JP2006313992A - Fixed wireless access network system and fixed base station thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed wireless access network system capable of realizing an efficient throughput as a whole by developing a wireless transmission system for performing a data transmission while distributing loads to radio frequency channels in a plurality of routing paths. <P>SOLUTION: In the fixed wireless access network system, transmission paths between two fixed base stations for transmitting signals are configured with a plurality of radio frequency channels, taking different relay paths. Each fixed base station includes a means 6 for detecting channel states of the radio frequency channels through the analysis of a received signal; a means 7 for distributing transmission data to each wireless link on the basis of the channel state; and means 8, 9 or the like, for selecting a transmission data rate variable modulation system for supplementing a difference between the transmission qualities and transmittable data rates between different wireless links to modulate a transmission signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixed radio access network system and a fixed base station thereof, and more particularly to a technique related to a transmission method in the system.

In recent years, a rapid realization of a broadband communication network using an optical fiber access link has been demanded. Realizing a broadband communication network that relies solely on the laying of optical fibers requires a large laying cost and time, and places where it is difficult to physically lay fiber cables.
Therefore, a broadband FWA network constructed by fixed wireless access (FWA) using a frequency of a quasi-millimeter wave band or higher capable of transmitting a broadband signal is expected as an alternative to an optical fiber network or a partial interpolation network.

In such a broadband FWA network, fixed base stations are installed at high density, and signals can be transmitted over a wide area by relaying signals to each other.
In addition, because fixed base stations are arranged at high density, there are usually multiple signal transmission (relay) paths between fixed base stations that want to transmit signals, and the communication quality of specific links deteriorates due to rain attenuation and interference. Even if a failure occurs in the path during signal transmission due to an unexpected failure of the relay station, it is expected to immediately adapt to this and bypass the signal transmission.

The conventional technology mainly relates to a technique for bypassing signal transmission, and a method in which a signal adaptively selects a transmission path based on various metrics and is routed to a desired station has been studied and verified. In the conventional study, each wireless relay station is regarded as a routing node in a wired network, and routing using existing routing protocols such as RIP and OSPF, or MLPS and VLAN technologies, or the radio for these routing protocols is optimal. The aim was to achieve high-speed and reliable route control to the destination base station. (See Non-Patent Document 1)

Kawakami et al., "Development of Broadband Millimeter-Wave Wireless Access System-(2) Routing Control Method Using VLAN-" 2002 IEICE General Conference B-5-325 page.776

  Basically, the conventional routing protocol is based on a wired network as a transmission medium. Although there is a viewpoint of the transmission band and the number of hops, it has a dynamic range due to radio rain attenuation and interference. It is not designed to be adaptable in consideration of degradation of channel quality.

  In addition, the existing routing protocol basically determines that the routing path is selected dynamically, and if the encoding method and the modulation method are selected, the transmission rate is inevitably lowered, but the transmission quality is maintained. There are many cases where network resources (frequency resources) are not effectively used because a link capable of data transmission is not used by changing a routing path.

FIG. 1 is a diagram for explaining occupation of network resources by a conventional routing protocol.
In FIG. 1, the case where all the links between the A station and the B station are good is the left column, and if the link state becomes poor due to rain attenuation between the A station and the B station as shown in the right column, the C station Switches to a relay link.
That is, assuming that each base has a potential transmission capacity of capacity C, the occupancy rate of all network resources is reduced from 1/3 to 1 to transmit the load transmission amount C between ABs. Change and use all remaining network resources.

In order to solve this, instead of switching all load transmission amounts to different paths, it is conceivable that the resources remaining in the direct link between the A station and the B station after load distribution are also effectively used. However, with the conventional technology, it was not possible to simultaneously transmit load-distributed signals to multiple radio links while successfully compensating for the difference in bandwidth and the difference in transmission rates between different radio relay links. .
The conventionally proposed method is not a method of providing a usage form in which traffic that is uniformly or non-uniformly load-distributed is transmitted while interpolating the difference in bandwidth and transmission quality of different radio links, but is not a resource in a radio station. For example, Patent Document 2 discloses a technique for distributing the load in the baseband signal processing means.

