JP2013236404A - Communication system synchronization method and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system synchronization method and a system.SOLUTION: The present invention relates to an uplink synchronization method between a first transceiver and a second transceiver in a multiuser cellular communication system. The method includes the steps of: transmitting a first signature sequence selected from a first signature sequence set from the second transceiver to the first transceiver; and in order to synchronize transmission between the second transceiver and the first transceiver, correlating in the first transceiver a received signal with at least one signature sequence among a second signature sequence set.

Description

  The present invention relates to the field of wireless communication systems, and in particular, to a method for uplink synchronization between a base station and a mobile terminal device in a multi-user cellular communication system.

  In most of today's communication systems, there are specific requirements regarding the synchronization of base stations and mobile terminals to ensure correct data transmission. Examples of such systems are UTRA (Universal Terrestrial Radio Connection) and Evolved UTRA.

  In Evolved UTRA, SC-FDMA (Single Carrier Frequency Division Multiple Access) can be used as a multiple access scheme for uplink communications. The SC-FDMA transmission scheme is so-called DFT spread OFDM (discrete Fourier transform spread orthogonal frequency domain multiplexing), which can be seen as OFDM with precoding. OFDM resulting in a multi-carrier signal has a high PAPR (peak to average ratio), whereas DFT precoding gives a single carrier signal with a lower PAPR. Low PAPR helps to extend the effective range and reduce battery drain on the mobile.

  In DFT spread OFDM, equalization in the frequency domain is achieved using a cyclic prefix. However, the requirement for successful DFT spread OFDM and equalization in OFDM is that the signal transmitted from all the mobile terminal devices in the cell is the cyclic prefix of the delay spread of the signal plus the spread of the arrival time. It is to be synchronized so that it is less than the duration. Accordingly, in order for each transmitting mobile terminal device to transmit data, it is first required to be synchronized to within a fraction of the cyclic prefix duration.

  In Evolved UTRA, synchronization is performed in both uplink and downlink. In one step of synchronization, downlink synchronization, the mobile terminal is synchronized (ie, locked) to the base station carrier frequency and frame timing. However, this synchronization ensures that the base station can properly receive the signal from the mobile terminal device because the mobile terminal device may be located at various distances relative to the base station. Not enough. Therefore, in general, the distance between the base station and the mobile terminal device is not known, and therefore the round trip time is not known, so further synchronization and uplink synchronization are required.

  In Evolved UTRA, RACH (Random Access Channel) supports uplink synchronization of mobile terminals. RACH in Evolved UTRA is contention based, that is, any mobile terminal in the cell can transmit on the resources allocated to RACH. Thus, a set of signature sequences can reduce the risk that several mobile terminals can attempt to transmit synchronization signals simultaneously and the base station fails to distinguish signals from different mobile terminals. Provided, each mobile terminal device randomly selects one signature sequence.

  In UTRA and Evolved UTRA, the binary pseudo-random sequence generated by the shift register is modulated by a 16-bit Hadamard sequence to generate these signature sequences. In many cases, these signature sequences provide good correlation properties, but with enhanced detection capabilities to detect specific signatures in the presence of other simultaneous signatures, especially at low SIR values. There is still a need.

B.M. Popovic, "New Complex Space-Time Block Codes for Efficient Transmit Diversity", IEEE 6th Int. Symp. On Spread-Spectrum Tech. & Appl (ISSSTA 2000), NJ, USA, pages 132-136, September 2000

  The object of the present invention is a multi-user cellular with a higher ability to detect a single signature compared to the known prior art, especially in the presence of several other simultaneous signatures, at low SIR values. A method and system for uplink synchronization in a communication system is provided.

  According to the present invention, a signature sequence is transmitted from a second transceiver to a first transceiver, the signature sequence is selected from a first signature sequence set, and the received signal is transmitted between the second transceiver and the second transceiver. Correlated with at least one signature sequence in the first transceiver to synchronize transmissions to and from one transceiver. The invention is characterized in that the signature sequence is generated from a Zadoff-Chu sequence having at least a partly zero correlation interval. The signature sequence can be selected from a group of signature sequences.

