Synchronization channel interference cancellation in a wireless network

Abstract

Method for wireless communication in a radio communication system comprising multiple base stations, the method comprising: (a) Synchronizing to one of the several base stations using a synchronization channel transmitted by that base station; (b) Receiving a pilot channel from the base station; (c) after synchronizing with the one base station, receiving a signal from that base station; (d) Using the base station pilot channel to cancel out any disturbance in the signal caused by the synchronization channel, wherein the cancellation includes (da) Performing a channel estimate based on the pilot channel; (db) Estimating a symbol received in the synchronization channel a k , where a k a coded symbol that is transmitted via code k; (dc) Using the estimated symbol ak and the channel estimation to estimate the gain of the synchronization channel; (dd) Using the profit for the aforementioned extinction, using the same estimate of symbol a k is used across multiple time slots of the synchronization channel, for which a disturbance in the signal is canceled out.

Description

Field of invention

[0001] The present invention relates to interference or disturbance caused by synchronization channels in a wireless radio communication system. background

[0002] The use of primary and secondary synchronization channels in the 3GPP-WCDMA system allows the user facility to achieve initial synchronization with the service cell. Once this step is completed, the synchronization channels are not always needed, but their presence causes interference on the other channels.

[0003] The 3GPP wide-area CDMA (WCDMA) system uses orthogonal variable spreading (OVSF) codes to enable multiplexing, or bundling, of different channels and multiple access for sharing resources between users. Due to the orthogonality of OVSF codes, their use means that no intermediate code interference is generated.

[0004] An exception to this are the primary and secondary synchronization channels (PSCH and SSCH), which are not scrambled with the cell-specific scramble code (Section 5.3.3.5, 3GPP TS 25.211, "Technical Specification Group for Radio Access Network; Physical Channels and Mapping of Transport Channels to Physical Channels (FDD)," December 2005). All other channels besides the synchronization channels are assigned OVSF codes and then scrambled or encrypted. The scramble sequence is a pseudo-random sequence designed to randomly distribute inter-cell interference. Because the OVSF codes are scrambled with the same scramble code, they remain orthogonal. The synchronization channels, on the other hand, are not scrambled (and are also assigned different codes), and thus do not remain orthogonal. This means that the synchronization channels are susceptible to interference or encryption.This can cause interference in the remaining channels.

[0005] FR 2 865 603 A1 relates to a method for suppressing intracellular interference generated by synchronization channels transmitted from a base station to a mobile terminal in a cellular telecommunications network. The method comprises the following steps: estimating the propagation channel characteristics of a total signal received by the terminal; estimating the contribution of the synchronization channels transmitted by the base station to the total signal received by the terminal; and subtracting the estimated contribution from the total signal for each propagation path. overview

[0006] The proportion of power allocated to synchronization channels, such as PSCH and SSCH, is typically small, and in the past, the effect of interference from these channels was considered negligible. However, to maximize performance, particularly with the latest categories introduced in Issue 7 for 64-QAM constellation support and MIMO (Multiple Input Multiple Output) mode, this interference can indeed be significant. That is, the presence of synchronization channels can create interference for other channels, resulting in a degrading performance, especially under the conditions required to achieve the highest data rates. It would therefore be desirable to take steps to mitigate such interference.To manage interference through synchronization channels.

[0007] To solve this, the present invention provides a synchronization channel cancellation method that takes advantage of the presence of an existing pilot channel to cancel out a disturbance or interference from a synchronization channel.

[0008] According to one aspect of the present invention, a method for wireless communication in a radio communication system comprising multiple base stations is provided, the method comprising: synchronizing to one of the base stations using a synchronization channel transmitted by that base station; receiving a pilot signal from the base station; after synchronizing to the base station, receiving a signal from the base station; and using the pilot channel from the base station to cancel out interference or disturbance in the signal caused by the synchronization channel.

[0009] In embodiments, the communication system is a code-division multiple-access communication system, wherein each base station operates according to a different corresponding scrambling code that differs from that of several other base stations; the synchronization channel is not scrambled by any of the scrambling codes and thus does not cause interference in this signal; and the cancellation comprises using the pilot channel from said base station to cancel out interference in the signal caused by the non-orthogonality of the synchronization channel.

