HK1041750B - Method and apparatus for reducing peak-to-average ratio in a cdma communication system - Google Patents

Description

Method and apparatus for reducing peak-to-average ratio in CDMA communication system

Technical Field

The present invention relates to communications. More particularly, the present invention relates to a novel and improved method and apparatus for reducing peak-to-average ratio in a code division multiple access communication system.

Background

Code Division Multiple Access (CDMA) modulation techniques are one of several communication techniques that facilitate the presence of a large number of system users today. Although, many other techniques are for example: time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), and amplitude modulation schemes such as: amplitude companding single-sideband techniques and the like are known. CDMA still has significant advantages over other technologies. The use of CDMA techniques in multipath COMMUNICATION SYSTEMs may be referred to in U.S. patent No. 4,901,307 entitled "spread spectrum MULTIPLE ACCESS COMMUNICATION SYSTEM for use in SATELLITE OR terrestrial repeaters" (spread spectrum MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR terrestrial repeaters). This patent is assigned to the assignee and is incorporated herein by reference for all purposes. The use of CDMA techniques IN a multi-path communication SYSTEM may be further referred to IN U.S. patent No. 5,103,459 entitled "SYSTEM and METHOD for generating SIGNAL WAVEFORMS IN a CDMA CELLULAR TELEPHONE SYSTEM" (SYSTEM AND METHOD for generating SIGNAL WAVEFORMS IN a CDMA CELLULAR TELEPHONE SYSTEM), which is assigned to the assignee and is hereby incorporated by reference. A CDMA system may be designed in accordance with the "TIA/EIA/IS-95 dual mode wideband spread spectrum cellular system standard compatible with a mobile station-base station," referred to herein below as the IS-95 standard.

A CDMA system is a set of spread spectrum communication systems. Spread spectrum communications are well known to the art and information can be obtained from the above-mentioned references. CDMA, due to its inherent wideband signal characteristics, provides a way to achieve frequency diversity by spreading the signal energy over a wideband. Thus, selective fading of frequency affects only a small portion of the bandwidth of the CDMA signal. Path diversity or spatial diversity is obtained by providing multiple signal paths through synchronized links of two or more base stations to a mobile user or remote site. Further, path diversity is obtained by allowing separate reception and processing of signals with different propagation delays during spreading in a multipath environment. Examples of path diversity are illustrated IN U.S. patent No. 5,101,501 entitled "METHOD and SYSTEM FOR PROVIDING SOFT HANDOFF IN COMMUNICATIONS IN a CDMA CELLULAR TELEPHONE SYSTEM" (METHOD AND SYSTEM FOR PROVIDING SOFT HANDOFF IN communication IN a CDMA CELLULAR TELEPHONE SYSTEM), and U.S. patent No. 5,109,390 entitled "using multiple receivers IN a CDMA CELLULAR TELEPHONE SYSTEM", both of which are assigned to the assignee and are incorporated herein by reference.

In a CDMA system, the forward link refers to the transmission from a base station to a remote station. In an exemplary system for CDMA using the IS-95 standard, data and voice transmissions for the forward link occur in orthogonal code channels. According to the IS-95 standard, each orthogonal code channel IS covered by a unique Walsh function with a period of 64 chips. This orthogonality minimizes interference between code channels and improves performance.

Several design features of CDMA systems provide the system with a high system capacity, which can be measured in terms of the number of users supported. First, the transmission frequency of the neighboring cell may be reused. Second, more directional antennas transmitting to some regions and some remote sites can be used to achieve greater capacity. In a CDMA system, the coverage area (cell) may be divided into several (e.g., 3) sectors, depending on the directional antenna used. Methods and apparatus for providing sectors in a CDMA communication SYSTEM may be found in U.S. patent No. 5,621,752 entitled "ADAPTIVE sector partitioning (ADAPTIVE sector partitioning IN A SPREAD spectrum management SYSTEM) in a spread spectrum communication SYSTEM," which is assigned to the assignee and incorporated herein by reference. Each sector and cell may be further divided into more directional spot beams. Alternatively, the spot beam may be arranged to select a sector or cell of a remote site or a group of remote sites. A local coverage area within a sector or cell may be a pico-zone. This pico-zone may be embedded in a sector or cell to improve capacity and provide additional services.

In this exemplary CDMA system, the forward link transmissions typically employ different short PN spreading sequences (or a common set of short PN spreading sequences with different offsets) in different sectors. When a remote site is in an overlapping sector coverage area and is demodulating one sector's signal, the signal from the other sector is spread and appears as wideband interference. However, the signals from other sectors or cells are not orthogonal to each other. Non-orthogonal interference from adjacent sectors or cells can degrade performance of the communication system.

In an IS-95 standard CDMA communication system, the pilot channel transmitted in the forward link IS intended to assist the remote station in coherently demodulating the received signal. Coherent demodulation results in further performance improvements. For each beam there is a pilot channel. According to the IS-95 standard, the pilot channel IS zero-covered by a Walsh function.

Many challenges arise when attempting to increase the capacity of CDMA. First, the Walsh function used to cover the code channel IS defined by the IS-95 standard and IS limited to 64. Second, a method that allows remote stations to distinguish between different beams, sectors, or picocells with minimal signal processing in a CDMA system is desirable. Third, such a method must comply with the IS-95 standard. It is to these challenges that this invention addresses.

Disclosure of Invention

The present invention is a novel and improved method and apparatus for reducing peak-to-average ratio in a system using a secondary pilot channel, as in the third generation wireless communication system described for the ITU in TIA/EIA TR45.5 "cdma 2000 ITU-R RTT candidatesub". The inventors have discovered that the use of a planned secondary pilot channel can result in a high peak-to-average ratio, which can have an undesirable impact on system capacity. A problem that arises when using a secondary pilot channel is that there is no data to modulate the pilot waveform. Because the data carried by each pilot channel is the same, the pilot waveforms are added in a structure, resulting in high energy peaks at portions of the waveform.

The first method proposed by the present invention to address the above problem is to change the phase of the auxiliary pilot channel to avoid adding the structural properties of the pilot channels. A second approach to the above problem of the present invention is to eliminate the structural addition of the auxiliary pilot channels. This invention also proposes a novel demodulator design for receiving signals with a modified auxiliary pilot signal.

A first aspect of the present invention discloses a base station, including: a pilot modulator for generating a common pilot signal; a plurality of auxiliary pilot modulators for generating a plurality of auxiliary pilot signals; wherein each of the pilot signals is composed of a plurality of pilot symbols; and symbol accumulation reduction means for varying at least one of said auxiliary pilot signals to reduce the peak-to-average ratio of said pilot signals.

Another aspect of the present invention discloses a mobile station comprising: means for receiving a pilot signal; means for varying a phase of an auxiliary pilot signal in the received pilot signals to form a phase-shifted pilot signal having a phase rotation; means for receiving a traffic signal; and means for demodulating the traffic signal based on the phase-shifted pilot signal.

Yet another aspect of the present invention discloses a mobile station comprising: means for receiving a pilot signal; means for inserting an estimate of a reduced symbol energy in an auxiliary pilot signal of the received pilot signal to provide an improved estimate of the pilot signal; means for receiving a traffic signal; and means for demodulating the traffic signal based on the improved estimate of the pilot signal.

In one aspect of the present invention, a method for transmitting a plurality of pilot signals in a base station simultaneously transmitting the pilot signals is disclosed, comprising the steps of: generating a plurality of pilot signals, wherein the generated plurality of pilot signals comprise a common pilot signal and a plurality of auxiliary pilot signals, and each of the plurality of pilot signals is composed of a plurality of pilot symbols; and altering at least one of the auxiliary pilot signals to reduce symbol accumulation in the plurality of pilot signals.

