US20030206577A1 - Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems - Google Patents

Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems Download PDF

Info

Publication number
US20030206577A1
US20030206577A1 US09813491 US81349101A US2003206577A1 US 20030206577 A1 US20030206577 A1 US 20030206577A1 US 09813491 US09813491 US 09813491 US 81349101 A US81349101 A US 81349101A US 2003206577 A1 US2003206577 A1 US 2003206577A1
Authority
US
Grant status
Application
Patent type
Prior art keywords
processor
atrf
combination
signal
processors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US09813491
Inventor
Joseph Liberti
Shimon Moshavi
Paul Zablocky
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TTI Inventions C LLC
Original Assignee
Telcordia Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/7103Interference-related aspects the interference being multiple access interference
    • H04B1/7105Joint detection techniques, e.g. linear detectors
    • H04B1/71055Joint detection techniques, e.g. linear detectors using minimum mean squared error [MMSE] detector
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/7103Interference-related aspects the interference being multiple access interference
    • H04B1/7107Subtractive interference cancellation
    • H04B1/71072Successive interference cancellation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/7103Interference-related aspects the interference being multiple access interference
    • H04B1/7107Subtractive interference cancellation
    • H04B1/71075Parallel interference cancellation

Abstract

Methods and systems in a wireless receiver for enabling the reception of input signals at varied power levels in the presence of co-channel interference utilizing combinations of space-time adaptive processing (STAP), interference cancellation multi-user detection (MUD), and combined STAP/MUD techniques. In MUD, code, timing, and possibly channel information of multiple users are jointly used to better detect each individual user. The novel combination of adaptive signal reconstruction techniques with interference cancellation MUD techniques provides accurate temporal cancellation of interference with minimal interference residuals. Additional methods and systems extend adaptive signal reconstruction techniques to take Doppler spread into account. STAP techniques permit a wireless receiver to exploit multiple antenna elements to form beams in the direction of the desired signal and nulls in the direction of the interfering signals. The combined STAP-MUD methods and systems increase the probability of successful user detection by taking advantage of the benefits of each reception method. An additional method and system utilizes STAP techniques in the case where no pilot signal is available. This method compares the outputs of various hypothesized STAP solutions.

