JP2019041175A - Tdma narrow-band digital cordless telephone system, carrier sense control method and program therefor - Google Patents

Abstract

To provide a TDMA narrow-band digital cordless telephone system comprising a carrier sense function capable of detecting a radio signal of a short signal length even under a communication environment that such a radio signal is transmitted.SOLUTION: At a front-edge part carrier measurement point RSSI0 and a rear-edge part carrier measurement point RSSI2 in a front edge part 41 and a rear edge part 43 of a slot 40 scheduled to be used corresponding to a frequency scheduled to be used, a reception signal strength is measured at a fixed time point on a time base over all measurement frames for a predetermined number of frames. At a central part carrier measurement point RSSI1 in a central part 42, a reception signal strength is measured at each of time points of a first central part carrier measurement point RSSI1<1> to a seventh central part carrier measurement point RSSI1<7> moved to a measurement time point shifted on the time base at a predetermined time interval (e.g., 79 μsec for 30 bits) for each of the measurement frames.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a TDMA narrow-band digital cordless telephone system, a carrier sense control method, and a carrier sense control program, and in particular, a TDMA system that avoids radio wave interference with a TDMA wide-band digital cordless telephone system that uses the same frequency band. The present invention relates to a narrowband digital cordless telephone system, a carrier sense control method, and a carrier sense control program.

  A PHS (Personal Handy-Phone System) system (that is, a TDMA (Time Division Multiple Access) narrowband digital cordless telephone system) and a J-DECT (Japanese-Digital Enhanced Cordless Telecommunications) system (that is, a TDMA (Time Division Multiple Access) system) that uses a 1.9 GHz frequency band. In the two digital cordless telephone systems (TDMA wideband digital cordless telephone system), the frequency bands used are 1893.55 to 1905.95 MHz and 1894.752 to 1903.392 MHz, and the frequency bands used are overlapping. doing. FIG. 5 is a schematic diagram for explaining the use frequency bands of the business PHS system and the J-DECT system.

  As shown in FIG. 5, the PHS system for offices using the 1.9 GHz frequency band has a frequency range of 1893.65 MHz to 1905.95 MHz, but is installed in Japan as a DECT digital cordless telephone system of 1.9 GHz band. As described above, the usable frequency band of the J-DECT system is 1894.752 to 1903.392 MHz, which overlaps with 1893.65 MHz to 1905.95 MHz of the office PHS system.

  The J-DECT system includes F1 channel (1894.752 MHz to 1896.480 MHz, center frequency 1895.616 MHz), F2 channel (189.480 MHz to 1898.208 MHz, center frequency 1897.344 MHz), F3 channel (1898.208 MHz). -1899.936 MHz, center frequency 1899.072 MHz), F4 channel (1899.936 MHz to 1901.664 MHz, center frequency 1900.800 MHz) and F5 channel (1901.664 MHz to 1903.392 MHz, center frequency 1902.528 MHz) Use of the channel is allowed.

  On the other hand, as shown in FIG. 5, the PHS system for offices uses a frequency band of 1893.65 MHz to 1905.95 MHz for a total of 22 channels of 1 ch to 10 ch, 14 ch to 16 ch, 20 ch to 37 ch, 251 ch to 255 ch. It can be divided into channels and used as communication channels. Among these 22 channels, channels 29 to 37 and 251 to 255 shown as band 0 in FIG. 5 have no frequency overlap with the J-DECT system, but the other channels are the same as the J-DECT system. The frequency overlap occurs.

  That is, as shown in FIG. 5, the five channels 1ch to 5ch shown as band 1 in the office PHS system overlap with the F1 channel of the J-DECT system and the frequency band 6ch to 10ch shown as band 2 These five channels overlap in frequency band with the F2 channel of the J-DECT system. Further, in the office PHS system, the three channels 14 to 16 shown as band 3 overlap with the F3 channel of the J-DECT system, and the four channels 20 to 23 shown as band 4 are J -The frequency band overlaps with the F4 channel of the DECT system. The five channels 24 to 28 shown as band 5 in the business PHS system overlap with the F5 channel of the J-DECT system.

  Therefore, when the two digital cordless telephone systems having overlapping usage frequency bands exist in the same service area, when the frequency bands to be used are close and the timing of the time division method overlaps Causes mutual radio wave interference, and an error occurs in audio data used for a call and control data required for functional operation.

  Usually, as a means for avoiding such a situation, for example, as described in Japanese Patent Laid-Open No. 2015-23565 “Digital Cordless Telephone System for Offices, Interference Avoidance Method and Interference Avoidance Program” of Patent Document 1, used as a carrier When a frequency to be transmitted is selected, a carrier sense operation is started, and a signal reception at the frequency is performed for a certain period of time prior to transmission of the signal at the frequency. ) Will be present and will check for interference. When carrier sense is performed and a radio wave (carrier) of another wireless communication system that becomes an interference source is detected, interference is detected by reselecting and using a frequency other than the frequency band of the radio wave (carrier). It can be avoided.

Japanese Patent Laid-Open No. 2015-23565

  However, in the current technology related to the present invention as described in Patent Document 1, a radio signal having a signal length shorter than the carrier sense execution interval (that is, a carrier having a short transmission time) is always transmitted. With respect to other wireless communication systems such as J-DECT systems that transmit depending on the situation, the wireless signal with a short signal length that is being transmitted cannot be detected by carrier sense depending on the timing. A case will arise. When such a phenomenon occurs, radio wave interference with other wireless communication systems may occur, causing a communication failure. Specifically, not only the occurrence of call noise, but also an error in the control data may cause problems such as disconnection of calls, inability to receive calls, frequent interference avoidance operations, or inability to operate keys. May cause serious problems.

(Object of the present invention)
The present invention has been made in view of such a situation, and even when the carrier transmission time is short using the same frequency band as in a TDMA wideband digital cordless telephone system such as a J-DECT system. , A mechanism capable of surely sensing the carrier, that is, a carrier sensing mechanism capable of detecting the radio signal even in a communication environment where a radio signal having a short signal length is transmitted. An object of the present invention is to provide a TDMA narrowband digital cordless telephone system, a carrier sense control method, and a carrier sense control program.

  In order to solve the above-described problems, the TDMA narrowband digital cordless telephone system, carrier sense control method, and carrier sense control program according to the present invention mainly adopt the following characteristic configuration.