JP 2004-120070

  The present invention has been created in view of the above-described problems of the prior art, and has developed a wireless transmission system that distributes loads to wireless links in a plurality of routing paths and performs relay transmission, thereby improving overall throughput. An object of the present invention is to provide a fixed wireless access network system that can realize the above.

In order to solve the above problems, the present invention provides the following fixed radio access network system and its fixed base station.
FIG. 2 is an explanatory diagram for explaining the concept of the present invention. As shown in the figure, the present invention performs load distribution and transmits an appropriate data capacity even on a path whose link state has deteriorated. That is, for example, using the resource C / 4 remaining in the direct link between the A and B stations, the transmission path relaying the C station is limited to the transmission amount of 3C / 4, and occurs between the BC stations and the AC station. C / 4 can be free space.

  At this time, the occupation ratio of all network resources does not deteriorate from 1/3 to 1 even after the state transition, but remains at 4/5. Furthermore, since the direct link between the A and B stations is not used at the same time in the previous routing method, it can be said that the occupancy rate has been improved to 3/4 when compared with this assumption. This surplus can be allocated as a resource for data transmission between other bases, and as a result, the throughput of the entire network is improved.

  Accordingly, the invention according to claim 1 is a fixed wireless access in which fixed base stations connected by fixed wireless access (FWA) are installed at high density, and the fixed base stations perform signal transmission by relaying signals to each other. In the network system, a transmission path between two fixed base stations that perform signal transmission is configured by a plurality of different radio relay links that use the same or different radio frequency channels.

  The fixed base station detects and uses each of the available radio frequency channels by analyzing the detected signal in a wide band with a receiving means for detecting the received signal from the direction of the adjacent fixed base station that performs direct communication. Analyzing the status of the frequency channel determined to be possible, demodulating the received signal from the adjacent fixed radio station, and combining it into received data, while obtaining the channel status information obtained by the channel status detection analyzing means Each adjacent fixed base station adds channel status detection / analysis means added to transmission data, channel status information received from the adjacent fixed base station, and each channel's own channel status detection / analysis means according to the channel status information of the link Load distribution means for allocating relay transmission data destined for fixed stations, transmission quality and transmission possible between different radio links transmitting load-distributed data A data rate variable modulation unit that selects an appropriate transmission rate variable modulation method that compensates for a difference in data rate and modulates transmission data, and a transmission unit that transmits a transmission signal modulated for each radio link It is characterized by that.

  According to the second aspect of the present invention, the variable data rate modulation means performs modulation after encoding processing for performing error correction encoding at different coding rates independently for each transmission data addressed to each adjacent fixed base station. It is characterized by.

  The invention described in claim 3 is characterized in that the variable data rate modulation means performs different modulation independently in each radio frequency channel after a predetermined encoding process.

  According to a fourth aspect of the present invention, there is provided a direct spreading type or frequency hopping type code division multiplexing (VSF-CDM) system in which the variable data rate modulation means has a spreading factor variable structure after a predetermined encoding process. And a different spreading factor (SF) is used for each transmission signal addressed to each adjacent fixed station.

  According to a fifth aspect of the present invention, the variable data rate modulation means uses a variable spreading factor / orthogonal frequency code division multiplexing (VSF-OFCDM) system after a predetermined encoding process, A different spreading factor is used independently for each transmission signal addressed to a fixed station, and at the same time, a different value is used independently for the number of subcarriers used for transmission.

  In claim 6 and subsequent claims of the present application, a fixed base station constituting the fixed wireless access network system can be provided. That is, the fixed base station according to the present invention includes a receiving unit that detects a received signal from the direction of an adjacent fixed base station that performs direct communication in a wide band, and each radio frequency channel that can be used by analyzing the detected signal. The frequency channel status determined to be usable is analyzed and the received signal from the adjacent fixed radio station is demodulated and then combined into the received data, which is obtained by the channel status detection analyzing means. Channel status detection analysis means for adding the channel status information to the transmission data to each adjacent fixed base station, channel status information received from the adjacent fixed base station, channel status information of the link by the channel status detection analysis means of the own station, and Depending on the load distribution means that distributes relay transmission data addressed to each adjacent fixed station, and between different wireless links that transmit the load-distributed data A variable data rate modulation means for modulating transmission data by selecting an appropriate transmission rate variable modulation method that complements the difference between transmission quality and transmittable data rate, and transmitting a transmission signal modulated for each radio link A transmission means is provided.