Description

    CROSS-REFERENCE TO RELATED APPLICATION
  • This application claims the benefit of U.S. Provisional Application No. 60/190,803 filed Mar. 21, 2000.[0001]
  • FIELD OF THE INVENTION
  • This invention relates to wireless communication networks and more specifically to CDMA wireless systems subject to co-channel interference. [0002]
  • BACKGROUND OF THE INVENTION
  • Code Division Multiple Access (CDMA) networks are widely deployed throughout the world. The current implementations of CDMA typically follow the IS-95 industry standards and are referred to as IS-95 wireless systems. With the advent of enhancements to CDMA technology such as third generation CDMA, CDMA2000 and W-CDMA, the deployment of CDMA is expected to increase dramatically. [0003]
  • A typical CDMA system [0004] 100 is shown in FIG. 1. It is divided into a plurality of cells 121. Each cell contains a fixed base station 103. Each base station 103 is connected to a centralized switch or mobile switching center 109 that provides switching capabilities and acts as a gateway to wired networks such as the public switched telephone network (PSTN), the Internet, and other public and private data communications networks. As is known, the base station 103 includes a transmitter 105 and a receiver 107 for communicating with the mobile customers or users.
  • On the customer side, users connect to the wireless network through wireless mobile nodes [0005] 101 that can act as transmitters and receivers. The mobile nodes 101 communicate with the base stations 103 over wireless communications links. The link from a base station transmitter 105 to a mobile node receiver is the forward link 115 (or downlink). The link from the mobile node transmitter to a base station receiver 107 is referred to as the reverse link 113 (or uplink).
  • One advantage of CDMA over other wireless access systems is that all users share the same spectrum at the same time. However, the fact that multiple users occupy the same bandwidth limits performance and capacity. Because the conventional matched filter receiver [0006] 107 does an imperfect job of removing signals from these users, each user in a CDMA system degrades the performance of every other user; this effect is called multiple access interference or MAI. An increase in interference between users can lower the ability of a wireless provider to reuse frequencies, resulting in a reduction of system capacity. Because of the tremendous demand for wireless voice and data services and increased competition between service providers, CDMA network providers cannot afford such a reduction in system capacity. Therefore, wireless providers are continually striving to maximize system capacity, which in turn, requires limiting interference.
  • In CDMA wireless systems, power control is used to control the level of MAI at the base station. By adjusting every user's power so that all user transmissions arrive at the base station at approximately the same level, the base station receiver for each user sees the same amount of MAI, and the link quality is roughly the same for each user. If power control was not implemented, then a single user close to the base station could prevent the conventional CDMA receiver for other users from receiving a usable signal, resulting in the so-called near-far problem. [0007]
  • Power control works reasonably well for currently deployed CDMA wireless systems although limitations in the speed of power control are a constant engineering concern and limit capacity and link quality. However, there are frequently situations where it is desirable to deploy auxiliary receivers that are not the target of mobile station power control. Auxiliary receivers can be used to monitor the health of a CDMA wireless system or assist in geolocation. These auxiliary receivers may even be used by law enforcement and military operators for non-cooperative monitoring of a CDMA system for drug-interdiction, counter-terrorism and international intelligence gathering. In these cases, the auxiliary receiver must contend with a wide range of received power levels. Often the auxiliary receiver may need to receive a signal from a mobile station whose received power level is far below (30 dB or more) below the strongest arriving signal. [0008]
  • A need therefore exists for enabling a user in a CDMA system to receive user signals in the presence of interference from other users when the power level of all co-channel signals is not adjusted to be substantially the same. [0009]
  • SUMMARY OF THE INVENTION
  • In accordance with an aspect of our invention, we combine concepts from space-time adaptive processing (STAP), interference cancellation, and multi-user detection (MUD) in multiple embodiments that are able to extract low-level CDMA signals in dense multi-user environments. The performance of these embodiments depends on the accuracy of the signal reconstruction and cancellation. This is particularly crucial if there is a wide range in received power (e.g., from lack of power control). For example, if there is an interfering signal that is 30 dB stronger than the signal we wish to receive and this signal is cancelled with 90% accuracy (meaning that 90% of the interfering signal power is canceled), then the residual portion is still 20 dB above the desired signal. Thus, in addition to symbol detection accuracy, channel estimation accuracy becomes very important in reducing the cancellation residuals. [0010]
  • Our invention utilizes adaptive temporal reconstruction filter (ATRF) techniques for reconstructing the signal interference. This novel approach permits very accurate channel estimation and signal cancellation. Through our novel use of ATRF, individual multipath components do not need to be tracked and separately estimated. The ATRF recreates the multipath channel structure with accurate amplitude and phase estimates for each component. The use of cost estimation techniques within the ATRF further minimizes cancellation residuals. In addition, cancellation timing errors are mitigated because the filter weights do not need to be exactly centered around the main multipath peak in order to solve for them accurately. [0011]
  • There has been extensive work on combined successive interference cancellation and multi-user detection systems. Much of this work is focused on simple channel estimation techniques, such as averaging the outputs of the conventional detector's correlators in order to estimate the amplitude and phase of signals to cancel. The reasons for this are that this approach is simple to describe, simulate and implement and the focus is most often on applications where power control is available to the receiver. Thus, small inaccuracies in cancellation do not significantly affect the performance. Also, there are only a limited number of multipath components which are strong enough to be worth tracking and canceling. [0012]
  • There has also been some work on channel estimation for MUD with the more theoretical motivation of determining the limits of estimation accuracy. These works have often focused on complex maximum likelihood approaches. Because our invention applies successive interference cancellation to complex, non-discrete multipath channels encountered in the real world, our invention takes transmit filtering into account and compensates for timing errors. Our approach minimizes residuals and estimates all multipath components without the need to track them individually. [0013]
  • Through the addition of STAP, the receiver is able to spatially separate the signals using array (smart antenna) receiver technology. This allows the STAP receiver to place spatial beam pattern nulls on strong interferers. In addition, the STAP receiver combines multipath energy, including both the resolvable multipath that is captured by the rake receiver, as well as unresolved multipath that the rake receiver cannot effectively exploit. We combine these techniques with MUD approaches, where the receiver jointly operates on the received waveform to extract signals for all users simultaneously. By carefully estimating higher level signals and canceling them from the array data for the STAP receivers for lower-level signals, the combined STAP-MUD approach is much more effective than either approach implemented individually. [0014]
  • In multi-user detection (MUD), code, timing and possibly channel information associated with multiple users are jointly used to better detect each individual user. Thus, at the outputs of a conventional MUD detector, each user sees less multiple access interference and enjoys improved performance. One form of multi-user detection known as interference cancellation estimates, reconstructs and subtracts interfering signals out of the received signal. Unlike the traditional CDMA detectors, interference cancellation MUD utilizes information about other users when detecting a single user. One aspect of our invention is the novel combination of these interference cancellation MUD techniques and adaptive minimum cost channel estimation in the reconstruction of signals. This combination improves performance of signal reconstruction including symbol detection accuracy and channel estimation fidelity. [0015]
  • Using this combination, we have demonstrated that the STAP-MUD receiver can operate independently of power control, extracting waveforms that are over 35 dB below the strongest arriving CDMA signals.[0016]
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is a network diagram illustrating a typical wireless CDMA network. [0017]
  • FIG. 2 is a network diagram of an illustrative embodiment of a SIC-MCCE combination system in accordance with our invention. [0018]
  • FIG. 3 depicts an illustrative conventional detector for the combination of FIG. 2. [0019]
  • FIG. 4 depicts an illustrative respread processor for the combination of FIG. 2. [0020]
  • FIG. 5 depicts an illustrative adaptive temporal filter (ATRF) for the combination of FIG. 2. [0021]
  • FIG. 6 is a flow diagram illustrating a method of operation for the SIC-MCCE combination system of FIG. 2. [0022]
  • FIG. 7 is a network diagram of an illustrative embodiment of a SIC-JMCCE combination system in accordance with our invention. [0023]
  • FIG. 8 is a network diagram of an illustrative embodiment of a SIC-MF-MCCE combination system in accordance with our invention. [0024]
  • FIG. 8[0025] a is a flow diagram illustrating a method of operation for the SIC-MF-MCCE combination system of FIG. 8.
  • FIG. 9 is a network diagram of an illustrative embodiment of a PIC-MCCE combination system in accordance with our invention. [0026]
  • FIG. 10 is a flow diagram illustrating a method of operation for the PIC-MCCE combination of FIG. 9. [0027]
  • FIG. 11[0028] a is a partial network diagram of an illustrative embodiment of a PIC-JMCCE combination system comprising an ATRF in each parallel processor in accordance with our invention.
  • FIG. 11[0029] b is a partial network diagram of an illustrative embodiment of a PIC-JMCCE combination system comprising a single ATRF processor in accordance with our invention.
  • FIG. 12 is a network diagram of an illustrative embodiment of a STAP receiver in accordance with our invention. [0030]
  • FIG. 13 is a network diagram of an illustrative embodiment of a stage in a STAP/VSIC-MCCE combination system in accordance with our invention. [0031]
  • FIG. 14 is a network diagram of an illustrative embodiment of a J-STAPSIC combination system in accordance with our invention. [0032]
  • FIG. 15 depicts an illustrative J-STAPSIC stage for the combination of FIG. 14.[0033]
  • DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
  • I. Interference Cancellation MUD Combined with Adaptive Temporal Channel Estimation [0034]
