CN1422023A - Rick receiving device and method - Google Patents

Abstract

A RAKE receiving device and method are used in a wireless spread spectrum communication system. The RAKE receiving device includes a multiplexing unit, a search unit, a first switching unit, a second switching unit, a RAKE finger and tracking unit, a RAKE control unit, a combination unit, a decoding unit and a channel estimation unit. Multiple antenna units of a base station share a search unit to reduce the complexity of the system. The number of RAKE fingers allocated to each communication link is dynamically allocated to improve the utilization efficiency.

Description

Rick receiving device and method

Technical field

The present invention relates to a rake receiving device and method, and in particular to a rake receiving device and method used for a base station of a wireless spread spectrum communication system.

Background technique

In a wireless spread spectrum communication system (wireless spread spectrum communication system), such as a Code Division Multiple Access (CDMA) system, a mobile station (Mobile Station, MS) establishes a communication link with a base station (Base Station, BS) (radio, link) must request a unique identification code (Pseudo-NoiseCode, PN Code) from the base station, different mobile stations use different identification codes to transmit information bits (information bit), and the base station at the receiving end is also based on the mobile station The identification code is used to demodulate received wireless signals so that multiple mobile stations can use the same channel to transmit signals. However, during the transmission process, there will be multipath interference (multipath). Multipath interference means that after the signal is transmitted from the transmitter, the signal reaches the receiver through more than one path, such as reflection from buildings in the city or atmospheric pressure. Reflection, etc., so that the signal received by the receiving end does not only arrive through one direct path, but also includes signals arriving through other paths, and there will be a transmission time difference between these multipath component signals. Referring to Fig. 1, it shows the time-delay power spectrum of the signal containing multipath components received by the base station. In the figure, there are multipath component signals P1, P2 and P3. The three multipath component signals all represent the same information bit, but the arrival times are different due to multipath interference. The propagation delay times of the multipath component signals P1 , P2 and P3 in the figure are t1 , t2 and t3 respectively.

In the wireless spread spectrum communication system, the rake receiver (rake receiver) is suitable for the demodulator (demodulator) of the multi-path transmission environment, and is used to demodulate the wireless signal received by each antenna to obtain the information bits sent by each mobile station Merge output. Generally, a rake receiving device includes a plurality of rake fingers and a combiner. Each rake finger is used to receive a multipath component signal, adjust its time difference and output it after demodulation. The combination unit, for example, uses the maximum ratio combining technique (maximum ratio combining technique) to combine the signals belonging to the same communication link in the output signal of the Rick finger to obtain the maximum signal to noise ratio (signal tonoise ratio, S/N ratio ), so that the bit error rate (bit error rate) is reduced. In order to make the rake receiving device have the best performance, two prediction techniques need to be used: the first one is to obtain the transmission delay time information of each multipath component signal, so that each rake finger can correctly transfer the received signal Perform despreading. The second technique is to obtain channel characteristic information such as the amplitude and phase of each multipath component signal, so that the combination unit can optimize the combination of each multipath component signal of the same communication link.

Contents of the invention

In view of this, the object of the present invention is to provide a rake receiving device and method for demodulating transmitted information bits in a transmission environment with multipath interference.

According to an object of the present invention, a rake receiving device is proposed. The brief description of the device is as follows: the rake receiving device is used in a wireless spread spectrum communication system, and the wireless spread spectrum communication system includes a base station and a plurality of mobile stations. These mobile stations respectively establish radio links with the base station to send spread spectrum signals including a plurality of information bits. These spread spectrum signals are transmitted in an environment with multipath interference, so that multiple multipath component signals are generated in each spread spectrum signal. The base station includes a plurality of antenna units, and each antenna unit receives wireless signals and outputs digital signals. The RAKE receiving device includes a multiplexing unit, a search unit, a first switching unit, a second switching unit, a RAKE finger and tracking unit, a RAKE control unit, a combination unit, a decoding unit and a channel estimation unit. The multiplexing unit is connected with each antenna unit, and is used for receiving various digital signals, and selecting one of these digital signals to output a digital input signal according to the multiplexing control signal. The search unit is connected with the multiplexing unit, and is used to receive the digital input signal, and find the delay time corresponding to the multipath component signal contained in the communication link in the digital input signal according to the search control signal, and output the transmission delay time signal accordingly . The first switching unit includes a plurality of input terminals and a plurality of output terminals, and the input terminals are respectively connected to the antenna units for receiving the digital signals and outputting a plurality of first switching signals according to the first switching control signal. The rake finger and the tracking unit include a plurality of rake fingers (rake fingers), and these rake fingers are respectively connected to the output ends of the first switching unit, and are used to respectively receive at most one first switching signal and set the rake finger according to the rake control signal The corresponding first switching signal is despread and its transmission time delay is adjusted to output a despread signal. The second switching unit is connected with the RAKE fingers, receives the despread signals and switches the despread signals according to the second switch control signal. The combining unit is connected to the second switching unit, and is used to combine the despread switching signals according to the channel signals to output a combined signal. The decoding unit is connected with the combining unit, receives the combined signal and extracts the information bits accordingly to output the decoded signal. A channel estimation unit (Channel Estimator) is connected with these rake fingers and combination units, and is used for estimating the channel characteristics of these despread signals and outputting channel signals accordingly. The RAKE finger control unit is the control center of the RAKE receiving device, and is connected with the multiplexing unit, the search unit, the first switching unit, the RAKE finger and tracking unit, the second switching unit, the combining unit, the decoding unit and the channel estimation unit, It is used to output the multiplexing control signal, the search control signal, the first switching control signal and the second switching control signal.

