JP2009033472A - Radio communication terminal and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication terminal and a radio communication method with which antenna diversity excellent in real time property is performed. <P>SOLUTION: A PHS 100 includes: antennas A, B; a UW error detection part 130 capable of detecting a UW error from a TDMA frame 112 received by the present antenna A; an antenna switching control part 140 which switches the present antenna A to the other antenna B during reception of the frame when the UW error is detected by the UW error detection part 130; a signal intensity acquisition part 120 which acquires an RSSI of the frame using the present antenna A and the other antenna B before and after switching of antennas by the antenna switching control part 140 during reception of the frame; and a judgment part 150 which compares RSSIs before and after switching of the antennas with each other, makes the antenna switching control part 140 select either of the present or the other antenna to receive the next frame. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radio communication terminal and a radio communication method that perform antenna diversity by selecting one of a plurality of antennas and receiving a frame in a time-division time slot.

  2. Description of the Related Art Conventionally, wireless communication terminals such as mobile phones and PHS have so-called antenna diversity that includes a plurality of antennas and performs signal transmission / reception by selecting one of the antennas in order to improve transmission / reception sensitivity due to multipath fading or the like. It is carried out.

  For example, in Patent Document 1, a signal strength of a received signal received by each antenna is measured, a time differential coefficient of each received signal strength is obtained, and an average of each antenna at a reception time is obtained based on the above signal strength and time differential coefficient. An antenna diversity method is described in which a reception error rate is estimated and an antenna with the lowest error rate is selected.

  Further, for example, Patent Document 2 describes a method in which the antenna to be connected is switched in the rising period of the burst signal for each reception period, and the connection antenna in the reception period is determined based on reception levels before and after the switching. .

Further, Patent Document 3 discloses a technique for detecting that a unique word error detected by a mobile station antenna is caused by a re-calling type reconnection operation of the mobile station. ing. According to this technique, when it is detected that the cause of the UW error is detected, there is no waste of radio resources such as giving a channel switching operation instruction to the mobile device or securing a free channel.
JP-A-4-10724 JP 2002-368660 A JP 2000-23237 A

  However, in the antenna diversity reception methods described in Patent Document 1 and Patent Document 3, after receiving many frames, the antenna is selected by performing statistical estimation and counting the number of errors. Missing.

  Further, in the method described in Patent Document 2, since it is necessary to select and switch the antenna in an extremely short period from the rising period of the burst signal for each reception period to reception, the communication terminal must have a high processing speed. This is difficult to realize.

  In view of such a problem, the present invention provides a radio communication terminal and a radio communication method for performing antenna diversity without depending on the processing speed of the radio communication terminal, in which the timing of switching to an antenna having a good reception state is excellent in real time. The purpose is to provide.

  In order to solve the above-described problem, a typical configuration of a wireless communication terminal according to the present invention is received by a plurality of selectable antennas that receive frames in a time-divided time slot and a current antenna. A reception error detection unit capable of detecting a reception error from a frame, an antenna switching control unit that switches the current antenna to another antenna when a reception error is detected by the reception error detection unit, and an antenna switching Compare the signal strength acquisition unit that acquires the signal strength of the frame using the current antenna and other antennas before and after the antenna switching by the control unit and the signal strength before and after the antenna switching. And a determination unit that causes the antenna switching control unit to select the antenna to receive the next frame.

  According to the above configuration, when an error is detected during frame reception, the frame is used for selecting a good antenna. That is, the antennas are switched, the signal strengths of the respective antennas before and after switching are acquired, and the antennas that are considered to be in good reception are selected by comparing them. Since such antenna diversity is performed during reception of one frame, the next frame can be received by a switched antenna whose reception state is considered to be better.

  The determination unit described above may cause the antenna switching control unit to select another antenna only when the signal strength of the other antenna is larger than the signal strength of the current antenna with a difference exceeding a predetermined threshold. .

  According to such a configuration, the antenna after switching is selected only when the signal strength of the antenna after switching is larger than the signal strength of the antenna before switching with a difference exceeding a threshold. Become. Therefore, the antenna once switched after the detection of the reception error may be switched again to the original antenna.

