JP3325244B2 - Band allocation method and mobile communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band allocation method and a mobile communication network, and more particularly to a handover (switching of a communication destination base station accompanying the movement of a terminal) when an ATM system is applied to a cellular mobile communication network. The present invention relates to a band allocation method and a mobile communication network for efficiently allocating a band to a call and a new call.

[0002]

2. Description of the Related Art In recent years, research and development on high-speed and multimedia transmission in mobile communication have been actively conducted.
In such a system, in order to keep the transmission power low, the radio communication range covered by a single radio base station in a conventional automobile or mobile phone is several kilometers (macro cell), whereas the radio communication range of about 100 m is It is said that it will be within the communication range (micro cell). When the wireless communication range is small as described above, a mobile station moving at a high speed immediately goes out of the communication range, so that a function for performing handover between wireless base stations is required. Note that handover refers to switching of a radio base station in order to continue a call even if the mobile station moves between radio zones during a call.

Conventionally, there is a PHS as a narrow system with a radio communication range of about 100 m. However, a mobile station moving at a speed of a pedestrian is assumed as a target of a call, and a handover of a mobile station moving at a high speed is required. Can not. Then, in the conventional car telephone system, there is an instantaneous interruption of 0.7 to 0.8 seconds when switching channels during a call. This occurs because the data flowing through the transmission line during the handover is simply discarded.

[0004] When such an instantaneous interruption occurs, in the case of voice or moving image transmission, sound skips and appears as phenomena such as image quality deterioration.
In the case of computer data transmission, there is a problem that data loss occurs, data is retransmitted, and traffic congestion is caused. In the case of a microcell, a handover occurs in a shorter cycle than in a macrocell, so this problem becomes more remarkable. In order to solve the problem of such an instantaneous interruption, not only a wireless-level channel switching technology but also a technology that does not cause data loss in the communication system as a whole is required.

[0005] In a mobile communication system, there is a radio portion between a mobile station and a radio base station, and a wired portion connecting the radio base station, the serving control station, and the gateway control station. As this wired part, a dedicated network for automobiles and mobile phone systems, N for PHS
-The ISDN network is used, but the service quality is based on voice, and there is a problem that the ability to integrate and transmit moving images and computer data is insufficient. Therefore, a network using an ATM (Asynchronous Transfer Mode) system is promising as a wired network for performing high-speed multimedia transmission.

In ATM, data is carried in a fixed-length format called a cell, which has a header part of 5 bytes and a payload part of 48 bytes, a total of 53 bytes. In the header part, information for routing called virtual path and virtual channel is described, but this is not the same setting from the source node (switch) to the final destination node, and it is usually It is valid only between ATM nodes, and is appropriately changed when inputting to each ATM node. At that time, an output transmission path is determined.

[0007] In order to adopt the ATM system in a wired portion of a mobile communication network where frequent handovers occur, a technique for switching paths during communication and preventing data loss is required. Therefore, a method of storing cells before starting the handover processing, changing the output transmission path after the handover processing is completed, and then transmitting the stored cells can be considered. Regarding this technology, Japanese Patent Application Laid-Open No. 10-224375 discloses a technology proposed by the inventor of the present application.

[0008]

In the conventional ATM exchange described above, cells arriving at the exchange during the handover process are accumulated in a buffer of a flow control module provided at the entrance of the exchange. Then, in the next handover, there is a possibility that this exchange deviates from the communication path, so it is necessary to eliminate the accumulation of cells in the buffer after the handover process and before the next handover occurs. However, since a new cell arrives by normal transmission even during storage cancellation, it is necessary to transmit at a burst transmission speed (normal transmission speed + marginal transmission speed) during the storage cancellation time.

Normal transmission speed is v, burst transmission speed is v +
If v / n, accumulation time is t, and accumulation elimination time is T, the sum of cells arriving at the normal transmission rate during the accumulation time and cells arriving at the normal transmission rate during the accumulation elimination time is eliminated at the burst transmission rate. (V + v / n) T = vt + vT If this is rewritten, T = nt.

