JPH03239019A - Diversity circuit in one-frequency alternate communication system - Google Patents

Abstract

PURPOSE:To improve the deterioration in communication quality due to fading, to attain alternate transmission reception and to realize the diversity effect effectively by employing an equi-gain synthesis diversity or a maximum ratio synthesis diversity for transmission/reception diversity implemented for a base station. CONSTITUTION:A base station is provided with a reception diversity means detecting a phase and a level of each reception signal received by plural antennas, matching each reception signal in a same phase, giving a prescribed weighting to the result and synthesizing the weighted signals, and a transmission diversity control means holding a phase shift angle and a weighted quantity corresponding to each antenna used at the end of a preceding reception period and sending signals from the plural antennas simultaneously at the time of transmitting to a mobile station. Thus, a highest instantaneous carrier-to-noise ratio(CNR) is ensured, the deterioration in the signal reception quality due to fading is reduced and the highest CNR is ensured for a mobile station during the transmission period of the base station.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single frequency alternating communication system for mobile communication in which signals of a single frequency are alternately transmitted and received between a base station and a mobile station. The present invention relates to a diversity circuit that achieves receive diversity and transmit diversity to improve communication quality.

[Conventional technology]

FIG. 3 is a conceptual diagram illustrating a single frequency alternating communication system for mobile communications in which signals of a single frequency are alternately transmitted and received between a base station and a mobile station.

In the figure, a base station 41 includes a plurality of (here, two) antennas 43 for both transmitting and receiving purposes for diversity, . 43□, one receiver, and one transmitter. Mobile station 4
5 is a single transmitting and receiving antenna 47 for miniaturization.
, one receiver, and one transmitter.

A signal of carrier frequency f transmitted from antenna 431 or antenna 43 of base station 41 is received by antenna 47 of mobile station 45. Further, the signal of carrier frequency f transmitted from the antenna 47 of the mobile station 45 is transmitted from the base station 4
1 antenna 43° and antenna 43□,
One of them is selected. That is, the base station 41 is configured to perform selection diversity in which a received signal from an antenna with the highest received level among a plurality of antennas is selected.

The one-frequency alternate communication method in which the base station 41 and the mobile station 45 perform bidirectional communication on a single frequency is BreathTalk communication in which transmission is performed alternately at a predetermined transmission time T, as shown in FIG. . Here, a signal from the mobile station 45 to the base station 41 is referred to as an uplink signal, and a signal from the base station 41 to the mobile station 45 is referred to as a downlink signal.

FIG. 5 is a block diagram showing the configuration of main parts of a base station and a mobile station. Note that (a) indicates a base station, and (b) indicates a mobile station.

In the figure, in the base station, a transmitter 52 to which an encoder 51 is connected and a receiver 54 to which a decoder 53 is connected include:
Antennas 58I and 58□ are connected through high frequency switches 56 and 57 whose switching is controlled by switch control circuit 55. In the mobile station, a transmitter 62 to which an encoder 61 is connected and a receiver 64 to which a decoder 63 is connected include:
An antenna 68 is connected via a high frequency switch 66 whose switching is controlled by a switch control circuit 65 .

Note that the high frequency switches 56 and 66 are switched according to the transmission/reception switching control signal, and the high frequency switch 57 is switched according to the antenna switching control signal.

Here, within the transmission time T of the uplink signal transmitted by the mobile station, the high frequency switch 66 of the mobile station is switched to the transmitter 62 side, and the high frequency switch 56 of the base station is switched to the receiver 54 side. Furthermore, within the transmission time T of the downlink signal transmitted by the base station, the high frequency switch 56 of the base station is switched to the transmitter 52 side, and the high frequency switch 66 of the mobile station is switched to the receiver 64 side.

The high frequency switch 57 of the base station also controls each antenna 58.
．． ．． The reception level of the signal received at 5B□ is switched to the higher level.

The switching operation of the high frequency switch 57 will be explained below.

FIG. 6 shows the frame structure of uplink signals and downlink signals transmitted and received within one signal section.

The signal lengths of the upstream signal and the downstream signal correspond to the transmission time T, and are composed of a preamble signal, an information signal, and a postamble signal. Note that the preamble signal and postamble signal do not include transmission information.

At the base station, the switch control circuit 55 alternately switches the high frequency switch 57 within the reception time of the preamble signal of the uplink signal, and selects the antenna with the higher reception level detected by the receiver 54. Diversity takes place.

On the other hand, since the mobile station has only one antenna, the base station performs transmission optimization to select a suitable antenna. That is, in the base station, the switch control circuit 55 alternately switches the high frequency switch 57 within the reception time i of the postamble signal of the uplink signal, detects each reception level, and selects one of the antennas with the highest level. This transmitter dyno utilizes the reversibility of the propagation path with sufficiently high correlation for the downlink signal following the uplink signal under the condition that fading fluctuations are slow, and transmits the data to the base station. A downlink signal transmitted from an antenna with a high reception level of a postamble signal of a received uplink signal is considered to have a high reception level at the mobile station.

