JP3979761B2 - Radio base station, radio base station communication method and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio base station such as an adaptive array system that spatially multiplexes and transmits a transmission signal to a mobile station with different directivity patterns, and a communication method performed by the radio base station with a mobile station.
[0002]
[Prior art]
In recent years, frequency resources have been saturated due to a rapid increase in users in mobile communications, and the spatial multiplexing method has attracted attention as a solution. Spatial multiplexing is a communication method that multiplexes transmission and reception signals of a plurality of mobile stations at the same frequency at the same time by forming different directivity patterns for the plurality of mobile stations using an adaptive array device. It is.
[0003]
In a radio base station equipped with an adaptive array device, the amplitude and phase of the received signal for each antenna are adjusted to separate the received signal for each mobile station from the multiplexed received signals from multiple mobile stations. A weighting coefficient for performing the calculation is calculated for each mobile station. As a method for calculating the weighting factor, a minimum mean square error (MMSE) method is used. That is, the weighting factor is calculated so that the sum of errors between the value obtained by multiplying the received signal for each antenna by the weighting factor for the antenna and the reference signal is minimized. Here, as the reference signal, a known signal, for example, PR (preamble) or UW (unique word) constituting a symbol string is used in PHS.
[0004]
For adaptive array systems and spatial multiplexing systems, see “Adaptive signal processing using array antennas” (by Nobuyoshi Kikuma, published by Science and Technology Publications) and “Path Division Multiple Access (PDMA) mobile communication systems” (RSG93- 84 (1994-01), pp 37-44), and detailed description thereof is omitted here.
By the way, if the reference signal has a different value for each mobile station wirelessly connected by spatial multiplexing, the weighting factor can be calculated and the signal can be separated without any problem. For example, in PHS, the above PR and UW are Since all mobile stations use a common one, the symbol sequence for each mobile station cannot be normally separated from the multiplexed received signal when the timing for receiving the symbol sequence is close Occurs. In order to avoid such a problem, the radio base station selects a set of mobile stations such that the reception timing difference between the symbol sequences is equal to or longer than a certain time, and performs spatial multiplexing on the selected set of mobile stations. To do.
[0005]
[Problems to be solved by the invention]
However, even if the reception timing difference is initially spatially multiplexed so that the reception timing difference is equal to or longer than a certain time, at least one mobile station in the set of multiplexed mobile stations moves, so that the mobile station Change occurs in the signal propagation environment between the mobile station and the radio base station. As a result, the reception timing of the symbol sequence from the mobile station may change in the radio base station, and the reception timing difference from the symbol sequence of another mobile station may be close to a certain time or less. In such a case, it becomes impossible to separate the symbol string for each mobile station, and the call cannot be made.
[0006]
Therefore, the present invention provides a radio base station and a radio that avoid a situation in which a call cannot be made when there is a possibility that a call cannot be made in the future because reception timings of symbol sequences from spatially multiplexed mobile stations are close. An object is to provide a communication method of a base station.
[0007]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention provides:A radio base station that receives signals transmitted from a plurality of desired mobile stations by spatially multiplexing with different directivity patterns and transmitting the transmission signals after a certain period of time after the mobile station receives the transmission signals. A timing specifying unit for specifying a reception timing of a symbol string in a signal transmitted from the mobile station, and a unit for searching for two mobile stations such that a difference between the specified reception timings is less than a first time. And a symbol sequence transmitted to at least one of the two mobile stations so that a difference in reception timing of the symbol sequences from the two searched mobile stations changes to a first time or more. And a timing adjusting means for adjusting the transmission timing.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present embodiment, when the timing for receiving a symbol string from a mobile station is close to less than a predetermined time, the timing of the symbol string transmitted to these mobile stations is adjusted so that the timing becomes equal to or longer than the predetermined time. The present invention relates to a radio base station having a function to perform.
[0010]
Hereinafter, the present embodiment will be described with reference to the drawings.
(Configuration of radio base station)
FIG. 1 is a block diagram showing a configuration of a main part of a radio base station in the embodiment of the present invention.
The radio base station includes radio units 11, 21, 31, 41, antennas 10, 20, 30, 40, a modem unit 60, a control unit 80, a baseband unit 70, and a signal processing unit 50. .
(Radio unit 11)
The radio unit 11 includes a transmission unit 12 and a reception unit 13. The transmission unit 12 modulates the baseband signal (symbol string) input from the signal processing unit 50 to an intermediate frequency signal (hereinafter abbreviated as IF signal), and the IF signal is a high frequency signal (hereinafter abbreviated as RF signal). And is amplified to a transmission output level and output to the antenna 10. The receiving unit 13 converts the received signal from the antenna 10 into an IF signal and demodulates it into a baseband signal (symbol sequence).
[0011]
Since the radio units 21, 31, and 41 have the same configuration as the radio unit 11, the description thereof is omitted.
