JP3870010B2 - Mobile station equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile station apparatus, and more particularly to a mobile station apparatus of a mobile communication system in which a plurality of mobile station apparatuses are connected to each other by a TDMA system via base stations of each cell.
[0002]
[Prior art]
FIG. 6 is a diagram for explaining the prior art, and shows a partial configuration of a cellular mobile communication system. In the figure, a wireless service area is divided into a plurality of zones (cells), and a base station BS1 is provided in the zone Z1, and a base station BS2 is provided in the zone Z2, and these base stations BS1, BS2 and the like are mobile units. It is connected to the public network via the switching center MCU. Further, the mobile station MS1 located in the zone Z1 is connected to the base station BS1 at the frequency f1, and the mobile station MS2 located in the zone Z2 is connected to the base station BS2 at the frequency f2. Under the cellular system, for example, as stipulated in the digital mobile phone system standard, frequency allocation is performed at least 50 kHz apart between adjacent cells, and the frequency is separated by at least twice the adjacent channel interval (25 kHz). Therefore, there is usually no interference between channels.
[0003]
[Problems to be solved by the invention]
However, in practice, there are cases where a plurality of operators operate a mobile communication system in the same service area. For this reason, it is becoming difficult to secure a frequency arrangement interval between zones. In addition, even if the frequency allocation interval between adjacent zones is observed, the radio wave propagation environment (ie, the shape of the service zone) changes substantially due to the influence of surrounding terrain, fading or urban structures, etc. As shown in the drawing, the radio wave fn (zone adjacent to f2, ie, | fn−f2 | = 25 kHz) from the zone Zn that is not adjacent to the zone Z2 is received by the mobile station MS2, and the call quality is significantly degraded. There is a case.
[0004]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a mobile station apparatus capable of maintaining good communication quality regardless of changes in the channel (frequency) environment during communication. There is.
[0005]
[Means for Solving the Problems]
The above problem is solved, for example, by the configuration of FIG. That is, the mobile station apparatus (MS2) of the present invention (1) is configured such that the mobile station apparatus connected to the base station that communicates with the mobile station by the TDMA method through a plurality of communication channels having different frequencies Measuring means for measuring a reception level (for example, RSSI) of a signal having a frequency adjacent to a frequency (for example, f2) of a channel during communication at a slot timing other than the communication slot reception timing (for example, T2), and the measured reception level is a predetermined threshold value If (TH) is exceeded, a transmission means for transmitting a call channel switching request to the base station is provided. Therefore, it is possible to quickly detect a radio wave interference state during a call and to quickly avoid deterioration in call quality. Further, by using the slot timing, the control becomes easy and reliable.
[0006]
Further, the above problem is solved by the configuration of FIG. That is, the mobile station apparatus (MS2) of the present invention (2) is adjacent to the frequency (f2 ′) of the standby channel at a timing other than the standby slot reception timing when the mobile station apparatus of the present invention is in the standby state. Measuring means for measuring a reception level of a signal having a frequency to be transmitted, and control means for shifting to a search mode for a perch channel when the measured reception level exceeds a predetermined threshold (TH). Therefore, it is possible to quickly detect a radio wave interference state during standby, and to quickly avoid deterioration (instability) of standby reception quality.
[0007]
The mobile station apparatus of the present invention (3) is a mobile station apparatus in a mobile communication system having a function of transmitting a signal for requesting a change of a call channel from a channel during a call to a channel of another frequency to a base station. Measuring means for measuring a signal level of a signal having a frequency adjacent to the frequency of the designated call channel between the designation of the call channel by the base station and the actual start of the call, and the measured reception level is And a transmission means for transmitting a signal for requesting the change of the call channel when exceeding a predetermined level. Accordingly, it is possible to quickly detect the radio wave interference state from the designation of the call channel by the base station to the actual start of the call, and to avoid starting the call in a poor state.