(1) A TDMA narrowband digital cordless telephone system according to the present invention is:
In a TDMA narrowband digital cordless telephone system composed of a digital cordless base station and a digital cordless handset having a carrier sense function for avoiding radio wave interference with other wireless communication systems using the same frequency band,
The digital cordless base station and the digital cordless slave unit are:
For each successive measurement frame consisting of a number of frames corresponding to a predetermined number of measurements, the measurement points for the leading edge, center and trailing edge of the slot corresponding to the frequency to be used are respectively measured at the leading edge carrier measurement point. When measuring the received signal strength at each measurement point as the center carrier measurement point and the trailing edge carrier measurement point,
At the leading edge carrier measurement point and the trailing edge carrier measurement point, the received signal strength is measured the number of times measured at a fixed point on the time axis over all the measurement frames,
On the other hand, the center carrier measurement point is moved to a measurement point shifted on the time axis by a predetermined time interval for each measurement frame for the number of measurements, and the moved measurement point is The received signal strength is measured as a partial carrier measurement point.

(2) A carrier sense control method according to the present invention includes:
Carrier sense in a TDMA-type narrowband digital cordless telephone system comprising a digital cordless base station and a digital cordless slave unit having a carrier sense function for avoiding radio wave interference with other wireless communication systems using the same frequency band A control method,
The digital cordless base station and the digital cordless slave unit are:
For each successive measurement frame consisting of a number of frames corresponding to a predetermined number of measurements, the measurement points for the leading edge, center and trailing edge of the slot corresponding to the frequency to be used are respectively measured at the leading edge carrier measurement point. When measuring the received signal strength at each measurement point as the center carrier measurement point and the trailing edge carrier measurement point,
At the leading edge carrier measurement point and the trailing edge carrier measurement point, measuring the received signal strength by the number of times of measurement at a fixed time point on the time axis over all the measurement frames;
On the other hand, the center carrier measurement point is moved to a measurement point shifted on the time axis by a predetermined time interval for each measurement frame for the number of measurements, and the moved measurement point is Measuring the received signal strength as a partial carrier measurement point.

(3) A carrier sense control program according to the present invention includes:
The carrier in a TDMA-type narrowband digital cordless telephone system comprising a digital cordless base station and a digital cordless handset having a carrier sense function for avoiding radio wave interference with other wireless communication systems using the same frequency band A carrier sense control program for executing sense control by a computer,
The digital cordless base station and the digital cordless slave unit are:
For each successive measurement frame consisting of a number of frames corresponding to a predetermined number of measurements, the measurement points for the leading edge, center and trailing edge of the slot corresponding to the frequency to be used are respectively measured at the leading edge carrier measurement point. When measuring the received signal strength at each time point as the center carrier measurement point and the trailing edge carrier measurement point,
In the leading edge carrier measurement point and the trailing edge carrier measurement point, a process of measuring the received signal strength by the number of times of measurement at a fixed point on the time axis over all the measurement frames;
On the other hand, the center carrier measurement point is moved to a measurement point shifted on the time axis by a predetermined time interval for each measurement frame for the number of measurements, and the moved measurement point is And a process of measuring the received signal strength as a partial carrier measurement point.

  According to the TDMA narrowband digital cordless telephone system, carrier sense control method, and carrier sense control program of the present invention, the carrier measurement point is two points on both sides of the three-point measurement on the time axis (the leading edge carrier measurement point, the rear The time interval between the carrier measurement points (edge carrier measurement points) is fixed without changing, and the time position of the center one carrier measurement point (center carrier measurement point) is slightly shifted each time according to the order of the number of measurements. However, the following effects can be achieved because a mechanism for performing the measurement a plurality of times is employed.

  That is, in the present invention, the signal length transmitted by other wireless communication systems such as a TDMA wideband digital cordless telephone system such as a J-DECT system, which could not be detected by the carrier sense control method in the current technology, is short. Since radio signals can also be detected, mutual interference between TDMA narrowband digital cordless telephone systems such as office PHS systems and TDMA wideband digital cordless telephone systems such as J-DECT systems can be prevented. It is possible to avoid it reliably, and it is possible to improve the frequency utilization efficiency.

1 is a system configuration diagram showing an outline of a system configuration of a business PHS system as an example of a TDMA narrowband digital cordless telephone system according to the present invention. It is a schematic diagram for demonstrating the carrier sense operation | movement of the PHS system for offices in the present technique. It is a schematic diagram for demonstrating an example of the carrier sense operation | movement of the office PHS system in this embodiment shown in FIG. It is a flowchart for demonstrating an example of the flow of the carrier sense operation | movement of the office PHS system in this embodiment shown in FIG. It is a schematic diagram for demonstrating the use frequency band of the PHS system for business establishments, and a J-DECT system.

  Hereinafter, preferred embodiments of a TDMA narrowband digital cordless telephone system, a carrier sense control method, and a carrier sense control program according to the present invention will be described with reference to the accompanying drawings. In the following description, a TDMA narrowband digital cordless telephone system and a carrier sense control method according to the present invention will be described. However, the carrier sense control method is implemented as a carrier sense control program executable by a computer. Needless to say, the carrier sense control program may be recorded on a computer-readable recording medium. In addition, it is needless to say that the drawing reference numerals attached to the following drawings are added for convenience to the respective elements as an example for facilitating understanding, and are not intended to limit the present invention to the illustrated embodiments. Yes.

(Features of the present invention)
Prior to the description of the embodiments of the present invention, an outline of the features of the present invention will be described first. The present invention provides a TDMA narrowband digital cordless telephone system that shares the same frequency band with other wireless communication systems, and the other wireless communication system transmits a short-time signal by improving the carrier sense control method. Even if it is, the main feature is to be able to reliably detect and avoid radio wave interference (although it was impossible to detect with the current technology). Here, the carrier sense control method to be improved is as follows. That is, as in the current technology, when sensing the RSSI (Received Signal Strength Indicator) level at the three points of the front edge, center, and rear edge of the time slot of the frequency band to be used, For the leading edge and the trailing edge, carrier sensing is performed at a fixed time position without changing the time position each time measurement is performed. However, unlike the current technology, the center portion is not fixed at an intermediate position between the front edge portion and the rear edge portion, but is sensed at a time position that is gradually shifted at a predetermined short time interval. The main feature is that the operation is repeated a plurality of times (for a predetermined number of measurements). The improvement of the carrier sense control method does not require any change in the hardware of the TDMA narrowband digital cordless telephone system, and is realized by changing the software of the carrier sense function (that is, the carrier sense control program). be able to.

