JP3794471B2 - Wireless channel assignment system in wireless network - Google Patents

Description

上式において、Ｘ(k)skjは、ＳＤペアkの始点ノードｓkから隣接ノードｊに流れるトラヒック量を表す。したがって、これを全ての隣接ノードｊ（ｊ∈Ａsk）について求め、かつ全てのＳＤペアkについて繰り返して総和を求めれば、全てのＳＤペアに対してネットワークが収容するトラヒック（ネットワークのキャパシティ）となる。
そして、本実施形態では前記リンク状態監視装置５により、上記目的関数が最大値を示すときの無線チャネル数Ｓi,jが求められ、これに基づいて、各ノードが自身の各無線リンクに最適な無線チャネルを割り当てる。
本実施形態では、この目的関数を、以下の５つの条件式(1)から(5)を解くことによって求めている。
【００２９】

上式(1)では、左辺はＳＤペアkの始点ノードから全隣接ノードｊ（ｊ∈Ａsk）に流れるトラヒック量、すなわちＳＤペアkについてネットワークに収容されるトラヒックを表す。したがって、上式(1)は、あるノードskを始点するリンクから、すべての終点ノードｊ（ｊ∈Ａsk）に至るリンクのトラヒック量の和が、指定されたトラヒック量Ｄk（過去の測定値による）を超えてはならないという条件を表す。
【００３０】

上式(2)は、あるＳＤペアkに関して、ノードiから流れるトラヒック量とノードiに流れるトラヒックの総和が等しいという条件を表す。
【００３１】

上式(3)は、各無線リンクを流れるトラヒック量がマイナスにならないという条件を表す。
【００３２】

上式(4)は、あるリンクの上り下りで流れるトラヒックの総和は、割り当てられた無線チャネル数×最大転送速度（＝使用可能なリンクの最大伝送容量）を超えないという条件を表す。
【００３３】

