JP2002353974A - Wireless channel assignment system in wireless network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless channel assignment system, that optimizes number of wireless channels assigned to each wireless link by increasing/ decreasing the number depending on traffic fluctuations in a wireless network and transmission quality of each wireless link in the wireless network, where a plurality of wireless nodes are arranged in a distribution way and each wireless node sets up a wireless link among a plurality of adjacent wireless nodes. SOLUTION: In the wireless channel assignment system in the wireless network, in which a plurality of the wireless nodes are arranged distributedly and each wireless node sets up a wireless link among a plurality of adjacent wireless nodes, a radio frequency terminal RFT 2 (and link controller LIC 3) causes dynamic increase/decreases in the number of wireless channels (wireless transmission reception unit CHU) assigned to wireless links L1, L2, etc., on the basis of the supervision result of the wireless network by a link state supervisory device 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless channel allocation system in a wireless network, and more particularly to an MP-MP (Multipoint-to-Multipoint) type in which a plurality of distributed wireless nodes are connected by wireless links. Wireless channel allocation system suitable for a wireless network.

[0002]

2. Description of the Related Art A mesh type wireless communication system is configured by distributing a plurality of wireless nodes for performing wireless communication, and each wireless node is located between a plurality of neighboring wireless nodes in a PP (Point-to-Point) manner. -Point) establishes a wireless link, enabling communication between any wireless nodes directly or via a plurality of wireless nodes. In a mesh-type wireless communication system, since a plurality of wireless nodes are connected by a wireless link, an MP-type is compared with a conventional PP type or P-MP type (Point-to-Multipoint).
It is also called MP (Multipoint-to-Multipoint) type.

Conventionally, when a mesh wireless communication system is configured by PP wireless links, each PP wireless link connecting wireless nodes has a fixed wireless channel as a physical transmission medium. Assigned, and a constant transmission band was always provided.

[0004]

In a communication system using wireless communication, deterioration of wireless transmission quality (transmission speed, error rate, etc.) and disconnection of a line occur due to a change in wireless channel quality (CNR) due to rainfall or the like. I can do it. In general, it is pointed out that a strong rainfall phenomenon that affects wireless transmission quality fluctuation largely depends on a place. Therefore, in the mesh-type wireless communication system, it is possible to bypass the wireless link of which transmission quality has been degraded and pass traffic.

[0005] However, in the conventional mesh-type radio communication system, a radio channel is fixedly allocated to each radio link. For this reason, it is impossible to effectively allocate the radio link band to the detour traffic generated due to the fluctuation of the transmission quality in each radio link, and the radio link through which the detour traffic passes may be overloaded.

In data communication such as the Internet, which is currently the mainstream, traffic demands on wireless links differ from one wireless link to another due to uneven distribution of traffic demand between wireless nodes. May fluctuate.

[0007] Even with such temporal fluctuations in traffic demand, it has been impossible for a conventional mesh-type wireless communication system to effectively use a wireless link band.
For this reason, when the radio link band is designed based on the maximum traffic demand for each radio link, the capacity becomes excessive during a time period when traffic is small. Also, if the radio link bandwidth is designed based on the average traffic demand,
Overload occurs during periods of heavy traffic.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a wireless network in which a plurality of wireless nodes are distributed and each wireless node establishes a wireless link with a plurality of neighboring wireless nodes. Another object of the present invention is to optimize the number of radio channels allocated to each radio link in accordance with network traffic fluctuation.

[0009]

In order to achieve the above-mentioned object, the present invention provides a wireless communication system in which a plurality of wireless nodes are distributed and arranged.
In a wireless channel assignment system in a wireless network in which each wireless node assigns a wireless channel between its own node and another node to establish a wireless link, the number of wireless channels assigned to each wireless link is variable.

According to the above feature, the number of radio channels allocated to each radio link can be arbitrarily changed according to the traffic on the network and the transmission quality of each link, so that the transmission band of each radio link can be optimized.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a wireless network to which the present invention is applied.
Here, a wireless mesh network in which a plurality of fixed wireless nodes N are dispersedly arranged at intervals of about 1 to 4 km and wireless links L are mutually established will be described as an example.

