JP5278110B2 - Wireless signal transmission system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dynamically change the allocation of uplink bandwidths by collectively managing a plurality of wireless transmission/reception units. <P>SOLUTION: A wireless control section 10 is connected to (n) pieces of wireless transmission/reception units 40-1 to 40-n via an optical fiber link 30. When there is an uplink signal to be transmitted to the wireless control section 10, each of the wireless transmission/reception units 40-1 to 40-n transmits a transmission request signal to the wireless control section 10. In response to the transmission request signal, the wireless control section 10 calculates uplink allocation bandwidths of the wireless transmission/reception units 40-1 to 40-n, within an uplink bandwidth of the optical fiber link 30 and then permits transmission request source of the transmission requested signal. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

The present invention relates to a radio signal transmission system and method for transmitting a radio signal used for mobile communication, and more particularly, to a radio signal transmission system and method capable of changing band allocation to a plurality of radio stations.

  Conventionally, as a method for efficiently deploying a radio base station, a configuration in which a radio control unit of a radio base station and a radio unit that radiates radio waves are connected via an optical fiber link is known. A configuration is known in which a plurality of radio units are connected to a radio control unit, and the plurality of radio units are centrally managed by one radio control unit (Patent Documents 1 and 2).

Special table 2007-507957 JP 2008-288754 A

  In the conventional example, the band between the radio control unit and the radio unit is fixed. In mobile communication, the amount of communication between a mobile terminal and a radio unit varies greatly with time. It is useless from the viewpoint of effective use of the band to keep radiating radio waves in a fixed band even in a time zone with a small amount of communication, for example, at night.

  Further, the configuration described in Patent Document 2 can reduce the installation space of the wireless base station and the infrastructure maintenance cost of the mobile communication carrier, but the operation cost of the wired network multiplexing apparatus becomes a burden.

An object of the present invention is to provide a radio signal transmission system and method capable of flexibly changing a band between a radio control unit and each of a plurality of radio units with simple management.

A radio signal transmission system according to the present invention is a radio signal transmission system that transmits radio signals between a mobile terminal and a higher-level network, each of which includes a plurality of radio transmission / reception units that can be wirelessly connected to the mobile terminal, A wireless control unit that transmits / receives the wireless signal to / from a higher level network; and an optical fiber link that connects the plurality of wireless transmission / reception units and the wireless control unit. A request means for transmitting a transmission request signal to the radio control unit when the radio signal to be transmitted to the unit is received, the radio control unit being within an upstream band of the optical fiber link with respect to the transmission request signal Determining means for determining whether allocation is possible, and when the bandwidth required by the transmission request signal cannot be allocated, the uplink allocated bandwidth and the actual An adjustment unit that enables uplink band allocation to the transmission request signal by reducing the uplink allocated band to another radio transmission / reception unit having the largest difference from the amount of hicks, and allocation within the uplink band of the optical fiber link And a means for transmitting a transmission permission signal to the request source of the transmission request signal in a possible state .
A radio signal transmission method according to the present invention includes a plurality of radio transmission / reception units that can be wirelessly connected to a mobile terminal, a radio control unit that transmits / receives the radio signal to / from an upper network, the plurality of radio transmission / reception units, In a radio signal transmission system having an optical fiber link connecting a radio control unit, a method for transmitting the radio signal between the mobile terminal and the host network, the radio transmission / reception unit includes: Upon receiving a radio signal to be transmitted to the radio control unit, a request step for transmitting a transmission request signal to the radio control unit, and the radio control unit in response to the transmission request signal, an upstream band of the optical fiber link A determination step for determining whether or not allocation is possible, and the radio control unit can allocate a bandwidth required by the transmission request signal. An adjustment step that enables uplink bandwidth allocation for the transmission request signal by reducing the uplink allocated bandwidth to other radio transmission / reception units having the largest difference between the uplink allocated bandwidth and the actual traffic amount when there is not, The radio control unit includes a step of transmitting a transmission permission signal to the request source of the transmission request signal in a state where the radio control unit can be allocated within the uplink band of the optical fiber link.

  According to the present invention, not only centralized management of a plurality of radio units can be realized, but also reduction of installation space and operation cost of a base station can be realized. Dynamic bandwidth allocation to the wireless transmission / reception unit becomes possible, and effective bandwidth utilization can be realized.

It is a schematic block diagram of one Example of this invention. It is an example of selection of a CPRI bit rate. It is a flowchart of the process with respect to the transmission request of a present Example. It is an example of traffic information.

