JP2008187369A - Communication method, and radio communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that spatial/temporal continuities of radio wave propagation path characteristics of signal in up time slot and those of signal in down time slot decrease and communication quality decreases as the moving speed of a terminal becomes faster. <P>SOLUTION: A radio communication device (100) has an information acquiring unit (120) which acquires information regarding the moving speed of the other device and a slot allocating unit (130) which selects and allocates an up time slot and a down time slot according to the acquired information on the other device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication method and a wireless communication apparatus.

  Conventional time division systems that use time slots include systems such as PHS (Personal Handy phone System) and iBurst (registered trademark) that use the TDMA-TDD (Time Division Multiple Access-Time Division Duplex) communication method. Yes, each is specified in “ARIB STD-28 (ARIB)” and “High Capacity-Spatial Division Multiple Access (HC-SDMA) WTSC-2005-032 (ATIS / ANSI)”. In current standards and communication systems using such a TDMA-TDD system, the time sequence in the upstream time slot is equal to the time sequence in the downstream time slot (upstream / downstream slot order synchronization method). Are assigned to each terminal.

In the conventional communication system described above, for example, on the basis of some control information obtained from the uplink time slot signal received by the base station, some adjustment (for example, antenna superposition coefficient) is made to the downlink time slot signal paired with this uplink time slot signal. ) And send the adjusted signal to the terminal. This is because there is spatial / temporal continuity between the radio wave propagation path characteristics of the upstream time slot signal and that of the downstream time slot signal (that is, the radio wave propagation environment of the uplink and that of the downlink are almost the same). ). Such control is sufficiently practical when the terminal is stationary, or when walking or getting on low-speed transportation.
JP-A-10-257009

  However, when the terminal moves at a high speed, the base station and the uplink time slot signal are not matched with the directivity control information obtained from the uplink time slot signal received by the base station (for example, the antenna superposition coefficient of the adaptive array antenna). Even if the directivity of the downlink time slot signal is adjusted, the terminal moves a considerable distance during the time difference Δt between the uplink time slot and the downlink time slot, and the base station appropriately adjusts the directivity. In some cases, it becomes impossible to control. As a result, there has been a problem that the communication quality deteriorates, such as the reception level of the terminal being reduced, the probability of occurrence of a reception error increasing, or fading occurring. That is, as the moving speed of the terminal increases, the radio wave propagation path characteristics of the upstream time slot signal and the spatial / temporal continuity with that of the downstream time slot signal decrease (that is, the radio wave propagation environment can be tracked). Communication quality may be reduced.

  Therefore, an object of the present invention is to ensure the continuity between the radio wave propagation path characteristic of the upstream time slot signal and that of the downstream time slot signal according to the moving speed of the terminal (that is, to the change of the radio wave propagation environment). It is to provide a technique (a communication method and a radio communication apparatus) that selects and assigns uplink and downlink time slots and prevents a deterioration in communication quality.

In order to solve the above-mentioned problems, the communication method according to the first invention is:
Communication in a wireless communication device that uses a time division multiple access / time division duplex method having a plurality of time slots and controls a signal in a downstream time slot based on an upstream time slot signal in wireless communication with another device A method,
An acquisition step of acquiring information on the moving speed in the other device (moving speed, fading amount in the radio wave propagation path, maximum Doppler frequency, etc.);
An allocation step of selecting and assigning the uplink time slot and the downlink time slot (from an empty slot) according to the acquired information of the other device;
Have

The communication method according to the second invention is
The assigning step comprises:
Select and assign the uplink time slot and the downlink time slot so that the time difference between the uplink time slot and the downlink time slot becomes shorter as the other device having a higher moving speed of the acquired information. ,
It is characterized by that.

The communication method according to the third invention is
There are a plurality of time slot pairs in which the time sequence of the upstream time slot is equal to the time sequence of the downstream time slot,
The assigning step comprises:
One time slot pair is selected from the plurality of time slot pairs so that the time difference between the upstream time slot and the downstream time slot becomes shorter as the other device having a higher moving speed of the acquired information. Assign
It is characterized by that.

A communication method according to the fourth invention is:
The time interval of the uplink time slot is different from the time interval of the downlink time slot (uplink / downlink time asymmetric time slot method),
It is characterized by that.

  As described above, the solution of the present invention has been described as a method. However, the present invention can be realized as a device, a program, and a storage medium storing the program substantially corresponding to these, and the scope of the present invention. It should be understood that these are also included.

For example, a wireless communication apparatus (base station apparatus or the like) according to the fifth aspect of the present invention that realizes the present invention as an apparatus
A wireless communication device that uses a time division multiple access / time division duplex method having a plurality of time slots in wireless communication with other devices and controls a signal in a downstream time slot based on an upstream time slot signal. And
According to the information acquisition unit for acquiring information about the moving speed in the other device (moving speed, fading amount in radio wave propagation path, maximum Doppler frequency, etc.) and the acquired information of the other device (free A slot allocation unit that selects and allocates the uplink time slot and the downlink time slot (from the slot);
Have

  According to the present invention, the uplink and downlink time slots are selected according to the moving speed of the terminal so as to ensure the continuity between the radio wave propagation path characteristics of the uplink time slot signal and that of the downlink time slot signal. Allocation and deterioration of communication quality can be suppressed. That is, according to the movement state of the terminal, it is possible to appropriately follow the change in the radio wave propagation environment between the uplink and the downlink, and it is possible to provide more stable communication.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Prior to description of the principle and configuration of the present invention, a communication system, a time slot configuration and the like targeted by the present invention will be described.

