JP3946652B2 - Routing method and wireless communication system for wireless network - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a routing method and a wireless communication system for a wireless network such as an ad hoc wireless network that performs packet communication in a wireless network such as a wireless LAN provided with a plurality of wireless stations.
[0002]
[Prior art]
In an ad hoc wireless network that supports communication between an unspecified number of people temporarily gathered in a specific area using a wireless line, there is no infrastructure such as a router device of the Internet. Users need to relay and route packets in cooperation.
[0003]
The routing system of an ad hoc wireless network usually employs a single path routing via wireless stations of a plurality of user terminals. However, for example, as disclosed in Non-Patent Document 1, once a set consisting of a plurality of paths is found between a source radio station and a destination radio station, the total capacity of data is divided into a plurality of individual capacities. It may be possible to improve the end-to-end delay time by dividing it into blocks and sending them from the source radio station to the destination radio station via the selected paths. Finally, network congestion and end-to-end delay time can be reduced, and such routing is called “multipath routing”.
[0004]
Non-Patent Document 2 demonstrates that multipath routing can balance network load. Split multi-path routing (SMR) proposed in Non-Patent Document 3 focuses on the construction and maintenance of a plurality of paths that maximize the degree of separation between the paths. Non-Patent Document 4 introduces the concept of a correlation coefficient between a plurality of paths located between a source radio station and a destination radio station.
[0005]
Non-Patent Document 5 discloses a MAC and routing protocol for an ad hoc wireless network. In this disclosure, each wireless station periodically collects its neighbor information, and an adjacent link state table ( Neighborhood Link State Table (NLST)) is created. Non-Patent Document 6 discloses a method for collecting network topology information without increasing overhead. In Non-Patent Document 7, a modified link state routing protocol is configured based on the periodic propagation of local information. The purpose is to make the wireless station recognized in the network topology, as described in Non-Patent Document 8.
[0006]
Further, Non-Patent Document 9 discloses that in a wireless network such as an ad hoc wireless network, a routing table can be updated efficiently even when a wireless station frequently moves, and a stable wireless communication is ensured by securing a stable route. A routing method and a router device for a wireless network capable of performing the above are disclosed. Patent Document 1 and Non-Patent Documents 10 and 11 disclose directional antennas that can be used in each wireless station in an ad hoc wireless network such as Non-Patent Document 9.
[0007]
[Patent Document 1]
JP 2001-24431A.
[Non-Patent Document 1]
SK Das et al., "Improving Quality-of-Service in Ad hoc Wireless Networks with Adaptive Multi-path Routing", Proceedings of the GLOBECOM 2000, San Francisco, California, November 27-December 1, 2000.
[Non-Patent Document 2]
MR Pearlman et al., “On the Impact of Alternate Path Routing for Load Balancing in Mobile Ad Hoc Networks”, Mobihoc 2000, p. 150, 3-10, 2000.
[Non-Patent Document 3]
SJ Lee et al., "Split Multi-path Routing with Maximally Disjoint Paths in Ad Hoc Networks", ICC 2001.
[Non-Patent Document 4]
Kui Wu et al., “On-Demand Multipath Routing for Mobile Ad Hoc Networks”, EPMCC 2001, Vienna, 20th-22nd February 2001.
[Non-Patent Document 5]
S. Bandyopadhyay et al., "An Adaptive MAC Protocol for Wireless Ad Hoc Community Network (WACNet) Using Electronically Steerable Passive Array Radiator Antenna", Proceedings of GLOBECOM 2001, November 25-29, San Antonio, Texas, USA.
[Non-Patent Document 6]
S. Bandyopadhyay et al., "Topology Discovery in Ad Hoc Wireless Networks Using Mobile Agents", Proceedings of MATA 2000, Paris.
[Non-Patent Document 7]
S. Bandyopadhyay et al., "An Adaptive MAC and Directional Routing Protocol for Ad Hoc Wireless Network Using Directional ESPAR Antenna", Proceedings of the ACM Symposium on Mobile Ad Hoc Networking & Computing 2001 (MOBIHOC 2001), Long Beach, California, USA , 4-5 October, 2001.
[Non-Patent Document 8]
R. RoyChoudhury et al., "A Distributed Mechanism for Topology Discovery in Ad hoc Wireless Networks using Mobile Agents", Proceedings of the First Annual Workshop On Mobile Ad Hoc Networking & Computing 2001 (MOBIHOC 2000), Boston, Massachusetts, USA, August 11,2000.
[Non-patent document 9]
Kazunari Masayama et al., “Proposal of Directional Routing Protocol in Wireless Ad Hoc Networks”, Proceedings of IEICE Communication Society Conference, B-5-207, IEICE, September 2001.
[Non-Patent Document 10]
T. Ohira et al., “Electronically steerable passive array radiator antennas for low-cost analog adaptive beamforming,” 2000 IEEE International Conference on Phased Array System & Technology pp. 101-104, Dana point, California, May 21-25, 2000 .
[Non-Patent Document 11]
Satoshi Tano et al., “M-CMA: Digital Signal Processing Algorithm for Adaptive Beamforming by Microwave Signal Processing”, IEICE Technical Report, AP99-62, SAT99-62, pp. 15-22, July 1999.
[0008]
[Problems to be solved by the invention]
However, it has also been shown that employing multiple paths between a source radio station and a destination radio station does not necessarily result in reduced end-to-end delay times. In Non-Patent Document 2, the effect of Alternate Path Routing (APR) in a mobile ad hoc network is examined, and the network topology and channel characteristics (for example, inter-route coupling) increase the gain provided by the APR method. It has been argued that there may be significant limitations.
[0009]
Suppose that there are only two source radio stations ₁ And s ₂ Respectively send the data packet to the destination radio station d ₁ And d ₂ Suppose you are trying to send to. Different node radio stations x ₁ , X ₂ , Y ₁ And y ₂ And there are two paths {s ₁ -X ₁ -Y ₁ -D ₁ } And {s ₂ -X ₂ -Y ₂ -D ₂ }, When communicating, these paths that do not include a common node radio station are referred to as node radio station separation in this specification. A path {s that is separation between node radio stations ₁ -X ₁ -Y ₁ -D ₁ } And {s ₂ -X ₂ -Y ₂ -D ₂ }, The end-to-end delay times of the data packets transmitted via each of these should be independent of each other. However, the node radio station x ₁ And x ₂ And / or y ₁ And y ₂ Are adjacent to each other, it is impossible for two communications to occur simultaneously. This is because the RTS / CTS exchange during data communication is performed at the same time as the node radio station x ₁ Or x ₂ Similarly, the node radio station y ₁ Or y ₂ This is because only either of them can only transmit a data packet. Therefore, the end-to-end delay time between any source radio station and destination radio station does not depend solely on the congestion characteristics of the node radio stations on that path. The pattern of communication in the adjacent area also contributes to this delay time. This is a phenomenon known as inter-route coupling (or route coupling). Inter-route coupling occurs when two routes are placed physically close enough to interfere with each other during data communications.
[0010]
FIG. 13 shows multipath routing according to the prior art, in which when there are two paths between the source radio station S and the destination radio station D, inter-route coupling occurs between the paths. FIG. 2 is a plan layout view of each wireless station and route. Here, between the radio stations S and D, a first path consisting of radio stations {S, x1, x2, D} and a second path consisting of radio stations {S, y1, y2, D} Each path does not have a common node other than the radio stations S and D, and in the present specification, these paths are also referred to as “node radio station separation”. Therefore, the end-to-end delay time of packet transmission through each path should be independent of each other, however, the node radio stations x1 and y1 are in the service area of the source radio station S (ie, the radio signal (Area of transmission possible range) 210 and located close to each other, and the node wireless stations x2 and y2 are located within the service area 211 of the destination wireless station D and located close to each other. As a result, there is an inter-route connection between each path. For this reason, it is impossible to transmit a packet simultaneously on each path. Not only that, the performance of data transmission using these two paths is worse than in the protocol using a single path.
[0011]
FIG. 14 shows multipath routing according to the prior art, in which two paths {S-1a-1b-1c-D including a plurality of inter-route couplings between a source radio station S and a destination radio station D are shown. } And {S-1d-1e-1f-D} are plan views showing the arrangement of radio stations on the path and the antenna radiation pattern.
[0012]
In FIG. 14, the node radio stations 1a and 1d exist in the service area 220 from the source radio station S, and the radio stations S, 1b, 1d, and 1e exist in the service area 221 from the node radio station 1a. The node radio stations 1a, 1c, 1d, 1e, and 1f exist in the service area 222 from the node radio station 1b. In such a case, between the paths {S-1a-1b-1c-D} and {S-1d-1e-1f-D}, the link between the node radio stations 1a and 1d, the node radio stations 1a and 1e There is an inter-route connection as shown by the link between the two, which prevents routing using these two paths.
[0013]
FIG. 15 is a timing chart when a packet is transmitted through the two paths {S-1a-1b-1c-D} and {S-1d-1e-1f-D} in FIG. Actually, referring to FIG. 14 and FIG. 15, when there are two paths coupled between routes between the source radio station S and the destination radio station D, the node radio stations on each path communicate with each other. The state of interference will be described in more detail. Each wireless station is assumed to have an omnidirectional antenna.