上式(5)の左辺は、ノードiにおいて、隣接ノードjとの間に割り当てられるチャネル数を表すので、あるノードiと当該ノードiに隣接するすべての隣接ノード間で使用するチャネル数の総和がノードiで使用可能な総チャネル数を超えないという条件を表す。
【００３４】
各ノードのリンク状態監視装置５は、以上の各式を線形計画問題として解いて前記目的関数Ｓi,jを求めると、この目的関数Ｓi,jに基づいて各無線リンクに割り当てる無線チャネル数を決定して前記ＲＦＴ２およびＬＩＣ３へ通知する。ＲＦＴ２およびＬＩＣ３は、リンク状態監視装置５から前記通知を受け取ると、これに応答して、各無線リンクに割り当てる無線チャネル数を動的に増減させる。
【００３５】
本実施形態によれば、各ノードが自身の各無線リンクに割り当てるＣＨＵ数すなわち無線帯域を、ネットワーク上の他のノードや無線リンクの状態を考慮して動的に増減させるので、ネットワーク上の各無線リンクに対して無線帯域を効率よく割り当てられるようになる。
【００３６】
【発明の効果】
本発明によれば、以下のような効果が達成される。
(1)各無線リンクに対して割り当てる無線チャネル数を動的に増減させることができるので、各無線リンクに対して任意の伝送帯域を割り当てられる。
(2) 各無線リンクに割り当てる無線チャネル数を、各リンクの伝送品質やネットワークのトラヒックに応じて増減させるようにしたので、各リンクに割り当てる帯域を最適化できる。
(3)一部のリンクの通信品質が降雨減衰等により一時的に悪化し、他のリンクのトラヒックが変動すると、トラヒックの変動に応答して各リンクに割り当てられる無線チャネル数が増減されるので、各リンクに割り当てられる伝送帯域が常に最適化される。
(4)全てのＳＤペアについて収容されるトラヒック量の総和が最大となるように、各無線リンクに割り当てられる無線チャネル数を決定するので、ネットワーク全体で無線チャネルの有効利用が可能になる。
【図面の簡単な説明】
【図１】 本発明が適用される無線ネットワークの構成を示した図である。
【図２】 図１の無線メッシュ網の一部を抜き出して示した図である。
【図３】 無線ノードの構成を示したブロック図である。
【図４】 無線帯域装置ＲＦＴ２の機能ブロック図である。
【符号の説明】
１…無線送受信装置，２…無線帯域装置ＲＦＴ，３…リンク制御装置ＬＩＣ，４…経路制御装置ＲＴＣ，５…リンク状態監視装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio channel assignment system in a radio network, and more particularly, a radio suitable for an MP-MP (Multipoint-to-Multipoint) type radio network in which a plurality of distributed radio nodes are connected by radio links. The present invention relates to a channel assignment system.
[0002]
[Prior art]
The mesh-type wireless communication system is configured by distributing and arranging a plurality of wireless nodes that perform wireless communication, and each wireless node is a P-P (Point-to-Point) wireless between a plurality of neighboring wireless nodes. By establishing the link, it is possible to communicate directly or via a plurality of wireless nodes between arbitrary wireless nodes. In the mesh-type wireless communication system, a plurality of wireless nodes are connected to each other by a wireless link, and therefore, MP-MP (Multipoint-) is compared to the conventional PP type or P-MP type (Point-to-Multipoint). It is also called to-multipoint type.
[0003]
Conventionally, when a mesh type wireless communication system is configured by a P-P type radio link, a radio channel as a physical transmission medium is fixedly allocated to each P-P type radio link connecting radio nodes. A constant transmission band was always provided.
[0004]
[Problems to be solved by the invention]
In a communication system using radio, deterioration in radio transmission quality (transmission speed, error rate, etc.) and line disconnection may occur with changes in radio channel quality (CNR) due to rainfall or the like. In general, it has been pointed out that a strong rainfall phenomenon that affects fluctuations in wireless transmission quality is highly dependent on location. Therefore, in a mesh type wireless communication system, it is possible to bypass a wireless link with deteriorated transmission quality and communicate traffic.
[0005]
However, in the conventional mesh wireless communication system, a wireless channel is fixedly assigned to each wireless link. For this reason, it is impossible to effectively assign the radio link band to the detour traffic generated by the fluctuation of the transmission quality in each radio link, and the radio link through which the detour traffic passes can be overloaded.
[0006]
In addition, in data communication such as the Internet, which is currently the mainstream, traffic demand on wireless links varies from wireless link to wireless link due to the uneven distribution of traffic demand between wireless nodes, and this varies with time. Can be considered.
[0007]
Even with such temporal fluctuations in traffic demand, it has been impossible to effectively use the radio link band in the conventional mesh radio communication system. For this reason, when a radio link band is designed based on the maximum traffic demand for each radio link, the capacity becomes excessive in a time zone with little traffic. In addition, when a radio link band is designed based on an average traffic demand, an overload occurs in a time zone with a lot of traffic.
[0008]
An object of the present invention is to solve the above-described problems of the prior art, in 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. The purpose is to optimize the number of radio channels allocated to a link in accordance with network traffic fluctuations.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a wireless channel in a wireless network in which a plurality of wireless nodes are distributed and each wireless node allocates a wireless channel between its own node and another node to establish a wireless link. In the assignment system, the number of radio channels assigned to each radio link is variable.
[0010]
According to the above feature, the number of radio channels allocated to each radio link can be arbitrarily varied 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 INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a radio network to which the present invention is applied. Here, a plurality of fixed radio nodes N are distributed and arranged at intervals of about 1 to 4 km to establish radio links L with each other. A wireless mesh network will be described as an example.
[0012]
FIG. 2 is a diagram showing a part of the wireless mesh network. When attention is paid to the wireless node N, wireless nodes N1, N2, N3, and N4 are arranged adjacent to the wireless node N. FIG. The wireless node N is provided with antennas AT1, AT2, AT3, AT4 having sharp directivities such as parabolic antennas toward the wireless nodes N1, N2, N3, N4.
[0013]
The antennas AT1, AT2, AT3, and AT4 of the wireless node N are opposed to the antennas provided in the adjacent wireless nodes N1, N2, N3, and N4, and establish the wireless links L1, L2, L3, and L4, respectively. To do.
[0014]
FIG. 3 is a block diagram showing a configuration of a main part of a radio communication system mounted on each radio node N, and the same reference numerals as those described above represent the same or equivalent parts. In this embodiment, each wireless node has an equivalent configuration.
[0015]
The radio transmission / reception device 1 includes a plurality of radio transmission / reception units CHU (CHU1 to CHUn), and each radio transmission / reception unit CHU controls one radio channel. The radio band device RFT2 responds to an instruction from the link state monitoring device 5 described later with the radio transmission / reception unit CHU for each of all the radio links (in this embodiment, four radio links L1 to L4) of the own node. Dynamically allocate the specified number. FIG. 4 is a functional block diagram of the radio band device RFT2, in which zero, one or a plurality of CHUs are allocated to the radio links L1 to L4.