According to another object of the present invention, a method for controlling a shared search unit is proposed. The control method includes the following steps: First, selectively extract search requests (raquest) from the search queue. Then, selectively connect the antenna unit with the search unit. Then, the search unit receives the digital signal and searches for the multipath component signal included in the digital signal according to the search request, and outputs a transmission delay time signal accordingly. Then, monitor the signal quality output by the rake receiver.

In order to make the above objects, features, and advantages of the present invention more comprehensible, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Description of drawings

Fig. 1 shows the time-delay power spectrum that contains the multipath component signal received by the base station;

Fig. 2 is a block diagram showing a rake receiving device according to a preferred embodiment of the present invention;

Figure 3 is a block diagram representing a search unit;

Fig. 4 is a block diagram showing a RAKE finger and tracking unit.

FIG. 5 is a schematic diagram showing the operation of the RAKE finger and the tracking unit.

Fig. 6 is a state transition diagram showing a communication link.

Explanation of the numbers in the drawings

101: Antenna unit

110: Rick receiver

120: multiplexing unit

130: Search unit

132: filter

134, 154: Identification code generator

136: Sequence Parallel Matched Filter

138: Peak Finder

140, 160: exchange unit

150: Rick finger and tracking unit

158: Despreader

170: Combined unit

180: decoding unit

190: channel estimation unit

200: Rick Control Unit

Specific implementation methods

Referring to Fig. 2, it shows a block diagram of a rake receiving device according to a preferred embodiment of the present invention. The rake receiving device 110 is used in a wireless spread spectrum communication system, and the wireless spread spectrum communication system includes a base station and multiple mobile stations. These mobile stations respectively establish wireless communication links (radiolink) with the base station to send out spread spectrum signals including multiple information bits, and these spread spectrum signals are transmitted in an environment with multipath interference, so that multiple multipath component signals are generated in each spread spectrum signal. The base station includes a plurality of antenna units 101, and each antenna unit 101 receives a wireless signal and outputs a digital signal D. The RAKE receiving device 110 includes a multiplexing unit 120, a search unit 130, a switching unit 140, a RAKE finger and a tracking unit 150, a switching unit 160, a combining unit 170, a decoder 180, a channel estimation unit (Channel Estimator) 190 and a RAKE Refers to the control unit 200 . The multiplexing unit 120 is connected to the antenna units 101 for receiving the digital signals D, and selecting one of the digital signals D to output the digital input signal DI according to the multiplexing control signal Cm. The search unit 130 is connected with the multiplexing unit 120, and is used to receive the digital input signal DI, and find the delay time of these multipath component signals included in the communication link corresponding to the search control signal Cs included in the digital input signal DI and according to to output a transmission delay time signal TD. Taking FIG. 1 as an example, the transmission delay time signal TD is information corresponding to times t1, t1 and t3. Since the computing power required by the search unit 130 is extremely complex, the present invention enables multiple antenna units 101 to share the search unit 130 to minimize the number of search units 130 and reduce the complexity of the system. The shared search unit 130 The control method will be described in detail below.