  Thus, for example, even in a radio wave environment where a TDMA type narrow band digital cordless telephone system and a TDMA type wide band digital cordless telephone system such as a J-DECT system using the same frequency band coexist, the current technology detects. It is possible to detect the presence of the TDMA wideband digital cordless telephone system that could not be performed using the carrier sensing function of the three-point measurement method similar to the current technology, and to select an appropriate frequency band. Can solve the problem.

  In other words, the present invention relates to a time interval (for example, 228 bits) between two carrier measurement points on both sides of a three-point measurement on the time axis as a carrier measurement point in a TDMA-type narrowband digital cordless telephone system such as an office PHS system. (297 μsec × 2 = 594 μsec) is fixed without change, and the carrier measurement point at the center is shifted a little (for example, 79 μsec for 30 bits) each time in accordance with the order of the number of times of measurement. : 79 μsec × 7 times = 553 μsec) is a main feature.

  Thus, with the current technology, even if a TDMA digital cordless telephone system that sends out signals at short intervals in the same frequency band exists in the same area, the presence is reliably detected. Therefore, radio wave interference can be reliably avoided, and the operation and communication quality of the TDMA narrowband digital cordless telephone system can be stabilized.

  In the current carrier sense control method, as in the case of the present invention, the operation of sensing the three points of the front edge portion, the center portion, and the rear edge portion of the time slot of the frequency band to be used is performed a plurality of times. Unlike the present invention, since the carrier sense is performed in a state where the positions of the three points are fixed at predetermined constant time intervals, as described above, the same frequency band is used. If there is another wireless communication system such as a TDMA wideband digital cordless telephone system that outputs a signal at a time interval shorter than the time interval of carrier sense in the same area, the other wireless communication system There is a possibility that a signal at a short time interval to be transmitted cannot be reliably detected, which may cause radio wave interference.

(Configuration example of embodiment of the present invention)
Next, a configuration example of an embodiment of a TDMA narrowband digital cordless telephone system according to the present invention will be described with reference to the drawings. As an example of the TDMA narrow-band digital cordless telephone system, in the following embodiment, a case where a business-use PHS system (Personal Handy-Phone System) is used will be described. A case where a J-DECT system (Japanese-Digital Enhanced Cordless Telecommunications System: that is, a TDMA wideband digital cordless telephone system) using substantially the same frequency band exists in an area in the vicinity of the office PHS system. explain.

  FIG. 1 is a system configuration diagram showing an outline of the system configuration of a business PHS system as an example of a TDMA narrowband digital cordless telephone system according to the present invention. FIG. 1 shows a case where there is a J-DECT system 20 that has a service area that partially overlaps the service area of the office PHS system 10 and uses substantially the same frequency band. Here, as shown in FIG. 1, the usage frequency of the business PHS system 10 is 1893.55 to 1905.95 MHz, the usage frequency of the J-DECT system 20 is 1894.752 to 1903.392 MHz, Almost the same frequency band is used as a communication channel.

  As shown in FIG. 1, the business PHS system 10 includes a main device (ME) 13 connected to the outside line 30, and is connected to the main device 13 and exists in the area 15 of the business PHS system 10. A PHS base station (CS: Cell Station) 14 is connected to a plurality of PHS slave stations (PS: Personal Station). In FIG. 1, there are a first PHS slave unit 11 and a second PHS slave unit 12 as a plurality of PHS slave units existing in the area 15. The first PHS slave unit 11 overlaps with the area 25 of the J-DECT system 20. The second PHS slave unit 12 is in the area 15 that is not in the area 15 but is in the area 15 but in the overlap area 16 that overlaps the area 25 of the J-DECT system 20. Yes.

  Further, as shown in FIG. 1, the J-DECT system 20 is connected to the outside line 30 and is connected to a plurality of DECT slave units (PS) existing in the area 25 of the J-DECT system 20. (CS) 23. In FIG. 1, there are a first DECT slave unit 21 and a second DECT slave unit 22 as a plurality of DECT slave units existing in the area 25, and the first DECT slave unit 21 overlaps with the area 15 of the business PHS system 10. The second DECT slave unit 22 is in the area 25 that is not in the area 25 but is in the area 25 but in the overlapping area 16 that overlaps the area 15 of the business PHS system 10. Yes.

  When the second PHS slave unit 12 and the second DECT slave unit 22 existing in the overlapping area 16 shown by the broken line in FIG. 1 are wirelessly connected, radio wave interference occurs if the used frequencies are the same. there is a possibility.

  The PHS base station (CS) 14 and the DECT master station (CS) 23 are examples of a digital cordless telephone base station of the TDMA narrowband cordless telephone system and a digital cordless telephone master of the TDMA wideband cordless telephone system, respectively. The PHS handset (PS) and the DECT handset (PS) are examples of a digital cordless telephone handset of the TDMA narrowband cordless telephone system and a digital cordless telephone handset of the TDMA wideband cordless telephone system, respectively. is there.

  Here, the PHS base station (CS) 14 and the PHS slave units (PS) of the first PHS slave unit 11 and the second PHS slave unit 12 are described below in order to monitor the possibility of radio wave interference. It has various functions. The DECT master station (CS) 23 and the DECT slave units (PS) of the first DECT slave unit 21 and the second DECT slave unit 22 also have similar functions. Since the carrier sense control method implemented as a countermeasure against radio wave interference in FIG. 10 will be described, the description on the DECT system 20 side will be omitted below.

  (1) The PHS base station (CS) 14 and each PHS slave (PS) of the first PHS slave 11 and the second PHS slave 12 receive carrier measurement points, that is, RSSI measurement points (RSSI (Received Signal Strength Indicator: reception)). It has a function that makes it possible to change the time position on the time axis of the measurement time) at which the signal intensity) is measured by a carrier sense control program or a register value.

