Mobile station

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to mobile stations used in CDMA systems.

【0002】

[Conventional technology]

A CDMA system is a system that multiplexes using a plurality of spreading codes on the same frequency in order to multiplex a plurality of communications. Compared to FDMA and TDMA, this CDMA system has the problems of high power consumption and short battery life for the following reasons.

【0003】

That is, in the cellular system, the handover process of switching the radio channel with the movement of the mobile station is performed. When performing the handover, the mobile station detects the reception quality of the signal from the base station and determines whether to switch the channel based on the result. When detecting the reception quality, the FDMA or TDMA mobile station detects the electric field strength of the RF signal received from the base station.

【0004】

On the other hand, in the CDMA system, when looking at each signal only with the RF signal, the same frequency is used, so each RF signal is demodulated to the baseband signal, and the PN code assigned to each signal is used as the signal. Each signal can be separated by multiplying and back-spreading. Therefore, in the mobile station in the CDMA system, many circuits such as the IF section and the baseband section of the receiving system operate in addition to the RF section at the time of handover, which consumes a large amount of current in the receiving system.

【0005】

Moreover, in a CDMA system, when performing a handover, the reception quality of a signal from a connected base station and the reception quality of a signal from an adjacent base station are measured (this controls the mobile station to assist the handover. (It is called Mobile Assist Handover, commonly known as MAHO function). If the reception quality of the signal from the adjacent base station is better than the specified judgment standard value, it is from the channel of the connected base station. Switch to the channel of the adjacent base station.

【0006】

However, in the conventional CDMA system, MAHO control is performed regardless of the quality of signal reception from the connected base station. Therefore, even if the signal reception quality from the connected base station is good, a large amount of power is consumed because MAHO is performed.

【0007】

[Problems to be Solved by the Invention]

As described above, in the conventional mobile station, the handover is performed regardless of the reception level of the signal from the connected base station, which causes power consumption. Therefore, it is an object of the present invention to provide a mobile station capable of suppressing power consumption by minimizing the processing required by the mobile station for handover.

【0008】

[Means for solving problems]

The present invention achieves the above object by prohibiting the control required for handover or making the control interval longer than the normal interval when the reception level of the signal from the connected base station is good.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described. In the CDMA mobile communication system, a plurality of base stations are distributed. A cell is formed in each of these base stations. Then, each of these cells is divided into a plurality of sectors. A spreading code is assigned to each sector.

【0010】

When in a call state, the mobile terminal device receives a notification of a diffusion code corresponding to each of the adjacent base stations in the signal from the connected base station during communication with the connected base station. Based on this information, the reception quality of the adjacent base station is detected at the same time during the communication with the connected base station. Then, when the reception quality of the signal from the adjacent base station is higher than the reception quality of the signal from the connected base station, the signal having the best reception quality among the adjacent base stations is broadcast. Handover processing for switching to a base station is performed.

【0011】

The present invention is characterized in that the necessity of handover processing is determined by an original method. FIG. 1 is a block unit showing the configuration of a mobile station according to the present embodiment.

【0012】

In the figure, the transmitted voice signal output from the microphone 10a is converted into a digital signal by the A / D converter 11a and then input to the encoder 14 that performs voice coding. In the encoder, it is compressed to a small amount of data by voice coding.

【0013】

An error detection code and an error correction code are added to the coded digital audio signal by the error correction coding unit 16. Then, the coded data is spread by the spread spectrum 18 by a PN code that is negotiated and determined each time with the base station. The diffused signal is converted into an analog signal by the D / A converter 24 after the unnecessary frequency components are removed by the digital filter 20. This analog signal is converted to a radio frequency by the RF unit 26, then raised to a predetermined power level and transmitted via the antenna 28.

【0014】

On the other hand, the radio signal received by the antenna 28 is amplified by the RF unit 26 and then down-converted to the baseband (low frequency band). This down-converted signal is converted into a digital signal by the A / D converter 30 at a predetermined sampling cycle, and then input to the RAKE receiving unit 32 and the search receiving unit 34.

【0015】

The RAKE receiver 32 has three finger circuits and a symbol synthesizer that symbol-synthesizes the output signals of these finger circuits. The finger circuit synthesizes the received signals of three different paths by performing despreading on the received signals of the desired path having a large reception level. The search receiving unit 34 multiplies the receiving baseband signal by the spread code peculiar to the peripheral base station notified in advance from the base station and examines the correlation, so that the reception quality of the signal from the base stations around the connected base station is examined. Is used to measure. This data is taken into the control unit.

【0016】

The symbol output from the RAKE receiving unit 32 is subjected to error decoding processing by the error correction decoding unit 38 to become received data. Of the received data, the audio data is audio-decoded by the decoder 40, converted into an analog signal by the D / A converter 42, and then output from the speaker 44.

【0017】

In the CDMA mobile radio system, the information neighbor list about the surrounding base stations is also received during the communication with the connected base station. By inspecting the reception quality of signals from peripheral base stations based on this information, the mobile station itself has a MAHO function to prepare data for determining whether or not to hand over.