  Thus, if the difference in signal strength between the antennas before and after switching does not exceed the threshold, it is determined that the difference is only a variation according to the acquisition timing of the signal strength, and the state of the antenna before switching is the same. As a result, the antenna before switching is continuously selected. Thereby, the antenna can be switched only when the reception state is surely deteriorated.

  The above reception error may be a unique word error (hereinafter referred to as “UW error”).

  In the present invention, based on the idea that an error rate such as a UW error is inversely proportional to a signal strength, the antenna is switched with the prediction that an error rate is low if the antenna has a high signal strength. Therefore, the antenna after switching is likely to receive the next incoming frame in a good reception state. That is, there is a low possibility that the antenna switching is wasted.

  In addition, a typical configuration of the wireless communication method according to the present invention includes a frame reception step of receiving a frame in a time-divided time slot using a current antenna among a plurality of selectable antennas, and a reception A first signal strength acquisition step of acquiring the signal strength of the received frame, a reception error detection step of detecting a reception error from the frame, and an antenna switching step of switching the current antenna to another antenna when a reception error is detected And using the other switched antennas, the second signal strength acquisition step of acquiring the signal strength of the frame is compared with the signal strengths acquired in the first and second signal strength acquisition steps, and the current or other And a determination step of selecting one of the antennas to receive the next frame.

  According to the above configuration, the antenna diversity is performed during reception of one frame, so that real-time characteristics are high.

  In the above-described determination step, the other antenna may be selected only when the signal strength of the other antenna is larger than the signal strength of the current antenna with a difference exceeding a predetermined threshold. Thereby, the antenna can be switched only when the reception state is surely deteriorated.

  The above reception error may be a unique word error. This is because, based on the idea that the error rate such as UW error and the signal strength are inversely proportional, if an antenna with a high signal strength is selected, the error rate is expected to be low. In other words, it is unlikely that antenna switching is wasted.

  According to the present invention, when an error is detected during frame reception, information is not acquired from the frame, but the antenna is switched, the signal strength of each antenna before and after switching is acquired, and the reception state is further improved. Select an antenna that is considered good. As a result, the probability that the next incoming frame can be normally received increases, the error rate can be reduced, and the number of retransmissions can also be reduced.

  Also, since antenna diversity is performed during reception of one frame, real-time performance is high.

  Furthermore, since antenna switching is not limited to the rising period of the received frame, it does not depend on the processing speed of the wireless communication terminal.

  Next, embodiments of a wireless communication terminal and a wireless communication method according to the present invention will be described in detail with reference to the accompanying drawings. In the figure, elements not directly related to the present invention are not shown. Similar elements are denoted by the same reference numerals. Note that dimensions, materials, and other specific numerical values shown in the following embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified.

(Wireless communication terminal)
FIG. 1 is a block diagram of a PHS (Personal Handy-phone System) which is an embodiment of a wireless communication terminal according to the present invention. The PHS 100 includes two selectable antennas A and B that receive a TDMA frame in a time division multiple access (TDMA) system. In addition, even if it is other than TDMA, any antenna that receives a frame in a time-divided time slot may be used. The PHS 100 intermittently receives TDMA frames through any of the selected antennas. In this embodiment, the number of antennas is only two, but three or more antennas may be provided. The antennas A and B are selected by the selector 102.

  A signal received by either one of the antennas A and B is converted to a low frequency by an LNA (Low Noise Amplifier) 104, a mixer 106, and an intermediate frequency amplifier 108, and DC converted by a DC conversion circuit 110. As a result, the voltage waveform of the signal 112 output from the DC conversion circuit 110 is smoothed as shown in FIG.

  The PHS 100 also includes a signal strength acquisition unit 120 that acquires the signal strength RSSI of the TDMA frame received by any of the antennas A and B. FIG. 2 is a timing chart showing an operation performed by the signal strength acquisition unit 120 during reception of one TDMA frame output from the DC conversion circuit 110 of FIG. FIG. 2A shows a measurement timing of RSSI (Receive Signal Strength Indicator) performed when a normal TDMA frame is received, and an antenna for measuring RSSI.

  As shown in FIG. 2A, the signal strength acquisition unit 120 is a time immediately after the signal waveform of the TDMA frame rises by the current antenna A regardless of whether or not the received TDMA frame includes a UW error. At T1, the RSSI of the TDMA frame is acquired. Thereafter, detection of a UW error is attempted, but if no UW error is detected, no RSSI acquisition or antenna switching is performed as shown in FIG.

