DEVICE AND METHOD FOR GENERATING PN SEQUENCE IN CDMA COMMUNICATION SYSTEM

Abstract: In a code division multiple access (CDMA) communications system, a PN sequence generating device (310) is provided to generate a PN sequence by interleaving (322, 332, 342) of cyclically shifting the symbols of an orthogonal or biorthogonal code (320, 330, 340) in accordance with a pre-defined hopping pattern (360). A receiver receives simultaneous signals from a plurality of transmitters, where each transmitted signal is spread by a PN sequence generated from the same pre-defined hopping pattern. The receiver is able to differentiate the received signals from each transmitter by varying the amount of interleaving or cyclic shift in each transmitted signal. In the PN sequence generating device (310), an orthogonal symbol generating portion (320, 330, 340) cyclically shifts mutually orthogonal and periodic orthogonal code sequences, and an orthogonal symbol selector (350) selectively outputs the cyclically shifted orthogonal symbols according to a predetermined pattern.

Description: DEVICE AND METHOD FOR GENERATING PN SEQUENCE IN CDMA COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION 1. Field ofthe Invention The present invention relates generally to a Code Division Multiple Access System (CDMA), and more particularly, to a device and method for generating a PN (PseudoNoise) sequence by orthogonal code hopping. 2. Description of the Related Art Generally, symbols of an orthogonal or biorthogonal code are hopped according to a predetermined hopping pattern in each of a plurality of transmitters in an asynchronous CDMA base station to generate a PN sequence.. Asynchronous base stations can use PN sequences to allow a mobile station to identify them. A plurality of slots (e.g., 16 slots) are assigned to one frame. A period of hopped orthogonal Gold code is sent in each slot. Since the orthogonal Gold code hopping patterns are different in the plurality of slots, the mobile station can identify a corresponding base station. If the mobile station can detect the starting point of one frame, it can discriminate a base station from others by determining with how much offset from the frame starting point the orthogonal Gold code in each slot is periodically generated. - 2 - The PN sequence may be used for spread spectrum or scrambling in the case where a different orthogonal code is used for channel identification. A particular receiver may simultaneously receive signals from a corresponding transmitter as well as from transmitters communicating with other receivers. If the plurality of signals, which contain data symbols to be despread, share the same PN sequence and the same orthogonal code (e.g., Walsh code) for channel identification, the receiver will be able to simultaneously despread the signals but fail to recover the intended data symbols. In the case of a periodic PN sequence, data symbols cannot periodically be recovered. FIGs. 1A and IB are schematic views of conventional PN sequence generators based on orthogonal code hopping and orthogonal Gold code hopping, respectively. FIGs. IC and ID are schematic views of conventional PN sequence generators based on biorthogonal code hopping and biorthogonal Gold code hopping, respectively. FIGs. 2 A and 2B illustrate a case where a receiver simultaneously receives the same orthogonal or biorthogonal code from different transmitters using PN sequence generators, based on possibly different hopping patterns, and cannot discriminate between data symbols through despreading. When an orthogonal code other than a PN sequence is used for distinguishing a communication channel in a transmitter, only data symbols using the same channel identifying orthogonal code avoid discrimination since collision is occurred when the orthogonal code for generating PN sequence and the orthogonal code for channelization of two received signals are the same. As illustrated in FIGs. 2A and 2B, a PN sequence PN A of a transmitter A 210 and a PN sequence PN B of a transmitter B 260 are generated from the same orthogonal - 3 - code, however, each uses a different hopping pattern. In FIG. 2B, though an orthogonal code OC3 is simultaneously received from the transmitters A 210 and B 260 (See FIG. 2A), only the data symbol using a channel identifying orthogonal spreading code W2 in the orthogonal code OC3 is lost due to symbol collision. That is, all ofthe coincident symbols in the respective PN sequences which are identical cannot be recovered (i.e., OC3). If the strengths ofthe signals received from the respective transmitters A 210 and B 260 are equal, they cannot be discriminated. If one is far stronger than the other, the stronger signal can be discriminated. Orthogonal or biorthogonal codes for use in PN sequence generation include, but are not restricted to Walsh codes, Hardamard codes, Gold codes, and the like. Referring to FIG. 1 A, reference numeral 110 denotes a PN sequence generator, constructed in accordance