JP2673757B2 - TDMA communication system - Google Patents

Abstract

PURPOSE:To provide a mobile station with excellent reliability such as a temperature characteristic for the TDMA communication system. CONSTITUTION:A transmission section of a mobile station is provided with a filter ROM 21 in which a preset route roll-off characteristic is stored and a burst ROM 22 storing a prescribed Hanning function. With a digital data signal given to the filter ROM 21, a filter signal is outputted in response to the route roll-off characteristic by using the digital data signal as its address. When a burst transmission control signal representing a transmission ON/OFF is given to the burst ROM 22 and the burst transmission control signal is switched from OFF to ON or vice versa, a burst signal whose ramp period representing a leading or trailing is specified based on a Hanning function is outputted. Then the burst signal and the filter signal are multiplied by a digital multiplier 23, the product is converted into an analog signal by a D/A converter 24 and the signal is sent through a channel allocated in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDMA communication system, and more particularly to a digital cellular telephone system using the TDMA system.

[0002]

2. Description of the Related Art Generally, a digital cellular telephone system of this type includes a base station and a plurality of mobile stations (cellular telephones), and each mobile station is assigned a predetermined channel. Then, as shown in FIG. 6, upon transmission from the base station, a transmission signal is assigned to each channel and continuously transmitted, and each mobile station receives the transmission signal of the channel assigned to itself.
On the other hand, when transmitting from the mobile station to the base station, the transmission signal is allocated to the own channel and transmitted. That is, the mobile station sends out the transmission signal in bursts.

By the way, in a mobile station, when transmission is turned off, it is generally necessary to keep the leakage of the carrier signal below a preset level (for example, in the US specification, it is necessary to suppress it to below -60 dBm). .

As described above, when the leakage of the carrier signal is suppressed below a preset level, it is difficult to suppress the carrier signal by simply using the diode switch, and the insertion loss is generated in the RF band. Cannot be ignored, which causes NF deterioration and transmission power reduction.

For this reason, in recent years, a baseband processing system has been known as a system for suppressing leakage of a carrier signal when transmission is off.

Here, the baseband processing method will be outlined with reference to FIG.

The mobile station is provided with a baseband filter 11 and a burst waveform generating circuit 12 in its transmitting section. A data signal is input to the baseband filter 11 and band-processed there (hereinafter, this signal is referred to as baseband Processing signal). Then, this baseband processed signal is input to the analog switch 13. On the other hand, an ON / OFF signal is input to the burst waveform generation circuit 12, and the burst waveform generation circuit 12 generates a burst signal based on this ON / OFF signal. Then, this burst signal is given to the analog switch 13. The analog switch 13 closes when the burst signal is on, whereby the baseband processed signal is modulated by the modulator 14 and assigned to a predetermined channel by the radio unit 15 and transmitted.

[0008]

By the way, since the conventional mobile station is composed of an analog circuit as is clear from the description of FIG. 5, its characteristics change according to the temperature change, and the desired mobile station is desired. There is a problem that the performance of can not be maintained.

An object of the present invention is to provide a TDMA communication system having excellent reliability such as temperature characteristics.

[0010]

According to the present invention, there is provided a TDMA communication system comprising a base station and a plurality of mobile stations, wherein the base station and the mobile stations are connected by TDMA.
The mobile station has a first ROM in which a preset roll roll-off characteristic is stored and a second ROM in which a predetermined Hanning function is stored, in the transmission unit thereof, and the first R
A digital data signal is given to the OM and the first R
The OM outputs a filter signal according to the root roll-off characteristic using the digital data signal as an address,
A burst transmission control signal indicating transmission ON / OFF is given to the second ROM, and the second ROM rises or rises based on the Hanning function when the burst transmission control signal switches from OFF to ON or from ON to OFF, respectively. A digital multiplier that outputs a burst signal in which a ramp section indicating a fall is defined, and that further multiplies the burst signal and the filter signal to generate a multiplication signal, and a D / that converts the multiplication signal into an analog signal. And a A converter for transmitting the analog signal on a pre-allocated channel.
A communication system is obtained.

[0011]

In the present invention, since the mobile station uses the digital signal, that is, the ROM to generate the transmission signal in a burst form, it does not affect the temperature change.
You can always get the desired characteristics. Furthermore, since the rising and falling portions of the burst signal are generated using the Hanning function, the spread of the spectrum can be suppressed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Referring to FIG. 1, the digital cellular telephone system includes a base station and a plurality of mobile stations (cellular telephones). Each mobile station has a baseband filter ROM (Baseband Filter) in its transmitter.
ROM, hereinafter simply referred to as filter ROM) 21 and burst window ROM (Burst WindowRO)
M, hereinafter referred to simply as burst ROM) 22. The filter ROM 21 and the burst ROM 22 use a data signal and an on / off signal (here, a burst transmission control signal from a CPU (not shown) as an on / off signal, This burst transmission control signal is TDM
Sent in response to A) is provided in the form of a digital signal.