  Further, a fixed base station can also be provided in each of the embodiments constituting the data rate variable modulation means as described above.

By the above means, the present invention has the following effects.
That is, in the conventional routing method, the link is not used for the link whose state has deteriorated because the link is switched selectively. On the other hand, in the present application, load ratio is distributed and an appropriate data capacity is transmitted without degrading the transmission quality of the data even in a path having a degraded transmission capability (resource), so that the occupation ratio of all network resources is extremely increased. Can be prevented.
The surplus of network resources can be distributed as resources for data transmission between other bases, and as a result, the throughput of the entire network is improved.

Hereinafter, embodiments of the present invention will be described based on examples shown in the drawings. The embodiment is not limited to the following.
FIG. 3 is an explanatory diagram showing the fixed wireless access network of the present invention. Fixed base stations A, B, and C are fixed base stations. Similarly, for each of the other fixed base stations, a fixed wireless access (FWA) is used between each fixed base station using a frequency of a quasi-millimeter wave band or higher. Is formed.

  A fixed base station is a wireless station that functions as a relay station that relays and transmits data signals to other fixed base stations at the same time that a plurality of mobile terminals (nomadic stations) perform wireless communication therewith. As a result, each mobile terminal can communicate with a mobile terminal that communicates with a different fixed base station. Such an FWA network is known, and communication between the mobile terminal and the fixed base station is not related to the present invention and will not be described in detail.

In the following, a technique for using radio links corresponding to a plurality of transmission paths in a fixed base station will be disclosed. Different transmission paths that are determined to be usable by fixed base stations by analyzing received signals include frequency bands that can be used in each path, interference conditions by other wireless terminals, channel quality conditions that depend on the propagation environment, etc. Different.
For this reason, a transmission method is required that complements or equalizes the difference between the transmission quality generated between different wireless links and the transmittable data rate.

Therefore, in the present invention, (a) a condition detection technique for each channel, (b) a technique for distributing transmission data (load) based on the detection information, and (c) a method suitable for the condition of the transmission link for the distributed signal The above transmission method is provided by three techniques, ie, a modulation technique.
That is, first, the receiving means of the fixed base station receives and demodulates the received signal for each radio link (receiving step).

As a technique of (a), the channel status detection / analysis means detects the channel status of each available radio frequency channel by analyzing the received signal (channel status detection analysis step).
The channel state detection / analysis means can use a known method for detecting the line state. For example, in order to search for usable frequency channels, frequency analysis is performed on signals received in a wide band, and each frequency channel is analyzed. The reception level may be analyzed. In addition, when analyzing the transmission quality of a channel that is supposed to be used, an FCS (frame check sequence) is added to the signal frame to be transmitted and received, and a frame error is detected on the receiving side based on this, thereby reducing rain attenuation. It is possible to analyze the status of link transmission quality due to interference.

  The data indicating the channel status of each radio link obtained by the channel status detection / analysis means in (a) is also accumulated in the load distribution processing circuit, and is added to the transmission data that has been load-balanced in the subsequent (b). Will be sent.

As a technique of (b), the transmission amount of each used channel is determined based on the channel state detection analysis step, and load distribution based on this is performed (load distribution step).
As for the method of determining the amount of transmission data load distribution, for example, if you learn from existing load distribution technology, the Enhanced Interior Gateway Routing Protocol (EIGRP), which is a typical routing protocol with a dynamic non-uniform load distribution function, is used. ) Can be realized by including the frame error rate of each radio link obtained in the above-described channel state detection analysis step as the cost value calculation for load distribution allocation.
As a calculation method, there is a method of performing load distribution from the viewpoint of equalization of error rate between wireless links. This is realized by the law that, when combined with any of the transmission rate variable modulation techniques in (c) below, a lower (good) error rate is obtained as the transmission rate is assigned lower.