  (2) The PHS base station (CS) 14 and each PHS slave (PS) of the first PHS slave 11 and the second PHS slave 12 have M points per slot (M: positive integer) for transmitting signals. ) RSSI measurement points are set, and M or more memory areas capable of storing RSSI values (register values) measured at the set RSSI measurement points are provided. In the following description, as an example, regarding M RSSI measurement points, one measurement point is set for each of the front and rear edges of the slot of the frequency band to be used, and seven measurement points are set in the center. Suppose that a memory area capable of storing a total of nine RSSI values for a preset number of times is provided.

  (3) The PHS base station (CS) 14 and the PHS slave units (PS) of the first PHS slave unit 11 and the second PHS slave unit 12 measure the number of measurement frames for measuring each RSSI value as a carrier sense, that is, each RSSI value. Has a function that makes it possible to change the number of times of measurement by a carrier sense control program or a register value.

(Description of operation example of embodiment of this invention)
Next, as an example of the TDMA system narrow band digital cordless telephone system according to the present invention, as an example of the operation of the business PHS system 10 illustrated in FIG. Will be described.

  The PHS base station (CS) 14 and each PHS slave (PS) of the first PHS slave 11 and the second PHS slave 12 receive carrier interference (radio wave interference) when a link channel establishment request is made and when a link channel assignment is executed. ) First, carrier sense is performed prior to the signal transmission operation, and the RSSI (1 slot length) of the carrier in the reception slot section (1-slot length section) of the link channel assigned to the signal is first detected. Monitor received signal strength level. As a result of the carrier sense, when the following “carrier availability determination condition” is satisfied, radio wave interference does not occur and the carrier of the link channel can be used. And the signal transmission / reception operation is started using the frequency of the carrier.

"Carrier availability criteria"
: “As carrier sense performed within 2 seconds prior to signal transmission, over multiple consecutive frames (eg, 4 frames for full rate, 2 significant frames for half rate (public only)) or more, In the reception slot section allocated to the signal, a reception signal having a carrier level lower than a predetermined threshold level continues, and a vacant state that can be regarded as having no reception signal continues. "

  Next, in order to make it easy to understand the operation of the present embodiment, first, problems at the time of carrying out carrier sense in the PHS system for offices of the current technology will be described with reference to the schematic diagram of FIG.

  Note that, in the PHS system for offices in the current technology as well, in the same way as in the present embodiment, in general, in order to confirm whether or not the “carrier use determination condition” is satisfied, 2 prior to signal transmission. Within two seconds, RSSI (received signal strength, in other words, received electric field strength) at three points of the front edge portion, the center portion, and the rear edge portion of one reception slot section of the link channel assigned to the signal is continuously four frames. When the maximum value of the measured RSSI is lower than a threshold level determined in advance as a carrier level threshold, it is determined that the link link is an empty link channel that does not cause radio wave interference. The operation of transmitting and receiving signals is started using the frequency of the link channel.

  FIG. 2 is a schematic diagram for explaining the carrier sense operation of the business PHS system in the current technology. For example, when a link channel establishment request is generated in the PHS base station, prior to the establishment of the link channel, the current technology uses the link channel to be transmitted by the PHS base station as shown in FIG. The received signal strength (RSSI) is set to a predetermined number of consecutive frames (for example, 4 frames) at each of the three carrier measurement points RSSI0, RSSI1, and RSSI2 of the front edge portion 41, the central portion 42, and the rear edge portion 43 of the scheduled slot 40. ) Measure over the above. Then, for example, as a measurement result of the Nth (the Nth frame in which the RSSI value is measured) in each of the leading edge carrier measurement point RSSI0, the center carrier measurement point RSSI1, and the trailing edge carrier measurement point RSSI2, FIG. As shown, the received signal strengths (RSSI) of RSSI0 (N), RSSI1 (N), and RSSI2 (N) are obtained (for example, N = 1, 2 when the predetermined number of measurements is four). , 3, 4).

  When the predetermined N times (for example, N = 4) measurement is completed, the maximum value of the received signal strength RSSI is extracted from the first to fourth measurement results, and the maximum value is a predetermined carrier. If it is confirmed that the frequency is lower than the sense threshold, the link channel frequency is determined to be empty, the link channel frequency is assigned for wireless communication, and wireless communication using the link channel frequency is performed. Establish.

  Here, one frame of the PHS system for offices is 5 msec and is composed of 8 slots, and the signal length of each slot is represented by a ramp bit (R) and a guard time (G) as shown in FIG. Including 625 μsec (240 bits). Then, the time point of the leading edge carrier measurement point RSSI0 is set as the leading time point of the ramp bit (R) of the slot, and the trailing edge carrier measurement point RSSI2 is set from the head of the guard time (G) located behind the slot. The time of the fourth bit (that is, the time of 228 bits (594 μsec) from the time of the leading edge carrier measurement point RSSI0) is fixed, and the time of the center carrier measurement point RSSI1 is the leading edge carrier measurement point RSSI0. And the time point of the trailing edge carrier measurement point RSSI2 (ie, 114 bits (297 μsec) from each of the time point of the leading edge carrier measurement point RSSI0 and the time point of the trailing edge carrier measurement point RSSI2). Time).

  Therefore, in the carrier sense in the current technology, as shown in FIG. 2, the respective time points of the leading edge carrier measurement point RSSI0, the central carrier measurement point RSSI1, and the trailing edge carrier measurement point RSSI2 are separated by 297 μsec. Since the time is fixed, a signal having a signal length of 297 μsec or more can be reliably detected. However, there is a problem that a signal having a signal length of less than 297 μsec may not be detected even if the carrier sense is repeated a plurality of times (for example, four times) or more.

  For example, the signal length of each slot of the control slot and the communication slot used in the J-DECT system 20 that uses substantially the same frequency band as the PHS system for offices in the 1.9 GHz band depends on the communication application. The signal length is variable to any one of 3 μsec to 368.1 μsec, and is not a fixed signal length as in the case of an office PHS system. That is, in the J-DECT system 20, the DB (dam bearer) slot periodically transmitted during non-communication has a signal length of 83.3 μsec, 118.1 μsec, 152, 8 μsec, and communication. A TB (traffic bearer) slot that is sometimes transmitted has a signal length of 368.1 μsec. In the J-DECT system 20, one frame is 10 msec.