<Adaptive antenna array>
As an example of a communication system targeted by the present invention, an adaptive antenna array system will be described. An adaptive antenna array having a plurality of antenna elements is typically implemented in a base station. When implemented in the base station, it is possible to suppress the interference wave included in the uplink reception wave and to estimate the arrival path of the desired wave by deriving the antenna weight by reception. The adaptive antenna array also ensures communication quality by setting the transmit antenna weight so that SINR (Signal to Interference and Noise Ration) is maximized for the wireless terminal to be estimated and the signal is suppressed otherwise. However, since the link capacity can be drastically increased, research has become active recently. As an example of actual operation, there is an iBurst (registered trademark) system that conforms to “High Capacity-Spatial Division Multiple Access (HC-SDMA) WTSC-2005-032 (ATIS / ANSI)”.

<TDMA-TDD and antenna array>
The TDMA-TDD system uses the same frequency for the uplink channel from the radio terminal to the base station and the downlink channel from the base station to the radio terminal, so the antenna weight obtained by reception is theoretically calculated. It can be used for top transmission. For this reason, it has the advantage that the performance improvement using an antenna array is easy to be obtained. In other words, in the same frequency band in a short period, it is assumed that there is continuity between the transmission path itself and the propagation characteristics in the propagation path between an arbitrary point and other arbitrary points, and the transmission path obtained by uplink reception It is assumed that the antenna superposition coefficient matching the above can be used for downlink transmission. In general, this assumption has sufficient practicality when the interval (time difference) between the received signal (uplink time slot signal) and the transmission signal (downlink time slot signal) used for estimation is short and the moving speed of the wireless terminal is slow. .

<Method for obtaining antenna weight>
The Winner solution is well known as the antenna weight, and the method of obtaining the winner solution is to minimize the mean square error (MSE) between the training signal (reference signal) and the received signal from the receiving antenna array. It is known that sequential updating by an algorithm is often used. As this adaptive algorithm, the LMS (Least Mean Square) algorithm is often used. A known training signal is required for the LMS algorithm. This is because the wireless terminal generally assigns a known training signal pattern shared between the base station and the wireless terminal to the beginning or end of the uplink signal, or both. In a base station, a method of using a known pattern as a training signal is often used.
<Advantage of Asymmetry of Up / Down Slot of TDMA-TDD>
Examples of the use of the Internet for general users include browsing the web and browsing video / audio streaming files on a server. Such so-called server-client type connections often have a feature that the amount of data in the downlink direction is much larger than the amount of data in the uplink direction. In such a case, for example, as seen in ADSL and Special Table 2006-501768, the bandwidth in the uplink direction and the bandwidth in the downlink direction are made asymmetrical so that the bandwidth in the downlink direction is increased. It is known to increase convenience.

  However, since the TDMA-TDD multiple multiplexing scheme uses the same frequency in the uplink direction and the downlink direction, it is necessary to prevent the slots in the uplink direction and the downlink direction from overlapping in time. Therefore, when one frame is formed by alternately repeating the uplink direction and the downlink direction, it has a drawback that it is difficult to connect to a wireless terminal that is separated from the base station by a certain distance. That is, in order for the transmission signal of the wireless terminal to reach the reception position defined by the base station, the wireless terminal needs to emit the transmission signal in advance according to the distance. In Special Table 2006-501768, as shown in Fig. 2, three uplinks and three downlinks are arranged in succession, and are expanded between the downlink slot group and the uplink direction group. A frame structure has been proposed in which, when a guard time is provided and the wireless terminal is far from the base station, the wireless terminal has room to advance and transmit a transmission signal in the uplink direction in time.

  FIG. 2 is a frame configuration diagram proposed in “High Capacity-Spatial Division Multiple Access (HC-SDMA) WTSC-2005-032 (ATIS / ANSI)”. As shown in the figure, the frames are logically divided, and the uplink / downlink constitutes three TDMA-TDD slots each.

  The wireless terminal can rewrite FIG. 2 as shown in FIG. 3 in order to determine the uplink transmission timing based on the downlink reception slot. When the uplink transmission signal is emitted from the antenna end of the wireless terminal, it is delayed according to the distance from the base station. When the propagation speed of radio waves is 300000Km / sec, based on the timing when the downlink signal from the base station arrives at the antenna end of the wireless terminal, uplink transmission is possible by transmitting 1μsec earlier per 150m distance from the base station Since the signal arrives at the antenna end of the base station at the correct timing, if the position of the wireless terminal is 12.6 Km from the base station, the wireless terminal will transmit the uplink transmission timing 84 μsec earlier, the uplink of the base station It can arrive at a timing that matches the reception timing. FIG. 4 shows the timing at the antenna end of the wireless terminal in this case.