(Modem unit 60)
The modem unit 60 converts and demodulates the baseband signal by a π / 4 shift QPSK (Quadrature Phase Shift Keying) method.
(Control unit 80)
The control unit 80 is specifically composed of a CPU and a memory, and controls the entire radio base station, particularly when receiving a call from a mobile station via a control channel and receiving a call from the network. Assign a communication channel to the mobile station. FIG. 2 shows an example of the allocation management table. In the assignment management table of FIG. 6, the horizontal direction indicates time division communication channels, and the vertical direction indicates path division multiplexing. PS-A to PS-D in the column indicate assigned mobile stations. In the figure. PS-A, PS-C, and PS-D are time-division multiplexed, and PS-A and PS-B are spatially multiplexed.
(Baseband part 70)
The baseband unit 70 is connected to a network (public network or private network) not shown in the figure, and performs baseband signal connection with the telephone network 90.
[0012]
The baseband unit 70 performs time division multiplexing processing. FIG. 3 is an explanatory diagram of a TDMA / TDD frame for performing time division multiplexing. Here, a TDMA / TDD frame of a so-called PHS telephone system is shown. In the figure, T0 to T3 are transmission time slots, and R0 to R3 are reception time slots. The control channel (CCH in the figure) is composed of a pair of transmission time slots and reception time slots (T0, R0). In addition, the communication channels TCH1, TCH2, and TCH3 are respectively configured by pairs of (T1, R1), (T2, R2), and (T3, R3). The communication channels TCH1, TCH2, and TCH3 are distinguished by time division, but each communication channel is further formed with a plurality of communication channels by spatial multiplexing.
(Signal processing unit 50)
The signal processing unit 50 is configured around a programmable digital signal processor, and includes a signal adjustment unit 51, a clock generation unit 52, a transmission timing adjustment unit 53, and a reception timing specification unit 54.
[0013]
The clock generation unit 52 generates a unique clock for each mobile station (user) to be spatially multiplexed, and sends each clock to the signal adjustment unit 51. In the present embodiment, the number of users to be spatially multiplexed is set to two for simplification of explanation, so the clock generation unit 52 generates a clock TA for user A and a clock TB for user B. When receiving the notification of the transmission timing from the transmission timing control unit 53, the clock generation unit 52 adjusts the clock generation timing so as to coincide with the notified transmission timing. At this time, the clock generation unit 52 is notified from the current clock generation timing instead of changing the clock generation timing at the same time so as to coincide with the notified transmission timing in the transmission time slot of the next time. The generation timing is changed by a fixed amount Δtc for each transmission time slot until the transmission timing is reached. This is because the mobile station may not be able to receive the symbol sequence well if the transmission timing of the symbol sequence from the radio base station changes suddenly, and the consistency with the PHS standard is taken into consideration.
[0014]
The signal adjustment unit 51 generates a symbol sequence for each user from the symbol sequences input from the radio units 11, 21, 31, 41 and outputs the symbol sequence to the modem unit 60. A symbol sequence for each of the radio units 11, 21, 31, and 41 is generated from the sequence and output to the radio units 11, 21, 31, and 41. FIG. 4 is a diagram illustrating a configuration of the signal adjustment unit 51. As shown in the figure, the signal adjustment unit 51 includes user processing units 51a and 51b for each user to be spatially multiplexed. X1 to X4 and S1 to S4 in the figure indicate signal lines and terminals, but for convenience of explanation, symbol column names to which the signal lines and terminals are input and output are also indicated. X1 to X4 indicate symbol sequences sent from the radio units 11, 21, 31, and 41 to the signal adjustment unit 51, and S1 to S4 denote symbols sent from the signal adjustment unit 51 to the radio units 11, 21, 31, and 41. Indicates a column.
[0015]
The user processing unit 51a receives input of the symbol strings X1 to X4 from the radio units 11, 21, 31, and 41. The user processing unit 51a generates the symbol sequence Ua of the user A from these symbol sequences and outputs it to the modem unit 60.
In addition, the user processing unit 51 a receives an input of the symbol string Ua of the user A from the modem unit 60. The user processing unit 51a generates symbol sequences Sa1 to Sa4 for the radio units 11, 21, 31, and 41 from this symbol sequence, and outputs each symbol sequence to each radio unit. Similarly, the other user processing unit 51b outputs the symbol strings Sb1 to Sb4 to each radio unit. As a result, a symbol sequence S1 (= Sa1 + Sb1) obtained by adding the symbol sequences Sa1 and Sb1 from each user processing unit is sent to the wireless unit 11.
[0016]
Next, details of processing by the user processing unit will be described. FIG. 5 is a diagram illustrating a configuration of the user processing unit 51a.