with the prior art, based on orthogonal code hopping. Reference numerals 120, 130, and 140 are orthogonal symbol generators to generate orthogonal codes. A selector 150 selectively outputs orthogonal symbols generated from each of the respective orthogonal symbol generators 120 to 140 according to an orthogonal symbol hopping pattern provided by hopping pattern generator 160. The selector 150 outputs a PN sequence from the selected symbols. The orthogonal symbol hopping pattern generator 160 generates an orthogonal code hopping pattern under a predetermined rule. It is to be noted here that like reference numerals denote the same components in the drawings. FIG. IB is a schematic view of PN sequence generator based on - 4 - orthogonal Gold code hopping. In FIG. IB, the orthogonal symbol hopping pattern generator 160 determines an initial value for an nr-sequence (with a period of 2"- 1) generator 163. An initial value register 162 stores the determined initial value. Another πr-sequence generator 167 with a period of - 1 generates an mr-sequence having an initial value with no relation to the initial value stored in initial value register 162. This second generated initial value is stored in an initial value register 166. A Gold sequence is generated by exclusive-ORing the outputs ofthe two nr-sequence generators 163 and 167 by an exclusive-OR gate 164. To change the Gold sequence to an orthogonal Gold code, the operations of the nr-sequence generators 163 and 167 are stopped for one clock period if the status value, which is the stored value ofthe m-sequence generator 167, (additional explanation : Each m sequence generator generates (2 - 1) m sequences in one period. (2 - 1) sequences are also produced by adding the output values ofthe two m sequence generators symbol by symbol. To obtain 2 orthogonal Gold sequences from the (2 - 1) sequences, zero is inserted in a predetermined position ofthe (2 - 1) sequences where the status value, that is, initial value ofthe m sequence generator is identical to a reference value. Zero is inserted in the same position in the next period because the m sequence generator generates periodic m sequences. The reference value can be determined depending on where zero is to be inserted in an orthogonal Gold code sequence, and the insertion position can freely be predefined.) ofthe nr- sequence generator 167 is equal to a predetermined reference value as determined by comparator 169. Whenever the values are equal, a switch 168 normally connected to the output ofthe exclusive-OR gate 164 is switched to select a zero value for insertion into the Gold sequence. Otherwise, when the values are not equal, the nr-sequence generators 163 and 167 are operated again. FIG. IC is a schematic view of a conventional PN sequence generator based on biorthogonal code hopping, modified from the PN sequence generator based on orthogonal code hopping, (additional explanation: If there are 32 orthogonal symbol generators, each orthogonal symbol generator generates a coiTesponding orthogonal sequence periodically, and the hopping pattern of the orthogonal symbol hopping pattern 160 is 1 ,3,5,7,9,1 1 ,13,15,17,19,21,23,25,27,29,31,2,4,6,8,10,12,14,16,18,20,22,24,26,2 8,30,32, the biorthogonal symbol hopping pattern generator 170 generates one more bit in addition to the hopping pattern. This one bit may be MSB or LSB and indicates a sign + or -. By passing the additional bit through the XOR gate 190, not 32 PN sequences but 64 PN sequences are produced.) Given an orthogonal code set, the output of a biorthogonal symbol hopping pattern generator 170 is twice as long as the orthogonal symbol hopping pattern generator 160 output. The output of the biorthogonal symbol hopping pattern generator 170 passes through an exclusive-OR gate by a bit like MSB (Most Significant Bit) or LSB (Least Significant Bit), which are similar to the sign bit of the generated orthogonal code symbol. That is, the number of elements in biorthogonal code set is twice as large as that of orthogonal codes by adding signs + and - to the orthogonal codes, and to indicate the sign, one bit is additionally assigned to an orthogonal code number. FIG. ID illustrates biorthogonal Gold code hopping which illustrates a modification ofthe apparatus of FIG. IB for biorthogonal codes. - 6 - FIGs. 2A and 2B illustrate data symbol loss in a receiver which may occur when a plurality of transmitters use PN sequences generated from different transmitters which simultaneously transmit signals to the receiver, where each transmitter transmits one ofthe following conventional orthogonal codes: orthogonal, orthogonal gold, biorthogonal and biorthogonal gold code hopping. The transmitter A 210 generates the PN sequence PN A by hopping orthogonal or biorthogonal codes in a predetermined hopping pattern indicated by 220. Reference numeral 230 denotes data symbols ofthe PN sequence PN A to be used for spreading or scrambling. The transmitter B 260 generates the PN