  FIG. 1 is a block diagram of a wireless communication apparatus according to an embodiment of the present invention. As shown in the figure, the wireless communication device 100 includes a control unit 110 that controls the entire device, an information acquisition unit (speed information acquisition unit) 120, a slot allocation unit 130, a communication unit 140, a storage unit 150, an antenna ANT. With. The control unit 110 uses a time division multiple access / time division duplex method having a plurality of time slots in radio communication with other devices, and controls the signals of the downlink time slots based on the signals of the uplink time slots. . The information acquisition unit (speed information acquisition unit) 120 acquires movement speed information in the other device for each other device. This “moving speed information” is information relating to the relative moving speed between the own apparatus and another apparatus with which it is communicating, and when the own apparatus is a base station apparatus and is stationary, It is the moving speed itself. This movement speed information may be acquired by the own apparatus, or movement speed information measured on the communication partner side may be received from the communication partner. A method for calculating the moving speed will be described in detail later. Further, the slot allocation unit 130 selects and allocates the uplink time slot and the downlink time slot from the empty slots according to the moving speed information for each other device. The communication unit 140 communicates with other devices (terminals) via the antenna ANT using the slot pairs assigned by the slot assignment unit 130.

  The slot allocation unit 130 refers to an upper and lower slot time difference table stored in the storage unit 150 as shown in Table 1, for example. Table 1 shows a virtual slot configuration for explaining the time difference to which the present invention is focused. The time interval of each slot and guard time is virtual, and actually, the slot is classified by frequency band and multiple space number. There are pairs. It is assumed that all three slot pairs in Table 1 are empty slot pairs, the time interval of the upstream time slot is 500 μs, the time interval of the downstream time slot is 1000 μs, and the guard time is 100 μs. The slot allocation unit 130 refers to this table, selects a slot pair U1-D1 having the shortest time difference for a terminal whose moving speed is larger than a predetermined first threshold, and allocates the selected terminal to the terminal. Since the slot pair has the shortest time difference between the upper and lower slots, the communication quality is the least susceptible to fluctuations in the radio wave propagation environment (highest fading resistance) among the three slot pairs even when the moving speed of the terminal is high. High slot pair. On the other hand, for a terminal whose moving speed of the terminal is smaller than the predetermined second threshold, the slot assignment unit 130 selects the slot pair U3-D3 having the longest time difference and assigns it to the terminal. Since this slot pair has the longest time difference between the upper and lower slots, among these three slot pairs, the slot pair is most susceptible to fluctuations in the radio wave propagation environment as the moving speed increases, but this terminal has a low moving speed. Therefore, there is no problem because the possibility that the communication quality is lowered is low.

  It is assumed that a time slot pair of “uplink / downlink slot order synchronization scheme” in which the time-series order in the uplink time slot and the time-series order in the downlink time slot are the same as shown in Table 1 is assigned to each terminal. To do. However, the present invention is not limited to such an “uplink / downlink slot order synchronization method”, and the time-series order in the uplink time slot is not necessarily equal to the time-series order in the downlink time slot. The present invention is applicable even when the “slot order asynchronous method” is adopted. That is, Table 2 shows the “ascending / descending slot order asynchronous method”, and the time slot pair U3-D1 having the shortest time difference has the highest fading tolerance (speed tolerance) in Table 1 because the time difference between the upper and lower slots is 600 μs. Since the time difference is about 1/3 of the slot pair U3-D1, the slot pair can provide excellent communication quality even at a higher moving speed.

<Acquisition of moving speed of wireless terminal>
A method for acquiring the moving speed will be described. As a method for obtaining the relative speed between the base station and the wireless terminal, there are a method for obtaining the moving speed of the wireless terminal on the base station side and a method for measuring the moving speed of the wireless terminal on the wireless terminal side. As a method of knowing the relative speed with the wireless terminal on the base station side, there is a method of obtaining from a signal arrival timing. In "High Capacity-Spatial Division Multiple Access (HC-SDMA) WTSC- 2005-032 (ATIS / ANSI)", the radio terminal transmits broadcast information transmitted by the base station to synchronize with the downlink signal transmitted by the base station. Monitor the channel burst periodically to adjust the receiving position. After determining the reception position, the wireless terminal transmits a configuration channel burst to the base station in order to know the uplink transmission timing according to the distance from the base station. The base station returns a configuration burst including difference information from the reception position of the configuration channel burst to the original uplink reception position to the wireless terminal. The wireless terminal adjusts the transmission timing based on the difference information obtained from the base station. At this time, the base station can obtain the distance from the base station of the wireless terminal from the difference information of the same wireless terminal, and performs control to record the difference information for a plurality of times in the past. By examining the change, the relative speed from the base station of the wireless terminal can be obtained. Since the time difference information is shared by the wireless terminals, the relative speed information acquisition unit can be easily implemented on the wireless terminal side.