In addition, for example, in combination with the technique (c) described later, each fixed base station assigns a variable modulation parameter for determining transmission capacity sequentially from a link with a poor channel condition, and variable modulation is performed until a required frame error rate is reached. A method of giving a feedback instruction to the transmission side so as to change the parameter can be considered.
In this way, even when the channel condition of the link with capacity C deteriorates as shown in FIG. 2 and the transmission capacity is reduced to C / 4 transmission capacity, the data amount of C / 4 is reduced to all other data in the channel. By distributing the load by relaying the link, the data amount of 3C / 4 may be distributed.

  A feature of the present invention is that a load is distributed to a plurality of available radio links based on their transmittable capacities and then transmitted to a destination fixed base station while maintaining the same transmission quality. As a method of distribution itself, a known method can be used. For example, a layer 2 ether packet may be distributed, or a layer 3 IP packet may be distributed.

Furthermore, as a technique of (c), the data rate variable modulation means of the fixed base station selects a transmission rate variable modulation method that complements the difference between the transmission quality between different radio links and the transmittable data rate, and modulates the transmission signal. (Transmission rate variable modulation step). Complementation involves different usable bandwidths depending on the radio links used, different link margins, and different amounts of interference.
Finally, the transmission means of the fixed base station transmits a transmission signal for each radio link (transmission step).

As described above, the present application has realized the wireless access method by the combination of the above (a) to (c), particularly the technology (c), which will be described in detail below.
As a first embodiment, the traffic distributed for different transmission links is subjected to error correction coding (Feed forward error correction) at different coding rates and transmitted independently, thereby being fixed differently. Provided is a method for compensating for a difference in transmission quality and a transmittable data rate between links addressed to a base station.

FIG. 3 shows a configuration diagram of the fixed base station in the first embodiment. This configuration is a fixed base station that performs error correction processing with different coding rates adaptively for baseband signals.
In this fixed base station, a receiving unit (3) and a transmitting unit (4) are provided for each of the plurality of radio links # 1 (1) to #N (2). The received signal received by the receiving unit (3) is input to the demodulator (5) and demodulated.

Further, the analyzer (6) analyzes the FCS and analyzes the frame error rate. Then, the received signals from the radio links (1) and (2) are input to the signal distribution processor (7), and desired received data is obtained as a fixed base station.
On the other hand, transmission data is first input to the signal distribution processor (7) and distributed to each channel. As described above, distribution is performed according to the number of channel errors in the analyzer (6). The distribution method is defined in advance by error rate analysis of the received signal from each link (1) (2) and error rate information on the transmission side of the link obtained from the demodulated data of the received signal, and the distribution amount is determined accordingly. May be.

  The distributed transmission data is input to the adaptive encoder (8) according to the present invention. In this adaptive encoder, the encoding rate is controlled so that the data rate is as constant as possible at the transmission stage input to the modulator. For the adaptive encoder (8), for example, Puncturing control in a convolutional encoder is suitable. In other words, when the rate is 1/2 in the convolutional encoder, a 4-bit redundant bit is added to the 4-bit input to obtain an 8-bit output, and a desired bit is thinned out from this. (Puncturing) makes it possible to obtain a desired coding rate. That is, the coding rate can be controlled adaptively by controlling this puncturing.

In addition, a BCH code, a turbo code having a high error correction capability, a Woven code, or an LDPC code can be used for the adaptive encoder.
In each radio link, the encoded transmission signal is modulated by the modulator (9) and transmitted from the transmission unit (4).
As described above, in this embodiment, the modulation / demodulation method is fixed, and the adaptive encoder controls the coding rate so that the signal distributed by the load sharing signal processing becomes a fixed transmission rate at the transmission stage, and is transmitted. .

  According to the configuration of the first embodiment, a method for adaptively correcting an error at a different coding rate for a signal whose load is distributed in the baseband region is based on the principle of the present system with a minimum modification to an existing modem. It is possible to apply.

Next, a second embodiment of the present invention will be described. In the present embodiment, the transmission quality and transmission rate between different radio links can be improved by transmitting the traffic distributed for different transmission radio links with RF carriers using different modulation schemes independently. It is a way to compensate for the difference.
FIG. 4 shows the configuration of a fixed base station according to the present embodiment. Constituent elements similar to those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In this embodiment, an adaptive modulator (10) is used instead of the adaptive encoder and modulator. The adaptive modulator (10) performs modulation by a modulation method suitable for the transmission rate of the signal distributed by load sharing signal processing. Although not shown, in this embodiment, an encoder with a fixed coding rate is arranged between the signal distribution processor (7) and the adaptive modulator (10).