[0016]
In response to the instruction from the link state monitoring device 5, the link control device LIC3 dynamically associates each of the radio links L1 to L4 with each CHU and controls the distribution of traffic to each CHU. The route control device RTC4 measures the traffic amount of each of the radio links L1 to L4 and notifies the link state monitoring device 5 of the traffic, and in response to an instruction from the link state monitoring device 5, the traffic transmitted and received by the terminal of its own node , And the traffic forwarding route via the own node.
[0017]
In such a configuration, when attention is paid to traffic input from the radio link L1 and output from the radio link L2 among the traffic relayed through the node N, the data detected by the input antenna AT1 is previously stored in the radio link L1. Are allocated to the CHUs assigned to (in this embodiment, for example, CHU1) by RFT2. When a plurality of CHUs are assigned to the radio link L1, the distribution is made to any one of the CHUs.
[0018]
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 is notified in advance of the relationship between the radio links L1 to L4 and CHU (CHU1 to CHUn). The LIC 3 transfers the data transferred from the CHU 1 to the RTC 4 from the route S 1 previously assigned to the radio link (in this embodiment, the radio link L 1).
[0019]
The RTC 4 recognizes the destination of the received data, and transfers this to the LIC 3 from the path S2 corresponding to the output link (in this embodiment, the wireless link L2). The LIC 3 recognizes a CHU (in this embodiment, for example, CHU 3) that is assigned in advance to the radio link L2, and delivers data to the CHU 3. When the CHU 3 receives and transmits the received data, the RFT 2 distributes the data to the antenna AT2 of the radio link L2 to which the CHU 3 is assigned in advance.
[0020]
On the other hand, in the data sent from the terminal of the own node to the other node, the radio link corresponding to the destination (in this embodiment, for example, the radio link L3) is determined in the RTC4. The RTC 4 transfers data to the LIC 3 from the route S3 corresponding to the wireless link L3. The LIC 3 recognizes the CHU (for example, CHU 5 in this embodiment) assigned to the radio link L 3 and delivers data to the CHU 5. When the CHU 5 receives and transmits data, the RFT 2 distributes the data to the antenna AT3 of the radio link L3 to which the CHU 5 is assigned in advance.
[0021]
In parallel with this, the RTC 4 detects traffic of each of the radio links L1 to L4 and notifies the link state monitoring device 5 of the traffic. The link state monitoring device 5 periodically monitors the traffic volume of each radio link, so that more radio channels (that is, radio transmission / reception unit CHU) are allocated to a radio link with a large traffic volume or transmission. The correspondence relationship between the radio links L1 to L4 and each CHU is notified to the RFT 2 and the LIC 3 so that more radio channels are allocated to a radio link with high quality. In response to the notification, RFT2 and LIC3 dynamically increase or decrease the number of radio channels assigned to each of the radio links L1 to L4.
[0022]
Thus, according to this embodiment, the number of radio channels (number of radio transmission / reception unit CHUs) allocated to each can be dynamically increased or decreased according to the state of each radio link. In other words, according to the present embodiment, it is possible to dynamically increase or decrease the transmission band allocated to each according to the state of each radio link. 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 band assigned to each link can always be optimized.
[0023]
By the way, even if the number of CHUs corresponding to the traffic volume is allocated to a radio link with a large traffic volume and the transmission band is widened, for example, if the link band at the subsequent stage is narrow, the communication speed corresponding to the band cannot be obtained. Further, since adjacent nodes need to allocate the same number of CHUs to the shared link, inconsistency may occur if each node autonomously allocates a CHU to its own radio link.
[0024]
Therefore, in this embodiment, each node grasps the bandwidth of each link of the entire network, and each wireless link is within the range of the number of CHUs held by each node according to network parameters such as traffic demand and wireless transmission quality. Control the bandwidth allocated to.
[0025]
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 transceiver of each radio node: number of CHUs), traffic information between radio nodes Based on the 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 radio channels allocated to each radio link of its own node. To do.
[0026]
Hereinafter, an example in which the method for optimizing the number of radio channels in the present embodiment uses a solution of a linear programming problem will be described. The definitions of the subscripts used in the following functional expressions are as follows.
(1) Subscript i, j
Both are 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 the start node (S) and the 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 link end nodes j (adjacent nodes) starting from node i, and each node is recognized based on a network topology obtained by executing a known routing protocol.
(4) Parameter Bi
This is a set of start point nodes j (adjacent nodes) of a link whose end point is node i, and is recognized based on the network topology in the same manner as the parameter Ai.
(5) Parameter Mi
This is the total number of channels (number of CHUs) that can be used in node i, and is registered in advance for each node.
(6) Parameter Dk
The traffic volume of the SD pair k (end-end), which is determined by the RTC 4 based on past measurement values.
(7) Parameter Cij
This is the maximum transmission rate per radio channel determined by the link line or transmission quality between the node i and node j, and is notified from the radio transmission / reception unit CHU.
(8) Decision variable Si, j
This is the number of radio channels to be used in each link between node i and node j.
[0027]
Here, the traffic volume that the network accommodates 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 SD pair accommodated on each radio link. If each traffic amount X (k) ij is a parameter, it is expressed as the following objective function.
[0028]

