KR20010033365A - Apparatus and method for signal detection by base station in a mobile communication system - Google Patents

Abstract

The present invention relates to a communication network 100 (e.g., cellular) comprising a mobile terminal 120, at least one base station 104 serving at least one mobile terminal 120 and at least one second base station 108. A method is provided for detecting a signal in a method, the method comprising the step wherein the mobile transmitted data detected at the first base station is used by the second base station to increase detection of data transmitted by the second base station. It features.

Description

Apparatus and method for detecting signal by base station in mobile communication system {APPARATUS AND METHOD FOR SIGNAL DETECTION BY BASE STATION IN A MOBILE COMMUNICATION SYSTEM}

In cellular communication networks such as IS95, mobile terminals communicating with base stations prefer to use closed and open loop transmit power control. This effectively means that the mobile terminal transmit power is optimized at a serving base station to a certain minimum level for proper detection in which the received signal level is defined as the quality of the required communication link. If the mobile terminal is in communication with one or more serving base stations, for example, during a soft hand-off period, the combined power or the strongest received signal (or a combination of the two techniques) may be at the required quality of the communication link. It is maintained to maintain a constant minimum level of a given proper detection. The power control mechanism ensures that the multiple access interface caused by the mobile terminal within or outside the radio range covered by the serving base station is kept to a minimum.

Although power control is desirable and more important in systems such as direct spread code division multiple access (DS-CDMA), it reduces the base station's ability to serve certain mobile terminals to receive and transmit mobile terminal transmissions appropriately and reliably. can not do. Reliable detection of mobile terminal transmissions by base stations other than the serving base station is preferred for services such as "location" and "hand off" operation. Thus, without any increase in mobile terminal transmission power, such that the information such as the propagation time delay (e.g. distance) and the mobile terminal signal power strength can fully utilize the received signal below the minimum required level for proper information data detection. It is desirable to increase the detection capability of a non-serving "base station.

The present invention relates in particular to a method and apparatus for detecting signals in a cellular communication network requiring location information and fast hand-off operation.

1 is a schematic diagram of a general embodiment of the present invention.

2 is a schematic diagram illustrating components of a portion of a first base station for an embodiment of the invention.

3 is a schematic diagram illustrating components of a portion of a second base station for an embodiment of the invention.

4 is a graphical representation of the data frame structure sent by the first and second base stations.

FIG. 5 is a schematic diagram illustrating components of a scrambler for scrambled and spread the data frame shown in FIG. 4; FIG.

6 is a graphical representation of a data frame structure transmitted by a mobile terminal.

FIG. 7 is a schematic diagram illustrating components of a scrambler for scrambled and spread the data frame shown in FIG. 6; FIG.

FIG. 8 is a flow chart showing the operational steps of the first base station schematically shown in FIG.

9 is a flow chart showing the operational steps of the second base station schematically shown in FIG.

The present invention is directed to increasing the detection capability of a mobile terminal transmitted signal by a cellular communication network, or a signal transmitted by the first and second base stations and detected by a mobile terminal.

According to one aspect of the invention, there is provided a signal detection method in a communication network comprising a mobile terminal, at least one first base station serving the mobile terminal and at least one second base station, Mobile terminal transmitted data is used by the second base station to increase detection of the transmitted data by the second base station.

Advantageously, the signal received by the first base station is of sufficient quality to enable detection of the data transmitted by the signal. Most preferably, the detected data is used by a second base station, wherein the mobile terminal transmission is not received with sufficient power for proper detection to enable detection of data by the second base station.

The detection method of the second base station is based on serial correlation, matched filter correlation, maximum likelihood sequence evaluation, connection detection or multiuser detection or any combination thereof.

The detection method at the second base station preferably comprises detecting the presence of data detected at the first base station.

Preferably the detection method at the second base station comprises detecting and calculating the received time delay caused by signal transmission due to the distance of the mobile terminal from the individual base station.

The detection method at the second base station additionally or optionally includes detecting the received signal power of the mobile terminal transmission signal by the second base station.

Preferably the mobile terminal is served by a first base station in association with a communication channel. Most preferably, the communication channel is a traffic channel, access channel or control channel that can be operated in a packet or direct switched mode.

The cellular communication network is preferably a direct spread code division multiple access (DS-CDMA) system, wherein the data is preferably used to extend and increase the processing gain of the receiver by enabling longer integration time at the base station. More preferably, the network system is a GSM or GSM derived system.