  This allows for good autocorrelation characteristics to allow accurate timing estimation, good cross-correlation characteristics that allow accurate timing estimation of different and simultaneously present signature sequences In addition to preserving favorable characteristics of prior art signature sequences, such as small peak-to-average power ratio, zero cross-correlation, or substantially zero cross-correlation for simultaneously occurring and coexisting signature sequences This increases the detection probability of a particular signature sequence substantially as the sequences are easily distinguished from each other. The improved detection probability has the additional advantage that in the case of having multiple simultaneously transmitted signature sequences, the number of retransmissions that must be performed due to a detection failure is reduced, thus making the system resources more Used efficiently. In addition, it is becoming increasingly important to have quick access to the network and the ability to transmit data quickly using high power. This improved detection capability allows for faster detection of specific mobile terminal devices desiring to transmit data, thereby facilitating interoperability with the IP protocol.

  The use of signature sequences according to the present invention, while the signal level of one signature sequence is strong, for example due to distance, shadowing, or (probably most likely) rapid fading, It has the further advantage that the probability of correct detection is substantially improved even if the signal level of the substantially simultaneous signature sequence is considerably weaker.

  The zero correlation interval of the first signature sequence can be of a length that substantially corresponds to the maximum expected delay from the second transceiver to the first transceiver. Furthermore, the received signal can be correlated with at least one signature sequence, for example over a predetermined number of delays of the signal corresponding to the maximum expected delay. This delay can be calculated using the cell size. This has the advantage that a desired length of zero correlation interval can be obtained, so that the number of signature sequences provides the required zero correlation interval length. It can be changed. The greater the sequence, the shorter the zero correlation interval.

  A set of matched filters is used in the first transceiver to correlate the received signal with at least one signature sequence, or each signature sequence in a group of signature sequences, over a predetermined number of delays of the signal And when the correlation is taken, the peak power from each matched filter is detected, after which the detected peak power from each filter is used to estimate the arrival time and from the second transceiver Transmission is synchronized. This has the advantage that correlation can be performed in a simple manner.

FIG. 2 shows a basic DFT spread OFDM transmitter structure for synchronized data transmission. FIG. 4 is a diagram illustrating absolute values of an autocorrelation function and a cross-correlation function of an exemplary signature sequence according to the present invention. FIG. 3 is a diagram showing a part of the graph of FIG. 2 in more detail. FIG. 6 shows the probability of failure to detect for one transmitted sequence according to the present invention. FIG. 7 shows the probability of failure to detect a transmitted sequence in the presence of one or more other transmitted sequences according to the present invention.

The present invention will now be described in detail in connection with a communication system using DFT spread OFDM. FIG. 1 shows a basic transmitter structure for DFT spread OFDM. A block of M complex modulation symbols X _n , n = 0, 1,..., M−1 is transformed by DFT, resulting in M coefficients X _k .

The output from the DFT is allocated on an equidistant subcarrier, l _k = l ₀ + k _L , where l ₀ is the frequency offset and L is an integer greater than or equal to one. All other inputs to the N-point IDFT (Inverse Discrete Fourier Transform) are set to zero. The output of the IDFT, y _n is given by the following. That is,

  Finally, to avoid ISI (inter-symbol interference) and ICI (inter-channel interference), a cyclic prefix is inserted, i.e. a copy of the last part of each OFDM symbol before the beginning of the same symbol Inserted into. A time window may be applied after the cyclic prefix to reduce out-of-band emissions.

  The cyclic prefix allows equalization in the frequency domain. However, the requirement for successful equalization in DFT spread OFDM and OFDM is that the signals transmitted from all mobile terminal devices in the cell are synchronized, and the delay spread of the signal plus the spread of the arrival time is the same. Is to be less than the duration of the click prefix. Therefore, in order for the mobile terminal apparatus to be able to transmit data, it is first required to be synchronized within a fraction of the cyclic prefix duration.