<Radio resource allocation method>
In a communication method using TDMA-TDD, radio resources used for a traffic channel are determined by a TDMA-TDD slot and a frequency channel. In other words, 24 traffic channels can be prepared when 3 times are multiplexed by TDMA-TDD and 8 frequency channels can be used. However, the TDMA-TDD scheme requires a channel for synchronization with a base station, and one or more radio resources are used as, for example, a broadcast information channel and cannot be used as a traffic channel in many cases. Among these traffic channels, traffic channels that are not used can be used. As a method of determining the unused state, the radio terminal side measures the interference wave of the uplink radio channel resource. There is a way to fire a start request signal. It is known that the use of the slotted ALOHA algorithm as defined in “ARIB STD-28 (ARIB)” increases the possibility of smooth re-resource selection during a collision.

  When implementing spatial multiplexing using an antenna array on the base station side, the traffic channel can be doubled by the number of spatial multiplexing by the management of the base station, and interference wave measurement on the wireless terminal side is meaningless There is. In such a case, the wireless terminal transmits a traffic channel establishment request signal according to the slotted ALOHA algorithm using the uplink traffic channel of the radio resource selected at random without performing interference wave measurement. On the base station side, control is performed to open a traffic channel when radio resources are available. In “High Capacity-Spatial Division Multiple Access (HC-SDMA) WTSC- 2005-032 (ATIS / ANSI)”, the traffic channel establishment signal and the training signal on each traffic channel of traffic channel spatial multiplexing number 3 Spatial multiplexing is realized by dividing patterns.

  The base station determines the superposition coefficient of the transmission antenna in the corresponding transmission slot in the downlink direction based on the training signal included in the reception signal in the reception slot in the uplink direction. In one TDMA-TDD frame, Since there are slots of other channels in the reception slot, a gap is included in time, which is the reason why an error is included in the determination of the superposition coefficient of the transmission antenna in the downlink direction.

  Since the time gap is not uniform in each slot, for example, a difference in beam forming performance due to a superposition coefficient of a transmission antenna appears between a slot with a small time gap and a slot with a large time gap. This causes a problem when the moving speed of the wireless terminal is fast. When the wireless terminal moves, the influence of Doppler fading occurs due to the influence of the relative speed with the base station. Since Doppler fading increases as the moving speed of a wireless terminal increases, the possibility that an optimal signal can be transmitted to the wireless terminal decreases even if a downlink signal is transmitted using the transmission superposition coefficient obtained by reception. End up. In addition, if the time difference between the uplink slot and the downlink slot is 1645 μsec, it moves 11 cm when the speed is 240 Km / Hour, but this is 18 cm in the downlink slot 3 from the worst slot uplink slot 3 Distance. The longer the moving distance, the higher the possibility that the characteristics of the transmission path are altered. In other words, the slot that comes later refers to information with poor conditions, and the wireless terminal receives the optimal signal even if the downlink signal is transmitted using the transmission superposition coefficient obtained by reception due to the influence of fading. This reduces the possibility of being able to do it.

  In the present invention, by assigning a time slot that is more resistant to fading (high speed tolerance) to a wireless terminal with a fast moving speed, it is possible for the wireless terminal to receive an optimum signal even when moving at a higher speed The sex can be increased. Wireless terminals with a low moving speed and wireless terminals with a short distance to the base station are less affected by fading due to an increase in moving speed, so there is no problem even if they are assigned to time slots that are weaker to fading. When a fast wireless terminal is connected in the future, a slot strong against fading can be secured. In a system where it is inevitable to mix slots that are resistant to fading (that is, speed tolerance) and slots that are vulnerable to fading, the slots that are resistant to fading naturally have higher value than slots that are vulnerable to fading. Therefore, if the object is to be distinguished by usage or billing, a more detailed service can be provided.

  Next, as Embodiment 1, a detailed configuration and principle when the present invention is applied to a specific wireless communication system will be described. As an example of a wireless communication system to which the present invention is applied, consider a system as shown in FIG. The base station 200 has an antenna array composed of two antenna elements, and establishes a digital radio path with the radio terminal 300. As a channel model, it is assumed that a large number of scatterers are distributed between the base station 200 and the radio terminal 300 and a frequency non-selective multiple propagation path is formed. Since the wireless terminal 300 can move by carrying, the multiple propagation paths between the wireless terminal 300 and the base station 200 have different Doppler frequencies.

  FIG. 6 is a block diagram illustrating a radio unit configuration of the base station 200 according to the first embodiment. As shown in the figure, the base station 200 includes a reference clock generation unit 210, a weight controller 220, a baseband processor 230, a channel estimation unit 240, a moving speed calculation unit 250, analog-digital converters ADC1, ADC2, digital-analog converters DAC1, DAC2. With Based on the reference clock generated by the reference clock generation unit 210, the base station 200 generates reference frequency generation related to radio and timing related to the TDMA-TDD frame structure. The two antennas ANT1 and ANT2 constitute an adaptive array antenna unit AAA, and are both used for transmission and reception. Transmit / receive signals are distributed by circulators C1 and C2. Of course, since the TDMA-TDD method is used, transmission and reception are not performed simultaneously.

