JPH02312417A - Radio channel quality supervisory system - Google Patents

Abstract

PURPOSE:To prevent an error from being generated at the time of calculating the radio channel quality by dividing one slot section into plural small sections, and providing a means for detecting the reliability of a receiving bit, and a means for measuring an envelope level of a receiving signal on each separate small section. CONSTITUTION:A information part is divided, for instance, into three small sections Info1, Info2 and Info3, a parity check bit Ch is added to each of them, this parity inspection is executed by an error detecting circuit 2, and its result is outputted. In accordance with a timing circuit 4, a counter input is controlled by a selecting circuit 5, and a result of detection is summed up in each separate small section in one slot. On the other hand, an envelope detecting circuit 9 is brought to sampling by synchronizing with a reproducing clock by a sample holding circuit 10, and an average receiving envelope level is derived by an averaging circuit 11. In such a way, the quality can be measured with high accuracy, and also, so as to be faithful to the quality sensed by a user.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is applicable to mobile communications with a small zone configuration, where interference waves exist, and each channel is assigned a time slot using TDMA. This relates to a method for monitoring the communication quality of a wireless channel in digital wireless communication.

[Conventional technology]

Conventionally, as an interference detection method for mobile communication, there is a method of detecting the size of a beat at an envelope level.

The principle of this method is that a beat corresponding to the difference in carrier frequency between the desired wave and the interference wave occurs at the envelope level of the received signal, and the size of the beat component is proportional to the ratio of the desired wave to the interference wave. This is what was used.

Among these conventional methods, in a method using a constant envelope modulation method such as FSX, fluctuations in the reception envelope level are caused by two factors, one is due to 7-lossing peculiar to the mobile communication propagation path, and the other is due to interference.

The pitch fluctuation due to the former is several hundred Hz at the most (when the carrier frequency is about IGHz and the mobile station's moving speed is 1100 km/h)
The pitch fluctuation due to the latter is usually 1 to 2 kHz or more depending on the frequency deviation, etc., since the contents of the modulated signals of the low wave and the desired wave are different, and the fluctuation pitch due to the latter is usually 1 to 2 kHz or more, and the frequency of both is different. By processing the envelope level output with a band-pass filter, it is theoretically possible to remove the influence of the 7A song, extract only the beat component due to interference, and obtain the amount of interference.

Furthermore, if a low-pass filter is used, it is also possible to extract only the fluctuations due to aging.

[Problem to be solved by the invention]

In the conventional interference detection method for mobile communication as described above, since the 5 cpc method is used in normal mobile communication, a reception IF filter is provided for each channel in order to remove the spectrum of the adjacent channel, but the bandwidth of the filter is However, if the signal is not large enough to pass the modulated spectrum components, part of the signal will be canceled by the filter and distortion will occur. Therefore, the envelope level after passing through the reception IF filter will fluctuate, and if the frequency of the modulated signal is relatively small, the speed of fluctuation of the envelope will be small.
This method has the drawback of causing a large error in detecting the amount of interference.

This is because the variation speed of the envelope becomes small, making it difficult to distinguish it from the variation due to 7-aging. In particular, when the carrier frequency drifts and there is a difference between the center frequency of the receive IF filter and the desired wave's F frequency, the amount of signal components removed by the filter increases and distortion increases, resulting in this error. It had the disadvantage of being very large.

Furthermore, when a modulation method that does not have a constant envelope, such as QPSK, is adopted, the envelope level varies depending on the modulated signal, so on the receiving side, the above-mentioned propagation path condition, that is, 7 aging and Variations specific to the modulated signal are superimposed on variations in the envelope level due to interference, making it difficult to extract only the bit component due to interference, and also having the disadvantage that errors are also greatly reduced.

Furthermore, as another method, error detection is performed using error detection codes such as BCH codes or detection of destruction of encoding rules of transmission line codes such as Manchester codes, and even if the reception envelope level is sufficient, First, a method has been considered in which the amount of interference is calculated by determining that there is interference when an error is detected.

In wireless communication using the TDMA system, communication is performed using slots assigned to each channel.