[0010] The aforementioned cancellation may include: performing a channel estimate based on the pilot channel; estimating a symbol received in the synchronization channel; using the estimated symbol and the channel estimate to estimate a gain of the synchronization channel; and using the gain to cancel out the interference or disturbance in the signal caused by the synchronization channel.

[0011] The symbol can be estimated by: unspreading the synchronization channel, estimating a correlation between the unspread synchronization channel and the pilot channel, estimating a power of the pilot channel, and estimating the symbol based on the correlation and the pilot channel power.

[0012] The symbol in question can be estimated by applying a predetermined knowledge of the symbol's structure.

[0013] Estimates of the correlation and / or the pilot channel power can be averaged over multiple time slots.

[0014] The same estimation of the said symbol can be used across multiple time slots of the synchronization channel, for which the corresponding interference or disturbance in the signal is canceled out.

[0015] The pilot channel can be a shared pilot channel. The communication system can be a WCDMA system, and the shared pilot channel can be a CPICH.

[0016] The said synchronization may include synchronizing to the base station using multiple synchronization channels; and the cancellation may include using the pilot channel from that base station to cancel out the interference or disturbance in the signal caused by the multiple synchronization channels.

[0017] The said synchronization may include synchronizing to the base station using a primary and secondary synchronization channel; and the said cancellation may include using the pilot channel from the said base station to cancel out any interference or disturbance in the said signal caused by the primary and secondary synchronization channels.

[0018] The communication system can be a WCDMA system, and the primary and secondary synchronization channels can be a PSCH and an SSCH, respectively.

[0019] According to a further aspect of the present invention, a program product for wireless communication in a radio communication system comprising multiple base stations is provided, wherein the program has a code or encoding which is formed on a computer-readable medium and configured such that, when executed in a user device, it performs any one of the above method features.

[0020] According to a further aspect of the present invention, a user device or application device for wireless communication is provided in a radio communication system comprising several base stations, wherein the application device comprises: a receiver configured to receive a synchronization channel and a pilot channel transmitted by one of the base stations; a processing unit coupled to the receiver and configured to synchronize with the base station using the synchronization channel; wherein the receiver is configured to receive a signal from the base station after synchronization with that base station; and wherein the processing unit is configured to use the pilot channel from the base station to cancel out any disturbance or interference in the signal caused by the synchronization channel.

[0021] The processing unit can also be configured to perform any of the preceding process features. Brief description of the drawings

[0022] For a better understanding of the present invention and to show how it can be implemented, reference is now made to the accompanying drawings, which: Fig. 1 is a schematic representation of a radio communication system; Fig. 2 is a schematic block view of a transmit-receive chain with synchronization channels; Fig. 3 is a schematic representation of the block structure or frame structure of a channel; Fig. 4 is a schematic representation of the structure of a synchronization channel (SCH); Fig. Figure 5 is a flowchart showing an algorithm for synchronization channel cancellation. Fig. 6 is a schematic block view of a synchronization channel cancellation and a receive processing block of a UE; Fig. 7 is a graph that shows BLER behavior for the highest category 10 of transport block sizes; and Fig. Figure 8 is a graph showing BLER performance behavior for transport block sizes with highest category 14. Detailed description of preferred embodiments

[0023] As previously mentioned, the 3GPP WCDMA system uses OVSF codes to enable multiplexing (bundling) of different channels and multiple access for resource sharing between users. The use of OVSF codes does not cause intercode interference, with the exception of the primary and secondary synchronization channels (PSCH and SSCH), which are not scrambled with the cell-specific scrambling code and are therefore no longer orthogonal to the rest of the channels, thus causing interference. The power sharing allocated to these channels is generally low.However, in order to achieve the highest possible performance, especially in the case of the latest categories introduced in Issue 7 for support of the 64-QAM constellation and the MIMO (Multiple Input Multiple Output) mode, this interference or disturbance should be avoided, and this can be accomplished by canceling out the synchronization channels from the received signal.

[0024] In preferred embodiments of the present invention, a novel synchronization channel cancellation method is provided which advantageously utilizes the presence of the existing reference pilot channel (CPICH) to achieve near-complete cancellation. This can also be achieved with a reduction in complexity compared to existing methods that do not use the CPICH channel.

[0025] The problem of disruption or interference by synchronization channels is now discussed in more detail in connection with the Fig. 1 to 4 are described in the context of a WCDMA system. However, it should be noted that the problem of interference can also arise from synchronization channels in any radio system, and a similar solution of cancellation based on a pilot channel can be applied in light of the present disclosure.