[0014]
Referring to FIG. 15, the source radio station S has a time interval T ₀ Data packet P ₁ Is transmitted to the node radio station 1a, and the node radio station 1a ₁ Data packet P ₁ Is transmitted to the node radio station 1b. If each radio station has an omnidirectional antenna, the source radio station S is T ₁ During this time, since the RTS is received from the node radio station 1a, it is necessary to maintain the idle state. Therefore, the source wireless station S has its second packet P ₂ Is the time interval T ₂ It is possible to transmit to the node radio station 1d (first node radio station in the second path) only after In the packet transition as shown in FIG. 15, the destination wireless station D receives the packet in every other time interval. Even if the number of paths between the radio stations S and D is increased more than two, the situation is not improved.
[0015]
As a result, in multipath communication between a pair of radio stations S and D, there is a possibility that node radio stations in these multiple routes are constantly competing for access to the medium they share, Communication performance may be worse than with routing through a single path between the pair of radio stations S and D. Therefore, in this context, it cannot be a sufficient condition for performance improvement that a plurality of routes constituting a multipath are separated from each other. Therefore, when the effort to find the route that is the separation between nodes or the route that maximizes the degree of the separation between nodes as in Non-Patent Documents 3 and 4, is not effective due to the coupling between the routes. There is. Accordingly, it is desirable to provide a more effective method for reducing end-to-end delay times when performing multipath routing in ad hoc wireless networks.
[0016]
The object of the present invention is to solve the above-mentioned problems, and in a wireless network such as an ad hoc wireless network, a wireless network capable of significantly reducing an end-to-end delay time as compared with the prior art. A routing method and a wireless communication system are provided.
[0017]
[Means for Solving the Problems]
A routing method for a wireless network according to a first invention is a routing method for a wireless network that includes a plurality of wireless stations and performs wireless communication between the wireless stations.
Based on the information table indicating the link state between the plurality of radio stations, relays a common radio station including at least one radio station as a relay station between the source radio station and the destination radio station. A first step of searching for a plurality of paths not included as a station;
In the wireless network, a second step of setting the wireless stations on the searched paths as the wireless stations in wireless communication; and
Based on the set wireless stations in communication, calculate the number of other wireless stations in communication in the service area of each wireless station on each path, and By adding the number of radio stations for each path, a correlation coefficient that represents the degree of coupling with respect to radio interference between each path and other communicating radio stations not included in the path itself A routing reference index for searching for the shortest path away from other communicating radio stations without radio wave interference by multiplying the calculated correlation coefficient for each path by the number of hops of the path. A third step of calculating
A fourth step of setting a wireless station included in a path having the largest reference index among the calculated routing reference indices for each path as a wireless station not in communication;
Repeat the third and fourth steps to select a pair of paths having two smaller reference indices as two paths between the source radio station and the destination radio station, and the selection And a fifth step of routing using the two paths.
[0018]
A wireless communication system according to a second aspect of the present invention is a wireless communication system for a wireless network that includes a plurality of wireless stations and performs wireless communication between the wireless stations.
Based on the information table indicating the link state between the plurality of radio stations, relays a common radio station including at least one radio station as a relay station between the source radio station and the destination radio station. Search for multiple paths not included as stations,
In the wireless network, the wireless stations on the searched paths are assumed to be wireless stations in wireless communication, and set.
Based on the set wireless stations in communication, calculate the number of other wireless stations in communication in the service area of each wireless station on each path, and By adding the number of radio stations for each path, a correlation coefficient that represents the degree of coupling with respect to radio interference between each path and other communicating radio stations not included in the path itself A routing reference index for searching for the shortest path away from other communicating radio stations without radio wave interference by multiplying the calculated correlation coefficient for each path by the number of hops of the path. Calculate
Among the calculated routing reference indices for each path, the wireless station included in the path having the largest reference index is set as a wireless station that is not communicating,
The process of calculating the routing reference index for each path and the process of setting the wireless station included in the path having the maximum reference index as a wireless station not in communication are repeated, and two smaller reference indices are obtained. Control means for selecting a pair of paths as two paths between the source radio station and the destination radio station and controlling to route using the selected two paths It is characterized by that.
[0019]
Furthermore, a routing method for a wireless network according to a third invention is a routing method for a wireless network that includes a plurality of wireless stations and performs wireless communication between the wireless stations.
Based on the information table indicating the link state between the plurality of radio stations, relays a common radio station including at least one radio station as a relay station between the source radio station and the destination radio station. Searching for a plurality of paths not included as stations,
In the wireless network, each pair of the searched plurality of paths path Assuming that the upper radio station is a communicating radio station, calculating the number of other communicating radio stations present in the service area of each of the radio stations on each pair of paths, By adding the calculated number of wireless stations in communication for each pair of paths, each of the pair of paths is connected to other wireless stations in communication that are not included in the path itself. By calculating a correlation coefficient representing the degree of coupling with respect to radio wave interference and multiplying the calculated correlation coefficient for each pair of paths by the number of hops of the path, radio interference from other communicating radio stations is obtained. Calculating a routing criterion index for each of the pair of paths to search for the shortest and shortest path;
Of the calculated routing reference indices for each pair of paths, a pair of paths having two smaller reference indices is selected as two paths between the source radio station and the destination radio station. And routing using the two selected paths.
[0020]
Still further, a wireless communication system according to a fourth aspect of the present invention is a wireless communication system for a wireless network that includes a plurality of wireless stations and performs wireless communication between the wireless stations.
Based on the information table indicating the link state between the plurality of radio stations, relays a common radio station including at least one radio station as a relay station between the source radio station and the destination radio station. Search for multiple paths not included as stations,
In the wireless network, each pair of the searched plurality of paths path Assuming that the upper radio station is a communicating radio station, calculating the number of other communicating radio stations present in the service area of each of the radio stations on each pair of paths, By adding the calculated number of wireless stations in communication for each pair of paths, each of the pair of paths is connected to other wireless stations in communication that are not included in the path itself. By calculating a correlation coefficient representing the degree of coupling with respect to radio wave interference and multiplying the calculated correlation coefficient for each pair of paths by the number of hops of the path, radio interference from other communicating radio stations is obtained. Calculate a routing criterion index for each pair of paths to search for the shortest and most closely spaced path;
Of the calculated routing reference indices for each pair of paths, a pair of paths having two smaller reference indices is selected as two paths between the source radio station and the destination radio station. And control means for controlling to perform routing using the two selected paths.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
<First Embodiment>
FIG. 1 is a plan layout view of a plurality of radio stations 1-1 to 1-9 (generally referred to by reference numeral 1) showing the configuration of an ad hoc radio network according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of each radio station 1 in FIG.
[0023]
In the wireless communication system of this embodiment, as shown in FIG. 1, a plurality of wireless stations 1 are present in a plane and each wireless station 1 has a gain, transmission power, and reception sensitivity of the variable beam antenna 101. A predetermined service area determined by parameters such as, and can perform packet communication within the service area. When performing packet communication with the wireless station 1 outside the service area, the wireless station 1 within the service area Is used as a relay station to relay packet data, thereby transmitting the packet data to a desired destination wireless station 1. That is, each radio station 1 includes a router device that performs packet routing, and operates as a source radio station, a relay station, or a destination radio station.
[0024]
The wireless communication system of this embodiment is applied to a packet communication system of an ad hoc wireless network such as a wireless LAN, for example, and includes an omni pattern that is an omnidirectional radiation pattern and a predetermined plane in a horizontal plane centered on the own station. A variable beam antenna 101 capable of selectively switching between a sector beam pattern capable of selectively changing a sector-shaped main beam for each azimuth angle and an exclusive sector pattern capable of forming a null point for each azimuth angle. Prepared,
(A) RE (Reply) signal from an adjacent radio station including a measured value of signal power to interference noise power ratio (hereinafter referred to as SINR) when the adjacent radio station receives an RQ (Request) signal from the own station The maximum SINR is selected for each adjacent radio station based on the SINR obtained in advance based on the SINR viewed from the radio station 1 in the service area for each predetermined azimuth angle in the horizontal plane centered on the own station. And an adjacent link state table (hereinafter referred to as an NLS table) including the affinity, the corresponding azimuth angle, and the data update time. ,
(B) By exchanging topology information of the NLS table (referred to as route information indicating the link state between all radio stations in the ad hoc radio network, the same shall apply hereinafter) between the radio stations, the ad hoc radio network NLS table topology information for all wireless stations 1 in the network is collected, this topology information (including the link state between each wireless station 1), the number of updates of the topology information for each wireless station, A global link state table (hereinafter referred to as a GLS table) including a communication state flag value indicating the wireless station 1 involved in an arbitrary communication process at the time.
Is stored in the database memory 154, and packet signals are routed while controlling the radiation pattern of the variable beam antenna 101 based on the NLS table and the GLS table.