  To change the modulation method, there is a method of adaptively switching between BPSK, WPSK, 8PSK, 16QAM, 64QAM, 128QAM, 256QAM, and even 1024QAM while the output symbol rate (occupied band) of the adaptive modulator (10) remains the same. . As a result, the transmission rate can be made variable and the tolerance against errors in each channel can be controlled.

  In the third embodiment of the present invention, a direct spreading (DS) type variable spreading factor and code division multiplexing (VSF-CDM) scheme is independently applied to traffic distributed for different transmission frequency channels. By using the RF carrier and modulating it, the modulation rate of the primary modulation is made variable so that the spreading factor (Spreading Factor) is controlled to reduce the difference between the transmission quality and the transmittable data rate between different channels. It is a way to complement.

FIG. 5 is a block diagram of a fixed base station in the present embodiment.
In this configuration, a primary modulator (11) and a secondary modulator (12) are provided, and the spreading factor is changed in the primary modulator (11). This configuration uses a variable spreading factor / code division multiplex modulation (VSF-CDM) with a variable expansion rate based on the DS-CDM system using a fixed chip rate, so that the transmission bandwidth required for the radio link is Only the resistance to interference can be controlled while remaining constant. That is, the spreading factor is decreased for a link with a low interference level and a high transmission capacity, and conversely, the spreading factor is increased for a link with a low transmission capacity.
Since this method depends on the CDM system, it can be expected to suppress interference signals using different code sequences (signals from fixed base stations that are not supposed to be received).

FIG. 6 assumes a DS (Direct Sequence) type CDM system as the CDM system. The upper part shows a signal waveform at a high transmission data rate, and the lower part shows a signal waveform at a low transmission data rate. It is assumed that high-speed data transmission is employed when the interfered signal level is small, and low-speed data transmission is employed when the level is large.
This figure shows a state where a double different transmission rate is realized by using a fixed chip rate and a fixed spreading code. Since the modulation method is simple, DS spreading of the bipolar signal of the BPSK signal is assumed.

In the upper part of FIG. 6, 2 bits are transmitted per spreading code, whereas only 1 bit is transmitted in the lower part, so the information transmission rate is halved.
However, the interference suppression effect is improved because the lower stage spreads the signal twice. In this way, by increasing or decreasing the number of bits transmitted in one spreading code sequence, it is possible to adjust the link transmission rate and tolerance to errors.

  As another embodiment of the third embodiment, a fixed base station provided with a data rate variable primary modulator (13) and a pattern variable frequency hopping synthesizer (14) as shown in FIG. 7 can be provided. A configuration that can control the transmission rate and the tolerance to interference while maintaining the physical transmission band required for the radio link by making the output by the spread spectrum method using the pattern variable frequency hopping synthesizer within a fixed frequency range It is possible to take

  In this case, the data rate variable primary modulation scheme is preferably a method such as limiting the number of subcarriers to be used by using, for example, a high-speed OFDM modulation / demodulation scheme rather than a symbol rate variable modulator / demodulator. FIG. 8 shows the adaptation situation (spectrum) of the fixed base station according to the present invention when the interference level of the link to be communicated within the allocated band is large (upper stage) and small (lower stage).

In the upper stage (link with a large level of interference), a signal can be transmitted with a high resistance to interference by reducing the transmission rate and performing frequency hopping (frequency spreading) over a relatively wide band.
In the lower stage (link with a small level of interference), the spreading rate due to frequency hopping (frequency spreading) decreases as the transmission rate is increased, and interference resistance is sacrificed.
In the most extreme case (link of non-interference level 0), transmission is possible as a link with a spreading factor of 1 (no spreading). That is, the entire usable band is used for signal transmission without performing frequency hopping at all.

  Finally, as a fourth embodiment of the present invention, traffic distributed for different radio links is transmitted independently on an RF carrier modulated using the VSF-OFCDM modulation scheme, and the expansion rate (Spreading) Describes how to compensate for differences in transmission quality and transmittable data rate between different channels by controlling Factor. Note that the physical occupied frequency band can be controlled by controlling the number of subcarrier frequencies used in the modulation method.