In one aspect of the present invention, a method of receiving a signal from a base station in a mobile station is disclosed, the method comprising the steps of: receiving a pilot signal; changing the phase of an auxiliary pilot signal in the received pilot signals to form a phase-shifted pilot signal with a phase rotation; receiving a traffic signal; and demodulating said traffic signal based on said phase-change pilot signal.

In still another aspect of the present invention, a method of receiving a signal from a base station in a mobile station is disclosed, the method comprising the steps of: receiving a pilot signal; inserting an estimate of reduced symbol energy in an auxiliary pilot signal of the received pilot signal to provide an improved estimate of the pilot signal; receiving a traffic signal; and demodulating said traffic signal based on the improved estimate of said pilot signal.

Drawings

The features, objects, and advantages of the present invention will become more apparent upon consideration of the following detailed description thereof, taken in conjunction with the accompanying drawings, which are generally consistent with the features of the present invention.

Fig. 1 is a diagram of a base station transmitter of the present invention.

Fig. 2 is a diagram of the common pilot channel modulator of the present invention.

Fig. 3 is a diagram of a traffic channel modulator of the present invention.

Fig. 4 is a first exemplary embodiment of an auxiliary pilot modulator of the present invention.

Fig. 5 is a second exemplary embodiment of an auxiliary pilot modulator of the present invention.

Fig. 6 is a diagram of a receiver that receives and coherently demodulates signals using the modified auxiliary pilot channel signal generated as described in fig. 4.

Fig. 7 is a diagram of a receiver that receives and coherently demodulates the modified auxiliary pilot channel generated as described in fig. 5.

Fig. 8 is a diagram of a third exemplary embodiment of an auxiliary pilot modulator using quasi-orthogonal codes to determine phase shifts according to the present invention.

Fig. 9 is a diagram representing a permutation matrix algorithm suitable for use in the method of the present invention.

FIG. 10 is a diagram representing a quasi orthogonal mask generation algorithm suitable for use in the present invention; and

fig. 11A-11E illustrate the correlation properties of quasi-orthogonal sequences and Walsh functions of equal or shorter length.

Detailed Description

I. Introduction to the word

In the present invention, there are two types of pilot channels that can be used to coherently demodulate the CDMA signal. The first type of pilot channel is the common pilot channel, which is used to help demodulate the traffic channel for any mobile station in the sector. In the exemplary embodiment, the common pilot channel is covered using an all-zero sequence of Walsh (0). The common pilot Walsh function is of equal length to the Walsh function covering the traffic channel.

The second type of pilot channel is the type of pilot channel transmitted by the base station sector (shown in fig. 1), which is a type of auxiliary pilot sequence. The auxiliary pilot sequence is a pilot sequence formed from a concatenation of a predetermined Walsh function and a Walsh function complement. The application of one auxiliary pilot is: antenna beamforming is applied to generate spot beams. Spot beams may be used to increase the coverage of a particular geographic spot or to increase the capacity of a highly congested area, commonly referred to as a hot spot. The secondary pilot may be shared by multiple mobile stations in a spot beam.

The code multiplexed auxiliary pilots may generate different Walsh codes for each auxiliary pilot. This approach reduces the number of orthogonal codes that can be acquired for the traffic channel. This limitation can be mitigated by spreading the Walsh code set size used for the secondary pilot. Because a pilot signal is not modulated with data, the length of the pilot Walsh function can be spread, thereby resulting in an increased number of available Walsh codes.

Each Walsh code W_i ^m(i is the index of the Walsh function, m is the length of the Walsh function or its order) can be used to generate N auxiliary Walsh codes, N must be the power of 2 (N2)ⁿAnd n is a non-negative integer). A more elongated Walsh function may be passed through the concatenation of W_i ^mObtained by N times. W of each cascade_i ^mDifferent polarities are possible. The order of polarity must be chosen to produce N additional orthogonal Walsh functions with an N x m order.

In the exemplary embodiment, N equals 4, followed by 4 slaves W_i ^mThe selected auxiliary Walsh codes with 4 x M steps are:

each of the N x m generated Walsh functions is associated with another W_i ^mThe Walsh function of (j ≠ i) is orthogonal to other traffic channels. All Walsh functions are available except W₀ ^mSince it will interfere with the common pilot if it is integrated over a short period of spread N x m Walsh length. Is used to generate an auxiliary pilot Walsh W_i ^mAnd cannot be used by other traffic channels. This limitation of spreading the Walsh function with N is due to the limitation that a smooth channel is required for spreading the period of the Walsh function with N x m. One method of generating secondary pilots and demodulating the traffic channels of the secondary pilots in such a situation is described in detail in U.S. patent application serial No. 08/925,521 entitled "method and apparatus for providing orthogonal spot beams, sectors, and picocells". This patent was filed on 1997, 9/8 and assigned to the assignee, and is incorporated herein by reference for all purposes。

A problem that arises in using the secondary pilot channel is that there is no data to modulate the pilot waveform. Because the data carried by each auxiliary pilot is the same, the pilot waveform is added in a structured manner and results in high energy peaks in the waveform portions. First, when all 4 auxiliary waveforms described in equation (1) are delivered at the same power, the resulting waveform is composed of one auxiliary waveform at peak 4 × W_j ^mFollowed by a string of 3 x m zeros (three Walsh function lengths). Furthermore, all Walsh functions start from where the chip value is 1. When more auxiliary pilots are based on other Walsh functions W_j ^mWhen added, the first chip of the nth Walsh function is constructively added to the 3 x m +1 bit position of the auxiliary pilot.

Figure 1 is a diagram of a base station sector of the present invention. The sector illustrated in fig. 1 provides a pilot channel over which a CDMA signal is transmitted and which may be used to coherently demodulate the signal. In the base station sector shown in fig. 1, both the common pilot channel and the secondary pilot generated in the previously discussed case are transmitted.

The common pilot and traffic channel modulator 109 generates a common pilot channel and a plurality of traffic channels that are coherently demodulated by means of the common pilot channel. The auxiliary pilot and traffic channel modulator 110 generates an auxiliary pilot channel that is used to coherently demodulate a set of traffic channels. The common pilot modulator and the auxiliary pilot modulator are capable of generating a common pilot signal and a set of auxiliary pilot signals. In the exemplary embodiment, each pilot and accompanying traffic signal is separately amplified and upconverted to provide maximum flexibility in beam steering and other applications. Those skilled in the art will appreciate that in another embodiment, the summation by adder 104 and adder 116, respectively, may be replaced by a single adder calculation.

In the common pilot and traffic channel modulator 109, pilot symbols are provided to a pilot modulator 100. In this exemplary embodiment, pilot modulationDevice 100 operates according to the Walsh function W₀ ^mThe pilot symbols are modulated. In this exemplary example, the pilot signal is an all-zero sequence. The traffic signal is provided to each traffic modulator 102. Each traffic modulator 102 follows a unique and dedicated modulation Walsh function (W)_T) Traffic data. The modulated data from each traffic modulator 102 and the pilot signal from pilot modulator 100 are summed in summer 104 and provide two sets of data streams for complex PN spreading element 106. The complex PN spreading element 106 provides a complex PN spread for the data according to the following equation:

I＝PN_II′+PN_QQ′ (2)

Q＝PN_II′-PN_QQ′， (3)

i' is the first data stream entering the complex PN spreading element 106. Q' is the second data stream entering the complex PN spreading element 106. Complex PN spreading is used to evenly distribute the transmit energy to the in-phase and out-of-phase portions of the transmitted QPSK signal. Complex PN spreading is well known in the art and may be referred TO by the document entitled "high data rate with REDUCED PEAK-TO-average ratio for transmit power in CDMA wireless COMMUNICATION SYSTEMs" (REDUCED PEAK-TO-AVERAGETRANSMIT POWER HIGH DATA RATE IN A CDMA WIRELESS COMMUNICATION SYSTEM), U.S. patent application 08/856,428, patented 5/14/1997, which is assigned TO the assignee and is incorporated herein by reference. This patent is equally applicable to other modulation formats such as BPSK and QAM. The complex PN spread data stream is then sent to transmitter 120, up-converted, filtered, amplified, and the resulting signal is sent to adder 122.

