KR100364037B1 - Method and system for setting relay path between mobile unit and radio base station - Google Patents

Abstract

The relay routing system includes a plurality of wireless base stations, mobile units, wireless relay units, and base station controllers. Wireless base stations have a communication area. The mobile unit performs wireless communication with wireless base stations by a code division multiple access scheme. The base station controller compares the traffic of the wireless base station and establishes a path between the mobile unit disposed in the communication area of the first wireless base station with high traffic and the second wireless base station with low traffic. Also disclosed is a relay routing method.

Description

METHOD AND SYSTEM FOR SETTING RELAY PATH BETWEEN MOBILE UNIT AND RADIO BASE STATION}

The present invention relates to a digital cellular system using a CDMA (code division multiple access) scheme, and more particularly, to a method and system for establishing a relay path between a mobile unit and a wireless base station.

In the CDMA scheme, the received field strength of a wireless base station that the mobile unit can hand off during a call is measured. The paths are sequentially connected in order from the largest to the lowest received field strength in a wireless base station having a received field strength higher than a predetermined threshold. In addition, the connected path is disconnected when the received field strength becomes lower than the threshold.

However, the conventional routing method in the digital cellular system using the CDMA method has the following problems.

First, since the communication capacity is determined only within the area of the wireless base station, the number of paths per wireless base station is limited to a fairly low value. This makes it impossible to use frequencies effectively.

Secondly, since the wireless base station to which the path is connected is determined according to the strength of the pilot signal, the mobile unit can connect the path only to the wireless base station in the vicinity.

In addition, in the CDMA scheme, since a plurality of mobile units use the same frequency, the mobile unit located near the wireless base station outputs weak transmit power, and the mobile unit located far from the wireless base station outputs strong transmit power, Power control is performed so that mutual interference is suppressed. This CDMA scheme is a multipath scheme in which each mobile unit communicates with multiple wireless base stations. This approach works to maintain high communication quality across all call paths.

A mobile unit located near a wireless base station where calls are concentrated can increase the output level causing interference by trying to improve the call quality with a strong received field strength. Therefore, it is inevitable that the received field strength causes interference with other mobile units. As a result, the call quality between the wireless base station and each of the mobile units is significantly degraded.

It is an object of the present invention to provide a method and system for establishing a relay path between a mobile unit and a wireless base station, which is designed to improve call quality in a wireless base station where calls are concentrated.

In order to achieve the above object, a relay path setting system according to the present invention includes a plurality of wireless base stations having a communication area, a mobile unit for performing wireless communication with a wireless base station by a code division multiple access scheme, and between wireless base stations. And a base station control means for comparing the traffic of the installed radio relay unit, the base station, and for establishing a path between the mobile unit located in the communication area of the first radio base station with high traffic and the second radio base station with low traffic.

1 is a block diagram showing a schematic configuration of a relay path setting system according to a first embodiment of the present invention.

2 is a block diagram showing a schematic configuration of a relay route setting system according to a second embodiment of the present invention;

3 is a block diagram illustrating a base station controller and a wireless relay unit of FIG.

FIG. 4 is a flowchart showing a relay path setting operation performed by the path setting control unit and the wireless relay unit setting control unit in FIG. 3. FIG.

<Explanation of symbols for the main parts of the drawings>

1: base station controller

2, 3, 4, 5: wireless base station

6: mobile unit

7: wireless relay unit

7a, 7b: antenna

11, 12, 13: wireless transmission path

21, 31, 41, 51: communication area

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 shows a schematic configuration of a relay route setting system according to a first embodiment of the present invention. According to FIG. 1, a plurality of radio base stations including radio base stations 2 and 3 having communication areas 21 and 31 are connected to the base station controller 1. Among the plurality of radio base stations, neighboring radio base stations 2 and 3 constitute one group. The base station controller 1 checks the traffic difference between the wireless base stations 2 and 3 constituting one group, and sets the path using a wireless relay unit to be described later in order to distribute the load. The mobile unit 6 is one of a plurality of mobile units located in the communication area 21 of the radio base station 2.