FIG. 9 shows a configuration diagram of the fixed base station in the present embodiment. This fixed base station includes a VSF-OFCDM modulator (15).
This configuration is based on the VSF-OFCDM system, and the transmission bandwidth required for the radio link remains constant, greatly improving the frequency utilization efficiency and adapting to interference conditions, rainfall attenuation, etc., and only the line margin. There are features that can be adaptively controlled.

  Specifically, the signal distributed by the load sharing process is encoded by an appropriate method and input to the VSF-OFDM modulator. Transmission is performed with a small spreading factor for a link with a high transmission capacity (a link with a good error condition) and with a large spreading factor for a link with a low transmission capacity (a link with a bad error condition). In addition, since it depends on the CDM system, it can be expected to suppress interference signals using different code sequences (signals from fixed base stations that are not supposed to be received).

  FIG. 10 is a block diagram of the VSF-OFCDM modulator, and FIG. 12 is the demodulator. Although the modulator / demodulator of the VSF-OFCDM is known, it has the Variable SF controller (spreading rate adjusting unit) (20) in FIG. 10, and adjusts the spreading rate by the control from the analyzer (6). At this time, by controlling the Spreading Factor (frequency domain, time domain) shown in FIG. 11, it is possible to arbitrarily set the tolerance for the transmission rate and the channel condition.

  The basic configurations and operations of the VSF-OFCDM modulator and demodulator are also well known, but will be briefly outlined based on FIGS. 11 and 13. Input data is appropriately encoded by a channel encoder and then converted to a data stream appropriately modulated by a data modulator. This is converted into a plurality of data series by a serial / parallel conversion circuit and then interleaved by an interleaver.

If the data sequence obtained here is converted by IFFT and parallel / serial converted, and then a guard interval is added, it becomes a normal OFDM signal. However, in VSF-OFCDM, each data sequence before IFFT conversion is desired. After preparing data copied by the spreading factor in the frequency direction, the code sequence from the spreading code generator is further multiplied and code-multiplexed.
The frequency spreading factor can be controlled by controlling the number of copies in the frequency spreading direction at this time. Also, the time spreading factor can be controlled by controlling the code generator output. The operation of the demodulator is omitted because it is mainly the reverse operation of the modulator based on the operation of the OFDM demodulator.

According to this method, even when a new interference station is generated, each relay station can control the spreading factor in an autonomous and distributed manner so that it can converge to a certain optimum network state.
In addition, since the methods of Embodiments 2 to 4 perform load distribution transmission processing in the RF modulation method, they contribute to high-speed and low-delay processing, and a wide range of transmission efficiency parameters can be selected.

It is explanatory drawing explaining the occupation state of the link in a prior art. It is explanatory drawing explaining the occupation state of the link in this invention technique. 1 is an overall configuration diagram of a fixed wireless access network system according to the present invention. It is a block diagram of the fixed base station which concerns on Example 1 of this invention. It is a block diagram of the fixed base station which concerns on Example 2 of this invention. It is a block diagram of the fixed base station which concerns on Example 3 (the 1) of this invention. It is a signal waveform in the same Example. It is a block diagram of the fixed base station which concerns on Example 3 (the 2) of this invention. It is a signal spectrum in the same Example. It is a block diagram of the fixed base station which concerns on Example 4 of this invention. It is a block diagram of a VSF-OFCDM modulator according to the same embodiment. It is explanatory drawing explaining how to define a spreading | diffusion rate parameter. It is a block diagram of the VSF-OFCDM demodulator according to the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Received signal 2 Transmitted signal 3 Receiver 4 Transmitter 5 Demodulator 6 Analyzer 7 Signal distribution processor 8 Adaptive encoder

Claims (10)

