JP4999566B2 - Guard interval length adaptive control method and communication system - Google Patents

Description

  The present invention relates to a guard interval length adaptive control method in a case where a guard interval (GI) is inserted into a data signal for transmission / reception.

  In wireless communication using an OFDM (Orthogonal Frequency Division Multiplex) method used in a wireless LAN or the like, a signal called a guard interval is inserted into a data signal in order to avoid intersymbol interference due to a multipath delayed wave. . In this guard interval, the end of the data portion in the symbol is duplicated and added to the head portion of the data. The interval between the direct wave and the delayed wave is called a delay spread, and the guard interval needs to be increased as the delay spread increases. The length of the guard interval varies depending on the state of the transmission path.

  In addition, it is known that in the communication method in which a guard interval is inserted into the data signal as described above, the transmission efficiency can be improved by shortening the length of the guard interval. As one of the methods, a method for estimating a maximum delay time from a received signal is disclosed.

  Further, in Patent Document 2 below, a method different from that in Patent Document 1 described below, that is, a process for reducing reception power from a receiver to a transmitter and reducing transmission power in the case of excessive quality or a modulation multi-value number A method is disclosed in which the guard interval is shortened by a link adaptation function, such as a process of dropping the threshold.

JP 2002-374223 A JP 2004-372856 A

  However, in the method of Patent Document 1, it is not only necessary to add a special signal for detecting a multipath in order to estimate the maximum delay time, but also a special circuit for detecting the multipath. Must be implemented. That is, by providing a special function for estimating the maximum delay time, there are problems such as deterioration in transmission efficiency, increase in circuit scale, and increase in power consumption.

  Further, the method of Patent Document 2 has a problem that transmission efficiency is deteriorated because feedback information is transmitted.

  The present invention has been made in view of the above, and without using a special function for estimating the maximum delay time, the guard interval capable of adaptively controlling the guard interval while avoiding deterioration of transmission efficiency. The purpose is to obtain a long adaptive control method.

  In order to solve the above-described problems and achieve the object, the guard interval length adaptive control method according to the present invention is provided between the master station and the slave station that can communicate within the area covered by the master station. A guard interval length adaptive control method in which a guard interval is inserted into a common control signal that can be transmitted and received with settings common to Slave stations and an individual control signal that can be transmitted and received with settings specific to each Slave station. A broadcast information transmission step in which the master station periodically transmits broadcast information as a common control signal for adaptively controlling a guard interval length; and a slave station that desires communication with the master station transmits the broadcast information Based on the information, send an association request as a common control signal, and the master station that received the request returns a random access response as a common control signal A random access step, an association response transmission step in which the master station transmits an association response as an individual control signal for assigning an identifier to the slave station that desires the communication, and a slave station that has received the association response An association completion transmission step for transmitting association completion as an individual control signal for notifying completion of association to the master station, and each slave station wishing to communicate with the master station The control signal is transmitted with the guard interval length set to an initial value based on the broadcast information. When the individual control signal cannot be normally received on the receiving side, the control signal is transmitted based on the broadcast information until reception is successful. The guard interval length is extended and transmission of individual control signals is repeated. It is characterized by being repeatedly executed.

  According to the present invention, it is possible to adaptively control the guard interval while avoiding deterioration of transmission efficiency without using a special function for estimating the maximum delay time.

  Embodiments of a guard interval (hereinafter referred to as GI) length adaptive control method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, each of the following embodiments is applicable to wired communication and wireless communication, and is particularly applicable to power line communication (PLC).

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a master station and a slave station included in a communication system for realizing the GI length adaptive control method according to the present invention. The Master station 1 in FIG. 1 includes a control unit 11, a receiving unit 12 that receives an uplink control signal, and a transmission unit 13 that transmits a downlink control signal, and is configured to be able to communicate with a plurality of Slave stations. The slave station 2 includes a control unit 21, a transmission unit 22 that transmits an uplink control signal, and a reception unit 23 that receives a downlink control signal.

