Background technology
In spread spectrum radio communications system (wireless spread spectrum communicationsystem), for example be the more location (Code Division Multiplexing Access of demal, CDMA) system, mobile radio station (Mobile Station, MS) with base station (Base Station, BS) set up communication link (radio, link) must be the time to unique identifier (Pseudo-NoiseCode of base station requests, PN Code), different mobile radio stations uses different identification codes to transmit information bit (information bit), and the base station of receiving terminal also is the wireless signal that comes demodulation to receive according to the employed identification code of mobile radio station, so that a plurality of mobile radio station can utilize same channel to transmit signal.Yet having multipath in the transmission course disturbs the situation of (multipath) to take place, multipath disturbs and is meant that signal is after the transmitting terminal emission, signal arrives receiving terminal through the path of one or more, for example be through the reflection of building in the city or atmospheric reflection etc., making the received signal of receiving terminal is not only to arrive via a directapath, also comprise the signal that arrives via other path, have the time difference of transmission between these multipath compositions (multipath component) signal.With reference to Fig. 1, wherein express the time delay power spectrum that contains the multipath component signal that the base station receives.Multipath component signal P1, P2 and P3 are arranged among this figure, and these three multipath component signals are all represented same information bit, for no other reason than that the feasible asynchronism(-nization) that arrives of the cause that multipath disturbs.Multipath component signal P1, P2 and P3 propagation delay time among the figure are respectively t1, t2 and t3.
In the spread spectrum radio communications system, rake reception device (rake receiver) is applicable to the demodulating equipment (demodulator) of multi-path transmission environment, and the wireless signal that is used for that each antenna is received demodulates the information bit merging output that each mobile radio station sends.Generally, rake reception device comprises a plurality of rake fingers (rake finger) and assembled unit (combiner).Each rake finger is to be used to receive a multipath component signal, will export after its time difference of it adjustment and the demodulation.Assembled unit for example is to utilize the signal that belongs to same communication link in the output signal of max ratio combined technology (maximum ratio combining technique) with rake finger to be made up, to obtain maximum signal to noise ratio (signal tonoise ratio, S/N ratio), so that bit error rate (BER) (bit error rate) reduces.In order to make rake reception device that best usefulness is arranged, need to use two kinds of Predicting Techniques: first kind is the propagation delay time information that obtains each multipath component signal, so that each rake finger can correctly carry out despreading with the signal that receives.Second kind of technology is to obtain the information of the characteristics of channel such as the amplitude of each multipath component signal and phase place, so that assembled unit can be done optimized combination with each multipath component signal of same communication link according to this.
Summary of the invention
In view of this, the purpose of this invention is to provide a kind of rake reception device and method, to demodulate the information bit that is transmitted in the transmission environment that disturbs at the tool multipath.
According to one object of the present invention, propose a kind of rake reception device, being summarized as follows of this device: rake reception device is to be used for spread spectrum radio communications system, and this spread spectrum radio communications system comprises base station and a plurality of mobile radio station.These mobile radio stations are set up wireless communication link (radio link) comprises a plurality of information bits with transmission spread-spectrum signal with the base station respectively.These spread-spectrum signals are to transmit in the environment that the tool multipath disturbs, and make a plurality of multipath component signals be created in each spread-spectrum signal.The base station comprises a plurality of antenna elements, and each antenna element receives wireless signal and exports digital signal.Rake reception device comprises multiplex (MUX) unit, search unit, first crosspoint, second crosspoint, rake finger and tracking cell, Rake control unit, assembled unit, decoding unit and channel estimation unit.The multiplex (MUX) unit is connected with each antenna element, is used to receive each digital signal, and selects an output digital input signals according to multiplex's control signal from these digital signals.Search unit is connected with the multiplex (MUX) unit, is used to receive digital input signals, and seeks in the digital input signals corresponding to the time of delay of the multipath component signal that this communication link comprised and in view of the above with output propagation delay time signal according to search control signal.First crosspoint comprises a plurality of inputs and a plurality of output, and these inputs are connected with these antenna unit respectively, is used to receive these digital signals and exports a plurality of first switching