JP2836204B2 - Bit synchronization method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile telephone system employing a TDMA system, and more particularly to a bit synchronization system in a base station.

[Conventional technology]

Conventionally, in this type of mobile telephone system, a receiving unit of a base station has a random access channel as a control channel.
When a single burst transmission from a mobile station is received on a channel, bit synchronization is achieved by utilizing the fact that a preamble pattern for bit synchronization is provided at the beginning of the burst. However, when bursts from the same mobile station are received periodically and continuously as in the case of a communication channel, it is useless to precede the preamble pattern every time, so that no preamble pattern is used. For this reason, the first few bursts until the synchronization is achieved are used only for obtaining the bit synchronization from the data without giving up the decoding of the contents, and these first few bursts are invalid bursts. .

Although the mobile station transmits in synchronization with the downlink signal from the base station, the receiving unit of the base station must obtain the bit synchronization information from the received signal instead of from the transmission timing information. This is because the distance from to the mobile station is not constant, and the propagation delay time due to this distance differs for each mobile station.

[Problems to be solved by the invention]

In order to enable the base station to receive the first few bursts in the communication channel without wasting the first burst, the receiving unit for the random access channel of the base station receives a call signal from a mobile station, for example. Bit synchronization information may be stored, and when the mobile station is assigned a communication channel, the stored bit synchronization information may be used.

However, there are the following problems to realize this. The first is that the call control is not a function originally provided in the transmission / reception circuit but a function of a station higher than the base station, for example, an exchange. For this reason, the function of storing and managing the number of the mobile station in the base station and identifying the communication channel assigned to the mobile station is a completely additional function, and greatly increases the complexity of the base station. . Second, it is good if the random access channel and the assigned traffic channel are different time slots of the same carrier, but if they are different carriers, the random access channel receiver and the traffic channel receiver are the same. Since it is a separate circuit even within the base station, a connection for bit synchronization information transfer between the receiving units is required.

An object of the present invention is to provide a bit synchronization system that prevents occurrence of invalid burst in a traffic channel receiving unit.

[Means for solving the problem]

In the bit synchronization system of the present invention, the random access channel receiving unit of the base station has a function of reporting the bit synchronization timing information used for decoding together with the decoded data to the upper station, and the upper station is notified of the information. When the data is data requesting the assignment of a communication channel, a communication channel number is specified to the mobile station, and a command signal and a bit synchronization timing information signal for starting communication are transmitted to the corresponding communication channel receiving section of the base station. The communication channel receiver of the base station has a function of receiving a transmission burst from the mobile station using the bit synchronization timing information sent from the upper station as an initial value.

For example, in the random access channel receiving section,
A bit synchronization section for shifting the phase of the clock generated from the clock oscillation section of the base station; and a transfer circuit for reporting the clock from the bit synchronization section to the upper station together with the decoded data. And a bit synchronization unit for presetting the bit synchronization timing information signal and outputting a decoding clock.

[Action]

According to the present invention, since the bit synchronization timing information found in the random access channel is transmitted to the speech channel via the higher-level station and used, it is possible to perform synchronous reception at the same time as reception in the speech channel. To prevent the occurrence of

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.
1 indicates a base station, 2 indicates a mobile station, and 3 indicates an upper station.

In the base station 1, portions not related to the present invention, such as a transmission unit, are omitted. This base station 1 has one carrier for a random access channel and two carriers for a speech channel. In the TDMA system, there are a plurality of time slots per carrier. For example, in the case of three multiplexing, one communication path, that is, a channel is formed for every third time slot. Therefore, the configuration of one channel per carrier is shown.

The random access channel receiving unit 10 includes a demodulating unit 11
And a sampling unit 12 for sampling demodulated data.
And a bit synchronization unit 13 for outputting a clock signal at the time of the sampling, a decoding unit 1 for decoding the sampled data, and a transfer circuit for transferring the decoded signal to the upper station 3.
It is composed of 15 and.

Further, the traffic channel receiving unit 20 includes a demodulation unit 21, a sampling unit 22, a bit synchronization unit 23, and a decoding unit 24,
Further, it comprises a command receiving unit 25 for receiving a command from the upper station 25.

 The communication channel 30 is similarly configured.

Further, the base station 1 is provided with a clock oscillator 40.