  • Interference cancellation can take the form of either successive interference cancellation or parallel interference cancellation. FIG. 2 depicts one illustrative embodiment of our invention comprising a system [0035] 200 combining successive interference cancellation (SIC) and adaptive minimum cost channel estimation (MCCE) for enabling a CDMA receiver to receive signals at different power levels in the presence of interference from other users. We shall refer to this combination as the SIC-MCCE system. The SIC-MCCE system 200 can be implemented as a component within an auxiliary CDMA receiver or within a CDMA base station receiver system.
  • The illustrative system of FIG. 2 comprises a control processor [0036] 202 and a plurality of processors 204 combining successive interference cancellation (SIC) multi-user detection and adaptive temporal reconstruction filters (ATRF). The plurality of SIC-ATRF processors 204 are arranged in successive stages. At each stage, the next user is decisioned, respread, temporally reconstructed, and subtracted out by the SIC-ATRF processor associated with that stage. The output of the SIC-ATRF processor in the first stage, a cleaned received signal, is used as the input to the SIC-ATRF processor in the second stage and the output of the processor in the second stage is used as input to the processor in the next stage. This arrangement is continued for each stage. The number of stages used by the SIC-MCCE system is determined based on the total number of users for the system.
  • Each SIC-ATRF processor [0037] 204 includes a conventional detector 206, a respread processor 208, an adaptive temporal reconstruction filter (ATRF) 210, and a complex mathematical processor 212. The conventional detector 210 is connected to the respread processor 208 and the mathematical operations processor 212 of the SIC-ATRF processor in the previous stage. For the SIC-ATRF processor 204 in the first stage, the conventional detector 210 is connected to an external entity providing a processed version of the received signal r(t) and to the respread processor 208. The respread processor 208 is in turn connected to the ATRF 210, which is connected to the mathematical operations processor 212. The output of the mathematical operations processor 212 is connected to the conventional detector 208 of the SIC-ATRF processor of the next stage and the mathematical operations processor 212 of the next stage. For the SIC-ATRF processor 204 in the first stage, the mathematical operations processor 212 is connected to the external entity providing a processed version of the received signal r(t) instead of the mathematical operations processor 212 of a previous stage.
  • The exact format of the conventional detector and respread processor will differ based on the modulation, coding, and spreading schemes of the particular CDMA system utilized in the wireless receiver system. Although the conventional detector and respread processor can be designed based on third generation CDMA, CDMA2000, or W-CDMA technology, FIGS. 3 and 4 are block diagrams of the conventional detector [0038] 206 and respread processor 208 of the embodiment of FIG. 2 according to an illustrative IS-95 implementation. In this implementation, the conventional detector can be an IS-95 conventional detector or an IS-95 rake conventional detector.
  • The IS-95 conventional detector [0039] 206, shown in FIG. 3, is a fundamental component of standard IS-95 receivers. The IS-95 conventional detector 206 comprises three parts: a short code despreader 31, a long code despreader 32, and a 64-ary matched filter bank 33. The short code despreader 31 separately multiplies the received signal by the real and imaginary components of the IS-95 short code, denoted by pi(t) and pq(t). The delays of these components are adjusted to match the offset in time of the intended received signal. Next, the resulting despread signals are recombined, using time delays as illustrated in FIG. 3, and multiplied by a local copy of the long code, pl(t) corresponding to the desired user in the long code despreader 32. The long code is also offset according to the expected delay of the arriving signal. The resulting signal is used as input to a 64-ary matched filter bank 33. The 64-ary matched filter bank 33 contains copies of each of the 64 possible Walsh symbols that could be transmitted during a symbol period. The 64 outputs of the matched filter bank contain the squares of the absolute values of the inner products between the signal at the matched filter bank input and each of these 64 potential symbols. This process may be equally accomplished using a Walsh-Hadamard transform. When the IS-95 conventional detector is used alone, the matched filter bank output with the largest value determines the receiver's estimate of the transmitted symbol during a particular symbol period.
  • The IS-95 conventional rake detector, a standard technique employed in practice, embodies several instantiations of the IS-95 conventional detector. Each detector uses the same long and short code, however a different delay is applied to each constituent IS-95 conventional detection. The delays correspond to different multipath components, so that a different IS-95 conventional detector tracks each significant multipath component. The outputs from the 64-ary matched filter banks of each of the IS-95 conventional detectors are combined in the IS-95 rake conventional detector using a non-coherent combining technique. Several non-coherent combining techniques are available; however, a simple example is the equal-gain combiner, in which the power from the corresponding ports from each of the 64 matched filter bank outputs in the constituent IS-95 conventional detectors are added, resulting in 64 new variables. These variables are compared, and the one with the largest power is selected as the receiver's estimate of the transmitted symbol from a 64-ary alphabet. [0040]
  • The respread processor [0041] 208, shown in FIG. 4, is used as a fundamental component of IS-95 receivers employing interference cancellation. The respread processor 208 uses as inputs the symbol decisions obtained from either the IS-95 conventional detector, the IS-95 conventional rake detector, or the IS-95 STAP detector, or other similar sources. The respread processor creates a symbol from the 64-ary alphabet corresponding to the selected symbol. Next the symbol is spread using the IS-95 long code, pl(t), then the result is spread using the complex short code using the offset quadrature method specified in the IS-95 standard. The respread processor then matches the resulting signal to the signal received from the antenna using minimum mean square error techniques.
  • FIG. 5 is a block diagram of the ATRF [0042] 210 of the embodiment of FIG. 2. The ATRF 210 comprises tap weights 62, a tap delay line 61, and a mathematical summing circuit 63. In addition, the ATRF has an MCCE weight update processor 64. This processor may be located within the ATRF or as a separate entity between the mathematical operations processor 212 and the ATRF 210 as shown in FIG. 6. The tap weights contain the amplitude, phase, and multipath structure of the received signal for the kth user. The length of the ATRF should be at least as long as the transmit filter (e.g., for IS-95 the transmit filter is 12 chips in duration), and ideally should be long enough to accommodate the delay spread of the signal (to recreate all multipath components).
  • FIG. 6 shows a flow diagram of the operation of the system [0043] 200 of our invention. After initial processing such as downconversion to baseband is performed on the received signal by an external entity, the control processor 202 orders the user signals according to a pre-defined methodology (step 605 ). The user signals are then assigned to a stage based on the ordering. For example, the signal for user A is assigned to the first stage; the signal for user B is assigned to the second stage; and the signal for user k is assigned to the kth stage.
  • An illustrative methodology ranks signals in descending order of received powers. An advantage of this methodology is that by canceling the strongest users first, the remaining users receive the largest benefit from MAI reduction. In alternative methodology, the control processor identifies signals above a certain threshold without performing a hard ranking of each signal. [0044]
  • Based on the ordering, the control processor [0045] 202 communicates a separate user code to the conventional detector 206 in each stage of the system (step 610). For example, the first stage receives the user code associated with user A. In the first stage of the system 200, the conventional detector 206 despreads the received signal and estimates the symbol transmitted for the identified user, Ŵ1(t)(step 620 ). The technique used in the IS-95 conventional detector and IS-95 rake conventional detector is discussed above.
  • In step [0046] 630, the symbol estimate generated by the conventional detector 206 is mixed with the user codes in the respread processor 208 to generate a scaled estimate of the transmitted signal for the user. Using the scaled estimate as input, the ATRF 210 estimates the channel for the user, (i.e., the multipath components and their associated amplitudes and phases) and reconstructs the signal interference associated with the user signal (step 640). The reconstructed signal for the user is then cancelled from the total received signal r(t) in the mathematical operations processor 212 (step 650). The output of the mathematical operations processor 212 is then input to the SIC-ATRF processor 203 in the next stage of SIC-MCCE system 200. The output is also fed back to the MCCE weight update processor 64. Steps 620 through 650 are successively repeated for each of the k stages.
  • A more detailed description of the basic SIC-MCCE channel estimation and reconstruction performed in the ATRF [0047] 210 is described below. In a preferred embodiment, the adaptive technique used for channel estimation is based on minimum cost estimation techniques.
  • In basic SIC-MCCE channel estimation (step [0048] 640 in FIG. 6), the MCCE weight update processor 64 determines the adaptive filter tap weights 62 that minimize a pre-determined cost function between the received signal and the output of the adaptive filter. In an illustrative mode of operation, the MCCE weight update processor functions as follows. The output of the jth stage is given by: r ( j ) ( l T s ) = r ( l T s ) - k = 0 j - 1 n = 0 N - 1 w k , n s ^ k ( ( l - n ) T s )
    Figure US20030206577A1-20031106-M00001
  • this is expressed in vector form as:[0049]
  • r l (j) =r l −w H B l H
  • where r[0050] l is the vector of received signals at time index I, and samples of the reconstructed waveform are contained in the vector: s ^ k , n = [ s ^ k ( n T s ) s ^ k ( ( n + 1 ) T s ) s k ( ( n + Q - 1 ) T s ) ] S ^ k , l = [ s ^ k , l s ^ k , l - 1 s ^ k , l - N + 1 ] B l H = [ S ^ 0 , l S ^ j - 1 , l ]
    Figure US20030206577A1-20031106-M00002
  • Different weight vectors can be obtained by using minimizing different cost functions, each of which represents the quality of the performance of the SIC stage in some manner. One implementation of the minimum cost channel estimate solution is the minimum mean square error solution. The minimum mean square error solution for the weight vector w is the solution that minimizes the following cost function:[0051]
  • J(w)=|r l (j)|2 =|r l −w H B l H|2
  • which simultaneously minimizes both the residual at the output of the j[0052] th stage of the SIC receiver and the difference between the ATRF filter output and the received data rl. The solution to this problem is obtained using standard techniques, where we obtain:
  • w=(B l H B l)B l H r l H