signals according to the first exchange control signal.Rake finger and tracking cell, comprise a plurality of rake fingers (rake finger), these rake fingers are connected with the output of first crosspoint respectively, are used for receiving to respectively many one first switching signals and according to Rake control signal despreading signal of output with the first switching signal despreading of correspondence and after adjusting its propagation time delay.Second crosspoint is connected with these rake fingers, receives these despreading signals and according to the signal behind the second exchange control signal exchange despreading.Assembled unit is connected with second crosspoint, is used for according to the switching signal combination back output composite signal of channel signal after with these despreadings.Decoding unit is connected with assembled unit, receives composite signal also in view of the above to extract information bit with the output decoder signal.Channel estimation unit (Channel Estimator) is connected with assembled unit with these rake fingers, is used to estimate the characteristic of channel of these despreading signals and delivery channel signal according to this.The rake finger control unit is the control centre of rake reception device, be connected with channel estimation unit with multiplex (MUX) unit, search unit, first crosspoint, rake finger and tracking cell, second crosspoint, assembled unit, decoding unit, be used to export multiplex's control signal, search control signal, the first exchange control signal and the second exchange control signal.
According to another object of the present invention, a kind of control method of shared search unit is proposed.This control method may further comprise the steps: at first, optionally extract searching request (raquest) from search queue.Then, optionally antenna element is connected with search unit.Then, the search unit receiving digital signals and according to searching request with the included multipath component signal of search digital signal and export the propagation delay time signal according to this.Then, monitor the signal quality of rake reception device output.
For above-mentioned purpose of the present invention, feature and advantage can be become apparent, embodiments of the invention are described in detail below in conjunction with accompanying drawing.
Description of drawings
Fig. 1 represents the time delay power spectrum that comprises the multipath component signal that the base station receives;
Fig. 2 is a kind of rake reception device block diagram of expression according to a preferred embodiment of the invention;
Fig. 3 is the block diagram of expression search unit;
Fig. 4 is the block diagram of expression rake finger and tracking cell.
Fig. 5 is the running schematic diagram of expression rake finger and tracking cell.
Fig. 6 is the state transition diagram of expression communication link.
The explanation of label in the accompanying drawing
101: antenna element
110: rake reception device
120: the multiplex (MUX) unit
130: search unit
132: filter
134,154: the identification code generator
136: sequence matched filter arranged side by side
138: peak portion searcher
140,160: crosspoint
150: rake finger and tracking cell
158: despreader
170: assembled unit
180: decoding unit
190: channel estimation unit
200: the Rake control unit
Execution mode particularly
With reference to Fig. 2, wherein represent a kind of rake reception device block diagram in accordance with a preferred embodiment of the present invention.Rake reception device 110 is used for spread spectrum radio communications system, and spread spectrum radio communications system comprises base station and a plurality of mobile radio station.These mobile radio stations are to set up wireless communication link (radiolink) to send out the spread-spectrum signal that comprises a plurality of information bits with the base station respectively, these spread-spectrum signals transmit in the environment that the tool multipath disturbs, and make a plurality of multipath component signals be created in each spread-spectrum signal.The base station comprises a plurality of antenna elements 101, and each antenna element 101 receives wireless signal and exports digital signal D.Rake reception device 110 comprises multiplex (MUX) unit 120, search unit 130, crosspoint 140, rake finger and tracking cell 150, crosspoint 160, assembled unit 170, decoder 180, channel estimation unit (Channel Estimator) 190 and rake finger control unit 200.Multiplex (MUX) unit 120 is to be connected with these antenna unit 101, is used to receive these digital signals D, and selects an output digital input signals DI according to multiplex's control signal Cm from these digital signals D.Search unit 130 is connected with multiplex (MUX) unit 120, be used to receive digital input signals DI, and seek the time of delay of these included multipath component signals of communication link that digital input signals DI comprised and export propagation delay time signal TD according to this corresponding to search control signal Cs.With Fig. 1, the propagation delay time, signal TD was the information corresponding to time t1, t1 and t3.Because the required computing capability of search unit 130 is very complicated, therefore the present invention makes a plurality of antenna element 101 shared search units 130 drop to minimum with the number with search unit 130, and can reduce the complexity of system, the control method of this shared search unit 130 will be explained below.