sequence PN B by hopping orthogonal or biorthogonal codes in a predetermined hopping pattern indicated by 270. Reference numeral 280 denotes data symbols ofthe PN sequence PN B to be used for spreading or scrambling. If signals from the transmitters A 210 and B 260 arrive at a receiver 200 at similar levels and share the same orthogonal symbols in their respective hopping patterns as shown in FIGs. 2A and 2B, it is difficult to discriminate one from the other. For example, as illustrated in FIG. 2a, orthogonal code OC3 is simultaneously received at the receiver causing a collision period. FIG. 2B is a magnified view of a symbol collision period. As illustrated in FIG. 2B, all data symbols are not damaged by the collision. Only the data symbols loaded on channels sharing the same channel identifying orthogonal code are lost as indicated by 232 and 274. Here, a Walsh code is used as an example. With reference to the example shown, only the data symbols sharing the same orthogonal code, that is, Walsh code W2, are lost among the totality of data symbols in each of the respective communication channels (i.e., Wl, W2 - 7 - and W3). Further, if a hopping pattern is repeated periodically, data loss will also be periodic. SUMMARY OF THE INVENTION A general object ofthe present invention is to provide a PN sequence (i.e., orthogonal code) generating device and PN sequence generating method in a CDMA communication system which can overcome the data collision problems described above. Another object ofthe present invention is to provide a device and method for generating a PN sequence (i.e., orthogonal code) to overcome data collision problems by performing a cyclic shift on the symbols of an orthogonal code according to a hopping pattern. A further object ofthe present invention is to provide a device and method for generating a PN sequence (i.e., orthogonal code) based on orthogonal or biorthogonal code hopping to prevent simultaneous despreading of data symbols received from a plurality of transmitters. According to the present invention, as embodied and broadly described herein, there is provided a PN sequence generating device and method in a CDMA communication system. In the PN sequence generating device, an orthogonal symbol generating portion cyclically shifts mutually orthogonal and/or periodic orthogonal code sequences, and an orthogonal symbol selector selectively outputs the cyclically shifted orthogonal symbols according to a predetermined pattern. BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages ofthe present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: FIGs. 1A to ID are schematic views of conventional PN sequence generators based on orthogonal, orthogonal Gold, biorthogonal, and biorthogonal Gold code hopping, respectively; FIGs. 2 A and 2B illustrate data symbol loss in a receiver due to collision between signals generated from different transmitters based on conventional orthogonal, orthogonal Gold, biorthogonal, or biorthogonal Gold code hopping; FIGs. 3 A to 3F are schematic views of PN sequence generators based on orthogonal, orthogonal Gold, biorthogonal, and biorthogonal Gold code hopping according to embodiments ofthe present invention; FIGs. 4A and 4B are views illustrating preservation of data symbols in a receiver by preventing collision between signals generated from different transmitters based on the orthogonal, orthogonal Gold, biorthogonal, or biorthogonal Gold code hopping according to the embodiments ofthe present invention; FIGs. 5A to 5H illustrate orthogonal code sets each having orthogonal symbols subject to the same cyclic shift or interleaving in order to maintain orthogonality among the orthogonal symbols to be hopped according to a hopping pattern; and FIGs. 6 A and 6B respectively illustrate a reference orthogonal code set and an orthogonal code set in which each orthogonal code has orthogonal symbols to be hopped according to a hopping pattern, which are subject to - 9 - different cyclic shift or interleaving and thus lose mutual orthogonality. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is now make in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. It is to be noted that like reference numerals denote the same components in the drawings. FIGs. 3A to 3F are schematic views of PN sequence (orthogonal code) generators based on hopping, delay, and interleaving of orthogonal or biorthogonal codes according to embodiments ofthe present invention. FIG. 3 A illustrates a PN sequence (orthogonal code) generator according to a first embodiment ofthe present invention. Referring to FIG. 3 A, an orthogonal symbol hopping pattern generator 360 generates a predetermined orthogonal code hopping pattern. A delay controller 370 generates a delay control signal in accordance with the hopping pattern received from the orthogonal symbol hopping pattern generator 360. The present invention envisions similar apparatus, such as that described in FIG. 3A, to be deployed at a plurality