  • Since this solution minimizes the mean square error between the ATRF filter output and the received data at this input to the stage, this is called the minimum mean square error (MMSE) solution. In an alternate illustrative embodiment of our invention, the channel is estimated jointly over multiple users. We will refer to this combination of a jointly optimized ATRF and SIC multi-user detection as the SIC-JMCCE system. An illustrative multi-stage SIC-JMCCE system is shown in FIG. 7. The SIC-JMCCE system [0053] 700 comprises a similar structure as the SIC-MCCE system. However, in the SIC-JMCCE system 700, the outputs of the respread processors 208 for all previous stages are communicated as inputs to the ATRF filter 710 of the current stage. For example, the SIC-ATRF processor in the third stage of a SIC-JMCCE system uses the output of the first stage respread processor and the second stage respread processor as inputs to the third stage ATRF.
  • The mode of operation in accordance with the SIC-JMCCE system is as described above for the SIC-MCCE system, FIG. 6. However, the channel estimation step [0054] 640 is modified to estimate the channel over multiple users. During channel estimation, the tap weights 62 of the current stage ATRF 710 are determined by jointly minimizing the cost function between the received signal and the sum of the outputs of the ATRFs 710 of previously completed stages. The ATRF 710 for each stage jointly estimates and reconstructs all of the currently detected signals including those detected in previous stages of SIC-JMCCE. Thus, the symbols of a single user are detected in each stage (step 620), but the temporal signal structures of all previous detected users are re-estimated and cancelled at each stage. At step 650, the output of the current stage ATRF 710 consisting of all the currently detected signals is subtracted from the received signal in the mathematical operations processor 212.
  • The above approaches to channel estimation in accordance with our invention reconstruct the temporal structure of the signals. However, these approaches do not take into account the frequency content of the signals. In another illustrative embodiment, the ATRF is extended to take into account Doppler spread. We refer to this combination of SIC multi-user detection and multiple frequency adaptive reconstruction as a SIC-MF-MCCE system. The MF-MCCE ATRF can be implemented either in an independent or joint arrangement. An independent MF-MCCE ATRF is shown in FIG. 8. In this arrangement, a frequency shift processor [0055] 814 is connected between the respread processor 208 and the ATRF 810 in each stage of the system.
  • The mode of operation in accordance with the independent SIC-MF-MCCE system is shown in FIG. 8[0056] a. In this mode, steps 605 through 630 are identical to those described for the SIC-MCCE and SIC-JMCCE systems. However, an additional step (step 835) is added to shift the frequency of the signal output from the respread processor to take into account Doppler spread and un-compensated frequency tracking errors. The output of the frequency shift processor 814 is then used as input to the MCCE weight update processor 64. At step 840, the ATRF 810 estimates the channel using either the basic or joint technique previously discussed. The following is a more detailed description of the operation of the MF-MCCE ATRF in accordance with a preferred embodiment of our invention. ŝk,p,n represents a row vector containing Q samples of the reconstructed signal for user k, from time nTs to (n+Q−1)Ts, and frequency shifted by (p−P/2)/(QTs) Hz: s ^ k , p , n = [ s ^ k ( n T s ) j2π ( p p 2 ) ( n ) / Q s ^ ( ( n + 1 ) T s ) j2π ( p p 2 ) ( n + 1 ) / Q s ^ ( ( n + Q - 1 ) T s ) j2π ( p p 2 ) ( n + Q - 1 ) / Q ]
    Figure US20030206577A1-20031106-M00003
  • r[0057] l represents a row vector containing the Q samples of the received signal, r(nTs) through r((n+Q−1)Ts). Then at stage j, the cleaned signal is:
  • r l (j) =r l −w H B l
  • [0058] where B l = [ A 0 , l A l - 1 , l ] , A k , l = [ S ^ k , o , l S ^ k , P - 1 , l ] , S ^ k , p , l = [ S ^ k , p , l + N / 2 S ^ k , p , l + N / 2 - 1 S ^ k , p , l + N / 2 + 1 ]
    Figure US20030206577A1-20031106-M00004
  • Using these equations, the MF-MCCE ATRF [0059] 810 determines the filter tap weight vector that minimizes the cost function set for the ATRF. For example, where a minimum mean square error cost function is used, the ATRF 810 determines the weight vector according to the following equations.
  • J(w)=∥r l −w H B l2
  • w=(B l B l H)−1 B l r l H
  • which gives: [0060]
  • The MF-MCCE ATRF [0061] 810 applies this weight vector to the delayed and frequency shifted version of the signal received from the previous stage (or the antenna input if this is the first stage).
  • The SIC detection approach is particularly attractive where there is a wide range in received powers (e.g., due to lack of power control). The SIC approach exploits the power distribution by canceling based on signal strength ordering. For applications where signals are received at about the same power (e.g., through power control), the PIC approach is often preferable. [0062]
  • The combination of interference cancellation and ATRF channel estimation can also be extended to parallel interference cancellation techniques. FIG. 9 depicts one stage of a system [0063] 900 combining parallel interference cancellation (PIC) and adaptive minimum cost channel estimation (MCCE) according to a further specific illustrative embodiment of our invention. We shall refer to this system as a PIC-MCCE system. In the PIC-MCCE system 900, rather than detecting one additional user at each stage of the detector as in the SIC-MCCE system 200, every user is detected anew at each stage.
  • The PIC-MCCE system [0064] 900 includes a plurality of parallel processors 905. The number of processors can vary but is typically determined by the number of users associated with the system. Each processor is comprised of a conventional detector 206, a respread processor 208 and an ATRF 910. The conventional detector 206 in each parallel processor 905 is connected to a respread processor 208 and to a single external entity that communicates the received signal r(t) as input to the conventional detector. The ATRF 910 in each parallel processor 905 is connected between a respread processor 208 and a series 913 of mathematical operations processors 212. Alternatively, a partial summer circuit could be substituted for the series of mathematical operations processors. The series of mathematical operations processors 913 (or alternatively the partial summer circuit) is connected to the ATRF 210 in every parallel processor 905 and to the external entity providing the received signal.
  • The conventional detector [0065] 206 and the respread processor 208 are identical to the conventional detector 206 and respread processor 208 used in the SIC-MCCE embodiment. In addition, a control processor 902 could optionally be included to provide ordering of the signals prior to processing by the PIC-MCCE system.
  • FIG. 10 shows a flow diagram of the operation of each processor [0066] 905 of the embodiment of FIG. 9. After initial processing such as downconversion to baseband is performed on the received signal by an external entity, the received signal is sent in parallel to each of the processors 905 in the first stage of the PIC-MCCE system. The conventional detector 206 in each processor 905 determines the initial symbol decision estimate for the user assigned to that processor (step 1010). In each processor 905, the initial symbol estimate is communicated to the respread processor 208. The respread processor 208 generates a scaled estimate of the transmitted signal waveform for the user (step 1020). After respreading, each user is temporally reconstructed in the ATRF 910 (step 1030).
  • The outputs from the ATRF [0067] 910 in each processor are sent in parallel to the series of mathematical operations processors 913 (or alternatively to the partial summer). The mathematical operations processors 212 sum up all signals but one for each output, thus, forming an estimate of the interference for each user (step 1040). This interference estimate is then subtracted out of the received signal (step 1050). This process can be repeated for multiple PIC stages until the signal converges. At each stage, different numbers of users are successfully detected. Typically, as the number of stages increases, the number of users successfully detected increases, although oscillatory conditions can also occur. We define convergence as occurring at the stage after which no substantial increase is obtained in the number of successfully detected stages. The number of repetitions can be fixed or under dynamic control. Due to the computational complexity of repeating the PIC-MCCE stages, a preferred implementation defines the optimal number of repetitions.
  • A first approach to channel estimation in the PIC structure is the same as described above for basic SIC-MCCE channel estimation. A joint MCCE channel estimation approach, described above for the SIC-JMCCE system, can also be applied to the parallel structure. We refer to this system as PIC-JMCCE. [0068]
  • A partial PIC-JMCCE system is shown in FIG. 11A according to an illustrative embodiment of our invention. In this embodiment, each processor [0069] 905 of the PIC-JMCCE system has an individual ATRF 911. In a system with k users, each ATRF 911 receives k input signals, one from each of the respread processors 208 in the other parallel processors 905. Each ATRF 911 processes the signals as described above for step 544 of SIC-JMCCE processing.
  • An alternative embodiment of the PIC-JMCCE system is shown in FIG. 11B, having a single ATRF [0070] 912. In this embodiment, each processor 905 has a conventional detector 206 and a respread processor 208. The output of the respread processor 208 in every parallel processor 905 is communicated as input to the single ATRF 912. In the PIC-JMCCE receiver, since the channels are estimated simultaneously for all successfully detected signals, only a single ATRF module is needed at each state, however, this ATRF module produces channel estimates for all signals. After reconstruction, the ATRF outputs the signal interference associated with each user to the series of mathematical operations processors 913.
  • A third approach to channel estimation, PIC-MF-MCCE, extends the ATRF to account for Doppler spread. This approach is identical to the approach described above for SIC-MF-MCCE. In the PIC-MF-MCCE arrangement, a frequency shift processor [0071] 814 is connected between the respread processor 208 and the ATRF 810 in each parallel processor 905 of the system.
  • The above embodiment assumes that all signals are used in the PIC-MCCE system at each stage. This condition can be relaxed to include groups of signals at each stage. For example, a control processor could be used to order the received signals in groups of similar power and successively detect groups of users in parallel. Similarly, the PIC-JMCCE system need not include all previously detected signals at each stage, but possibly, some subset of them. [0072]
  • II. Application of STAP to Systems without a Pilot Reference Signal [0073]
  • Through the use of space time adaptive processing (STAP), a receiver is able to spatially separate user signals using array (smart antenna) receiver technology. This feature allows a STAP receiver to place spatial beam pattern nulls on strong interferers. In addition, the STAP receiver combines multipath energy, including both the resolvable multipath that is captured by a rake receiver, as well as unresolved multipath that the rake receiver cannot effectively exploit. [0074]