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

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention. Mobile communication radio base stations are installed in various locations. The radio base station includes a radio control unit 10 and n radio transmission / reception units 40-1 to 40-n connected to the radio control unit 10 via an optical fiber link 30. The optical fiber link 30 includes an optical fiber 32 connected to the wireless control unit 10, branched optical fibers 34-1 to 34-n connected to the wireless transmission / reception units 40-1 to 40 -n, and branched light from the optical fiber 32. The optical splitter 36 includes an optical splitter 36 that demultiplexes the downstream optical signals to the fibers 34-1 to 34-n, combines the upstream optical signals from the branch optical fibers 34-1 to 34-n, and supplies the multiplexed optical signals to the optical fiber 32. Each of the radio transmission / reception units 40-1 to 40-n is connected to antennas 60-1 to 60-n that transmit and receive radio waves carrying radio signals.

  In this embodiment, a common public radio interface (CPRI) is used as a connection interface between the wireless control unit 10 and the wireless transmission / reception units 40-1 to 40-n. Of course, the present invention is not limited to CPRI. FIG. 2 shows CPRI bit rate options. If the downstream band on the optical fiber 32 is 10 Gbps, a CPRI bit rate of up to 2457.6 Mbps can be assigned to each wireless transmission / reception unit when four wireless transmission / reception units are expropriated.

  A basic transmission operation of a radio signal between the radio control unit 10 and the radio transmission / reception units 40-1 to 40-n will be briefly described. The wireless signal of this embodiment is voice data, text data, image data, mail data, etc. used for communication with the mobile terminal, and identification information for identifying the communication partner is added to the header. Has been.

A radio signal directed from the higher level network to the mobile terminal is broadcast from the radio control unit 10 to all the radio transmission / reception units 40-1 to 40-n. The framing unit 12A of the radio control unit 10 converts a radio signal from the higher level network toward the mobile terminal into a data format for optical transmission, for example, a frame format. In this embodiment, a CPRI frame is used. Each frame generated by the framing unit 12A is sequentially stored in the downlink buffer 14A. The CPRI frame has a synchronization code at the head.

  The optical transmitter 16A reads the data stored in the downlink buffer 14A, converts it into serial data, converts it into an optical signal (downlink optical signal), and supplies it to the optical multiplexer / demultiplexer 18. The optical fiber link 30 uses optical carriers having different wavelengths for upstream optical signals and downstream optical signals. The optical multiplexer / demultiplexer 18 is composed of a wavelength division multiplexing (WDM) optical coupler, and outputs the downstream optical signal from the optical transmitter 16A to the optical fiber 32 of the optical fiber link 30.

  The transmission / band control device 20 manages and controls the uplink signal transmission timing and band allocation by the radio transmission / reception units 40-1 to 40-n connected to the optical fiber link 30. The transmission / band control device 20 can write a control signal for controlling each of the radio transmission / reception units 40-1 to 40-n in the downlink buffer 14A. The control signal written in the down buffer 14A is read out to the optical transmitter 16A between or before the frames of the radio signal described above, converted into a down optical signal, and transmitted from the optical multiplexer / demultiplexer 18 to the optical fiber. 32. This control signal includes, for example, allocation band information allocated to uplink transmission for each of the radio transmission / reception units 40-1 to 40-n and time slot information for permitting transmission. By making the time slots used by the wireless transmission / reception units 40-1 to 40-n different in uplink transmission, the optical fiber link 30 can be shared by the plurality of wireless transmission / reception units 40-1 to 40-n.

  The downstream optical signal output from the wireless control unit 10 to the optical fiber 32 of the optical fiber link 30 is divided into n by the optical splitter 36, propagates through the branched optical fibers 34-1 to 34-n, and is transmitted to the optical transmission / reception unit 40-. Enter 1-40-n. As will be described later, each of the optical transmission / reception units 40-1 to 40-n converts the downstream optical signals from the corresponding branch optical fibers 34-1 to 34-n into electric signals, and converts the radio signals to the antennas 60-1 to 60-1. Radio waves are emitted from 60-n. The operation of the optical transmission / reception unit 40-1 will be described as an example.

The optical multiplexer / demultiplexer 42 includes a WDM optical coupler similar to that of the optical multiplexer / demultiplexer 18, and supplies the downstream optical signal from the branch optical fiber 34-1 to the optical receiver 44A. The optical receiver 44A converts the downstream optical signal from the optical multiplexer / demultiplexer 42 into an electrical signal, performs binary discrimination, parallelizes it, and stores it in the downstream buffer 46A.

