffic whose requested
band is 20 Mbps (the degree of priority: 1, the degree of stability: 99.99%,
the degree of stability which is possible with modulation method QPSK) is
performed. When the link cost is computed, 30 Mbps out of 40 Mbps,
which is the allocated band by the modulation method QPSK, is already
25 used in the radio link 111 by the piece of traffic allocated by the path
17
computation 1. As a result, the requested band 20 Mbps of the piece of
traffic is larger than the unused band 10 Mbps that satisfies the specified
degree of stability (30+20>40). Therefore, a penalty cost is set in the
link cost of the radio link 111.
5 [0040]
A cost obtained by multiplying the maximum value of the link costs
of the other links with the coefficient x is set as the penalty cost to be set
in the radio link 111. The degree of stability of the band (16QAM) usable
in the target link is 99.9%, and the degree of stability requested by the
10 piece of traffic is 99.99%. Therefore, the tradeoff coefficient x when
x=pref(y)=y+2 is used as a pref function is as follows.
pref(log(l-0.999)-log(l-0.9999))=3 ... (5)
Therefore, the penalty link cost to be set in the target link is as follows.
3*1/40=3/40 ... (6)
15 [0041]
The band 40 Mbps remains in the other radio links 112 and 113 for
the modulation method QPSK. Therefore, the link cost of the radio links
112 and 113 is calculated as follows by applying the same computation as
the path computation 1.
20 (radio link 112, radio link 113): 1/40 ...(7)
[0042]
The sum of the costs of the two path candidates is calculated as
follows.
(radio links 112 and 113): 1/40+1/40=2/40 ... (8)
25 (radio link 111): 3/40 ... (9)
When the paths candidates are compared, the path of the radio links
112 and 113 whose cost is smaller is selected. The used bands after the
computation processing in this case are updated as follows.
[Table 3]
18
Used band with respect to each degree of priority
Link
Used band (QPSK)
Used band (16QAM)
Used band (32QAM)
111
30
0
0
112
20
0
0
113
20
0
0
[0043]
When a piece of traffic, in which x=pref(y)=y+0.5 is used as a pref
function, is used as the piece of traffic having the same degree of priority
5 as the other piece of traffic, the sums of the path candidates are
respectively calculated as follows, because the tradeoff coefficient x=1.5.
(radio links 112 and 113): 1/40+1/40=2/40 ... (10)
(radio link 111): 1.5/40 ... (11)
Therefore, in this case, the path of the radio link 111 is selected.
10 [0044]
C) Path computation 3
Next, a path computation of the piece of traffic whose requested
band is 20 Mbps (the degree of priority: 3, the degree of stability: 99.5%,
the degree of stability by the modulation method 32QAM or higher is
15 requested) is performed. There are three unused bands which satisfy the
degree of stability requested by the piece of traffic. The link cost of each
link is computed as follows, using an inverse of a value based on the
unused band.
(radio link 111): l/((40+40+28)-30)=l/78 ...(12)
20 (radio link 112, radio link 113):
l/((40+40+28)-20)=l/88 ... (13)
(radio links 112 and 113): 2/88 ...(14)
(radio link 111): 1/78 ... (15)
As a result of the expressions (14) and (15), the radio link 111
25 whose cost is smaller is selected as the path. When a band whose degree
19
of stability is lowest among the unused bands that satisfy the degree of
stability requested by the piece of traffic is allocated, the allocation status
is as illustrated in Table 4.
[0045]
5 [Table 4]
Used band with respect to each degree of priority
Link
Used band (QPSK)
Used band (16QAM)
Used band (32QAM)
111
30
0
20
112
20
0
0
113
20
0
0
[0046]
D) Path computation 4
Lastly, a path computation of the piece of traffic whose requested
10 band is 20 Mbps (the degree of priority: 1, the degree of stability: 99.99%,
the degree of stability which* is possible with modulation method QPSK) is
performed. The radio link 111 does not satisfy the degree of stability of
the unused band (16QAM), which is requested by the piece of traffic.