  • A single user space time adaptive processing (STAP) receiver is depicted in FIG. 12 in accordance with an illustrative embodiment of our invention. The STAP receiver [0075] 1200 includes a plurality of filters 1250, one per antenna, in a parallel arrangement, a mathematical summation processor 1270 for combining the outputs of all the filters prior to detection, a conventional detector 206, a respread processor 208, mathematical operations processor 212, and an MCCE weight update processor 64. The receiver in FIG. 12 also can include implementations with a one time tap per antenna (spatial adaptive signal processing) or with a single antenna element and multiple time taps (single element adaptive rake receiver). Each filter 1250 contains a tap delay line 1252, a series of STAP weights 1254, and a summation processor 1256. In a traditional STAP receiver, the STAP weights in the filter 1250 can be trained using a known pilot signal. However, a key complication in applying STAP to the IS-95 reverse link is that there is no pilot present in the received signal. Our invention provides innovative processes for blind adaptation where no pilot signal exists to train the filter weight.
  • An illustrative embodiment of our invention comprises a space time adaptive processing (STAP) processor, means for hypothesizing possible symbols transmitted during a symbol period, a respread processor, means for weight computation wherein the hypothesized symbol and the vector input symbol are used to form a set of STAP weights which filter the input data spatially and temporally, a matched filter bank, means for determining a metric to measure the quality of the matched filter bank, and means for comparing generated metrics. The STAP processor includes a plurality of filters, each comprising a set of STAP weights, and a plurality of mathematical summation circuits. In addition, each filter may also include a tapped delay line. In a preferred IS-95 implementation, the matched filter bank is a bank of 64 matched filters that correspond to the 64 possible Walsh symbols. [0076]
  • When a user signal is received by the antenna array, the user signal from each antenna in the array is first downconverted to baseband in a processor (not shown) and sampled. Downconversion and sampling are performed by an external processor. After the resulting signal r[0077] 1(t), r2(t), . . . rM(t) is received, a metric is determined associated with a hypothesized symbol value. The metric used may also be referred to as the sharpness factor. The step of determining a metric is repeated for each of the possible 64 Walsh symbols. The resulting 64 metrics are compared in the comparison means to determine the best estimate for the transmitted signal. This estimate is the output of the blind adaptive STAP detector.
  • A more detailed description of the metric determination step is described below. After the input signal vector is received, the hypothesizing means hypothesizes which symbol was transmitted. The hypothesized symbol is communicated to the respread processor and spread to create a replica of the transmitted waveform. The replica of the transmitted waveform and the input signal vector are input to the weight computation means. The weight computation means uses these inputs to determine the appropriate STAP weights for the STAP filters. After the determination is made, these STAP weights are communicated to the filters and applied to each signal vector component, r[0078] 1(t), r2(t), . . . rM(t). Before application of the STAP weights, a tapped delay line may be applied to each component of the input signal vector. After application of the STAP weights, the weighted signals from every antenna are combined in a mathematical summation circuit. The output of the summation circuit is despread and input into the matched filter bank. The matched filter bank generates a metric associated with the hypothesized symbol.
  • In an alternate embodiment, the STAP processor may despread the delayed signals from each antenna element and then apply the STAP weights. After the STAP weights are applied, the results are summed and used as input to the matched filter bank. [0079]
  • For example in IS-95, the sharpness factor is computed by taking the ratio of the peak output (i.e., for the most likely transmitted symbol) to the sum of the outputs for all the other 63 hypothesized Walsh symbols. The sharpness factor can also be based on the distance between the peak output and the average of all other outputs. In either case the STAP solution with the largest sharpness factor is chosen to determine the correctly hypothesized symbol. This embodiment can be extended across multiple symbols where we hypothesize all combinations of multiple symbols. [0080]
  • In an alternative embodiment, the STAP filter weights are determined based on a combination of “known” symbols and hypothesized symbols. The known symbols may be obtained by feeding back previously detected symbols, or from a priori known pilot reference symbols. Utilizing the known symbols allows extension of the length of the training sequence without requiring additional hypothesized symbols. It also anchors the hypothesized STAP solutions to a partially known training sequence, which makes it more likely that the correctly hypothesized solution will stand out. The above embodiments can be repeated for each symbol. These procedures can also be utilized to detect initial symbol(s), and then utilize an update procedure to compute the STAP weights for the remaining symbols. In other words, the STAP weights of the previous symbol can be used to detect the current symbol which can then in turn be used to update the STAP tap weights for the next symbol. [0081]
  • III. Combined STAP and MUD [0082]
  • The STAP receiver shown in FIG. 12 is limited in several ways. First, it can only effectively null M-1 high level signals (including temporally resolvable multipath components) where M is the number of antennas used. Therefore, it is only effective at extracting the M strongest signal components. Another embodiment of our invention combines MUD and temporal interference cancellation techniques and thus, removes much of the interfering signals before applying the STAP receiver. This approach frees up STAP degrees of freedom to operate on the remaining interference more effectively. [0083]
  • FIG. 13 depicts a single stage of a system [0084] 1300 combining STAP, interference cancellation MUD, and minimum cost channel estimation (MCCE) according to a specific illustrative embodiment of our invention. The illustrative embodiment of our invention shown in FIG. 13 applies SIC (e.g., SIC-MCCE or SIC-JMCCE) to each antenna element separately. We shall refer to this system as the STAP/VSIC system where the V refers to the vector nature of the cancellation process. The multi-stage STAP/VSIC receivers resemble the multi-stage SIC receivers of FIGS. 2, 4, and 5, except that the received signal and cleaned received signals are now vectors of size M.
  • A single stage of the STAP/VSIC system includes a STAP processor [0085] 1200, a plurality of ATRFs 1210, and a plurality of mathematical operations processors 212. The STAP processor can be a standard STAP processor or a blind adaptive STAP processor. In an illustrative embodiment of our invention, the STAP processor includes a plurality of filters 1250, a mathematical operations processor, and a conventional detector. In an alternate embodiment, the STAP processor may include a respread processor and may also include a MCCE weight update processor.
  • When a user signal is received by the antenna array, the user signal from each antenna in the array is first downconverted to baseband in a processor (not shown) and sampled. For each antenna, the resulting signal, r[0086] 1(t), r2(t), . . . rM(t), is communicated to the STAP processor 1200. After processing by the STAP filters, conventional detector, and respread processor as described in the embodiments above, the output of the respread processor, a vector estimate of the transmitted signal for the user, is communicated to the ATRFs 1210, one per antenna. Each ATRF 1210 then estimates the channel associated with the signal and reconstructs the signal interference. The methods used for channel estimation in the STAP/VSIC system can be either basic MCCE, JMCCE, or MF-MCCE techniques. Each reconstructed signal is then cancelled from the total received input for that antenna in a mathematical processor 212. The output of the plurality of mathematical processors, one per antenna, is then used as the vector input to the next STAP/VSIC stage.
  • The STAP/VSIC system approach can also be extended to vectorized parallel interference cancellation. We shall refer to this system as the STAP/VPIC system. In these embodiments, the system would take the form of the PIC detector shown in FIG. 9 with the conventional detector replaced by the one of the above described embodiments of a STAP processor. [0087]
  • Another embodiment of our invention combines STAP with interference cancellation techniques. In this embodiment, the system jointly solves for the ATRF tap weights and STAP tap weights. For example, the system minimizes the error associated with the cost function between the transmitted symbol replica and the sum of the STAP filter outputs and ATRF filter outputs. FIG. 14 depicts one illustrative embodiment of our invention. We shall refer to this system as the J-STAPSIC system. [0088]
  • The illustrative system of FIG. 14 comprises a plurality of J-STAPSIC processors arranged in successive stages [0089] 1404. The input to the J-STAPSIC system 1400 is a vector of size M where M is equivalent to one received signal stream for each antenna element). Each stage utilizes the symbols of all previously detected users, and detects one additional user's symbols. The number of stages, K, is equivalent to the total number of users associated with the system.
  • An illustrative embodiment of a k[0090] th J-STAPSIC stage 1404 is shown in FIG. 15. Each J-STAPSIC stage comprises a plurality of STAP filters 1252, one per antenna, in a parallel arrangement, a plurality of respread processors, one per previous stage, in a parallel arrangement for receiving the symbol estimates from the previous J-STAPSIC stages, a plurality of ATRF filters 1410, one per previous stage, a mathematical summation circuit 1414 for summing the outputs of the plurality of STAP filters, a mathematical summation circuit 1414 for summing the outputs of the plurality of ATRF filters, a mathematical operations processor 212 for adding the outputs of the mathematical summation circuits 1414, a conventional detector 206, and a respread processor 208.
  • In the k[0091] th stage, the plurality of STAP filters 1252 receive a cleaned vector received signal, r1(t), r2(t), . . . rM(t) from the previous stage and the plurality of parallel respread processors receive a vector comprising symbol estimates determined in the previous stage. In each parallel respread processor, the symbol estimates are spread. The mathematical summation circuit 1414 sums the outputs from the plurality of the STAP filters and another mathematical summation circuit sums the outputs from the plurality of ATRF filters. The outputs of these summation circuits are then combined in a mathematical operations circuit 212. Using the output of the mathematical operations circuit 212, the conventional detector despreads the input and estimates the symbol transmitted. The symbol estimate is then spread by the respread processor. The output of the respread processor is combined with the output of the conventional detector and is used as input to an MCCE weight update processor. The MCCE weight update processor then updates in parallel the tap weights of the plurality of STAP and ATRF filters.
  • Although the invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that various changes, omissions and additions may be therein and thereto, without departing from the spirit and the scope of the invention. [0092]