  As described above, in the first synchronization step in the DFT spread OFDM system, the mobile terminal apparatus performs synchronization using the carrier frequency and frame timing of the base station. This synchronization step ensures that the downlink synchronized mobile can receive the signal from the base station, but compensates for the generally unknown distance between the mobile terminal and the base station, Further synchronization is required to ensure that the station can properly receive the signal from the mobile terminal. A mobile terminal device far away from the base station receives a downlink signal having a larger delay than a mobile terminal device close to the base station, and is propagated to the base station with respect to the mobile terminal device. A signal transmitted in the uplink takes longer time than a signal from a mobile terminal apparatus closer to the base station. When the base station estimates the time taken for the signal transmitted from the mobile terminal apparatus to reach the base station, the base station sends a command to the mobile terminal apparatus to adjust the transmission timing of the mobile terminal apparatus. The transmissions from various mobile terminals can be received at the base station at a desired time.

  An important aspect of the second step of synchronization is that the mobile terminal device is already synchronized with the reception of the downlink signal, and all fluctuations in the arrival time at the base station of the signal transmitted from the mobile terminal device are: This is due to different round trip times. Since the cell size is known, the range of the incoming time is speculatively known at the base station.

  In Enhanced UTRA, RACH (Random Access Channel) in the uplink supports uplink synchronization of the mobile terminal device. RACH is allocated on several resources in time (access slot) and frequency. In each access slot, all transmitted signals arrive within the allotted time and the guard interval is such that the transmitting mobile terminal equipment does not interfere with data transmission no matter where it is located in the cell. Must exist.

  RACH in Evolved UTRA is contention-based, i.e. any mobile terminal in the cell can transmit on the time-frequency resources assigned to RACH, so that multiple mobile terminals can simultaneously Or, substantially simultaneously, it is possible to attempt to transmit a synchronization signal. To reduce the risk that the base station will fail to distinguish signals from different mobile terminals, a set of signature sequences is used, and each mobile terminal is typically 1 in a random manner from the set of signature sequences. Select one signature sequence.

  Since successful detection of this signature sequence is necessary for the mobile terminal device to access the network, the transmitted signature sequence requires a low power amplifier backoff, allowing a high average transmit power, and this It is therefore important to enable a good effective range.

The signature sequence in the uplink must have the following characteristics: That is,
Good autocorrelation characteristics that allow accurate timing estimation,
Good, which allows accurate timing estimation of signature sequences that are somewhat synchronized (i.e. downlink synchronized), where the phase difference is limited by the maximum round trip time in the cell Cross-correlation properties,
Zero cross-correlation for synchronous, simultaneous signature sequences,
A small peak-to-average power ratio.

  These properties are largely met by the RACH signatures in UTRA used today, and at least some of these properties also constitute the current proposal for Evolved UTRA. In UTRA, binary pseudo-random sequences generated by shift registers are modulated by 16-bit Hadamard sequences to generate these signature sequences. In addition, rotation of the signal constellation is applied to reduce the PAPR of the signal.

  Modulation using Hadamard sequences allows to reduce the complexity at the receiver, ie, for each delay, the received signal is multiplied by a complex conjugate of a pseudo-random scrambled sequence. Summed every 16th sample to generate a vector of 16 elements. Finally, the Hadamard sequences are correlated with the received vectors to produce a correlated output of these signature sequences.

  However, the probability of detection of a single signature in the presence of some of these known signature sequence characteristics, such as cross-correlation with each other, i.e. one or more other simultaneous signatures, is particularly low. SIR values can be better.

  According to the present invention, the above-mentioned problems are overcome by using a zero correlation interval sequence, i.e. a signal whose downlink synchronized mobile terminal is a signature sequence from a set of zero correlation interval sequences. Is transmitted.

A set of M sequences of length N, {d _x (k)}, x = 0,1, ..., M-1, k = 0,1, .., N-1 are in this set If all sequences satisfy the following autocorrelation and cross-correlation properties, then it is said to be a set of zero correlation interval sequences. That is,
Periodic autocorrelation function

Is zero for all p, so 0 <| p | ≦ T and the periodic cross-correlation function

Is zero for all p, and therefore | p | ≦ T (including p = 0). T is the length of the zero correlation interval.

In an exemplary embodiment of the invention, the set of zero correlation interval sequences is constructed by using GCL (generalized chirp-like) sequences. The GCL sequence {c (k)} is defined as follows: That is,
c (k) = a (k) b (k mod m), k = 0,1, ..., N-1 (3)
Where N = sm ² , s and m are positive integers, {b (k)} is an arbitrary sequence of m complex numbers of unit size, and {a ( k)} is the Zadoff-Chu sequence,

Where W _N = exp (−j2πr / N) and r is relatively prime to N (ie, the greatest common divisor of r and N is 1).