In the secondary pilot and traffic channel modulator 110A, the pilot symbols are provided to a secondary pilot modulator 112. Auxiliary pilot modulator 110A will modulate the pilot symbols according to the auxiliary pilot sequence generated according to equation (1) described above. In the exemplary embodiment, the pilot symbol is a sequence of all zeros. Traffic data is provided to each traffic modulator 114. Each traffic modulator 114 will modulate the traffic data according to a dedicated Walsh function. The modulated data provided by each traffic modulator and the pilot signal provided by auxiliary pilot modulator 112 are summed in summer 116 and provide two sets of data streams for complex PN spreading element 118. The complex PN spreading element 118 spreads the data according to equations (2) and (3) discussed above. The PN spread signal stream provided by complex PN despreader 118 is provided to transmitter (TMTR) 120. Transmitter 108 up-converts, filters, amplifies the signal and provides the resulting signal to adder 122. The auxiliary pilot and traffic channel modulators 110B-110K function as described for auxiliary pilot and traffic channel modulator 110A.

The signals from the auxiliary pilot and traffic channel modulators 110A-110K and the signals from the common pilot and traffic channel modulator 109 are summed in summer 122. The resulting summed signal is transmitted via antenna 124.

Fig. 2 is a diagram of an exemplary embodiment of pilot modulator 100 of the present invention. The pilot signal, which in this exemplary embodiment is an all-zero sequence, is provided to demultiplexer 150. Demultiplexer 150 maps the input pilot signal into a constellation of 4 points (1, 1), (1, -1), (-1, 1), (-1, -1)) and outputs the aligned sequence to output terminals 157 and 158. The signal streams at outputs 157 and 158 are provided to quadrature cover elements 154 and 156. Walsh generator 152 generates these orthogonal cover sequences. In this exemplary embodiment, the Walsh cover sequence is Walsh (0). The symbol stream from demultiplexer 150 is provided to orthogonal cover elements 154 and 156 and spread by the cover sequences generated by Walsh generator 152.

Fig. 3 is a diagram of exemplary embodiments of traffic channel modulators 102 and 114 of the present invention. The traffic signal is provided to a CRC (cyclic redundancy check) and tail bit generator 160. The tail bit generator is an element that generates a set of cyclic redundancy check bits and tail bits by a well-known method and adds the cyclic redundancy check bits and tail bits to traffic data. The bits generated from the CRC and tail bit generator 160 are provided to an encoder 162. Encoder 162 provides forward error correction processing for the traffic data and adds a CRC and tail bits. This invention contemplates a number of error correction coding methods such as convolutional coding and turbo coding. The complete code is provided to an interleaver 164, which rearranges the symbols according to a pre-customized format. The aligned symbols are provided to spreading element 166 where the spreading cell will scramble the data for security reasons with pseudo-random sequences that are known only to the receiving mobile station and the transmitting base station.

The scrambled sequences from spreading element 166 are provided to demultiplexer 168. Demultiplexer 168 maps the input pilot symbols into a constellation of 4 points (1, 1), (1, -1), (-1, 1), (-1, -1)) and outputs the mapped sequence to outputs 169 and 171. The signal streams at outputs 169 and 171 are provided to quadrature cladding elements 172 and 174. Walsh generator 170 generates these orthogonal cover sequences to be used for transmission to a particular mobile station user. The symbol stream from demultiplexer 168 is provided to orthogonal cover elements 172 and 174 and spread by the cover sequences generated by Walsh generator 170.

II. Peak-to-average ratio reduction by phase rotation

Fig. 4 is a diagram of a first exemplary embodiment of the auxiliary pilot modulator 112 of the present invention. The modulator is designed to address the above-described problem of adding bits in a structured manner in the secondary pilot channel. The pilot signal, which in this exemplary embodiment is a sequence of all zeros, is provided to demultiplexer 180. Demultiplexer 180 maps the input pilot symbols into a constellation consisting of 4 points (1, 1), (1, -1), (-1, 1), (-1, -1)) and then outputs the mapped sequence onto outputs 181 and 183. The symbol streams at outputs 181 and 183 are provided to quadrature covering elements 186 and 188. Auxiliary pilot Walsh generator 182 generates these orthogonal cover sequences in accordance with equation (2) above and provides the orthogonal spreading sequences to phase rotation element 184. The phase rotation element 184 is a symbol accumulation reduction means for varying at least one of the pilot signals to reduce the peak-to-average ratio of the pilot signal sum.

The phase rotation element 184 rotates the auxiliary pilot spreading sequence by a predetermined phase value. In this exemplary embodiment, the phase rotation element rotates the auxiliary pilot spreading sequence by 0 ° or 180 °. That is, the phase rotation element 184 will multiply the cover sequence by 1 or-1. The signal stream from demultiplexer 168 is provided to quadrature cover elements 172 and 174 and spread by the cover sequence from phase rotator element 184. The auxiliary pilot signal will not be structurally added by symbol transforming the entire auxiliary pilot Walsh spreading function by multiplying by 1 or-1. Note that the phase-rotated symbols must be communicated to the mobile station via the auxiliary pilot so that the mobile station can coherently demodulate the traffic data.

Fig. 6 is a block diagram of a receiver that receives and coherently demodulates traffic channel signals with an auxiliary pilot signal generated by the auxiliary pilot modulator depicted in fig. 4, which are received by an antenna 300 and provided to a receiver (RCVR) 302. Receiver 302 down-converts, filters, and amplifies the signal in accordance with a QPSK demodulation format and provides the result to correlator 326, which coherently demodulates the traffic channel using the modified auxiliary pilot channel.

At correlator 326A, the received signal is provided to complex conjugate multiplier 310. The complex conjugate multiplier 310 combines the received signal with a pseudo-random noise sequence PN_IAnd PN_QThe multiplication PN despreads the received signal. The despread signal is provided to pilot correlators 308A and 308B and multipliers 314A and 314B. Auxiliary pilot Walsh generator 304 and phase rotation element 306 cooperate to generate a modified auxiliary pilot sequence via auxiliary pilot Walsh generator 182 and phase rotation element 184 of fig. 4. Auxiliary pilot Walsh generator 304 generates orthogonal cover sequences according to equation (2) above and provides phase rotation element 306 withThese orthogonal spreading sequences. Phase rotation element 306 rotates the auxiliary pilot spreading sequence by a predetermined phase value. In this exemplary embodiment, the phase rotation element rotates the auxiliary pilot spreading sequence by 0 ° or 180 °. That is, the phase rotation element 306 multiplies the covering sequence by 1 or-1.

In the pilot correlators 308A and 308B, the received signals are multiplied by the phase-rotated pilot sequences and accumulated by the auxiliary pilot sequence length. The resulting despread pilot signal stream is provided to the dot product circuit 324. Walsh generator 312 generates a Walsh traffic sequence that is used to cover the mobile station user traffic data. The Walsh traffic sequences are provided to multipliers 314A and 314B, which multiply the received signal stream with the Walsh traffic sequences. The resulting sequence of multipliers 314A and 314B are provided to accumulators 316A and 316B. Accumulators 316A and 316B accumulate over a Walsh traffic sequence interval. The accumulated result sequence is provided to the dot product circuit 324.