[0025]
In particular, in each radio station 1,
(1) Based on the GLS table, between the source wireless station S and the destination wireless station D, each node includes at least one wireless station as a relay station and does not include a common wireless station as a relay station Searching for multiple paths that are separate; and
(2) In a communication status flag value indicating a wireless station in communication in a wireless network, setting the wireless stations on the searched plurality of paths as wireless stations in communication;
(3) Based on the communication state flag value, calculate the number of other wireless stations in communication within the wireless signal reachable range of the wireless stations on the paths, and calculate the communication in progress The correlation coefficient representing the degree of coupling with respect to the radio wave coherence between each path and other communicating radio stations not included in the path by adding the number of radio stations for each path. A routing reference index for finding the shortest path away from other communicating radio stations without radio wave interference by multiplying the above correlation coefficient of each path by the number of hops of the path. calculating γ;
(4) In the communication state flag value, setting a wireless station included in a path having the largest reference index as a wireless station that is not communicating;
(5) The steps (3) and (4) described above are repeated, and two paths having a smaller routing reference index γ are selected as paths between the source radio station S and the destination radio station D, Performing routing using the selected path.
[0026]
Next, the device configuration of each radio station 1 will be described with reference to FIG. In FIG. 2, a radio station 1 includes a variable beam antenna 101, a directivity control unit 103 for controlling the directivity thereof, a circulator 102, a data packet transmission / reception unit having a data packet transmission unit 140 and a data packet reception unit 130. 104, a traffic monitor unit 105, a line control unit 106, and an upper layer processing unit 107.
[0027]
Transmission signal data for communication in packet format generated by the upper layer processing device 107 that processes data to be transmitted / received is input to the modulator 143 via the transmission buffer memory 142, and the modulator 143 has a predetermined radio frequency. The carrier wave signal is subjected to spread spectrum modulation in accordance with the input communication transmission signal data using a predetermined communication channel spreading code generated by the spread code generator 160 by the CDMA method, and the modulated transmission signal is transmitted at a high frequency. Output to the machine 144. The high-frequency transmitter 144 performs processing such as amplification on the input transmission signal, and then transmits the variable signal from the variable beam antenna 101 to another wireless station 1 via the circulator 102. On the other hand, the communication signal received in the packet format received by the variable beam antenna 101 is input to the high-frequency receiver 131 via the circulator 102, and the high-frequency receiver 131 performs low noise amplification on the input received signal. After executing the above process, the data is output to the demodulator 132. The demodulator 132 demodulates the input received signal by spectrum despreading using the communication channel spreading code generated by the spreading code generator 160 in the CDMA system, and the demodulated received signal data is converted into an upper layer. The data is output to the processing device 107 and also output to the traffic monitor unit 105 for traffic monitoring.
[0028]
In the present embodiment, the variable beam antenna 101 that is a directional antenna is connected to a plurality of antenna elements and a control unit 103 that controls the directivity,
(A) an omni pattern which is an omnidirectional radiation pattern;
(B) For example, as shown in FIG. 3, a sector beam pattern capable of selectively changing a sector-shaped main beam for each predetermined azimuth angle in a horizontal plane centered on the own station;
(C) an exclusive sector pattern capable of forming a null point for each azimuth angle;
Is an antenna that can be selectively switched by electrical control. The variable beam antenna 101 may be, for example, a known phased array antenna device, or may be a variable beam antenna disclosed in Patent Document 1 or Non-Patent Document 11.
[0029]
The traffic monitor unit 105 includes a search engine 152, an update engine 153, a database memory 154, and a clock circuit 155, and performs routing and communication processing described later, and the wireless station 1 communicates with other wireless stations 1. The communication channel to be used in the packet communication is determined, and the spread code generator 160 sends the spread code designation data corresponding to the determined communication channel to the spread code generator 160 via the line control unit 106. The transmission timing control unit is controlled by generating a spreading code corresponding to the designated data and sending the designated data of the time slot corresponding to the determined communication channel to the transmission timing control unit 141 via the line control unit 106. 141 is a communication channel transmission signal by the transmission buffer memory 142 Controls to transmit the signal for the communication channel is transmitted in the corresponding time slot by controlling the writing and reading of over data. The clock circuit 155 counts the current date and time and outputs the information to the management control unit 151 as necessary.
[0030]
The search engine 152 of the traffic monitor unit 105 searches the data in the database memory 154 under the control of the management control unit 151 and returns the searched data to the management control unit 151. The update engine 153 updates data in the database memory 154 under the control of the management control unit 151. Further, the database memory 154 stores an NLS table and a GLS table that is a table for routing.
[0031]
In this embodiment, the effective transmission beam width of the sector beam pattern for changing the directivity so that the gain in the direction of a single communication partner is maximized is set to 30 °, and the variable beam antenna 101 is used. The azimuth angle can be selectively changed every 30 °. The beam width and azimuthal angle of change may be 60 ° or other angles.
[0032]
Next, a method for generating an NLS table will be described. In order to implement an arbitrary multipath routing protocol using the variable beam antenna 101, each radio station has a method of setting its transmission direction for effectively transmitting packets to its selected neighboring radio station. I need to know. Therefore, each wireless station periodically collects its neighbor information and creates an NLS table in each wireless station (see Prior Art Document 5). Each radio station selects an azimuth angle at which the SINR value for each adjacent radio station acquired in advance is maximized, and uses this SINR value as the affinity with the adjacent radio station. Each wireless station extracts the value of the azimuth angle and the affinity for each adjacent wireless station, and generates and updates the NLS table with the current date and time as the update date and time. An example of the NLS table of the radio station 1 is shown in FIG. As is clear from FIG. 4, the NLS table stores the azimuth corresponding to the maximum SINR value, the affinity that is the maximum SINR value, and the update date and time for each adjacent wireless station.
[0033]
A method for acquiring the SINR value for each adjacent radio station will be described. Each wireless station in the ad hoc wireless network periodically collects adjacent wireless station information. The radio station of the local station that collects adjacent radio station information first transmits a broadcast packet in order by a sector beam pattern at an azimuth of 12 directions every 30 degrees. The azimuth angle is 12 directions so that the sector beam pattern covers all 360 degrees. This packet signal is called an RQ signal. In the RQ signal, packet type: RQ, ID of the transmission source radio station of the RQ signal (identification number or identification code, the same shall apply hereinafter), transmission azimuth angle, and standby time are described. Specifically, the standby time is a time until transmission of RQ signals in 12 directions is completed. Next, neighboring neighboring radio stations that have received the RQ signal measure the SINR at the time of reception. Each adjacent radio station temporarily stores this SINR value in the temporary storage table during the standby time, and after the standby time ends, the packet type: RE, the ID of the destination radio station, the ID of the source radio station The SINR value together with the azimuth information described in the RQ signal is returned to the radio station that is the source of the RQ signal as a unicast packet signal. This packet is called an RE signal. When transmitting the RE signal, the same procedure as when transmitting a normal data packet is performed. Then, the radio station that received the RE signal (source of the RQ signal) extracts the source radio station ID of the RE signal (here, the ID of the radio station), azimuth angle information, and SINR information from the RE signal. Here, if a radio station other than the radio station that has transmitted the RQ signal, that is, a radio station that is different from the radio station that has transmitted the RQ signal, receives the RE signal, this is ignored.
[0034]
In this embodiment, in order to measure SINR, BER is measured by transmitting / receiving data packets of a predetermined training pattern to / from other wireless stations 1, and BER for SINR determined by a modulation / demodulation method of wireless communication. Using the characteristic graph, it is converted into SINR. For example, when using the CDMA method, conversion can be performed using a graph of BER characteristics with respect to SINR. For example, when using a QPSK differential detection method, conversion can be performed using a graph of BER characteristics with respect to a predetermined CNR. Can do. That is, whether to use the carrier power to interference noise power ratio (CINR) or SINR depends on the modulation / demodulation method used in the wireless system. In the present invention, any measurement value regarding co-channel interference noise may be used.
[0035]
Next, the GLS table will be described. The GLS table is stored in the database memory 154 in all the radio stations 1 in the ad hoc radio network, and is information on the NLS table of all the radio stations 1 (including radio link information between the radio stations 1). Contains topology information. This is because each wireless station 1 can grasp complete (but approximate) topology information of the entire network by periodically exchanging information in the GLS table in each wireless station 1 with another wireless station. it can. In the context of variable beam antenna 101, the GLS table not only indicates connectivity between any two radio stations, but also each radio station to effectively transmit packets to any selected neighboring radio station. The service area information that needs to be set is also shown. At the same time, each radio station propagates its knowledge about the active node list, ie a list describing the radio station IDs of all active radio stations involved in any communication process at that time (ie information on the communication status flag value). To do. However, it should be noted that the knowledge of each radio station regarding the network topology or the number of active radio stations in the network is only approximate. Here, “active radio station” refers to a radio station that is in a communication state. However, the periodic recalculation of routes by the originating radio station adjusts itself adaptively to changing scenarios.
[0036]
The GLS table includes connectivity between all the radio stations 1, up-to-dateness, and communication state flag values. Here, the connectivity is an item representing the connection strength between radio stations called affinity, and can be obtained from the NLS table of each radio station 1. Also, the newness is a value indicating the number of times each radio station information is updated. When topology information is received from an adjacent radio station, it is updated to the latest information for each radio station compared to the topology information in the receiving radio station. Used to prevent re-transmission from the neighboring radio station after sending the updated topology information to the neighboring radio station and determining the transmission destination of the updated topology information to the neighboring radio station Also used for. The communication status flag value has a value of 1 for a radio station involved in an arbitrary communication process at that time, and a value of 0 for a radio station not involved in the communication process.