The location of the mobile terminal is for example using the time delay received at each individual base station, using the mobile terminal direction from each individual base station, or received time delay from the first base station and / or the mobile terminal. It can be determined from the network system by using a combination of the direction of and the received time delay from the second base station and / or the mobile terminal direction.

Positioning methods for mobile terminals using three or more fixed base stations of known positions are known in the art as triangulation or trilateration.

Preferably, the data received by at least the first base station can identify a mobile terminal in the network system.

The measured signal power of the mobile terminal can be used to prepare for hand-off from the first base station to the second base station.

Preferably the data transmitted by the mobile terminal is unknown information data.

Alternatively, or in addition, preferably the data transmitted by the mobile terminal is a predetermined sequence.

The data received by the first base station may be used by the first base station as well as or instead of the second base station to improve detection of the transmitted data by the mobile station.

Preferably, a spatial filter is used at the second base station to reduce the effect of the transmission channel on the received signal.

A second aspect of the invention provides an apparatus for detecting a signal in a communication network (e.g. cellular) comprising a plurality of base stations and a mobile terminal, wherein at least one of the base stations at a given time becomes a serving base station, Is served by the serving base station; The serving base station can receive and detect data sent to it by the mobile terminal, wherein the detected data is not used by the serving base station and / or at least one other base station to increase detection of the transmitted data. It is characterized by.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

A cellular system 100 (FIG. 1) installed in a geographic area, eg, urban center 102, has a first base station 104 having a first associated coverage area 106, and a second associated coverage area 110. And a coverage area 111 associated with the second base station 108 and the third base station 107.

The first, second and third base stations 104, 108, 107 are independently connected to a base station controller (BSC) 112, and the BSC 112 is connected to a mobile switching center (MSC) 114. have. The MSC 114 communicates with a fixed terminal 116 via a public switched telecommunication network (PSTN) 118.

Examples of the first, second and third base stations 104, 108, 107 are supercell (trade name) base station units manufactured by Motorola. The supercell base station has hardware and / or software modifications to function as time delay evaluation units 220 and 320. The mobile terminal 120 is disposed within the first coverage area 106 and the second coverage area 110. However, it is not critical for the mobile terminal 120 to be disposed within the second coverage area 110. The mobile terminal 120 may be disposed around the second and third coverage areas 110 and 111.

An example of the mobile terminal 120 is a Qualcomm QCP / 820 model cellular telephone.

Referring to FIG. 2, the first base station 104 includes a receiver chain 200. The receiver chain 200 has an antenna 202 coupled to the low noise amplifier 204. The low noise amplifier 204 is coupled to a band pass filter 206. The band pass filter 206 is coupled to the mixer 208. The mixer 208 is coupled to the low pass filter 212 and the synthesizer unit 210. The low pass filter 212 is coupled to an analog-to-digital converter (ADC) 214, which is coupled to a digital signal processor (DSP) 218 via a buffer 216.

In addition, the buffer 216 is coupled to the delay evaluation unit 220. The delay evaluation unit 220 is also coupled to the DSP 218. Within delay evaluation unit 220, the buffer output is coupled to multiplier 222. The multiplier 222 is coupled to the integrator 224 and the variable delay unit 226. The integrator unit 224 is coupled to the peak detector 230 and transmitted symbols set to an initial value of zero, for example at the beginning of each correlation operation starting at the beginning of each received data symbol. To integrate the received data over a period Ts. The output of the peak detector 230 is coupled to the processor 232. The variable delay unit 226 is coupled to both the processor 232 and the code unit 228. Finally, clock 234 is coupled to processor unit 232. The clock 234 is also coupled to the code unit 228.

The receiver operates in the presence of in-phase and quadrature phase components (eg, complex data).

The receiver chain 200 described above is shown for illustrative purposes only and may also form part of a transceiver circuit (not shown).

Referring to FIG. 3, the second and third base stations 108, 107 each include a receiver chain 300. The receiver chain 300 has an antenna 302 coupled to the low noise amplifier 304. The low noise amplifier 304 is coupled to a band pass filter 306. The band pass filter 306 is coupled to the mixer 308. The mixer 308 is coupled to the low pass filter 312 and synthesizer unit 310. The low pass filter 312 is coupled to an analog to digital converter (ADC) 314 that is coupled to a buffer 316. The buffer 316 is coupled to the delay evaluation unit 320. Within delay evaluation unit 320, the buffer output is coupled to multiplier 322.