  The deframing unit 48A is a device that performs processing reverse to that of the frame unit 12A, sequentially reads out the CPRI frames stored in the downlink buffer 46A, extracts a radio signal from each CPRI frame, and releases radio waves as necessary. Convert to a data structure for The RF signal processing device 50 converts the radio signal output from the deframe unit 48A into a specified modulation scheme such as CDMA or OFDM with a code specifying a transmission destination mobile terminal added thereto, and an antenna 60 Drive -1. Thereby, a radio signal is emitted as a radio signal of a predetermined band.

  The antenna 60-1 also detects a radio signal from a nearby mobile terminal, converts it to a digital radio signal that is an electrical signal, and supplies the digital radio signal to the framing unit 48B. The frame unit 48 </ b> B collects the received radio signal from the RF signal processing device 50 in the CPRI frame for transmission through the optical fiber link 30. A synchronization signal and a monitoring control signal are added to the CPRI frame. The CPRI frames generated by the framing unit 48B are sequentially stored in the upstream buffer 46B. Since the CPRI frame has a different frame size depending on the transmission band, it is necessary to adjust the frame size to match the allocated band. The frame control unit 52 adjusts the frame size of the CPRI frame by controlling the framing unit 48B in accordance with the allocated bandwidth information stored in the downlink buffer 46A.

  The transmission control device 54 reads the data stored in the upstream buffer 46B to the optical transmitter 44B at a timing when transmission is permitted by the wireless control unit 10. The optical transmitter 44B serializes and converts the data from the upstream buffer 46B into an optical signal (upstream optical signal), and outputs the upstream optical signal to the optical multiplexer / demultiplexer 42.

In this embodiment, the transmission control device 54, each time the uplink radio signals to be transmit are stored in the uplink buffer 46B, to generate a upstream optical signal requesting transmission permission to the optical transmitter 44B, radio contrast Based on the time slot information designated by the control unit 10, data reading from the upstream buffer 46B is controlled so that the upstream optical signal is arranged in the time slot permitted for transmission. The transmission of the uplink radio signal is delayed until the transmission permission from the wireless control unit 10 is received. By obtaining the transmission permission whenever necessary, for example, a radio wave signal exceeding the allocated band can be received by the antenna. Even in the case of receiving at 60-1, it is possible to temporarily increase the allocated bandwidth and avoid failure.

  The optical multiplexer / demultiplexer 42 outputs the upstream optical signal from the optical transmitter 44B to the branch optical fiber 34-1 of the optical fiber link 30. The upstream optical signal propagates through the branch optical fiber 34-1, the optical splitter 36, and the optical fiber 32 of the optical fiber link 30 and enters the optical multiplexer / demultiplexer 18 of the radio control unit 10.

  The optical multiplexer / demultiplexer 18 of the wireless control unit 10 supplies the upstream optical signal from the optical fiber 32 to the optical receiver 16B. The optical receiver 16B converts the upstream optical signal from the optical multiplexer / demultiplexer 18 into an electrical signal, performs binary discrimination, parallelizes it, and stores it in the upstream buffer 14B.

  The deframing unit 12B is a device that performs processing reverse to that of the frame unit 48B, sequentially reads out CPRI frames stored in the uplink buffer 14B, and extracts an uplink radio signal from each CPRI frame. The extracted radio signal is transferred to another mobile terminal, a mail server, or various servers on the Internet via a host network.

  The control signals (transmission request signals in this example) from the radio transmission / reception units 40-1 to 40-n stored in the upstream buffer 14B are supplied to the transmission / band control device 20.

  In this way, the radio signal and the control signal are transmitted from the radio control unit 10 to the radio transmission / reception units 40-1 to 40-N and transmitted in the opposite direction.

  Processing of transmission request signals from the wireless transmission / reception units 40-1 to 40-n by the wireless control unit 10 will be described. This transmission request signal includes information for identifying the wireless transmission / reception units 40-1 to 40-n that are request sources, and information on the amount of traffic or data to be transmitted. The transmission / band control device 20 determines transmission permission / inhibition according to the transmission request signal from each of the wireless transmission / reception units 40-1 to 40-n. FIG. 3 shows a flowchart of the operation.

  When the transmission / band control device 20 receives a transmission request signal from any one of the radio transmission / reception units 40-1 to 40-n, for example, the radio transmission / reception unit 40-i (S1), the transmission / bandwidth control device 20 calculates the figure from the requested traffic amount. The bandwidth calculator 24 determines which of the four CPRI bit rates shown in FIG. 2 should be applied (S2). For example, the closest value among the four CPRI bit rates is searched by calculating the absolute value difference between the four CPRI bit rates with respect to the requested traffic volume.