  FIG. 2 is a diagram illustrating a basic control sequence between the Master station 1 and the Slave station 2. The master station 1 periodically transmits broadcast information as a control signal (step S1). A slave station (for example, slave station 2) that desires one-to-one communication with master station 1 receives the broadcast information and acquires information necessary for one-to-one communication with master station 1 ( Step S1).

  Thereafter, the slave station 2 transmits an association request by random access as a control signal indicating that one-to-one communication is to be started to the master station 1 (step S2). Since this association request is transmitted by random access, if the transmission timing overlaps with other Slave stations, the Master station 1 may not receive normally. Therefore, the master station 1 transmits a random access response as a control signal indicating whether or not this association request has been normally received (step S3). The slave station 2 can know whether or not the association request has been normally received by receiving this random access response.

  Further, if the master station 1 can normally receive the association request, it is necessary to give an identifier to the slave station 2 in order to start one-to-one communication with the slave station 2. Here, an association response is transmitted to the slave station 2 as a control signal for assigning an identifier (step S4).

  When the slave station 2 has successfully received the association response, the slave station 2 transmits association completion to the master station 1 as a control signal indicating that the association has been correctly received (step S5). Through this series of processing, one-to-one communication between the Master station 1 and the Slave station 2 becomes possible. Hereinafter, these series of procedures will be referred to as association processing.

  In the association process, the broadcast information, the association request, and the random access response need to be transmitted and received with a common setting that enables communication within the area covered by the master station 1. Such a control signal is called a common control signal. On the other hand, since the slave to be communicated is specified, the association response and the association completion are transmitted / received with a setting unique to the slave. Such a control signal is called an individual control signal.

  FIG. 3 is a diagram illustrating a frame configuration example in the case where communication between the Slave station 2 and the Master station 1 is realized by TDMA / TDD (Time Division Multiple Access / Time Division Duplex). The illustrated Downlink is a time for transmitting a signal from the Master station 1 to the Slave station 2, and Uplink is a time for transmitting a signal from the Slave station 2 to the Master station 1. At this time, the master station 1 transmits broadcast information using the BCH and transmits a random access response using the ACH. The association response and the association completion, which are one-to-one communication between the Master station 1 and the Slave station 2, are performed on the SCH / LCH, respectively, and the transmission / reception timing is determined by the Master station 1. The master station 1 notifies the slave station 2 of the transmission / reception timing determined above as a control signal transmitted on the FCH.

  In the case of transmitting a common control signal that enables communication within the covered area, the master station 1 according to the present embodiment transmits the GI length that is set to be the longest, and the slave station that communicates is specified. When transmitting a control signal (when Slave station 2 is specified as an example), the GI length is set to the shortest and transmitted. For the slave station 2 that starts the one-to-one communication, if the GI length of the individual control signal set as described above is too short, the sequence in FIG. 1 is not completed. The length is increased stepwise by a predetermined length. As a result, the sequence of FIG. 1 can be completed with an appropriate GI length for the Slave station 2. Since the master station 1 performs one-to-one communication with the slave station 2 using the GI length when the sequence in FIG. 1 is completed, one-to-one communication is realized with the shortest GI length that can be communicated. Can do.

  FIG. 4 is a diagram illustrating an example of a GI length adaptive control sequence according to the present embodiment when the master station 1 and the slave station 2 perform one-to-one communication. In steps S1 to S3, the master station 1 transmits and receives the common control signal with the GI length set to the longest as described above. Then, after executing Steps S1 to S3, the first association response and exchange of association completion are performed with the GI length set to the shortest (Steps S4 and S5). After that, if the GI length is too short for the slave station 2 to complete the control sequence normally, the master station 1 sets the GI length longer step by step until it succeeds, and exchanges the association response and the association completion. (Steps S4 ′ and S5 ′). FIG. 4 shows a case where an appropriate GI length is set by one retry as an example.