FIG. 2 is a diagram showing a part of the wireless mesh network extracted. When attention is paid to a wireless node N, wireless nodes N1, N2, N3 and N4 are arranged adjacent thereto. The wireless node N has wireless nodes N1, N
Antennas AT1, AT2, AT3, and AT4 having sharp directivity such as a parabolic antenna are provided for 2, N3, and N4, respectively.

Each of the antennas AT1, AT of the radio node N
2, AT3 and AT4 are adjacent wireless nodes N1, N
2, N3, and N4, respectively, and establish wireless links L1, L2, L3, and L4, respectively.

FIG. 3 is a block diagram showing a configuration of a main part of a radio communication system mounted on each radio node N. The same reference numerals as those described above denote the same or equivalent parts. In the present embodiment, each wireless node has an equivalent configuration.

The wireless transmitting / receiving device 1 includes a plurality of wireless transmitting / receiving units CHU (CHU1 to CHUn), and each wireless transmitting / receiving unit CHU controls one wireless channel.
The wireless band device RFT2 responds to the instruction from the link state monitoring device 5 described below to the wireless transmission / reception unit CHU for each of the wireless links (the four wireless links L1 to L4 in this embodiment) of the own node. Dynamically allocate as many as you have. FIG. 4 is a functional block diagram of the radio band apparatus RFT2. Zero, one, or a plurality of CHUs are assigned to each of the radio links L1 to L4.

The link control device LIC3 responds to an instruction from the link state monitoring device 5 to transmit the wireless links L1 to L1.
4 is dynamically associated with each CHU and traffic distribution control to each CHU is performed dynamically. Route control device RTC4
Measures the amount of traffic on each of the wireless links L1 to L4 and notifies the link state monitoring device 5, and in response to an instruction from the link state monitoring device 5, the traffic transmitted and received by the terminal of the own node and the own node To control the traffic transfer route via

In such a configuration, focusing on traffic input from the radio link L1 and output from the radio link L2 among the traffic relaying the node N, the data detected by the input antenna AT1 is determined in advance. RFT2 is assigned to the CHU (for example, CHU1 in the present embodiment) assigned to the wireless link L1. When a plurality of CHUs are assigned to the radio link L1, the channel is allocated to any one of the CHUs.

The CHU 1 to which the data has been distributed receives this and transfers it to the LIC 3. The link state monitoring device 5 notifies the LIC 3 of the relationship between the wireless links L1 to L4 and the CHUs (CHU1 to CHUn) in advance. LI
The C3 transfers the data transferred from the CHU1 to the RTC4 from the route S1 previously allocated to the wireless link (the wireless link L1 in this embodiment).

The RTC 4 recognizes the destination of the received data,
This is output to the output link (the wireless link L2 in this embodiment).
Is transferred to the LIC3 from the path S2 corresponding to. LIC3
Is C assigned to the radio link L2 in advance.
The HU (in this embodiment, for example, CHU3) is recognized, and data is delivered to this CHU3. When the CHU 3 receives and transmits the received data, the RFT 2
Antenna A of wireless link L2 to which U3 is assigned
Data is distributed to T2.

On the other hand, in the data transmitted from the terminal of the own node to the other node, the wireless link (for example, the wireless link L3 in the present embodiment) corresponding to the destination is determined by the RTC 4. The RTC 4 transfers data from the route S3 corresponding to the wireless link L3 to the LIC 3. LI
C3 is the CHU assigned to the radio link L3
(In the present embodiment, for example, CHU5),
Deliver the data to HU5. When the CHU 5 receives and transmits the data, the RFT 2 distributes the data to the antenna AT3 of the wireless link L3 to which the CHU 5 is assigned in advance.

In parallel with this, the RTC 4 detects traffic on each of the radio links L1 to L4 and notifies the link status monitoring device 5. The link state monitoring device 5 periodically monitors the traffic volume of each radio link, and allocates or transmits more radio channels (that is, radio transmission / reception units CHU) to radio links having a large traffic volume. For high quality wireless links,
The RFT 2 and the LIC 3 are notified of the correspondence between the wireless links L1 to L4 and each CHU so that more wireless channels are allocated. RFT2 and LIC3 are:
In response to the notification, the number of wireless channels assigned to each of the wireless links L1 to L4 is dynamically increased or decreased.