Dot product circuit 324 performs a dot product calculation of the despread pilot signals from pilot correlators 308A and 308B with the despread traffic data sequence from accumulators 316A and 316B and provides two scalar data streams. The dot product circuit 324 functions to remove phase errors of signals propagating from the base station to the mobile station. The design and implementation of the DOT PRODUCT CIRCUIT 324 is well known in the art, and reference may also be made to U.S. Pat. No. 5,506,865 entitled "Pilot Carrier DOT PRODUCT Circuit" (Pilot Circuit). This patent is assigned to the assignee and is incorporated herein by reference for all purposes. In this exemplary embodiment, the dot product circuit 324 outputs a single multiplexed signal stream. In another alternative embodiment, this function may be split into two elements, one for performing the dot product calculation and the other for multiplexing the two result streams.

Correlators 326B-326M perform the same function as correlator 326A described above, except that they operate on different multipath components from the received signal. Parallel demodulation of signals on different propagation paths and combining of the demodulated signal streams are described in detail in us patent No. 5,101,5015,109,390. The demodulated signal estimates are provided to a combiner 328 and are combined to provide an improved estimate of the received signal data. The improved signal estimate from combiner 328 is provided to despreader 330. Despreader 330 despreads the signal with a long PN (pseudo noise) code sequence known only to the mobile station user and the transmitting base station or base station. The long PN spread signal is provided to a deinterleaver and decoder 332. The deinterleaver and decoder 332 rearranges the signal by a predetermined rearrangement format and decodes the rearranged symbols in a forward error correction format such as Viterbi decoding and turbo decoding.

In a different aspect of this embodiment, the rotation may be based on a random sequence, such as a pseudo-random noise sequence generated by combining the mobile station identification. Further, while a static phase rotation of an auxiliary pilot is discussed above, such phase rotation may be dynamic. In performing dynamic rotation, phase rotation element 184 will phase rotate the auxiliary pilots on a dynamic basis. In this exemplary embodiment, the auxiliary pilot rotation is on a frame-by-frame basis, and rotation of a group of frames or less may be implemented. In this embodiment, the shift is aware of the pattern used to generate the phase rotation, which is repeated in phase rotation element 306 in the same phase rotation pattern produced in phase rotation element 184.

III, gating high peak energy code element

Fig. 5 is a second exemplary embodiment of the auxiliary pilot modulator 112 of the present invention. The modulator is designed to address the above-described problem of adding bits in a structured manner in the secondary pilot channel. The pilot symbols, which in this exemplary embodiment are a sequence of all zeros, are provided to demultiplexer 190. Demultiplexer 190 maps the input pilot signal into a constellation consisting of 4 points (1, 1), (1, -1), (-1, 1), (-1, -1)) and then outputs the mapped sequence to output terminals 191 and 193. The symbol streams at outputs 191 and 193 are provided to orthogonal cover elements 194 and 196. Auxiliary pilot Walsh generator 192 generates these orthogonal cover sequences in accordance with equation (2) above and provides the orthogonal spreading sequences to Walsh cover element 194. The bit stream from demultiplexer 190 is spread by an auxiliary pilot spreading sequence generated by an auxiliary pilot Walsh generator 192.

The spread pilot signal from the overlay elements 194 and 196 is provided to the gate elements 200 and 202. When the architecturally added bits are to be provided to pass gate elements 200 and 202, control processor 198 sends a signal to pass gate elements 200 and 202 that causes the pass gate elements to reduce the power of the auxiliary pilot signal that is to be architecturally added. In this embodiment, the auxiliary pilot signal energy that would be added constructively would be reduced to zero.

Fig. 7 is a block diagram of a receiver that receives and coherently demodulates traffic channel signals with an auxiliary pilot signal generated by the auxiliary pilot modulator depicted in fig. 5. The signal is received by an antenna 350 and provided to a receiver (RCVR) 352. Receiver 352 down-converts, filters, and amplifies the signal and provides a received signal in accordance with a QPSK demodulation format and provides the result to correlator 354, which uses the modified auxiliary pilot channel to coherently demodulate the traffic channel.

In correlator 354A, the received signal is provided to complex conjugate multiplier 358. Complex conjugate multiplier 358 combines the received signal with pseudo-random noise sequence PN_IAnd PN_QMultiplied to perform PN despreading of the received signal. The PN despread signal is provided to symbol insertion elements 362A and 362B and multipliers 364A and 364B. Insertion elements 362A and 362B will insert the energy estimate reduced by gate elements 200 and 202 of fig. 5 into the received data stream. The modified received signal is provided to pilot correlators 370A and 370B.

Auxiliary pilot Walsh generator 356 generates orthogonal auxiliary pilot spreading sequences according to equation (2) above and provides orthogonal spreading sequences for pilot correlators 370A and 370B. In pilot correlators 370A and 370B, the modified received signal is multiplied by the auxiliary pilot sequence and accumulated over the auxiliary pilot sequence length. The resulting despread pilot signal stream is provided to a dot product circuit 378. Walsh generator 360 generates a Walsh traffic sequence that is used to cover traffic data to a mobile station user. Walsh traffic sequences are provided to multipliers 364A and 364B, which multiply the received signal stream with Walsh traffic sequences. The product sequence resulting from multipliers 364A and 364B is provided to accumulators 374A and 374B. Accumulators 374A and 374B accumulate the product sequences over the Walsh traffic sequence interval. The accumulated result sequence is provided to the dot product circuit 378.

Dot product circuit 378 dot-products the despread pilot signals from pilot correlators 370A and 370B with the despread traffic data sequence from accumulators 374A and 374B and provides two scalar data streams. The dot product circuit 378 functions to remove phase errors of the signal propagating from the base station to the mobile station. The design and implementation of the DOT-PRODUCT CIRCUIT 378 is well known in the art and may also be referred to in U.S. Pat. No. 5,506,865, entitled "Pilot Carrier DOT PRODUCT Circuit" (Pilot Circuit), which is assigned to the assignee and is incorporated herein by reference. In this exemplary embodiment, the dot-product circuit 378 outputs a single multiplexed signal stream. In another alternative embodiment, this function may be split into two elements, one for performing the dot product calculation and the other for multiplexing the two result streams.

Correlators 354B-354M perform the same function as correlator 354A described above, except that they operate on different multipath components from the received signal. Parallel demodulation of signals on different propagation paths and combining of the demodulated signal streams are described in detail in us patent No. 5,101,5015,109,390. The demodulated signal estimates are provided to a combiner 380 and combined to provide an improved estimate of the received signal data. The improved signal estimate from combiner 380 is provided to despreader 382. Despreader 382 despreads the signal using a long PN code sequence known only to the mobile station user and the transmitting base station or base station. The long PN despread signal is provided to a deinterleaver and decoder 384. The deinterleaver and decoder 384 rearranges the symbols by a predetermined rearrangement format and decodes the rearranged signals in a forward error correction format such as Viterbi decoding and turbo decoding.

IV, phase rotation based on quasi-orthogonal vector

One way in which BINARY QUASI-ORTHOGONAL codes may be generated is found in THE document 12.9.1998, commonly assigned as co-pending U.S. patent application serial No. 09/208,336, entitled METHOD AND apparatus for transmitting AND constructing BINARY QUASI-ORTHOGONAL VECTORS (METHOD AND apparatus for transmitting AND constructing BINARY QUASI-ORTHOGONAL VECTORS), which is incorporated herein by reference. This patent is assigned to the assignee and is incorporated herein by reference for all purposes. One way to generate a quaternary QUASI-ORTHOGONAL vector can be found in a document published in 12.05.2000, co-pending U.S. patent No. 6,157,611 entitled "METHOD and apparatus FOR constructing a binary QUASI-ORTHOGONAL vector" (METHOD and apparatus FOR constructing a binary QUASI-ORTHOGONAL vector "). This patent is assigned to the assignee and is incorporated herein by reference for all purposes. Further, THE use OF QUASI-ORTHOGONAL code VECTORS in variable length Walsh function systems can be found in THE document OF 5.29.2001, having a continuation OF THE United states patent No. 6,240,143B1 entitled "METHOD AND apparatus for reflecting AND transmitting QUASI-ORTHOGONAL VECTORS" (METHOD AND APPARATUS FOR REFLECTION AND TRANSMISSION OF QUASI ORTHOGONAL VECTORS)). This patent is assigned to the assignee and is incorporated herein by reference for all purposes. In particular, the above-mentioned patent application shows that the quasi-orthogonal vectors are the largest for the variable length Walsh functions of those symbol sub-blocks selected from the long quasi-orthogonal vectors. With respect to the method of generating quasi-orthogonal vectors, we will defer to the end of this chapter and introduce it again to avoid departing from the subject of the invention of using auxiliary pilot channels to reduce the number of structurally added symbols in communications. Various methods of generating quasi-orthogonal vectors are intended to minimize the structural accumulation of auxiliary pilot signals. Thus, the quasi-orthogonal function is a quasi-orthogonal function selected to optimize the shortened Walsh sequence.