A radio relay unit 7 having two antennas, i.e., a strong directional antenna 7a and a non-directional antenna 7b, is provided between the radio base stations 2,3. The antenna 7a is set corresponding to the radio base stations 2 and 3 and has a fixed direction to the radio base stations 2 and 3. The radio relay unit 7 communicates with these radio base stations 2 and 3 by directing the antenna 7a to the radio base stations 2 and 3, and simultaneously with the mobile unit 6 in the vicinity through the antenna 7b. In this way, the relay operation between the radio base stations 2 and 3 and the mobile unit 6 is performed.

Reference numeral 11 denotes a radio transmission path between the radio base station 2 and the mobile unit 6, and reference numeral 12 denotes a radio transmission path between the mobile unit 6 and the radio relay unit 7. FIG. 13 denotes a radio transmission path between the radio base station 3 and the radio relay unit 7.

Next, the path setting operation of the path setting system having the above-described configuration will be briefly described. The base station controller 1 sets a path consisting of the radio transmission paths 12 and 13 through the radio relay unit 7 so that the mobile unit 6 located in the area of the radio base station 2 with high traffic C12 is located. Enables communication with the wireless base station 3 with low traffic C13. By this operation, the output power from the mobile unit 6 is reduced to reduce interference with other mobile units.

This operation will be described in detail below. The base station controller 1 determines the error rates Er11, Er12, and Er13 of the traffic C12, C13 of the radio base stations 2, 3 and the radio transmission paths 11, 12, 13 from the radio base stations 2, 3; Acquire. The base station controller 1 detects the wireless base station 2 having the maximum traffic from the wireless base stations in the group and the wireless base station 3 having the minimum traffic located near the wireless base station 2.

According to a command from the base station controller 1, the communication by the radio base station 3 in the communication area 31 is affected by the radio base station 3 transmitting / receiving a test signal for the radio relay unit 7. The size is checked. The base station controller 1 calculates the difference in the received electric field strength between the wireless base station 3 and the wireless base station 2 according to the test signal output and compares the calculated difference with the threshold value.

If this difference is greater than the threshold value, the radio relay unit 7 transmits a control signal to the radio base station 3 and the mobile unit 6 so that the radio base station 3 and the mobile unit 6 with low traffic are low. The path is set. Subsequently, the base station controller 1 receives an error rate Er11 of the radio transmission path 11 and an error in the radio transmission paths 12 and 13 from the mobile unit 6 to the radio base station 3 through the radio relay unit 7. Compare rate Er (12 + 13). When the comparison determines that the radio transmission paths 12 and 13 are valid, the path passing through the radio relay unit 7 has a predetermined threshold for receiving path strength R3 at the radio relay unit 7 for path separation. Used until lower.

According to the invention, the base station controller 1 first checks the traffic difference between the wireless base stations 2, 3, and then sets the path using the wireless relay unit 7 to distribute the load. This makes it possible to reduce the received electric field strength R2 in the communication area 21 of the radio base station 2 where the load is concentrated, thereby improving the call quality.

2 shows a configuration of a relay route setting system according to a second embodiment of the present invention. 2, a plurality of radio base stations including radio base stations 2, 3, 4, 5 having communication areas 21, 31, 41, and 51 are connected to the base station controller 1. The neighboring radio base stations 2-5 form one group. The base station controller 1 checks the traffic difference between the wireless base stations constituting one group, and sets the path using a wireless relay unit which will be described later to distribute the load. The mobile unit 6 is one of a plurality of mobile units located in the communication areas 21, 31 of the radio base stations 2, 3.

The radio relay unit 7 having the strong directional antennas 7a and the undirected antennas 7b are provided at almost equal distances from the radio base stations 2-5. The number of antennas 7a installed may be less than the number of radio base stations 2-5. The base station controller 1 controls the directionality of these antennas in the direction of the radio base stations 2-5. The radio relay unit 7 communicates with one of the radio base stations 2-5 by directing the antenna 7a to the radio base station 2-5, and simultaneously with the mobile unit 6 in the vicinity via the antenna 7b. By communicating, the communication between the mobile unit 6 and one of the radio base stations 2-5 is relayed.

It should be noted that directional control can be done in all directions of the wireless base station 2-5, and that only one antenna 7a may be sufficient.