[0037]
An example of this GLS table is shown in FIG. The GLS table is a collection of NLS tables of each wireless station 1 in the ad hoc wireless network, and is a set of affinity values from a certain wireless station to a certain wireless station. That is, in the GLS table, as is clear from FIG. 5, a radio station on the transmission side is juxtaposed on the horizontal axis, while a radio station on the reception side is juxtaposed on the vertical axis, and N radio stations are arranged in the radio network. When there is a wireless station 1, the GLS table is an N × N table in which values at individual intersections indicate the affinity (maximum SINR value) from the transmitting wireless station to the receiving wireless station. Furthermore, it has an update count indicating the latestness corresponding to each transmitting-side radio station. Here, the GLS table is generated by periodically exchanging information by transmitting a REN (Renewal) signal including topology information to another radio station, and transmitting the topology information (GLS of a certain radio station) to the radio station. Table) arrives, the GLS table is updated. At that time, it is necessary to compare the GLS table in the topology information with the GLS table of the wireless station that received the topology information. Used, information with a large value of the number of updates is used as a new GLS table. Note that the REN signal includes a packet type: REN, an ID of a destination wireless station, an ID of a source wireless station (here, an ID of the wireless station S), and topology information.
[0038]
Further, an adaptive MAC (Media Access Control) method used in this embodiment will be described. In the present embodiment, each wireless station 1 moves around in a two-dimensional closed space, and shares a common wireless channel when performing wireless communication. Each wireless station 1 is equipped with a variable beam antenna 101 which is an adaptive antenna capable of forming a 360 ° beam / null point, and an effective transmission beam width is 30 °. It is assumed that one radio station 1 cannot perform transmission and reception at the same time, and cannot perform a plurality of different transmissions or a plurality of different receptions. However, it is possible to transmit the same signal in a plurality of directions. When the direction of the interference wave is known, each wireless station that performs reception can form or adjust a null point in order to avoid radio wave interference due to unnecessary signals.
[0039]
First, in the ad hoc wireless network, in the initial idle state, each wireless station 1 waits for transmission / reception with the antenna radiation pattern set as an omni-directional pattern.
[0040]
The IEEE802.11 MAC protocol standard, which is a wireless LAN standard that is currently widely used, uses an RTS-CTS-DATA-ACK exchange procedure in order to realize reliable data communication. On the other hand, in the present system, when the wireless station S wants to perform wireless communication with the wireless station D, the wireless station S first sets the wireless station S including the wireless station D to the adjacent wireless station “from the wireless station S to the wireless station D. Is transmitted in an omni pattern by an RTS (Request-To-Send) signal. The RTS signal includes packet type: RTS, source wireless station ID (in this case, the ID of the wireless station S), and destination wireless station ID, as in the signals prescribed in IEEE 802.11 and the RE signal of this system. (Here, the ID of the wireless station D) and the value of the standby time are included. All adjacent radio stations of the radio station S (the direction to the radio station S is known from the respective NLS table) receive the RTS signal from the radio station S.
[0041]
When the radio station D which is the destination radio station of the RTS signal receives the RTS signal, the radio station D transmits a CTS (Clear−) to notify the radio station S that transmission of the DATA signal (data signal) is permitted. To-Send) signal is returned in an omni pattern. This CTS signal includes the packet type: CTS, the ID of the destination wireless station (here, the ID of the wireless station S), and the value of the standby time.
[0042]
Next, when the wireless station S that is the wireless station that has transmitted the RTS signal receives the CTS signal from the wireless station D that is the destination, the wireless station S transmits the DATA signal. The radio station D as the destination radio station receives the DATA signal, and when the reception is completed normally, returns an ACK (Acknowledgement) signal (acknowledgment signal) to the radio station S as an acknowledgment. The wireless station S receives the ACK signal, completes a series of processes related to one DATA, and returns to the idle state. Here, the DATA signal includes packet type: DATA, source wireless station ID (in this case, ID of wireless station S), destination wireless station ID (in this case, ID of wireless station D), and waiting time value. Contains data to be transmitted. The ACK signal includes a packet type: ACK, a destination wireless station ID (in this case, an ID of the wireless station S), and a waiting time value.
[0043]
On the other hand, when a radio station other than the radio station D (hereinafter referred to as a radio station A) receives the RTS signal, the radio station A is a radio station S that is a radio station that has transmitted the RTS signal based on the NLS table. Azimuth angle information is acquired, and a null point is formed in the direction of the radio station S only during the waiting time described in the RTS signal. Such antenna radiation patterns in which null points are formed in an arbitrary direction are collectively referred to as an exclusive sector pattern.
[0044]
When a CTS signal is received by a device other than the radio station S, a null point is formed for a certain period in the direction of the CTS signal source radio station in the same manner as the RTS signal.
[0045]
The radio station S that has transmitted the RTS signal and the DATA signal and the radio station D that has transmitted the CTS signal operate a timer for a certain time after the transmission. In the case of the radio station S, when a CTS signal is not received within a certain time after transmitting an RTS signal, and when an ACK signal is not received within a certain time after transmitting a DATA signal, the RTS signal is transmitted as a time-out. Redo a series of processing from. On the other hand, if the wireless station D does not receive the DATA signal within a certain time after transmitting the CTS signal, the sector beam pattern to the wireless station S is returned to the omni pattern and becomes an idle state. When the standby time period ends, if there is no other communication in the direction during the standby time period, the null point in that direction in the variable beam antenna 101 is canceled.
[0046]
Furthermore, in the present embodiment, the variable beam antenna 101 that is a directional antenna is utilized to preferentially notify peripheral wireless stations with a low degree of topology information update, thereby maintaining the latest topology information. Uniformity of the degree of update in the surrounding radio stations is ensured while reducing overhead.
[0047]
Hereinafter, a transmission method of the REN signal for updating the GLS table will be described. If the flooding is used to notify each wireless station of the topology information, the overhead becomes large, which may affect normal data transmission. In our previous work, we constructed a modified link state routing protocol based on the periodic propagation of neighbor information of each radio station (see prior art document 7). The purpose is to recognize the radio station in the network topology (see Prior Art Document 8). The main purpose is to collect all topology related information from each radio station in the network without flooding the network with topology update packets, and periodically transfer it to only one neighboring radio station (as update information) ) Distribute.
[0048]
In the mechanism of the present embodiment, each radio station periodically propagates a REN signal including topology information and its knowledge about the active node list to only one neighboring radio station at regular intervals. The radio station on the receiving side of the REN signal updates the topology information and the active node list based on the knowledge and propagates it to other radio stations. In order to reduce the overhead due to the REN signal including the topology information and the active node list, the selection of the target neighboring radio station to which the topology map and the active node list are propagated is a known least-visited-neighbor-first (LVNF) criterion. (For example, refer nonpatent literature 6). Each radio station monitors a metric called recency of its neighboring radio stations to determine which one has received the minimum number of update messages. The adjacent radio station that has received the minimum number of update messages at that time becomes the target radio station for update. Specifically, when a radio station receives a REN signal that is a topology update packet signal, updates the GLS table, and transmits a new REN signal, an update that indicates the latestness of adjacent radio stations that can directly perform radio communication The number of times is compared, and the REN signal is transmitted only to the radio station having the minimum number of updates. The REN signal is transmitted after increasing the number of updates of the transmission destination radio station.
[0049]
Each time the source radio station S desires communication with the destination radio station D, the source radio station S calculates a routing reference index γ for a plurality of inter-node separation routes from the radio stations S to D. From these multiple routes, the source radio station S examines the active node list to maximize the degree of inter-zone separation between radio stations S and D (as described above) and the shortest multipath (ie, minimum Multipath with a routing criterion index γ of. However, due to mobility and slow information penetration, it may not be possible for the originating radio station to fully compute a multipath with the minimum routing criterion index γ between radio stations S and D. is there. In order to improve performance under these circumstances, each source radio station periodically performs its calculation and adaptively modifies its routing decision.
[0050]
In the present embodiment, topology information is distributed to only one adjacent wireless station using a directional antenna using an NLS table, so that the conventional omnidirectional beam is used (Non-Patent Document 6). The overhead can be greatly reduced. In addition, by using the number of updates, it is possible to average the latestness of neighboring wireless stations.
[0051]
Hereinafter, a method for calculating the routing reference index γ for each path when a plurality of paths exist between the source radio station S and the destination radio station D will be described.
[0052]
The influence of inter-route coupling as shown in FIG. 13 and FIG. 14 is significant if a directional antenna (that is, variable beam antenna 101) is used instead of an omnidirectional antenna in each radio station in an ad hoc radio network. Can be dramatically reduced. It has been shown that the use of directional antennas can significantly reduce radio interference, thereby improving the use of the radio medium and consequently improving the network throughput (eg, Non-Patent Document 5). reference.).