In the above-mentioned patent application, it is stated that when a Q is generated_NAfter the quasi-orthogonal function of shape, it is the largest with a Walsh function of length N, where N is a shape of 2ⁿIs an integer of (1). In addition, the above-mentioned patent application also describes that Walsh functions having a length less than N are also maximized with sub-blocks of quasi-orthogonal sequences.

The characteristics of the correlation of quasi-orthogonal sequences and equal or shorter length Walsh functions are illustrated with reference to fig. 11A-11E. In FIG. 11A, a quasi-orthogonal sequence Q of 32 symbols₃₂Comprises q₁-q₃₂32 symbols. FIG. 11B illustrates a Walsh function (W) of 32 symbols₃₂)。Q₃₂And also with a Walsh function (W) having all 32 symbols₃₂) The set of (2) is largest.

FIG. 11C illustrates two Walsh functions (W) of 16 symbols₁₆). The 16-symbol Walsh function and Q₃₂Is also largest. Q₃₂Comprises q as a first sub-block₁-q₁₆The symbol of (2). Q₃₂Comprises q as a second sub-block₁₇-q₃₂The symbol of (2). Q₃₂With a Walsh function W of 16 symbols₁₆The set is also largest.

FIG. 11D illustrates 4 8-symbol Walsh functions (W)₈). The 8-symbol Walsh function and Q₃₂Is also largest. Q₃₂Comprises q as a first sub-block₁-q₈The symbol of (2). Q₃₂Comprises q as a second sub-block₉-q₁₆The symbol of (2). Q₃₂Comprises q as a third sub-block₁₇-q₂₄The symbol of (2). Q₃₂The fourth sub-block of (1) comprises q₂₅-q₃₂The symbol of (2). Q₃₂With a Walsh function W of 8 symbols₈The set of (c) is also largest.

FIG. 11E illustrates 8 4-symbol Walsh functions (W)₄). This is achieved by4-symbol Walsh function and Q₃₂Also the maximum of the eight sub-blocks. Q₃₂Comprises q as a first sub-block₁-q₄The symbol of (2). Q₃₂Comprises q as a second sub-block₅-q₈The symbol of (2). Q₃₂Comprises q as a third sub-block₉-q₁₂The symbol element of (1). Q₃₂The fourth sub-block of (1) comprises q₁₃-q₁₆The symbol of (2). Q₃₂Includes q as a fifth sub-block₁₇-q₂₀The symbol of (2). Q₃₂Comprises q₂₁-q₂₄The symbol of (2). Q₃₂Comprises q₂₅-q₂₈The signal element of (1). Q₃₂The eighth sub-block of (1) comprises q₂₉-q₃₂The signal element of (1). Q₃₂With a 4-symbol Walsh function W₄Is also maximally correlated.

In the exemplary embodiment, each set of 4 auxiliary pilots of length 4m consists of a Walsh function of length m (W)_m) By spreading the Walsh function (W)_m) And the Walsh function (W) listed below_m) Complement form generated:

W_m，1＝W_mW_mW_mW_m

if the auxiliary pilots defined by equation (4) above are placed in a matrix P, the form is as follows:

the reason for choosing equation (5) as the form of matrix P is that each column of this form matrix is a Walsh function.

If, a vector A is defined to contain each representative auxiliary pilot W_m，iVector a of phase rotation_iThe phase of (2) is rotated. Then the optimum phase rotation to determine the reduction of the peak-to-average ratio should be determined by the minimum of the sum of the elements of each column of the given matrix AP.

Since all columns of matrix P are Walsh functions, the minimum of the sum of the columns of matrix AP can be simply reduced to finding a vector a that is the largest of the Walsh functions represented by the columns of matrix P. As noted above, the vector that is maximally uncorrelated with the set of Walsh functions is a quasi-orthogonal vector or a sub-block of a larger quasi-orthogonal vector. Thus, if 8 secondary pilots are used, the best shift to reduce symbol accumulation is determined by a length-8 quasi-orthogonal vector symbol or 8 symbol sub-blocks of a larger quasi-orthogonal vector.

We now turn our attention to the method of generating quasi-orthogonal vectors with characteristics related to Walsh functions. A quasi-orthogonal vector is a vector other than an orthogonal vector. The quasi-orthogonal vectors are derived from all binary 2 sⁿThe residual code vectors in the vector space are selected to minimize interference with the orthogonal vectors. In particular, the quasi-orthogonal vectors are selected to provide interference levels that are within acceptable interference limits, even though non-zero interference.

To select quasi-orthogonal vectors, a computer search algorithm may be applied at all 2ⁿBinary (+1/-1 alphabet) mask vector space. Masks may be used for the orthogonal vectors to generate a new set of quasi-orthogonal vectors. Applying all M masks to one Walsh code vector w_n′Set, the number of generated quasi-orthogonal functions is: (M +1) n. Applying a mask m to a code vector W ∈ W_nComprising multiplying the mask m and the orthogonal code vector w by the component sum to generate a new code vector:

w_m＝w·m (7)

the interference results from applying the new code vectors can be determined and the code vector providing the least correlation can be selected to provide a set of quasi-orthogonal vectors. We can find many masking functions in order to find many sets of quasi-orthogonal vectors from a single set of orthogonal vectors. In order to separate message signals mixed with quasi-orthogonal vectors found by computer search from each other, the quasi-orthogonal vectors must be orthogonal to each other. At least one code vector in the orthogonal set is non-zero correlated with one code vector in the quasi-orthogonal set.

If v represents a quasi-orthogonal vector, it can be expressed as:

the purpose of selecting the quasi-orthogonal vector v is to select the next vector, so that

As small as possible.

Because the correlation of vectors is an effective measure of the degree of separation between vectors. Two code vectorsx， yThe normalized correlation of (d) can be defined as follows:

the correlation between two orthogonal vectors is zero. The absolute value of the correlation is low because the degree of separation between the message signal mixed with the orthogonal vector and the message signal mixed with the quasi-orthogonal vector is good.

The mean square correlation of an orthogonal vector and a corresponding quasi-orthogonal vector (n is a power of 2) is 1/n. The lower bound of the absolute value of the correlation can be defined asThis quantity is the Holtzman lower bound. When n is an even power of 2, it is known that the mask reaches the lower bound. However, when n is an odd power of 2, this lower bound medium sign is not satisfied, and the minimum correlation in the latter case isTherefore, the best quasi-orthogonal vector interference amount found in the odd power of 2 by the computer search technique is the theoretical limitAnd (4) doubling.

In the signaling of the invention, masks m are constructed and applied to orthogonal code vectors to provide quasi-orthogonal code vectors, the masks being quadrature phase or Quadrature Phase Shift Keying (QPSK) masks. Mask m has a 4-element alphabet, { + -1, + -j }, instead of two elements, whereIs the virtual root of 1. It will be further appreciated that the signaling method of the present invention may have 2 masks when transmitting a message signal. One of the two masks may be used inside the in-phase (I) channel and the other outside the out-of-phase (Q) channel.