The multiplier 322 is coupled to the integrator 324 and variable delay unit 326. The integrator 324 is set to an initial value of zero at the beginning of each correlation operation, for example at the beginning of the received data block, and integrates the received data for the required period Ti. The output of the peak detector 330 is coupled to the processor 332. The variable delay unit 326 is coupled to a multiplier 329 and also to a processor 332. Clock 334 is coupled to processor 332. The multiplier 329 is coupled to both the DSP unit 319 and the code unit 328. The DSP unit is coupled to the information data unit 318. The clock 334 is also coupled to the code unit 328.

The receiver operates in the presence of in-phase and quadrature phase components (eg, complex data).

The receiver chain 300 described above is shown for illustrative purposes only and may also form part of a transceiver circuit (not shown).

The first, second and third base stations 104, 108, and 107 may all transmit a sequence of 20 msec data frames having a data frame structure 400 (shown in FIG. 4). The data frame 400 has a structure including information data units 436, 438, 440, 442, 446, 448, 450, 452, 454, 456, 460, 462, 464, 466, and 468. The frame structure 400 also includes 16 power control data units 404, 406, 408, 410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434.

The data frame 400 is scrambled and spread by the scrambler code 500. Spreading is to extend the signaling bandwidth of data frame 400. The scrambler includes several codes 504, 506, 508 and 510 known for all network components, such as base stations 104, 108 and 107 and mobile terminal 120, for example.

Referring to FIG. 5, the data is scrambled and spread by the LC code 504 in the multiplier 512. The data is further scrambled by Walsh code 506 in multiplier 514. The scrambled data obtained is then scrambled once by I code 510 during in-phase transmission at multiplier 516 and scrambled once by Q code 508 during quadrature phase transmission at multiplier 518. The resulting scrambled and spreading code is referred to as the scrambling code 502 for such an example.

The scrambling code 502 is used for the calculation of various parameters such as channel estimation, frame synchronization and coherent detection of data, for example. The mobile terminal 120 operation is synchronized to the scrambling code 502.

The mobile terminal 120 may transmit a sequence of 20 msec data frames having a data structure 600. The data frame 600 is mostly composed of information data units.

The data frame 600 is scrambled and spread by the scrambler 700. Spreading is to extend the signaling bandwidth of data frame 600. The scrambler 700 includes several codes 704, 712, 706 that are known for all network components such as, for example, base stations 104 and 108 and mobile terminal 120.

Referring to FIG. 7, the data is scrambled and spread by the LC code 704 in the multiplier 710. The resulting scrambled and spread data is then scrambled once by I code 708 during in-phase transmission at multiplier 7122 and scrambled once by Q code 706 during quadrature phase transmission at multiplier 714. The resulting scrambling and spreading code is referred to as scrambling code 702 for such an example.

The operation of the cellular system 100 will now be described below.

The call is made according to a technique known in the art. A first base station 104 and a first traffic channel (tch) in communication with the mobile terminal 120 are assigned. A data frame having the structure of the first data frame structure 400 is transmitted from the first base station 104 and received by the mobile terminal 120. The data frame having the structure of the second data frame structure 600 is transmitted from the mobile terminal 120 and received by the first base station 104. The power control data 404, 406, 408, 410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434 allows the first base station 104 to be known in the art. Accordingly, the transmission power of the mobile terminal 120 is controlled. The data frame 600 received by the first base station antenna 202 only has sufficient power for the propagation time delay by the first base station 104 and the correct detection of the information data. With regard to information data, it refers to unknown information data present in data frame 400 and data frame 600.

Therefore, the mobile terminal 120 transmit power is only large enough to overcome the propagation loss for the first base station 104. Second and third base stations 108 and 107 that are not in communication with the mobile terminal 120 may experience excessive propagation loss, so that they have sufficient power for time delay and reliable and successful detection of information data. Cannot receive the data frame 600 sent by < RTI ID = 0.0 >

A method of detecting the information data 828 and the time delay 829 for the first base station 104 is outlined in FIG. 8 and is as follows. The synthesizer 210 of the first base station 104 is adjusted to receive the data frame transmitted from the mobile terminal 120 at the predicted arrival time (step 802). When the traffic data frame 600 is received, in the designated time frame, the traffic data is stored by the first base station 104 (step 806).