[0026] Those skilled in this field know that a code-division multiple access (DCMA) system spreads different signals using different corresponding spreading codes to enable these signals to be transmitted at the same frequency and at the same time across the same area. This spreading is achieved by multiplying each bit of the signal by a corresponding spreading code such that each bit of information is represented by a larger number of binary subblocks or binary chips. The desired signal can then be identified from the other signals based on the knowledge of its corresponding spreading code.

[0027] According to Fig. 1 In a radio system using CDMA, each cell 102 is served by a corresponding base station 104, and each base station can transmit a number of different special channels to different corresponding user facilities (UEs) 106 using different corresponding OVSF spreading codes, which are referred to as channeling codes. Each base station can also transmit one or more pilot channels using one or more additional corresponding channeling codes. The main purpose of a pilot channel is to be used as a reference to enable the UE 106 to perform a channel estimation. Such pilot channels can be common pilot channels that can be accessed by all UEs 106 in the cell 102 (as opposed to associated channels that are reserved for a specific corresponding receiving UE).

[0028] The OVSF channeling codes are chosen so that they are mutually orthogonal to each other in the same cell, which means that channels transmitting from the same cell and spread using different OVSF codes do not interfere with each other.

[0029] Each base station also scrambles each of its associated channels and the common pilot channel using a further spreading code, known as the scrambling code. Each base station uses its own unique scrambling code, which is characteristic of that base station (at least within a certain area). A base station can also be referred to as a "Node B" in WCDMA technology; however, the more general term "base station" is used throughout this text to encompass WCDMA Node B or other types.

[0030] The scrambling codes between different base stations (cells) are not orthogonal, and there is no good reason for them to be for the following reasons. Within the same base station, OVSF codes are assigned to all channels except the synchronization channels and then scrambled. The scrambling sequence is a pseudo-random sequence designed to randomly distribute inter-cell interference. Because the OVSF codes are scrambled with the same scrambling code, they remain orthogonal.

[0031] However, the synchronization channel is not scrambled with the scrambling code. The synchronization channel is required for a UE 106 to initially search for and synchronize with a base station 104 before establishing a connection. Part of this process is to enable the UE to obtain the cell's encryption code, and therefore, the synchronization channel itself cannot be spread by the scrambling code. This has the side effect that the synchronization channels are not orthogonal to the other channels, and thus the other channels are subject to interference from the synchronization channel. Since the OVSF codes are scrambled with the same scrambling, they remain orthogonal, as already mentioned; the synchronization channels, on the other hand, are not scrambled (and are also assigned to other codes) and are therefore not orthogonal.

[0032] As schematically in Fig. As shown in Figure 2, the 3GPP WCDMA synchronization channel SCH actually contains two subchannels, namely the primary synchronization channel PSCH and the secondary synchronization channel SSCH. These are processed by multiplexing to the other channels, or bundled onto them, for transmission by the base station 104. As shown in Fig. As shown in Figure 3, in a WCDMA system a channel is typically divided into several frames or blocks (typically 10 ms), and each block is further subdivided into several slots or time slots (typically 15). The SCH synchronization channel has such a structure according to the 3GPP standard, where each slot has a length of 2560 signal parts or subblocks or chips. Fig. Figure 4 schematically shows the structure of an SCH block.

[0033] The primary SCH contains a modulated code of length 256 subblocks, which is called the primary synchronization code (PSC) and Fig. 4 as c 1 is designated.

[0034] This primary synchronization code (PSC) is transmitted once in each timeslot, but only in the first 256 sub-blocks. The PSC is the same for every cell 102 in the system.

[0035] The secondary SCH contains a repeated sequence of 15 modulated secondary synchronization codes (SSCs), each with a length of 256 subblocks or chips. These are transmitted in parallel with the primary SCH. The SSC is known as c 2,m in Fig. 4 denotes, where m = 0, 1, ..., 14 is the number of time slots. Each SSC is selected from a group of 16 different possible codes, each with a length of 256. This sequence on the secondary SCH indicates to which scrambling code group the cell's downlink scrambling code belongs. Therefore, the sequence c 2 characteristic of cell 102 and is used to identify the scramble code for this cell 102.

[0036] The primary and secondary synchronization codes transmit a symbol "a", as shown in Fig. 4 is shown and explained in more detail below.