  Next, detailed operations of the Master station 1 and the Slave station 2 in the GI length adaptive control sequence will be described.

  FIG. 5 is a diagram showing a processing flow of the Master station 1. As a premise, the master station 1 broadcasts broadcast information including GI length control information to an area covered by the own station (corresponding to step S1 in FIG. 4). The GI length control information includes, for example, the number of association processing retries, an individual control signal GI length initial value, and an individual control signal GI length list. The number of association process retries indicates how many times to retry Step S4 and Step S5 in the association process. The individual control signal GI length initial value indicates the initial value (shortest GI length) of the GI length of the individual control signal. The master station 1 and the slave station that communicates with the master station 1 transmit and receive the individual control signal transmitted for the first time in the association process with the GI length indicated by this initial value. The individual control signal GI length list indicates a list of GI lengths applicable in association processing.

  In the above description, the individual control signal GI length list is notified when the next GI length is determined. For example, an equation is defined as information indicating how long the GI length is to be increased, and is substituted into the equation. The parameters to be notified may be notified, and this list may be known by the Master station and the Slave station. Further, the association processing retry count and the individual control signal GI length initial value may be known by the Master station and the Slave station.

  Also, the GI length of the individual control signal to be used at present is notified as a part of the transmission / reception timing control signal notified by the FCH. FIG. 6 shows an example. The transmission / reception timing control signal is composed of a slot number, transmission / reception classification, Slave-ID, slot length, and GI length. The slot number indicates the order of transmission / reception. The transmission / reception classification indicates whether the slot number is transmission from the Master station to the Slave station (denoted as DL) or transmission from the Slave station to the Master station (denoted as UL). Slave-ID indicates to which Slave station the slot number corresponds. The slot length indicates a transmission / reception time length (for example, corresponding to a symbol length) in the slot number. The GI length indicates the GI length in the slot number. However, the format is not limited to this format as long as the GI length in each slot number can be designated.

  Based on the premise process described above, the master station 1 first receives the RCH (step S11), and checks whether there is an error in the message received on the RCH (step S12). In order to indicate success / failure of the message, a random access response is transmitted on the ACH of the next frame (step S13).

  When the message received on the RCH is an association request from the Slave station 2 and is normally received, the Master station 1 generates an association response for assigning an identifier to the Slave station 2. And the timing which transmits an association response is determined (step S14), the control signal for notifying the timing is produced | generated, and it transmits by FCH. Thereafter, the master station 1 transmits an association response by SCH / LCH using the individual control signal GI length initial value notified to the slave station 2 (step S15). At this time, the failure counter is reset to “0”.

  Further, the master station 1 determines the timing at which the slave station 2 transmits the association completion (step S16), generates a control signal for notifying the timing, and transmits it by FCH.

  Next, when the master station 1 normally receives the association completion (step S17, step S18, Yes), the master station 1 enters the one-to-one communication enabled state, and ends the processing as it is. On the other hand, when there is an error in the completion of association and the signal cannot be received normally (including the case where the received signal cannot be detected: Step S17, Step S18, No), the Master station 1 counts up the failure counter (Step S17). S19). If the failure counter value does not exceed the association process retry count (No at Step S20), the GI length is increased by a predetermined length according to the individual control signal GI length list (Step S21), and the association response is transmitted again. Steps S14 and after are executed. However, if the failure counter value exceeds the number of association process retries in the process of step S20 (step S20, Yes), the master station 1 gives up the retransmission of the association response and stops the association process.

  FIG. 7 is a diagram showing a processing flow of the Slave station 2. When the slave station 2 receives the broadcast information from the master station 1, the slave station 2 transmits an association request using the RCH (step S31) and waits for a random access response transmitted on the ACH of the next frame. Then, when receiving the random access response (step S32) and recognizing that the association request has been received normally, the slave station 2 transmits an association response using the initial value of the individual control signal GI length obtained from the broadcast information. Wait for it to come. At this time, the failure counter is reset to “0”.