The first base station 104 then determines whether enough time has elapsed to receive the entire data frame 600 (step 808). Consider the longest expected propagation time delay due to the distance between the first base station 104 and the mobile terminal 120. If not enough time has elapsed, the first base station 104 continues to receive and store traffic data (step 806). When the specified time has elapsed, the first base station 104 initializes the elapsed time delay T to zero (step 810).

Next, a descrambling code similar to the scrambling code 702 (known in the prior art as code synchronized) at the time of transmission of the data frame 600 by the mobile terminal 120 is delayed by a specified time delay T. (Step 812). The first base station 104 descrambles the data traffic received with the delayed descrambling code 702 (step 814). The descrambled data traffic is then summed (integrated) over the data symbol period Ts (step 818).

If a substantial peak is not detected by the first base station 104, the predicted time delay T is increased (by a set amount) (step 820) and steps 812 and 814 until a substantial peak is detected. , 816, 818, and 820 are repeated. After detecting the substantial peak, the first base station 104 calculates and stores the time delay and further calculates the distance from the mobile terminal 120 (step 822).

In the presence of multipath delivery, several peaks can be detected, where one or more peaks can be used for data detection.

After successful evaluation of the time delay between the first base station 104 and the mobile terminal 120, the correction of the received traffic data is selected in the data frame portion 600 and transmitted by the mobile terminal 120 (step 826). Next, the information data contained in the data frame 600 is detected and stored (step 428).

The time delay and distance between the first base station 104 and the mobile terminal 120 are sent to the MSC 114 and stored.

The time delay detection method for the second base station 108 is outlined in FIG. 9 and is as follows.

The synthesizer 310 of the second base station 108 is adjusted to receive the data frame 600 at the predicted arrival time of the data frame 600, transmitted from the mobile terminal 120 (step 902). When the traffic data is received, at a designated time, the traffic data is stored by the second base station 108 (step 906).

The second base station then determines whether enough time has elapsed to receive the entire data frame 600 (step 908), which is caused by the distance between the second base station 108 and the mobile terminal 120. Allow longer predicted propagation time delays. If not enough time has elapsed, the second base station 108 continues to receive and store traffic data (step 906). When the designated time has elapsed, the second base station 108 acquires and stores the information data 318 detected and stored by the first base station 104 via a network component such as the BSC 112 in step 828 ( Step 910).

The second base station 108 then processes the stored information data 318 in a manner similar to the processing and scrambling performed by the mobile terminal 120 on the original information data (319), and the scrambling code 702, 328 and store it prior to transmission of data frame 600 (step 912). After step 912, the stored processed and scrambled information data, now referred to as "data descrambling code", is substantially similar to data frame 600 transmitted by mobile terminal 120 in envelope and phase.

The second base station 108 then begins to initialize the predicted time delay T to zero (step 916). The "data descrambling code" is then delayed by a specified delay T (step 918). The second base station 108 descrambles the received data traffic with a “data descrambling code” (step 920). The descrambled data traffic is then summed (integrated) over a sufficiently long time Ti to ensure reliable and successful detection of the data frame 600 transmitted by the mobile terminal 120 (step 922). Ti is long enough to provide sufficient processing gain to account for all possible excess propagation losses experienced by the second base station 108 when compared to that experienced by the first base station 104.

The second base station 108 then determines whether a substantial peak was detected as a result of the sum (step 928). If the peak is not detected by the second base station 108, the predicted time delay T is increased (step 924) and the steps 918, 920, 922, 926 and 924 until a substantial peak is detected. Is repeated. After detection of an acceptable peak, the second base station 108 calculates and stores the time delay and further calculates the distance that the mobile terminal 120 is away from the second base station 108 (step 928).

The third base station 107 performs a time delay detection method substantially the same as that already described for the second base station 108.

The time delay and distance between the second base station 108 and the mobile terminal 120 are sent to the MSC 114 and stored. The time delay and distance between the third base station 107 and the mobile terminal 120 are sent to the MSC 114 and stored. The MSC 114 determines the mobile terminal 120 from the first and second and third base stations 104, 108, 107 by a method known as triangulation in order to evaluate the coordinates of the mobile terminal 120. Stored data for distance, known coordinates of the first, second and third base stations 104, 108, 107 are used.

The remaining components of the cellular communication system base station are well known in the art and will not be described here in detail.

Although the present invention has been described above in accordance with one preferred embodiment of the present invention, various modifications may be made without departing from the spirit of the present invention as defined by the appended claims. It is obvious to those skilled in the art.