[0037] As previously explained, since the synchronization channel SCH is not scrambled with a scrambling code, it can interfere with received downlink signals transmitted from the base station 104 to the UE 106. The following describes an algorithm according to a preferred embodiment of the present invention that improves the cancellation of interference from the synchronization channels and has only a minor impact on complexity.

[0038] First, a certain notation is introduced. The received signal y i The downward link WCDMA, which is sampled at sub-block time i, can be modeled as follows: yi=h∑k=1Kcikak+ni where h is the channel gain n i the thermal noise plus the inter-cell interference cik, the spread and scrambled sequence of the code k and a kThe coded symbol is transmitted via the code k.

[0039] In the notation used herein, one code corresponds to 1 (ci1) the PSCH sequence and code 2 (ci2) This corresponds to the SSCH sequence of the service node B. The remaining channels are assigned the code indices 3 to K, and the common pilot channel CPICH is derived from these channels (Section 5.3.3.1, 3GPP TS 25.211, "Technical Specification Group for Radio Access Network; Physical Channels and Mapping of Transport Channels to Physical Channels (FDD)," December 2005). The main purpose of CPICH is to serve as a reference channel for channel estimation by UE 106. However, embodiments of the present invention take advantage of the presence of this channel to use it for an additional purpose: to detect interference or disturbance from the synchronization channel SCH on a received downlink signal y. i to delete.

[0040] All sequences cik, k = 1,...,K correspond to the unit energy. The synchronization channels are transmitted via the first 256 subblocks or chips of each time slot, where the transmitted symbol a k is exactly the same at all times.

[0041] To simplify the notation, the power outputs on different channels are related to the power output on the CPICH. We denote ĥ as the channel estimate generated using CPICH processing.

[0042] The symbol transmitted on the synchronization channels has the following form: ak=λγk(1+j)2 where j=−1 the imaginary unit and λ = + 1 applies if the primary common control physical channel (P-CCPCH) is transmission diversity encoded, and where λ = - 1 applies if this is not the case.

[0043] γ k = |a k | 2represents the performance difference of code k (k = 1,2) in relation to the CPICH.

[0044] To eliminate the synchronization channels, one can imagine that each time slot creates: zk=1L∑i=1Lcikyi,(k=1,2) where L = 265 is the length of the synchronization sequence. k corresponds to the estimate of profit g k = ha k , composed of the channel and the symbol that appears on the channel k (ĝ k = z k ) is transferred.

[0045] The preferred embodiments of the present invention exploit the fact that the profit g k = ha k can be derived from the CPICH channel estimate h, as soon as a k is known. The symbol a kdepends on the configuration of node B (ratio between CPICH and SCH powers, transmission diversity coding), which is static or semi-static and is fixed at least over a span of several blocks.

[0046] To improve the extinction performance, the accuracy of ĝ should be increased. k This strategy can be improved. However, it has a limitation, as the channel is time-variable and can differ significantly from one time slot to another.

[0047] In the profit g k = ha k Only the channel varies from timeslot to timeslot. The symbol a k However, it depends only on the configuration of node B, which is quasi-static. Therefore, the estimation of g can k This can be made more precise by taking the channel estimate of the CPICH (ĥ) and only the unspreading (z k ) k of the synchronization channel is used to a kto estimate.

[0048] Applying this approach allows for a reduction in complexity when estimating a only once. k at the beginning, or by using a continuous-time approach, where the update rate of a k is reduced. That is, the same estimate of a k can be used across multiple time slots of the synchronization channel, for which a corresponding interference or disturbance on the received signal is canceled out, instead of estimating it separately for each time slot for which the disturbance is canceled out.

[0049] According to the flowchart from Fig. 5. The first step S10 of the algorithm consists of the fact that z 1 and z 2 calculated by spreading the primary and secondary SCH.

[0050] In the second step S20, a is used to estimate kThe correlation between the spread-out SCH channels and the CPICH, as well as the performance of the CPICH, was calculated: Nk=conj(h^)zk,k=1,2 D=|h^|2.

[0051] As is clearly evident, NkD an estimate of a k To improve this estimate, however, in step S30 the numerator and denominator are preferably averaged over several time slots to obtain N k and to obtain D.

[0052] Averaging can be performed, for example, by a simple sum if the estimation is only performed once, or it can be performed using a finite impulse response (IIR) filter if a continuous-time approach is preferred.