Due to the limits of slot synchronization accuracy between stations and the propagation time difference, the slot timing of the interference wave generally deviates from the timing of the desired wave, and interference with the slot of the desired channel is due to the carrier of the interference wave. Depending on the usage status of each slot and the size of slot timing deviation,
There are various cases in which only a part of the slot is affected by the interference wave, and there are cases in which the entire slot is affected by the interference wave.

Generally, on average, even if the code error rate is the same, the quality of the line depends on the temporal distribution of the errors, so in the case of TDMA mentioned above, errors are concentrated in a part of the slot. Since there are cases where the radio channel quality is distributed and cases where it is dispersed throughout, there is a drawback that an error occurs in the calculation of the radio channel quality.

In view of these conventional problems, it is an object of the present invention to provide a wireless channel quality monitoring method that can be applied to a wireless communication system using TDMA and can accurately detect quality deterioration due to interference or the like.

[Means to solve the problem]

According to the present invention, the above object is achieved by the means described in the claims.

That is, in wireless communication for transmitting digital signals, the present invention divides one slot interval into a plurality of small intervals,
A means for detecting the reliability of received bits for each sub-interval and a means for measuring the envelope level of the received signal is provided, and the wireless This is a wireless channel quality monitoring method that determines channel quality.

[For production]

The main feature of the present invention is to detect pit errors in each small section of one slot section of the TDMA system.

That is, the present invention is applied to a wireless communication system using TDMA, and even if there is interference in a part of a slot, it can be detected, and the error distribution in the slot and the wireless channel quality can be measured. becomes possible.

Hereinafter, a detailed explanation will be given based on an example.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention, in which 1 is a detection circuit, 2 is an error detection circuit, 3 is a frame synchronization signal detection and clock recovery circuit (hereinafter simply referred to as a clock recovery circuit), Reference numeral 4 represents a timing circuit, 5 a selection circuit, 6 to 8 counters, 9 an envelope detection circuit, 1o a sample hold circuit or A/D conversion circuit, 11 an averaging circuit, and 12 a determination circuit.

FIG. 2 is a diagram showing an example of the signal 7 ormant in this embodiment.

In the figure, Pr is a preamble for pit synchronization, F is a frame synchronization signal, Infol-I nf.

3 represents an information bit string, ch represents a check pit, and G represents a guard pit.

In FIG. 1, a received signal is detected by a detection circuit 1, and a clock regeneration circuit 3 reproduces a clock synchronized with the received signal and detects a frame synchronization signal (for example,
In the signal 7 format shown in FIG. 2, this corresponds to the detection of the frame synchronization signal F). The information part includes, for example, three subintervals I
nf.

It is divided into 1, Info2, and Info3, each with a parity check bit (Ch) added, and the error detection circuit 2 performs this parity check.
Output the result. The selection circuit 5 controls the cutter input according to the timing circuit 4, and the detection results are totaled for each small section within one slot.

On the other hand, the envelope detection circuit 9 is sampled by the sample and hold circuit 10 in synchronization with the recovered clock, and the averaging circuit 11
The average reception envelope level can be found by

The determination circuit 12 determines the radio channel quality based on the erroneous detection results for each small section and the average reception envelope level. That is, quality deterioration due to thermal noise is determined based on the average reception envelope level. In other words, if the envelope level is small, it is determined that the horse mackerel has deteriorated due to thermal noise. Furthermore, quality deterioration due to interference is determined from the relationship between the envelope level and the number of detected errors. That is,
When the envelope level is large and there is deterioration, it is determined that it is due to interference.

Furthermore, based on the number of error detections for each subsection, it is found that if the slot corresponding to the channel of the interference wave is in use, but the entire slot is being interfered with, or there is a shift between stations, only the beginning or end of the slot is being used. If there is no influence, the slot corresponding to the interference channel is unused, only the adjacent slot is in use, and there is a misalignment between stations and only the beginning or rear of the slot is experiencing interference. An example of operation will be described with reference to FIG. 3 when the sixth embodiment for determining interference mode is applied to an uplink channel from a mobile station to a base station in a small zone mobile communication system.

The desired wave channel is slot 1, and the interference wave channel is slot 3.
An example is shown in which slots 1 and 3 are in use. The interference wave signal strength of the uplink channel is determined by the distance between each mobile station and the authorized base station (hereinafter referred to as the desired station)*, the propagation path condition, and if transmission power control is applied, each mobile station at that time. It varies depending on the transmission power etc.