To implement the transmission method used in this invention, this new mask m may be generated using a Line Feedback Shift Register (LFSR). A2^kMeta LFSR sequence s [ t ]]Is a symbol consisting of {0, 1, …,2 }^k-1} when in the binary case k is defined as 1 and in the quaternary case k is 2. This sequence satisfies a linear recurrence relation:

r.gtoreq.1 is the order of recursion. Coefficient c_iBelong to the set 0,1, …,2^k-1} and c_rNot equal to 0. This sequence s [ t ]]There is a characteristic polynomial:

when k is 1, the sequence s [ t ]]Is less than or equal to 2^r-1. If, the sequence s [ t ]]Has reached a maximum value of 2^r-1，s[t]Will be defined as a primitive polynomial and the sequence s [ t ]]Is an m-sequence. This form of sequence is described in the "shift register sequence" written by s.w. golomb (HoldenDay, San Francisco, CA, 1967).

A C' code consists of one period of the m-sequence and one period of each of its cyclic shifts. The size of the code C' is 2^r-1. The code C 'can be extended by adding a zero bit to each codeword in C'. Zero bits are added at the same bit positions of each codeword. The inclusion of this form of all-zero vector from the code matrix C constitutes the code C'.

The length of the code matrix C is 2^rSize of 2^r. In one embodiment, code C may be permuted in a column-wise and row-wise manner to generate a size of 2^rWalsh code ofCode W_b，2r. In this way, it is sufficient to obtain the set of row vectors and W that make the matrix product CP_b，2rThe row vectors are grouped into the same permutation matrix P.

Referring to fig. 9, we show a permutation matrix algorithm 510 that represents a suitable method for use with the present invention. In the permutation matrix algorithm 510, the matrix W_b，2rAs shown in block 512. The submatrix W comprises r rows with the sequence 1, 2, 4, …,2^r-1. Note W_b，2rIs based on a sequence number starting from zero and ranging from 0 to 2^r-1. The matrix W has r rows and 2^rAnd (4) columns. The elements of each column of the matrix are different from the other columns.

One sub-matrix M of the code matrix C is shown as block 514 of the permutation matrix algorithm 510. The submatrix M has r rows 2^rAnd (4) columns. To generate the submatrix M, one has r rows 2^rThe middle submatrix M' of 1 column is generated. The submatrix M' is formed by adding a column of all-zero elements to the submatrix M. The first row of the sub-matrix M' may be any of the M-sequence cyclic shifts used in the constructed code C. The next r-1 rows after the first row of the submatrix M' are generated by successively shifting one time unit at a time from the first row. Each column of the sub-matrix M is different.

A permutation matrix P of MP ═ W is then generated as depicted in block 516 of permutation matrix algorithm 510. The permutation matrix P is the output required by the algorithm 510. Since the sub-matrices M and W have the same set of different columns. The method of deciding the generation of the matrix P becomes simple. In an alternative embodiment of the present invention, the permutation matrix P may be determined by a matrix computation technique. It will be understood by those skilled in the art that the rows and W of the matrix CP_b，2rThe same applies.

When k is 2, the sequence is a quaternary alphabet. A sequence called cluster a can be generated. The A cluster sequence is referred to in the documents published in the IEEE information theory annual society, S.Boztas, P.V.Kumar, R, Hammons, "four-Phase Sequences with Near-optimal correlation Properties" (4-Phase Sequences with Near-optimal correlation Properties), IT-383 (May 1992), pp 1101-. To obtain the A cluster sequence, let c (y) be a binary primitive polynomial of degree r. The polynomial g (x) coefficient set {0, 1, 2, 3} may be derived from the polynomial c (x) lifting:

g(x²)＝(-1)rc(x)c(-x)(mod 4) (13)

this boost from the binary polynomial c (x) to the quaternary polynomial g (x) is a special Hensel polynomial boost. For example, refer to "finish Rings with Identity," MarcelDekker, Inc., New York, 1974, written by B, R, MacDonald. The LFSR characteristic polynomial sequence is defined as the a cluster sequence. The sequence has a period of 2^r-1。

Referring to fig. 10, a diagram of a quasi orthogonal mask generation algorithm 650 is shown. Quasi-orthogonal mask generation algorithm 650 may be used to construct a 4-phase mask to generate a length of 2^rA quasi-orthogonal vector of (a). In mask generation algorithm 650, a binary, r-th order primitive polynomial c (x) is shown in block 652. By using the primitive polynomial c (x) as its characteristic polynomial, the period of an m-sequence is constructed as shown in block 656.

(2^r-1)×(2^r-1) matrix M' of dimension when n is 2^rThe time structure is shown as block 658. Each row of matrix M' contains an M-sequence and all its cyclic shifts as shown in block 656. The matrix M' is then expanded to form the matrix M as shown in block 662. The matrix M 'is expanded by adding a row of all zero rows and a column of all zero columns to the matrix M'. The dimension of matrix M becomes (2)^r)×(2^r). For simplicity, the first column of matrix M may be made to be all zero columns. As shown in block 666, a permutation P may be found to swap the columns of matrix M to make its row vector sum W_b，2rThe contained rows are identical. This permutation matrix method described above or other methods known to those skilled in the art may be used to implement the operations of block 666.

Next, Hensel lifting is applied to the primitive polynomial c (x) shown in block 652 of the mask generation algorithm 650 to obtain the polynomial g (x) described above. The Hensel lift operation is shown in block diagram. One period of the cluster a sequence with the polynomial g (x) as its characteristic polynomial is shown in block 678. One of the sequences of one of the clusters a is selected. The selected sequence may be a sequence having at least one symbol of 1 or 3 in any one of the a cluster sequences.

One length is (2)^rThe vector N' of-1) is constructed. Vector N' includes one period of the a cluster sequence selected as block 678. (2^r-1)×(2^r-1) dimensional matrix N₁' configured as shown in block 680. Matrix N₁' Each row contains the A cluster sequence period of block 678 along with all its cyclic shifts. Subsequently, the matrix N₁' expand as shown at block 682. Matrix N₁' is extended by using a matrix N₁' add an all zero column. By selecting the matrix N₁' extended row, length 2 can be obtained^rVector N of (a).

As shown in block 670, the vector N is column transformed with the permutation P found in block 666. After applying the appropriate symbol mapping on the permuted vectors as shown in block 684, the permuted codewords can be used in this invention as a masking function to generate quasi-orthogonal vectors. The quasi-orthogonal vectors generated by this method can be used for the case of mapping the symbols to (+1, -1, + j, -j). In this way, 127 masks can be generated in a Walsh code of length 128. The masks generated by the two quasi orthogonal masking algorithms 650 are shown in table I.

[1j1j1j1j1j1j1j1j1j1j1j1j-1-j-1-j-1-j-1-j1j1j-1-j-1-j1j1j-1-j-1-j1j1j-1-j-1-j-1-j-1-j1j1j1j-1-j1j-1-j1j-1-j1j-1-j1j-1-j1j-1-j-1-j1j-1-j1j1j-1-j-1-j1j1j-1-j-1-j1j1j-1-j-1-j1j-1-j1j1j-1-j]
	[1j1j1j1j-1-j-1-j1j1j1j-1-j1j-1-j1j-1-j-1-j1j1-j1-j-1j-1j-1j-1j-1j-1j1-j-1j-1j1-j1-j-1j1-j-1j-j1j-1-j1j-1j-1-j1-j1j-1-j1-j1-j1-j1-j1-j1j-1j-1j1-j-1-j-1j1-j-1j1-j-1j1j1j1-j-1-j-1j1j1j1j1]

TABLE I

The mask function obtained above is then further processed (permuted) to obtain the best correlation with the shorter length fat thread Walsh codes or orthogonal variable length functions and to maintain the best correlation with the equal length Walsh codes. ORTHOGONAL VARIABLE length sequences may be referred to IN the document having U.S. patent No. 5,751,761 entitled "METHOD and apparatus FOR generating ORTHOGONAL spreading sequences IN a VARIABLE data rate system" (SYSTEM AND METHOD FOR ORTHOGONAL SPREAD SPECTRUM sequence IN VARIABLE DATA RATE SYSTEM). And related information can also be found in "cdma 2000 conference subscription to the ITU" of TIA.