[0053] In step S40, the estimate is therefore calculated as follows: a^k=N1D and g^1=h^a^1,g^2=h^a^2.

[0054] As an alternative to step S40, the estimation can be improved by modifying the structure of a k is being exploited. In fact, the following applies: ak=λγk(1+j)2 and (1−j)2ak=λyk where this expression is strictly real. Therefore, a better estimate in step S40 is given by: a^k=(1+j)2real((1−j)N¯kD¯), where real(x) is the real part of the complex value x.

[0055] In the final step S50, the cancellation of the synchronization channels is achieved by subtracting the contribution of the primary and secondary channels at the sub-block level or chip level: yi0=yi−g^1ci1−g^2ci2 where yi0 The signal after subtracting the synchronization channels.

[0056] In the case where the complexity is increased by not calculating z 1 , z 2Since the time slot is reduced for each time slot, it is preferable for the timeslots used to have balanced block indices. Balanced block indices mean that the timeslots used span all possible positions in the block; for example, timeslot 0 of block 0, timeslot 1 of block 1, ..., timeslot 14 of block 14, timeslot 0 of block 15, timeslot 1 of block 16, and so on, are used. The reason for this is that the scrambling sequence applied to the CPICH (and all OVSF codes) is repeated for each block, and using the same timeslot index from each block for calculating the time slot is preferable. 1 , z 2This creates a constant interference pattern or noise pattern that cannot be removed by averaging across blocks. However, averaging across time slot indices (the scrambling changes from time slot index to time slot index) makes it possible to remove this noise.

[0057] The preferred embodiments of the present invention offer the following advantages.

[0058] By applying the preferred embodiments, it is possible according to the invention to achieve almost complete synchronization channel cancellation by improving the estimation of the PSCH and SSCH gain used in the cancellation.

[0059] The present invention further enables a reduction in complexity with respect to existing techniques, since PSCH and SSCH unspreading is not required for each time slot.

[0060] The present invention is applicable to different configurations with multiple antennas, i.e., to the transmit diversity mode, receive diversity mode and MIMO mode.

[0061] Furthermore, the present invention is flexible and can be applied to different receiver structures: a rake structure and an equalizer. In the case of the rake structure, almost the entire performance gain is achieved by applying SCH channel cancellation only to the strongest finger.

[0062] For the computational structure, the algorithm can be applied to each finger of the computational receiver or rake receiver by applying the cancellation to the received signal with the correct delay corresponding to the processed finger. In this case, the channel estimation corresponds to the gain estimation of the finger from the CPICH processing. k It's the same for all fingers.

[0063] When a computational structure is used, applying synchronization channel cancellation to the strongest finger (or to the N) allows r strongest finger in the event that N r (Receiving antennas are used) a restoration of almost all the loss in performance due to the presence of the SSCH and PSCH. In the critical case of a single radiation channel (where the slightest degree of interference is more likely to be required), the entire power loss can be reversed.

[0064] If an equalizer is used, the algorithm can be applied at the equalizer's output. Therefore, h can be estimated by processing the CPICH at the equalizer's output. For a MIMO equalizer, a different h must be estimated for each output current, where the cancellation is performed for each current, but where a k is the same for all streams.

[0065] When the Time-Switching Transmission Diversity (TSTD) scheme is applied to the SCH channels, the channel estimate ĥ generated from the CPICH processing corresponds to the main antenna (Antenna 1) in even time slot indices and the diversity antenna (Antenna 2) in odd time slot indices, thus achieving a match with the TSTD pattern.

[0066] The present invention can be implemented by a SCH cancellation and receive processing block 108 in the UE 106. As shown schematically in Fig. As shown in Figure 6, this block 108 can comprise a SCH cancellation block 114, a SCH processing block 110, and a CPICH block 112, each having an input configured to receive the downlink signal y, and each having an output coupled to the SCH cancellation block 114. The output of the CPICH processing block 112 is coupled to another input of the SCH processing block 110. The CPICH processing block 112 is configured to generate the channel estimate ĥ based on the CPICH in the received signal y. The SCH processing block 110 is configured to perform processing according to steps S10 to S30, as previously described, using the received signal y and the channel estimate ĥ output by the CPICH processing block 112, and to output the symbols a k(k = 1,2) to be output at the SCH cancellation block 114. The SCH cancellation block 114 is configured to perform processing according to step S50, which was previously described, using the channel estimate ĥ, which is output by the CPICH processing block 112, and the symbols a k The SCH cancellation block 114 is configured to execute the resulting signal, which is output by the SCH processing block 110. It is thus designed to forward the resulting signal for further reception processing and finally for output to an output device, such as a loudspeaker.