of base stations whereby signal collision is prevented by setting different hopping patterns and delay amounts at each base station. Orthogonal symbol generators 320 to 340 generate corresponding orthogonal symbols to be hopped. That is, each orthogonal symbol generator generates a code sequence coiTesponding to a specific Walsh code number. Orthogonal symbols output from generators 320 to 340 are supplied to one of the respective delays 325 to 3451. An orthogonal symbol selector 350 selects one ofthe delayed orthogonal - 10 - symbols received from the delays 325 to 345. The amount of delay and particular symbol selected are made under the control ofthe orthogonal symbol hopping pattern generator 360. In operation, the orthogonal symbol generators 320 to 340 each generate an orthogonal code sequences as shown in FIG. 5A and 6A. The code sequences are hopped according to a hopping pattern defined by symbol hopping pattern generator 360. The hopping pattern represents the order in which code sequences are sent. The delays 325 to 345 delay the outputs ofthe orthogonal symbol generators 320 to 340 to be cyclically shifted by a number of symbols, predetermined by a delay controller 370. What the cyclically shifted means is as follows : (Al A2A3 * A10)(A1A2A3 * A10) is changed to (A2A3 * A10A1)(A2A3 * A10 Al) where (*)is the period. The orthogonal symbol selector 350 selectively outputs the delayed orthogonal symbols received from each of the respective delays 325 to 345 according to hopping pattern information received from the orthogonal symbol hopping pattern generator 360 to thereby produce a PN sequence. FIG. 5 A illustrates an exemplary reference orthogonal code set, and FIGs. 5B, 5C, and 5D are related figures which illustrate the code set of FIG. 5a modified while maintaining orthogonality. The code sets of FIGs. 5B, 5C, and 5D are obtained by cyclically shifting the reference orthogonal code set in the PN sequence generator, as shown in FIG. 3A. In the drawings, shaded portions indicate cyclically shifted chips in the respective rows, as determined by the delay controller 370. FIG. 3B is a schematic view of a PN sequence generator according to a - 11 - second embodiment ofthe present invention. Referring to FIG. 3B, the orthogonal symbol hopping pattern generator 360 generates predetermined hopping pattern information of an orthogonal code. An interleaver controller 380 generates an interleaving control signal based on the hopping pattern information received from the orthogonal symbol hopping pattern generator 360. The orthogonal symbol generators 320 to 340 generate their corresponding orthogonal symbols, that is, rows of reference orthogonal symbols (i.e., orthogonal code sequences), shown in FIG. 5A or 6A, to be hopped. Interleavers 322 to 342 interleave orthogonal symbols received from the orthogonal symbol generators 320 to 340 under the control ofthe interleaver controller 380. The orthogonal symbol selector 350 selectively outputs the interleaved orthogonal symbols under the control ofthe orthogonal symbol hopping pattern generator 360. In operation, the orthogonal symbol generators 320 to 340 of FIG. 3B generate orthogonal symbols to be hopped according to a hopping pattern as in FIG. 3 A. The orthogonal symbol hopping pattern generator 360 generates the hopping pattern information of an orthogonal code. The interleaver controller 380 controls interleaving ofthe orthogonal symbols, and the interleavers 322 to 342 interleave the orthogonal symbols received from the orthogonal symbol generators 320 to 340 in chip units according to the hopping pattern. This interleaving scheme is different in each base station, thereby preventing signal collision. The orthogonal symbol selector 350 selectively outputs the symbols received from the interleavers 322 to 342 according to the hopping pattern information defined by hoping pattern generator 360. FIGs. 5E to 5H illustrate modified orthogonal code sets with - 12 - orthogonality maintained, which are obtained by interleaving the reference orthogonal code sets of FIG. 5 A in a PN sequence generator such as the one shown in FIG. 3B. Shaded portions indicate interleaved chips, that is, columns locations that have been exchanged. In the present embodiment, the delays 325 to 345 of FIG. 3 A are replaced by the interleavers 322 to 342 of FIG. 3B, resulting in the same effects in generating a PN sequence. Control of the delays 325 to 345 and the interleavers 322 to 342 over a different number of orthogonal symbols in each orthogonal code produces modified sequences shown in FIG. 6B, which may lose orthogonality since the modified code symbol is not included in the orthogonal code set. FIG. 3C is a schematic view of a PN sequence generator based on orthogonal Gold code hopping according to a third embodiment of the present invention. Referring to FIG. 3C, the orthogonal symbol hopping pattern generator 360 generates hopping pattern information of an orthogonal code. The interleaver