【0018】

It is decided that the reception quality of signals from peripheral base stations is inspected at fixed intervals, but in the past, inspections were performed regardless of whether the reception quality of signals from connected base stations was good or bad. .. Especially in a CDMA system, since peripheral base stations use the same frequency, it is not possible to determine which base station has the best conditions by quality comparison using RF signals. Therefore, the frequency of the baseband signal is lowered, and the baseband signal is back-spread by applying a diffusion signal determined for each base station to separate the signals from the peripheral base stations. Check the reception quality when. Therefore, it consumes more power than the case where the reception quality of the signal of the peripheral base station can be seen by the RF signal such as MAHO in the conventional TDMA. Therefore, in the present invention, the MAHO function in the CDMA system is omitted when it is unnecessary to make it difficult to consume power.

【0019】

Figure 2 shows the function of not checking the received signal level of peripheral base stations, that is, not performing MAHO operation, if the reception quality of the signal from the connected base station is above a certain level.

【0020】

From the base station connected in step 102, the spread code information (neighbor list) assigned to the adjacent base station is received. Then, the reception level of the signal from the connected base station is dropped to the baseband band, and the signal is back-diffused and measured, and compared with the predetermined threshold value TH (step 104).

【0021】

As a result, when it is determined that the reception quality is sufficiently good, the measurement of the reception level of the signal from the adjacent base station (MAHO) is prohibited (step 106), and the reception of a new neighbor list is waited for. On the other hand, if the signal quality from the base station connected in step 104 is worse than the threshold value, the received signal from the normal adjacent base station is measured (step 108), and based on the obtained information. , Determining whether or not to perform handover, and performing control processing (hereinafter, this is referred to as normal handover processing, step 110).

【0022】

FIG. 3 shows different embodiments. The difference from the embodiment of FIG. 2 is that the processing when the reception quality of the signal from the connected base station is better than the threshold value is different. Therefore, the reception level determination process (steps 202 and 204) is the same as that in FIG. 2, and the description thereof will be omitted. If the reception level is better than the threshold value in step 204, set the detection interval so that the detection interval of the reception level of the signal from the adjacent base station is T1 which is longer than the conventional detection interval T2 (step). 206). By doing so, when the reception quality of the signal from the connected base station is good, the battery consumption can be suppressed by lengthening the execution span of MAHO.

【0023】

If the reception quality of the signal from the base station connected in step 204 is not better than the threshold value, MAHO is performed at T1 intervals (step 208). When the processing in steps 206 and 208 is completed, the normal handover processing is performed (step 210). FIG. 3 is a diagram showing another embodiment. The following information is received from the base station connected in step 302.

【0024】

1. PN code assigned to the nearest base station 2.1 PN code assigned to a base station located around the base station Then, it is determined whether the reception level of the signal from the connected base station is equal to or higher than the threshold value (step 304), and if the reception quality is good, only the PN code of the closest base station of 1 is used. Detect reception quality (step 306). By doing so, when the reception quality from the connected base station is good, the reception quality detection of the peripheral base stations can be minimized, so that the power consumption can be suppressed.

【0025】

If the reception quality is poor, the reception quality is measured using the PN codes of both base stations 1 and 2 of the adjacent base stations (step 308). A normal handover is performed based on the measurement information in steps 306 and 308 (step 310).

【0026】

In FIG. 4, the threshold value for determining the signal quality of the adjacent base station is not determined in advance, but is set for each connected base station, and the value is received from the connected base station. (Step 402). It is determined whether the reception level of the signal from the connected base station is higher than the received threshold value TH1 (step 404), and if it is higher, the measurement of the reception level of the signal from the adjacent base station is prohibited. (Step 406) Wait for the next threshold and neighbor notification.

【0027】

If it is small, the reception level of the signal from the adjacent base station is measured (step 408), and the normal handover process is performed (step 410). FIG. 5 is different from the above-described embodiment in that the threshold value for determining the reception level is set to two levels. That is, it receives a neighbor list from the connected base station (step 502). Then, it is determined whether or not the reception level of the signal from the connected base station is larger than the first threshold value TH1 (step 504), and if it is larger, the reception level detection interval T of the signal from the adjacent base station is determined. To the highest value T3 (step 506). If it is less than the threshold TH1, compare the receive level with the second threshold TH2 (TH2 is less than TH1) (step 508), and if it is greater than TH2, set the MAHO interval T to T2. To do. T2 is a smaller value than T3.

【0028】

If the level of the received signal of the connected base station in step 508 is lower than TH2, the execution interval T of MAHO is set to T1 (step 512). T1 is a smaller value than T2. Therefore, the relationship of T1, T2, and T3 is T3> T2> T1. When the settings in steps 506, 510, 512 are completed, normal MAHO and handover processing are performed (step 514). [0029]

[Effect of the invention]

As described above, in the present invention, in the measurement of the reception level of the signal from the peripheral base station for performing the handover in the CDMA system, if the reception level of the signal from the connected base station is large, the measurement is performed. It is possible to reduce the battery consumption by not performing the above or by making the measurement interval longer than usual.

[Simple explanation of drawings]

[Figure 1]

Block diagram showing an embodiment of the present invention [Figure 2]

The flowchart which shows the 1st control in the mobile station of the Example of this invention. [Fig. 3]

The flowchart which shows the 2nd control in the mobile station of the Example of this invention. [Fig. 4]

The flowchart which shows the 3rd control in the mobile station of the Example of this invention. [Fig. 5]

The flowchart which shows the 4th control in the mobile station of the Example of this invention. [Fig. 6]

The flowchart which shows the 5th control in the mobile station of the Example of this invention. [Explanation of symbols]

34 ... Search receiver 36 ... Control unit