Therefore, a penalty cost is set in the radio link 111. The link cost of the
15 radio link 112, 113 is as follows.
(radio link 112, radio link 113): l(40-20) = l/20
... (16)
Therefore, the link cost of the radio links 112 and 113 is 2/20.
[0047]
20 It is assumed that the piece of traffic is a piece of traffic which
prefers a shortest path, in other words, which prioritizes a transmission
speed over stability. In view of the above, x=pref(y)=y+0.5 is set in
advance as a pref function, which calculates a relatively small value as the
penalty cost.
25 Specifically, the penalty cost is as follows.
20
x=pref(log(l-0.999)-log(l-0.9999))=log(l-0.999)-log( 1-0.9999)
+0.5 = 1.5. The penalty cost of the radio link 111 is calculated as
follows.
(radio link 111): 1/20*1.5=3/40... (17)
5 As a result of comparing the sums of the link costs of each path, the
radio link 111 whose sum of the link costs is smallest is selected as a path.
[0048]
Lastly, the used band of each link is as illustrated in Table 5.
[Table 5]
10 Used band with respect to each degree of priority
Link
Used band (QPSK)
Used band (16QAM)
Used band (32QAM)
111
30
20
20
112
20
0
0
113
20
0
0
[0049]
As described above, the path computations make it possible to set a
path whose degree of stability is high for a piece of traffic in which
stability is prioritized, and to set a path whose number of times of hopping
15 is small for a piece of traffic in which delay is prioritized. As an applied
example of the present invention, the invention may be used in a mobile
backhaul network in a mobile phone network.
[0050]
According to the exemplary embodiment, a penalty cost
20 computation is performed individually for each piece of traffic, even when
the pieces of traffic have the same degree of priority. Therefore, it is
possible to set the penalty cost to be low, when the traffic prefers a
shortest path, and it is possible to set the penalty cost to be high, when the
traffic prioritizes stability. Thereby, it is made possible to set a path
25 according to the preference of traffic.
21
[0051]
The present invention is not limited to the aforementioned
exemplary embodiment, but may be modified as necessary, as far as such
modifications do not depart from the gist of the invention. For instance,
5 the invention is also applicable to higher communications standards such
as communications standards of fourth generation or higher (e.g.
LTE-Advanced, IMT-Advanced, WiMAX2).
[0052]

10 As another exemplary embodiment, the function of the path control
device 100 may be implemented by the configuration of the communication
devices 101 to 103.
[0053]
Further, the path control device 100 described in the exemplary
15 embodiment may be implemented, using a semiconductor processing device
including an ASIC (Application Specific Integrated Circuit).
Furthermore, this method may be implemented by causing a computer
system including at least one processor (e.g. a microprocessor, an MPU or
a DSP (Digital Signal Processor)) to execute a program. Specifically, the
20 above configuration is implemented by creating one or more programs
including a command group for causing a computer system to execute an
algorithm relating to bias voltage control, which has been described using
a flowchart and the like, and by supplying the program to the computer.
[0054]
25 The programs can be stored using various types of non-transitory
computer readable media, and can be supplied to a computer. The
non-transitory computer readable media include various types of tangible
storage media. Examples of the non-transitory computer readable media
are a magnetic recording medium (e.g. a flexible disk, a magnetic tape, a
22
hard disk drive), a magneto-optical recording medium (e.g. a
magneto-optical disk), a CD-ROM (Read Only Memory), a CD-R, a
CD-R/W, and a semiconductor memory (e.g. a mask ROM, a PROM
(Programmable ROM), an EPROM (Erasable PROM), a flash ROM, and a
5 RAM (Random Access memory)). Further, the program may be supplied
to a computer by various types of transitory computer readable media.
Examples of the transitory computer readable media include an electrical
signal, a light signal, and an electromagnetic wave. A transitory
computer readable medium is capable of supplying a program to a
10 computer via a wired communication path such as a power line and an
optical fiber, or via a wireless communication path.