controller 380 generates an interleaving control signal according to the hopping pattern information received from the orthogonal symbol hopping pattern generator 360. An initial value register 366 stores an initial value, and an m-sequence generator 367 reads the initial value from the initial value register 366 and generates a first nr-sequence corresponding to the supplied initial value. An initial value register 362 stores the hopping pattern information as an initial value, and a second nr-sequence generator 363 generates a second nr-sequence coiTesponding to the initial value received from the initial value register 362. Therefore, the nr-sequence generators 363 and 367 output first and second m- sequences, different from each other as a consequence of different supplied initial values. An exclusive-OR gate 364 exclusive-ORs the outputs of the nr- sequence generators 363 and 367 to produce a Gold sequence. A comparator - 13 - 369 compares the status value ofthe m-sequence generator 367 with a predetermined value and generates a switch controlling signal according to the comparison result. A switch 368 is selectively coupled to both a zero input value 365 and the output ofthe exclusive-OR gate 364. The switch 365 selects the zero input for one clock period by the switch controlling signal received from the comparator 369 if the output ofthe nr-sequence generator 367 is equal to the predetermined value. Otherwise, if they are different, the switch 368 selects the output of the exclusive-OR gate 364, that is, the Gold sequence. The switch 368 may be implemented as a multiplexer. The interleaver controller 380 generates a control signal for interleaving the symbols received from the switch 368 according to the hopping pattern information received from the orthogonal symbol hopping pattern generator 360. The interleaver 322 interleaves the output ofthe switch 368 under the control ofthe interleaver controller 380 to produce a PN sequence. In operation, the orthogonal symbol hopping pattern generator 360 determines an initial value for the nr-sequence (with a period of 2 n - 1) generator 363. The determined initial value is stored in the register 362. Another nr- sequence, generator 367 (with a period of 2 n - 1) generates an m-sequence whose initial value is wholly unrelated to the orthogonal symbol hopping pattern generator 360. The initial value for m-sequence generator 367 is stored in the register 366. The outputs ofthe two nr-sequence generators 363 and 367 are exclusive-ORed to produce Gold sequence as output from the exclusive-OR gate 364. To generate an orthogonal Gold code from the Gold sequence, the comparator 369 compares the status value ofthe nr-sequence generator 367 with a predetermined value. If they are equal, the nr-sequence generators 363 and 367 are stopped for one clock period, and the switch 368 inserts a zero value into - 14 - the Gold sequence for the one clock period. If they are different, however, the Gold sequence is selected by the switch 368. Then, the interleaver 322 interleaves the output ofthe switch 368 under the control ofthe interleaver controller 380. As an exemplary output of this process, FIGs. 5E - 5H illustrate interleaved versions of FIG. 5 A. FIG. 3D is a schematic view of a PN sequence generator according to a fourth embodiment ofthe present invention. Referring to FIG. 3D, a biorthogonal symbol hopping pattern generator 358 generates hopping pattern information. The delay controller 370 generates a delay control signal in accordance with the hopping pattern received from the biorthogonal symbol hopping pattern generator 358. There is no necessity in the present invention for configuring the orthogonal(biorthogonal) symbol hopping pattern generator in relation to an interleaver controller for determining an interleaving pattern or a delay controller for controlling a delay amount. In other words, the orthogonal(biorthogonal) symbol hopping pattern generator may independently be provided with a delay amount or an interleaving pattern. Yet, each base station should have a different delay amount or interleaving pattern. Therefore, since each base station has a different hopping pattern, the base station can have a different delay amount or interleaving pattern if it uses a delay amount or interleaving pattern corresponding to its unique hopping pattern in an embodiment ofthe present invention. The orthogonal symbol generators 320 to 340 generate corresponding orthogonal code sequence to be hopped. The delays 325 to 345 delay orthogonal symbols received from the orthogonal symbol generators 320 to 340 under the control of the delay controller 370. An orthogonal symbol selector 350 selects one ofthe - 15 - delayed orthogonal symbols received from the delays 325 to 345 at every orthogonal code sequence duration time under the control ofthe biorthogonal symbol hopping pattern generator 358. The exclusive-OR gate 390 exclusive- ORs the orthogonal symbol sequence received from the orthogonal