In this manner, the base station performs receive diversity using the preamble signal of the uplink signal, and similarly performs transmit diversity for the downlink signal using the postamble signal of the uplink signal.

[Problem to be solved by the invention]

By the way, the diversity circuit described above is configured to select the one with the best reception condition from a plurality of receiving antennas during reception of a preamble signal or a postamble signal, and use it for receiving uplink signals and transmitting downlink signals. . However, in such reception diversity and transmission diversity, the antennas are fixed at least during the reception time t2 of the information signal, so in a situation where the reception level is reversed due to fading etc. during that time,
It was inevitable that the diversity effect would be reduced.

Furthermore, in receiving diversity, even if a configuration is adopted in which antennas are sequentially switched, the reception quality deteriorates significantly when antennas are switched, and the generation of switching noise is unavoidable.

The present invention provides a single frequency alternating communication system that can minimize the deterioration of reception quality while receiving an l-frame signal corresponding to the transmission time of an uplink signal or a downlink signal, and effectively bring out the diversity effect. The purpose is to provide a diversity circuit.

[Means to solve the problem]

FIG. 1 is a block diagram showing the basic configuration of the diversity circuit of the present invention.

The present invention alternately transmits and receives a single frequency signal at a predetermined period between a base station having multiple antennas for both transmitting and receiving purposes and a mobile station having one antenna for both transmitting and receiving purposes,
In a single frequency alternating communication system that performs receive diversity and transmit diversity at a base station, the base station detects the phase and level of each received signal received by multiple antennas, adjusts each received signal to the same phase, and transmits a predetermined signal. Receiving diversity means for weighting and combining, and transmission for simultaneously transmitting signals from a plurality of antennas by retaining the phase shift angle and weighting amount corresponding to each antenna used at the end of the previous reception period when transmitting to a mobile station. and diversity control means.

[For production]

In base station receive diversity, the present invention ensures the highest instantaneous received power-to-noise power ratio (CNR) by aligning the phases of each received signal received by multiple antennas and combining them with predetermined weighting. It is possible to reduce the deterioration of reception quality due to fading.

In addition, with base station transmit diversity, signals are simultaneously transmitted from multiple antennas based on the phase shift angle and weighting amount that are set immediately before switching to transmission.
During the transmission period of the base station, it is possible to ensure the highest CNR at the mobile station.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment of a base station according to the present invention.

In the figure, between a plurality of (here, two) antennas 111 and 112 for both transmitting and receiving functions and a combiner/distributor 13 that combines each received signal and distributes the transmitted signal, a Amplifier 151 .
15□ is inserted, and a phase shifter 17 for adjusting the phase of the transmitted and received signals of each antenna is further inserted in at least one of the paths.

Reception level detection circuit 19. ．． 19□ is each antenna 11
．． , 11g and selects a weighting amount (amplification factor) proportional to each reception level using a switch 211.21.
．． via each amplifier 150.15. The phase comparator 23 compares the phases of each received signal, and selects the amount of phase shift that makes them equal in phase via the changeover switch 25 to the phase shifter 17.
Set to .

A receiver 29 or a transmitter 31 is connected to the combiner/distributor 13 via a high frequency switch 27. receiver 29
The output signal of the encoder 35 is sent to the decoder 33 and the output signal of the encoder 35 is sent to the transmission 1131. Further, the output signal of the receiver 29 and the output signal of the encoder 35 are sent to the switch control circuit 37 as a transmission/reception switching control signal.

The switch control circuit 37 switches the high frequency switch 27 according to the transmission/reception switching, and also switches the selector switch 2.
11. Switch 21t and 25.

Note that the figure shows the state of the base station when receiving an uplink signal. That is, the changeover switch 211.21! The output signals of the reception level detection circuits 19I and 19z are sent to the amplifiers 15. ．． 15□
A weighting amount (amplification factor) proportional to each reception level is set in each amplifier 151.15□. The changeover switch 25 connects the output signal of the phase comparator 23 to the phase shifter 17, and selects the amount of phase shift that makes the phases of each received signal equal to the phase shifter 17.
Set to 7. Further, the high frequency switch 27 connects the combiner/distributor 13 and the receiver 29.

By the way, selection diversity is configured to select and receive the signal with the highest reception level among multiple reception signals, but even if it does not have the maximum reception level, the instantaneous reception power to noise power ratio (CNR) Since some signals have a large signal, combining all the received signals can relatively reduce the probability that the reception quality will deteriorate, making it possible to effectively bring out the diversity effect.

A feature of the present invention is that first, in reception diversity, the phases of each received signal are matched, appropriate weighting is applied, and the signals are combined.

Hereinafter, operations at the base station when receiving an uplink signal, switching between transmission and reception, and transmitting a downlink signal will be described.