  Every GCL sequence has an ideal periodic autocorrelation function, ie the GCL sequence is a CAZAC (constant amplitude zero autocorrelation) sequence.

Two GCL sequences, c _x (k) and c _y (k), use the same Zadoff-Chu sequence, {a (k)}, but any different modulation sequence, {b _x (k) } and {when defined using b _y (k)}, periodic cross-correlation, (BM Popovic, "New Complex Space-Time Block Codes for Efficient Transmit Diversity", IEEE 6th Int. Symp. on Spread- Spectrum Tech. & Appl (ISSSTA 2000), NJ, USA, pages 132-136, in a manner similar to that disclosed in September 2000) All time shifts in the delay interval, p,
0 <| p | <sm, sm <| p | <2sm, ..., (m-1) sm, <| p | <sm ²
Can be shown to be zero.

  Thus, if the two modulation sequences described above are orthogonal, the resulting GCL sequence is not only orthogonal, but also has a zero correlation interval of length sm-1.

Based on this property, a set of m zero correlation interval sequences is obtained by different m orthogonal modulation sequences, {b _i (k)}, i = 0,1,2, ..., m-1, k = 0,1,2, ..., m-1 is used to define a general Zadoff-Chu sequence, a set of GCL sequences obtained by modulating {a (k)} Is possible. The periodic cross-correlation between any two sequences from this set is zero for all delays between -sm and + sm.

  A sequence from the set of zero correlation interval sequences is used as the synchronization signature. Although the matched filter for such signatures actually calculates the non-periodic cross-correlation, the ideal periodic cross-correlation characteristics within the search window are expected to be largely preserved. The reason is that for delays in the search window that are much smaller than the length of the sequence, the sum for the aperiodic cross-correlation values and the sum for the periodic cross-correlation values differ only in a few terms. This prospect is confirmed by numerical evaluation, as will be shown later.

  With respect to the GCL sequence, possible options for the selection of the orthogonal modulation sequence are, for example, a set of Hadamard sequences or a set of DFT (Discrete Fourier Transform). The set of DFT sequences is defined as follows: That is,

On the other hand, a set of Hadamard sequences is defined as a row (or column, or possibly both row and column) in an mxm Hadamard matrix, as defined below. That is, the Hadamard matrix H _{m of} order m consists only of 1s and -1s and has the characteristic H _m H _m ^T = mI, where I is the identity matrix and ^T represents the transpose . For this reason, the Hadamard sequences are orthogonal. For m = 2 ⁿ , where n is a positive integer, a Hadamard sequence can be defined as follows: That is,

Here, i ₁ and k ₁ are bits in binary representation of integers i and k having a m-bit length.

  The actual numbers m and N can be selected to meet the requirements of Evolved UTRA. For a given length of the sequence, there is then a trade-off between the length of the zero correlation interval and the number of signatures that can be provided.

For example, for a 1.25 MHz bandwidth in Evolved UTRA, an exemplary time available for signature sequence transmission is 500 microseconds, with a guard time of about 110 microseconds, and the duration of the sequence is 390 microseconds It is. For example, assuming a sampling rate of 1.024 MHz, the length of these sequences is N = 400 = sm ² .

  The cell size is generally known, and as a result, the maximum time difference between signals from two mobile terminal devices in the cell (i.e., the addition to one mobile terminal device relative to the other mobile terminal device). And the additional propagation time from one mobile terminal device) are also known. Advantageously, the zero correlation interval length is adapted to this time difference, i.e. adapted to obtain a low correlation for all possible time differences up to the maximum possible time difference. For example, when the cell size is 14 km, the maximum transmission time for a signal corresponds to 96 symbols on the assumption described above. A low cross-correlation in this delay range is guaranteed when sm = 100, according to what has been described above, so that m = 4 and s = 25 (larger m is shorter, This results in an unsatisfactory zero correlation interval length). For simplicity, q = 0 is selected in Equation (4). However, it should be understood that other values of q may be used. A non-zero q causes a sequence shift. For this reason, there are four different signature sequences of length 400.