  During reception of the traffic channel, the desired wave and the interference wave are superimposed and received on the antennas ANT1 and ANT2 serving as the antenna elements. The weight controller 220 samples the signals received at the reception frequency and the set time slot set by each antenna element by the analog-digital converters ADC1 and ADC2, and then applies the matched filters MF1 and MF2 to obtain antenna array output data. The baseband processor 230 passes the training signal pattern that should be included in the desired wave to the channel estimation unit 240. The channel estimation unit 240 can perform channel estimation using the training signal pattern. Since the training signal is included in the head portion of the desired wave in the uplink, the channel estimation unit 240 uses this for channel estimation. The weighting factor of each antenna used for channel estimation by the channel estimation unit 240 is temporarily stored in a memory area (not shown) of the baseband processor 230. The stored antenna weighting factor is reused as the transmission antenna weighting factor during downlink transmission of the same channel.

  The moving speed calculation unit 250 is added to calculate the relative speed between the base station 200 and the wireless terminal 300 (the base station is stationary and becomes the absolute speed of the wireless terminal). Then, it needs to exist in either the base station or the wireless terminal. This part will be described in detail later. Since the radio terminal 300 does not use an antenna array, it has a simple configuration as shown below.

  FIG. 7 is a block diagram illustrating a configuration of a wireless unit of the wireless terminal 300 according to the first embodiment. As shown in the figure, the wireless terminal 300 includes a reference clock generation unit 310, a baseband processor 330, a moving speed calculation unit 350, analog-digital converters ADC3, ADC2, and a digital-analog converter DAC3. The wireless terminal 300 has only one antenna ANT3 and is used for both transmission and reception. Of course, since the TDMA-TDD method is used, transmission and reception are not performed simultaneously. At the time of reception, the downlink reception signal arriving at the antenna end is sent to the analog-digital converter ADC3 through the circulator C3 and sampled. The sampled interface (IF) signal is sent to the baseband processor 330, detected and demodulated, and processed as a data signal. Regarding transmission, data in the baseband processor 330 is modulated into a transmission interface (IF) signal, converted into an analog signal by the digital-analog converter DAC3, and then sent to the antenna ANT3 through the circulator C3 and emitted.

  Similar to the base station, the moving speed calculation unit 350 is added to calculate the relative speed between the base station and the wireless terminal, and in the present invention, it needs to exist in either the base station or the wireless terminal. This part will be described in detail later.

  At the time of transmission, the weight of each antenna is changed by multiplying the transmission data signal from the baseband processor 330 by the antenna weight coefficient used for channel estimation at the time of reception. The signal multiplied by the weight coefficient is converted into analog data by the DAC 3 and then guided to the antenna output by the circulator C3.

  Next, radio resources will be described. The TDMA-TDD frame has 5 msec as 1 frame and is multiplexed 3 times. The frequency channel is 625KHz wide, 8 frequency channels can be used and occupies 5MHz. 24 channels are formed by combining slots 1 to 3 with f0 to f7 in ascending order of frequency. Here, the combination of f0 and slot 0 is 0ch, and channel numbers are assigned as shown in Table 3. 0ch is reserved for the broadcast information channel. 4ch is reserved for a traffic channel establishment request. The base station manages 22 channel resources from 1ch to 3ch and 5ch to 23ch, monitors traffic channel establishment requests from wireless terminals in all 4ch, and allocates channel channel resources to traffic channels

  Table 4 shows the types of channel signals exchanged between the base station and the wireless terminal. The wireless terminal has a wireless terminal ID uniquely assigned by the system, and the wireless terminal ID is placed on the information symbols of all uplink channels. The base station manages the wireless terminal based on the wireless terminal ID. When the wireless terminal includes the wireless terminal ID in the downlink channel from the wireless base station, the wireless terminal determines whether the wireless terminal ID is addressed to the wireless terminal. To do. Further, the signal format used in the downlink channel is one type as shown in FIG.

  The broadcast information channel has a known training sequence pattern and a known information symbol, and transmits the broadcast information channel every other frame. The wireless terminal monitors f0, captures the received signal from the point where the energy increases sharply, recognizes that the signal having a high correlation with a known information symbol is a broadcast information channel, and stores its timing in a storage unit (not shown). Stored). After receiving the broadcast information channel, the reception slot position is adjusted, and synchronization with the base station is attempted. The base station and the wireless terminal determine that the frame transmitting the broadcast information channel is an even frame and the frame not transmitting the broadcast information channel is an odd frame.

  The wireless terminal 300 receives the broadcast information channel, adjusts the reception slot position, and then transmits the configuration request channel using the 0ch odd frame. The following shows the signal format used in the configuration request channel in the uplink.

  The configuration request channel in the uplink is a small signal for the uplink slot with a relatively large guard time added at the end. As a result, even if the wireless terminal 300 is far from the base station 200, the wireless terminal 300 is within the uplink reception slot of the base station. Therefore, the base station 200 can receive even if the radio terminal 300 does not advance the transmission timing of the uplink configuration request channel. When the base station 200 receives the configuration request channel, the base station 200 returns the information symbol with a delay time value from the original reception position, and returns the ID and the ID of the wireless terminal 300 that has transmitted the configuration request channel. Store the current time and delay value.