[0053]
In the concept of the inter-zone separation route in the wireless medium proposed in the embodiment according to the present invention, when the data communication on one path does not interfere with the data communication on the other path, both paths are separated between zones. Is done. However, even if capturing an inter-zone separation route in an ad hoc wireless network using an omni-directional antenna, or even partially capturing an inter-zone separation route, the coverage area of each wireless station 1 is This is difficult because it is large compared to the case of a directional antenna. When the radio station 1-n forms a transmission beam with the beam angle θ in the horizontal plane and the radius R of the transmission range with respect to the radio station 1-n, the reachable range from the radio station 1-n is the service area A. _n Defined by (θ), θ × R ² Equal to / 2. For an omnidirectional antenna with a beam angle θ = 2π, service area A _n (2π) = πR ² It is. Thus, one way to reduce the service area of a radio station and thus reduce inter-route coupling is to use a directional antenna with a beam angle θ that is significantly less than 360 °.
[0054]
Next, the concept of the node separation route and the zone separation route will be described. Most of the researches on multipath routing in the ad hoc wireless network so far have been conducted on a plurality of separated paths / nodes between a source radio station S and a destination radio station D for effective multipath routing by appropriate load balancing. You are trying to find a path that maximizes the degree of isolation between nodes. Two (or a plurality of three or more) paths between the radio stations S and D are referred to as “inter-node separation” when a common radio station other than the radio stations S and D is not shared. However, due to inter-route coupling in a wireless environment, inter-node separation routes may not be a sufficient condition for improved performance in this context. In this embodiment, the concept of “inter-zone separation route” in a wireless medium is proposed. Here, when data communication on one path does not interfere with data communication on another path, both paths are separated between zones. Called. In other words, two (or more than two) paths between radio stations S and D are called “inter-zone separation” when the inter-route coupling between them is zero.
[0055]
In Non-Patent Document 4, the influence of coupling between routes is measured using a correlation coefficient η. In this document, the correlation coefficient η of the radio station 1-n in the path p ⁿ (P) is defined as the number of active adjacent radio stations of the radio station 1-n that do not belong to the path p (radio links of other radio stations 1 in the service area of the radio station 1-n with respect to the path p. In this case, the active neighboring radio station of the radio station 1-n is active (active) in an arbitrary communication process within the service area of the radio station 1-n at that moment. Defined as a radio station involved (in communication). For example, in FIG. 14, the source radio station S and the destination radio station D communicate using two paths {S-1a-1b-1c-D} and {S-1d-1e-1f-D}. Yes. Therefore, in this context of communication, all radio stations are active radio stations. Here, the active adjacent radio stations of the radio station 1a are {S, 1d, 1e, 1b}. Therefore, the correlation coefficient of the radio station 1a in the path p, that is, the path p {S-1a-1b-1c-D} is η ^a (P) = “the number of active neighboring radio stations not belonging to the path p”, that is, 2.
[0056]
The correlation coefficient η of the path p, that is, η (p) is defined as the sum of the correlation coefficients of all the radio stations 1 in the path p. In other words, the correlation coefficient of the path p is obtained by counting the number of links between a radio station on the path p and a radio station on another path. When the correlation coefficient η (p) = 0, the path p is said to be inter-zone separation with respect to all other active paths. Here, the active path refers to a path that is currently involved in the communication process. Unless correlation coefficient η (p) = 0, path p is related to other active paths by correlation coefficient η.
[0057]
It has been found that the larger the correlation coefficient, the larger the average end-to-end delay time for both paths (Non-Patent Document 4). This is because the greater the correlation coefficient between the two paths, the greater the chance that the two paths will interfere with each other's transmission due to the broadcast characteristics of radio propagation. In addition, the greater the correlation coefficient, the greater the difference in end-to-end delay times along multiple paths. Based on this study, it can be concluded that the success of multipath routing in ad hoc wireless networks depends largely on the correlation coefficient between multiple routes.
[0058]
However, when using an omnidirectional antenna, it is difficult to capture a complete interzone separation route. As shown in FIG. 14, since the node radio stations 1a and 1d are both within the non-directional transmission range of the source radio station S, the RTS from the source radio station S to the node radio station 1a is simultaneously performed by the destination radio station. Disable station D. Similarly, since the node radio stations 1c and 1f are both within the non-directional transmission range of the destination radio station D, the CTS from the destination radio station D disables both the node radio stations 1c and 1f. Thus, when using two multipaths between radio stations S and D and an omnidirectional antenna, the minimum possible correlation coefficient η is 2. This is the minimum correlation coefficient η ^min That's it. More specifically, the minimum correlation coefficient η ^min Is the value of the smallest correlation coefficient among the correlation coefficients of the nodes in the path.
[0059]
In the case of the variable beam antenna 101, it is possible to separate (decouple) these two routes so that they are completely separated between zones. For example, if each radio station 1 in FIG. 6 uses the variable beam antenna 101 and each radio station 1 sets its service area only to the target radio station 1, the path {S-1a-1b- 1c-D} does not affect the communication between the paths {S-1d-1e-1f-D}. 6 shows two paths {S-1a-1b-1c-D} in which the correlation coefficient η is 0 between the source radio station S and the destination radio station D in the ad hoc radio network similar to FIG. And {S-1d-1e-1f-D} are plan views showing the arrangement of the radio stations and the antenna radiation pattern on the path. In the case of the prior art shown in FIG. 14, the correlation coefficient η between the paths {S-1a-1b-1c-D} and {S-1d-1e-1f-D} was 7, whereas Thus, in the case of the present embodiment in FIG. 6, it can be seen that the inter-zone separation is achieved between the two paths. Therefore, the minimum correlation coefficient η when using an omnidirectional antenna ^min For (omnidirectional) = 2, the minimum correlation coefficient η when using a directional antenna ^min (Directivity) = 0.
[0060]
As a result, even if a plurality of inter-zone separation routes having the minimum correlation coefficient are captured using an omnidirectional antenna, the packet arrival rate at the destination wireless station in the best case is 2 × t. _p Each packet is one packet. Where time t _p Is the average delay time per hop for packets of the traffic stream on path p. In this best case, a single traffic stream is assumed from the source radio station S to the destination radio station D in the network with error-free packet transmission. On the other hand, if the variable beam antenna 101 is used, the best packet arrival rate at the destination radio station is the time t. _p Each packet is one packet. The timing charts of FIG. 7 (the present embodiment) and FIG. 15 (prior art) illustrate this point.
[0061]
Referring to FIG. 14, it is assumed that each radio station 1 is provided with an omnidirectional antenna. Further assume that the two paths shown have the smallest correlation coefficient, ie η = 2. This implies that the node radio stations {1a, 1b, 1c} and the node radio stations {1d, 1e, 1f} are separated from each other. T _p Represents a time (timing), and at each time, one packet is transmitted from one radio station to another radio station.
[0062]
Considering FIG. 15, the source radio station S ₀ Data packet P ₁ Is transmitted to the node radio station 1a, and the node radio station 1a transmits the next time interval, that is, T ₁ Data packet P ₁ Is transmitted to the node radio station 1b. In the case of an omnidirectional antenna, the source radio station S ₁ During this time, since the RTS is received from the node radio station 1a, it is necessary to maintain the idle state. Therefore, the source wireless station S has its second packet P ₂ Is the time interval T ₂ It is possible to transmit to the node radio station 1d (first node radio station in the second path) only after FIG. 15 shows packet transitions, and the destination wireless station D receives a packet in every other time interval. Even if the number of paths between the radio stations S and D is increased from two, the situation is not improved when an omnidirectional antenna is used.
[0063]
However, if the variable beam antenna 101 is used, the source radio station S can simultaneously send a packet to the node radio station 1d when the node radio station 1a is sending a packet to the node radio station 1b. FIG. 7 shows two inter-zone separation paths {S-1a-1b-1c-D} and {S-1d-1e- with the minimum correlation coefficient η = 0 in FIG. 6 when using a directional antenna. It is a timing chart when transmitting a packet via 1f-D}. As shown in FIG. 7, when the variable beam antenna 101 is used, the destination radio station D is connected to all time intervals T by two inter-zone separation paths. ₀ , T ₁ , T ₂ , ... receive packets. It has to be noted here that the two inter-zone separation paths when using the variable beam antenna 101 are sufficient to achieve this best case method.
[0064]
Next, multiplex communication by multipath routing when there are a plurality of source radio stations and a plurality of destination radio stations will be described. So far we have considered communication over a single pair of radio stations S and D. However, the situation becomes worse when considering a plurality of pairs of radio stations S and D involved in simultaneous communication. Each pair of radio stations S and D selects two multipaths between them with the smallest possible correlation coefficient η between them. However, in the context of a pair of radio stations S and D, for example, even if two multipaths between radio stations S1 and D1 are inter-zone separation, those paths are, for example, between radio stations S2 and D2. May be coupled (coupled) to other active routes. Therefore, consider all active routes, find the correlation coefficient η associated with each other active route for each, and the degree of inter-zone separation for all active routes in the system as well as for each other It is essential to determine the maximum interzone separation multipath between a pair of radio stations S and D such that is maximized.