  FIG. 2B shows RSSI measurement timing when the PHS according to the present embodiment receives a TDMA frame including a UW error, and an antenna that performs RSSI measurement. When the current antenna A is switched to another antenna B during the rise of the signal waveform, the signal strength acquisition unit 120 acquires the RSSI of the TDMA frame even at the time T2 immediately after that.

  As shown in FIG. 2 (b), when a UW error is detected during reception of a TDMA frame, the feature of this embodiment is that the RSSI is measured by switching to the antenna B as a switching candidate. That is, RSSI is acquired for different antennas at a plurality of time points during reception of one TDMA frame, and these are compared.

  The antenna switching trigger is the UW error detection unit 130 included in the PHS 100. The UW error detection unit 130 can detect a reception error (in this embodiment, a UW error) from the TDMA frame 112. A TDMA frame 112 shown in FIG. 2 includes a reference burst and a plurality of data bursts, and each burst includes a unique word (UW). The unique word is an identification code indicating that the position is the start of a burst.

  In this embodiment, based on the idea that an error rate such as a UW error is inversely proportional to RSSI, the antenna is switched based on the prediction that the error rate is low if the RSSI value is high. Therefore, the antenna after switching is likely to receive the next TDMA frame in a good reception state. That is, there is a low possibility that the antenna switching is wasted.

  The PHS 100 includes an antenna switching control unit 140, which can freely switch the antennas A and B by switching the selector 102. When a UW error is detected by the UW error detection unit 130, the antenna switching control unit 140 switches the current antenna A to another antenna B during reception of the TDMA frame.

  Further, the PHS 100 detects the signal strength at a time T1 immediately after the signal waveform of the TDMA frame rises with the current antenna A and at a time T2 immediately after the current antenna A is switched to another antenna B during the rise of the signal waveform. The RSSI detected by the detecting unit 120 is compared, and the antenna switching control unit 140 is selected at any time T3 during frame reception to determine the antenna switching control unit 140 to receive the next TDMA frame.

  According to the above configuration, when a UW error is detected during reception of a TDMA frame, the antenna is switched, the RSSIs of the respective antennas before and after the switching are acquired, and the reception state is considered to be good by comparing them. Select. Since such antenna diversity is performed during reception of one TDMA frame, an antenna that receives the next TDMA frame is switched to an antenna that is considered to have a better reception state. As described above, this embodiment can perform antenna diversity with high real-time characteristics.

  In this embodiment, the PHS 100 is used as a wireless communication terminal. However, the present invention is not limited to this, and various electronic devices such as a portable terminal such as a mobile phone and a PDA, and a household device such as a videophone may be used.

(RSSI comparison / antenna selection)
FIG. 3 is a diagram comparing RSSI values X1 and Y1 acquired by antennas A and B in FIG. In the present embodiment, the determination unit 150 selects an antenna having a larger RSSI only when there is a difference exceeding a predetermined threshold value α between the RSSI values to be compared, that is, X1 and Y1. To select.

  That is, assuming that RSSI = X1 of the antenna A, RSSI = Y1 of the antenna B, and the difference between them, the antenna B is selected when Z> α holds, and the antenna B is selected when Z ≦ α holds.

  According to such a configuration, the antenna after switching is selected only when the RSSI of the antenna B after switching is larger than the RSSI of the antenna A before switching with a difference exceeding the threshold α. It becomes. Therefore, although it is once switched to the antenna B after detecting the UW error, it may be switched again to the original antenna A.

(Threshold)
FIG. 4 is a diagram for explaining the threshold value α described in FIG. Even if the RSSI values are about the same, a slight difference occurs depending on the measurement timing (values X and Y in FIG. 4), so the threshold value α is set so as to include the difference. This threshold value α may be determined empirically.

  Thus, when the difference in RSSI between the antennas before and after switching does not exceed the threshold, it is determined that the difference is only a variation according to the RSSI acquisition timing, and the state of the antenna before switching is equivalent. The antenna before switching that has been able to perform communication until is continuously selected. Thereby, the antenna can be switched only when the reception state is surely deteriorated.