As described above, according to the present embodiment, the number of radio channels (the number of radio transmission / reception units CHU) assigned to each radio link can be dynamically increased or decreased according to the status of each radio link. In other words, according to the present embodiment,
According to the state of each wireless link, the transmission band assigned to each can be dynamically increased or decreased. Therefore,
Even if the communication quality of some links temporarily deteriorates due to rain attenuation or the like, and the traffic of other links fluctuates, the transmission bandwidth allocated to each link can always be optimized.

By the way, for example, even if the number of CHUs corresponding to the traffic volume is allocated to a radio link having a large traffic volume and the transmission band is widened, a communication speed corresponding to the band can be obtained if the subsequent link band is narrow. I can't. Also,
Adjacent nodes share the same number of CHUs on the shared link.
Therefore, inconsistency may occur if each node autonomously assigns a CHU to its own radio link.

Therefore, in the present embodiment, each node grasps the bandwidth of each link of the entire network, and within the range of the number of CHUs held by each node, according to network parameters such as traffic demand and radio transmission quality. Controls the bandwidth allocated to each wireless link.

In order to perform such radio link band control, in this embodiment, a mesh type radio communication system configuration (radio node, radio link configuration, radio transmission / reception device of each radio node: CHU number), , And transmission quality information of each radio link (maximum transmission capacity per radio channel in each radio link),
The link state monitoring device 5 of each node optimizes the number of wireless channels allocated to each wireless link of the own node.

Hereinafter, an example of the method of optimizing the number of wireless channels in the present embodiment using a solution to a linear programming problem will be described. The definition of each subscript used in each of the following functional expressions is as follows. (1) Subscripts i and j are both node IDs, and i and j are adjacent nodes. (2) Subscript k This is an ID (k = 1, 2,..., K) that defines a set (SD pair) of a start node (S) and an end node (N). However, in each SD pair k, sk is a start node and dk is an end node. (3) Parameter Ai A set of end nodes j of links starting from node i (adjacent nodes). Each node is recognized based on a network topology obtained by executing a known routing protocol. (4) Parameter Bi A set of start nodes j (adjacent nodes) of links ending with node i, which are recognized based on the network topology in the same manner as the parameters Ai. (5) Parameter Mi Total number of channels available at node i (number of the CHUs)
Is registered in advance for each node. (6) Parameter Dk is the traffic volume of SD pair k (end-to-end),
The RTC 4 determines based on past measurements. (7) Parameter Cij is the maximum transmission rate per radio channel determined by the line or transmission quality of the link between node i and node j,
This is notified from the wireless transmission / reception unit CHU. (8) Decision variable Si, j This is the number of radio channels to be used on each link between node i and node j.

Here, the traffic volume accommodated in the network for all SD pairs on the network is the number of radio channels Si, j to be used in each radio link (i, j) and the traffic volume accommodated in each radio link. Traffic volume X for each SD pair
If (k) ij is a parameter, it is expressed as the following objective function.

[0028] In the above equation, X (k) skj is the starting node sk of the SD pair k.
Represents the amount of traffic flowing from the node to the adjacent node j. Therefore, if this is obtained for all adjacent nodes j (j∈Ask) and repeated for all SD pairs k to obtain the sum, the traffic (capacity of the network) accommodated by the network for all SD pairs is obtained. Become. In the present embodiment, the link status monitoring device 5
Thus, the number of wireless channels Si, j when the objective function indicates the maximum value is obtained. Based on this, each node allocates an optimal wireless channel to its own wireless link.
In the present embodiment, this objective function is represented by the following five conditional expressions
It is found by solving (1) to (5).