The mobile station apparatus of the present invention (4) is a mobile station of a mobile communication system in which the base station switches the mobile station to another frequency channel when the reception level reported from the connected mobile station is below a predetermined level. In the apparatus, at the time of a call, a measuring means for measuring a reception level of a signal having a frequency adjacent to the frequency of the channel during the call at a timing other than the reception timing of the call slot, and the local station when the measured reception level exceeds a predetermined level. And a transmission means for reporting the reception level measurement result lower than actual. Therefore, the channel switching request can be promoted.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.
[0009]
FIG. 1 is a block diagram of a mobile station apparatus according to an embodiment. In the figure, 31 is an antenna, 32 is a transmission / reception branching switch, 33 is a low noise amplifier (LNA) for amplifying a received RF signal, 34 is a frequency synthesizer, 35 Is a mixer that converts the frequency of the received RF signal into an IF signal, 36 is a bandpass filter (BPF) that extracts an IF signal of the required bandwidth, and 37 is amplifying the extracted IF signal to a required level and receiving level (received electrolysis). (Intensity) IF amplifier (IFA) capable of detecting RSSI, 38 is, for example, a demodulator (DEM) by (π / 4) shift QPSK, 39 is a modulator (MOD) by (π / 4) shift QPSK, and 40 is a transmitter , 41 is a TDMA synchronization control unit that mediates exchange of call control signals and voice data signals in accordance with a TDMA system with a base station (not shown). A codec (CODEC) that performs code conversion of transmission / reception signals, 43 is a baseband processing unit that processes audio band signals, 44 is a speaker (SPK), 45 is a microphone (MIC), and 46 is an A / D converter. .
[0010]
Further, 51 is a CPU that performs main control and call processing of the apparatus, 52 is a memory (MEM) that stores programs executed by the CPU 51 and necessary operation data, and 53 is a console (on the front of the apparatus). CSL) and 54 are liquid crystal display units (DSP), 55 is a keyboard (KBD) having dial keys and function keys, and 56 is a common bus for the CPU 51.
[0011]
The CPU 51 can start various application programs described later by various timing signals (call slot, standby slot, etc.) from the TDMA synchronization control unit 41.
[0012]
In addition, the configuration including the IF amplifier 37 and the A / D converter 46 is under the control of the CPU 51 during the call of this apparatus, during standby, or from the designation of the call channel by the base station to the start of the call. This corresponds to measurement means for measuring the reception level of a signal having a frequency adjacent to the channel used by the own station. Further, when the measured reception level exceeds a predetermined threshold, the transmission means for transmitting a call channel switching request to the base station is under the control of the CPU 51, the modulation unit 39 for transmitting the call channel switching request, A configuration including the transmission unit 40 and the like is equivalent. Further, when the measured reception level exceeds a predetermined threshold, the CPU 51 corresponds to the control means for shifting to the perch channel search mode. Hereinafter, the operation of the mobile station apparatus according to the present embodiment will be described.
[0013]
With the above configuration, when the apparatus is powered on, the CPU 51 first searches for a plurality of perch channels, connects to the nearest (best communication quality) base station, and receives information for standby reception of the own station from the base station ( A standby reception frame number, standby reception slot number, etc.) are received, and a standby state is entered.
[0014]
Thereafter, when a call from the own station or an incoming call from another station is accepted, the call channel is designated by the base station to connect the call, and at the time of the call, the received RF from the antenna 31 is connected. The signal is demodulated into reception data RD by the reception system, converted to a PCM code signal by the codec 42, further converted to an analog signal by the baseband processing unit 43, and output to the speaker 44. The audio signal from the microphone 45 is converted into a PCM code signal by the baseband processing unit 43, converted to transmission data TD by the codec 42, further modulated into a transmission RF signal by the transmission system, and transmitted from the antenna 31.
[0015]
However, if there is radio wave interference from an adjacent channel during this call, the call quality will deteriorate, and in the worst case, the call may be disconnected. Therefore, in this embodiment, in order to effectively avoid such a state, the following channel monitoring control during call is performed.
[0016]
FIG. 2 is a flowchart of channel monitoring control during a call according to the embodiment.