  While waiting for the association response to be transmitted, the slave station 2 receives the FCH every frame, and the association response becomes a reception error even though the timing at which the association response is transmitted on the FCH is notified. If it has occurred (step S33, step S34, No), the failure counter is counted up (step S35). If the failure counter value does not exceed the association processing retry count (No at Step S36), the GI length is increased by a predetermined length according to the individual control signal GI length list (Step S37), and the association response is transmitted again. Wait for On the other hand, if the failure counter value exceeds the association processing retry count in the process of step S36 (step S36, Yes), the slave station 2 gives up receiving the association response and stops the association process.

  If the association response is normally received in the process of step S34 (step S34, Yes), the slave station 2 confirms the transmission timing of the association completion by receiving the FCH for each frame, and completes the association completion at that timing. Transmit (step S38). However, after that, when the association response is retransmitted from the master station 1, the association completion is transmitted again at the transmission timing designated by the master station 1.

  As described above, in the present embodiment, first, a GI shorter than the common control signal is set in the individual control signal, and until the GI length adaptive control sequence is normally completed and the optimum individual control signal is set, The GI length of the individual control signal is increased stepwise. Thus, it is possible to adaptively control the guard interval while avoiding deterioration of transmission efficiency without using a special function for estimating the maximum delay time. In addition, since the GI is determined using the GI length adaptive control sequence, extra feedback information as shown in the prior art is not required.

  The reception error of the individual control signal is not only caused by the presence of a delayed wave exceeding the GI length. For example, a reception error occurs even when the distance between the Master station 1 and the Slave station 2 is long and the signal strength is weak. Therefore, in the present embodiment, the master station 1 measures a received signal strength indicator (RSSI) when receiving an association request, and if the measurement result is lower than a specific threshold, the slave station 1 It is possible to determine that an error is likely to occur because the distance to 2 is far away, and the GI length extension process in step S21 may not be performed. Alternatively, when a plurality of individual control signal GI length lists are prepared and the RSSI is low, the Master station 1 increases the GI length more slowly than when the RSSI is high, as shown in FIG. Also good.

  Further, the reception error of the individual control signal may occur when the noise power density is increased for some reason or when interference between the same channels is generated. Therefore, in the present embodiment, as shown in FIG. 9, it is possible to prepare an idle period in which neither the Master station 1 nor the Slave station 2 transmits in the frame. In this case, when the master station 1 measures RSSI in the section and the measurement result is higher than a specific threshold value, the noise power density is increased or interference between the same channels has occurred. Therefore, the GI length extension process in step S21 is not performed. Alternatively, when a plurality of individual control signal GI length lists are prepared and the RSSI is high, the Master station 1 makes the GI length longer slowly than when the RSSI is low, contrary to FIG. Also good. However, the length of the idle slot is variable and is notified by FCH.

  If a reception error of the individual control signal occurs due to interference between the same channels, the master station 1 changes the slot position in steps S14 and S16 at the time of retransmission, and extends the GI length until reception fails N times. The processing may be skipped and the GI length extension processing may be performed when the processing still fails.

  When a reception error of an individual control signal occurs due to an increase in noise power density or interference between the same channels, the Master station 1 increases the transmission power step by step every time an association response is retransmitted. The GI length extension process may be skipped until reception fails repeatedly, and if it still fails, the GI length extension process may be performed. Similarly, the slave station 2 increases the transmission power step by step for each retransmission of completion of association, skips the GI length extension process until it fails N times, and implements the GI length extension process if it still fails It is good to do.

  In addition, when a reception error of an individual control signal occurs due to an increase in noise power density or interference between the same channels, the master station 1 gradually decreases the modulation multi-value number every time an association response is retransmitted. (As an example, QPSK → BPSK), GI length extension processing may be skipped until reception fails N times, and if it still fails, GI length extension processing may be performed. Similarly, the slave station 2 gradually decreases the modulation multi-value number for each retransmission of association completion, skips the GI length extension process until it fails N times, and if it still fails, the GI length extension process It is good also as implementing.