  Therefore, as long as the carrier sense of the current technology as shown in FIG. 2 is used, the business PHS system can detect a signal having a signal length of less than 297 μsec that the J-DECT system 20 may use. There are cases where it cannot be done. Thus, in an environment where the J-DECT system 20 that uses substantially the same frequency band is installed in the vicinity of the office PHS system, the frequency band permitted to be allocated as the link channel of the office PHS system is J -A frequency that overlaps with the frequency of the signal used by the DECT system 20 may occur, resulting in mutual radio wave interference.

  The office PHS system 10 according to the present embodiment additionally has a function that makes it possible to reliably avoid radio wave interference like this. Next, an example of carrier sense operation of the business PHS system 10 in the present embodiment will be described with reference to the schematic diagram of FIG. FIG. 3 is a schematic diagram for explaining an example of the carrier sense operation of the business PHS system 10 according to the present embodiment shown in FIG. 1. The PHS base station (CS) 14, the first PHS slave device 11, Each PHS handset (PS) of the 2PHS handset 12 has the following additional functions as described above.

  (1) The PHS base station (CS) 14 and each PHS slave (PS) of the first PHS slave 11 and the second PHS slave 12 measure carrier measurement points, that is, RSSI measurement points (RSSI (received signal strength)). It is possible to change the time position by a carrier sense control program or a register value at a measurement trigger point designated in advance by a program for controlling a radio signal in a reception slot. It has a function. The number of RSSI measurement points to be measured per frame is three as in the case of the current technology, but the time position of the RSSI measurement points can be changed, and control for performing the change is performed. The method varies depending on the hardware to be configured, and in the following description, for example, the time position is determined by a carrier sense control program.

  (2) The PHS base station (CS) 14 and the PHS slaves (PS) of the first PHS slave 11 and the second PHS slave 12 are measured at M (M: positive integer) RSSI measurement points. There are M or more memory areas that can store the RSSI values (register values). In the following description, as the M RSSI measurement points, the leading edge carrier measurement point RSSI0 is set at the leading edge 41 of the scheduled slot 40, and the trailing edge carrier measurement is set at the trailing edge 43 of the scheduled slot 40. One point RSSI2 is set one by one, and the center 42 of the scheduled slot 40 is set to 7 of the first center carrier measurement point RSSI1 <1> to the seventh center carrier measurement point RSSI1 <7>. The case of setting the number of measurement points will be described, and it is assumed that a memory area capable of storing a total of nine RSSI values for a predetermined number of measurements (N times) is provided.

  (3) Each PHS slave unit (PS) of the PHS base station (CS) 14 and the first PHS slave unit 11 and the second PHS slave unit 12 determines the number of measurements, that is, the number of measurement frames, for measuring the carrier level, that is, the RSSI value. It has a function that allows it to be changed by a carrier sense control program or a register value.

  As shown in the schematic diagram of FIG. 3, for example, when a link channel establishment request is generated in the PHS base station 14, prior to the establishment of the link channel, as in the case of the current technology shown in FIG. The received electric field strength (RSSI) is measured at each of the three carrier measurement points RSSI0, RSSI1, and RSSI2 of the leading edge 41, the central portion 42, and the trailing edge 43 of the scheduled use slot 40 of the link channel to be transmitted by the station 14. To do. However, in the present embodiment shown in FIG. 3, unlike the case of FIG. 2, the central carrier measurement point RSSI 1 set in the central part 42 of the scheduled use slot 40 is in the order of the number of measurements to be continuously measured. Accordingly, it is moved by a predetermined time interval and sequentially set to seven measurement points from the first center part carrier measurement point RSSI1 <1> to the seventh center part carrier measurement point RSSI1 <7>. Then, the RSSI value is measured at each moved time position. Further, unlike the case of FIG. 2, as shown in FIG. 3, the number of times of measurement N is 7 and the number of consecutive measurement frames N is 7 as the measurement frames for performing carrier measurement. In the present invention, the number of measurements N is not limited to seven, and may be any number of seven or more as long as the carrier sense operation is finished within two seconds (note that In the TDMA narrowband digital cordless telephone standard, it is defined as four times or more).

  As a result, in FIG. 3, at each of the leading edge carrier measurement point RSSI0, the first center carrier measurement point RSSI1 <1> to the seventh center carrier measurement point RSSI1 <7>, and the trailing edge carrier measurement point RSSI2. Received signal strengths (RSSI) of RSSI0 (N), RSSI1 (N), and RSSI2 (N) are obtained as measurement results of the Nth (measured Nth frame), respectively (for example, N = 1, 2, 3, 4, 5, 6, 7).

  Here, each time interval between the first center part carrier measurement point RSSI1 <1> to the seventh center part carrier measurement point RSSI1 <7>, that is, time for each frame in which the received signal strength RSSI is measured as carrier sense. A predetermined time interval for moving on the axis is determined as follows. That is, for example, as shown in FIG. 3, the remaining 212 bits are obtained by deleting the ramp bit (R), guard time (G), and 4 bits before and after the significant slot of the slot 40 to be used having a slot length of 240 bits. Is the central portion 42. Then, in consideration of the time position relationship with the leading edge carrier measurement point RSSI0 and the trailing edge carrier measurement point RSSI2, a non-measurement part is further provided by 16 bits before and after the central part 42, and the non-measurement part is excluded. The remaining 180 bits are moved by 30 bits (79 μsec) so that the measurement time positions are equally spaced.

That is, the first central carrier measurement point RSSI1 <1> to the seventh central carrier measurement point RSSI1 <7> shifted by 30 bits starting from the 16th bit time point from the front edge of the central portion 42. Each time point is as follows when the front edge of the central portion 42 is used as a base point.
(A) RSSI1 <1>: 0 + 16 = 16th bit (b) RSSI1 <2>: 16 + 30 = 46th bit (c) RSSI1 <3>: 46 + 30 = 76th bit (d) RSSI1 <4>: 76 + 30 = 106 Bit (e) RSSI1 <5>: 106 + 30 = 136th bit (g) RSSI1 <7>: 166 + 30 = 196th bit

In addition, the time from the front edge part of the center part 42 of each of the front edge carrier measurement point RSSI0 and the rear edge carrier measurement point RSSI2 measured at the time when any of the seven times determined as the number of measurement N is fixed is shown in FIG. As shown in FIG. 3, the following is based on the front edge of the central portion 42 as a base point.
(H) RSSI0: 0-4-4 = −8th bit (fixed)
(I) RSSI2: 196 + 16 + 4 + 4 = 220th bit (fixed)
That is, the time interval between the leading edge carrier measurement point RSSI0 and the first central carrier measurement point RSSI1 <1>, and the seventh central carrier measurement point RSSI1 <7> and the trailing edge carrier measurement point RSSI2. The time interval between the two is 24 bits (63 μsec).