A timing chart corresponding to this is shown in FIG. FIG. 2A shows a non-call slot 1 interrupt process. When the timing of the non-call slot (for example, slot 1) of the own station comes, an interrupt is input to this process. In step S11, the CPU 51 offsets the reception frequency of the synthesizer 34 to the busy channel (f2) -25 kHz. In other words, the reception frequency is switched to the channel adjacent to the busy channel. In step S12, the reception level RSSI at that time is detected, and in the subsequent step S13, it is determined whether or not the detected reception level RSSI is greater than a predetermined threshold value TH (for example, 1 dB). If RSSI> TH, there is a possibility that this busy channel is in a radio wave interference state due to the adjacent channel, so the process proceeds to step S14, where 1 is set in the channel up switching request flag. If RSSI> TH is not satisfied, the process of step S14 is skipped. In step S15, the frequency of the synthesizer 34 is returned to the busy channel (f2), and the process is exited.
[0017]
This channel up switching request flag = 1 is immediately notified to the connected base station via the control channel CC, and the base station receiving it searches for a free channel with a frequency higher than the busy channel f2 and exists. When doing so, the vacant channel is assigned to the mobile station MS2, and the busy channel is quickly switched. Therefore, a radio wave interference state at a low frequency can be efficiently avoided.
[0018]
FIG. 2B shows a non-call slot 2 interrupt process. When the timing of another non-call slot (for example, slot 3) of the own station comes, an interrupt is input to this process. In step S21, the CPU 51 offsets the reception frequency of the synthesizer 34 to the busy channel (f2) +25 kHz. In other words, the reception frequency is switched to the channel adjacent to the busy channel. In step S22, the reception level RSSI at that time is detected, and in the subsequent step S23, it is determined whether or not the detected reception level RSSI is greater than a predetermined threshold value TH (for example, 1 dB). If RSSI> TH, there is a possibility that this busy channel is in a radio wave interference state due to an adjacent channel, so the process proceeds to step S24, where 1 is set in the channel down switching request flag. If RSSI> TH is not satisfied, the process of step S24 is skipped. In step S25, the frequency of the synthesizer 34 is returned to the busy channel (f2), and the process exits.
[0019]
This channel down switching request flag = 1 is immediately notified to the connected base station via the control channel CC, and the base station receiving it searches for an empty channel having a frequency lower than the busy channel f2 and exists. When doing so, the vacant channel is assigned to the mobile station MS2, and the busy channel is quickly switched. Therefore, a radio wave interference state at a high frequency can be efficiently avoided.
[0020]
In the above embodiment, the case where the channel up / down switching request is directly notified to the base station has been described. However, the present invention is not limited to this. In addition, an existing communication method with the base station during a call can be used effectively. That is, for example, by reporting the reception level measurement result of the own station during a call lower than the actual one, the channel switching request can be promoted. In this case, it can be switched to any free channel.
[0021]
FIG. 3 is a flowchart of the standby channel monitoring control according to the embodiment. FIG. 5 shows a timing chart corresponding to this. In FIG. 5, one superframe of this standby channel is composed of 36 consecutive frame signals, and one frame is composed of three slot signals. Each slot signal includes a leading preamble signal, a subsequent data signal, an intermediate synchronization word signal, and a subsequent data signal. The mobile station MS2 receives the designation of the standby reception frame number and standby reception slot number of the own station from the base station and is in a standby state while maintaining this reception synchronization.
[0022]
Returning to FIG. 3, this figure shows a standby interrupt process. When a timing other than a predetermined standby slot of the own station comes, an interrupt is input to this process. This timing can be arbitrarily set by the CPU 51 in a section other than the standby slot. In step S31, the CPU 51 offsets the reception frequency of the synthesizer 34 to the waiting channel (f2 ′) − 25 kHz. In step S32, the reception level RSSI at that time is detected, and in the subsequent step S33, it is determined whether or not the detected reception level RSSI is greater than a predetermined threshold value TH (for example, 1 dB). If RSSI> TH, there is a possibility that this standby channel is in a radio wave interference state, so the process proceeds to step S37.