In the above equation, X (k) skj represents the amount of traffic flowing from the start node sk of the SD pair k to the adjacent node j. Accordingly, if this is obtained for all adjacent nodes j (jεAsk) and the sum is obtained for all SD pairs k, the traffic (network capacity) accommodated by the network for all SD pairs is obtained. Become.
In this embodiment, the link state monitoring device 5 obtains the number of radio channels Si, j when the objective function shows the maximum value, and based on this, each node is optimal for its own radio link. Assign a radio channel.
In this embodiment, this objective function is obtained by solving the following five conditional expressions (1) to (5).
[0029]

In the above equation (1), the left side represents the amount of traffic flowing from the starting node of the SD pair k to all adjacent nodes j (jεAsk), that is, the traffic accommodated in the network for the SD pair k. Therefore, the above formula (1) is obtained by calculating the sum of traffic amounts of links from a link starting from a certain node sk to all terminal nodes j (j∈Ask) as a specified traffic amount Dk (according to past measurement values). ) Represents a condition that must not be exceeded.
[0030]

The above equation (2) represents a condition that the traffic amount flowing from the node i and the total sum of the traffic flowing to the node i are equal for a certain SD pair k.
[0031]

The above equation (3) represents a condition that the amount of traffic flowing through each wireless link does not become negative.
[0032]

The above equation (4) represents a condition that the sum of traffic flowing in the uplink and downlink of a certain link does not exceed the number of assigned 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 between the adjacent node j and the node i, the total number of channels used between a certain node i and all adjacent nodes adjacent to the node i. Represents the condition that does not exceed the total number of channels available at node i.
[0034]
When the link state monitoring device 5 of each node solves the above equations as a linear programming problem to obtain the objective function Si, j, the number of radio channels to be assigned to each radio link is determined based on the objective function Si, j. Then, the RFT 2 and the LIC 3 are notified. When receiving the notification from the link state monitoring device 5, the RFT 2 and the LIC 3 dynamically increase or decrease the number of radio channels assigned to each radio link in response to the notification.
[0035]
According to the present embodiment, the number of CHUs assigned to each wireless link by each node, that is, the wireless bandwidth is dynamically increased or decreased in consideration of the state of other nodes and wireless links on the network. A radio band can be efficiently allocated to a radio link.
[0036]
【The invention's effect】
According to the present invention, the following effects are achieved.
(1) Since the number of radio channels allocated to each radio link can be dynamically increased or decreased, an arbitrary transmission band can be allocated 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 network traffic, the band allocated to each link can be optimized.
(3) If the communication quality of some links temporarily deteriorates due to rain attenuation, etc., and traffic on other links fluctuates, the number of radio channels assigned to each link will increase or decrease in response to traffic fluctuations. The transmission band allocated to each link is always optimized.
(4) Since the number of radio channels allocated to each radio link is determined so that the total amount of traffic accommodated for all SD pairs is maximized, radio channels can be effectively used throughout the 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. 1 extracted.
FIG. 3 is a block diagram showing 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 ... Path control apparatus RTC, 5 ... Link state monitoring apparatus

Claims (1)

In a radio channel allocation system in a radio network in which a plurality of radio nodes are distributed and each radio node allocates a radio channel between its own node and another node to establish a radio link,
Each wireless node
A plurality of radio transmission / reception units each controlling one radio channel;
Means for periodically monitoring the radio links of the entire radio network and, based on predetermined network parameters, optimizing the correspondence between each radio link of its own node and the radio transmission / reception unit assigned to each radio link;
Means for dynamically allocating a radio channel to each radio link of its own node based on the optimized correspondence relationship;
The means for optimizing the correspondence is:
For each SD pair in the wireless network (a pair of a start node and an end node), the total amount of traffic flowing from the start node to all adjacent nodes is obtained, and this is repeated for all SD pairs to obtain the sum Set the function,
The number of channels of each radio link when the objective function shows the maximum value,
A first condition in which the amount of traffic flowing in each link does not exceed the maximum transmission amount depending on the wireless transmission quality and the number of channels of the link;
A second condition in which the total number of channels that each node allocates between adjacent nodes does not exceed the total number of channels that can be used in each node;
A third condition in which the total amount of traffic flowing from the start node of each SD pair to all adjacent nodes does not exceed the traffic demand between the SD pairs;
A wireless channel assignment system in a wireless network, wherein the wireless channel assignment system is obtained by solving a plurality of conditions including:

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