  In addition, when a reception error of an individual control signal occurs due to an increase in noise power density or interference between the same channels, the Master station 1 decreases the coding rate step by step every time an association response is retransmitted ( As an example, the GI length extension process may be skipped until reception fails for N times, and the GI length extension process may be performed if it still fails. Similarly, the slave station 2 gradually decreases the coding rate for each retransmission of association completion, skips the GI length extension process until it fails N times, and if it still fails, performs the GI length extension process. It may be carried out.

  Further, the present embodiment can be applied to a communication system that applies a GI and equalizes delayed waves, for example, “Power Line Communication, 802.16e, 3GPP Evolved UTRA”.

Embodiment 2. FIG.
In the first embodiment described above, as shown in FIG. 6, the transmission / reception timing in each slave station is designated by the slot length (for example, the number of symbols). Also, as shown in FIG. 10, when the GI length is different, the slot length is different even with the same number of symbols. Therefore, when individual control signals of different Slave stations are mapped to the same frame, calculation of transmission / reception timing may be complicated if the GI of each Slave station is different.

  Therefore, in this embodiment, when individual control signals of different slave stations are mapped to the same frame, slave stations having the same GI length are arranged as shown in FIG. In the example on the upper side of FIG. 11, since slots are arranged without aligning GI lengths, it is necessary to calculate the transmission / reception timing every time at the slot breaks. However, in the lower example in FIG. 11, slots are arranged with the same GI length, so it is only necessary to calculate the transmission / reception timing in a slot where the GI length changes, and the amount of calculation is reduced compared to the upper example. be able to. The processing other than the above is the same as that in the first embodiment.

Embodiment 3 FIG.
In the first and second embodiments described above, since the GI length of the individual control signal of each slave station is changed in the control sequence shown in FIG. 4, the calculation of the transmission / reception timing may be complicated.

  Therefore, in the present embodiment, as shown in FIG. 12, the GI length of the individual control signal is adjusted to the worst value (longest GI length) of the Slave station. For example, in FIG. 4, the GI length of the individual control signal is gradually extended in a series of control sequences starting from the association request. However, in FIG. 12, for example, the control sequence shown in FIG. If normal reception is not possible with the GI length of, the GI lengths of the individual control signals of all the slave stations already connected are extended. Thereby, since the GI length of each Slave station can be made uniform, calculation of the transmission / reception timing of the individual control signal can be simplified.

  For example, the GI length change notification is a message for individually notifying each slave station of a change in the GI length. Upon receipt of this message, each slave station returns a GI length change notification receipt notification to notify the GI length change notification. And waits for the delay time specified in, extends the GI length from the current state, and transmits the association request again.

  In order to unify the standby start timing, the master station stops the BCH once, removes the synchronization of each slave station, extends the GI length from the current state, resumes the transmission of the BCH, and synchronizes each slave station. The established timing is set as the standby point. Also, the latest GI length is reported on the BCH. At this time, a sufficient delay time is set when the GI length change notification is performed so that the association request can be started again from the slave station that has failed the association request. Then, in the association request again by this Slave station, the GI length is extended until the association is completed.

  In the present embodiment, it is also possible to remember the slave station that failed in the association request and triggered the GI length change. For example, when this Slave station stops communicating with the Master station for some reason, the procedure shown in FIG. 12 can be applied to shorten the GI length. More specifically, the GI length broadcast on the BCH can be shortened. Further, when there is no Slave station that has failed the association request, it is not necessary to set a delay time as large as described above in the GI length change notification.

  As described above, the guard interval length adaptive control method according to the present invention is useful for wireless communication and wired communication in which a guard interval is inserted into a data signal to perform transmission / reception, and in particular, a special method for estimating the maximum delay time. This is suitable for communication that adaptively controls the guard interval without using a special function.