  When receiving a reply to the configuration request channel, the radio terminal 300 stores the delay time value from the original reception position included in the information symbol of the signal and the current time, and sets the delay time of the uplink transmission signal. In order to cancel, the transmission position of the transmission signal is advanced. With the above processing, the synchronization processing of the wireless terminal is completed with respect to the base station 200. However, since the reference clock of the wireless terminal 300 is asynchronous with the reference clock of the base station, it gradually shifts. Further, the reception slot position and the transmission slot position are shifted due to the movement. In order to avoid synchronization shift due to these two reasons, for example, the wireless terminal 300 transmits a configuration request channel to the base station 200 every 5 seconds and repeats the above processing.

  In the present invention, either the base station or the wireless terminal must include a relative speed calculation unit (information acquisition unit) that calculates the relative speed between the base station and the wireless terminal. In this embodiment, the moving speed calculation units 250 and 350 added to the base station 200 and the wireless terminal 300 calculate the moving speed based on the difference information.

  The base station 200 can obtain the distance from the base station of the wireless terminal from the “difference information” of the same wireless terminal, and performs control to record the differential information over the past several times. By examining the change, the “relative movement speed” between the wireless terminal and the base station can be obtained. Since the difference information is shared between the base station 200 and the wireless terminal 300, means for performing a relative speed acquisition operation can be provided on the wireless terminal 300 side. The start of the base station traffic channel starts when the wireless terminal 300 transmits a traffic channel start request channel signal. In the uplink direction, both the traffic channel start request signal and the traffic channel signal have the signal format shown in FIG.

  There are two types of training sequence patterns, T0 and T1, respectively. As the traffic channel start channel signal, T0 is fixedly used, and T1 is fixedly used for the traffic channel. The wireless terminal transmits the information symbol of the traffic channel start channel signal using the 4ch including the wireless terminal ID and the current speed value. When there is a free channel resource, the base station reserves a free channel resource for the wireless terminal having the ID, and transmits a traffic channel permission signal including the channel number of the wireless resource in the information symbol. When the base station transmits a traffic channel permission signal and the wireless terminal receives the signal, in the next frame, the traffic channel is opened using the radio resource of the channel number included in the traffic channel permission signal.

  Next, the TDMA-TDD frame will be described. FIG. 11A is an example of a TDMA-TDD frame. One frame is multiplexed three times and is divided into three slots for both uplink and downlink. In the uplink slot, one time distribution is 545 μsec, and three uplink slots are continuous. A guard time of 10 μsec between uplink and downlink is provided behind the uplink slot, and a group of downlink slots follows. In the downlink slot, one time distribution is 1090 μsec, which is twice the time distribution of the uplink slot. Similarly to the uplink slot, the downlink slot has a configuration in which three are continuous. The first uplink slot and the first downlink slot form a pair “slot pair” to form one bidirectional channel. The same goes for the second and third uplink / downlink slot pairs.

  Here, attention is paid to the time difference between each uplink and downlink slot. As shown in FIG. 11B, the first uplink / downlink slot pair “slot pair” is 1645 μsec. That is, the antenna coefficient used for channel estimation during uplink reception is used as a transmission antenna coefficient after 1645 μsec. As shown in FIG. 11C, it can be seen that the second uplink / downlink slot pair extends to 2190 μsec, and the third uplink as shown in FIG. 11D extends to 2735 μsec. Here, the movement distance in each period of 1645 μsec, 2190 μsec, and 2735 μsec at 60 Km / Hour, 120 Km / Hour, 180 Km / Hour, and 240 Km / Hour is shown in the following table.

  If the carrier frequency is 2 GHz, the second slot moves by one wavelength equivalent at 240 km / hour. In addition, since the third slot moves by a portion that greatly exceeds one wavelength, there is a very high possibility that the propagation path itself will change in an environment where multiple propagation paths are formed. On the other hand, since the first slot has not moved by about one wavelength yet, the quality of the propagation path characteristics cannot be denied, but the antenna weighting factor used for channel estimation at the time of uplink reception by the reception slot is used at the time of transmission. It can be said that the value is high.

  A method according to the flowchart shown in FIG. 12 will be described as an example of a method in which the baseband processor 230 of the base station 200 allocates the first to third slots according to the speed. This flowchart aims to assign a slot with high fading resistance to a wireless terminal moving at a high speed of 120 km / hour or higher.

  First, in step S10, it is confirmed whether or not the moving speed of the terminal is 120 km / hour or more. If it exceeds 120Km / Hour, the process proceeds to step S11, where it is confirmed whether or not there is an empty slot in the first slot. If there is an empty slot, one empty slot is randomly selected from the empty slots in the first slot. Select and assign to a traffic channel (step S12). If it is determined in step S11 that there is no empty slot in the group of the first slot, the process proceeds to step S13 to check whether there is an empty slot in the second slot. One empty slot is selected at random from the above and assigned to the traffic channel (step S14). If it is determined in step S13 that there is no empty slot in the group of the second slot, the process proceeds to step S15 to check whether there is an empty slot in the third slot. One empty slot is randomly selected from the slots and assigned to the traffic channel (step S16).