The switching unit 140 is connected with these antenna units, and is used for receiving these digital signals D and outputting a plurality of switching signals S1 according to the switching control signal Cw1. The rake finger and tracking unit 150 includes a plurality of rake fingers (rake finger) 152, and these rake fingers 152 are respectively connected to the output ends of the switching unit 140 for receiving at most one switching signal S1 respectively, and according to the rake control The signal Cr despreads the corresponding switching signal S1 and outputs the despread signal R after adjusting the transmission time delay. The switch unit 160 is connected to the RAKE fingers 152, receives the despread signals R and outputs the multi-switch signal S2 according to the switch control signal Cw2. The combining unit 170 is connected with the switching unit 160, and is used for combining these switching signals S2 according to the channel signal E to output a combined signal SC. The decoding unit 180 is connected with the combining unit 170, receives the combined signal SC and extracts the information bits sent by the mobile station accordingly, so as to output the decoded signal DC. The channel estimating unit 190 is connected with the RAKE finger and tracking unit 150 and the combining unit 170 for estimating the channel characteristic of the despread signal R and outputting the channel signal E accordingly.

The RAKE finger control unit 200 is the control center of the RAKE receiving device 110, together with the multiplexing unit 120, the search unit 130, the switching unit 140, the RAKE finger and tracking unit 150, the switching unit 160, the combining unit 170, and the decoding unit 180 Be connected with channel estimation unit 190, be used for outputting multiplexing control signal Cm so that different digital signals D are fed into search unit 130; Output search control signal Cs is to designate search unit 130 to search for the multipath component signal of one of these communication links Output switching control signal Cw1 so that the multipath component signals of each communication link correspond to one of these rake fingers 152 respectively; Output switching control signal Cw2 so that the despread signal R belonging to the same mobile station is fed into the combining unit 170.

Referring to FIG. 3, a block diagram of the search unit 130 is shown. The search unit 130 includes a filter 132 , an identification code generator 134 , a sequence-parallel matched filter 136 and a peak searcher 138 . The filter 132 is used for receiving the digital input signal DI and outputting the filtered signal DF accordingly. The identification code generator 134 is used for receiving the search control signal Cs and generating an identification code PN accordingly. The serial parallel matched filter 136 is connected to the filter 132 and the identification code generator 134 for outputting the matching signal SP according to the filtered signal DF and the identification code PN. The peak searcher 138 is connected to the serial parallel matched filter 136, receives the matching signal SP, and searches the peak of the matching signal SP to output the transmission delay time signal TD accordingly.

Referring to FIG. 4, a block diagram of the RAKE finger 152 is shown. The RAKE finger 152 includes an identification code generator 154 , a DLL 156 , and a despreader 158 . The identification code generator 154 is used for receiving the RAKE control signal Cr and the phase-lock control signal Cd and generating the identification code PN1 accordingly. The delay locked loop (Delay Locked Loop, DLL) 156 is used for receiving the exchange signal S1 and the identification code PN1 and outputting the phase locking control signal Cd accordingly to control the phase of the identification code PN1. The despreader 158 is used for receiving the switching signal S1, despreading the switching signal S1 according to the identification code PN1, and outputting a despreading signal R.

The above is a description of the structure of the RAKE receiving device of the present invention, and a further description of the operation flow is as follows. Referring to FIG. 5 , it shows a schematic diagram of the operation of the RAKE finger and the tracking unit 150 . In this figure a base station with two antenna elements and three communication links in operation is taken as an example for further illustration. The switching unit 140 receives digital signals D( 1 ) and D( 2 ) from different antennas, wherein each digital signal D includes spread spectrum signals transmitted by respective communication links. The switch unit 140 feeds the digital signals D( 1 ) and D( 2 ) into the plurality of RAKE fingers 152 according to the switch control signal Cw1 . For example, the spread spectrum signals transmitted by the communication link (1), communication link (2) and communication link (3) in the digital signal D(1) respectively include 2, 1 and 1 multipath components to be processed signal, so the switching unit 140 feeds the digital signal D(1) into four Rake fingers, so that each Rake finger 152 processes a multipath signal to be processed; the communication link in the digital signal D(2) ( 1), the spread spectrum signals transmitted by the communication link (2) and the communication link (3) each include 1, 1 and 2 multipath component signals to be processed, so the switching unit 140 converts the digital signal D(2) Feed 4 Rick fingers. When each Rake finger 152 demodulates the received multipath component signal according to the Rake control signal Cr, each output despread signal R and feed it into the switching unit 160, and the switching unit 160 will despread the signals belonging to the same communication link The frequency signal R is fed into the same combination unit 170, so that the combination unit 170 combines the received despread signal R and outputs it. Traditionally, the number of multipath component signals to be processed by a communication link is set to a predetermined value, so the number of rake fingers 152 allocated to each communication link is fixed. However, not every communication link needs to process as many multipath component signals as the predetermined number, so the rake fingers 152 are not effectively utilized. In the present invention, the rake control unit 200 individually determines the number of multipath component signals that each communication link needs to process according to the search result of the search unit 130, and allocates the rake fingers 152 accordingly, so the present invention is dynamic Allocating the Rick fingers 152 can improve the use efficiency of the Rick fingers 152 .