That is, the storage elimination time is the product of the ratio of the normal transmission speed to the marginal transmission speed and the storage time. In such a wireless communication system, a band allocation method (hereinafter, used in the same meaning as the amount of transmission per unit time = transmission speed) in consideration of a marginal transmission speed is required. However, if the burst transmission band is always allocated to the handover call, there is a problem that the number of accommodated calls decreases.

An object of the present invention is to solve the above-mentioned problems of the prior art and to implement a bandwidth allocation method and a bandwidth allocation method capable of accommodating more calls in a path switching method for preventing data loss during handover. To provide a mobile communication network.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a request for allocating a new call band and a request for allocating a handover call band accompanying a mobile terminal in communication entering the radio zone are stored in separate queues. This is a bandwidth allocation method for queuing in the FIFO format and accepting the request. In the bandwidth allocation request for the handover call bandwidth, a request is made in two stages of a minimum required bandwidth and a remaining bandwidth, and each queue is individually allocated. It is characterized by queuing in the FIFO format and periodically receiving the request. In addition, a request is received from a queue queuing a request for allocating a new call band, a handover call band (required minimum), and a handover call band (remaining) at a ratio of a preset weight to an available band. There is also a feature in performing.

Further, a new call band, a handover call band
(Minimum required), it is also characterized in that requests are received at the ratio of the number of requests queued at that time from the queue in which the allocation request for the handover call band (remaining) is queued. Furthermore, from the queue queuing requests for allocating a new call band, a handover call band (required minimum), and a handover call band (remaining), the product of the number of requests queued at that time and a preset weight is obtained. It is also characteristic that requests are accepted at the ratio of. In the present invention, it is not necessary to simultaneously secure the handover call band (required minimum) and the handover call band (remaining), and it is possible to accommodate more calls by saving band resources.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 7 is a block diagram showing a configuration of an exchange to which the present invention is applied. The mobile communication network has, for example, a hierarchical structure, and an ATM node (switch), which is a gateway control station (not shown), is located at the top of the hierarchy and is connected to the serving control station switch 10 located at a lower level. In addition, it is also connected to other communication networks.

The serving control center switch 10 is an ATM node located below the gateway control station, and may have a plurality of hierarchies. The lowest control station exchange 10 is an input / output ATM.
The transmission lines 13 and 14 are connected to the radio base stations 15 and 16. Each of the wireless base stations 15 and 16 performs wireless connection with the mobile station 20 located in a predetermined service area. The serving control center exchange 10 includes a cell switch 80 and a cell switch control device.
81, Input control module 8 for each input ATM transmission line
2, 90, an output buffer 84 and output destination tables 83 and 91. The output buffer 84 is used in the input ATM transmission line.
This is a buffer memory of a cell arranged in a stage preceding the cell switch 80. Output destination tables 83 and 91 are input ATM
It is provided at a stage prior to the cell switch 80 in the transmission path, and from the ATM virtual channel identifier at the time of input of the cell, the virtual channel identifier at the time of the cell passing through the cell switch (
This is a table from which virtual channel identifiers and output ATM transmission line information can be searched.

The input control modules 82 and 90 respectively monitor the input ATM transmission lines, search the output destination tables 83 and 91 using the ATM virtual channel identifier of the input cell, and output the output ATM.
If the transmission path information is "pending", the cell is stored in the output buffer 84. If not “reserved”, it is rewritten to the virtual channel identifier when passing through the cell switch and passed to the cell switch 80. The information cell for connection control such as call setting is transferred to the cell switch control device 81 via the cell switch 80. Further, when the “hold” is released, the cells stored in the buffer 84 are transmitted to the cell switch 80 at the set transmission rate.

The buffer terminal device 85 includes an input buffer 8
6, 87, 88 and a cell sending module 89 are provided. The input buffers 86, 87, and 88 are buffer memories for cells that perform FIFO operations, and are secured and released as needed for each virtual channel. The cell transmission module 89 transmits cells at a transmission rate set for each virtual channel by a band management device (12) described later.