[0055]
A part or all of the aforementioned exemplary embodiment may be
described as the following Supplemental Notes. The present invention
15 described by the exemplary embodiment, however, is not limited to the
following.
(Supplemental Note 1)
A path control method for controlling a communication path by
selecting one path from among a plurality of path candidates with respect
20 to a specific piece of traffic in a network constituted of a radio link
provided with an adaptive modulation function, including:
a comparing step of comparing a requested band of the piece of
traffic, and an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
25 stability requested by the piece of traffic by a first modulation method; and
a selecting step of giving a penalty cost due to transmission using a
band usable by a second modulation method whose degree of stability is
lower than the first modulation method to the first path candidate so that
the first path candidate is less likely to be selected, when the requested
23
band of the piece of traffic is larger than the allocatable band as a result of
the comparison for selecting one path from among the plurality of path
candidates.
(Supplemental Note 2)
5 The path control method according to Supplemental Note 1,
wherein
the penalty cost is determined on the basis of a unique value that is
defined in advance with respect to each piece of traffic.
(Supplemental Note 3)
10 The path control method according to Supplemental Note 1 or 2,
wherein
the penalty cost is determined on the basis of a value reflecting a
degree of stability that is determined in accordance with a difference in
relative height between a degree of stability of the first modulation method
15 in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
(Supplemental Note 4)
The path control method according to Supplemental Note 1, further
including:
20 setting a link cost that is determined in accordance with an unused
area of a path candidate with respect to the path candidate having the
unused area capable of accommodating the requested band of the piece, of
traffic, wherein
the penalty cost is calculated by multiplying a tradeoff coefficient
25 with a maximum link cost in the other path candidates, the tradeoff
coefficient being determined on the basis of at least one of a unique value
that is defined in advance with respect to each piece of traffic, and a value
reflecting a degree of stability determined in accordance with a difference
in relative height between a degree of stability of the first modulation
24
method in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
(Supplemental Note 5)
The path control method according to any one of Supplemental
5 Notes 1 to 4, further including:
calculating a degree of stability with respect to each band of the
radio link, on the basis of history information of the modulation methods
used by the radio link in the past.
(Supplemental Note 6)
10 A path control method for controlling a communication path by
selecting one path from among a plurality of path candidates including a
first path candidate as a shortest path, and a second path candidate whose
number of times of hopping is larger than the first path candidate with
respect to a specific piece of traffic in a network constituted of a radio link
15 provided with an adaptive modulation function, including:
a comparing step of comparing a requested band of the piece of
traffic, and an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
stability requested by the piece of traffic by a first modulation method; and
20 a selecting step of giving a penalty cost due to transmission using a
band usable by a second modulation method whose degree of stability is
lower than the first modulation method to the first path candidate so that
the first path candidate is less likely to be selected, when the requested
band of the piece of traffic is larger than the allocatable band as a result of
25 the comparison for selecting one path from among the plurality of path
candidates.
(Supplemental Note 7)
The path control method according to Supplemental Note 6,
wherein
25
the penalty cost is determined on the basis of a unique value that is
defined in advance with respect to each piece of traffic.
(Supplemental Note 8)
The path control method according to Supplemental Note 6 or 7,
5 wherein
the penalty cost is determined on the basis of a value reflecting a
degree of stability that is determined in accordance with a difference in
relative height between a degree of stability of the first modulation method
in the first path candidate, and a degree of stability of the second
10 modulation method in the first path candidate.
(Supplemental Note 9)
A wireless communication system provided with a device for
controlling a communication path by selecting one path from among a
plurality of path candidates with respect to a specific piece of traffic in a
15 network constituted of a radio link provided with an adaptive modulation
function, including:
a comparing means which compares a requested band of the piece of
traffic, with an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
20 stability requested by the piece of traffic by a first modulation method; and
a selecting means which gives a penalty cost due to transmission
using a band usable by a second modulation method whose degree of
stability is lower than the first modulation method to the first path
candidate so that the first path candidate is less likely to be selected, when
25 the requested band of the piece of traffic is larger than the allocatable band
as a result of the comparison for selecting one path from among the
plurality of path candidates.