[0067] Blocks 110, 112, and 114 are preferably implemented as software stored in memory on the UE 106 and executed by a processor on the UE 106. However, the option of implementing some or all of these functions in dedicated hardware is not excluded.

[0068] To evaluate the effectiveness of the solution, detailed simulations were performed. These simulations measure the performance in terms of block error rate (BLER) for defined transport blocks transmitted on the high-speed physical downlink share channel (HS-PDSCH). The simulations assume a channel with additive white Gaussian noise (AWGN) and a compute / receiver / rake / receiver configuration. Fig. Figure 7 shows the performance for the largest transport block size in Category 10 with 16-QAM modulation, i.e., a transport block size of 27952 [3GPP TS 25.321, “Radio Access Network Technical Specification Group; Medium Access Control (MAC) Protocol Specification”, September 2008, Annex A]. Fig. Figure 8 shows the performance behavior for the largest transport block size of category 14 with 64-QAM modulation, i.e. a transport block size of 42192.

[0069] In both figures, the performance is shown as a function of BLER versus geometry. Geometry is the ratio of usable received signal power to noise plus inter-cell noise power. Each figure compares the performance of our proposed synchronization channel cancellation method, in which the CPICH channel estimation "Method 1" is applied, with the reference case where no synchronization channels are present ("no synchronization channel"). The curve "Method 2" corresponds to the case in which CPICH is not used and the gain from SCH channel processing is ĝ k = z k The “Method 3” applies when an additional averaging over two time slots is applied to the gain estimated from the SCH channel processing as in Method 2.

[0070] In the two simulated cases, the proposed use of CPICH shows a significantly better performance ratio compared to cases where the cancellation relies solely on SCH channel processing. Fig. 7 and for a BLER around the 10% point, the proposed method lies within 0.05 dB of the performance behavior of the reference "no synchronization channel". The non-use of the CPICH results in a loss of 0.4 dB at best compared to the reference case. Fig. In 8 the difference is even more pronounced; the proposed method results in only about 0.1 dB loss, while not using the CPICH results in more than 3 dB impairment.

[0071] It should be noted that the embodiments described above are merely examples. The invention is not limited to any specific WCDMA or 3GPP standard, or otherwise. The principle of the invention, based on the use of the pilot signal for cancellation, can be extended, based on the disclosure herein, to any wireless radio communication system in which a synchronization channel causes interference on a signal. For example, the invention preferably takes advantage of the fact that the gain can be derived from the channel estimation determined from the pilot channel, an idea that can be applied to any such system and not only to 3GPP or WCDMA systems. Other configurations and applications of the present invention will be apparent to those skilled in the art from the disclosure herein.The scope of protection of the invention is not defined by the described embodiments, but by the attached patent claims.