  FIG. 2 shows the absolute values of the sequence autocorrelation function and the cross-correlation function for the received signal.

aperiodic cross-correlation function, where p is the delay and " ^* " represents the complex conjugate

Is shown in FIG. 2 for a DFT modulated GCL sequence with N = 400 (s = 25 and m = 4) and r = 1.

  The set of Hadamard modulated GCL sequences has autocorrelation and cross-correlation functions similar to those shown in FIG. The peak of the cross-correlation function is located near a multiple of sm = 100. Those peaks show some spread, i.e., correlation values near multiples of sm have substantial non-zero values that do not exist for the periodic cross-correlation function. However, for a given parameter, the cross-correlation function does not exceed 20 for delays less than 96. Thus, for a 14 km size cell, only the portion of the plot up to p = 96 is of interest, and within this interval the correlation results are obvious. The portion of the plot of FIG. 2 showing the delay from 0 to 100 is shown in more detail in FIG.

  The actual synchronization uses a set of matched filters to correlate the received signal with the signature sequence in the set of signature sequences for all delays in the search window, and the peak output from each matched filter is Executed by the detecting base station. A threshold is used to reduce the probability of false detection, i.e., the threshold is set to a value that results in a detection with a certain probability, e.g. 0.0001, if the received signal consists only of noise.

  Next, the detected peak output from each filter is used to estimate the arrival time, ie, the delay, and the transmission from the mobile terminal apparatus is synchronized.

  The comparison signal at the base station may be aperiodic, i.e. may consist of only one period. Alternatively, this signal may be periodic, i.e. consist of a part of one or both periods in addition to one period. If a periodic signal is used, the threshold must be increased because the probability of false detection increases. On the other hand, robustness is enhanced when there are multiple signature sequences. Furthermore, of course, it is also possible to extend the signature sequence transmitted by the mobile terminal device by a part of the period on one or both sides of the sequence. The length of this further part can be determined by the time available to transmit the signature sequence.

  In one embodiment of the invention, all cells in the system are given the same number of signature sequences, and preferably this number is selected based on the largest cell in the system. However, as will be apparent, the specific signature sequence may vary from cell to cell. This has the advantage that when a mobile terminal device exists at the boundary between two cells, it can be determined which cell the mobile terminal device tries to connect to. If neighboring cells have the same set of signature sequences, two or more base stations may attempt to answer the call from the mobile terminal. On the other hand, it can be determined which base station provides the best signal quality, so that it can be determined which base station to respond to. . However, as is also evident from the foregoing, it is possible to have different signature sequence sets in different cells. Various signature sequence sets can be easily obtained by changing r. Which r value should be used can be transmitted to the mobile terminal device, so that the mobile terminal device can generate a set of signature sequences according to the above equation. Furthermore, if the cell size is smaller, the number of signature sequences can be increased while keeping the sequence length. For example, if the cell size is 7 km, the number of delay steps required is only half of the previous example. Thus, m can be set to 7 and s can be set to 8. Doing this results in a signature sequence of length 392 and 7 signature sequences during the cell size requirement, ie, sm-1 = 55 steps. In this example, the aforementioned guard time is maintained. However, it is also possible to reduce the guard time in smaller cells to allow longer signature sequences and consequently more sequences.

  The detection performance of these proposed signature sequences, ie, preambles, has been evaluated by link level simulation. To preserve the same number of signature sequences as in the proposed sequence, the truncated WCDMA RACH preamble is a modulated Hadamard sequence that is 4 bits long, instead of a 16 bit length sequence, Used as a reference. The number of receive antennas is 2, and the correlation from the two antennas at the same delay is combined incoherently, i.e. the squared matched filter output from the two antennas at the same delay. The absolute value is added. The number of trials is 100,000.

  Two scenarios were simulated. In both scenarios, the detector correlates the received signal with all possible signature sequences within the search window. The threshold is set to provide a false alarm probability of 0.0001 for a signature sequence at a single delay. If the transmitted signature sequence is not detected, a detection failure is declared.

  In the first scenario, only one preamble is transmitted in time-frequency resources for RACH. The delay is randomly distributed in the search window corresponding to randomly distributed mobiles in the cell, i.e. in this example, ranging from 0 samples to 96 samples.