  The bandwidth calculation device 24 refers to the monitoring result of the traffic monitoring device 22 and calculates the total bit rate of the uplink allocated bandwidth to all the radio transmission / reception units 40-1 to 40-n (S3). Then, it is determined whether or not the total bit rate is within a predetermined allocated bandwidth (S4).

  When the total bit rate exceeds the allocated bandwidth (S4), the allocated bandwidth for each of the radio transmission / reception units 40-1 to 40-n is recalculated (S5). As a recalculation method, for example, the CPRI bit rate is lowered by one step because the difference between the CPRI bit rate assigned to each of the radio transmission / reception units 40-1 to 40-n and the actual traffic amount is large.

  It is checked again whether the total bit rate is within the allocated bandwidth (S4). Steps S5 and S3 are repeated until the total bit rate is within the allocated bandwidth. When step S5 is executed from the second time onward, once the CPRI bit rate has been lowered, the CPRI bit rate is again set until the CPRI bit rate of all other radio transmission / reception units is lowered. Do not lower.

When the total bit rate yield or Tsu within allocated band (S4), and transmits the time slot information to be used for transmission to the requestor (S6). Then, the process returns to step S1 and waits for the next transmission request.

  A method for determining the allocated bandwidth for uplink transmission from each of the radio transmission / reception units 40-1 to 40-n to the radio control unit 10 will be described. The traffic monitoring device 22 monitors traffic of uplink transmission from each of the radio transmission / reception units 40-1 to 40-n to the radio control unit 10, and holds the time change of the traffic amount within a certain past time. The bandwidth calculation device 24 calculates the bandwidth allocated to each of the radio transmission / reception units 40-1 to 40-n by referring to the traffic amount information held by the traffic monitoring device 22 in accordance with the bandwidth calculation instruction from the transmission / bandwidth control device 20. To do. In addition, the bandwidth calculation is programmed in advance in the bandwidth calculation device 24 or the transmission / bandwidth control device 20 so as to be executed at a fixed time interval such as 10 minutes or 1 hour, or at a predetermined time interval for each time zone. It may be left.

  An example of bandwidth calculation by the bandwidth calculation device 24 will be described. The traffic monitoring device 22 quantitatively measures the daily fluctuation of the upstream traffic from each of the radio transmission / reception units 40-1 to 40-n (or the antennas 60-1 to 60-n), and calculates the past fixed time. It is held in a built-in storage device (traffic storage device). FIG. 4 shows an example of traffic information held by the traffic monitoring device 22.

Bandwidth calculating device 24, a wireless transceiver unit 40 from the transmission / bandwidth control unit 20 - 1 to 40 - when receiving a bandwidth calculation instruction is not specified n, by referring to the traffic information traffic monitoring device 22 is held, the past Based on the average value of the actual traffic volume for a certain period of time, the bandwidth of the optical fiber 32 is proportionally distributed to the wireless transmission / reception units 40-1 to 40-n.

In CPRI, as shown in FIG. 2, the transfer bit rate is selected from a plurality of candidates. In this case, the average traffic amount calculated for each radio transceiver units 40-1 to 40-n, in contrast to the band B ₁ .about.B ₄ shown in FIG. 2, such as the difference between the absolute value is smallest The bandwidth is determined as the allocated bandwidth. Of course, the total of the bandwidth allocated to each of the radio transmission / reception units 40-1 to 40-n is set to be within the uplink transmission rate of the optical fiber 32.

Or, the bandwidth of the optical fiber 32 after the prorated based on the average value of the actual traffic amount of each radio transceiver units 40-1 to 40-n, from the proportional distribution values of the band B ₁ .about.B ₄ shown in FIG. 2 The lower band may be the allocated band, and the remaining part may be a spare band for instantaneous upstream traffic.

  The bandwidth calculation device 24 notifies the transmission / bandwidth control device 20 of the determined allocated bandwidth. The transmission / band control apparatus 20 stores the allocated band information from the band calculation apparatus 24 for processing of uplink transmission requests from the radio transmission / reception units 40-1 to 40-n.

  The bandwidth calculation device 24 can instruct the bandwidth calculation device 24 to perform bandwidth calculation in which the transmission / bandwidth control device 20 designates any one of the wireless transmission / reception units 401 to 40n. This bandwidth calculation instruction includes information on the expected amount of uplink traffic that the specific radio transmission / reception unit 40-i intends to perform uplink transmission from now on.

  In response to this bandwidth calculation instruction, the bandwidth calculation device 24 adopts the average value of the scheduled uplink traffic volume and the past actual traffic volume for the designated radio transmission / reception unit 40-i, and designates the designated radio transmission / reception unit 40- For wireless transmission / reception units other than -i, refer to the average value of past actual traffic volume. Then, based on these average values, the bandwidth of the optical fiber 32 is proportionally distributed to each of the radio transmission / reception units 40-1 to 40-n. In order to match the band defined by the CPRI, the band may be matched with any band defined by the CPRI by the same method as described above.