  When the predetermined N times (for example, N = 7) measurement is completed, the maximum value of the received signal strength RSSI is extracted from the measurement results from the first time to the seventh time, and the maximum value is determined to be used. When it is confirmed that the link channel corresponding to the slot 40 is less than a predetermined carrier sense threshold as a threshold for determining whether or not the link channel is free, it is determined that the frequency of the link channel is free. Then, link channel allocation for allocating the frequency of the link channel is performed, and wireless communication using the frequency of the link channel is established. Here, the predetermined carrier sense threshold value may be set to, for example, an electric field strength of 44 dBμV / m.

  As described above, the time point of the central carrier measurement point RSSI1 set in the central portion 42 of the scheduled use slot 40 is not fixed to the center of the central portion 42 as shown in FIG. Depending on the measurement point RSSI1 <1> to the seventh center carrier measurement point RSSI1 <7> and the number of consecutive measurement frames, for example, 30 bits (79 μsec) on the time axis. By shifting, it is possible to reliably detect any short-time signal as long as the signal has a signal length of 79 μsec or more.

  Therefore, it is possible to reliably detect the signal of the J-DECT system 20 in which the signal length of the signal is variable to any signal length of 83.3 μsec to 368.1 μsec. Furthermore, when it is desired to detect a signal with a short signal length, the time of the center carrier measurement point RSSI1 (or the time of the leading edge carrier measurement point RSSI0 and the trailing edge carrier measurement point RSSI2 in some cases). In addition, as described above, it may be appropriately changed in accordance with the order of the number of measurement frames.

  In addition, as shown in FIG. 2 as the current technology, when carrier sense is performed at a fixed time, the center carrier measurement point RSSI1 in the center 42 is not limited to one point at the center of the center 42, for example, As in FIG. 3, if the fixed number is set to 7 at intervals of 30 bits (79 μsec), the signal of the J-DECT system 20 can be reliably detected as in FIG. However, since the carrier sense operation is changed from the three-point measurement to the nine-point measurement operation, for example, the load is increased greatly even for a PHS slave unit (PS) that is not usually high in performance. Therefore, higher processing capability is required, and it cannot be applied unless the existing PHS slave unit (PS) is modified. On the other hand, in the present embodiment shown in FIG. 3, since the mechanism for performing the three-point measurement operation similar to the existing technology is adopted as the carrier sense operation, the existing PHS slave unit (PS) is used. However, the present invention can be easily applied without changing the hardware configuration.

  Next, the carrier sense control method in the present embodiment as described above will be further described with reference to the flowchart of FIG. FIG. 4 is a flowchart for explaining an example of the flow of the carrier sense operation of the business PHS system 10 in the present embodiment shown in FIG. 1, and a specific example of the carrier sense operation shown in the schematic diagram of FIG. Is described as an example of the carrier sense control method according to the present invention.

  In the flowchart of FIG. 4, when starting the carrier sense operation, first, the number of measurements N for counting the number of consecutive measurement frames is initialized and set to ‘0’ (step S <b> 1). Further, the memory area of the maximum received signal strength RSSIxMAX for storing the maximum value among the measured RSSI values is also initialized and set to '0'. Next, the number N of times of measurement is incremented by “1”, and when it is executed for the first time, the first carrier sense number is set (step S2).

  Then, the channel of the frequency to be used is selected, and at least 2 seconds before the actual transmission operation of the signal, the front edge portion 41 and the center portion 42 of the scheduled use slot 40 corresponding to the channel to be used are selected. At the leading edge carrier measurement point RSSI0, the central carrier measurement point RSSI1, and the trailing edge carrier measurement point RSSI2 at the three points of the trailing edge 43, carrier sense is started, and the received signal strength (RSSI) at each time point Are acquired as RSSI0 (N), RSSI1 (N), and RSSI2 (N) (step S3). Here, N in RSSI 0 (N), RSSI 1 (N), and RSSI 2 (N) indicates the number of measurements N. Then, the received signal strength RSSIx (N) (where x = 0, 1, or 2) measured at each of the three carrier measurement points is sequentially stored in the memory area.

  As described above, and as indicated by “carrier measurement point RSSI1 <N>” on the right side of step S3 in FIG. 4, of the three carrier measurement points per scheduled slot 40, the leading edge carrier The time point of the measurement point RSSI0 and the trailing edge carrier measurement point RSSI2 is fixed to the time of the -8th bit and the 220th bit from the front edge part of the central part 42, respectively. Depending on the number of measurements N, starting from the 16th bit from the front edge of the central portion 42, the first central carrier measurement point RSSI1 <1> to the seventh central carrier measurement point RSSI1 <7> Each time point is a moving time point shifted by 30 bits on the time axis.

  Thereafter, the maximum received signal stored in the memory area as the absolute value (x = 0, 1, 2) of each of the measured received signal strength RSSIx (N) and the maximum value of the received signal strength RSSI measured so far. The absolute value of the intensity RSSIxMAX is compared (step S4). As a comparison result, if any of the absolute values of the measured received signal strength RSSIx (N) is equal to or less than the absolute value of the maximum received signal strength RSSIxMAX (NO in step S4), the process proceeds to step S6. .

  On the other hand, if any of the absolute values of the measured received signal strength RSSIx (N) is larger than the absolute value of the maximum received signal strength RSSIxMAX (YES in step S4), the current measurement is performed. Of the received signal strength RSSIx (N), the maximum value is overwritten and stored in the maximum received signal strength RSSIxMAX in the memory area (step S5). In the case of the first measurement, since the maximum received signal strength RSSIxMAX in the memory area is initialized to '0', the maximum value of the received signal strength RSSIx (N) measured this time is Stored as the maximum received signal strength RSSIxMAX.