Suppose that the received signal strength of the interference wave from the mobile station in slot 1 is small, that of slot 3 is large, and the slot timing of the interference wave is slightly delayed from that of the desired station due to inter-station synchronization deviation and propagation delay. The slot of the desired channel is divided into three sub-intervals indicated by letters 11-e or d-f in the same figure. When the number of errors detected in a certain period of time is measured for each of the slots, the number of errors in the first sub-interval is large, and the number of errors in the first sub-interval is large. The result is that the number of the second and third subsections is small.

This result shows that the slot timing of the interference channel is slightly delayed, and that although the number of errors detected is small on average, errors are concentrated at the beginning of the slot due to the influence of the third slot of the interference channel. This can be determined.

According to the present invention, since the error distribution within a slot can be determined in this way, by measuring the correspondence between the radio channel quality and the error distribution for each small section, it is possible to obtain quality that is more accurate and faithful to the quality perceived by the user. measurement becomes possible.

Furthermore, by combining the measurement results with adjacent slots, even more accurate quality monitoring is possible.

For example, the measurement result of a bit error in the last small section of the slot before the current slot is relatively poor, and the reception level is 5 dB higher than the previous slot. If the measurement result shows that the small section and the first small section of the own slot are receiving interference waves at the same level, it is determined that the own slot has a margin of 5 dB before the interference state of the previous slot. I can do it. Bit errors do not necessarily have a linear proportional relationship with the ratio of desired waves to interference waves, and tend to deteriorate rapidly when the ratio falls below a certain value, so they may be difficult to detect even in areas with good quality.

Radio channel quality monitoring is important in order to detect poor quality before the user feels it and to be able to take some countermeasures such as channel switching within a zone, and detection with relatively good quality is important (see above). Intra-zone channel switching refers to switching to another channel assigned to that base station due to interference, etc. when a certain channel is used for communication between one base station and a mobile station).

The present invention has the advantage that by using the relative relationship with adjacent slots, the linear range of error detection can be expanded and deterioration can be detected before quality deteriorates.

Although the above embodiment describes a case where a parity check is used for error detection, the present invention is not limited to this, and can be applied to other error detection codes.

Furthermore, when using a transmission path coding or modulation method with coding rules, bit errors can be estimated by detecting breakage of the rules.

For example, a method may be used in which the error is estimated by discriminating into a discriminant region that is greater than the number of multi-values of digital modulation (1 discriminant region, and is far from the discriminant region when there is no noise. In this case, error detection It is not necessary to add bits for this purpose, and the degree of freedom in setting the division of small sections is large, and it is possible to change it according to the situation.

In addition, if a specific pattern such as a 7-frame synchronization signal is being transmitted, the detection rate, or if the detection is not a perfect match detection but a permissible number of error bits in the frame synchronization pattern is set. The number of error bits can be used to estimate the error in that part.

For example, in the conventional car telephone system, an error of 1 bit out of 16 bits is allowed for detecting frame synchronization, so that number of bits can be used.

If frame synchronization protection is not used, and the frame synchronization signal cannot be detected, the entire slot will not be received and the entire slot will be affected. By performing the correction, more accurate quality monitoring becomes possible.

〔Effect of the invention〕

As explained above, the present invention is applied to a wireless communication system using TDMA, and even if there is interference in a part of a slot, it can be detected, and the error distribution in the slot and the wireless By correcting based on the correspondence with the channel quality, there is an advantage that quality can be measured more accurately and faithfully to the quality perceived by the user.

Furthermore, there is an advantage that by combining the measurement results in adjacent slots, it is possible to improve accuracy and expand the linear range of error detection.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing an example of the signal 7 format in this embodiment, and FIG.
The figure is an explanatory diagram of an example of the operation when this embodiment is applied to an uplink channel from a mobile station to a base station in a mobile communication system with a small zone configuration.

Claims (1)

[Claims] In wireless communication for transmitting digital signals, one slot section is divided into a plurality of small sections, and means for detecting the reliability of received bits for each small section and means for measuring the envelope level of the received signal are provided, A wireless channel quality monitoring method characterized by determining wireless channel quality based on reliability detection results and envelope level measurement results for each small interval.