[0065]
However, this alone is not sufficient to improve performance. In multipath routing, the path length is another important factor (Non-Patent Document 4). Longer paths with higher hop count H increase end-to-end delay and waste more bandwidth. Therefore, even if the longer bypass route between the pair of radio stations S and D has a small correlation coefficient η, it cannot be very effective in reducing the end-to-end delay time. In order to deal with this problem, the criterion of route selection is to minimize the product of the correlation coefficient η and the number of hops H. When the product value is minimized, the shortest path in which the degree of separation between zones is maximized can be obtained. This product value is referred to as a routing reference index γ (= η × H).
[0066]
However, this is a difficult task in the dynamic environment of ad hoc wireless networks where topology and communication patterns change. An approximate solution to alleviate this difficulty will be discussed later. Here, a mechanism for maximizing the degree of separation between zones in a plurality of pairs of radio stations S and D and finding the shortest multipath is discussed. In this context, the variable beam antenna 101 surpasses the omnidirectional antenna. Indicates effectiveness. To this end, we first assumed a static scenario in the simulation environment. Assume that each radio station is aware of the exact topology and communication pattern in the network. The algorithm shown in the flowchart of FIG. 8 is used to obtain the shortest path in which the degree of zone separation between the radio stations S and D is maximized.
[0067]
FIG. 8 is a flowchart showing the routing and communication processing executed by the management control unit 151 in the traffic monitor unit 105.
[0068]
In step S1 of FIG. 8, with reference to the GLS table, all paths p1 between the source wireless station S and the destination wireless station D whose hop count H is smaller than the maximum value Hmax and which are separated from each other between nodes. Search for pn. In the present embodiment, the maximum value Hmax of the number of hops is set to 5, for example. In step S2, all paths p1,..., Pn are set assuming that they are active (deemed), and the communication state flag value for the node radio stations included in the paths p1,. To do. At this time, the communication state flag value in the GLS table is 1 because the node wireless station on the path searched between the pair of the wireless stations S and D is actually communicating with other than the wireless stations S and D. And the node radio station on the active path between the pair of the source radio station and the destination radio station.
[0069]
In step S3, if the number of paths found in step S2 is two or less, the process proceeds to step S6. If not, then in step S4, the source radio station S and the destination radio station D are referred to for the path pi set (considered) by referring to the GLS table and assuming that each is active in step S2. Calculating a correlation coefficient of the path pi with respect to the set path (assumed) other than the path pi between the source station and the destination radio station other than the radio stations S and D The path pi routing reference index γ is calculated by calculating the correlation coefficient of the path pi for the active path between them and multiplying the sum of the two calculated correlation coefficients by the hop count H of the path pi. . This step S4 is repeated until the routing criteria index γ is calculated for all paths pi set (considered) assuming that they are active. Specifically, as described above, the correlation coefficient is calculated in the other active areas other than the path pi between the source radio station S and the destination radio station D that exist in the service area of each radio station on the path pi. , The number of radio stations on the path set (considered) (that is, the interfering station for the radio station on the path pi), the source radio station other than the radio stations S and D, and the destination radio This is executed by calculating the number of radio stations on the active path between stations (interference stations for radio stations on the path pi) and adding the calculated number of radio stations (interference stations) for each path pi. The
[0070]
Next, in step S5, a path having the maximum routing reference index γ is set assuming that it is not active (deemed), and the communication state flag value for the node radio station included in the path in the GLS table is set to zero. After step S5, again in step S3, it is determined whether or not the number of paths set (considered) assuming that the path is active is 2 or less. When step S3 is NO, repeat step S4 until the number of paths set (considered) assuming that they are active is two (ie, the two with the largest routing criterion index γ) Steps S3 to S5 are repeated (until a path is found). In this iteration, every time the number of paths is reduced by step S5, the recalculation of the routing criterion index in step S4 was set assuming that it is active between radio stations S and D (assumed. This is because the correlation coefficient with other paths related to the path (assumed) set assuming that each path is active changes as the number of paths changes. If three or more paths are searched in step S1 in the flow, it is finally set (considered) that all paths are set to be active in the calculation in step S4. Or different approximations (ie, only two paths are active), or some kind of approximation.
[0071]
When step S3 becomes YES, the process proceeds to step S6. In step S6, node radios included in two paths (referred to as paths pa and pb) set (considered) assuming that they are finally active between the source radio station S and the destination radio station D. The active node list information for the station is transmitted to other node radio stations according to the LVNF standard, and the GLS table of each node radio station is updated. Next, in step S7, the source radio station S communicates with the destination radio station via these paths pa and pb based on relaying the routing information included in the packet header and the like. This communication is not limited to one-way communication from the source wireless station S to the destination wireless station D, and may be bidirectional communication between these two wireless stations. After the communication is completed, in step S8, the communication state flag value for the node wireless stations included in the paths pa and pb in the GLS table is set to 0, and the active node list information for the node wireless stations included in the paths pa and pb is set to the LVNF standard. To the other node radio stations to update the GLS table of each node radio station.
[0072]
As described above, according to the present embodiment, the source radio station S can calculate the routing reference index γ at high speed and execute communication with the destination radio station D.
[0073]
<Second Embodiment>
Hereinafter, a routing method for a wireless network according to the second embodiment of the present invention will be described. This embodiment differs from the first embodiment only in routing and communication processing executed by the management control unit 151 in the traffic monitor unit 105.
[0074]
FIG. 9 is a flowchart showing routing and communication processing executed by the management control unit 151 in the traffic monitor unit 105 in the ad hoc wireless network according to the second embodiment of the present invention.
[0075]
In step S11 of FIG. 9, the communication status flag value in the GLS table is initialized to zero. In step S12, referring to the GLS table, all paths p1,..., Between the source radio station S and the destination radio station D, in which the number of hops H is smaller than the maximum value Hmax and the nodes are separated from each other. Search and find pn. In step S13, two paths pi, pj (a pair of paths) are selected from all the searched paths p1,..., Pn and set assuming that they are active (deemed). The communication status flag value for the node radio stations included in the paths pi and pj in the GLS table is set to 1. At this time, the communication status flag value in the GLS table is 1 because the node radio stations on the paths pi and pj between the pairs of the radio stations S and D are actually communicating with other than the radio stations S and D. And the node radio station on the active path between the pair of the source radio station and the destination radio station. Next, in step S14, the correlation coefficient of the path pi with respect to the path pj is calculated by referring to the GLS table, and the phase of the path pi for the active path between the source radio station and the destination radio station other than the radio stations S and D is calculated. By calculating the number of relationships and multiplying the calculated two types of correlation coefficients by the number of hops H of the path pi, the routing reference index γ of the path pi _{i, j} Calculate Specifically, as described above, the correlation coefficient is calculated by a radio station on the path pj existing in the service area of each radio station on the path pi (ie, an interfering station for a radio station on the path pi) And the number of radio stations on the active path between the source radio station and the destination radio station other than the radio stations S and D (interference stations for radio stations on the path pi), and the calculated radio This is performed by adding the number of stations (interfering stations).
[0076]
Similarly in step S15, the correlation coefficient of the path pj with respect to the path pi is calculated with reference to the GLS table, and the phase of the path pj for the active path between the source radio station and the destination radio station other than the radio stations S and D is calculated. By calculating the number of relations and multiplying the sum of the two calculated correlation coefficients by the number of hops H of the path pj, the routing reference index γ of the path pj _{j, i} Calculate Next, in step S16, the routing reference index γ _{i, j} And γ _{j, i} The communication state flag value for the node radio stations included in the paths pi and pj in the GLS table is set to zero. Steps S13 to S16 are repeated until it is determined in step S17 that the routing reference index γ has been calculated for all combinations of paths p1,..., Pn. When step S17 is NO, the process returns to step S13 to regard another pair of path pairs as active, calculate the routing reference index γ, and when step S17 is YES, proceed to step S18. .
[0077]
In step S18, a pair of paths (hereinafter referred to as paths pa and pb) corresponding to the minimum routing reference index γ is selected, and communication state flag values for the node radio stations included in the paths pa and pb in the GLS table. Set to 1. In step S19, the active node list information for the node radio stations included in the paths pa and pb is transmitted to other node radio stations according to the LVNF standard, and the GLS table of each node radio station is updated. Next, in step S20, the source radio station S communicates with the destination radio station via these paths pa and pb based on relaying the routing information included in the packet header and the like. After completion of communication, in step S21, the communication state flag value for the node radio stations included in the paths pa and pb in the GLS table is set to 0, and the active node list information for the node radio stations included in the paths pa and pb is set to the LVNF standard. To the other node radio stations to update the GLS table of each node radio station.
[0078]
In order to compare the amount of calculation of routing and communication processing according to the first and second embodiments, consider a case where eight paths are searched in step S1 and step S11. In the first embodiment, when step S4 is executed for the first time, the correlation coefficient η is calculated for the eight paths, the path having the maximum routing criterion index γ is regarded as inactive in step S5, and step S4 is When executing for the second time, the correlation coefficient η is calculated for 7 paths, and the path having the maximum routing reference index γ is regarded as not active in step S5, and the process is repeated until the number of paths reaches 2. Therefore, the calculation amount can represent 8 + 7 + 6 + 5 + 4 + 3 = 33. On the other hand, in the second embodiment, since it is necessary to execute steps S14 and S15 for all pairs of paths among the eight paths, the calculation amount is reduced. ₈ C ₂ X2 = 56.