Referring to FIG. 6, a state transition diagram of a communication link is shown. The search unit 130 includes a search queue Q. The search queue Q may include multiple sub-queues corresponding to different priorities. Here, a high-priority sub-queue Qh and a low-priority sub-queue Q1 are taken as an example. When a communication link is established, the rake control unit 200 generates a search request accordingly and puts it into the high priority subqueue Qh or the low priority subqueue Qh in the search queue Q according to the priority of the search request. Sub-queue Q1, as shown in step 602. The rake control unit 200 processes the search requests in the search queue Q sequentially. When the search request of a communication link is processed for the first time, it enters the preliminary search state, one of the antenna units 101 is connected to the search unit 130, and the search unit 130 initially searches for multipath component signals, as shown in step 604 . Algorithms that are less precise, but more efficient, can be used in the preliminary search. Then, check whether the search unit 130 is busy, as shown in step 606, if not, execute step 607, and if yes, execute step 610. In step 607, enter the re-search state, one of the antenna units 101 is connected to the search unit 130, and the search unit 130 re-searches for multipath component signals. Algorithms that are less efficient but have more accurate results can be used when re-searching. The search unit 130 receives the digital signal D and re-searches the multipath component signal of the communication link included in the digital signal D corresponding to the search request according to the search request, and outputs a transmission delay time signal TD accordingly, and then performs step 610 . In step 610, the quality of the signal output by the rake receiver 110 is monitored. Check whether the communication link is terminated, as shown in step 612, if yes, then end the method, if not, then execute step 614. In step 614, it is decided whether to search again according to the result monitored in step 610, if not, then return to step 610 and continue to monitor the signal quality output by the rake receiving device 110, if yes, then search request according to its priority The weight is placed in the search queue Q and enters a waiting state, as shown in step 616. When the search request is processed, it enters the re-search state (step 607).

The rake receiving device and method disclosed in the above embodiments of the present invention have the following advantages:

1. Multiple antenna units share one search unit, so the complexity of the system can be reduced.

2. Propose a method of sharing one search unit, use search queues with different priorities, and use different algorithms under different requests to optimize the performance of the system.

3. The number of RAKE fingers allocated to each communication link is allocated dynamically, so the use efficiency of the RAKE fingers can be improved.

In summary, although the present invention has been disclosed with a preferred embodiment, it is not intended to limit the present invention, and any person skilled in the art can still make various modifications without departing from the spirit and scope of the present invention. change or modification. Therefore, the protection scope of the present invention shall prevail as defined by the appended claims.

Claims (11)