  Thereafter, it is confirmed whether or not the number of times of measurement N has reached the last seventh time (step S6). If it is not the last number of times of measurement (N = 7) (NO in step S6), step S2 Returning to the process, the above-described operation is repeated. On the other hand, if the number of measurements N has reached the last number of measurements of the seventh time (N = 7) (YES in step S6), then the maximum received signal strength RSSIMAX and free channels that do not cause radio wave interference As a received signal strength value indicating that it is, it is compared with a predetermined carrier sense threshold value, for example, 44 dBμV / m (step S7).

  As a result of comparison, when the maximum received signal strength RSSIxMAX is a value larger than the carrier sense threshold value, for example, 44 dBμV / m (NO in step S7), the channel scheduled to be used is not an empty channel, The frequency is determined to be in use in another wireless communication system, and it is determined that radio wave interference may occur (step S9). Thereafter, the channel scheduled to be used is canceled and the operation shifts to a search operation for another free channel, or the current communication start operation is abandoned. On the other hand, when the maximum received signal strength RSSIxMAX is less than the carrier sense threshold value, for example, 44 dBμV / m (YES in step S7), it is determined that the channel that was scheduled to be used is an empty channel, and carrier sense is performed. The process ends (step S8). Thereafter, the assignment of the channel is confirmed and the communication operation is started.

  As described above, in the present embodiment, when any of the received signal strengths (RSSI) measured at each carrier measurement point is at a level less than the carrier sense threshold, for example, 44 dBμV / m, Is empty, and it is determined that the frequency corresponding to the channel is usable. On the other hand, if any of the received signal strengths (RSSI) measured at each carrier measurement point is at a level of the carrier sense threshold, for example, 44 dBμV / m or higher, the frequency corresponding to the channel is set to other It is determined that there is a possibility of radio wave interference in a state in use in the wireless communication system, and the use of the frequency is suppressed.

  In addition, in the above description, about center part carrier measurement point RSSI1, each time of 1st center part carrier measurement point RSSI1 <1>-7th center part carrier measurement point RSSI1 <7> is the order of the frequency | count N of measurement. Accordingly, the case where the 16th bit time point from the front edge of the central portion 42 is set as the start position and the movement time point is shifted by 30 bits (79 μsec) on the time axis is shown. However, the signal length of a signal transmitted by another wireless communication system that is not limited to the J-DECT system and may cause radio wave interference using the same frequency band is shorter than that of the J-DECT system. It is also possible to set the time interval to move on the time axis to a time interval of 30 bits (79 μsec) or less and set the number of measurements to 7 times or more in preparation for the case where it is long. It is.

  In other words, the time interval for shifting on the time axis for each measurement frame is set to an interval of 79 μsec or less, and the measurement time point at which the carrier measurement is performed in the central portion 42 (the first central carrier measurement point RSSI1 <1> to the Nth central carrier). It is also possible to set the number of measurement points RSSI1 <N>) to 7 or more and the number of measurements to be equal to or more than the number of measurement points. Furthermore, in some cases, the positions of the leading edge carrier measurement point RSSI0 and the trailing edge carrier measurement point RSSI2 may be moved as appropriate.

  In the above description of FIG. 3, the time interval between the central carrier measurement points RSSI1 from the first central carrier measurement point RSSI1 <1> to the seventh central carrier measurement point RSSI1 <7> is 30 bits ( 79 μsec), but the time interval between the leading edge carrier measurement point RSSI0 and the first central carrier measurement point RSSI1 <1>, and the seventh central carrier measurement point RSSI1 <7> and the trailing edge. The time interval between the carrier measurement point RSSI2 was 24 bits (62.5 μsec), unlike 30 bits. However, in some cases, the time interval between the leading edge carrier measurement point RSSI0 and the first central carrier measurement point RSSI1 <1>, the seventh central carrier measurement point RSSI1 <7> and the trailing edge carrier measurement point. The time intervals between all carrier measurement points including the time interval with RSSI 2 may be set to substantially the same value.

(Description of the effect of this embodiment)
As described in detail above, in the present embodiment, as the carrier measurement point, the time interval (for example, 297 μsec × 2 = 594 μsec) between the two carrier measurement points on both sides of the three-point measurement on the time axis is changed. Instead, a mechanism is adopted in which the measurement is performed a plurality of times (for example, 7 times: 79 μsec × 7 times = 553 μsec) while the carrier measurement point at the center is shifted a little each time (for example, 79 μsec) according to the order of the number of measurements. Therefore, the following effects can be achieved.

  First, in the office PHS system 10 according to this embodiment, unlike the current technology carrier sense, any radio signal having a short signal length of the J-DECT system 20 can be detected. It becomes possible to avoid the radio wave interference between the PHS system 10 and the J-DECT system 20 with certainty, and the frequency utilization efficiency can be improved.

  Secondly, in the office PHS system 10 according to the present embodiment, since any radio signal having a short signal length of the J-DECT system 20 can be detected, compared to the office PHS system in the current technology. Therefore, control and call quality can be improved.

  Thirdly, in the office PHS system 10 according to the present embodiment, a radio signal with a short signal length of the DECT system 20 is detected only by changing the carrier sense control program (software) without changing any hardware. Therefore, it is possible to cope with the problem by simply downloading the software in the existing system installation environment.

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

10 PHS system for offices 11 First PHS cordless handset (PS)
12 Second PHS cordless handset (PS)
13 Main equipment (ME)
14 PHS base station (CS)
15 area 16 overlap area 20 J-DECT system
(DECT digital cordless telephone system)
21 First DECT handset (PS)
22 Second DECT handset (PS)
23 DECT master station (CS)
25 Area 30 Outside line 40 Scheduled slot 41 Front edge 42 Central part 43 Rear edge RSSI0 Front edge carrier measurement point RSSI1 Center carrier measurement point RSSI1 <1> First center carrier measurement point RSSI1 <2> Second center Part carrier measurement point RSSI1 <3> third center part carrier measurement point RSSI1 <4> fourth center part carrier measurement point RSSI1 <5> fifth center part carrier measurement point RSSI1 <6> sixth center part carrier measurement point RSSI1 <7> 7th center part carrier measurement point RSSI2 trailing edge carrier measurement point

Claims (9)