Claims (75)

    What is claimed is:
  1. 1. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference, said combination comprising:
    a control processor comprising a means for ordering user signals; and
    a plurality of SIC-ATRF processors combining successive interface cancellation (SIC) multi-user detection and adaptive temporal reconstruction filtering in a successive arrangement wherein the output of one of the said processors is the input to the next successive processor, each of said SIC-ATRF processors comprising:
    a conventional detector;
    a respread processor;
    an adaptive temporal filter (ATRF); and
    a complex mathematical operation processor for canceling the reconstructed signal for the user from the total received signal.
  2. 2. The combination of claim 1 wherein each conventional detector is an IS-95 conventional detector comprising a short code despreader, a long code despreader, and a 64-ary matched filter bank.
  3. 3. The combination of claim 1 wherein each conventional detector is an IS-95 rake conventional detector.
  4. 4. The combination of claim 1 wherein each ATRF comprises:
    tap weights;
    a tap delay line; and
    a mathematical summing circuit.
  5. 5. The combination of claim 4 wherein each SIC-ATRF processor further comprises a minimum cost channel estimate (MCCE) weight update processor.
  6. 6. The combination of claim 4 wherein each ATRF further comprises a minimum cost channel estimate weight update processor.
  7. 7. The combination of claim 4 wherein each ATRF is a minimum mean square error filter.
  8. 8. The combination of claim 1 wherein the output of each respread processor is the input for the ATRF.
  9. 9. The combination of claim 8 wherein the input to each ATRF further comprises the outputs of the respread processors in all the previous SIC-ATRF processors.
  10. 10. The combination of claim 1 wherein each SIC-ATRF processor further comprises a frequency shift processor connected between the respread processor and the adaptive temporal filter.
  11. 11. The combination of claim 10 wherein each frequency shift processor comprises means to shift the frequency of the signal output from the respread processor to take into account Doppler spread.
  12. 12. A method in a combination system for enabling the receiver to receive input signals at varied power levels in the presence of interference wherein said combination comprises a control processor and a plurality of SIC-ATRF processors in a successive arrangement, said method comprising:
    ordering user signals according to a pre-defined methodology and assigning each user signal to one of the SIC-ATRF processors wherein each SIC-ATRF processor comprises a conventional detector, a respread processor, an adaptive temporal filter; and a complex mathematical operation processor for canceling the reconstructed signal for the user from the total received signal;
    communicating a separate user code associated with the user signal to each SIC-ATRF processor according to the ordering;
    in each successive SIC-ATRF processor, performing the steps of:
    despreading, in the conventional detector, the received signal and estimating a symbol transmitted for the desired user signal;
    communicating the symbol estimate to the respread processor;
    spreading, in the respread processor, the symbol estimate;
    estimating a channel for the user associated with the SIC-ATRF processor and reconstructing the signal interference associated with the user signal; and
    canceling, in a mathematical operations processor, the reconstructed signal for the user associated with the SIC-ATRF processor from the total received signal.
    if a plurality of SIC-ATRF processors remain, inputting the output of the current SIC-ATRF processor to the next successive SIC-ATRF processor.
  13. 13. The method of claim 12 wherein the step of ordering user signals according to a pre-defined methodology comprises ranking signals in descending order of received powers.
  14. 14. The method of claim 12 wherein the step of ordering user signals according to a pre-defined methodology comprises identifying signals above a certain threshold.
  15. 15. The method of claim 12 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights that minimize a pre-determined cost function between the received signal and an output of the adaptive filter; and
    updating, in the ATRF, the filter tap weights.
  16. 16. The method of claim 15 wherein the pre-determined cost function is a minimum mean square error function.
  17. 17. The method of claim 12 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights by jointly minimizing the cost function between the received signal and the sum of the outputs of the respread processors of previous SIC-ATRF processors; and
    updating, in the ATRF, the filter tap weights.
  18. 18. The method of claim 17 wherein the pre-determined cost function is a minimum mean square error function.
  19. 19. A method in a combination system for enabling the receiver to receive input signals at varied power levels in the presence of interference wherein said combination comprises a control processor and a plurality of SIC-ATRF processors in a successive arrangement, said method comprising:
    ordering user signals according to a pre-defined methodology and assigning each user signal to one of the SIC-ATRF processors wherein each SIC-ATRF processor comprises a conventional detector, a respread processor, a frequency shift processor, an adaptive temporal filter; and a complex mathematical operation processor for canceling the reconstructed signal for the user from the total received signal.;
    communicating a separate user code associated with the user signal to each SIC-ATRF processor according to the ordering;
    in each successive SIC-ATRF processor, performing the steps of:
    despreading, in the conventional detector, the received signal and estimating a symbol transmitted for the desired user signal;
    communicating the symbol estimate to the respread processor;
    spreading, in the respread processor, the symbol estimate;
    shifting, in the frequency shift processor, the symbol estimate generated by the respread processor for the user associated with the SIC-ATRF processor;
    estimating a channel for the user associated with the SIC-ATRF processor and reconstructing the signal interference associated with the user signal; and
    canceling, in a mathematical operations processor, the reconstructed signal for the user associated with the SIC-ATRF processor from the total received signal.
    If a plurality of SIC-ATRF processors remain, inputting the output of the current SIC-ATRF processor to the next successive SIC-ATRF processor.
  20. 20. The method of claim 19 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights that minimize a pre-determined cost function between the received signal and an output of the adaptive filter; and
    updating, in the ATRF, the filter tap weights.
  21. 21. The method of claim 19 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights by jointly minimizing the cost function between the received frequency shift estimate and the sum of the outputs of the frequency shift processors of previous SIC-ATRF processors; and
    updating, in the ATRF, the filter tap weights.
  22. 22. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference, said combination comprising:
    a plurality of processors in a parallel arrangement wherein the input to every processor is a received signal, each of said parallel processors comprising:
    a conventional detector;
    a respread processor; and
    an adaptive temporal filter (ATRF); and
    means for summing signals to form an interference estimate and subtracting the estimate from the received signal.
  23. 23. The combination of claim 22 further comprising a control processor including a means for ordering user signals.
  24. 24. The combination of claim 22 wherein the summation and subtraction means is a series of mathematical operations processors.
  25. 25. The system of claim 22 wherein the summation and subtraction means is a partial summer circuit.
  26. 26. The combination of claim 22 wherein each ATRF comprises:
    tap weights;
    a tap delay line; and
    a mathematical summing circuit.
  27. 27. The combination of claim 26 wherein each parallel processor further comprises an MCCE weight update processor.
  28. 28. The combination of claim 26 wherein each ATRF further comprises a minimum cost channel estimate weight update processor.
  29. 29. The combination of claim 22 wherein, in each parallel processor, the output of the respread processor is the input for the ATRF.
  30. 30. The combination of claim 22 wherein, in each parallel processor, the input to the ATRF comprises the outputs of the respread processors in all the other parallel processors.
  31. 31. The combination of claim 22 wherein each parallel processor further comprises a frequency shift processor connected between the respread processor and the ATRF.
  32. 32. The combination of claim 31 wherein each frequency shift processor comprises means to shift the frequency of the signal output from the respread processor to take into account doppler spread.
  33. 33. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference, said combination comprising:
    a plurality of processors in a parallel arrangement wherein the input to every processor is a received signal, each of said parallel processors comprising:
    a conventional detector; and
    a respread processor;
    an adaptive temporal filter (ATRF); and
    means for summing signals to form an interference estimate and subtracting the estimate from the received signal.
  34. 34. The combination of claim 33 wherein the input to each ATRF comprises the outputs of the respread processors in all the parallel processors.
  35. 35. The combination of claim 33 wherein the ATRF further comprises a MCCE weight update processor.
  36. 36. The combination of claim 35 wherein each parallel processor further comprises a frequency shift processor connected between the respread processor in the parallel processor and the ATRF.
  37. 37. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein said combination comprises a plurality of parallel processors and means for summing signals to form an interference estimate and subtracting the estimate from the received signal:
    communicating a received signal to the plurality of parallel processors wherein each of the processors comprises a conventional detector, a respread processor, and an adaptive temporal filter (ATRF);
    generating a reconstructed signal in each of the parallel processors for a user associated with the parallel processor; said generation step further comprising:
    despreading, in the conventional detector, the received signal and estimating a symbol transmitted for the desired user signal;
    communicating the symbol estimate to the respread processor;
    spreading, in the respread processor, the symbol estimate; and
    estimating a channel for the signal associated with the parallel processor and reconstructing the signal interference;
    communicating the output of each parallel processor to a means for mathematically summing signals and subtracting signal estimates from the received signal;
    generating, in the mathematical means, an interference estimate for each user; and
    subtracting, in the mathematical means, the interference estimate from the received signal.
  38. 38. The method of claim 37 further comprising the steps of:
    ordering user signals according to a pre-defined methodology; and
    communicating a separate user code to a conventional detector in each parallel processor.
  39. 39. The method of claim 37 wherein the step of channel estimation step further comprises:
    determining the adaptive filter tap weights that minimize a pre-determined cost function between the received signal and an output of the adaptive filter; and
    updating, in the ATRF, the filter tap weights.
  40. 40. The method of claim 37 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights by jointly minimizing the cost function between the received signal and the sum of the outputs of the respread processors of all the other parallel processors; and
    updating, in the ATRF, the filter tap weights.
  41. 41. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein said combination comprises a plurality of parallel processors, an adaptive temporal filter (ATRF), and means for summing signals to form an interference estimate and subtracting the estimate from the received signal, the method comprising the steps of:
    communicating a received signal to the plurality of parallel processors wherein each of the processors comprises a conventional detector and a respread processor;
    generating a reconstructed signal in each of the parallel processors for a user associated with the parallel processor; said generation step further comprising:
    despreading, in the conventional detector, the received signal and estimating a symbol transmitted for the desired user signal;
    communicating the symbol estimate to the respread processor; and
    spreading, in the respread processor, the symbol estimate;
    estimating a channel for the signal associated with each parallel processor and reconstructing the signal interference;
    communicating the output of the ATRF to a means for mathematically summing signals and subtracting signal estimates from the received signal;
    generating, in the mathematical means, an interference estimate for each user; and
    subtracting, in the mathematical means, the interference estimate from the received signal.
  42. 42. The method of claim 41 wherein the step of channel estimation step further comprises:
    determining the adaptive filter tap weights that minimize a pre-determined cost function between the received signal and an output of the adaptive filter; and
    updating, in the ATRF, the filter tap weights.
  43. 43. The method of claim 41 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights by jointly minimizing the cost function between the received signal and the sum of the outputs of the respread processors of all the other parallel processors; and
    updating, in the ATRF, the filter tap weights.
  44. 44. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein said combination comprises a plurality of parallel processors and means for summing signals to form an interference estimate and subtracting the estimate from the received signal, the method comprising the steps of:
    communicating a received signal to the plurality of parallel processors wherein each of the processors comprises a conventional detector, a respread processor, a frequency shift processor and an adaptive temporal filter (ATRF);
    generating a reconstructed signal in each of the parallel processors for a user associated with the parallel processor; said generation step further comprising:
    despreading, in the conventional detector, the received signal and estimating a symbol transmitted for the desired user signal;
    communicating the symbol estimate to the respread processor;
    spreading, in the respread processor, the symbol estimate;
    shifting, in the frequency shift processor, the symbol estimate generated by the respread processor for the user association with the parallel processor; and
    estimating a channel for the signal associated with the parallel processor and reconstructing the signal interference;
    communicating the output of each parallel processor to a means for mathematically summing signals and subtracting signal estimates from the received signal;
    generating, in the mathematical means, an interference estimate for each user; and
    subtracting, in the mathematical means, the interference estimate from the received signal.
  45. 45. The method of claim 44 wherein the step of channel estimation step further comprises:
    determining the adaptive filter tap weights that minimize a pre-determined cost function between the received signal and an output of the adaptive filter; and
    updating, in the ATRF, the filter tap weights.
  46. 46. The method of claim 44 wherein the channel estimation step further comprises:
    determining the adaptive filter tap weights by jointly minimizing the cost function between the received signal and the sum of the outputs of the respread processors of all the other parallel processors; and
    updating, in the ATRF, the filter tap weights.
  47. 47. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference wherein said input signal is a vector comprised of one signal from each antenna in an antenna array of the receiver, said combination comprising:
    a space-time adaptive processing (STAP) processor;
    means for hypothesizing possible symbols transmitted during a symbol period;
    a respread processor;
    means for weight computation wherein the hypothesized symbol and the vector input symbol are used to form a set of STAP weights which filter the input data spatially and temporally;
    a matched filter bank;
    means for determining a metric to measure the quality of the matched filter bank; and
    means for comparing generated metrics.
  48. 48. The combination of claim 47 wherein the STAP processor comprises a plurality of tapped delay lines, one per antenna element.
  49. 49. The combination of claim 47 wherein the possible symbols transmitted are the 64 Walsh symbols for an IS-95 reverse link transmitter.
  50. 50. The combination of claim 49 wherein the matched filter bank is a bank of 64 matched filters corresponding to the 64 Walsh symbols.
  51. 51. The combination of claim 47 wherein the means for weight computation further comprises a means for using previously detected or known symbols.
  52. 52. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein said input signal is a vector comprised of one signal from each antenna in an antenna array of the receiver; the method comprising the steps of:
    receiving the input signal vector;
    determining a metric, said determining step comprising:
    hypothesizing which symbol was transmitted;
    respreading the hypothesized symbol;
    determining STAP weight update based on respread hypothesized symbol and input signal vector;
    applying a tap delay line to each signal vector component;
    applying STAP weights to each signal vector component, one per antenna;
    summing the weighted results in a mathematical summation circuit;
    despreading the output of the summation circuit and inputting the despread signal to a matched filter bank; and
    generating a metric associated with the hypothesized signal;
    repeating the metric determining step for each of the possible 64 Walsh symbols;
    comparing each of the 64 metrics; and
    determining, based on the comparison, the transmitted symbol.
  53. 53. A method in a combination system for enabling a receiver to receive input signals at varied power levels in the presence of interference wherein said input signal is a vector comprised of one signal from each antenna in an antenna array of the receiver; the method comprising the steps of:
    receiving the input signal vector;
    determining a metric, said determining step comprising:
    hypothesizing which symbol was transmitted;
    respreading the hypothesized symbol;
    determining STAP weight update based on respread hypothesized symbol and input signal vector;
    despreading the delayed signal vector components, one per antenna;
    applying the STAP weights to each of the despread signal vector components;
    summing the weighted results in a mathematical summation circuit; and
    generating a metric associated with the hypothesized signal;
    repeating the metric determining step for each of the possible 64 Walsh symbols;
    comparing each of the 64 metrics; and
    determining, based on the comparison, the transmitted symbol.
  54. 54. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference wherein said input signal is a vector comprised of one signal from each antenna in an antenna array of the receiver, said combination comprising:
    a control processor comprising a means for ordering user signals; and
    a plurality of STAP/VSIC-ATRF processors combining successive interface cancellation (SIC) multi-user detection, space-time adaptive processing and adaptive temporal reconstruction filtering in a successive arrangement wherein the output of one of the said processors is the vector input to the next successive processor, each of said STAP/VSIC-ATRF processors comprising:
    a space-time adaptive processing (STAP) processor;
    a plurality of adaptive temporal filters (ATRFs), one per antenna; and
    a plurality of complex mathematical operation processors, one per ATRF, for canceling the reconstructed signal for the user from the total received signal.
  55. 55. The combination of claim 54 wherein each STAP processor comprises:
    a plurality of filters, one per antenna;
    a mathematical summation processor for combining the outputs of all the filters;
    a conventional detector; and
    a minimum cost channel weight update processor.
  56. 56. The combination of claim 55 wherein the STAP processor is a blind adaptive STAP processor.
  57. 57. The combination of claim 55 wherein each STAP/VSIC-ATRF processor further comprises a plurality of respread processors.
  58. 58. The combination of claim 55 wherein each STAP processor further comprises a respread processor.
  59. 59. The combination of claim 54 wherein each ATRF comprises:
    tap weights;
    a tap delay line; and
    a mathematical summing circuit.
  60. 60. The combination of claim 59 wherein each ATRF further comprises a minimum cost channel estimate weight update processor.
  61. 61. The combination of claim 57 wherein, in each STAP/VSIC-ATRF processor, the output of the respread processor is the input for the plurality of ATRFs.
  62. 62. The combination of claim 57 wherein, in each STAP/VSIC-ATRF processor, the input to the plurality of ATRFs further comprises the outputs of the respread processors in all the previous STAP/VSIC-ATRF processors.
  63. 63. The combination of claim 57 wherein each STAP/VSIC-ATRF processor further comprises a plurality of frequency shift processors connected between the respread processor and the plurality of ATRFs.
  64. 64. In a wireless receiver for a CDMA system, a combination for enabling the receiver to receive input signals at varied power levels in the presence of interference, said combination comprising:
    a plurality of processors in a parallel arrangement wherein the input to every processor is a received signal, each of said parallel processors comprising:
    a space-time adaptive processing (STAP) processor; and
    a plurality of adaptive temporal filters (ATRFs); and
    means for summing signals to form an interference estimate and subtracting the estimate from the received signal.
  65. 65. The combination of claim 64 wherein each STAP processor comprises:
    a plurality of filters, one per antenna;
    a mathematical summation processor for combining the outputs of all the filters; and
    a conventional detector.
  66. 66. The combination of claim 64 wherein each parallel processor further comprises an MCCE weight update processor.
  67. 67. The combination of claim 65 wherein each STAP processor further comprises an MCCE weight update processor.
  68. 68. The combination of claim 64 wherein each parallel processor further comprises a of respread processor.
  69. 69. The combination of claim 65 wherein each STAP processor further comprises a respread processor.
  70. 70. The combination of claim 64 wherein the summation and subtraction means is a series of mathematical operations processors.
  71. 71. The combination of claim 64 wherein the summation and subtraction means is a series of mathematical operations processors.
  72. 72. The combination of claim 64 wherein each ATRF comprises:
    tap weights;
    a tap delay line; and
    a mathematical summing circuit.
  73. 73. The combination of claim 68 wherein, in each parallel processor, the output of the respread processor is the input for the plurality of ATRFs.
  74. 74. The combination of claim 68 wherein, in each parallel processor, the input to the plurality of ATRFs further comprises the outputs of the respread processors in all the other parallel processors.
  75. 75. The combination of claim 68 wherein each parallel processor further comprises a plurality of frequency shift processors connected between the respread processor and the plurality of ATRFs.
US09813491 2000-03-21 2001-03-21 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems Abandoned US20030206577A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US19080300 true 2000-03-21 2000-03-21
US09813491 US20030206577A1 (en) 2000-03-21 2001-03-21 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US09813491 US20030206577A1 (en) 2000-03-21 2001-03-21 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US10971237 US8111669B2 (en) 2000-03-21 2005-01-27 Parallel interference cancellation and minimum cost channel estimation
US10971233 US7688777B2 (en) 2000-03-21 2005-01-31 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US13365757 US8670418B2 (en) 2000-03-21 2012-02-03 Successive interference cancellation