(Supplemental Note 10)
The wireless communication system according to Supplemental
26
Note 9, wherein
the penalty cost is determined on the basis of a unique value that is
defined in advance with respect to each piece of traffic.
(Supplemental Note 11)
5 The wireless communication system according to Supplemental
Note 9 or 10, wherein
the penalty cost is determined on the basis of a value reflecting a
degree of stability that is determined in accordance with a difference in
relative height between a degree of stability of the first modulation method
10 in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
(Supplemental Note 12)
The wireless communication system according to Supplemental
Note 9, including:
15 setting a link cost that is determined in accordance with an unused
area of a path candidate with respect to the path candidate having the
unused area capable of accommodating the requested band of the piece of
traffic, wherein
the penalty cost is calculated by multiplying a tradeoff coefficient
20 with a maximum link cost in the other path candidates, the tradeoff
coefficient being determined on the basis of at least one of a unique value
that is defined in advance with respect to each piece of traffic, and a value
reflecting a degree of stability determined in accordance with a difference
in relative height between a degree of stability of the first modulation
25 method in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
(Supplemental Note 13)
The wireless communication system according to any one of
Supplemental Notes 9 to 12, further including:
27
calculating a degree of stability with respect to each band of the
radio link, on the basis of history information of the modulation methods
used by the radio link in the past.
(Supplemental Note 14)
5 A wireless communication system provided with a control device
for controlling a communication path by selecting one path from among a
plurality of path candidates including a first path candidate as a shortest
path, and a second path candidate whose number of times of hopping is
larger than the first path candidate with respect to a specific piece of
10 traffic in a network constituted of a radio link provided with an adaptive
modulation function, including:
a comparing means which compares a requested band of the piece of
traffic, with an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
15 stability requested by the piece of traffic by a first modulation method; and
a selecting means which gives a penalty cost due to transmission
using a band usable by a second modulation method whose degree of
stability is lower than the first modulation method to the first path
candidate so that the first path candidate is less likely to be selected, when
20 the requested band of the piece of traffic is larger than the allocatable band
as a result of the comparison for selecting one path from among the
plurality of path candidates.
(Supplemental Note 15)
The wireless communication system according to Supplemental
25 Note 14, wherein
the penalty cost is determined on the basis of a unique value that is
defined in advance with respect to each piece of traffic.
(Supplemental Note 16)
The wireless communication system according to Supplemental
28
Note 14 or 15, wherein
the penalty cost is determined on the basis of a value reflecting a
degree of stability that is determined in accordance with a difference in
relative height between a degree of stability of the first modulation method
5 in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
(Supplemental Note 17)
The wireless communication system according to Supplemental
Note 14, further including:
10 setting a link cost that is determined in accordance with an unused
area of a path candidate with respect to the path candidate having the
unused area capable of accommodating the requested band of the piece of
traffic, wherein
the penalty cost is calculated by multiplying a tradeoff coefficient
15 with a maximum link cost in the other path candidates, the tradeoff
coefficient being determined on the basis of at least one of a unique value
that is defined in advance with respect to each piece of traffic, and a value
reflecting a degree of stability determined in accordance with a difference
in relative height between a degree of stability of the first modulation
20 method in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
(Supplemental Note 18)
A path control device, including:
a control unit provided with an adaptive modulation function; and
25 a wireless antenna which wirelessly communicates with a
communication device, wherein
the control unit controls a communication path by selecting one
path from among a plurality of path candidates with respect to a specific
piece of traffic in a network connected to the communication device by a
29
radio link, and
the path control device further includes:
a comparing means which compares a requested band of the
piece of traffic, with an allocatable band allocatable to a first path
5 candidate that is included in the plurality of path candidates and that
satisfies a degree of stability requested by the piece of traffic by a first
modulation method; and
a selecting means which gives a penalty cost due to
transmission using a band usable by a second modulation method whose
10 degree of stability is lower than the first modulation method to the first
path candidate so that the first path candidate is less likely to be selected,
when the requested band of the piece of traffic is larger than the
allocatable band as a result of the comparison for selecting one path from
among the plurality of path candidates.