symbol selector 350 and code bits ofthe biorthogonal code hopping pattern information to produce a PN sequence. It is apparent, therefore, that the PN sequence generator of FIG. 3D is operationally equivalent to the PN sequence generator based on orthogonal code hopping. The orthogonal symbol generators 320 to 340 generate orthogonal symbols to be hopped according to a hopping pattern, generated by the symbol hopping pattern generator 358. The delays 325 to 345 delay the outputs of the orthogonal symbol generators 320 to 340 to be cyclically shifted, where a delay controller 370 determines how many symbols to delay. The orthogonal symbol selector 350 selectively outputs the delayed orthogonal symbols, one orthogonal code sequence period unit, received from the delays 325 to 345 according to hopping pattern information received from the biorthogonal symbol hopping pattern generator 358 to thereby produce a PN sequence. Given that the orthogonal symbol generators 320 to 340 generate orthogonal symbols ofthe same length as in previous embodiments the output ofthe biorthogonal symbol hopping pattern generator 358 is twice as long as that ofthe orthogonal symbol hopping pattern generator 360 described in FIGs. 3A - 3C. The exclusive OR gate 390 performs an exclusive -OR operation on the PN sequence output from orthogonal symbol selector 350 and sign components (i.e., plus and minus) from the hopping pattern information by a bit like MSB or LSB. Thus, the number of resulting PN sequences is twice as large as that ofthe PN sequences (orthogonal codes) in FIG. 3 A because sign components ( + and -) are added to the latter. - 16 - As a result, the probability decreases that different base stations use the same PN sequence cyclically shifted to the same amount in the same time period. FIG. 3E is a schematic view of a PN sequence generator according to a fifth embodiment of the present invention. Referring to FIG. 3E, the biorthogonal symbol hopping pattern generator 358 generates hopping pattern information of an orthogonal code. The interleaver controller 380 generates an interleaving control signal based on the hopping pattern information received from the biorthogonal symbol hopping pattern generator 358. That is, signal collision is prevented by using different hopping patterns and interleaving schemes in different base stations. The orthogonal symbol generators 320 to 340 generate their corresponding orthogonal symbols to be hopped. The interleavers 322 to 342 interleave orthogonal symbols received from the orthogonal symbol generators 320 to 340 under the control ofthe interleaver controller 380. The orthogonal symbol selector 350 selectively outputs the interleaved orthogonal symbols under the control of the biorthogonal symbol hopping pattern generator 358. The exclusive-OR gate 390 exclusive-ORs the orthogonal symbol received from the orthogonal symbol selector 350 and the biorthogonal code hopping pattern information to produce a PN sequence. Therefore, the PN sequence generator of FIG. 3E is a modification ofthe PN sequence generator based on orthogonal code hopping. In operation, the orthogonal symbol generators 320 to 340 generate orthogonal symbols to be hopped according to a hopping pattern. The biorthogonal symbol hopping pattern generator 358 generates the hopping pattern information of an orthogonal code. The interleaver controller 380 controls interleaving ofthe orthogonal symbols, and the interleavers 322 to 342 interleave the orthogonal symbols - 17 - received from the orthogonal symbol generators 320 to 340 according to the hopping pattern. The orthogonal symbol selector 350 selectively outputs the symbols received from the interleavers 322 to 342 according to the hopping pattern to output a PN sequence. With an orthogonal code ofthe same length given, the output ofthe biorthogonal symbol hopping pattern generator 358 is twice as long as that ofthe orthogonal symbol hopping pattern generator 360. The PN sequence selected by the orthogonal symbol selector 350 and the hopping pattern information are exclusive-ORed by a bit like MSB or LSB in the exclusive-OR gate 390. FIG. 3F is a schematic view of a PN sequence generator based on biorthogonal Gold code hopping according to a sixth embodiment ofthe present invention. Referring to FIG. 3F, the biorthogonal symbol hopping pattern generator 358 generates hopping pattern information of an orthogonal code. The interleaver controller 380 generates an interleaving control signal according to the hopping pattern information received from the biorthogonal symbol hopping pattern generator 358. The initial value register 366 stores an initial value, and the nr-sequence generator 367 reads the initial value from the initial value register 366 and generates an nr-sequence corresponding to the initial value, the initial value register 362 stores the hopping pattern information as an initial value, and the nr-sequence generator 363 generates an nr-sequence corresponding to