To give an example of the set of permutations discussed above to obtain the mask function without losing the best correlation with Walsh codes of fixed length (and equal length to the mask function), we note that the Walsh code is a sub-code of a first order Reed-Muller code, and any permutation within an isomorphic group of any one and equal length first order Reed-Muller codes will be used on those mask functions that leave the maximum absolute value of the correlation of equal length Walsh codes unchanged. These permutations will be applied systematically to obtain new mask functions that are optimal for fat thread usage.

We specify n (n is an integer power of 2) as the length of the mask function. For the purposes of the present discussion, there is a length of 2^mBlock b ═ b of packet of L chips₁₊₁，b₁₊₂，…，b_1+L]. Where L (L.gtoreq.4) is an integer power of 2. And each sub-block b_1+i(1. ltoreq. i. ltoreq.L) has the same length of 2^mOne chip. m (m.gtoreq.0) is an integer. Block

Is seen as a reflection of the block b with parameter m.

Is provided withv＝[v₁，…，v_n]Is a masking function. Let m, 0 ≤ m ≤ log₂And n is an integer. ThenvIt can be used with a length of 2^mThe sub-blocks of (a):

let r (4. ltoreq. r. ltoreq. n) be the integer power of 2, vector

Viewed as having parameters (m, r)vTotal reflection vector of (1).

The steps discussed below can be used to construct a mask function when a given QOF (quasi-orthogonal function) is used for the best fat thread:

1) constructing a 4-phase mask function from the discussion abovev ⁽¹⁾Starting from this function, the Walsh code of length n and this function have the best correlation properties.

2) Inspection length of 2^kIs/are as followsv ⁽¹⁾K has an initial value of 1, and has the best correlation with a Walsh code of length 2.

a) If it is notv ⁽¹⁾And a Walsh code of length 2. Is provided withv ^(k+1)＝ v ⁽¹⁾K +1, go to (3.).

b) If not, an attempt is made to selectv ^(TR)(0, r), r being an integer power of 2, 4 ≦ r ≦ n until when r equals a certain value r '(r ≦ r'),v ^(TR)(0, r') and the length 2 Walsh code have the best correlation. Then, putv ^(k+1)＝ v ^(TR)(0, r'), k ═ k +1, go to (3).

3) Inspection length of 2^kIs/are as followsv ^(k)Whether the sub-block sum of length 2^kThe Walsh codes of (a) have the best correlation.

a) If it is notv ^(k)Is a sum of length 2^kThe Walsh codes of (a) have the best correlation. Device for placingv ^(k+1)＝v ^(k)And k is k + 1. If k is log₂n, go to (4.). Otherwise, the iteration proceeds to another (3.) loop.

b) If not, an attempt is made to selectv ^(TR)(2^k+1R) for each possible value of r, 2^kR ≦ n until when r equals a certain value r ≦ r ",v ^(TR)(2^k-1r ") and a length of 2^kUntil the Walsh code of (a) has the best correlation. Device for placingv ^(k+1)＝ v ^(TR)(2^k-1R "), k ═ k + 1. If k is log₂n, go to (4.). Otherwise, the iteration proceeds to another (3.) loop.

4) Mask v^(log2n)Is a mask function of length n necessary for the optimization of fat threads.

Note that up to log may always be needed in order to obtain the necessary mask function that may need to be optimized for fat threads₂And (3) repeating the step (3) n-1 times.

Through the above steps, it is possible to find QOFs optimized for fat threads. We will illustrate the above two mask functions of length 128. The following are two resulting fat thread optimized mask functions:

[1j1-j1j-1j1j1-j-1-j1-j1j1-j1j-1j-1-j-1j1j-1j1j1-j-1-j1-j1j1-j1j-1j1j1-j-1-j1-j

-1-j-1j-1-j1-j1j-1j1j1-j1j-1j-1-j-1j1j-1j1j1-j-1-j1-j1j1-j1j-1j-1-j-1j1j-1j1j1

-j1j-1j-1-j-1j-1-j1-j-1-j-1j].

the above mask is rotated by 45 degrees to obtain a constellation of one point { ± 1 ± j }. The I-and Q-channels of the QOF mask corresponding to the above are shown below (in hexadecimal symbols):

[1jj-1-j11j-1-j-j1-j11j-j1-1-j1j-j1-j1-1-j-1-jj-1j11-j-1jj1-j-1-1j-1jj11-jj1-j

-11-j1-jj1j1-1j-j11j1jj-1j-1-1-j1jj-11j-j1-j1-1-j1j-j1j-11j1-j-j-1-j-1-1j-1jj1

-j-1-1jj1-1j-1j-j-1j1-1j1-jj1].

and rotating the mask by 45 degrees to obtain a constellation diagram of the IS-95C point { + -1 + -j }. The I-and Q-channels of the QOF mask corresponding to the above are shown below (in hexadecimal symbols):

QOF_I＝[7181242b8e7e242b17e7424d17e7bdb2]，

QOF_Q＝[18e8b2bd18e84d4281712b247e8e2b24].

the following two embodiments use QOF masks of length 256, which are masks optimized for fat threads of length 256 Walsh codes, using the method according to the present disclosure.

[1jj-11j-j11jj-1-1-jj-11j-j11jj-11j-j1-1-j-j11-jj11-j-j-11-jj1-1jj11-j-j-11-jj1

1-j-j-1-1j-j-11jj-11j-j11jj-1-1-jj-11j-j11jj-11j-j1-1-j-j1-1j-j-1-1jj1-1j-j-11

-j-j-1-1jj1-1j-j-1-1jj11-jj11jj-11j-j11jj-1-1-jj-11j-j11jj-11j-j1-1-j-j11-jj11

-j-j-11-jj1-1jj11-j-j-11-jj11-j-j-1-1j-j-1-1-j-j1-1-jj-1-1-j-j11j-j1-1-jj-1-1-j

-j1-1-jj-11jj-11-jj11-j-j-11-jj1-1jj11-j-j-11-jj11-j-j-1-1j-j-1].

The mask IS rotated by 45 degrees, so that a constellation diagram of IS-95C points { ± 1 ± j } IS obtained. The I-and Q-channels of the QOF mask corresponding to the above are shown below (in hexadecimal symbols):

[1j-j11jj-11-jj11-j-j-11j-j11jj-1-1j-j-1-1jj1-1jj11-jj11jj-1-1-jj-11-j-j-1-1j-j

-11jj-1-1-jj-1-1-jj-11jj-11-jj1-1jj11j-j1-1-j-j11-jj1-1jj11-j-j-11-jj11jj-11j-j

11-j-j-11-jj1-1-j-j1-1-jj-11-jj1-1jj11j-j1-1-j-j1-1j-j-11-j-j-11j-j1-1-j-j11jj

-11j-j1-1jj1-1j-j-11jj-11j-j11-j-j-j-11-jj11-jjj11-j-j-1-1-jj-1-1-j-j11-jj11-j-j-1

1j-j11jj-11jj-1-1-jj-11-j-j-1-1j-j-1-1-j-j11j-j11-j-j-1-1j-j-1].

and rotating the mask by 45 degrees to obtain a constellation diagram of points { ± 1 ± j }. The I-and Q-channels of the QOF mask as opposed to the above are shown below (in hexadecimal symbols):

QOF_I＝[472147dee27b1d7bb72e482e1274128b2e48d14874ed741221b821477b1d841d]，

QOF_Q＝[214721b8841d7b1dd1482e48741274ed482eb72e128b127447de47211d7be27b].

as described above, a set of quasi-orthogonal vectors can be generated that are maximally uncorrelated with the Walsh functions used to generate the secondary pilot channels. The method discussed above may generate complex quasi-orthogonal functions. In this invention, only the real part of the complex orthogonal function can be used to determine the phase of the auxiliary pilot. Because of their correlation properties, the quasi-orthogonal functions can be used to effectively reduce the peak-to-average ratio. The third embodiment is actually an optimized version of the first embodiment, the phase rotation is chosen according to a quasi-orthogonal function, and the phase rotation is simply a rotation of the auxiliary pilot channel by 180 degrees or 0 degrees.