Crosspoint 140 is connected with these antenna unit, is used to receive these digital signals D and exports a plurality of switching signal S1 according to exchange control signal Cw1.Rake finger and tracking cell 150 comprise a plurality of rake fingers (rake finger) 152, these rake fingers 152 are the outputs that are connected respectively to crosspoint 140, be used for receiving to respectively many switching signal S1, and according to Rake control signal Cr output despreading signal R with the switching signal S1 despreading of correspondence and after adjusting propagation time delay.Crosspoint 160 is connected with these rake fingers 152, receives these despreading signal R and exports many switching signals S2 according to exchange control signal Cw2.Assembled unit 170 is connected with crosspoint 160, is used for according to channel signal E these switching signals S2 combination back output composite signal SC.Decoding unit 180 is connected with assembled unit 170, receives composite signal SC and extract mobile radio station according to this information bit that is sent, with output decoder signal DC.Channel estimation unit 190 is connected with assembled unit 170 with rake finger and tracking cell 150, is used to estimate the characteristic of channel of despreading signal R and delivery channel signal E according to this.
Rake finger control unit 200 is the control centres for rake reception device 110, be connected with channel estimation unit 190 with multiplex (MUX) unit 120, search unit 130, crosspoint 140, rake finger and tracking cell 150, crosspoint 160, assembled unit 170, decoding unit 180, be used to export multiplex's control signal Cm so that different digital signal D feed-in search units 130; Output search control signal Cs is to specify the multipath component signal of one of search unit 130 these communication links of search; Control signal Cw1 is so that the multipath component signal of each communication link corresponds respectively to one of these rake fingers 152 in the output exchange; Control signal Cw2 is so that belong to the despreading signal R feed-in assembled unit 170 of same mobile radio station in the output exchange.
With reference to Fig. 3, wherein represent the block diagram of search unit 130.Search unit 130 comprises filter 132, identification code generator 134, sequence matched filter 136 arranged side by side and peak portion searcher 138.Filter 132 is used to receive digital input signals DI, and exports filtering signal DF according to this.Identification code generator 134 is used to receive search control signal Cs and produces identification code PN according to this.Sequence matched filter 136 arranged side by side is connected with filter 132 and identification code generator 134, is used for according to filtering signal DF and identification code PN output matched signal SP.Peak portion searcher 138 is connected with sequence matched filter 136 arranged side by side, receives matched signal SP, and exports propagation delay time signal TD according to this after the peak portion of search matched signal SP.
With reference to Fig. 4, wherein represent the block diagram of rake finger 152.Rake finger 152 comprises identification code generator 154, delay locked loop device 156, reaches despreader 158.Identification code generator 154 is used to receive Rake control signal Cr and phase-locked control signal Cd and produces identification code PN1 according to this.(Delay Locked Loop, DLL) 156 are used to receive switching signal S1 and identification code PN1 and export the phase place of phase-locked control signal Cd with control identification code PN1 according to this delay phase-locked loop road device.Despreader 158 be used to receive switching signal S1 and according to identification code PN1 with switching signal S1 despreading and export despreading signal R.