Reference numerals 11 and 12 denote radio transmission paths between the base stations 2 and 3 and the mobile unit 6, and reference numeral 13 denotes radio transmissions between the mobile unit 6 and the radio relay unit 7. FIG. A path is shown, and reference numeral 14 denotes a radio transmission path between the radio base station 3 and the radio relay unit 7.

The base station controller 1 causes each radio base station 2-5 to report their traffic, and the received field strengths R2-R5, traffic C12, C13, C14, and C15 of the base station, and frame errors in the radio transmission path. Receive rates Er11, Er12, Er13, and Er14. For example, the base station controller 1 instructs the radio base station 5 to communicate with the radio relay unit 7 based on the received data. The radio base station 5 transmits a control signal to the radio relay unit 7. The radio relay unit 7 relays a signal between the radio base station 5 and the mobile unit 6.

Referring to FIG. 2, the mobile unit 6 is located in the communication area 31 of the radio base station 3. The traffic C13 of the radio base station 3 is high, and accordingly, the reception field strength R3 of the radio base station 3 is also high. In contrast, in the radio base station 5 near the radio base station 3, the traffic C15 and the received field strength R5 are low.

Next, the path setting operation of the system having the above-described configuration will be described.

The base station controller 1 periodically requests each radio base station 2-5 to report traffic C13, C14, C15, and compares the maximum traffic C13 and the minimum traffic C15 with each other in the received report. When the difference C13-C15 of the traffic is larger than the threshold value? C1 preset in the base station controller 1, it is determined that a traffic offset has occurred between the wireless base stations in the group.

In this case, the base station controller 1 requests the radio base stations 3 and 5 corresponding to the maximum traffic C13 and the minimum traffic C15 to report the received field strengths R3 and R5. After receiving the request, the wireless base stations 3 and 5 measure the received field strengths R3 and R5 and report them to the base station controller 1.

It should be noted that the base station controller 1 may periodically request each radio base station 2-5 to immediately report the received field strengths R2 to R5 and traffic.

The base station controller 1 calculates the difference R3-R5 between the received field strength R3 at the wireless base station 3 with high traffic C13 and the received field strength R5 at the wireless base station 5 with low traffic C15, It is checked whether this difference is greater than or equal to the threshold value? R. Further, after confirming the difference in the received electric field strength between the two radio base stations 3 and 5, the base station controller 1 requests the radio relay unit to perform relay setting for the radio base station 5. In response to this request, the radio relay unit 7 sets the direction of the directional antenna 7a so that radio waves from the radio base station 5 are relayed.

According to the command from the base station controller 1, the wireless base station 5 transmits test data to the wireless relay unit 7 via the wireless transmission path 14. The radio relay unit 7 carries test data received to the radio base station 5 via the radio transmission path 14. The base station controller 1 receives the frame error rate Er14 of the test data in the radio transmission path 14 and the received field strength at the radio base station 5 at the time of transmission / reception of the test data (the error rate Er14 and the reception). The electric field strength is reported from the radio base station 5), and it is checked whether the path can be established through the radio relay unit 7.

After determining that the relay operation can be performed by establishing a path, the base station controller 1 is between the mobile station in the communication area 31 of the radio base station 5 with low traffic and the radio base station 3 with high traffic. The route is set using the radio relay unit 7. Due to this, it is possible to reduce the received electric field strength in the radio base station 3 with high traffic and to improve the call quality under the control of the base station controller 1.

3 shows the base station controller 1 and the wireless relay unit 7 of FIG. 2.

In the base station controller 1 of Fig. 3, the voice / data communication processing unit 1a performs voice / data communication processing for connecting the wireless zone to the wired zone. The voice control processing unit 1b performs voice control on the base station controller 1 itself, and also controls the radio base station 2-5 and the radio relay unit 7 connected to the base station controller 1. The route setting control section 1c includes a relay route setting control section 1d and a radio relay unit setting control section 1e, and sets a route passing through the radio relay unit 7.

The relay path setting control section 1d periodically references the traffic data of the radio base stations 2-5 and the request / maintenance data required for path setting, and checks whether or not the relay path should be set based on the data. do. The radio relay unit setting control section 1e holds data of the radio relay unit 7 controlled by the base station controller 1 and manages the direction setting and operation state of the radio relay unit 7.