Claims (24)

A method for detecting a signal in a communication network comprising a mobile terminal, at least one first base station serving the mobile terminal and at least one second base station, And the mobile terminal transmitted data detected at the first base station is used by the second base station to increase detection of the transmitted data by the second base station. The method of claim 1, wherein the signal received by the first base station is of sufficient quality to enable detection of the data transmitted by the signal and the detected data is used by the second base station. Terminal transmission is not received with sufficient power for proper detection to enable detection of data by the second base station. 3. A method according to claim 1 or 2, wherein the detection method at the second base station comprises detecting and calculating the received time delay caused by signal transmission due to the distance of the mobile terminal from the individual base station. How to. 4. A method according to any one of claims 1 to 3, wherein the detection method at the second base station comprises detecting a received signal power of a mobile terminal transmission signal by the second base station. The communication network according to any one of claims 1 to 4, wherein the communication network is a cellular communication direct spread type code division multiple access (DS-CDMA) system, and the data is processed by a receiver by enabling a longer integration time at the base station. Characterized in that it is used to extend and increase the gain. The method according to any one of claims 1 to 5, wherein the location of the mobile terminal is determined by the following method-(a) using the received time delay at each individual base station, and (b) the mobile terminal from each individual base station. Using the direction, by (c) a combination of the received time delay from the first base station and / or the direction of the mobile terminal and the received time delay from the second base station and / or the direction of the mobile terminal. Determined from the network system. 7. A method according to any one of the preceding claims, wherein at least the data received by the first base station can identify a mobile terminal in the network system. 8. A method according to any one of the preceding claims, wherein the measured signal power of the mobile terminal is used to prepare for hand-off from the first base station to the second base station. 9. A method according to any one of the preceding claims, wherein the detection method at the second base station comprises detecting the presence of data detected at the first base station. 10. A method according to any one of the preceding claims, wherein the data transmitted by the mobile terminal is unknown information data. 10. A method according to any one of the preceding claims, wherein the data transmitted by the mobile terminal is a predefined sequence. An apparatus for detecting a signal in a communication network comprising a plurality of base stations and mobile terminals, the apparatus comprising: At a given time, at least one of the base stations becomes a first serving base station, and the mobile terminal is served by the first serving base station; The first serving base station can receive and detect data transmitted to it by a mobile terminal, the detected data being used to increase the detection of the transmitted data and / or the at least one primary base station. 2 A device which can be used by a base station. 13. The system of claim 12, wherein the signal received by the first base station is of sufficient quality to enable detection of data transmitted by the signal, wherein the mobile terminal transmission is not received with sufficient power for proper detection. And wherein the second base station comprises means for using the detected data to enable detection of the data by the second base station. 14. A method according to claim 12 or 13, wherein the second base station comprises means for detecting and calculating the received time delay caused by signal transmission due to the distance of the mobile terminal from an individual base station. Device. 15. The apparatus according to any one of claims 12 to 14, wherein the second base station comprises means for detection of the received signal power of a mobile terminal transmission signal by the second base station. The communication network according to any one of claims 12 to 15, wherein the communication network is a cellular communication direct spread code division multiple access (DS-CDMA) system, which extends the processing gain of the receiver by enabling a longer integration time at the base station. Means for using the data to increment. 17. The method according to any one of claims 12 to 16, comprising the following methods: (a) using the received time delay at each individual base station, (b) using the direction of the mobile terminal from each individual base station, c) move from the network system by any of-by a combination of the received time delay from the first base station and / or the direction of the mobile terminal and the received time delay from the second base station and / or the direction of the mobile terminal. Means for determining the location of the terminal. 18. The apparatus according to any one of claims 12 to 17, comprising means for using at least the data received by the first base station to identify a mobile terminal in the network system. 19. The apparatus according to any one of claims 12 to 18, comprising means for using the measured signal power of the mobile terminal in preparation for hand-off from the first base station to the second base station. 20. The apparatus of any of claims 12 to 19, wherein the second base station comprises means for detecting the presence of data detected at the first base station. 21. The apparatus according to any one of claims 12 to 20, wherein the data transmitted by the mobile terminal is unknown information data. 21. An apparatus as claimed in any of claims 12 to 20, wherein the data transmitted by the mobile terminal is a predefined sequence. A signal detection method as in one embodiment described herein or related to the accompanying drawings. Apparatus for signal detection as in one embodiment described herein or related to the accompanying drawings.