The weight calculation unit 55 uses the PR (preamble) and UW (unique word) symbols, which are known parts in the symbol sequence, in the first few reception time slots after starting communication with the mobile station. Calculate the weight. That is, the weight calculation unit 55 uses E = D− (Wa1) using the symbol sequences X1 to X4 sent from the radio units 11, 21, 31, and 41 and the fixed symbol sequence D sent from the reference signal generation unit 506. Weights Wa1 to Wa4 are calculated so as to minimize (X1 + Wa2 × X2 + Wa3 × X3 + Wa4 × X4). The weights Wa1 to Wa4 once calculated in this way are used as initial values in the subsequent reception of the symbol string in the reception time slot and in the transmission time slot which is a pair of the reception time slot.
[0017]
The weight calculation unit 55 outputs the weights Wa1 to Wa4 calculated as described above when receiving the symbol sequence, and the multiplier 521 to 524 and the adder 504 output the symbol sequence Ua (= Wa1) to the user A. * X1 + Wa2 * X2 + Wa3 * X3 + Wa4 * X4) is generated. The generated symbol string Ua for user A is sent to the modem unit 60.
[0018]
Further, when transmitting a symbol string, the symbol string Ua for the user A sent from the modem unit 60 is temporarily stored in the buffer 507. The buffer 507 outputs the symbol sequence Ua according to the clock TA generated by the clock generation unit 52. The weight calculation unit 53 outputs the weights Wa1 to Wa4 calculated as described above according to the clock TA. Each of the multipliers 581 to 584 multiplies the symbol sequence Ua and the weights Wa1 to Wa4, and the symbol sequences Sa1 (= Wa1 × Ua), Sa2 (= Wa2 × Ua), and Sa3 (= Wa3 ×) as multiplication results. Ua) and Sa4 (= Wa4 × Ua) are output to the radio units 11, 21, 31, and 41.
[0019]
Similarly, the weight calculation unit of the user processing unit 51b calculates the weight and outputs the weight when transmitting / receiving the symbol, and the buffer of the user processing unit 51b outputs the symbol string Ub to the user B according to the clock TB. Here, when the clock generation unit 52 generates the clock TB with a delay of ΔtS from the clock TA, the symbol strings Sb1 to Sb4 output from the user processing unit 51b are Sa1 to S1 output from the user processing unit 51a. It is delayed by ΔtS from Sa4.
[0020]
In this way, by changing the transmission timing of the symbol string transmitted to the user (mobile station) in the radio base station, the reception time of the symbol string changes in the mobile station, and the radio base station after a certain time has elapsed from the reception time. Since it is transmitted to the station as a symbol string, the radio base station can change the reception timing of the symbol string from the mobile station.
(Reception timing specifying unit 54)
The reception timing specifying unit 54 specifies the relative time at which the first symbol point constituting the symbol sequence is received as the reception timing of the symbol sequence based on the start time of the reception time slot for receiving the symbol sequence.
[0021]
FIG. 6A shows an example of the transmission timing of the symbol string to the users A and B. As shown in the figure, it is assumed that the radio base station transmits the symbol sequence for user A and the symbol sequence for user B at the same timing in the T1 slot in the T1 slot. That is, if the symbol string transmission timing to the user A is tSa and the symbol string transmission timing tSb to the user B is tSA = tSb.
[0022]
FIG. 6B shows an example of the reception timing of symbol strings from the users A and B. As shown in the figure, the radio base station receives different reception timings tRa for the symbol string from the user A and the symbol string from the user B in the R1 slot which is a pair of the T1 slot shown in FIG. Receiving at tRb. This is because the transmission time of the symbol sequence between the radio base station and the mobile station differs for each mobile station. In this way, the symbol strings can be separated by the reception timing of the symbol strings from the spatially multiplexed mobile stations being separated by a certain time or more.
(Sending timing adjustment unit 53)
The transmission timing adjustment unit 53 calculates a reception timing difference ΔtR (= | tRb−tRa |) from the reception timings tRa and tRb of the symbol string from each user specified by the reception timing specification unit 54.
[0023]
If the calculated reception timing difference ΔtR is equal to or greater than the threshold value Δtmin, the transmission timing adjustment unit 53 does not perform adjustment because the symbol strings can be separated even if the symbol strings are transmitted at the same timing as before. Here, the threshold value is a value obtained by adding a margin to a minimum time difference at which a symbol string for each mobile station can be separated. When the reception timing difference is less than the threshold, there is a risk that separation will not be possible if the reception timing difference is further reduced thereafter.
[0024]
On the other hand, if ΔtR is less than the threshold value Δtmin, there is a risk that the symbol sequence for each user cannot be separated if ΔtR becomes small due to the movement of the user. To make the reception timing difference widen. That is, ΔtS (= Δtmin−ΔtR), which is the difference between Δtmin and ΔtR, is calculated, and the transmission timing of the symbol string to the user A or the user B is changed by Δts. Then, the transmission timing adjustment unit 53 calculates the time difference tEa, tEb between the reception time of the last symbol of each user's symbol string and the end time of the reception slot. Then, the transmission timing adjustment unit 53 calculates the transmission timing of the symbol string on the basis of the following (A1) to (A4). Here, tSa ′ and tSb ′ indicate the transmission timings after changing the symbol strings to the user A and the user B, respectively.