A fixed wireless access network system in which fixed base stations connected by fixed wireless access (FWA) are installed at high density, and the fixed base stations perform data communication by relaying signals to each other,
In a fixed radio access network system in which a transmission path between two fixed base stations that communicate in a fixed radio access network can have a plurality of different relay paths configured by the same or different radio frequency channels.
The fixed base station includes
Receiving means for detecting a received signal from the direction of an adjacent fixed base station that performs direct communication in a wide band;
By analyzing the detected signal, each available radio frequency channel is detected, and the status of the frequency channel determined to be usable is analyzed,
Channel status detection in which the received signal from the adjacent fixed radio station is demodulated and then combined into the received data, while the channel status information obtained by the channel status detection analysis means is added to the transmission data to each adjacent fixed base station Analysis means;
Load distribution means for allocating relay transmission data addressed to each adjacent fixed station according to the channel status information received from the adjacent fixed base station and the channel status information of the link by the channel status detection analysis means of the own station;
Data rate variable modulation means for modulating transmission data by selecting an appropriate transmission rate variable modulation method that complements the difference between transmission quality generated between different wireless links transmitting load-balanced data and the transmittable data rate ,
A fixed radio access network system comprising: a transmission means for transmitting a transmission signal modulated for each radio link. 2. The fixed radio access network system according to claim 1, wherein the data rate variable modulation means modulates after encoding processing for performing error correction encoding at different coding rates independently for each transmission data addressed to each adjacent fixed base station. . The fixed radio access network system according to claim 1, wherein the data rate variable modulation means performs different modulation independently in each radio frequency channel after a predetermined encoding process. The data rate variable modulation means uses a direct spreading type or frequency hopping type code division multiplexing (VSF-CDM) system having a variable spreading factor structure after a predetermined encoding process, and each adjacent fixed It is characterized by using a different spreading factor (SF) for each transmission signal addressed to the station,
The fixed wireless access network system according to claim 1. The variable data rate modulation means uses a variable spreading factor / orthogonal frequency code division multiplexing (VSF-OFCDM) system after a predetermined encoding process, and is independently different for each transmission signal addressed to each adjacent fixed station At the same time as using the spreading factor, use different values for the number of subcarriers used for transmission.
The fixed wireless access network system according to claim 1. A fixed base station constituting a fixed wireless access network system in which fixed base stations connected by fixed wireless access (FWA) are installed at high density, and the fixed base stations perform data communication by relaying signals to each other. ,
In a configuration in which a transmission path between two fixed base stations that communicate in a fixed radio access network can take a plurality of different relay paths configured by the same or different radio frequency channels,
Fixed base station
Receiving means for detecting a received signal from the direction of an adjacent fixed base station that performs direct communication in a wide band;
Analyzing the detected signal to detect each available radio frequency channel, analyze the status of the frequency channel determined to be usable, and demodulate the received signal from the adjacent fixed radio station, Channel status detection analysis means for adding the channel status information obtained by the channel status detection analysis means to the transmission data to each adjacent fixed base station, while combining the received data
Load distribution means for allocating relay transmission data addressed to each adjacent fixed station according to the channel status information received from the adjacent fixed base station and the channel status information of the link by the channel status detection analysis means of the own station;
Data rate variable modulation means for modulating transmission data by selecting an appropriate transmission rate variable modulation method that complements the difference between transmission quality generated between different wireless links transmitting load-balanced data and the transmittable data rate ,
A fixed base station of a fixed radio access network system, comprising: a transmission unit configured to transmit a transmission signal modulated for each radio link. 7. The fixed radio access network system according to claim 6, wherein the data rate variable modulation means modulates after encoding processing for performing error correction encoding at different coding rates independently for each transmission data addressed to each adjacent fixed base station. Fixed base station. The fixed base station of the fixed radio access network system according to claim 6, wherein the data rate variable modulation means performs different modulation independently in each radio frequency channel after a predetermined encoding process. The data rate variable modulation means uses a direct spreading type or frequency hopping type code division multiplexing (VSF-CDM) system having a variable spreading factor structure after a predetermined encoding process, and each adjacent fixed It is characterized by using a different spreading factor (SF) for each transmission signal addressed to the station,
The fixed base station of the fixed wireless access network system according to claim 6. The variable data rate modulation means uses a variable spreading factor / orthogonal frequency code division multiplexing (VSF-OFCDM) system after a predetermined encoding process, and is independently different for each transmission signal addressed to each adjacent fixed station At the same time as using the spreading factor, use different values for the number of subcarriers used for transmission.
The fixed base station of the fixed wireless access network system according to claim 6.