  By such bandwidth allocation calculation, it is possible to allocate an appropriate upstream bandwidth even to a wireless transmission / reception unit in which upstream traffic suddenly or suddenly increases.

  As described above, in this embodiment, the uplink band from the radio transmission / reception unit to the radio control unit is dynamically adjusted according to the fluctuation of the traffic volume, so that the band of the optical fiber link 30 can be effectively used. It is possible to provide a radio base station system that realizes effective use of bandwidth.

  Note that the radio control unit 10 may designate the timing of uplink transmission from each of the radio transmission / reception units 40-1 to 40-n to the radio control unit 10 in advance every time bandwidth setting is set or changed. . In that case, each of the radio transmission / reception units 40-1 to 40-n does not transmit a transmission request to the radio control unit 10 for normal uplink transmission, and does not allocate the allocated bandwidth for a sudden increase in the amount of uplink traffic. A recalculation is requested from the transmission / bandwidth controller 20. The transmission / bandwidth control device 20 then causes the bandwidth calculation device 24 to recalculate the allocated bandwidth in accordance with this request.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

10: Radio control unit 12A: Framing unit 12B: Deframing unit 14A: Downstream buffer 14B: Upstream buffer 16A: Optical transmitter 16B: Optical receiver 18: Optical multiplexer / demultiplexer 20: Transmission / band control device 22: Traffic Monitoring device 24: Bandwidth calculation device 30: Optical fiber link 32: Optical fibers 34-1 to 34-n: Branch optical fiber 36: Optical splitters 40-1 to 40-n: Radio transmission / reception unit 42: Optical multiplexer / demultiplexer 44A: Optical receiver 44B: Optical transmitter 46A: Downstream buffer 46B: Upstream buffer 48A: Deframer 48B: Framer 50: RF signal processor 52: Frame controller 54: Transmission controllers 60-1 to 60-n :antenna

Claims (3)

A radio signal transmission system for transmitting radio signals between a mobile terminal and an upper network,
A plurality of wireless transmission / reception units each capable of wireless connection with the mobile terminal;
A wireless control unit that transmits and receives the wireless signal to and from the upper network;
An optical fiber link connecting the plurality of radio transmission / reception units and the radio control unit;
Each wireless transmission / reception unit includes request means for transmitting a transmission request signal to the wireless control unit when receiving a wireless signal to be transmitted to the wireless control unit ,
The radio control unit
A determination unit that determines whether or not the transmission request signal can be allocated within the uplink band of the optical fiber link ;
When the bandwidth required by the transmission request signal cannot be allocated, the uplink allocation bandwidth to the other radio transmission / reception unit having the largest difference between the uplink allocation bandwidth and the actual traffic volume is reduced to reduce the bandwidth for the transmission request signal. An adjustment means for enabling upstream bandwidth allocation;
Means for transmitting a transmission permission signal to the request source of the transmission request signal in a state that can be allocated within the upstream band of the optical fiber link
Wireless signal transmission system characterized by comprising and. The radio control unit
Traffic monitoring means for monitoring the traffic volume of radio signals from each radio transmission / reception unit toward the upper network;
The radio signal transmission system according to claim 1, further comprising: band calculation means for calculating an uplink allocated band from each radio transmission / reception unit to the radio control unit in accordance with a monitoring result of the traffic monitoring means. A plurality of wireless transmission / reception units each capable of wireless connection with a mobile terminal;
A wireless control unit that transmits and receives the wireless signal to and from the upper network;
An optical fiber link that connects the plurality of radio transmission / reception units and the radio control unit.
A wireless signal transmission system comprising: a method of transmitting the wireless signal between each mobile terminal and the upper network,
Each wireless transmission / reception unit, upon receiving a wireless signal to be transmitted to the wireless control unit, a request step for transmitting a transmission request signal to the wireless control unit;
A determination step for determining whether or not the radio control unit can allocate the transmission request signal within the uplink band of the optical fiber link;
When the radio control unit cannot allocate the band requested by the transmission request signal, it reduces the uplink allocated band to another radio transmission / reception unit having the largest difference between the uplink allocated band and the actual traffic amount. An adjustment step for enabling uplink bandwidth allocation for the transmission request signal,
The wireless control unit transmits a transmission permission signal to the request source of the transmission request signal in a state in which the wireless control unit can be allocated within the upstream band of the optical fiber link.
A wireless signal transmission method comprising:

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