In a TDMA narrowband digital cordless telephone system composed of a digital cordless base station and a digital cordless handset having a carrier sense function for avoiding radio wave interference with other wireless communication systems using the same frequency band,
The digital cordless base station and the digital cordless slave unit are:
For each successive measurement frame consisting of a number of frames corresponding to a predetermined number of measurements, the measurement points for the leading edge, center and trailing edge of the slot corresponding to the frequency to be used are respectively measured at the leading edge carrier measurement point. When measuring the received signal strength at each measurement point as the center carrier measurement point and the trailing edge carrier measurement point,
At the leading edge carrier measurement point and the trailing edge carrier measurement point, the received signal strength is measured the number of times measured at a fixed point on the time axis over all the measurement frames,
On the other hand, the center carrier measurement point is moved to a measurement point shifted on the time axis by a predetermined time interval for each measurement frame for the number of measurements, and the moved measurement point is The TDMA narrowband digital cordless telephone system, wherein the received signal strength is measured as a partial carrier measurement point. One of the received signal strengths measured at each of the carrier measurement points of the leading edge carrier measurement point, the center carrier measurement point, and the trailing edge carrier measurement point by performing carrier sensing for the number of times of measurement. However, if the channel to be used is at a level equal to or higher than a predetermined carrier sense threshold as a threshold for determining whether or not the channel is free, the frequency corresponding to the channel is the other radio communication system. Is in use and is determined to have the potential for radio interference,
On the other hand, if any of the received signal strengths measured at each of the carrier measurement points is at a level lower than the carrier sense threshold, the channel is in an idle state, and the frequency corresponding to the channel is used. The TDMA narrowband digital cordless telephone system according to claim 1, wherein the TDMA narrowband digital cordless telephone system is determined to be possible. When the other wireless communication system is a J-DECT (Japanese-Digital Enhanced Cordless Telecommunications) system using a 1.9 GHz band,
The central carrier measurement point is set as a time interval of 79 μsec or less as the time interval to be shifted for each measurement frame, set to a number of 7 or more as the measurement time point in the central portion, and the number of measurements as the number of measurements The TDMA narrowband digital cordless telephone system according to claim 1 or 2, wherein the number is set to a number equal to or greater than the number at the time of measurement. Carrier sense in a TDMA-type narrowband digital cordless telephone system comprising a digital cordless base station and a digital cordless slave unit having a carrier sense function for avoiding radio wave interference with other wireless communication systems using the same frequency band A control method,
The digital cordless base station and the digital cordless slave unit are:
For each successive measurement frame consisting of a number of frames corresponding to a predetermined number of measurements, the measurement points for the leading edge, center and trailing edge of the slot corresponding to the frequency to be used are respectively measured at the leading edge carrier measurement point. When measuring the received signal strength at each measurement point as the center carrier measurement point and the trailing edge carrier measurement point,
At the leading edge carrier measurement point and the trailing edge carrier measurement point, measuring the received signal strength by the number of times of measurement at a fixed time point on the time axis over all the measurement frames;
On the other hand, the center carrier measurement point is moved to a measurement point shifted on the time axis by a predetermined time interval for each measurement frame for the number of measurements, and the moved measurement point is Measuring the received signal intensity as a partial carrier measurement point. One of the received signal strengths measured at each of the carrier measurement points of the leading edge carrier measurement point, the center carrier measurement point, and the trailing edge carrier measurement point by performing carrier sensing for the number of times of measurement. However, if the channel to be used is at a level equal to or higher than a predetermined carrier sense threshold as a threshold for determining whether or not the channel is free, the frequency corresponding to the channel is the other radio communication system. Determining that there is a possibility of radio wave interference in use in
On the other hand, if any of the received signal strengths measured at each of the carrier measurement points is at a level lower than the carrier sense threshold, the channel is in an idle state, and the frequency corresponding to the channel is used. The carrier sense control method according to claim 4, further comprising a step of determining that it is possible. When the other wireless communication system is a J-DECT (Japanese-Digital Enhanced Cordless Telecommunications) system using a 1.9 GHz band,
The central carrier measurement point is set as a time interval of 79 μsec or less as the time interval to be shifted for each measurement frame, set to a number of 7 or more as the measurement time point in the central portion, and the number of measurements as the number of measurements The carrier sense control method according to claim 4 or 5, wherein the number of times is equal to or more than the number at the time of measurement. The carrier in a TDMA-type narrowband digital cordless telephone system comprising a digital cordless base station and a digital cordless handset having a carrier sense function for avoiding radio wave interference with other wireless communication systems using the same frequency band A carrier sense control program for executing sense control by a computer,
The digital cordless base station and the digital cordless slave unit are:
For each successive measurement frame consisting of a number of frames corresponding to a predetermined number of measurements, the measurement points for the leading edge, center and trailing edge of the slot corresponding to the frequency to be used are respectively measured at the leading edge carrier measurement point. When measuring the received signal strength at each time point as the center carrier measurement point and the trailing edge carrier measurement point,
In the leading edge carrier measurement point and the trailing edge carrier measurement point, a process of measuring the received signal strength by the number of times of measurement at a fixed point on the time axis over all the measurement frames;
On the other hand, the center carrier measurement point is moved to a measurement point shifted on the time axis by a predetermined time interval for each measurement frame for the number of measurements, and the moved measurement point is A carrier sense control program comprising: a process of measuring the received signal strength as a partial carrier measurement point. One of the received signal strengths measured at each of the carrier measurement points of the leading edge carrier measurement point, the center carrier measurement point, and the trailing edge carrier measurement point by performing carrier sensing for the number of times of measurement. However, if the channel to be used is at a level equal to or higher than a predetermined carrier sense threshold as a threshold for determining whether or not the channel is free, the frequency corresponding to the channel is the other radio communication system. A process of determining that there is a possibility of radio wave interference in use in
On the other hand, if any of the received signal strengths measured at each of the carrier measurement points is at a level lower than the carrier sense threshold, the channel is in an idle state, and the frequency corresponding to the channel is used. The carrier sense control program according to claim 7, further comprising: a process for determining that it is possible. When the other wireless communication system is a J-DECT (Japanese-Digital Enhanced Cordless Telecommunications) system using a 1.9 GHz band,
The central carrier measurement point is set as a time interval of 79 μsec or less as the time interval to be shifted for each measurement frame, set to a number of 7 or more as the measurement time point in the central portion, and the number of measurements as the number of measurements The carrier sense control program according to claim 7 or 8, wherein the number of times is equal to or more than the number at the time of measurement.

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