Based on the fundamental wave of the root roll-off impulse response shown in FIG. 2, this fundamental wave is stored in the filter ROM 21 by a bit stream of ± 4 symbols (symb).
ol), the calculation result of intersymbol interference is stored as a filter value (root roll-off characteristic) using a data signal as an address. That is, the filter ROM 21 is used as a waveform shaping ROM. On the other hand, the burst ROM 22
In order to smooth the rising and falling of the burst, that is, to smooth the rising section (here, 2 symbol section, hereinafter this section is called the ramp section) as shown in FIG. 3, a Hanning function is used. A burst signal based on the on / off signal.
Similarly, a burst signal is generated using the Hanning function also in the falling section.

As described above, the filter ROM 21 outputs the filter value to the multiplier 23 using the data signal as an address, that is, in response to the data signal. On the other hand, the burst ROM 22 sends the burst signal to the multiplier 23 based on the ON / OFF signal. As described above, this burst signal rises and falls smoothly in the rising and falling sections, respectively, that is, it is not turned on and off in a rectangular manner, so the rising and falling edges of the burst signal become sharp. Never. As a result, the spectrum does not spread in the multiplication result (hereinafter referred to as a multiplication signal) of the filter value in the multiplier 23 and the burst signal.

Specifically, the filter value is represented by an 8-bit digital value, and the Hanning function is also represented by an 8-bit digital value. The multiplier 23 multiplies the filter value by the burst signal (signed 8 bits × 8 bits) to generate a multiplication signal in burst form. The burst ROM 22 outputs "0" when the transmission is off, outputs the Hanning function in the ramp section, and outputs "1" when the transmission is on.

The multiplication signal is converted into an analog signal by the D / A converter 24 and modulated by the modulator 25, and the radio section 2
6 is assigned to a predetermined channel and transmitted.

By the way, the ramp section is generally a total of 4 on the plus side and the minus side and the rising side and the falling side.
Burst R in this ramp section
Since the Hanning function is read from the OM 22 based on the ON / OFF signal, the burst ROM 22 may be accessed in the opposite direction on the falling side, so that the rising and falling Hanning functions can be shared. Further, as shown in FIG. 4, if the burst window function is positive, the sign is held in the filter ROM 21, so it is sufficient to consider only the plus side.

The ramp section can be arbitrarily set by changing the data in the burst ROM 22. That is, an arbitrary ramp waveform can be realized. Furthermore, since waveform shaping and burst signal generation are performed using different ROMs, the data in the ROMs can be changed independently.

[0020]

As described above, according to the present invention, a mobile station uses a digital signal, that is, a ROM to generate a transmission signal in a burst form. You can always get the desired characteristics. Furthermore, since the rising and falling portions of the burst signal are generated using the Hanning function, there is an effect that the spread of the spectrum can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing an embodiment of a transmitter of a mobile station used in a TDMA communication system according to the present invention.

FIG. 2 is a diagram for explaining a fundamental wave of a root roll-off impulse response.

FIG. 3 is a diagram showing a rise of a burst signal generated by using a Hanning function in the burst ROM shown in FIG.

FIG. 4 is a diagram for explaining an output from the multiplier shown in FIG.

FIG. 5 is a block diagram schematically showing an example of a transmitter of a mobile station used in a conventional TDMA communication system.

FIG. 6 is a diagram for explaining an outline of a TDMA communication system.

[Explanation of symbols]

 11 Baseband Filter 12 Burst Waveform Generation Circuit 13 Analog Switch 14 Modulator 15 Radio Unit 21 Baseband Filter ROM 22 Burst Window ROM 23 Multiplier 24 D / A Converter 25 Modulator 26 Radio Unit

Claims (1)

(57) [Claims] 1. In a TDMA communication system comprising a base station and a plurality of mobile stations, wherein the base station and the mobile station are TDMA-connected, the mobile station has a root roll-off preset in its transmission unit. First RO with stored characteristics
M and a second ROM in which a predetermined Hanning function is stored, a digital data signal is given to the first ROM, and the first ROM uses the digital data signal as an address for the root roll. A filter signal is output according to the off characteristic, and a burst transmission control signal indicating transmission on / off is given to the second ROM, and the second R
The OM outputs a burst signal in which a ramp section indicating a rising edge or a falling edge is defined based on the Hanning function when the burst transmission control signal is switched from off to on or from on to off. A digital multiplier that multiplies the filter signal to generate a multiplication signal and a D / A converter that converts the multiplication signal into an analog signal are provided, and the analog signal is transmitted on a pre-allocated channel. A TDMA communication system characterized by the above.