At the time of the handover process, before starting the handover process, the input transmission path is switched to the buffer terminal device 85 to store cells in the input buffers 86 to 88 and to switch the radio base stations 15 and 16. . And
After the handover process is completed, the buffer terminal device 85
The cell stored by connecting the output of the first base station and the new base station 16 is burst-transmitted to the mobile station, and when the transmission is completed, the cell is switched back to the original transmission path.

FIG. 1 is a block diagram showing a main configuration of a mobile communication system to which the present invention is applied. The old base station 15 is connected to the exchange 10 via a transmission path 13 to the old base station, and the new base station 16 is connected to the exchange via a transmission path 14 to the new base station.
Connected to 10. The exchange 10 is provided with band management devices 11 and 12 for each of the transmission lines 13 and 14 (corresponding to each base station). The mobile terminal 20 communicating with the old base station 15 is assigned a band requested at the time of calling, for example, and when handing over to the new base station 16, the handover call band via the old base station 15 (required minimum) An assignment request 32 is transmitted to the exchange 10. The required amount of the handover call band (required minimum) allocation request 32 may be, for example, the same as the band requested at the time of calling.

The mobile terminal 21 that has handed over to the new base station 16
Transmits a handover call band (remaining) allocation request 33 to the exchange 10 via the new base station 16. Handover call bandwidth
(Remaining) The required amount of the allocation request 33 is added to the above-mentioned required amount of the handover call band (required minimum) allocation request 32, and the band for burst-transferring the cells held during the handover to the mobile terminal 21. Assuming that the assigned amount at the time of calling is 1, the amount may be, for example, about 0.1 to 2.

When a mobile terminal 22 that is located in the wireless zone 18 of the new base station 16 and is not currently in communication makes a call, the new base station
A new call bandwidth allocation request 31 is transmitted to the exchange 10 via 16. Each band allocation request 31, 32, 33 is passed to the band management device 12 (a new base station side), which is a function executed in the cell switch control device 81 of the exchange 10.

FIG. 2 is a block diagram showing the configuration of the band management device 12 (on the new base station side). The bandwidth management device 12 includes a new call bandwidth allocation request queue 51, a handover call bandwidth (minimum required) allocation request queue 52, and a handover call bandwidth.
(Remaining) Allocation request queue 53, free bandwidth management table 50
Is provided. The passed new call bandwidth allocation request 31 is transferred to the new call bandwidth allocation request queue 51, the handover call bandwidth (required minimum) allocation request 32 is transferred to the handover call bandwidth (required minimum) allocation request queue 52, and the handover call bandwidth (remaining The assignment requests are queued in the handover call band (remaining) assignment request queue 53, respectively.

The bandwidth management device 12 has a free bandwidth management table.
When a free band is detected from 50, a request is taken out from the new call band allocation request queue 51 and a free band is allocated. When the band management device 12 detects a free band from the free band management table 50, it extracts a request from the handover call band (required minimum) allocation request queue 52 and allocates a free band. Further, when the band management device 12 detects a free band from the free band management table 50, the handover call band
(Remaining) The request is taken out from the allocation request queue 53 and a free band is allocated. With the above-described configuration and operation, a necessary band is allocated when necessary, so that useless band allocation is reduced, and an allowable traffic amount is increased.

FIG. 3 is a block diagram showing the configuration of the bandwidth management device 12 provided with a reception weight storage means for each queue. The bandwidth management device 12 has an available bandwidth management table 50, a new call bandwidth allocation request queue 51, and a handover call bandwidth.
A (required minimum) allocation request queue 52, a handover call band (remaining) allocation request queue 53, and reception weight storage means 61, 62, 63 for each request are provided. A value is set in advance in the reception weight storage means 61, 62, 63 of each request.