(A1) If tRa ≧ ΔtS and tEb <ΔtS (shown in FIG. 7A), tSa ′ = tSa−ΔtS and tSb ′ = tSb (shown in FIG. 7B).
[0025]
In other words, when the longest time tRa that can be earlier in the earlier reception timing is ΔtS or more and the longest time tEb that can be further delayed in the later reception timing is less than ΔtS, the earlier reception timing The transmission timing of the symbol string to the user is advanced by ΔtS.
(A2) If tRa <ΔtS and tEb ≧ ΔtS (shown in FIG. 8A), then tSa ′ = tSa and tSb ′ = tsb + ΔtS (shown in FIG. 8B).
[0026]
That is, when the longest time tRa that can be advanced earlier in the earlier reception timing is less than ΔtS and the longest time tEb that can be further delayed in the later received timing is greater than or equal to ΔtS, The transmission timing of the symbol string to the user is delayed by ΔtS.
(A3) If tRa ≧ ΔtS, tEb ≧ ΔtS, and tRa ≧ tEb (shown in FIG. 9A), tSa ′ = tSa−ΔtS and tSb ′ = tSb (shown in FIG. 9B). ).
[0027]
That is, the longest time tRa that can be made earlier with the earlier reception timing is ΔtS or more, the longest time tEb that can be made later with the later reception timing is more than ΔtS, and tRa is more than tEb. Sometimes, the transmission timing of the symbol string to the user whose reception timing is earlier is advanced by ΔtS.
(A4) If tRa ≧ ΔtS, tEb ≧ ΔtS, and tRa <tEb (shown in FIG. 10A), then tSa ′ = tSa and tSb ′ = tSb + ΔtS (shown in FIG. 10B).
[0028]
That is, the longest time tRa that can be made earlier with the earlier reception timing is ΔtS or more, and the longest time tEb that can be made later with the later reception timing is more than ΔtS, and tRa is less than tEb. Sometimes, the transmission timing of the symbol string to the user whose reception timing is later is delayed by ΔtS.
[0029]
When the transmission timing is changed as described above, the transmission timing adjustment unit 53 notifies the clock reproduction unit 52 of the changed transmission timing.
Next, how the reception timing finally changes when the transmission timing is changed according to the above-described standard will be described.
FIG. 7C shows the reception timing of the symbol strings from the user A and the user B in the corresponding reception slot after the symbol strings are transmitted to the user A and the user B at the transmission timing shown in FIG. Show. As shown in the figure, the symbol string reception timing tRa 'from the user A is also advanced by Δts because the symbol string transmission timing to the user A is advanced by Δts. That is, tRa ′ = tRa−Δts = tRa− (Δtmin−ΔtR) = tRb−Δtmin, and the difference ΔtR ′ between the reception timing of the user A symbol sequence and the reception timing of the user B symbol sequence is Δtmin. It is possible to safely separate the symbol sequence from the user B symbol sequence.
[0030]
FIG. 8C shows the reception timing of the symbol sequences from the user A and the user B in the corresponding reception slot after the symbol sequences are transmitted to the user A and the user B at the transmission timing shown in FIG. Show. As shown in the drawing, the symbol string reception timing tRb 'from the user B is also delayed by Δts by delaying the transmission timing of the symbol string to the user B by Δts. That is, tRb ′ = tRb + Δts = tRb + (Δtmin−ΔtR) = tRa + Δtmin, and the difference ΔtR ′ between the reception timing of the user A symbol sequence and the reception timing of the user B symbol sequence is Δtmin, and the user A symbol sequence and the user B Can be safely separated from the symbol string.
[0031]
FIG. 9C shows the reception timings of the symbol sequences from the user A and the user B in the corresponding reception slots after the symbol sequences are transmitted to the user A and the user B at the transmission timing shown in FIG. 9B. Show. As shown in the figure, the symbol string reception timing tRa ′ from the user A is also advanced by Δts because the symbol string transmission timing to the user A is advanced by Δts. That is, tRa ′ = tRa−Δts = tRa− (Δtmin−ΔtR) = tRb−Δtmin, and the difference ΔtR ′ between the reception timing of the user A symbol sequence and the reception timing of the user B symbol sequence is Δtmin. It is possible to safely separate the symbol sequence from the user B symbol sequence.
[0032]
FIG. 10C shows the reception timing of the symbol sequences from the user A and the user B in the corresponding reception slot after the symbol sequences are transmitted to the user A and the user B at the transmission timing shown in FIG. Show. As shown in the drawing, the symbol string reception timing tRb 'from the user B is also delayed by Δts by delaying the transmission timing of the symbol string to the user B by Δts. That is, tRb ′ = tRb + Δts = tRb + (Δtmin−ΔtR) = tRa + Δtmin, and the difference ΔtR ′ between the reception timing of the user A symbol sequence and the reception timing of the user B symbol sequence is Δtmin, and the user A symbol sequence and the user B Can be safely separated from the symbol string.
<Sending timing adjustment operation>
An operation of symbol string transmission timing control in the radio base station according to the present embodiment will be described. FIG. 11 is a flowchart showing an operation procedure of symbol sequence transmission timing control.
[0033]
First, the user processing units 51 a and 51 b of the signal adjustment unit 51 generate a user A symbol sequence and a user B symbol sequence, respectively, based on the symbol sequences from the radio units 11, 21, 31, and 41 (steps). S1000).
The reception timing specifying unit 54 specifies the reception timing tRa of the user A symbol sequence and the reception timing tRb of the user B symbol sequence (step S1002).
[0034]
Next, the transmission timing adjustment unit 53 calculates a reception timing difference ΔtR = | tRb−tRa |, and compares ΔtR with Δtmin. If ΔtR is equal to or greater than Δtmin, the transmission timing adjustment unit 53 does not need to change the transmission timing, and thus does not adjust the timing (step S1003).
On the other hand, if ΔtR is less than Δtmin, the transmission timing adjustment unit 53 calculates the transmission timing according to the above-mentioned criteria (A1) to (A4) so that the reception timing difference ΔtR changes to Δtmin or more, and sets the transmission timing. The clock generation unit 52 is notified (steps S1003 and S1004).
[0035]
When the clock generation unit 52 receives a notification of a new transmission timing from the transmission timing adjustment unit 53, the clock generation unit 52 sequentially shifts by Δtc for each transmission time slot from the current clock generation timing until the notified transmission timing is reached. Then, the signal adjustment unit 51 sends the symbol strings to the user A and the user B according to the clock generated by the clock generation unit 52 (steps S1005 and S1006).
[0036]
When the reception timing difference ΔtR is equal to or greater than Δtmin, or after it coincides with the transmission timing notified of the clock, the clock generation unit 52 continues to generate the clock at the same timing as the previous time without changing the clock generation timing. The signal adjustment unit 51 sends out symbol strings to the user A and the user B according to the clock generated by the clock generation unit 52 (step S1007).
<Summary>
As described above, the radio base station according to the present embodiment widens the difference in reception timing by changing the transmission timing of the symbol sequence to the user when the reception timing of the symbol sequence from the user is close. Therefore, when there is a possibility that the symbol string from the user cannot be separated and the call cannot be made in the near future, it becomes possible to cope in advance so as not to make the call impossible.
<Modification>
In addition, this invention is not limited to said embodiment, Of course, the following modifications are also assumed naturally.
(1) About change of sending timing
In this embodiment, the transmission timing of the symbol string to one mobile station (user) is changed. However, the present invention is not limited to this, and the transmission timing of the symbol string to two mobile stations is changed. It may be changed. For example, within the range of the transmission time slot, the transmission timing of the symbol string to the mobile station with the earlier reception timing is advanced by α, and the transmission timing of the symbol string to the mobile station with the later reception timing is (Δts− It may be delayed by α).
(2) Change in sending timing
In the present embodiment, Δts (= Δtmin−ΔtR) is calculated and the transmission timing is adjusted so that the reception timing difference changes to Δtmin when the reception timing difference ΔtR is less than the threshold value Δtmin. However, the present invention is limited to this. Instead, the transmission timing may be adjusted by calculating Δts (= Δtmin−ΔtR + α) so that the reception timing difference ΔtR is somewhat larger than Δtmin. As a result, even if the reception timing is changed, even if the reception timing is likely to approach again due to continued movement of the user, the process of readjusting the transmission timing can be omitted.
(3) Other methods of changing reception timing
In the present embodiment, the radio base station uses the property of transmitting a symbol string to the radio base station after a certain time has elapsed from the timing at which the mobile station received the symbol string from the radio base station. However, the present invention is not limited to this, although the reception timing of the symbol sequence from the mobile station is changed by changing the transmission timing of the symbol sequence. For example, a signal instructing the timing for transmitting a symbol string may be sent from a radio base station to a mobile station.
(4) Reception timing
In the present embodiment, the time from the start time of the reception time slot to the time when the head of the symbol string is received is specified as the reception timing, but the present invention is not limited to this. For example, the relative time until the reception of a specific symbol point in the UW (unique word) from the start time of the reception time slot or the relative time until the reception of another symbol point is specified as the reception timing. Also good.
(5) Transmission / reception that exceeds the time slot limit
In the present embodiment, as long as the condition that the transmission symbol sequence can be transmitted in the currently used transmission time slot and the symbol sequence from the mobile station can be received in the currently used reception time slot is satisfied. Although the transmission timing is adjusted, the present invention is not limited to this. If there is no time for transmission / reception of symbol sequences, the transmission timing may be adjusted so that symbol sequences are transmitted / received across adjacent time slots. In addition, if a signal adjustment unit is provided with a function that can be separated even when user symbol sequences transmitted and received in separate time slots overlap, transmission that overlaps with symbol sequences of adjacent time slots. It may be timing adjustment.
[0039]
【The invention's effect】
  The radio base station of the present invention isA radio base station that transmits signals transmitted to a plurality of mobile stations in a spatially multiplexed manner with different directivity patterns and receives a signal transmitted by the mobile station after a certain period of time after the transmission signal is received by the mobile station. A timing specifying means for specifying a reception timing of a symbol string in a signal transmitted from the mobile station, a means for searching for two mobile stations such that a difference between the specified reception timings is less than a first time, Transmission of a transmission symbol string to at least one of the two mobile stations so that the difference in the reception timing of the symbol string from the two mobile stations searched changes to a first time or more. And a timing adjusting means for adjusting the timing.
[0040]
As a result, when there is a possibility that the difference in the reception timing of the symbol sequence from the spatially multiplexed mobile station cannot be separated close to less than the first time and the call cannot be made, the symbol sequence to the mobile station By adjusting the transmission timing, the difference in the reception timing of the symbol sequence from the mobile station is changed to the first time or more, so that it becomes impossible to separate the symbol sequence for each mobile station and to disable the call. be able to.
[0041]
Here, the timing adjustment means includes means for calculating a difference time between the first time and a reception timing difference, and is a symbol transmitted to the mobile station with the earlier reception timing of the two mobile stations. The total time of the time to advance the transmission timing of the column and the time to delay the transmission timing of the transmission symbol sequence to the mobile station with the later reception timing of the two mobile stations is equal to or greater than the difference time. The transmission timing may be adjusted.
[0042]
As a result, the difference time between the first time and the reception timing difference is calculated, and the transmission timing of the symbol string to the mobile station is changed by a time equal to or longer than the difference time, so the reception timing of the symbol string from the mobile station The difference can be increased by more than the difference time to the first time or more.
Here, the radio base station includes means for transmitting and receiving in time-divided time slots, and the timing specifying means uses the relative time from the start of the reception time slot to the reception of the beginning of the symbol string as the reception timing. The timing adjusting means includes means for calculating a difference time between the first time and a reception timing difference, and the earlier reception timing of the two mobile stations is the difference time. In the above case, the transmission timing can be adjusted by increasing the transmission timing of the transmission symbol string to the mobile station with the earlier reception timing by at least the difference time.
[0043]
As a result, when the time at which the head of the symbol sequence from the mobile station with the earlier reception time is received and the start time of the reception time slot are more than the difference time apart, the mobile station with the earlier reception time is sent to By making the symbol sequence transmission timing earlier than the difference time, the reception timing of the symbol sequence from the mobile station is earlier than the difference time, and the difference in reception timing from the two mobile stations is set to the first time or more. be able to.
[0044]
Here, the radio base station includes means for transmitting and receiving in time-divided time slots, and the timing specifying means uses the relative time from the start of the reception time slot to the reception of the end of the symbol string as the reception timing. The timing adjustment means calculates the time from the reception timing of the mobile station with the later reception timing of the two mobile stations to the end of the reception slot as a remaining time; Means for calculating a difference time between the time of 1 and the reception timing difference, and when the remaining time is equal to or longer than the difference time, at least a difference is made between the transmission timings of the transmission symbol strings to the mobile station having the later reception timing. The transmission timing can be adjusted with a delay of time.
[0045]
As a result, when the time of receiving the end of the symbol string from the mobile station whose reception time is later and the end time of the reception time slot are more than the difference time, the mobile station whose reception time is later By delaying the transmission timing of the symbol sequence for the difference time or more, the reception timing of the symbol sequence from the mobile station is delayed for the difference time or more, and the reception timing difference from the two mobile stations is set to the first time or more. be able to.
[0046]
Here, the radio base station includes means for transmitting and receiving in time-divided time slots, and the timing specifying means uses the relative time from the start of the reception time slot to the reception of the beginning of the symbol string as the reception timing. The timing adjustment means specifies the time from the end of the symbol string from the mobile station with the later reception timing of the two mobile stations to the end of the reception slot as the remaining time. Means for calculating, and means for calculating a difference time between the first time and the reception timing difference, and when the reception timing is equal to or greater than the difference time and equal to or greater than the remaining time, the reception timing that is earlier The transmission timing of the transmission symbol sequence to the mobile station is advanced at least by the difference time, the remaining time is greater than or equal to the difference time, and the reception time is increased. When the above timing may be characterized by adjusting at least difference output timing and delayed by time period the transmission timing of the transmission symbol sequence of the reception timing slower mobile stations.
[0047]
As a result, the free time space from the start time of the reception time slot to the time of receiving the beginning of the symbol string from the mobile station whose reception time is earlier, and the symbol from the mobile station whose reception time is later Compare the free time space from the time of receiving the end of the column to the end time of the reception time slot, and use the longer time space of the free time space, so the transmission timing difference for a longer time, Therefore, a reception timing difference can be ensured and symbols can be easily separated.
[0048]
Here, the timing adjusting means may change the transmission timing by a certain amount sequentially for each transmission time slot until the adjusted transmission timing is reached.
As a result, since the radio base station changes the symbol sequence transmission timing little by little, it is possible to avoid a situation in which the mobile station cannot follow a sudden change in the symbol sequence reception timing.
[0049]
In addition, the present invention provides a transmission signal to a plurality of mobile stations that is spatially multiplexed with different directivity patterns and transmitted, and receives a signal transmitted by the mobile station after a certain period of time after the transmission signal is received by the mobile station. A method of identifying a reception timing of a symbol string in a signal transmitted from a mobile station, and two mobile units whose difference between the identified reception timings is less than a first time At least one of the two mobile stations so that the difference between the step of searching for the station and the reception timing of the symbol string from the searched two mobile stations changes over a first time. Adjusting the transmission timing of the transmission symbol string.
[0050]
As a result, when there is a possibility that the difference in the reception timing of the symbol sequence from the spatially multiplexed mobile station cannot be separated close to the first time and the call cannot be made, the symbol sequence to the mobile station By adjusting the transmission timing, the difference in the reception timing of the symbol sequence from the mobile station is set to the first time or more, so that it becomes impossible to separate the symbol sequence for each mobile station and to disable the call. be able to.
[0051]
In addition, the present invention provides a transmission signal to a plurality of mobile stations that is spatially multiplexed with different directivity patterns and transmitted, and receives a signal transmitted by the mobile station after a certain period of time after the transmission signal is received by the mobile station. A computer-readable recording medium recording a program for controlling a radio base station, wherein a step of specifying a reception timing of a symbol string in a signal transmitted from a mobile station and a difference between the specified reception timing are the first The step of searching for two mobile stations such that the time is less than the time, and the difference between the received timings of the symbol sequences from the two mobile stations searched for are changed to the first time or more. A program for causing a computer to execute a step of adjusting a transmission timing of a transmission symbol string to at least one of the mobile stations is recorded.
[0052]
As a result, when there is a possibility that the difference in the reception timing of the symbol sequence from the spatially multiplexed mobile station cannot be separated close to less than the first time and the call cannot be made. By adjusting the transmission timing, the difference in the reception timing of the symbol sequence from the mobile station is set to the first time or more, so that it becomes impossible to separate the symbol sequence for each mobile station and to disable the call. be able to.
[0053]
As described above, according to the present invention, the problem of being unable to make a call, which has been a major obstacle to the spread of communication systems using spatial multiplexing, is solved, and its practical effect is extremely large.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a main part of a radio base station in an embodiment of the present invention.
FIG. 2 shows an example of an allocation management table.
FIG. 3 is an explanatory diagram of a TDMA / TDD frame for performing time division multiplexing.
4 is a diagram showing a configuration of a signal adjustment unit 51. FIG.
FIG. 5 is a diagram illustrating a configuration of a user processing unit 51a.
FIG. 6A shows an example of the transmission timing of a symbol string to users A and B.
FIG. 6B shows an example of the reception timing of symbol strings from the users A and B.
FIG. 7A shows an example of the reception timing of symbol strings from users A and B. FIG. 7B shows an example of the adjusted transmission timing of the symbol string to the users A and B.
FIG. 7C shows an example of symbol string reception timing from the users A and B after the transmission timing adjustment.
FIG. 8A shows an example of the reception timing of symbol strings from users A and B. FIG. FIG. 8B shows an example of the adjusted transmission timing of the symbol string to the users A and B.
FIG. 8C shows an example of symbol string reception timing from the users A and B after transmission timing adjustment.
FIG. 9A shows an example of the reception timing of symbol strings from users A and B. FIG. FIG. 9B shows an example of the adjusted transmission timing of the symbol string to the users A and B.
FIG. 9C shows an example of the reception timing of the symbol strings from the users A and B after the transmission timing adjustment.
FIG. 10A shows an example of symbol string reception timing from users A and B. FIG.
FIG. 10B shows an example of the adjusted transmission timing of the symbol string to the users A and B.
FIG. 10C shows an example of the reception timing of the symbol string from the users A and B after the transmission timing adjustment.
FIG. 11 is a flowchart showing an operation procedure of symbol string transmission timing control;
[Explanation of symbols]
10, 20, 30, 40 Antenna
11, 21, 31, 41 Radio unit
12 Transmitter
13 Receiver
50 Signal processor
51 Signal adjustment unit
51a User processing unit
52 Clock generator
53 Sending timing adjustment unit
54 Reception timing specifying unit
60 Modem part
70 Baseband part
80 Control unit
90 telephone network

Claims (8)

A radio base station that receives signals transmitted from a plurality of desired mobile stations by spatially multiplexing with different directivity patterns and transmitting the transmission signals after a certain period of time after the mobile station receives the transmission signals. There,
Timing specifying means for specifying the reception timing of a symbol string in a signal sent from the mobile station;
Means for searching for two mobile stations such that the difference between the identified reception timings is less than the first time;
Transmission of a transmission symbol string to at least one of the two mobile stations so that the difference in the reception timing of the symbol string from the two mobile stations searched changes to a first time or more. Timing adjustment means for adjusting the timing;
A radio base station comprising: The timing adjusting means includes means for calculating a difference time between the first time and a reception timing difference, and sending a transmission symbol string to a mobile station with the earlier reception timing of the two mobile stations. The transmission timing is such that the total time of the time to advance the timing and the time to delay the transmission timing of the transmission symbol sequence to the mobile station with the later reception timing of the two mobile stations is equal to or greater than the difference time. Adjust
The radio base station according to claim 1. The radio base station includes means for transmitting and receiving in time-divided time slots,
The timing specifying means specifies a relative time from the start of the reception time slot to the reception of the beginning of the symbol string as a reception timing,
The timing adjusting means includes means for calculating a difference time between the first time and a reception timing difference, and when the reception timing with the earlier reception timing of the two mobile stations is equal to or greater than the difference time. The transmission timing is adjusted by increasing the transmission timing of the transmission symbol string to the mobile station with the earlier reception timing by at least the difference time.
The radio base station according to claim 1. The radio base station includes means for transmitting and receiving in time-divided time slots,
The timing specifying means specifies the relative time from the start of the reception time slot to the reception of the end of the symbol string as the reception timing,
The timing adjustment means calculates a time from a reception timing of a mobile station having a later reception timing of the two mobile stations to a termination of the reception slot as a remaining time, and the first time And a means for calculating a difference time between the reception timing difference, and when the remaining time is equal to or greater than the difference time, the transmission timing of the transmission symbol string to the mobile station having the later reception timing is at least the difference time. Adjust sending timing by delaying
The radio base station according to claim 1. The radio base station includes means for transmitting and receiving in time-divided time slots,
The timing specifying means specifies a relative time from the start of the reception time slot to the reception of the beginning of the symbol string as a reception timing,
The timing adjusting means is means for calculating, as a remaining time, a time from reception of the end of a symbol string from a mobile station having a later reception timing of the two mobile stations until the end of the reception slot. And a means for calculating a difference time between the first time and the reception timing difference, and when the reception timing is equal to or greater than the difference time and equal to or greater than the remaining time, the mobile station with the earlier reception timing When the transmission timing of the transmission symbol sequence is advanced at least by the difference time, and when the remaining time is not less than the difference time and not less than the reception timing, the transmission timing of the transmission symbol sequence to the mobile station with the later reception timing Adjust the sending timing by delaying at least by the difference time
The radio base station according to claim 1. The timing adjustment means sequentially changes the transmission timing by a predetermined amount for each transmission time slot until the adjusted transmission timing is reached.
The wireless base station according to claim 2, wherein the wireless base station is a wireless base station. A radio base station that receives a signal transmitted by a mobile station after a certain period of time after the mobile station receives the transmission signal by spatially multiplexing and transmitting transmission signals to a plurality of desired mobile stations. A communication method,
Identifying a reception timing of a symbol string in a signal sent from the mobile station;
Searching for two mobile stations such that the identified difference in reception timing is less than the first time; and
Transmission of a transmission symbol string to at least one of the two mobile stations so that the difference in the reception timing of the symbol string from the two mobile stations searched changes to a first time or more. Adjusting the timing and
A communication method for a radio base station, comprising: A radio base station for transmitting signals to a plurality of desired mobile stations by spatially multiplexing with different directivity patterns and receiving a signal transmitted by the mobile station after a certain period of time after the mobile station receives the transmission signal. A computer-readable recording medium recording a program to be controlled,
Identifying a reception timing of a symbol string in a signal sent from the mobile station;
Searching for two mobile stations such that the identified difference in reception timing is less than the first time; and
Transmission of a transmission symbol string to at least one of the two mobile stations so that the difference in the reception timing of the symbol string from the two mobile stations searched changes to a first time or more. Adjusting the timing and
The computer-readable recording medium which recorded the program which makes a computer perform.

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