Claims

[1] A method for wireless communication in a radio communication system having a plurality of base stations, the method comprising: (a) synchronizing to one of the plurality of base stations using a synchronization channel transmitted by that base station; (b) receiving a pilot channel from the base station; (c) after synchronizing to said one base station, receiving a signal from that base station; (d) using the base station pilot channel to cancel interference in the signal caused by the synchronization channel, the cancellation comprising (da) performing a channel estimation based on the pilot channel; (db) estimating a symbol a received in the synchronization channel k , where a k is a coded symbol transmitted via code k; (dc) Using the estimated symbol ak and channel estimation for estimating a gain of the synchronization channel; (dd) Using the winnings for said cancellation, the same estimate of the symbol a k over several time slots of the synchronization channel for which interference in the signal is canceled. [2] The method of claim 1, wherein the communication system is a code division multiple access communication system, each base station operating according to a different corresponding scrambling code different from that of a plurality of other base stations; wherein the synchronization channel is not scrambled with any of the scrambling codes and thus causes interference in the signal; and wherein the cancellation comprises using the pilot signal from the base station to cancel interference in the signal caused by non-orthogonality of the synchronization channel. [3] The method of claim 1, wherein multiple antennas are used as transmit diversity, receive diversity and MIMO mode. [4] The method of claim 1, wherein the estimation of the symbol is performed by despreading the synchronization channel, estimating a correlation between the despread synchronization channel and the pilot channel, estimating a power of the pilot channel, and estimating the symbol based on the correlation and the pilot channel power. [5] A method according to claim 1 or 4, wherein the symbol is estimated using a predetermined knowledge of a structure of the symbol. [6] A method according to claim 1, 4 or 5, wherein the correlation and / or pilot channel power estimates are averaged over a plurality of time slots. [7] A method according to any one of the preceding claims, wherein the pilot channel is a common pilot channel. [8] The method of claim 7, wherein the communication system is a WCDMA system and the common pilot channel is a CPICH. [9] A method according to any preceding claim, wherein synchronization comprises synchronizing to the base station using a plurality of synchronization channels; and cancellation comprises using the pilot channel from the base station to cancel interference in the signal caused by the plurality of synchronization channels. [10] The method of claim 9, wherein synchronization comprises synchronizing to the base station using a primary and a secondary synchronization channel; and cancellation comprises using the pilot channel from the base station to cancel interference in the signal caused by the primary and secondary synchronization channels. [11] The method of claim 10, wherein the communication system is a WCDMA system and the primary and secondary synchronization channels are a PSCH and an SSCH, respectively. [12] User equipment for wireless communication in a radio communication system having a plurality of base stations, the user equipment comprising: a receiver configured to receive a synchronization channel and a pilot channel transmitted from one of the base stations; a processing unit coupled to the receiver and configured to synchronize with the base station using the synchronization channel, wherein (a) the receiver is adapted to receive a signal from the base station after synchronisation with that base station; (b) the processing unit is designed to use the pilot channel from the base station in such a way that interference in the signal caused by the synchronization channel is cancelled, wherein the processing unit is designed to carry out the cancellation by (ba) performing a channel estimation based on the pilot channel; (bb) Estimating a symbol a received in the synchronization channel k , where a k is a coded symbol transmitted via code k; (bc) using the estimated symbol and the channel estimate to estimate a gain of the synchronization channel; and (bd) using the gain to cancel the interference in the signal caused by the synchronization channel, the same estimate of the symbol a k over several time slots of the synchronization channel for which interference in the signal is canceled. [13] A user equipment according to claim 12, wherein the user equipment is adapted for wireless communication in a code division multiple access communication system, each base station operating according to a different corresponding scrambling code different from that of a plurality of other base stations; wherein the synchronization channel is not scrambled by any of the scrambling codes and thus causes interference in the signal; and wherein the processing unit is configured to cancel the cancellation using the pilot channel from the base station to cancel interference in the signal caused by the non-orthogonality of the synchronization channel. [14] User equipment according to one of claims 12 or 13, wherein the received pilot channel is a common pilot channel. [15] User equipment according to claim 14, wherein the user equipment is configured for wireless communication in a WCDMA system and the common pilot channel is a CPICH. [16] The user equipment of claim 12, wherein the processing unit is configured to perform the estimation of the symbol by despreading the synchronization channel, estimating a correlation between the despread synchronization channel and the pilot channel, estimating a power of the pilot channel, and estimating the symbol based on the correlation and the pilot channel power. [17] User equipment according to claim 12 or 16, wherein the processing unit is configured to estimate the symbol using a predetermined knowledge of a structure of the symbol. [18] User equipment according to claim 12, 16 or 17, wherein the processing unit is arranged to average the estimates of the correlation and / or the pilot channel power over a plurality of time slots before estimating the symbol. [19] User equipment according to one of the preceding claims 12 ff, wherein the processing unit is designed to synchronize to the base station using a plurality of synchronization channels and to perform the cancellation by using the pilot channel from the base station to cancel interference in the signal caused by the plurality of synchronization channels. [20] User equipment according to claim 19, wherein the processing unit is arranged to synchronize to the base station using a primary and a secondary synchronization channel and to perform the cancellation using the pilot channel from the base station to cancel interference in the signal caused by the primary and secondary synchronization channels. [21] User equipment according to claim 20, wherein the user equipment is configured for wireless communication in a WCDMA system and the primary and secondary synchronization channels are a PSCH and an SSCH, respectively. [22] A program product for wireless communication in a radio communication system having a plurality of base stations, the program comprising coding formed on a computer-readable medium and being designed to carry out the method of one of claims 1 to 11 when executed in a user device.

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