In this way, if the mobile speed of the terminal is 120Km / Hour or higher, the probability of the slot allocated to the traffic channel is
Control is performed so that the first slot> the second slot> the third slot. A mobile terminal at a speed of 120 Km / Hour or more is likely to be a train or a car that runs long distance, and is unlikely to remain in the area of the base station. Therefore, even if such a channel that is resistant to fading is preferentially assigned, there is no problem because it is less likely to be occupied for a long time.

  If it is determined in step S10 that the terminal speed is less than 120 Km / Hour, the process proceeds to step S17. If it is determined in step S17 that the moving speed of the terminal is 60 Km / Hour or more (that is, 60 Km / Hour). The above is less than 120 Km / Hour), randomly selecting an empty slot from the group of all slots and assigning it to the traffic channel (steps S18 and S19). The reason for this is that at moderate speeds, it is meaningful to assign slots that are resistant to fading, but it is difficult to estimate the movement method and purpose of the base station, and it may remain in the area of the base station for a long time. Cannot be denied. Therefore, the selection is made randomly from all the empty slots without giving any weight to the selection.

  If it is determined in step S17 that the moving speed of the terminal is less than 60 km / hour, the process proceeds to step S20 to check whether or not there is an empty space in the third slot. One empty slot is randomly selected from the empty slots and assigned to the traffic channel (step S21). If there is no empty slot in the third slot group, the process proceeds to step S22 to check whether there is an empty slot in the second slot. If there is an empty slot, one empty slot is randomly selected from the empty slots in the second slot. A slot is selected and assigned to a traffic channel (step S23). If there is no empty slot in the second slot group, the process proceeds to step S24 to check whether or not there is an empty first slot. If there is an empty slot, a random one is selected from the empty slots in the first slot. One empty slot is selected and assigned to the traffic channel (step S25).

In this way, if the mobile speed of the terminal is less than 60Km / Hour, the probability of the slot allocated to the traffic channel is
Control is performed so that the third slot> the second slot> the first slot. In mobile terminals with a speed of less than 60 km / hour, there is not much difference in channel estimation because the moving distance is small no matter which slot is used. However, since the moving distance is short, there is a high possibility that the user stays in the base station for a long time and continues to occupy the slot. By actively selecting a slot that is vulnerable to high-speed movement, the frequency of use of a slot that is resistant to high-speed movement is reduced, and the possibility that it can be assigned to a wireless terminal that has subsequently moved at high speed is increased. In any case, when traffic is congested, all wireless terminals can select all available channels.

  The radio resource selection algorithm can be implemented by either a radio terminal or a base station. Which one is adopted may be determined by the system, and control is simply performed by selecting the terminal moving speed value calculated by the base station itself, or selecting the terminal moving speed value included in the information symbol of the traffic channel request signal. It is only necessary to switch the control of whether or not. It may be difficult to add the contents of an information symbol if it follows a standard that is already in operation. In such a case, it is easier to adopt the moving speed value calculated by the base station. As another viewpoint, when implementing a measurement mechanism that can measure the relative speed by sequentially calculating the Doppler shift amount of the downlink broadcast information channel signal emitted by the base station to the wireless terminal, the information symbol of the traffic channel request signal It would be advantageous in terms of performance to use the included relative speed value. Note that the present invention is not limited to these implementations.

  The above has described the method of selecting and assigning slots having different fading tolerances (that is, different speed tolerances) on the basis of “movement speed”. However, changing the slot to be assigned based on the nature of the transmitted data and the nature of the application to be used may be convenient in providing the service. A recent wireless terminal may have both a voice transmission function and a data transmission function as an application. In the case of voice transmission, if channel transmission is not performed, there are many implementations in which retransmission is not performed, leading to a reduction in voice quality. However, in the case of data transmission, re-transmission is normally implemented by control such as ARQ (Auto Repeat reQuest). If such an implementation is selected, a slot that is vulnerable to fading is selected when a traffic channel is established for data communication purposes, and a slot that is resistant to fading is selected when a traffic channel is established for voice communication purposes. .

  FIG. 13 is a block diagram illustrating a configuration of a wireless terminal 300 that exclusively supports voice communication and data communication. As shown in the figure, the wireless terminal 300 further includes a voice codec 360 and a data communication upper layer 370. Whether the communication is voice communication or data communication is controlled so that the baseband processor 330 distinguishes whether the data generation source from the upper layer is the voice codec 360 or the data communication upper layer 370. . When a traffic channel establishment request channel is established, if the higher-level data generation source is the voice codec 360, the wireless terminal places information indicating a voice call in the communication type information element of the information symbol of the traffic channel establishment request channel. In addition, when the wireless terminal 300 establishes the traffic channel establishment request channel and the higher data generation source is the data communication upper layer 370, the information indicating the data call in the communication type information element of the information symbol of the traffic channel establishment request channel Put on. When the base station receives the traffic channel establishment request channel, the base station refers to the communication type information element of the information symbol of the traffic channel establishment request channel and determines the slot to be selected as shown in the flowchart of FIG.