When receiving an uplink signal, each reception level detection circuit 19, . 1
9□ indicates each antenna t1. , llz is detected, and the amplifier 15 . ．． 15g
control the amplification factor. Further, the phase comparator 23 controls the phase shifter 17 so that the phases of each received signal are equal to each other.The 0 combiner/distributor 13 combines the received signals that have undergone such level and phase control. This provides reception diversity.

Here, if each amplification factor of the amplifier 151.15□ is set to be independent of the received level (amplification factor 1), that is, if the amplifier and the received level detection circuit are removed, "equal gain combining diversity" is achieved, and the amplifier 15 ．． ．． 15. When each amplification factor is made proportional to the reception level, "maximum ratio combining diversity" is achieved, and the CNR of the combined reception signal can be maximized.

Next, when switching between transmission and reception, the switch control circuit 37 switches the high frequency switch 27 to the transmitter 31 side, and also switches the selector switch 21. ．． 21! , 25.

That is, the changeover switch 21. ．． 21-2 are reception level detection circuits 198 and 19, and amplifiers 15+ and 1, respectively.
5z, and the changeover switch 25 is connected to the phase comparator 23.
and the phase shifter 17 are separated. In addition, at this time, the amplifier ts
+, tsz and the phase shifter 17 retain the weighting amount (amplification factor) and degree phase shift amount that were set last when receiving the upstream signal.

Therefore, when transmitting a downlink signal, the weighting amount (amplification factor) and phase shift amount set last when receiving an uplink signal are
Transmission diversity is applied to signals transmitted from each antenna IL'Nz.

Note that, as in the past, this transmit diversity utilizes the reversibility of the propagation path where the correlation of the propagation path is sufficiently high for the downlink signal following the uplink signal under the condition that fading fluctuations are slow. . In other words, when the downlink signal is processed using the weighting amount (amplification factor) and phase shift amount set so that the GNR of the uplink signal received by the base station is maximized, the The CNR when the transmitted downlink signal is received by the mobile station is also considered to be maximum.

By the way, in conventional reception diversity and transmission diversity, a reception signal corresponding to each antenna is alternately switched during the reception period of a preamble signal and a postamble signal of an uplink signal, and one of the transmission and reception antennas is selected. However, in the method of the present invention, since the preamble signal and postamble signal for detecting the reception level used in the diversity processing are not required, almost all of the signal length T except for the part for absorbing the time lag at the time of switching between transmission and reception is eliminated. It can be used as an information signal, and transmission efficiency can be improved.

〔Effect of the invention〕

As described above, the present invention employs equal gain combining diversity or maximum ratio combining diversity in transmitting/receiving diversity performed at the base station in a system in which communication is performed alternately between a base station and a mobile station using signals of a single frequency. By using this, deterioration in communication quality due to fading can be further improved, and diversity effects can be effectively brought out in both alternate transmission and reception.

Furthermore, antenna switching is not required, and it is possible to avoid deterioration of reception quality or generation of switching noise at the time of switching.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the principle configuration of the present invention. FIG. 2 is a block diagram showing the configuration of an embodiment of a base station according to the present invention. FIG. 3 is a conceptual diagram illustrating a single frequency alternate communication system for mobile communication in which signals of a single frequency are alternately transmitted and received between a base station and a mobile station. FIG. 4 is a diagram illustrating alternate communication between a base station and a mobile station. FIG. 5 is a block diagram showing the configuration of main parts of a base station and a mobile station. FIG. 6 is a diagram showing the frame structure of uplink signals and downlink signals transmitted and received within one signal section. 11... Antenna, 13... Combiner/distributor, 15.
... Amplifier, 17... Phase shifter, 19... Reception level detection circuit, 21... Changeover switch, 23... Phase comparator, 25... Changeover switch, 27... High frequency switch, 29...Receiver, 31...Transmitter, 33...
- Decoder, 35... Encoder, 37... Switch control circuit, 41... Base station, 43... Antenna, 45...
...Mobile station, 47...Antenna, 51.61...Encoder, 52.62...Transmitter, 53.63...Decoder, 54.64...Receiver, 55.65 ...Switch control circuit, 56.57.66...High frequency switch,
58.68...Antenna. Figure 1 Figure 2 Figure 3 Figure Figure Figure (a) 1 Needle Mountain Moon 6 Figure

Claims (1)

[Claims] (1) A base station having multiple antennas for both transmission and reception,
between a mobile station that has one antenna for both transmitting and receiving,
In a single frequency alternating communication system in which a single frequency signal is alternately transmitted and received at a predetermined period and a base station performs receive diversity and transmit diversity, the base station has the following functions: a receiving diversity means for detecting the signals and levels, aligning each received signal with the same phase, applying predetermined weighting, and combining the received signals; and a phase shift angle corresponding to each antenna used at the end of the previous receiving period when transmitting to the mobile station. and retain the weighting amount,
1. A diversity circuit in a single frequency alternating communication system, comprising: transmission diversity control means for simultaneously transmitting signals from the plurality of antennas.