The wireless relay unit 7 includes an antenna 7a having a strong directionality, an antenna 7b having no direction, a rotor 7c for directing the antenna 7a to the wireless base station 5 through which data is relayed, and an antenna 7a. Transmitting / receiving unit 7d for transmitting / receiving data to / from the radio base station 5 via a transmission / receiving unit 7e for transmitting / receiving data to / from the mobile unit 6 via an antenna 7b. Loop output setting for carrying data received from the wireless base station 5, antenna direction control for the wireless base station 5 to which data is relayed, and output control such as a mobile unit in response to a request from the base station controller 1; And a control unit 7f for performing the following.

The wireless base station 2-5 and the mobile unit 6 have a configuration known by those skilled in the art. Since these configurations are not directly related to the gist of the present invention, detailed description thereof will be omitted.

The relay path setting operation by the relay path setting control unit 1c and the relay unit setting control unit 1e of the base station controller 1 will be described in detail with reference to the flowchart of FIG. 4.

In the relay path setting control section 1c, the threshold value DELTA C1 = 200 related to the traffic difference and the threshold value DELTA R = 2 (mW) related to the received field strength difference are predetermined. In step S101, the relay path setting control section 1c periodically receives the traffic C12, C13, C14, and C15 reported from the radio base station 2-5. Each traffic for 5 minutes is assumed to be C12 = 200, C13 = 350, C14 = 150, and C15 = 50.

In step S102, the relay path setting control section 1c extracts C13 = 350 as the maximum traffic C1max. When the mobile unit 6 in the standby state is located in the area of the wireless base station corresponding to the extracted maximum traffic C1max, the relay routing setting control section 1c is the minimum traffic C1min from the wireless base station to which data can be relayed. Extract C15 = 50.

In step S103, the relay path setting control unit 1c checks whether the difference C1max-C1min between the maximum traffic and the minimum traffic exceeds the threshold value? C1 = 200 held in the relay path setting control unit 1c. In the case of YES in step S103, the relay path setting control section 1c continues the relay path setting. If NO in step S103, the relay path setting control section 1c determines that the traffic difference between the radio base station with the maximum traffic and the radio base station with the minimum traffic is not sufficient, so that the relay path setting is not necessary. Determine.

In this case, as the threshold value DELTA C1 increases, the possibility that the relay path setting acts decreases. However, in the case where the threshold value DELTA C1 is extremely small, the number of times that the relay path setting is required is increased in the traffic check step to greatly increase the amount of data to be processed in determining the necessity of the relay operation. Even if the relay operation is initiated, the traffic difference can be reduced quickly. In some cases, the relationship between wireless base stations can be reversed with respect to the difference.

In this embodiment, since C1max-C1min (= 300)> ΔC1 (= 200), a relay path must be set.

In step S104, the relay path setting control section 1c generates a request for each of the two wireless base stations 3 and 5 having the maximum and minimum traffic, and receives the received field strength Rmax = 20 (mW) and the received field strength Rmin = Receive a report of 15 (mW).

In step S105, the relay path setting control section 1c obtains the difference Rcmax-Rcmin between the received received electric field strengths, and checks whether the obtained difference is larger than the threshold value? R. This operation is performed to check whether or not the radio base station 5 performing the relay operation has sufficient communication capability as compared with the radio base station 3 requesting the relay operation.

In this embodiment, since Rcmax-Rcmin (= 5 (mW)> ΔR (= 2mW), the relay path setting is allowed.

In step S106, the radio relay unit setting control unit 1e requests the radio relay unit 7 to relay the control signal from the radio base station 5. Based on this request, the radio relay unit 7 sets the direction of the antenna and establishes synchronization to receive a signal from the radio base station 5.

In step S107, the relay path setting control section 1c generates a setting request to return the received signal to the radio base station side through the radio relay unit 7. After the transfer setting is completed, the relay path setting control section 1c transmits the test data to the radio base station 5 and receives the data carried from the radio base station 5.

In step S108, the radio base station 5 relays the radio transmission frame error rate Ert (= 0.01%) of the test data and the received field strength Rcmin '(= 16 mW) in the radio base station 5 upon reception of the test data. Report to control unit 1c.