Fig. 8 is a third exemplary embodiment of auxiliary pilot modulator 112. Is designed to address the above problem of adding bits to the secondary pilot channel structure. The pilot signal, in the exemplary embodiment, is a set of all-zero sequences provided to demultiplexer 480. The demultiplexer 480 arranges the input pilot signal in a constellation consisting of 4 points (1, 1), (1, -1), (-1, 1), (-1, -1)) and then outputs the mapped sequence to the output terminals 481 and 483. The symbol streams at outputs 481 and 483 are provided to quadrature covering elements 486A and 486B. Walsh auxiliary pilot generator 482 generates the orthogonal cover sequences in accordance with equation (2) above and provides the orthogonal spreading sequences to phase rotator element 484. The phase rotation element 484 is also a symbol accumulation reduction means for changing at least one of the pilot signals to reduce the peak-to-average ratio of the pilot signal sum.

Phase rotation element 484 multiplies the auxiliary pilot spreading sequence by 1 or-1 depending on the previously determined quasi-orthogonal spreading sequence. A quasi-orthogonal spreading function generator (QOF GEN)488 generates a quasi-orthogonal spreading function as described above. In the exemplary embodiment, a quasi-orthogonal spreading function generator (QOF GEN)488 generates a quasi-orthogonal function of equal length or number of symbols to the auxiliary pilot sequence. Then, if the length of the auxiliary pilot sequence is 256 symbols, a quasi-orthogonal spreading function generator (QOF GEN)488 generates a quasi-orthogonal function having 256 symbols.

A quasi-orthogonal spreading function generator (QOF GEN)488 provides the quasi-orthogonal functions to demultiplexer 490. The demultiplexer extracts one bit (having a value of +1 or-1) from the sequence and provides it to the phase rotator element 484. Phase rotation element 484 changes the phase of the auxiliary pilot sequence based on the quasi-orthogonal function symbol resulting from multiplying the auxiliary pilot sequence by the symbol from demultiplexer 490. Demultiplexer 490 provides each auxiliary pilot modulator with a symbol that is different from the quasi-orthogonal function from quasi-orthogonal spreading function generator (QOF GEN) 488.

A method for demodulation using the auxiliary pilot channel phase rotation according to a quasi-orthogonal function can be found in the first embodiment of the present invention.

V, auxiliary pilot signal derived from quasi-orthogonal function

In the foregoing description, the auxiliary pilot signal is constructed from a Walsh function. The invention can also be applied in other cases where the Walsh functions are constructed from quasi-orthogonal functions or from a concatenation of quasi-orthogonal functions and their complements. The above-described embodiments are all directly applicable to avoid the accumulation of secondary pilot symbols resulting from quasi-orthogonal functions.

The method discussed above provides us with a method of generating a complete set of quasi-orthogonal functions. When generating auxiliary pilots from quasi-orthogonal functions, the optimal phase shifting method to minimize symbol accumulation can be derived simply using one of the same or different quasi-orthogonal functions described above, as described above.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Many modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein may be applied to other embodiments without the use of inventive faculty. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (18)

1. A base station, comprising:

a pilot modulator for generating a common pilot signal; a plurality of auxiliary pilot modulators for generating a plurality of auxiliary pilot signals; wherein each of the pilot signals is composed of a plurality of pilot symbols; and

symbol accumulation reduction means for varying at least one of said auxiliary pilot signals to reduce the peak-to-average ratio of said pilot signals.

2. The base station of claim 1 wherein said symbol accumulation reducing means comprises a phase rotation means for varying the amount of phase rotation of at least one of said auxiliary pilot signals.

3. The base station of claim 2 wherein said phase rotation means changes the phase of at least one of said auxiliary pilot signals by multiplying by-1.

4. The base station of claim 1 wherein said auxiliary pilot signal is generated from a concatenation of a Walsh function and a complement of said Walsh function.

5. The base station of claim 2 wherein the phase rotation of each auxiliary pilot signal is determined according to a quasi-orthogonal function.

6. The base station of claim 5, wherein the quasi-orthogonal function is a quadrature phase shift keying quasi-orthogonal function.

7. The base station of claim 5 wherein said quasi-orthogonal function is a quasi-orthogonal function that is optimally selected for shortened Walsh sequences.

8. A mobile station, comprising:

means for receiving a pilot signal;

means for varying a phase of an auxiliary pilot signal in the received pilot signals to form a phase-shifted pilot signal having a phase rotation;

means for receiving a traffic signal; and

means for demodulating the traffic signal based on the phase-change pilot signal.

9. A mobile station, comprising:

means for receiving a pilot signal;

means for inserting an estimate of a reduced symbol energy in an auxiliary pilot signal of the received pilot signal to provide an improved estimate of the pilot signal;

means for receiving a traffic signal; and

means for demodulating the traffic signal based on the improved estimate of the pilot signal.

10. A method of transmitting a plurality of pilot signals in a base station that simultaneously transmits the pilot signals, comprising the steps of:

generating a plurality of pilot signals, wherein the generated plurality of pilot signals comprise a common pilot signal and a plurality of auxiliary pilot signals, and each of the plurality of pilot signals is composed of a plurality of pilot symbols; and

altering at least one of the auxiliary pilot signals to reduce symbol accumulation in the plurality of pilot signals.

11. The method of claim 10, wherein the step of varying at least one of the auxiliary pilot signals to reduce symbol accumulation comprises varying a phase of at least one of the auxiliary pilot signals to form a phase-varied pilot signal having a phase rotation.

12. The method of claim 11 wherein said step of changing the phase of at least one of said auxiliary pilot signals comprises changing the phase of at least one of said auxiliary pilot signals by multiplying by-1.

13. The method of claim 10, wherein the auxiliary pilot signal is generated from a concatenation of a Walsh function and a complement of the Walsh function.

14. The method of claim 11, wherein the changing is performed according to a quasi-orthogonal function.

15. The method of claim 14, wherein the quasi-orthogonal function is a four phase shift keyed quasi-orthogonal function.

16. The method of claim 14 wherein said quasi-orthogonal function is a quasi-orthogonal function selected for optimization of shortened Walsh sequences.

17. A method for receiving a signal from a base station in a mobile station, the method comprising the steps of:

receiving a pilot signal;

changing the phase of an auxiliary pilot signal in the received pilot signals to form a phase-shifted pilot signal with a phase rotation;

receiving a traffic signal; and is

Demodulating said traffic signal based on said phase-shifted pilot signal.

18. A method of receiving a signal from a base station in a mobile station, the method comprising the steps of:

receiving a pilot signal;

inserting an estimate of reduced symbol energy in an auxiliary pilot signal of the received pilot signal to provide an improved estimate of the pilot signal;

receiving a traffic signal; and is

Demodulating said traffic signal based on the improved estimate of said pilot signal.