1. A kind of rake receiving device, is used for wireless spread spectrum communication system, and this wireless spread spectrum communication system comprises base station and a plurality of mobile stations, and these mobile stations set up a wireless communication link (radio link) with this base station respectively to send Spread spectrum signals including a plurality of information bits, these spread spectrum signals are transmitted in an environment with multipath interference, so that a plurality of multipath component signals are generated in these spread spectrum signals, the base station includes a plurality of antenna elements, and the antennas The unit receives a wireless signal and outputs a digital signal, the device consists of: a multiplexing unit connected to the antenna units for receiving the digital signals and selecting an output digital input signal from among the digital signals according to a multiplexing control signal; A search unit, connected with the multiplexing unit, is used to receive the digital input signal, and find the delay time corresponding to the multipath component signals contained in the communication link in the digital input signal according to a search control signal and according to to output a transmission delay time signal; A first switching unit, including a plurality of input terminals and a plurality of output terminals, these input terminals are respectively connected to the antenna units, and are used to receive the digital signals and output a plurality of first switching signals according to the first switching control signal; A rake finger and tracking unit, comprising a plurality of rake fingers (rake fingers), these rake fingers are respectively connected to the output ends of the first switching unit, for receiving at most one of these first switching signals respectively and despreading the corresponding first switching signal according to a rake control signal and outputting a despreading signal after adjusting its transmission time delay; A second switching unit, connected to the rake fingers, receives the despread signals and switches a plurality of despread switching signals according to the second switching control signal; A combining unit, connected to the second switching unit, for combining the switched despread signals according to a channel signal and outputting a combined signal; A decoding unit, connected to the combining unit, receives the combined signal and extracts the information bits accordingly to output a decoded signal; A channel estimation unit (Channel Estimator), which is connected with these rake fingers and the combination unit, is used to estimate the channel characteristics of these despread signals and output the channel signal accordingly; and A rake finger control unit is the control center of the rake receiving device, and the multiplexing unit, the search unit, the first switching unit, the rake finger and tracking unit, the second switching unit, the combination unit . The decoding unit is connected to the channel estimation unit, and is used to output the multiplexing control signal, the search control signal, the first switching control signal and the second switching control signal. 2. The RAKE receiving device as claimed in claim 1, wherein the search unit comprises: a filter for receiving the digital input signal and outputting a filtered signal accordingly; an identification code generator for receiving the search control signal and generating an identification code accordingly; a serial parallel matched filter, connected to the filter and the identification code generator, for receiving the filtered signal and the identification code and outputting a matching signal accordingly; and A peak searcher is connected with the sequence parallel matcher, receives the matching signal, and outputs the transmission delay time signal after searching for the peak value of the matching signal. 3. The RAKE receiving device according to claim 1, wherein the RAKE finger comprises: An identification code generator for receiving the rake control signal and generating an identification code according to the rake control signal and a phase-lock control signal; A delay-locked loop (Delay Locked Loop, DLL), for receiving the first exchange signal and the identification code and outputting the phase-locked control signal accordingly to control the phase of the identification code; and A despreader is used to receive the first exchange signal, despread the first digital exchange signal according to the identification code, and output the despread signal. 4. The RAKE receiving apparatus as claimed in claim 1, wherein the combining unit uses a maximum ratio combining technique to combine the second switching signals according to the channel signal. 5. A control method for a shared search unit, used for a base station, the base station comprising a plurality of antenna units and a rake receiving device, these antenna units respectively receive a wireless signal and output a digital signal accordingly, the rake receiving device It is used to receive these digital signals and demodulate them into multiple information bits. The rake receiving device includes a search unit and a search queue. When a communication link is established, the rake receiving device generates a Search request (request) and put it into the search queue, the control method includes: selectively extracting the search request from the search queue; selectively connecting the antenna units to the search unit; The search unit receives the digital signal and searches for a multipath component signal included in the digital signal according to the search request, and outputs a transmission delay time signal accordingly; and Monitor the signal quality output by the rake receiver. 6. The control method as claimed in claim 5, wherein the search queue further includes a plurality of sub-queues corresponding to different priorities, and the search request is placed into one of the sub-queues according to the priority of the search request. 7. The control method as claimed in claim 5, wherein, in the monitoring step, if it is found that the signal quality output by the rake receiving device is not good, then the search is re-entered into the search queue. 8. A control method for a shared search unit, used for a base station, the base station comprising a plurality of antenna units and a rake receiving device, these antenna units respectively receive a wireless signal and output a digital signal accordingly, the rake receiving device It is used to receive these digital signals and demodulate them into multiple information bits. The rake receiving device includes a search unit and a search queue. When a communication link is established, the rake receiving device generates a Search request (request) and put it into the search queue, the control method includes: selectively extracting the search request from the search queue; Enter a preliminary search state, at this time, one of these antenna units is connected to the search unit, and the search unit performs preliminary search for multipath component signals according to the search request and an algorithm suitable for preliminary search; Enter a re-search state, at this time, connect one of these antenna units to the search unit, and re-search the multipath component signal by the search unit according to the search request and an algorithm suitable for re-search; monitor the signal quality output by the rake receiving device; and Enter a waiting state, at this time, put the search request into the search queue, and enter the re-search state when the search request is processed. 9. The control method as claimed in claim 8, wherein the search queue further includes a plurality of sub-queues corresponding to different priorities, and the search request is placed into one of the sub-queues according to the priority of the search request. 10. The control method as claimed in claim 9, wherein, in the monitoring step, if it is found that the signal quality output by the rake receiving device is not good, a search request is regenerated and placed into one of the sub-queues according to its priority . 11. The control method as claimed in claim 8, wherein in the monitoring step, if it is found that the quality of the signal output by the rake receiving device is not good, a new search request is generated and put into the search queue according to its priority.

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