(Wireless communication method)
FIG. 5 is a flowchart showing a wireless communication method performed by the PHS of FIG. Hereinafter, the flow of the wireless communication method will be described. The PHS 100 performs a frame reception step S200 in which a TDMA frame is received by the current antenna A among a plurality of selectable antennas A and B.

  Immediately after the signal waveform of the TDMA frame rises, the signal strength acquisition unit 120 performs the first RSSI acquisition step S210 for acquiring the RSSI of the TDMA frame 112, and the UW error detection step S220 for detecting the UW error from the TDMA frame 112 This is performed by the error detection unit 130.

  In step S230, when the UW error detection unit 130 detects a UW error, the UW error detection unit 130 sends a signal to the antenna switching control unit 140, and during reception of the TDMA frame 112, the antenna switching control unit 140 An antenna switching step S240 for switching the antenna A to another antenna B is performed. On the other hand, if there is no UW error in step S230, detection of the UW error is continued until reception of the TDMA frame is completed (step S232). As shown in FIG. 2A, if no UW error is detected until the end of frame reception, the process ends without switching antennas and the like, and prepares for the reception of the next TDMA frame.

  Immediately after the antenna switching step S240 performed during the rise of the signal waveform, the signal strength acquisition unit 120 performs a second RSSI acquisition step S250 for acquiring the RSSI of the TDMA frame 112.

  Subsequently, the determination unit 150 compares the RSSI acquired in the first and second RSSI acquisition steps S210 and S250, and performs a determination step S260 of selecting any one of the antennas and receiving the next TDMA frame.

  In this determination step S260, as described above, an antenna having any RSSI is selected only when any of the RSSIs to be compared is larger than the other RSSIs with a difference exceeding a predetermined threshold value α. (Step S270). Thereby, the antenna can be switched only when the reception state is surely deteriorated.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention is applicable to a wireless communication terminal and a wireless communication method that perform antenna diversity by selecting any one of a plurality of antennas and receiving a frame in a time-divided time slot.

It is a block diagram of PHS which is embodiment of the radio | wireless communication terminal by this invention. FIG. 3 is a timing diagram illustrating an operation performed by a signal strength acquisition unit during reception of one TDMA frame output from the DC conversion circuit of FIG. 1. It is the figure which compared the value X1 and Y1 of RSSI each acquired with the antennas A and B in FIG.2 (b). It is a figure explaining the threshold value described in FIG. It is a flowchart which shows the radio | wireless communication method which PHS of FIG. 1 performs.

Explanation of symbols

100 PHS
DESCRIPTION OF SYMBOLS 110 DC conversion circuit 120 Signal strength acquisition part 130 UW error detection part 140 Antenna switching control part 150 Judgment part A, B Antenna

Claims (6)

Multiple selectable antennas that receive frames in time-divided time slots; and
A reception error detector capable of detecting a reception error from a frame received by the current antenna;
When a reception error is detected by the reception error detection unit, an antenna switching control unit that switches the current antenna to another antenna during reception of the frame;
A signal strength acquisition unit that acquires the signal strength of the frame using the current antenna and other antennas before and after antenna switching by the antenna switching control unit;
A wireless communication terminal comprising: a determination unit that compares signal strengths before and after the antenna switching, and causes the antenna switching control unit to select a current or any other antenna to receive a next frame.   The determination unit causes the antenna switching control unit to select another antenna only when the signal strength of the other antenna is larger than the signal strength of the current antenna with a difference exceeding a predetermined threshold. The wireless communication terminal according to claim 1.   The wireless communication terminal according to claim 1, wherein the reception error is a unique word error. A frame receiving step of receiving a frame in a time-divided time slot using the current antenna among a plurality of selectable antennas;
A first signal strength acquisition step of acquiring a signal strength of the received frame;
A reception error detection step of detecting a reception error from the frame;
When a reception error is detected, an antenna switching step of switching the current antenna to another antenna,
A second signal strength acquisition step of acquiring the signal strength of the frame using the other switched antenna;
A wireless communication method comprising: comparing the signal strengths acquired in the first and second signal strength acquisition steps, and selecting a current or other antenna to receive the next frame. .   The determination step includes selecting another antenna only when the signal strength of the other antenna is larger than the signal strength of the current antenna with a difference exceeding a predetermined threshold. 4. The wireless communication method according to 4.   6. The wireless communication method according to claim 4, wherein the reception error is a unique word error.

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