[0079]
According to the routing and communication processing of this embodiment, the amount of calculation increases compared to the first embodiment, but an approximation like the routing and communication processing of the first embodiment (see step S4 in FIG. 8). Therefore, the routing reference index γ can be calculated more accurately than in the first embodiment.
[0080]
【Example】
FIG. 10 is a graph showing a correlation coefficient η with respect to the number of wireless stations when an omnidirectional antenna is used in the ad hoc wireless network of FIG.
[0081]
The inventors have used simulation to confirm that it is much easier to use a variable beam antenna 101 to capture a set of two interzone separation paths than to use an omnidirectional antenna. We conducted a survey. In this investigation, radio stations were randomly arranged in a 1000 × 1500 area at a predetermined density. The source radio station and the destination radio station were randomly selected such that they were separated from each other by a plurality of hops. First, it is assumed that all the radio stations 1 are provided with variable beam antennas 101 having a fixed service area. It is assumed that the transmission zone angle of the beam formed by each variable beam antenna 101 is 60 °. Two inter-zone separation routes were found between the selected source radio station and destination radio station. If two inter-zone separation routes are not available for the source and destination radio station pair, another source and destination radio station pair was selected. Next, assuming that each radio station has an omnidirectional antenna, in the case of the variable beam antenna 101, the correlation coefficient η between these two routes, which is the separation between zones. _omni Was calculated. This experiment was repeated for 25 source and destination radio station pairs. As described above, in each case, the correlation coefficient η when the variable beam antenna 101 is used. _dir Is zero and the correlation coefficient η with an omnidirectional antenna _omni Have calculated about. Next, the correlation coefficient η _omni The average value of was obtained. Next, the same experiment was repeated by changing the distribution density of the radio stations.
[0082]
FIG. 10 shows the result of the simulation described above. As the number of radio stations in the system increases, the correlation coefficient η _omni The average value of is also increasing. However, the correlation coefficient η when the variable beam antenna 101 is provided. _dir Is zero in all cases. This is because even if the variable beam antenna 101 is used even at different radio station densities, it is possible to capture the inter-zone separation path, but these inter-zone separation paths when using the variable beam antenna 101 are omnidirectional. This means that a high correlation coefficient is obtained when a sex antenna is substituted.
[0083]
Next, a simulation result regarding multiplex communication using multipath routing when there are a plurality of source radio stations and a plurality of destination radio stations will be described.
[0084]
FIG. 11 is a graph showing the average value of the routing reference index γ for the multipath between the source radio station S and the destination radio station D with respect to the number of simultaneous communications in the ad hoc radio network of FIG. The simulation begins by finding the shortest path that maximizes the degree of separation between the two zones between a single pair of radio stations S and D. Next, the number of pairs of radio stations S and D is increased by one, and the shortest path with the maximum degree of zone separation in the newly added pair of radio stations S and D is calculated. Recalculate the multipath routing reference index γ in the S and D pair and observe the effect of multiple simultaneous communications on the value of the multipath routing reference index γ in the first pair of wireless stations S and D.
[0085]
This experiment is repeated using several sets of pairs of radio stations S and D and both the variable beam antenna 101 and the omnidirectional antenna. The results shown in FIG. 11 show that the increase of the routing reference index γ is quite abrupt when using an omnidirectional antenna. This is because, as the number of radio stations S and D pairs in the system increases, the inter-route coupling for other active routes of a particular radio station S and D pair is a variable beam antenna in the case of an omnidirectional antenna. It implies that it increases much faster than 101.
[0086]
Next, simulation results regarding the performance of multipath routing using the variable beam antenna 101 are shown. FIG. 12 is a graph showing an average value of end-to-end delay times with respect to the number of simultaneous communications in the ad hoc wireless network of FIG.
[0087]
Due to mobility and slow information penetration, it is impossible for the source radio station to completely calculate the shortest multipath with the maximum degree of interzone separation between radio stations S and D. There is a case. In order to improve performance under these circumstances, each source radio station periodically performs its calculation and adaptively modifies its routing decision. The simulation environment we have implemented incorporates this point, uses omnidirectional antennas and variable beam antennas 101 to increase the number of simultaneous communications, and packets between a set of selected radio stations S and D pairs. The average end-to-end delay time was observed. The timing assumptions are the same as described above. FIG. 12 shows the result. The unit of the vertical axis is an average required time when one packet is transmitted from one wireless station to another wireless station in one hop. The result shows that as the number of simultaneous communications increases, the average end-to-end delay time per packet increases significantly more when the omnidirectional antenna is used than when the variable beam antenna 101 is used. Show. This is a natural consequence of the phenomenon shown in FIG. 11, and it is concluded that the routing performance using multiple paths is significantly improved using the variable beam antenna 101 than using the omnidirectional antenna. be able to.
[0088]
As described above, according to the embodiment of the present invention, the effect of a directional antenna on multipath routing was investigated, and its effectiveness was compared with multipath routing using an omnidirectional antenna. In conclusion, it can be said that the routing performance using a plurality of paths is significantly improved by using a directional antenna as compared with the case of using an omnidirectional antenna. By applying multipath routing technology to ad hoc wireless networks, the impact of unreliable wireless links and constantly changing topologies can be reduced. In addition, in an ad hoc wireless network, it is possible to facilitate end-to-end delay time reduction and load balancing.
[0089]
【The invention's effect】
As described above in detail, according to the routing method or the wireless communication system for the wireless network according to the present invention, based on the information table indicating the link state between the plurality of wireless stations, the source wireless station and the destination Search for a plurality of paths that include at least one radio station as a relay station and do not include a common radio station as a relay station with the radio station,
In the wireless network, the wireless stations on the searched paths are assumed to be wireless stations in wireless communication, and set.
Based on the set wireless stations in communication, calculate the number of other wireless stations in communication in the service area of each wireless station on each path, and By adding the number of radio stations for each path, a correlation coefficient that represents the degree of coupling with respect to radio interference between each path and other communicating radio stations not included in the path itself A routing reference index for searching for the shortest path away from other communicating radio stations without radio wave interference by multiplying the calculated correlation coefficient for each path by the number of hops of the path. Calculate
Among the calculated routing reference indices for each path, the wireless station included in the path having the largest reference index is set as a wireless station that is not communicating,
The process of calculating the routing reference index for each path and the process of setting the wireless station included in the path having the maximum reference index as a wireless station not in communication are repeated, and two smaller reference indices are obtained. A pair of paths is selected as two paths between the source radio station and the destination radio station, and control is performed so that routing is performed using the two selected paths.
[0090]
Further, according to the routing method or the wireless communication system for the wireless network according to another invention, based on the information table indicating the link state between the plurality of wireless stations, the source wireless station and the destination wireless station A plurality of paths including at least one radio station as a relay station and not including a common radio station as a relay station,
In the wireless network, each pair of the searched plurality of paths path Assuming that the upper radio station is a communicating radio station, calculating the number of other communicating radio stations present in the service area of each of the radio stations on each pair of paths, By adding the calculated number of wireless stations in communication for each pair of paths, each of the pair of paths is connected to other wireless stations in communication that are not included in the path itself. By calculating a correlation coefficient representing the degree of coupling with respect to radio wave interference and multiplying the calculated correlation coefficient for each pair of paths by the number of hops of the path, radio interference from other communicating radio stations is obtained. Calculate a routing criterion index for each pair of paths to search for the shortest and most closely spaced path;
Of the calculated routing reference indices for each pair of paths, a pair of paths having two smaller reference indices is selected as two paths between the source radio station and the destination radio station. Then, control is performed so that routing is performed using the two selected paths.
[0091]
Therefore, based on the information table showing the link status between multiple wireless stations, a pair of paths is searched with a smaller amount of calculation compared to the prior art on the basis of the minimum correlation coefficient and the shortest hop count. Thus, multipath routing can be performed, and at this time, the end-to-end delay time can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a plan layout view of a plurality of radio stations 1-1 to 1-9 constituting an ad hoc radio network according to a first embodiment of the present invention.
2 is a block diagram showing an internal configuration of each radio station 1 in FIG. 1. FIG.
FIG. 3 is a diagram illustrating an example of a sector beam pattern of the variable beam antenna 101 of FIG.
4 is a diagram showing an example of an adjacent link state table (NLS table) stored in the database memory 154 of FIG. 2; FIG.
5 is a diagram showing an example of a global link state table (GLS table) stored in the database memory 154 of FIG. 2. FIG.
6 shows two paths {S-1a-1b-1c-D} in which the correlation coefficient η is 0 between the source radio station S and the destination radio station D in the ad hoc radio network similar to FIG. And {S-1d-1e-1f-D} are plan views showing the arrangement of the radio stations and the antenna radiation pattern on the path.
7 is a timing chart when a packet is transmitted via the two paths {S-1a-1b-1c-D} and {S-1d-1e-1f-D} in FIG. 6;
FIG. 8 is a flowchart showing a routing and communication process executed by the management control unit 151 in the traffic monitor unit 105 of FIG.