In step S109, the relay path setting control section 1c determines the difference (Rcmax-Rcmim ') between the received field strength of the radio base station as the relay request transmission destination and the received field strength of the radio base station 5 as the relay request destination in the relay operation. Check if this threshold value ΔR is exceeded.

In this embodiment, the relay path setting is allowed because Rcmax-Rcmin '(= 20-16 = 4 mW)> ΔR (= 2 mW).

In step S110, control from the radio base station 5 is relayed by the radio relay unit 7 to allow handoff to the radio base station 5 as a relay request destination. The relay path setting control section 1c subtracts the difference Er13 by subtracting the frame error rate Ert at the reception of the test data from the frame error rate Er13 of the signal sent to the radio base station 5 via the radio relay unit 7. -Ert). If the difference obtained is higher than the radio transmission path frame error rates Er2 and Er3 of the communicating radio base stations 2 and 3, the relay path is determined to be invalid, and the relay path setting is stopped.

In this embodiment, assume that the radio transmission path frame error rate between the display section 6 and the radio base stations 2 and 3 is lower than that between the display section 6 and the radio relay unit 7.

In step S111, the relay path setting control section 1c checks whether there is any display section 6 capable of performing handoff via the wireless relay unit 7. In step S112, the relay path setting control unit 1c performs path setting control to establish a path between the radio base station 5 and the display unit 6 in the area of the radio base station 3 via the radio relay unit 7. do.

In step S103, when the traffic difference between the radio base station 3 as the relay request destination and the radio base station 5 as the relay request destination is small, the relay path setting control section 1c determines that relay path setting is not required. . That is, if the traffic of the radio base station assumed to have high traffic is not very high, or if the traffic of the radio base station for which relay operation is required is high, the flow proceeds to step S113. The relay path setting control section 1c next determines that the relay path does not need or can not be set for the radio base station 3 with high traffic.

In steps S105 and S109, when the received electric field strength difference between the radio base station 3 as the relay request destination and the radio base station 5 as the relay request destination is small, the relay path setting control section 1c next traffic is the least Perform the same operation as described above for the wireless base station having a. That is, if the received field strength of the radio base station 5 is increased by setting a relay path for the radio base station with low traffic, or if sufficient call quality is ensured in the radio base station with high traffic when sufficient power control is performed, the relay path It is determined that no effect can be expected from the establishment. In this case, the flow advances to step S114, where the relay path setting control section 1c changes the radio base station on which the relay operation is performed to the radio base station with the next minimum traffic. Next, steps S103 to S111 are repeated.

In steps S110 and S111, if the radio transmission path quality between the display unit 6 and the radio relay unit 7 is low, the display unit 6 is not near the radio relay unit 7, or several radio base stations are not present. If it is not present around the radio relay unit 7 and none of them exist as a handoff candidate for the display unit 6, it is determined that it is not important to set the path using the radio relay unit 7. Even in this case, the flow advances to step S114 to change the radio base station on which the relay operation is performed to the radio base station with the next minimum traffic. Next, steps S103 to S111 are repeated.

As described above, according to the present invention, a path is established for a wireless base station having lower traffic through the wireless relay unit in order to communicate with a mobile unit located in the communication area of the wireless base station with higher traffic. This can suppress the output power of the mobile unit located near the wireless relay unit. With this operation, since the received field strength of the radio base station with high traffic is reduced, call quality can be improved.

In addition, since the path is set to a radio base station with low traffic through the radio relay unit, the communication capacity of the mobile base station with low traffic can be effectively used.

Moreover, since the relay path is established through the radio relay unit to the radio base station from which the path cannot be established directly from the mobile unit, the mobile unit can route to a larger number of base stations.