[0029] In the above equation (1), the left side represents the amount of traffic flowing from the start node of the SD pair k to all adjacent nodes j (j∈Ask), that is, the traffic accommodated in the network for the SD pair k. Therefore, the above equation (1) indicates that, from a link starting at a certain node sk, all end nodes j (j∈Ask)
Represents a condition that the sum of the traffic amounts of the links leading to the above must not exceed the designated traffic amount Dk (based on past measured values).

[0030] The above equation (2) represents a condition that, for a certain SD pair k, the amount of traffic flowing from the node i is equal to the sum of the traffic flowing to the node i.

[0031] The above equation (3) represents a condition that the traffic volume flowing through each wireless link does not become negative.

[0032] The above equation (4) represents a condition that the sum of the traffic flowing in the uplink and the downlink of a certain link does not exceed the number of allocated radio channels × the maximum transfer rate (= the maximum transmission capacity of the usable link).

[0033] Since the left side of the above equation (5) represents the number of channels allocated to the adjacent node j at the node i, a certain node
This represents a condition that the sum of the number of channels used between i and all adjacent nodes adjacent to the node i does not exceed the total number of channels available at the node i.

The link state monitoring device 5 of each node solves each of the above equations as a linear programming problem and solves the objective function Si, j.
Is calculated, the number of radio channels to be allocated to each radio link is determined based on the objective function Si, j, and the RFT2
And LIC3. RFT2 and LIC3
Receives the notification from the link state monitoring device 5,
In response, the number of radio channels allocated to each radio link is dynamically increased or decreased.

According to the present embodiment, the number of CHUs that each node allocates to its own radio link, that is, the radio band,
Since the number is dynamically increased and decreased in consideration of the state of other nodes and wireless links on the network, a wireless band can be efficiently allocated to each wireless link on the network.

[0036]

According to the present invention, the following effects are achieved. (1) Since the number of radio channels assigned to each radio link can be dynamically increased or decreased, an arbitrary transmission band can be assigned to each radio link. (2) Since the number of radio channels allocated to each radio link is increased or decreased according to the transmission quality of each link or the traffic of the network, the bandwidth allocated to each link can be optimized. (3) If the communication quality of some links temporarily deteriorates due to rainfall attenuation and the traffic of other links fluctuates, the number of radio channels allocated to each link increases or decreases in response to traffic fluctuations. The transmission band allocated to each link is always optimized. (4) Since the number of wireless channels allocated to each wireless link is determined so that the total amount of traffic accommodated for all SD pairs is maximized, wireless channels can be effectively used in the entire network.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a wireless network to which the present invention is applied.

FIG. 2 is a diagram showing a part of the wireless mesh network of FIG.

FIG. 3 is a block diagram illustrating a configuration of a wireless node.

FIG. 4 is a functional block diagram of a radio band device RFT2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wireless transmission / reception apparatus, 2 ... Wireless band apparatus RFT, 3 ... Link control apparatus LIC, 4 ... Route control apparatus RTC, 5 ... Link state monitoring apparatus

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shinobu Namba 2-1-1-15 Ohara, Kamifukuoka-shi, Saitama Inside KDDI Laboratory Co., Ltd. (72) Shinichi Nomoto 2-1-1 Ohara, Kamifukuoka-shi, Saitama No. 15 F-term in KDI Research Institute (reference) 5K033 AA01 CA12 CB06 DA17 5K067 AA11 BB21 DD51 EE63

Claims (4)

[Claims] 1. A wireless channel allocation system in a wireless network in which a plurality of wireless nodes are distributed and allocated, and each wireless node allocates a wireless channel between the own node and another node to establish a wireless link. A wireless channel assignment system in a wireless network, wherein the number of assigned wireless channels is variable. 2. The wireless channel assignment system according to claim 1, wherein the number of wireless channels assigned to each wireless link is dynamically increased or decreased according to a predetermined parameter of the network. 3. The wireless channel assignment system according to claim 2, wherein the predetermined parameter is at least one of transmission quality of each wireless link and traffic fluctuation of the wireless network. 4. Determining the number of radio channels allocated to each radio link so that the total amount of traffic flowing between each SD pair (a pair of a source node and a destination node) in the radio network is maximized. Claim 2
Or a wireless channel assignment system in the wireless network according to 3.