the initial value received from the initial value register 362. Therefore, the nr-sequence generators 363 and 367 output different resequences. The exclusive-OR gate 364 exclusive-ORs the outputs ofthe nr- sequence generators 363 and 367 to produce a Gold sequence. The comparator 369 compares the status value ofthe nr-sequence generator 367 with a predetermined value and generates a switch controlling signal according to the - 18 - comparison result. The switch 368 is selectively switched between a zero value input and the output of the exclusive-OR gate 364. The switch selects the zero value input for one clock period responsive to the switch controlling signal received from the comparator 369 when the output ofthe nr-sequence generator 5 367 is equal to the predetermined value. Otherwise, if the values are different, the switch 368 selects the output ofthe exclusive-OR gate 364, that is, the Gold sequence. The switch 368 may be implemented as a multiplexer. The exclusive- OR gate 390 exclusive-ORs the orthogonal symbol received from the switch 368 and the biorthogonal code hopping pattern information. The interleaver 0 controller 380 generates a control signal for interleaving the symbols received from the switch 368 according to the hopping pattern information received from the biorthogonal symbol hopping pattern generator 358. The interleaver 322 interleaves the output ofthe exclusive-OR gate 390 under the control ofthe interleaver controller 380 to produce a PN sequence. 5 In operation, the biorthogonal symbol hopping pattern generator 358 determines an initial value for the nr-sequence (with a period of 2"- 1) generator 363. The determined initial value is stored in the register 362. Another nr- sequence (with a period of T- 1) generator 367 generates an nr-sequence with an initial value with no relation to the biorthogonal symbol hopping pattern 0 generator 358 and the initial value is stored in the register 366. The outputs of the two nr-sequence generators 363 and 367 are exclusive-ORed to produce a Gold sequence as output from the exclusive-OR gate 364. To generate a orthogonal Gold code from the Gold sequence, the comparator 369 compares the status value ofthe nr-sequence generator 367 with a predetermined value. If 5 they are equal, the nr-sequence generators 363 and 367 are stopped for one clock period, and the switch 368 inserts a zero value into the Gold sequence for - 19 - the clock period. If they are different, the Gold sequence is selected by the switch 368. With an orthogonal code ofthe same length given, the output ofthe biorthogonal symbol hopping pattern generator 358 is twice as long-as that of the orthogonal symbol hopping pattern generator 360. The PN sequence output from the switch 368 and the hopping pattern information are exclusive-ORed by a bit like MSB or LSB in the exclusive-OR gate 390. . Then, the interleaver 322 interleaves the output ofthe exclusive-OR gate 390 under the control ofthe interleaver controller 380. From FIGs. 4A and 4B, it is noted that while a receiver receives signals using the same PN generating orthogonal code OC3 and the same channel identifying orthogonal code at the same time from at least two base stations, different cyclic shift or interleaving for each base station according to the present invention prevents signal collision caused by use ofthe same code. A receiver can recover a signal received from a transmitter having a PN sequence generator ofthe present invention by cyclic shift and deinterleaving according to the same hopping pattern used in the transmitter, or extract the hopping pattern information from a received signal. In this case, the transmitter operates according to an initial hopping pattern for generating a PN sequence when data is initially transmitted, and the receiver also operates according to the initial hopping pattern. If the hopping pattern is changed, the transmitter notifies the receiver ofthe changed hopping pattern. The receiver includes a lookup table for storing the hopping patterns for PN sequences received from the transmitter, and detects a PN sequence according to hopping pattern information read from the lookup table when the hopping pattern is changed. - 20 - The PN sequence generator ofthe present invention as described above generates a PN sequence by interleaving or cyclically shifting the symbols of an orthogonal code according to a hopping pattern. Therefore, even though a receiver simultaneously receives signals spread by PN sequences generated from hopping ofthe same orthogonal or biorthogonal code in different transmitters, concurrent spreading ofthe data symbols can be prevented by varying the amount of interleaving or cyclic shift. While the present invention has been described in detail with reference to the specific embodiments, they are mere exemplary applications. Thus, it is to be clearly understood that many variations can be made by anyone skilled in the art within the scope and spirit ofthe present invention.