Claims (16)

In the relay routing system, A plurality of wireless base stations 2-5 having communication areas 21, 31, 41, and 51; A mobile unit (6) for wirelessly communicating with the wireless base station by a code division multiple access scheme; A radio relay unit (7) which relays radio communication between the mobile unit and the radio base station by radio communication with the mobile unit and by radio communication with the radio base station; And Base station control means (1) for comparing traffic of said wireless base stations and establishing a path between said mobile unit disposed in a first wireless base station communication area having high traffic and a second wireless base station having low traffic Relay routing system comprising a. 2. The base station control means according to claim 1, wherein the base station control means comprises: traffic and received field strength of the radio base station, a radio transmission path error rate between the mobile unit and the radio base station, and a radio transmission path between the mobile unit and the radio relay unit. And route setting control means (1c) for determining whether to establish a path between the mobile unit and the second radio base station via the radio relay unit based on at least one of the error rates. 3. The method according to claim 2, wherein the path setting control means determines a path between the mobile unit and the second wireless base station through the wireless relay unit when the traffic difference between the first and second wireless base stations exceeds a predetermined value. Relay routing system to set up. 3. The method according to claim 2, wherein said routing control means is adapted to communicate between said mobile unit and said second wireless base station via said wireless relay unit when the difference in received field strength between said first and second wireless base stations exceeds a predetermined value. Relay routing system to set the path. 5. The method of claim 4, wherein the routing control means selects a third radio base station having low traffic instead of the second radio base station, and the received field strength difference between the first and second radio base stations is less than or equal to the predetermined value. A relay routing control system that performs relay routing control that includes comparisons between traffic again. 3. The radio base station according to claim 2, wherein the path setting control means makes a difference between a frame error rate of a signal sent to the second radio base station via the radio relay unit and a frame error rate at the reception of test data. And establish a path between the mobile unit and the second wireless base station via the wireless relay unit when the wireless transmission path error rate is less than. 7. The frame error of claim 6, wherein the routing control means selects a third wireless base station with next least traffic instead of the second wireless base station and is sent to the second wireless base station via the wireless relay unit. And repeating the traffic routing control when the difference between the rate and the frame error rate upon reception of the test data is equal to or greater than the radio transmission path error rate of the radio base station during communication. The relay path setting control system according to claim 1, wherein said path setting control means periodically determines whether to set a path between said mobile unit and said second wireless base station via said wireless relay unit. The method of claim 1, The wireless relay unit At least one first antenna (7a) directed to the second wireless base station for transmitting / receiving a radio signal to / from the second wireless base station with strong directivity; And A second antenna 7b for transmitting / receiving radio signals to / from said mobile unit without directivity, A relay routing control system for relaying signals between the second wireless base station and the mobile unit using the first and second antennas. The relay routing control system according to claim 9, wherein the first antenna is disposed corresponding to the wireless base station, and a direction in which the antenna is directed is fixed to the wireless base station. The method of claim 9, The first antenna has a variable directing direction, And the base station control means includes antenna control means (1e) for controlling the directing direction of the first antenna. 12. The relay routing control system according to claim 11, wherein said base station control means comprises relay unit control means (1e) for performing control to direct said first antenna to said second wireless base station. In the relay route setting method, Installing a wireless relay unit (7) between the mobile unit (7) and the plurality of wireless base stations (2-5) for performing wireless communication using a code division multiple access scheme; At least a traffic and reception field strength of the wireless base station between the wireless base stations, a wireless transmission path error rate between the mobile unit and the wireless base stations, and a wireless transmission path error rate between the mobile unit and the wireless relay unit. Comparing one set; And Establishing a path between the mobile unit disposed in the communication area of the first radio base station with high traffic through the radio relay unit and the second radio base station with low traffic based on the comparison result. Relay route setting method comprising a. 15. The method of claim 13, wherein the step of establishing a path establishes a path between the mobile unit and the second wireless base station through the wireless relay unit when the traffic difference between the first and second wireless base stations exceeds a predetermined value. Relay route setting method comprising the step of. The method of claim 13, wherein the setting of the path comprises: a path between the mobile unit and the second wireless base station through the wireless relay unit when a difference in the received field strength between the first and second wireless base stations exceeds a predetermined value. Relay route setting method comprising the step of setting a. 14. The method of claim 13, wherein the step of establishing the path comprises: a difference between a frame error rate of a signal sent to the second wireless base station via the wireless relay unit and a frame error rate upon reception of test data of the wireless base station in communication. Establishing a path between the mobile unit and the second wireless base station via the wireless relay unit when less than a wireless transmission path error rate.