The passed new call bandwidth allocation request 31 is stored in the new call bandwidth allocation request queue 51 in the handover call bandwidth.
The (required minimum) allocation request 32 is queued in a handover call band (required minimum) allocation request queue 52, and the handover call band (remaining) allocation request is queued in a handover call band (remaining) allocation request queue 53. When detecting the free bandwidth from the free bandwidth management table 50, the bandwidth management device 12 allocates the free bandwidth according to the ratio of the weight of receiving each request.

More specifically, it is assumed that the bandwidth management device 12 detects a free bandwidth at a predetermined cycle (for example, every one second) and that 16 free bandwidths exist at a certain time. Assuming that the ratio of the acceptance weights W1 to W3 of each request is 2: 5: 1, 4 units for a new call, 10 units for a handover call (required minimum), and 10 units for a handover call (remaining). Two units are allocated. Then, within the range of each allocated free band, requests are sequentially taken out from each of the request queues 51 to 53 and bands are allocated. With the above configuration and operation, a necessary band is allocated according to the type of request, so that a band can be preferentially secured, for example, during handover, and communication quality is improved.

FIG. 4 shows queue length monitoring means for each queue.
FIG. 3 is a block diagram illustrating a configuration of a band management device 12 provided with 71, 72, and 73. The bandwidth management device 12 includes an available bandwidth management table 50, a new call bandwidth allocation request queue 51, a handover call bandwidth (minimum required) allocation request queue 52, a handover call bandwidth (remaining) allocation request queue 53, and a length of each request queue. Monitoring means 71, 72 and 73 are provided.

The passed new call band allocation request 31 is stored in the new call band allocation request queue 51 in the handover call band.
The (required minimum) allocation request 32 is queued in a handover call band (required minimum) allocation request queue 52, and the handover call band (remaining) allocation request is queued in a handover call band (remaining) allocation request queue 53. The bandwidth management device 12 detects a free bandwidth from the free bandwidth management table 50 at a predetermined cycle, for example, and allocates a free bandwidth according to each request queue length. For example, the number of assignments is calculated as follows.

P1 = E * L1 / L1 + L2 + L3 P2 = E * L2 / (L1 + L2 + L3) P3 = E * L3 / (L1 + L2 + L3)

Here, E is the total amount of free bandwidth, and L1 to
L3 is the queue length of each of the request queues 51 to 53. Then, within the allocated free bandwidths P1 to P3, requests are sequentially taken out from the request queues 51 to 53 and bandwidths are allocated. With the above configuration and operation, the necessary bandwidth is allocated according to the traffic condition.
The vacant space can be used efficiently, and the allowable traffic volume increases.

FIG. 5 is a block diagram showing the configuration of the bandwidth management device 12 provided with reception weight storage means 61, 62, 63 and queue length monitoring means 71, 72, 73 for each queue. The bandwidth management device 12 has an available bandwidth management table 50, a new call bandwidth allocation request queue 51, and a handover call bandwidth (required minimum).
Allocation request queue 52, handover call band (remaining) allocation request queue 53, and reception weight storage area for each request
61, 62, 63 and request queue length monitoring means 71, 72, 73 are provided.

The passed new call band allocation request 31 is stored in the new call band allocation request queue 51 in the handover call band.
The (required minimum) allocation request 32 is queued in a handover call band (required minimum) allocation request queue 52, and the handover call band (remaining) allocation request is queued in a handover call band (remaining) allocation request queue 53. The bandwidth management device 12 detects a free bandwidth from the free bandwidth management table 50 at a predetermined cycle, and allocates a free bandwidth according to the reception weight of each request and the queue length. For example, the number of assignments is calculated as follows.

K1 = w1 * L1 K2 = w2 * L2 K3 = w3 * L3 P1 = E * K1 / (K1 + K2 + K3) P2 = E * K2 / (K1 + K2 + K3) P3 = E * K3 / (K1 + K2 + K3).