9 is a flowchart showing routing and communication processing executed by the management control unit 151 in the traffic monitor unit 105 of FIG. 2 in the ad hoc wireless network according to the second embodiment of the present invention.
10 is a graph showing a correlation coefficient η with respect to the number of wireless stations when an omnidirectional antenna is used in the ad hoc wireless network of FIG.
11 is a graph showing an average value of a routing reference index γ for multipath between a source wireless station S and a destination wireless station D with respect to the number of simultaneous communications in the ad hoc wireless network of FIG. 1;
12 is a graph showing an average value of end-to-end delay times with respect to the number of simultaneous communications in the ad hoc wireless network of FIG.
FIG. 13 shows multipath routing according to the prior art, in which two paths {S-x1-x2-D} and {S-y1-y2-D between a source radio station S and a destination radio station D } Is a plane layout diagram of each wireless station and route on the path, showing that inter-route coupling occurs between the paths.
FIG. 14 shows multipath routing according to the prior art, in which two paths {S-1a-1b-1c-D including a plurality of inter-route couplings between a source radio station S and a destination radio station D; } And {S-1d-1e-1f-D} are plan views showing the arrangement of the radio stations on the path and the antenna radiation pattern.
15 is a timing chart when a packet is transmitted via the two paths {S-1a-1b-1c-D} and {S-1d-1e-1f-D} in FIG.
[Explanation of symbols]
1, 1-1 to 1-9, 1a to 1f, S, D ... wireless station,
101 ... Variable beam antenna,
102 ... circulator,
103 ... Direction control unit,
104 ... packet transmission / reception unit,
105 ... Traffic monitor section,
106 ... line control unit,
107 ... upper layer processing apparatus,
130: Packet receiver,
131 ... high frequency receiver,
132: demodulator,
133: Receive buffer memory,
140 ... packet transmitter,
141. Transmission timing control unit,
142 ... transmission buffer memory,
143 ... modulator,
144 ... high frequency transmitter,
151... Management control unit,
152 ... Search engine,
153 ... Update engine,
154 ... Database memory,
155 ... Clock circuit,
160 ... spreading code generator,
200 to 204: Service area.

Claims (4)

For a wireless network that includes a plurality of radio stations each having a variable beam antenna that can be changed by selecting a sector-shaped main beam for each predetermined azimuth angle centered on its own station, and performing radio communication between the radio stations a routing method,
The signal power to interference noise power ratio for each azimuth angle between the radio stations is measured at each radio station using the variable beam antenna, and each of the above has the maximum signal power to interference noise power ratio. The link state between the wireless stations is obtained by acquiring the link state between the wireless stations at the azimuth angle (hereinafter referred to as the link state between the wireless stations) and exchanging the link state between the wireless stations. Is stored in the storage device of each wireless station, and based on the stored information table representing the link state between the wireless stations, at least one between the transmitting wireless station and the destination wireless station A first step of searching for a plurality of paths including a radio station as a relay station and not including a common radio station as a relay station;
In the wireless network, a second step of setting the wireless stations on the searched paths as the wireless stations in wireless communication; and
Based on the set wireless stations in communication, calculate the number of other wireless stations in communication in the service area of each wireless station on each path, and By adding the number of radio stations for each path, a correlation coefficient that represents the degree of coupling with respect to radio interference between each path and other communicating radio stations not included in the path itself A routing reference index for searching for the shortest path away from other communicating radio stations without radio wave interference by multiplying the calculated correlation coefficient for each path by the number of hops of the path. A third step of calculating
A fourth step of setting a wireless station included in a path having the largest reference index among the calculated routing reference indices for each path as a wireless station not in communication;
The above third and fourth steps are repeated, and a pair of paths having two smaller reference indices are selected as two paths between the source radio station and the destination radio station, and the selection is performed. A routing method for a wireless network, comprising: a fifth step of routing using the two paths and using the variable beam antenna. For a wireless network having a plurality of wireless stations each having a variable beam antenna that can be changed by selecting a sector-shaped main beam for each predetermined azimuth angle centered on the own station, and performing wireless communication between the wireless stations a wireless communication system,
Measure the signal power to interference noise power ratio for each azimuth angle between the radio stations in the radio stations using the variable beam antenna, and each of the above having the maximum signal power to interference noise power ratio The link state between the wireless stations is obtained by acquiring the link state between the wireless stations at the azimuth angle (hereinafter referred to as the link state between the wireless stations) and exchanging the link state between the wireless stations. Is stored in the storage device of each wireless station, and based on the stored information table indicating the link state between the wireless stations, at least one between the transmitting wireless station and the destination wireless station is stored. Search for a plurality of paths including a radio station as a relay station and not including a common radio station as a relay station,
In the wireless network, the wireless stations on the searched paths are assumed to be wireless stations in wireless communication, and set.
Based on the set wireless stations in communication, calculate the number of other wireless stations in communication in the service area of each wireless station on each path, and By adding the number of radio stations for each path, a correlation coefficient that represents the degree of coupling with respect to radio interference between each path and other communicating radio stations not included in the path itself A routing reference index for searching for the shortest path away from other communicating radio stations without radio wave interference by multiplying the calculated correlation coefficient for each path by the number of hops of the path. Calculate
Among the calculated routing reference indices for each path, the wireless station included in the path having the largest reference index is set as a wireless station that is not communicating,
The process of calculating the routing reference index for each path and the process of setting the wireless station included in the path having the maximum reference index as a wireless station not in communication are repeated, and two smaller reference indices are obtained. A pair of paths is selected as two paths between the source radio station and the destination radio station, and routing is performed using the selected two paths and the variable beam antenna. A wireless communication system comprising control means for controlling the wireless communication system. A wireless network that includes a plurality of wireless stations each including a variable beam antenna that can be selected and changed by selecting a sector-shaped main beam for each predetermined azimuth angle centered on its own station, and performing wireless communication between the wireless stations. A routing method for
Measure the signal power to interference noise power ratio for each azimuth angle between the radio stations in the radio stations using the variable beam antenna, and each of the above having the maximum signal power to interference noise power ratio The link state between the wireless stations is obtained by acquiring the link state between the wireless stations at the azimuth angle (hereinafter referred to as the link state between the wireless stations) and exchanging the link state between the wireless stations. Is stored in the storage device of each wireless station, and based on the stored information table representing the link state between the plurality of wireless stations, between the source wireless station and the destination wireless station, Searching for a plurality of paths including at least one radio station as a relay station and not including a common radio station as a relay station;
In the wireless network, the wireless stations on each pair of paths in all combinations of the plurality of searched paths are set assuming that the wireless stations are communicating, and the wireless stations on the pair of paths are By calculating the number of other communicating wireless stations existing in the service area of each wireless station, and adding the calculated number of communicating wireless stations for each pair of paths, For each pair of paths, a correlation coefficient representing the degree of coupling with respect to radio wave coherence with other communicating radio stations not included in the path itself is calculated, and the phase for each pair of paths calculated above is calculated. Calculating a routing reference index for each of the pair of paths for searching for the shortest path separated from other communicating radio stations without radio wave interference by multiplying the number of relations by the number of hops of the path When,
Of the calculated routing reference indices for each pair of paths, a pair of paths having two smaller reference indices is selected as two paths between the source radio station and the destination radio station. And routing using the two selected paths and using the variable beam antenna. A wireless network that includes a plurality of wireless stations each including a variable beam antenna that can be changed by selecting a sector-shaped main beam for each predetermined azimuth angle centered on its own station, and performing wireless communication between the wireless stations. A wireless communication system for
Measure the signal power to interference noise power ratio for each azimuth angle between the radio stations in the radio stations using the variable beam antenna, and each of the above having the maximum signal power to interference noise power ratio The link state between the wireless stations is obtained by acquiring the link state between the wireless stations at the azimuth angle (hereinafter referred to as the link state between the wireless stations) and exchanging the link state between the wireless stations. Is stored in the storage device of each wireless station, and based on the stored information table indicating the link state between the wireless stations, at least one between the transmitting wireless station and the destination wireless station is stored. Search for a plurality of paths including a radio station as a relay station and not including a common radio station as a relay station,
In the wireless network, the wireless stations on each pair of paths in all combinations of the plurality of searched paths are set assuming that the wireless stations are communicating, and the wireless stations on the pair of paths are By calculating the number of other communicating wireless stations existing in the service area of each wireless station, and adding the calculated number of communicating wireless stations for each pair of paths, For each pair of paths, a correlation coefficient representing the degree of coupling with respect to radio wave coherence with other communicating radio stations not included in the path itself is calculated, and the phase for each pair of paths calculated above is calculated. By multiplying the number of relations by the number of hops of the path, calculate a routing reference index for each of the pair of paths for searching for the shortest path that is separated from other communicating radio stations without radio wave interference,
Among the calculated routing reference indices for each pair of paths, a pair of paths having two smaller reference indices is selected as two paths between the source radio station and the destination radio station. And a control means for controlling to perform routing using the two selected paths and using the variable beam antenna.

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