[0023]
If RSSI> TH is not satisfied, the CPU 51 further offsets the reception frequency of the synthesizer 34 to the standby channel (f2 ′) + 25 kHz in step S34. In step S35, the reception level RSSI at that time is detected, and in the subsequent step S36, it is determined whether or not the detected reception level RSSI is greater than a predetermined threshold value TH (for example, 1 dB). If RSSI> TH is not satisfied, the frequency of the synthesizer 34 is returned to the waiting channel (f2 ′) in step S38, and the process is exited.
[0024]
If it is determined in step S33 or step S36 that RSSI> TH, the standby channel may be in a radio wave interference state, so the process proceeds to step S37, where the CPU 51 sets 1 in the perch channel switching request flag. set. In step S38, the CPU 51 returns the frequency of the synthesizer 34 to the waiting channel (f2 ') and exits this process.
[0025]
This perch channel switching request flag = 1 activates the perch channel search process in the apparatus, thereby entering a new perch channel search mode.
[0026]
In addition, although channel monitoring control in which the present apparatus is in a call and in standby has been described, the present invention is not limited to this. For example, during the period from the designation of the call channel by the base station to the actual start of the call, the possibility of radio wave interference by the adjacent channel can be monitored by the same control as in FIG. 2 or FIG. When the predetermined threshold is exceeded, it is possible to prevent the start of a call in a poor state by requesting the base station to change the call channel.
[0027]
Moreover, although the said embodiment was demonstrated with the specific numerical example, this invention is not limited to these numerical values. For example, the offset frequency for detecting radio wave interference may be ± 12 kHz.
[0028]
Further, although the preferred embodiment of the present invention has been described, it goes without saying that various changes in the configuration, control, processing, and combination of each part can be made without departing from the spirit of the present invention.
[0029]
【The invention's effect】
As described above, according to the present invention, it is possible to maintain good communication quality regardless of changes in the channel environment during communication, and thus greatly contribute to improvement of service and reliability of the mobile communication system.
[Brief description of the drawings]
FIG. 1 is a block diagram of a mobile station apparatus according to an embodiment.
FIG. 2 is a flowchart of channel monitoring control during a call according to the embodiment.
FIG. 3 is a flowchart of standby channel monitoring control according to the embodiment;
FIG. 4 is a timing chart of channel monitoring control during a call according to the embodiment.
FIG. 5 is a timing chart of standby channel monitoring control according to the embodiment;
FIG. 6 is a diagram illustrating a conventional technique.
[Explanation of symbols]
BS Base station MS Mobile station MCU Mobile switching center

Claims (4)

In a mobile station apparatus connected to a base station that communicates with a mobile station by a TDMA scheme through a plurality of communication channels having different frequencies ,
A measuring means for measuring a reception level of a signal having a frequency adjacent to a frequency of a channel during a call at a slot timing other than the call slot reception timing of the local station during a call;
A mobile station apparatus comprising: a transmission unit configured to transmit a call channel switching request to a base station when the measured reception level exceeds a predetermined threshold. In a mobile station apparatus connected to a base station that communicates with a mobile station by a TDMA scheme through a plurality of communication channels having different frequencies ,
Measuring means for measuring the reception level of the signal of the frequency adjacent to the frequency of the channel that is waiting at a timing other than the reception timing of the standby slot when waiting for the own station;
A mobile station apparatus comprising: control means for shifting to a perch channel search mode when the measured reception level exceeds a predetermined threshold value. In a mobile station apparatus in a mobile communication system, having a function of transmitting a signal requesting a change of a call channel from a channel during a call to a channel of another frequency to a base station,
Measuring means for measuring a signal level of a signal having a frequency adjacent to the frequency of the designated call channel between the designation of the call channel by the base station and the actual start of the call;
A mobile station apparatus comprising: a transmission unit configured to transmit a signal requesting the change of the communication channel when the measured reception level exceeds a predetermined level. In the mobile station apparatus of the mobile communication system, the base station switches the mobile station to another frequency channel when the reception level reported from the connected mobile station is below a predetermined level.
A measuring means for measuring a reception level of a signal having a frequency adjacent to a frequency of a channel during a call at a timing other than a call slot reception timing during a call;
A mobile station apparatus comprising: transmission means for reporting a reception level measurement result of the own station lower than actual when the measured reception level exceeds a predetermined level.

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