15 (Supplemental Note 19)
A non-transitory computer readable medium storing a program
which causes a computer to select one path from among a plurality of path
candidates with respect to a specific piece of traffic in a network
constituted of a radio link provided with an adaptive modulation function,
20 the program causing the computer to execute:
a comparing step of comparing a requested band of the piece of
traffic, and an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
stability requested by the piece of traffic by a first modulation method; and
25 a selecting step of giving a penalty cost due to transmission using a
band usable by a second modulation method whose degree of stability is
lower than the first modulation method to the first path candidate so that
the first path candidate is less likely to be selected, when the requested
band of the piece of traffic is larger than the allocatable band as a result of
30
the comparison for selecting one path from among the plurality of path
candidates.
[0056]
The invention of the present application has been described
5 referring to the exemplary embodiment. The invention of the present
application, however, is not limited by the foregoing description. The
configuration and the details of the invention of the present application
may be modified in various ways comprehensible to a person skilled in the
art within the technical scope of the invention.
10 [0057]
This application claims the priority based on Japanese Patent
Application No. 2012-233493 filed on October 23, 2012, and all of the
disclosure of which is hereby incorporated.
Reference signs List
15 [0058]
50 Control unit
51 Wireless antenna
55 Control unit
56 Wireless antenna
20 100 Path control device
101 Communication device
102 Communication device
103 Communication device
111 Radio link
25 112 Radio link
113 Radio link
191 Radio link
200 Wireless communication system

CLAIMS
[Claim 1]
A path control method for controlling a communication path by
5 selecting one path from among a plurality of path candidates with respect
to a specific piece of traffic in a network constituted of a radio link
provided with an adaptive modulation function, the method comprising:
a comparing step of comparing a requested band of the piece of
traffic, with an allocatable band allocatable to a first path candidate that is
10 included in the plurality of path candidates and that satisfies a degree of
stability requested by the piece of traffic by a first modulation method; and
a selecting step of giving a penalty cost due to transmission using a
band usable by a second modulation method whose degree of stability is
lower than the first modulation method to the first path candidate so that
15 the first path candidate is less likely to be selected, when the requested
band of the piece of traffic is larger than the allocatable band as a result of
the comparison, and selecting one path from among the plurality of path
candidates.
20 [Claim 2]
The path control method according to Claim 1, wherein
the penalty cost is determined on the basis of a predetermined
unique value with respect to each piece of traffic.
25 [Claim 3]
The path control method according to Claim 1 or 2, wherein
the penalty cost is determined on the basis of a value reflecting a
degree of stability that is determined in accordance with a difference in
relative height between a degree of stability of the first modulation method
32
in the first path candidate, and a degree of stability of the second
modulation method in the first path candidate.
[Claim 4]
5 The path control method according to Claim 1, further comprising:
setting a link cost that is determined in accordance with an unused
area of a path candidate with respect to the path candidate having the
unused area capable of accommodating the requested band of the piece of
traffic, wherein
10 the penalty cost is calculated by multiplying a tradeoff coefficient
with a maximum link cost in the other path candidates, the tradeoff
coefficient being determined on the basis of at least one of a predetermined
unique value with respect to each piece of traffic, and a value reflecting a
degree of stability determined in accordance with a difference in relative
15 height between a degree of stability of the first modulation method in the
first path candidate, and a degree of stability of the second modulation
method in the first path candidate.
[Claim 5]
20 The path control method according to any one of Claims 1 to 4,
further comprising:
calculating a degree of stability with respect to each band of the
radio link, on the basis of history information of the modulation methods
used by the radio link in the past.