  In the second scenario, two or more different signature sequences from the same set are transmitted on the same time-frequency resource. The SNR of signature S1 is fixed (SNR = -15 dB), and other interference signatures are transmitted with various power offsets relative to signature 1. However, all interference signatures are transmitted with the same power. All signatures are transmitted with an independent random delay within the search window. The probability of failure to detect a weaker signal, signature S1, is recorded. SIR is the ratio of the power of signature S1 to the power of any of the interference signatures.

  The simulation results for scenarios 1 and 2 are shown in FIGS. 4 and 5, respectively. Figure 4 shows the probability of detection failure for one transmitted sequence, and Figure 5 shows the probability of failure to detect one transmitted sequence in the presence of another transmitted sequence. Is shown. From FIG. 4, it is clear that in the case where there is no interference sequence, there is no difference in the probability of failure in detection compared to the prior art. Thus, in this situation, the signature sequence according to the present invention exhibits similar performance as the prior art sequence.

  However, for the second scenario involving two or more simultaneously or substantially simultaneously transmitted sequences, the result shown in FIG. 5 is that for a set of sequences according to the invention, one or several interference sequences Clearly demonstrate significantly improved detection performance in the presence of. For the proposed sequence set, the detection performance does not change in situations with more interference, even for very low SIR values, whereas for the control sequence, the performance increases as the number of interferences increases. However, even if the SIR decreases, it decreases significantly. This significant difference is that when a strong signal and a weak signal are present at the same time, some parts of the stronger signal are interpreted as part of the weaker signal during correlation, It can be explained at least in part by the condition that it is interpreted with a miscalculated delay. The use of the signature sequence according to the present invention, as can be seen in FIG. 5, is correct detection even when the signal level of one signature sequence is strong while the signal level of substantially simultaneous signature sequences is considerably weaker. This has the advantage that the probability of

  The decrease in the probability of detection failure shown for the proposed sequence set is due to the good cross-correlation properties of the zero correlation interval sequence, and thus the present invention provides a significant improvement over the prior art. Furthermore, this improvement in detection probability by using a zero correlation interval sequence can reduce transmit power for the RACH preamble, reduce overall interference in the system, and extend battery life. it can.

  Furthermore, in the foregoing description, the present invention has been described as utilizing a complete zero correlation interval sequence. However, it is also possible to use censored sequences, ie sequences that are not all zero correlation interval sequences can be used. Doing so reduces the detection probability, but has the advantage of greater freedom in choosing the number of signature sequences due to the increased specific signature length. The truncation can vary depending on the cell size, and in smaller cells a larger truncation can be tolerated with satisfactory performance.

  As mentioned above, the present invention has several advantages. However, there are other features that need to be considered for the system to work properly. For example, as mentioned above, it is important that the transmitted signature sequence requires a low power amplifier back-off to allow a high average transmit power, thereby allowing a good coverage. Two measurements related to power backoff are PAPR (peak to average power ratio) and CM (cubic metric).

  In the following, the influence of the invention on these measurements is disclosed.

Let z (t) be a normalized baseband signal so that the expected value E (| z (t) | ² ) = 1 of this signal. The PAPR at the 99.9th percentile is defined as a value x such that the probability of 10log ₁₀ (| z (t) | ² ) <x is 0.999.

CM is defined as follows:
CM = [20log ₁₀ ((v_norm ³ ) _rms ) -20log ₁₀ ((v_norm_ref ³ ) _rms )] / 1.85 (7)
However,
−v_norm is the normalized voltage waveform of the input signal,
-V_norm_ref is a normalized voltage waveform of the reference signal (12.2 kbps AMR Speech in WCDMA (registered trademark)).

  Table 1 shows the PAPR values at the 99.9th percentile for a reference WCDMA® RACH preamble truncated to 400 samples using a 4-bit Hadamard modulation sequence, and a GCL sequence using DFT and Hadamard modulation sequences. List up. Table 2 lists the corresponding CM values.