Here, E is the total amount of available bandwidth, and L1 to
L3 is a queue length of each of the request queues 51 to 53, and w1 to w3 are reception weights of each request. Then, within the allocated free bandwidths P1 to P3, requests are sequentially taken out from the request queues 51 to 53 and bandwidths are allocated. With the above configuration and operation, the necessary bandwidth is allocated according to the type of request and the state of the traffic, so that, for example, the bandwidth can be preferentially secured at the time of handover, the communication quality is improved, and the available space is efficiently used. Becomes possible,
Allowable traffic volume increases.

FIG. 6 is an explanatory diagram showing the operation at the time of handover. The lower graph in FIG. 6 shows a change in the communication band of the mobile terminal 20 and a change in the amount of cells stored in the exchange at the time of handover. The wireless zones 17, 18, and 19 of the old base station, the new base station, and the next base station are arranged one-dimensionally and overlap with some overlap width. When the mobile terminal 20 located in the wireless zone 17 of the old base station passes through the boundary of the wireless zone 18 of the new base station, a handover occurs, and a handover call band (minimum necessary) allocation request is transmitted. Since information about the band used by the new base station is obtained via the old base station, the handover call band (minimum necessary) allocation request needs to be accepted before passing through the wireless zone 17 of the old base station.

Data arriving at the exchange during the handover is stored in buffers (76 to 78) of the exchange. After the handover, it is necessary to transmit at a transmission speed higher than usual in order to eliminate this accumulation. Therefore, a handover call band (remaining) allocation request is further made after the handover is completed. That is, it is not necessary to secure this band until the handover ends. Also, since the current exchange may deviate from the route, it is necessary to accept the handover call band (remaining) allocation request by a predetermined time before the next handover starts.

While the embodiment has been disclosed above, the present invention may be modified as follows. In the embodiment, the handover call band (required minimum) allocation request amount has been disclosed, for example, the same example as the allocation amount at normal time.However, the handover call band (required minimum) allocation request amount in the present invention is the handover call band. (Remaining) a band capable of transmitting the allocation request may be used, and handover is possible even if the handover call band (required minimum) allocation request amount is smaller than the normal band. In this case, the band is returned to the normal band after the burst transmission. Also, the handover call band (remaining) allocation request does not need to be allocated immediately after the handover, and if the exchange can hold the cell, the data disappears even if the handover call band (remaining) is allocated after a lapse of a predetermined time after the handover. There is no. Therefore, according to the present invention, it is possible to more flexibly secure the band at the time of handover.

[0038]

As described above, according to the present invention, the handover call band (required minimum) and the handover call band
(Remaining) does not have to be secured at the same time, and there is an effect that more calls can be accommodated by saving bandwidth resources. Further, even if the band (remaining) for burst transmission cannot be secured at the time of starting handover, handover is possible, and the possibility that a call is disconnected due to handover is reduced, and there is also an effect that communication quality is improved.
Further, by allocating the bandwidth based on the type of request and the traffic state, there is an effect that the communication quality is improved or more calls can be accommodated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a mobile communication network to which the present invention is applied.

FIG. 2 is a block diagram illustrating a configuration of a band management device according to an embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a bandwidth management device according to an embodiment of the present invention when referring to the weight of each request assignment;

FIG. 4 is a block diagram illustrating a configuration of a bandwidth management device when referring to each request queue length according to an embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a bandwidth management device according to an embodiment of the present invention, in which the weight of each request allocation and each request queue length are referred to simultaneously.

FIG. 6 is an explanatory diagram showing an operation at the time of handover according to the present invention.

FIG. 7 is a block diagram illustrating a configuration example of an exchange to which the present invention is applied.