25
[Claim 6]
A path control method for controlling a communication path by
selecting one path from among a plurality of path candidates including a
first path candidate as a shortest path, and a second path candidate whose
33
number of times of hopping is larger than the first path candidate with
respect to a specific piece of traffic in a network constituted of a radio link
provided with an adaptive modulation function, comprising:
a comparing step of comparing a requested band of the piece of
5 traffic, with an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
stability requested by the piece of traffic by a first modulation method; and
a selecting step of giving a penalty cost due to transmission using a
band usable by a second modulation method whose degree of stability is
10 lower than the first modulation method to the first path candidate so that
the first path candidate is less likely to be selected, when the requested
band of the piece of traffic is larger than the allocatable band as a result of
the comparison, and selecting one path from among the plurality of path
candidates.
15
[Claim 7]
A wireless communication system provided with a device for
controlling a communication path by selecting one path from among a
plurality of path candidates with respect to a specific piece of traffic in a
20 network constituted of a radio link provided with an adaptive modulation
function, comprising:
a comparing means which compares a requested band of the piece of
traffic, with an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
25 stability requested by the piece of traffic by a first modulation method; and
a selecting means which gives a penalty cost due to transmission
using a band usable by a second modulation method whose degree of
stability is lower than the first modulation method to the first path
candidate so that the first path candidate is less likely to be selected, when
34
the requested band of the piece of traffic is larger than the allocatable band,
as a result of the comparison, and selects one path from among the
plurality of path candidates.
5 [Claim 8]
A wireless communication system provided with a control device
for controlling a communication path by selecting one path from among a
plurality of path candidates including a first path candidate as a shortest
path, and a second path candidate whose number of times of hopping is
10 larger than the first path candidate with respect to a specific piece of
traffic in a network constituted of a radio link provided with an adaptive
modulation function, comprising:
a comparing means which compares a requested band of the piece of
traffic, with an allocatable band allocatable to a first path candidate that is
15 included in the plurality of path candidates and that satisfies a degree of
stability requested by the piece of traffic by a first modulation method; and
a selecting means which gives a penalty cost due to transmission
using a band usable by a second modulation method whose degree of
stability is lower than the first modulation method to the first path
20 candidate so that the first path candidate is less likely to be selected, when
the requested band of the piece of traffic is larger than the allocatable band
as a result of the comparison, and select one path from among the plurality
of path candidates.
25 [Claim 9]
A path control device, comprising:
a control unit provided with an adaptive modulation function; and
a wireless antenna which wirelessly communicates with a
communication device, wherein
35
the control unit controls a communication path by selecting one
path from among a plurality of path candidates with respect to a specific
piece of traffic in a network connected to the communication device by a
radio link, and
5 the path control device further comprises:
a comparing means which compares a requested band of the
piece of traffic, with an allocatable band allocatable to a first path
candidate that is included in the plurality of path candidates and that
satisfies a degree of stability requested by the piece of traffic by a first
10 modulation method; and
a selecting means which gives a penalty cost due to
transmission using a band usable by a second modulation method whose
degree of stability is lower than the first modulation method to the first
path candidate so that the first path candidate is less likely to be selected,
15 when the requested band of the piece of traffic is larger than the
allocatable band as a result of the comparison, and selects one path from
among the plurality of path candidates.
[Claim 10]
20 A non-transitory computer readable medium storing a program
which causes a computer to select one path from among a plurality of path
candidates with respect to a specific piece of traffic in a network
constituted of a radio link provided with an adaptive modulation function,
the program causing the computer to execute:
25 a comparing step of comparing a requested band of the piece of
traffic, with an allocatable band allocatable to a first path candidate that is
included in the plurality of path candidates and that satisfies a degree of
stability requested by the piece of traffic by a first modulation method; and
a selecting step of giving a penalty cost due to transmission using a
36
band usable by a second modulation method whose degree of stability is
lower than the first modulation method to the first path candidate so that
the first path candidate is less likely to be selected, when the requested
band of the piece of traffic is larger than the allocatable band as a result of
5 the comparison, and selecting one path from among the plurality of path
candidates.