Related Child Applications (2)

Application Number Title Priority Date Filing Date
US10971237 Division US8111669B2 (en) 2000-03-21 2005-01-27 Parallel interference cancellation and minimum cost channel estimation
US10971233 Division US7688777B2 (en) 2000-03-21 2005-01-31 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems

Publications (1)

Publication Number Publication Date
US20030206577A1 true true US20030206577A1 (en) 2003-11-06

Family

ID=22702845

Family Applications (4)

Application Number Title Priority Date Filing Date
US09813491 Abandoned US20030206577A1 (en) 2000-03-21 2001-03-21 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US10971237 Active 2026-12-24 US8111669B2 (en) 2000-03-21 2005-01-27 Parallel interference cancellation and minimum cost channel estimation
US10971233 Active 2024-06-13 US7688777B2 (en) 2000-03-21 2005-01-31 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US13365757 Active 2021-05-07 US8670418B2 (en) 2000-03-21 2012-02-03 Successive interference cancellation

Family Applications After (3)

Application Number Title Priority Date Filing Date
US10971237 Active 2026-12-24 US8111669B2 (en) 2000-03-21 2005-01-27 Parallel interference cancellation and minimum cost channel estimation
US10971233 Active 2024-06-13 US7688777B2 (en) 2000-03-21 2005-01-31 Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US13365757 Active 2021-05-07 US8670418B2 (en) 2000-03-21 2012-02-03 Successive interference cancellation

Country Status (2)

Country Link
US (4) US20030206577A1 (en)
WO (1) WO2001071927A3 (en)