  FIG. 14 is a flowchart showing a slot allocation method in which slots are selected and allocated based on whether or not voice communication is performed. Steps K10-K16 and K20-K25 in FIG. 14 are the same processes as steps S10-S16 and S20-S25 in FIG. Step K10 in FIG. 14 determines whether or not the voice communication is performed by the above method. If it is voice communication, the process proceeds to step K11, and if it is not voice communication, the process proceeds to step K20. The subsequent processing is the same. In this way, high-quality slots (slot pairs) with higher fading resistance and speed resistance are selected and assigned to applications using voice (such as VoIP).

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each unit, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. It is. For example, in the embodiment, the configuration in which the moving speed information is obtained from the difference information has been described. However, a configuration in which the moving speed information is obtained from the maximum Doppler frequency as described below may be used. For example, the information acquisition unit 120 in FIG. 1 is provided with a maximum Doppler frequency calculation unit and a movement speed calculation unit. A maximum Doppler frequency calculation unit (not shown) calculates a maximum Doppler frequency representing a relative movement state between devices by subtracting a known reference frequency from a frequency of a signal received from another wireless communication terminal. To do. In addition, a moving speed calculation unit (not shown) calculates a relative moving speed from the calculated maximum Doppler frequency using a predetermined calculation formula. Thus, it should be noted that the moving speed information can be obtained from other techniques and various elements, and such a configuration is also included in the scope of the present invention. Also, in the embodiment, based on the control information obtained from the uplink time slot signal received by the base station, the superposition coefficient (beamforming directivity) of the downlink time slot signal paired with this uplink time slot signal is adjusted. Thus, the configuration for transmitting the adjusted signal to the terminal is shown. However, the superposition coefficient is merely an example, for example, by changing the modulation method (ModClass), changing the transmission power, etc., and transmitting the adjusted signal to the terminal, the radio wave propagation path of the uplink time slot signal Communication quality may be improved by ensuring continuity between the characteristics and that of the downlink time slot signal.

1 is a block diagram of a wireless communication device according to an embodiment of the present invention. It is a figure which shows a frame structure. It is a figure which shows the rewritten frame structure. It is a figure which shows the timing in the antenna end of a radio | wireless terminal. It is a block diagram which shows an example of the radio | wireless communications system to which this invention is applied. FIG. 3 is a block diagram illustrating a configuration of a radio unit of a base station 200 according to the first embodiment. 3 is a block diagram illustrating a configuration of a radio unit of a radio terminal 300 according to the first embodiment. FIG. It is a figure which shows the signal format used with a downlink channel. It is a figure which shows the format of the signal used with the configuration request | requirement channel in an uplink. It is a figure which shows the signal format of the traffic channel start request signal in an uplink direction. It is a figure which shows an example of a TDMA-TDD frame. It is a flowchart which shows an example of the method of assigning a slot. It is a block diagram which shows the structure of the radio | wireless terminal 300 which supports audio | voice communication and data communication exclusively. It is a flowchart which shows the slot allocation method which selects and allocates a slot on the basis of whether it is audio | voice communication.

Explanation of symbols

100 wireless communication device 110 control unit 120 information acquisition unit (speed information acquisition unit)
130 slot allocation unit 140 communication unit 150 storage unit 200 base station 210 reference clock generation unit 220 weight controller 230 baseband processor 240 channel estimation unit 250 moving speed calculation unit AAA adaptive array antenna unit ADC1, ADC2, ADC3 analog / digital converter ANT, ANT1 , ANT2, ANT3 Antenna C1, C2, C3 Circulator DAC1, DAC2, DAC3 Digital analog converter MF1, MF2 Matched filter 300 Wireless terminal 310 Reference clock generator 330 Baseband processor 350 Moving speed calculator 360 Voice codec 370 Data communication upper layer

Claims (5)

Communication in a wireless communication device that uses a time division multiple access / time division duplex method having a plurality of time slots and controls a signal in a downstream time slot based on an upstream time slot signal in wireless communication with another device A method,
An acquisition step of acquiring information about a moving speed in the other device;
An allocation step of selecting and assigning the uplink time slot and the downlink time slot according to the acquired information of the other device;
A communication method. The communication method according to claim 1,
The assigning step comprises:
Select and assign the uplink time slot and the downlink time slot so that the time difference between the uplink time slot and the downlink time slot becomes shorter as the other device having a higher moving speed of the acquired information. ,
A communication method characterized by the above. The communication method according to claim 1 or 2,
There are a plurality of time slot pairs in which the time sequence of the upstream time slot is equal to the time sequence of the downstream time slot,
The assigning step comprises:
One time slot pair is selected from the plurality of time slot pairs so that the time difference between the upstream time slot and the downstream time slot becomes shorter as the other device having a higher moving speed of the acquired information. Assign
A communication method characterized by the above. The communication method according to any one of claims 1 to 3,
The time interval of the upstream time slot is different from the time interval of the downstream time slot,
A communication method characterized by the above. A wireless communication device that uses a time division multiple access / time division duplex method having a plurality of time slots in wireless communication with other devices and controls a signal in a downstream time slot based on an upstream time slot signal. And
An information acquisition unit that acquires information on a moving speed in the other device; and a slot allocation unit that selects and assigns the uplink time slot and the downlink time slot according to the acquired information of the other device;
A wireless communication device.

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