It is a figure which shows the structural example of the communication system for implement | achieving the GI length adaptive control method concerning this invention. It is a figure which shows the basic control sequence between a Master station and a Slave station. It is a figure which shows the example of a frame structure in the case of implement | achieving communication between a Slave station and a Master station by TDMA / TDD. It is a figure which shows an example of the GI length adaptive control sequence of this Embodiment. It is a figure which shows the processing flow of a Master station. It is a figure which shows an example of the control signal notified by FCH. It is a figure which shows the processing flow of a Slave station. It is a figure which shows an example of the separate control signal GI length list. It is a figure which shows the example of a frame structure. It is a figure which shows an example of the slot length when a GI length is long and when it is short. FIG. 10 is a diagram showing processing of the second embodiment. FIG. 10 is a diagram showing processing of the third embodiment.

Explanation of symbols

1 Master station 2 Slave station

Claims (10)

A common control signal that can be transmitted and received with the settings common to each slave station and an individual that can be transmitted and received with the settings specific to each slave station between the master station and the slave station that can communicate within the area covered by the master station A guard interval length adaptive control method in the case of transmitting and receiving by inserting a guard interval in each control signal,
The master station periodically transmits broadcast information as a common control signal for adaptively controlling the guard interval length, and
A random access step in which a slave station that wishes to communicate with the master station transmits an association request as a common control signal based on the broadcast information, and the master station that has received the request returns a random access response as a common control signal When,
An association response transmission step in which the Master station transmits an association response as an individual control signal for assigning an identifier to the Slave station that desires the communication;
An association completion transmission step in which the slave station that has received the association response transmits association completion as an individual control signal for notifying the master station of completion of association;
Including
Each slave station that wishes to communicate with the master station performs transmission of the first individual control signal with the guard interval length set to an initial value based on the broadcast information, and the individual control signal is normally transmitted on the receiving side. A guard interval length adaptive control method characterized in that, when reception is impossible, the guard interval length is extended stepwise based on the broadcast information and transmission of individual control signals is repeatedly executed until reception is successful.   The guard according to claim 1, wherein the broadcast information includes an allowable number of times of repeated execution, an initial value of a guard interval length of an individual control signal, and a list of guard interval lengths that are gradually extended. Interval length adaptive control method.   The master station measures the strength of the received signal in the random access step, and controls the guard interval length of the individual control signal repeatedly transmitted when the normal reception is not possible based on the measurement result The guard interval length adaptive control method according to claim 1 or 2.   The master station measures the signal strength using an idle period in which neither the own station nor the slave station transmits a signal, and based on the measurement result, the guard of the individual control signal that is repeatedly transmitted when the normal reception is not possible 3. The guard interval length adaptive control method according to claim 1, wherein the interval length is controlled.   2. The master station performs control to change a transmission timing of an individual control signal to be repeatedly transmitted when the master station cannot be normally received, and does not perform a guard interval length extension process for a predetermined number of repetitions. Or the guard interval length adaptive control method according to 2;   The master station performs control to increase the transmission power of the individual control signal repeatedly transmitted when the master station cannot be normally received, and does not perform the extension process of the guard interval length for a predetermined number of repetitions. The guard interval length adaptive control method according to claim 1 or 2.   The master station performs control to gradually reduce the modulation multi-level number of the individual control signal to be repeatedly transmitted when the master station cannot be normally received, and does not perform the guard interval length extension process over a predetermined number of repetitions. The guard interval length adaptive control method according to claim 1 or 2.   The master station performs control to gradually reduce the coding rate of the individual control signal to be repeatedly transmitted when the master station cannot be normally received, and does not perform the guard interval length extension process over a predetermined number of repetitions. The guard interval length adaptive control method according to claim 1 or 2.   9. A communication system, wherein a slave station capable of communicating within an area covered by a master station and the master station implements the guard interval length adaptive control method according to any one of claims 1 to 8.   10. The communication system according to claim 9, wherein when the master station maps the individual control signals of a plurality of slave stations to the same frame, the individual control signals having the same guard interval length are collectively arranged. .

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