Claims: - 21 - WHAT IS CLAIMED IS: 1. A PN sequence generating device in a CDMA communication system, comprising: orthogonal symbol generating means for cyclically shifting a plurality of orthogonal symbol sequences; and an orthogonal symbol selector for selectively outputting one of said cyclically shifted orthogonal symbols according to a predetermined pattern. 2. The PN sequence generating device of claim 1, wherein the plurality of orthogonal symbol sequences are one of a mutually orthogonal symbol sequence and a periodic orthogonal symbol sequence. 3. The PN sequence generating device of claim 1 , wherein the orthogonal symbol generating means comprises: a plurality of orthogonal symbol generators for generating said orthogonal symbol sequences; and a plurality of delay devices for cyclically shifting the generated orthogonal symbol sequences. 4. The PN sequence generating device of claim 1, wherein the orthogonal symbol generating means comprises: a plurality of orthogonal symbol generators for generating mutually orthogonal symbol sequences; and a plurality of interleavers for row permuting the orthogonal code sequences. - 22 - 5. The PN sequence generating device of claim 1 , wherein cyclically shifting the orthogonal symbols is based on a predetermined pattern. 6. The PN sequence generating device of claim 5, wherein the predetermined pattern is an orthogonal symbol hopping pattern. 7. The PN sequence generating device of claim 4, wherein the predetermined pattern is a biorthogonal symbol hopping pattern. 8. A PN sequence generating device in a CDMA communication system, comprising: PN sequence generating means for generating a PN sequence based on orthogonal Gold code hopping; and an interleaver for permuting the PN sequence according to a predetermined pattern. 9. The PN sequence generating device of claim 8, wherein the PN sequence generating means comprises: a hopping pattern generator for generating hopping pattern information; a first register for storing the hopping pattern information as a first initial value; a first nr-sequence generator for generating a first nr-sequence according to said first initial value stored in said first register; a second register for storing a second initial value; a second nr-sequence generator for generating a second nr- sequence according to said second initial value stored in said second register; - 23 - an exclusive-OR gate for exclusive-ORing said first m-sequence with said second m-sequence; a comparator for comparing the second nr-sequence with a predetermined value and generating a switch controlling signal based on said comparison; and a switch for selecting one of said exclusive-OR output and a zero value according to the switch controlling signal. 10. The PN sequence generating device of claim 9, wherein the hopping pattern generator is an orthogonal symbol hopping pattern generator. 1 1. The PN sequence generating device of claim 9, wherein the hopping pattern generator is a biorthogonal symbol hopping pattern generator. 12. A method for generating a PN sequence in a CDMA communication system, comprising the steps of: (1) cyclically shifting a plurality of orthogonal code sequences; and (2) selectively outputting one of said plurality of cyclically shifted orthogonal code sequences according to a predetermined pattern. 13. The PN sequence generating method of claim 12, wherein the step of cyclically shifting further comprises the steps of: generating a plurality of orthogonal code sequences; and cyclically shifting said plurality of orthogonal code sequences. 14. The PN sequence generating method of claim 12, wherein the - 24 - step of cyclically shifting further comprises the steps of: generating a plurality of orthogonal code sequences; and permuting said plurality of orthogonal code sequences row by row. 15. The PN sequence generating method of claim 12, wherein the cyclic shift operation is based on a predetermined pattern. 16. The PN sequence generating method of claim 15, wherein the predetermined pattern is an orthogonal symbol hopping pattern. 17. The PN sequence generating method of claim 15, wherein the predetermined pattern is a biorthogonal symbol hopping pattern. 18. A method for generating a PN sequence in a CDMA communication system, comprising: (1) generating a PN sequence based on orthogonal Gold code hopping; and (2) permuting the PN sequence according to a predetermined pattern. 19. The PN sequence generating method of claim 18, wherein the generating step further comprises: generating hopping pattern information; storing the hopping pattern information as a first initial value; generating a first m-sequence according to the first initial value; storing a second initial value; - 25 - generating a second m-sequence according to the second initial value; exclusive-ORing the first and the second nr-sequences; comparing the second nr-sequence with a predetermined value and generating a switch controlling signal based on said comparison; and outputting one of said exclusive-ORed output and a zero value according to the switch controlling signal. 20. The PN sequence generating method of claim 19, wherein the hopping pattern is an orthogonal symbol hopping pattern. 21. The PN sequence generating method of claim 19, wherein the hopping pattern is a biorthogonal symbol hopping pattern.

Inventors: PARK SU WON, PARK, SU, WON
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1999
Main classification: H04B7
IPC codes: H04B1, H04B7, H04J11, H04J13