The above is the structure explanation for rake reception device of the present invention, and it is described that further operating process is described as follows literary composition.With reference to Fig. 5, wherein represent the operation chart of rake finger and tracking cell 150.Have the base station of two antenna elements in the figure, and three communication links that have in the work are that example is further described.Crosspoint 140 receives the digital signal D (1) and D (2) from different antennae, wherein, and the spread-spectrum signal that each digital signal D comprises each communication link simultaneously and transmitted.Crosspoint 140 is according to exchanging control signal Cw1 with digital signal D (1) and a plurality of rake fingers 152 of D (2) feed-in.For example the communication link (1) among the digital signal D (1), communication link (2) respectively include 2,1 and 1 pending multipath component signals with the spread-spectrum signal that communication link (3) is transmitted, therefore crosspoint 140 is with 4 rake fingers of digital signal D (1) feed-in, so that each rake finger 152 is respectively handled a pending multi-path signal; Communication link (1) among the digital signal D (2), communication link (2) respectively include 1,1 and 2 pending multipath component signal with the spread-spectrum signal that communication link (3) is transmitted, so crosspoint 140 is with 4 rake fingers of digital signal D (2) feed-in.After each rake finger 152 is according to the multipath component signal demodulation of Rake control signal Cr with reception, respectively export despreading signal R and feed-in crosspoint 160, crosspoint 160 is about to each and belongs to the same assembled unit 170 of despreading signal R feed-in of same communication link, so that assembled unit 170 is with the despreading signal R combination back output that receives.Be that number with the multipath component signal of a required processing of communication link is set at a predetermined value traditionally, so assigned rake finger 152 numbers of each communication link are fixed.Yet, be not a plurality of just like predetermined number of the multipath component signal of the required processing of each communication link, so rake finger 152 just is not used effectively.The present invention is the number that determines the multipath component signal of the required processing of each communication link with Rake control unit 200 according to the result of search unit 130 search individually, and distribute rake finger 152 according to this, therefore the present invention is dynamic rake finger 152, the service efficiency that can promote rake finger 152 of distributing.
With reference to Fig. 6, wherein represent the state transition diagram of communication link.Search unit 130 comprises a search queue Q, and search queue Q can comprise a plurality of subqueues, and each subqueue is example at this with a high priority subqueue Qh and a low priority subqueue Q1 corresponding to different priority.When a communication link is set up, Rake control unit 200 promptly produces a searching request (request) according to this and according to the priority of this searching request it is inserted high priority subqueue Qh or low priority subqueue Q1 among the search queue Q, shown in step 602.Rake control unit 200 can be handled the searching request in search queue Q in regular turn.Enter preliminary search condition when the searching request of a communication link is for the first time processed, one of antenna element 101 is connected with search unit 130, and by search unit 130 preliminary search multipath component signals, shown in step 604.Though when preliminary search, can adopt than inaccuracy, more efficient operation method.Then, check whether search unit 130 is busy, and shown in step 606, if not, then execution in step 607, if then execution in step 610.In step 607, enter search condition again, one of antenna element 101 is connected with search unit 130, and searches for the multipath component signal again by search unit 130.But though when searching for again, can adopt the more accurate operation method of more inefficent result.Search unit 130 receiving digital signals D and according to searching request with search for again digital signal D included corresponding to the multipath component signal of the communication link of searching request and export propagation delay time signal TD execution in step 610 then according to this.In step 610, monitor the signal quality of rake reception device 110 outputs.Check whether to finish communication link, shown in step 612, if, method ends then, if not, then execution in step 614.In step 614, whether to search for again according to the result's decision that is monitored in the step 610, if not, then get back to the signal quality that step 610 continues to monitor rake reception device 110 outputs, if, then searching request is inserted among the search queue Q according to its priority, and entered wait state, shown in step 616.Enter again search condition (step 607) when this searching request is processed by the time.
Rake reception device and method that the above embodiment of the present invention is disclosed have the following advantages:
Therefore one, the shared search unit of a plurality of antenna elements can lower the complexity of system.
Two, propose the method for a shared search unit, use search queue, under the difference request, adopt different operation methods to come the usefulness of optimization system with different priority.
Three, the rake finger number that is assigned to of each communication link is a dynamic assignment, so the service efficiency of rake finger can improve.
In sum, though the present invention discloses with a preferred embodiment, it is not to be used to limit of the present invention, and any professional and technical personnel still can make various changes or modification under the situation that does not break away from the spirit and scope of the present invention.Therefore, protection scope of the present invention is as the criterion with the scope that accompanying claims were defined.