  In all cases, the maximum PAPR value is given across all modulation sequences. The range of values given for the WCDMA® RACH preamble spans all scramble codes. For GCL sequences, a Zadoff-Chu sequence with r = 1 was used. This particular example of the value of r should be understood to be merely exemplary. A root raised cosine filter with two different pulse shaping filters, a simple sync filter and a roll-off rate of 0.15 is applied.

  From these tables it is clear that DFT modulated sequences have lower PAPR and cubic metric compared to Hadamard modulated GCL sequences. Furthermore, applying a root raised cosine filter does not improve the PAR or cubic metric of DFT modulated sequences.

  Finally, the PAPR of DFT-modulated GCL sequences is as good as that of WCDMA sequences using root raised cosine filters, while cubic metric is the case of WCDMA sequences. It is somewhat better than. Obviously, it is possible to find a set of zero correlation interval sequences that allow low power backoff.

Claims (17)

A method for performing uplink synchronization between a first transceiver and a second transceiver in a multi-user cellular communication system comprising:
Receiving by the first transceiver a signal comprising a first signature sequence selected from a first signature sequence set, the signal for the uplink synchronization provided by a second transceiver;
In order to synchronize transmission between the second transceiver and the first transceiver, at the first transceiver, the received signal is at least one second selected from a second signature sequence set. Correlating with two signature sequences,
The method of claim 1, wherein the first signature sequence set is generated by modulating a Zadoff-Chu sequence using an orthogonal modulation sequence. The method of claim 1, wherein the length of the zero correlation interval substantially corresponds to an expected maximum delay of transmission from the second transceiver to the first transceiver. The method of claim 2, wherein a cell size is used to calculate the expected maximum delay of the transmission from the second transceiver to the first transceiver. The method according to any one of claims 1 to 3, wherein the first signature sequence is randomly selected from the first signature sequence set. The method according to any one of claims 1 to 4, wherein the first signature sequence set and the second signature sequence set are the same signature sequence set. Further comprising transmitting a reference representative of a particular signature sequence set to the second transceiver;
The method according to any one of claims 1 to 5, wherein the criterion is used by the second transceiver to obtain a signature sequence set scheme to be used. The said 1st signature sequence is used as a preamble part of the signal transmitted to a base station by a mobile terminal device via a random access channel, The Claim 1 characterized by the above-mentioned. The method described. The method according to any one of claims 1 to 6, wherein the first signature sequence is used as part of a synchronization signal transmitted by a mobile terminal device to a base station. A multi-user cellular communication system having communication resources for communication between at least a first transceiver and a second transceiver,
A multi-user cellular communication system, characterized in that the communication system comprises means for carrying out the method according to any one of claims 1 to 8. A system,
Means for receiving a signal comprising a first signature sequence selected from a first signature sequence set, the signal for performing uplink synchronization provided by the transceiver;
Means for correlating the received signal with at least one second signature sequence selected from a second signature sequence set to synchronize transmission between the transceiver and the system. And
The system of claim 1, wherein the first signature sequence set is generated by modulating a Zadoff-Chu sequence using an orthogonal modulation sequence. The system of claim 10, wherein the first signature sequence set and the second signature sequence set are the same signature sequence set. Means for transmitting a reference representing a particular signature sequence set to the transceiver;
12. A system according to claim 10 or claim 11, wherein the criteria is used by the transceiver to obtain a signature sequence set scheme to be used. The method according to any one of claims 10 to 12, wherein the first signature sequence is used as a preamble portion of a signal transmitted to a base station by a mobile terminal device via a random access channel. The described system. The system according to any one of claims 10 to 12, wherein the first signature sequence is used as part of a synchronization signal transmitted by a mobile terminal device to a base station. A transmitter for use in a multi-user cellular communication system comprising:
Means for selecting a first signature sequence from the first signature sequence set;
Means for transmitting to the receiver a signal for uplink synchronization between the transmitter and the receiver;
The signal comprises the first signature sequence;
The transmitter according to claim 1, wherein the first signature sequence set is generated by modulating a Zadoff-Chu sequence using an orthogonal modulation sequence. The transmitter according to claim 15, wherein the first signature sequence is used as a preamble part of a signal transmitted to a base station by a mobile terminal device via a random access channel. The transmitter according to claim 15, wherein the first signature sequence is used as a part of a synchronization signal transmitted by a mobile terminal device to a base station.