In such a configuration, the random access channel receiving section 10 suddenly receives a burst signal from the mobile station 2. In this case, the signal is received at a substantially fixed timing, but there is a timing shift inside and outside one bit due to a difference in propagation delay time. Therefore, the sampling timing for demodulating this signal matches the frequency of the clock of the clock oscillating unit 40 in the base station 1 but does not always match the phase.

Therefore, the bit synchronization unit 13 of the random access channel receiving unit 10 checks this phase difference during the period when the preamble pattern placed at the head of the burst from the mobile station 2 is being received, and the clock oscillation unit 40 The clock is a phase shift (phase shift) and is used as a clock at the optimum sampling timing. For this reason, the part which should be transmitted as information after the preamble pattern can be sampled and decoded at the correct timing.

Further, the random access channel receiving unit 10
Reports the phase difference information of the bit synchronization unit 13 to the upper station 3 through the transfer circuit 15 together with the decoded data.

The upper station 3 decodes the signal from the notified mobile station 2,
If the signal requires a call channel, such as an outgoing call signal, one of the vacant call channels is selected and transmitted to the mobile station 2 through a random access channel transmission unit (not shown). In addition to notifying the channel number, the operation start command is sent to the corresponding communication channel of the base station 1, for example, the command receiver 25 of the communication channel receiver 20.

At this time, the phase difference information in the bit synchronization circuit 13 when received by the random access channel receiving unit 10 is also transmitted to the traffic channel receiving unit 20 together. For this reason, the communication channel receiving unit 20 starts the receiving operation when receiving the operation start command from the upper station 3. At this time, the bit synchronization unit 23 can preset the initial value of the phase shift amount. 3 from the bit synchronization section.
After setting to 23, the receiving operation is started. Therefore,
The traffic channel receiving unit 20 can receive a signal from the head of the first burst of the signal from the mobile station 2 at a correct phase shift amount, that is, at an optimum sampling timing, and can perform a correct decoding.

Note that the reason that the correct phase shift amount in the random access channel is the same as the correct phase shift amount in the speech channel is a signal from the same mobile station. It can be considered that the mobile station is sufficiently stable in time, and that the mobile station does not move as the propagation delay time greatly changes in a short time.

Here, the present invention can be similarly applied to the case of multi-level modulation of three or more values.

〔The invention's effect〕

As described above, the present invention relates to a communication system in which bit synchronization timing found in a random access channel is transmitted to a higher station based on a transmission burst from a mobile station, and the higher station receives the bit synchronization timing information. Since the signal is transmitted to the channel, it is possible to perform synchronous reception at the same time as reception on the communication channel for reception, and it is possible to avoid a head loss of a transmission burst from the mobile station and to prevent an invalid burst from being generated. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing the bit synchronization system of the present invention. DESCRIPTION OF SYMBOLS 1 ... Base station, 2 ... Mobile station, 3 ... Upper station, 10 ... Random access channel receiver, 20, 30 ... Communication channel receiver, 40 ... Clock oscillator, 11 ... Demodulation Department,
12 sampling section, 13 bit synchronization section, 14 decoding section, 15 transfer circuit, 21 demodulation section, 22 sampling section, 23 bit synchronization section, 24 decoding section, 25 Command receiving part.

Claims (2)

(57) [Claims] 1. A TDMA mobile telephone system having a random access channel and a communication channel, wherein a transmission burst of a mobile station on the random access channel is preceded by a preamble pattern for bit synchronization. In a system that uses a signal format in which a preamble pattern for bit synchronization is not prepended to the transmission burst of the transmission channel, the random access channel receiving unit of the base station stores the bit synchronization timing information used for decoding together with the decoded data. When the reported data is data requesting the assignment of a communication channel, the upper station specifies the communication channel number to the mobile station and receives the corresponding communication channel from the base station. Signal and bit synchronization timing to start communication It has a function of transmitting an information signal, and the communication channel receiver of the base station has a function of receiving a transmission burst from the mobile station using the bit synchronization timing information transmitted from the upper station as an initial value. Bit synchronization method. 2. A random access channel receiving unit, comprising: a bit synchronizing unit for shifting a phase of a clock generated from a clock oscillating unit of a base station; and a clock from the bit synchronizing unit reported to a higher-level station together with decoded data. A communication channel receiving unit, a command receiving unit for receiving a reception start command signal and bit synchronization timing information from an upper station, and a bit for presetting a bit synchronization timing information signal and outputting a decoding clock. 2. The bit synchronization system according to claim 1, further comprising a synchronization unit.