[Explanation of symbols] [Explanation of symbols]

10: exchange, 11: (old base station side) band management device, 12
... (new base station side) band management device, 13 ... (old base station side) transmission line, 14 ... (new base station side) transmission line, 15 ... old base station, 16
... new base station, 17 ... wireless zone of old base station, 18 ... wireless zone of new base station, 19 ... wireless zone of next base station, 20
... mobile terminals 1, 21 ... mobile terminals 2, 22 ... mobile terminals 3,
31: New call band allocation request, 32: Handover call band (minimum required) allocation request, 33: Handover call band (remaining) allocation request, 41: New call band allocation
42 ... handover call band (required minimum) allocation, 43
... handover call band (remaining) allocation, 50 ... free band management table, 51 ... new call band allocation request queue,
52: Handover call band (required minimum) allocation request queue, 53: Handover call band (remaining) allocation request queue, 61: New call band allocation weight storage means, 62 ...
Handover call band (required minimum) allocation weight storage means, 63: Handover call band (remaining) allocation weight storage means, 71: New call band allocation queue length monitoring means,
72: Handover call bandwidth (minimum required) assigned queue length monitoring means; 73: Handover call bandwidth (remaining) assigned queue length monitoring means

────────────────────────────────────────────────── ─── Continuing from the front page Application for Patent Law Article 30 (1) has been applied. Masaya Nishio et al., Evaluation of bandwidth allocation method in ATM mobile communication network to which non-stop handover method is applied (RCS99-23), IEICE Technical Report, IEICE, Japan, IEICE, May 24, 1999, IEICE Technical Report Vol. 99, No. 85, p. 57-61 "and" Masaya Nishio two others, Evaluation of a Bandwi dth Assignment Method in Mobile ATM Networks that Achieve Lossless Handove r, Session WP4: Wireless A TM, 1999 IEEE Wireless Commu nications and Networking Conference, 1999 September 21 (56) References Masaya Nishio et al., Evaluation of bandwidth allocation method in ATM mobile communication network to which non-stop handover method is applied (RCS99-23). IEICE Technical Report, The Institute of Electronics, Information and Communication Engineers, Japan, May 24, 1999, IEICE Technical Report Vol. 99, No. 85, p. 57-61 (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B ^7/ 24-7/26 102 H04Q ^7/ 00-7/38

Claims (6)

(57) [Claims] 1. A method for allocating a band in a cellular wireless communication system, comprising: receiving a request for allocating a new call band in response to a call from a mobile terminal; Receiving a request for allocating a second band, receiving a request for allocating a second band of a handover call accompanying the end of handover of the mobile terminal, and periodically allocating a free band to the received request. A bandwidth allocation method comprising: 2. The method according to claim 1, wherein in the allocation of the new call bandwidth and the first and second bandwidth allocation of the handover call, a ratio of a weight set in advance from a queue queuing the allocation request to an empty bandwidth is used. The bandwidth allocation method according to claim 1, wherein allocation is performed. 3. The method according to claim 1, wherein in the allocation of the new call band and the first and second band allocation of the handover call, the request queued from the queue queuing the allocation request to the vacant band at that time. The bandwidth allocation method according to claim 1, wherein allocation is performed at a ratio of the amounts. 4. The method according to claim 1, wherein in the allocation of the new call band and the first and second band allocations of the handover call, a ratio of a weight set in advance from a queue queuing an allocation request to a free band is calculated. 2. The bandwidth allocation method according to claim 1, wherein the allocation is performed at a ratio of the queued request amount at that time. 5. In a cellular ATM mobile communication network having an exchange provided with band management means corresponding to each base station, said band management means transmits a call to a mobile terminal located in a service area of said base station. First queuing means for queuing a request for allocating a new call band associated with a call, and queuing a first band allocating request for a handover call before starting handover from a mobile terminal moving from another area. Second queue means, third queue means for queuing a second bandwidth allocation request of a handover call from the mobile terminal after completion of the handover to the area, the first queue means, the second queue means And based on the bandwidth allocation request stored in the third queue means,
A mobile communication network comprising: band allocation means for performing band allocation. 6. The bandwidth allocating means is configured to provide at least one of a ratio of a weight set in advance and a ratio of a request amount queued at that time to a vacant band of a line passing through a base station. The mobile communication network according to claim 5, wherein the assignment is performed based on: