JP2008252181A - Slot allocation method and base station device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply efficient slot coupling to a free time slot even when allocation and release of a time slot constituting a frame are repeated, and to improve transmission efficiency. <P>SOLUTION: A slot specifying unit 9b gives priority levels in order from time slots close to both ends of a frame among free slots in the frame. A channel allocation unit 9c allocates time slots to a terminal device from a time slot having the highest priority level according to the priority levels. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for allocating slots to terminal apparatuses, and more particularly to a slot allocation method suitable for slot connection and a base station apparatus using the same.

  A mobile communication system such as PHS (Personal Handyphone System) uses a 4-slot multiplexed TDMA-TDD (Time Division Multiple Access-Time Division Duplex) system as shown in FIG. Communication is performed with a base station apparatus (CS: Cell Station) by assigning a time slot as a unit of communication to a personal station.

In the conventional time slot allocation method, in order to facilitate control, uplink and downlink time slots are allocated to terminal devices in order from the beginning of the frame. (For example, Non-Patent Document 1)
ARIB STANDARD RCR STD-28-1 “Second Generation Cordless Telephone System Standards”, 4.1, (1/2 volumes)

  By the way, recent mobile communication systems require high-speed and large-capacity data transmission as compared to conventional voice communication, such as data communication. In PHS, multiple time slots are connected. Thus, a slot connection technique to be assigned to the same terminal device has been studied.

  However, in the conventional time slot allocation method, time slots are allocated to the terminal device in order from the beginning of the frame. Therefore, when the time slot that has finished communication with the terminal device is released, the time slot is not included in the frame. There was a case where it was not continuous with a time slot to which no other terminal device was assigned, that is, an empty time slot. For example, when the first time slot and the second time slot of the frame in FIG. 1 are allocated to the terminal device, even if communication with the terminal device to which the first time slot is allocated ends and is released, the first time slot is released. The slot is isolated from other free time slots. Although there are a total of three empty time slots, the first time slot, the third time slot, and the fourth time slot, in the frame, consecutive time slots are 2 of the third time slot and the fourth time slot. The slot connection can be applied only to these two time slots. For this reason, it has been difficult to apply efficient slot connection to empty time slots.

  The present invention has been made in view of such a situation, and provides a slot allocation method capable of applying efficient slot connection to empty time slots and improving transmission efficiency, and a base station apparatus using the same. The purpose is to provide.

  One embodiment of the present invention is an allocation method. The gist of this method is to construct a frame from a plurality of continuous time slots, assign priorities to the time slots near the end of the frame, and assign them to the terminal devices in that order.

  Here, the “time slot close to the frame end” includes a time slot located at a short time interval from the time slots at both ends of the frame.

  Another aspect of the present invention is a base station apparatus. The base station device includes a allocating unit that configures a frame from a plurality of continuous time slots, assigns the time slot to the terminal device, and a specifying unit that specifies a priority from the time slot near the frame end, and The gist of the allocating unit is that the time slots are allocated to the terminal devices in the specified order.

  In addition, it is preferable that the specifying unit increases a rank of a time slot adjacent to a time slot to which a terminal device is already assigned.

  A communication quality measuring unit configured to measure communication quality with the plurality of terminal devices, wherein the specifying unit is configured such that when there are a plurality of time slots having the same priority, the order of time slots with higher communication quality. It is desirable to increase the value.

  In addition, it is preferable that the allocation unit performs the allocation if the measured communication quality exceeds a threshold value related to communication quality.

  According to the present invention, even after allocation and release of time slots constituting a frame are repeated, it is possible to apply efficient slot connection to empty time slots and improve transmission efficiency.

  The outline will be described before the present invention is specifically described. The embodiment of the present invention is a base station apparatus that connects a plurality of terminal apparatuses by the TDMA-TDD system, as in the second generation cordless telephone system. In the second generation cordless telephone system, as shown in FIG. 1, a TDMA frame (hereinafter referred to as a TDMA frame) is composed of four time slots for uplink communication (terminal device to base station device) and four time slots for downlink communication (base station device to terminal device). Frame), and the frames are continuously arranged. In the present embodiment, uplink communication and downlink communication are symmetric, and therefore only the uplink communication will be described below for convenience of explanation.

  As shown in FIG. 2, the base station apparatus according to the embodiment of the present invention further applies SDMA (Space Division Multiple Access), and allocates a plurality of terminal apparatuses to one time slot. FIG. 2 shows the arrangement of time slots on the time axis in the direction of the horizontal axis, that is, the arrangement of radio channels, and the arrangement of radio channels on the spatial axis in the direction of the vertical axis. That is, multiplexing on the horizontal axis corresponds to TDMA, and multiplexing on the vertical axis corresponds to SDMA. FIG. 2 includes the first to fourth time slots in one frame. In FIG. 2, the terminal device A is on one radio channel of the first time slot, the terminal device B and the terminal device D are on two radio channels of the second time slot, and the terminal device C is on one radio channel of the third time slot. Is assigned. In the following, for convenience of explanation, it will be assumed that one time slot is limited to one space and one radio channel is included in one time slot, and one terminal apparatus is assigned to one time slot. .

  FIG. 3 is a conceptual diagram showing the structure of the time slot. Time slot includes transient response response ramp time R, start symbol SS, preamble PR, synchronization word UW, modulation parameter MI, header in which communication control symbol consisting of channel type CI is arranged, payload in which data symbol is arranged, error It comprises a detection code CRC and a guard symbol G that prevents interference between adjacent time slots.

  When the required communication capacity is small as in voice communication, one time slot is assigned to one terminal device for each frame. On the other hand, when the required communication capacity is large as in data communication, two or more time slots may be linked for each frame and assigned to one terminal device.

  When two time slots are concatenated for each frame, a communication control symbol is arranged only in the first time slot to form a frame, which is allocated to a terminal device. As a result, the payload can be expanded, so that the transmission capacity per frame can be increased.

  At this time, if time slots are allocated to the terminal device in order from the beginning of the frame, when the time slot that has finished communication with the terminal device is released, the time slot is isolated from other free time slots in the frame. In some cases, it cannot be allocated to one terminal device in connection with another empty time slot.

  Therefore, in the base station apparatus according to the embodiment of the present invention, time slots having a short interval from the frame end are ranked and specified, and the time slots are assigned to the terminal apparatuses in the specified order. As a result, when the time slot that has finished communication with the terminal device is released, the possibility that it is continuous with other empty time slots in the frame increases, and it is possible to apply efficient slot connection to the empty time slots. it can.

  FIG. 4 is a conceptual diagram showing a configuration of mobile communication system 100 according to the embodiment of the present invention. The mobile communication system includes a base station device 1 and a terminal device 2. In FIG. 4, three terminals, ie, the first terminal apparatus 2a, the second terminal apparatus 2b, and the third terminal apparatus 2c, which are collectively referred to as the terminal apparatus 2, are illustrated, but there are two or less or four or more terminal apparatuses. May be.

  FIG. 5 is a conceptual diagram showing the configuration of the base station apparatus 1 of FIG. In FIG. 5, the antenna 3a, the antenna 3b, the antenna 3c, and the antenna 3d, which are collectively referred to as the antenna 3, are arranged at intervals set according to the radio frequency, and transmit and receive radio frequency signals. The antenna 3 corresponds to the adaptive array antenna technology, and the directivity of the antenna is controlled by a transmission / reception unit 5 described later. Although the number of antennas 2 is “4” in FIG. 5, other numbers may be used.

  The radio unit 4 performs frequency conversion on a radio frequency signal received by the antenna 3 during reception, derives a baseband signal, and outputs the baseband signal to the transmission / reception unit 5. In addition, the baseband signal from the transmission / reception unit 5 is frequency-converted during transmission to derive a radio frequency signal.

  The transmission / reception unit 5 weights and adds each of the reception signals sent from the radio unit 4 with the reception weight vector derived from the reception signal at the time of reception. As a method for deriving the reception weight vector, there are LMS (Least Mean Squeare), RLS (Recursive Least Square) algorithm and the like. The preamble PR shown in FIG. 3 is used as a reference signal for these algorithms.

  The transmission / reception unit 5 estimates a transmission weight vector necessary for weighting the transmission signal from the reception weight vector during transmission. As a method of estimating the transmission weight vector, there is a method of using the reception weight vector as it is. Further, the reception weight vector may be corrected in consideration of the Doppler frequency fluctuation of the propagation environment caused by the time difference between reception and transmission.

  The modem unit 6 demodulates the input from the transmission / reception unit 5 at the time of reception, and outputs the result to the IF unit 7. Further, the modem unit 6 outputs a signal modulated at the time of transmission to the transmission / reception unit 5. As a modulation method, π / 4 shift QPSK (Quadrature Phase Shift Keying), BPSK (Binary Phase Shift Keying), QPSK, 8QPSK, 12QAM (Quadrature Amplitude Modulation) or the like is used.

  The IF unit 7 is connected to a network (not shown), and outputs a signal demodulated by the modem unit 6 during reception to a network (not shown). Further, the IF unit 7 inputs data from the network at the time of transmission, and outputs this to the modem unit 6.

  The communication quality measuring unit 8 measures the communication quality of the signal transmitted from the terminal device 2 and outputs it to the control unit 9. As the communication quality, for example, a D / U ratio is derived. The communication quality measuring unit 8 measures the reception level of the signal transmitted from the terminal apparatus 2 when the terminal apparatus 2 makes a radio resource acquisition request to the base station apparatus 1 and sets it as the D wave level. In addition to the radio resource acquisition request, the reception level of the radio resource acquisition re-request or service flow addition request may be measured to obtain the D wave level. Further, the communication quality measuring unit 8 derives the D / U ratio by dividing the D wave level by the U wave level with the reception level in the empty time slot to be assigned as the U wave level. When SDMA (Space Division Multiple Access) is used as in the embodiment of the present invention, the reception level may be derived based on the reception weight vector or may be derived from the signal strength of the radio frequency.

  The control unit 9 receives the communication request notified from the IF unit 7 and the received signal sent from the modem unit 5 and assigns a radio channel to the terminal device 2 that should communicate with the base station device 1. In addition, the timing of the entire base station apparatus 1 is controlled. In TDMA, a time slot is assigned to the terminal device 2 to communicate with the terminal device 2, so that the radio channel corresponds to a time slot.

  The control unit 9 includes a radio resource management unit 9 a that manages time slots that can be allocated to the terminal device 2.

  Further, the control unit 9 receives the information sent from the radio resource management unit 9a and the information sent from the channel allocation unit 9c as inputs, and specifies the time slot to be allocated to the terminal device with priority and identifies the slot identification unit 9b. including. The priority is set so that the time slots located at a short time interval from the time slots at both ends of the frame are higher. When the time slots are positioned at the same interval from the time slots at both ends of the frame, the priority is set higher for the time slot adjacent to the time slot to which the terminal device is assigned.

  The control unit 9 further includes a channel allocation unit 9c that allocates time slots, which are radio channels, to the terminal device 2.

  6 and 7 are conceptual diagrams illustrating an example of time slot allocation by the channel allocation unit 9c. Each of FIG. 6 and FIG. 7 includes the first to fourth time slots of the uplink in one frame. In each of FIGS. 6 and 7, “terminal device 2a” and “terminal device 2b” are displayed in rectangles described in each time slot, and “terminal device 2a” and “terminal device 2b” are displayed. Indicates that it is assigned to the corresponding time slot.

  FIG. 6 shows a frame configuration in which one time slot is allocated to a terminal apparatus that has made a single time slot allocation request (for example, a voice call) when all the time slots in the frame are empty time slots.

  In the example of allocation shown in FIG. 6, the slot identifying unit 9b that has received information from the radio resource management unit 9a that all the time slots in the frame are vacant time slots has the highest priority in order from the time slots at both ends of the frame. Add. At this time, when there are a plurality of time slots having the same priority, the priority is set so that the priority of the time slot with high communication quality is high. Since the first time slot and the fourth time slot have the same distance from the frame end, the slot identifying unit 9b accepts the D / U ratio of the first time slot and the fourth time slot from the communication quality measuring unit 8. To do. Here, it is assumed that the communication quality of the first time slot is higher than the communication quality of the fourth time slot. For this reason, the slot identifying unit 9b gives priority “1” to the first time slot and gives priority “2” to the fourth time slot.

  Next, among the free time slots in the frame excluding the first time slot and the fourth time slot, the second time slot and the third time slot closest to the time slots at both ends of the frame are prioritized. Since the second time slot and the third time slot are the same from the frame end, the slot specifying unit 9b determines the D / U ratio between the second time slot and the third time slot from the communication quality measuring unit 8. Accept. Here, it is assumed that the communication quality of the second time slot is higher than the communication quality of the third time slot. For this reason, the slot identifying unit 9b gives priority “3” to the second time slot and gives priority “4” to the third time slot. Since priority is given to all the empty time slots, this information is sent to the channel allocation unit 9c.

  The channel allocation unit 9c receives the D / U ratio of the empty time slot from the communication quality measurement unit 8, and based on the priority sent from the slot identification unit 9c, the highest time slot and the fourth time slot are sequentially ordered. Then, it is determined whether or not the communication quality of each time slot exceeds a threshold value to which the terminal device 2a can be assigned.

  In the example of assignment shown in FIG. 6, since the first time slot exceeds this threshold, the first time slot is assigned to the terminal device 2a.

  FIG. 7 shows a frame configuration in which one time slot is allocated to a terminal device that has made a single time slot allocation request (for example, a voice call) when the third time slot in the frame has been allocated.

  In the allocation example shown in FIG. 7, the first time slot and the fourth time slot, which are time slots at both ends of the frame, are empty time slots. Therefore, if priority is given only by the proximity from the frame end, the first time slot is assigned. And the fourth time slot has the highest priority in the frame. However, if a new terminal device is assigned to the first time slot according to the priority order, the empty time slots after the assignment of the first time slot become the second time slot and the fourth time slot, and there are 2 in the frame. Two empty time slots are not consecutive. On the other hand, if a new terminal device is assigned to the fourth time slot, the empty time slots after the assignment of the fourth time slot are the first time slot and the second time slot, and these two empty time slots are continuous. In other words, when there are time slots to which terminal devices are assigned, it is preferable to give higher priority to time slots adjacent to the time slots in order to increase consecutive free time slots.

  Therefore, the slot identifying unit 9b that has received information from the radio resource management unit 9a that the time slots other than the third time slot in the frame are empty time slots are the time slots at both ends of the frame, and the third time slot. A high priority (here, “1”) is assigned to the fourth time slot adjacent to the slot. The first time slot is assigned a lower priority (here, “2”). Of the empty time slots in the frame excluding the first time slot and the fourth time slot, the second time slot closest to the time slots at both ends of the frame is given the next highest priority (here, “3”). Since priority is given to all the empty time slots in the frame, this information is sent to the channel allocation unit 9c.

  The channel allocating unit 9c receives the D / U ratio of the empty time slot from the communication quality measuring unit 8, and based on the priority sent from the slot specifying unit 9c, the time slot communication is performed in order from the highest fourth time slot. It is determined whether or not the quality exceeds a threshold value to which the terminal device 2a can be assigned.

  In the allocation example shown in FIG. 7, since the fourth time slot exceeds this threshold, the fourth time slot is allocated to the terminal device 2b.

  The operation of the base station apparatus 1 having the above configuration will be described. FIG. 8 is a sequence diagram showing a communication start procedure by the mobile communication system. The terminal device 2 transmits a radio resource acquisition request to the base station device 1 (S10). The base station apparatus 1 performs channel allocation to the terminal apparatus 2 (S20), and then transmits radio resource allocation to the terminal apparatus 2 (S30). Thereafter, the base station apparatus 1 and the terminal apparatus 2 perform communication using the TCH that has established synchronization.

  9, 10 and 11 are flowcharts showing channel assignment performed by the base station apparatus 1. FIG.

  When there is a radio resource acquisition request, the control unit 9 confirms the use state of the time slot by the radio resource management unit 9a, and instructs the communication quality measurement unit 8 to derive the D / U ratio for each empty time slot (S2000). ). The communication quality measuring unit 8 measures the U wave for each empty time slot, measures the D wave of the terminal device 2 that has requested to acquire radio resources, derives the D / U ratio for each empty time slot, and Output to 9.

  The control unit 9 determines whether or not the radio resource acquisition request from the terminal device 2 is slot concatenation allocation (S2001). If it is not slot concatenation allocation (N in S2001), the control unit 9 instructs the slot specifying unit 9b to prioritize the empty time slots in the frame.

  Based on the information sent from the radio resource management unit 9a, the slot specifying unit 9b determines whether or not there is a time slot to which the terminal device has been assigned in the frame (S2002). If it exists (Y in S2002), it is determined whether there are time slots at both ends of the frame adjacent to the time slot to which the terminal device has been assigned (S2003). If it exists (Y in S2003), the time slot is given the highest priority (S2004).

  On the other hand, when there is no time slot assigned to the terminal device in the frame (N in S2002), or when there are no time slots at both ends of the frame adjacent to the time slot to which the terminal device is assigned (S2003 N) It is determined whether or not there are a plurality of time slots that are close to the time slots at both ends of the frame among the empty time slots (S2005). If it exists (Y in S2005), refer to the D / U ratio sent from the communication quality measurement unit 8 and prioritize those time slots so that the priority of time slots with good communication quality becomes higher. (S2006). Then, priorities are assigned in order from empty time slots close to both ends of the frame (S2007).

  When the slot specifying unit 9b gives priority to all the empty time slots in the frame, the result is sent to the channel allocating unit 9c.

  When receiving a response indicating that the priority is given from the slot specifying unit 9b, the control unit 9 instructs the channel allocation unit 9c to perform radio channel allocation for the terminal device 2.

  The channel assigning unit 9c determines the D / U ratio sent from the communication quality measuring unit 8 in order from the time slot with the highest priority based on the priority of empty time slots in the frame sent from the slot specifying unit 9b. It is referred and it is determined whether or not the terminal device 2 can be assigned to the time slot (S2008). Whether or not the allocation is possible is determined by whether or not the D / U ratio of the time slot exceeds a first threshold value related to communication quality.

  When the D / U ratio of the time slot exceeds the assignable first threshold value (Y in S2008), channel assignment is performed and the terminal device 2 is assigned to the time slot (S2009). On the other hand, if the D / U ratio of the time slot is smaller than the assignable first threshold (N in S2008), the time slot is excluded from the assignment target (S2010), and the time slot with the next highest priority is selected. The above operation is repeated until there is no time slot to be allocated (N in S2011) or until channel allocation is performed (S2009).

  According to such an embodiment of the present invention, the following operational effects can be enjoyed.

  The slot specifying unit 9b assigns a higher priority in order from the time slots closest to both ends of the frame among the empty time slots in the frame, and the channel allocation unit 9c starts from the time slot having the highest priority based on the priority. Since it is assigned to a terminal device, when a time slot that has finished communication with the terminal device is released, there is a higher possibility that it is continuous with other free time slots in the frame, and efficient slot concatenation for free time slots is applied. Transmission efficiency can be improved.

  Further, the slot identifying unit 9b assigns a high priority to the time slots that are closest to the time slots at both ends of the frame and are adjacent to the time slots to which the terminal device has been allocated among the free time slots in the frame. Even when there is a time slot to which the terminal device is already assigned in the frame, there is a high possibility that the empty time slot is continuous after assigning the time slot. Can be applied to improve the transmission efficiency.

  Further, the communication quality measuring unit 8 measures the communication quality with the terminal device for each empty time slot, and the slot specifying unit 9b determines from the time slots at both ends of the frame among the empty time slots in the frame. When there are multiple time slots with the same proximity, a higher priority is given to time slots with higher communication quality, so that the idle time is improved while improving the transmission quality with the terminal device that has made a single time slot allocation request. Transmission efficiency can be improved by applying efficient slot connection to the slots.

  Further, the channel allocation unit 9c determines whether or not to allocate a time slot to the terminal device based on the communication quality and priority of the empty time slot, so that the empty time slot is maintained while maintaining the transmission quality with the terminal device. Efficient slot connection can be applied to improve transmission efficiency.

  Although the best mode for carrying out the present invention has been described above, the present invention is not limited to the configuration of this embodiment, and the scope of application of the present invention defined in the claims. As long as the functions of the configuration of the above-described embodiment can be achieved, various modifications are possible.

  For example, in the embodiment of the present invention, the communication system 100 is described as being applied with TDMA and SDMA. However, the communication system 100 is not limited to this, and it is sufficient that at least TDMA is applied. For example, TDMA and CDMA (Code Division Multiple Access) may be applied, and TDMA and OFDMA (Orthogonal Frequency Division Multiple Access) may be applied.

Conceptual diagram showing the TDMA frame structure Conceptual diagram showing spatially multiplexed time slots by SDMA Conceptual diagram showing the structure of a time slot The conceptual diagram which shows the structure of the communication system which concerns on embodiment of this invention The conceptual diagram which shows the structure of the base station apparatus which concerns on embodiment of this invention Diagram showing an example of slot assignment Diagram showing an example of slot assignment The sequence diagram which shows the communication start procedure of the communication system which concerns on embodiment of this invention Flow chart showing an example of slot assignment operation Flow chart showing an example of slot assignment operation Flow chart showing an example of slot assignment operation

Explanation of symbols

4 Radio section 5 Transceiver section 6 Modulation / demodulation section L
7 IF unit 8 Communication quality measurement unit 9 Control unit 9a Radio resource management unit 9b Slot identification unit 9c Channel allocation unit

Claims (5)

  An allocation method comprising: constructing a frame from a plurality of continuous time slots, assigning priorities from time slots close to the end of the frame, and allocating the frames in that order. An allocation unit that configures a frame from a plurality of consecutive time slots and allocates the time slots to the terminal device;
With a specific part that specifies the priority from the time slot near the frame end,
The base station device, wherein the assigning unit assigns time slots to terminal devices in the specified order.   The base station apparatus according to claim 2, wherein the specifying unit increases a rank of a time slot adjacent to a time slot to which a terminal apparatus is already assigned. A communication quality measuring unit for measuring communication quality between the plurality of terminal devices;
4. The base station apparatus according to claim 2, wherein, when there are a plurality of time slots having the same priority, the specifying unit increases the rank of the time slot having the higher communication quality. 5. The base station apparatus according to claim 4, wherein the allocation unit performs the allocation if the communication quality exceeds a threshold value related to communication quality.

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