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030002569A1 (en) * 2001-03-14 2003-01-02 Oates John H. Wireless communication systems and methods for long-code communications for regenerative multiple user detection involving implicit waveform subtraction
US20030016772A1 (en) * 2001-04-02 2003-01-23 Per Ekstrand Aliasing reduction using complex-exponential modulated filterbanks
US20030048800A1 (en) * 2001-03-30 2003-03-13 Daniel B. Kilfoyle Mutlistage reception of code division multiple access transmissions
US20030076872A1 (en) * 2001-08-21 2003-04-24 Jalloul Louay M. A. Method and apparatus for enhancing data rates in spread spectrum communication systems
US20030231702A1 (en) * 2001-03-14 2003-12-18 Oates John H. Wireless communications systems and methods for cache enabled multiple processor based multiple user detection
US20040023691A1 (en) * 2002-08-01 2004-02-05 Interdigital Technology Corporation Simple smart-antenna system for MUD-enabled cellular networks
US20040123227A1 (en) * 2002-12-24 2004-06-24 Lee Sang-Hyun Hybrid multi-user interference cancellation method and device using clustering algorithm based on dynamic programming
US20050175074A1 (en) * 2004-02-11 2005-08-11 Interdigital Technology Corporation Wireless communication method and apparatus for performing multi-user detection using reduced length channel impulse responses
US20050195889A1 (en) * 2004-03-05 2005-09-08 Grant Stephen J. Successive interference cancellation in a generalized RAKE receiver architecture
US20060077927A1 (en) * 2001-09-17 2006-04-13 Kilfoyle Daniel B Method and system for a channel selective repeater with capacity enhancement in a spread-spectrum wireless network
US20060109938A1 (en) * 2004-11-19 2006-05-25 Raghu Challa Interference suppression with virtual antennas
US7535867B1 (en) 2001-02-02 2009-05-19 Science Applications International Corporation Method and system for a remote downlink transmitter for increasing the capacity and downlink capability of a multiple access interference limited spread-spectrum wireless network
FR2927748A1 (en) * 2008-02-19 2009-08-21 Thales Sa Method of processing a first and a second signal superposed in a composite signal incident and corresponding device
US7602835B1 (en) * 2004-08-10 2009-10-13 L-3 Communications Corporation Multi-rate spread spectrum composite code
FR2930389A1 (en) * 2008-04-22 2009-10-23 Thales Sa Method for processing a first and a second signal superposed in a composite signal incident and corresponding device.
US7724851B2 (en) * 2004-03-04 2010-05-25 Bae Systems Information And Electronic Systems Integration Inc. Receiver with multiple collectors in a multiple user detection system
US20110244899A1 (en) * 2010-03-31 2011-10-06 Qualcomm Incorporated Methods and apparatus for determining a communications mode and/or using a determined communications mode
JP2012100026A (en) * 2010-11-01 2012-05-24 Ntt Docomo Inc Radio communication device and radio communication method
US8412104B2 (en) 2010-11-16 2013-04-02 Samsung Electronics Co., Ltd. Method and apparatus of controlling inter cell interference based on cooperation of intra cell terminals
US8710836B2 (en) 2008-12-10 2014-04-29 Nanomr, Inc. NMR, instrumentation, and flow meter/controller continuously detecting MR signals, from continuously flowing sample material
US8841104B2 (en) 2010-04-21 2014-09-23 Nanomr, Inc. Methods for isolating a target analyte from a heterogeneous sample
US20160036490A1 (en) * 2014-08-01 2016-02-04 Futurewei Technologies, Inc. Interference Cancellation in Coaxial Cable Connected Data Over Cable Service Interface Specification (DOCSIS) System or Cable Network
US20160142236A1 (en) * 2013-06-25 2016-05-19 Thuy Duong NGUYEN Weak signal detection in double transmission
US9389225B2 (en) 2010-04-21 2016-07-12 Dna Electronics, Inc. Separating target analytes using alternating magnetic fields
US9428547B2 (en) 2010-04-21 2016-08-30 Dna Electronics, Inc. Compositions for isolating a target analyte from a heterogeneous sample
US9476812B2 (en) 2010-04-21 2016-10-25 Dna Electronics, Inc. Methods for isolating a target analyte from a heterogeneous sample
US9551704B2 (en) 2012-12-19 2017-01-24 Dna Electronics, Inc. Target detection
US9599610B2 (en) 2012-12-19 2017-03-21 Dnae Group Holdings Limited Target capture system
US9804069B2 (en) 2012-12-19 2017-10-31 Dnae Group Holdings Limited Methods for degrading nucleic acid
US9902949B2 (en) 2012-12-19 2018-02-27 Dnae Group Holdings Limited Methods for universal target capture
US9995742B2 (en) 2012-12-19 2018-06-12 Dnae Group Holdings Limited Sample entry
US10000557B2 (en) 2012-12-19 2018-06-19 Dnae Group Holdings Limited Methods for raising antibodies

Families Citing this family (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6184829B1 (en) 1999-01-08 2001-02-06 Trueposition, Inc. Calibration for wireless location system
US6765531B2 (en) 1999-01-08 2004-07-20 Trueposition, Inc. System and method for interference cancellation in a location calculation, for use in a wireless location system
US7783299B2 (en) 1999-01-08 2010-08-24 Trueposition, Inc. Advanced triggers for location-based service applications in a wireless location system
US20030206577A1 (en) 2000-03-21 2003-11-06 Liberti Joseph Charles Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US6711219B2 (en) * 2000-12-04 2004-03-23 Tensorcomm, Incorporated Interference cancellation in a signal
WO2005091889A3 (en) * 2004-03-05 2007-03-29 Thorkild Hansen Method and apparatus for improving the efficiency and accuracy of rfid systems
WO2005091890A3 (en) * 2004-03-05 2006-10-05 Thorkild Hansen Method and apparatus for security in a wireless network
US7536158B2 (en) 2004-03-29 2009-05-19 Telefonaktiebolaget Lm Ericsson (Publ) Impairment correlation estimation in a spread spectrum system
US8111789B2 (en) 2004-10-06 2012-02-07 Broadcom Corporation Method and system for channel estimation in a single channel MIMO system with multiple RF chains for WCDMA/HSDPA
US8098776B2 (en) 2004-10-06 2012-01-17 Broadcom Corporation Method and system for pre-equalization in a single weight spatial multiplexing MIMO system
CN101980456A (en) * 2005-01-05 2011-02-23 Atc科技有限责任公司 Adaptive beam forming with multi-user detection and interference reduction in satellite communiation systems and methods
FR2887379B1 (en) * 2005-06-17 2007-08-31 Thales Sa Process for blind demodulation to higher order more issuers of linear waveform
US8855704B2 (en) 2005-08-26 2014-10-07 Qualcomm Incorporated Fast cell selection in TD-CDMA (UMTS TDD)
US8130727B2 (en) * 2005-10-27 2012-03-06 Qualcomm Incorporated Quasi-orthogonal allocation of codes in TD-CDMA systems
US8068464B2 (en) 2005-10-27 2011-11-29 Qualcomm Incorporated Varying scrambling/OVSF codes within a TD-CDMA slot to overcome jamming effect by a dominant interferer
WO2007126446A3 (en) 2006-01-12 2008-04-17 Agere Systems Inc Receiver employing non-pilot reference channels for equalizing a received signal
US7924930B1 (en) * 2006-02-15 2011-04-12 Marvell International Ltd. Robust synchronization and detection mechanisms for OFDM WLAN systems
US8275323B1 (en) 2006-07-14 2012-09-25 Marvell International Ltd. Clear-channel assessment in 40 MHz wireless receivers
US20080069197A1 (en) * 2006-09-20 2008-03-20 Agere Systems Inc. Equalizer for equalizing multiple received versions of a signal
US8737451B2 (en) * 2007-03-09 2014-05-27 Qualcomm Incorporated MMSE MUD in 1x mobiles
US8521089B2 (en) * 2008-03-31 2013-08-27 Intel Corporation Reducing co-channel interference
EP2134017B1 (en) * 2008-05-09 2015-04-01 Vodafone Holding GmbH Method and system for data communication
EP2427868B1 (en) * 2009-05-07 2013-06-19 Koninklijke Philips Electronics N.V. System and method for generating a tomographic reconstruction filter
CA2693012C (en) * 2009-09-18 2015-06-23 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of National Defence Signal detection in fading environments
CN102611648B (en) * 2011-01-20 2015-04-01 中兴通讯股份有限公司 Successive interference cancellation system and method
US8767799B2 (en) 2011-04-12 2014-07-01 Alcatel Lucent Method and apparatus for determining signal-to-noise ratio
US9209858B2 (en) * 2011-04-12 2015-12-08 Alcatel Lucent Method and apparatus for determining uplink noise power in a wireless communication system
US8982849B1 (en) 2011-12-15 2015-03-17 Marvell International Ltd. Coexistence mechanism for 802.11AC compliant 80 MHz WLAN receivers
US9885772B1 (en) 2014-08-26 2018-02-06 Vencore Labs, Inc. Geolocating wireless emitters
US10051616B2 (en) * 2014-10-07 2018-08-14 Massachusetts Institute Of Technology Multiuser detection for high capacity cellular downlink
US9602240B1 (en) * 2015-09-11 2017-03-21 Signalchip Innovations Private Limited Method and system for symbol level interference cancellation at a receiver for multiuser detection

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5596600A (en) * 1995-04-06 1997-01-21 Mayflower Communications Company, Inc. Standalone canceller of narrow band interference for spread spectrum receivers
US5818882A (en) * 1995-01-31 1998-10-06 Nec Corporation Frequency offset cancellation apparatus
US6115409A (en) * 1999-06-21 2000-09-05 Envoy Networks, Inc. Integrated adaptive spatial-temporal system for controlling narrowband and wideband sources of interferences in spread spectrum CDMA receivers
US6137788A (en) * 1995-06-13 2000-10-24 Ntt Mobile Communications Network, Inc. CDMA demodulating apparatus

Family Cites Families (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0779281B2 (en) * 1990-09-21 1995-08-23 日本ビクター株式会社 Spread spectrum modulation demodulator
US5218619A (en) * 1990-12-17 1993-06-08 Ericsson Ge Mobile Communications Holding, Inc. CDMA subtractive demodulation
US5268927A (en) * 1992-10-06 1993-12-07 Mayflower Communications Company, Inc. Digital adaptive transversal filter for spread spectrum receivers
JP2734953B2 (en) * 1993-12-16 1998-04-02 日本電気株式会社 Cdma receiving device
KR0158092B1 (en) * 1994-02-10 1998-12-01 오오보시 고지 Adaptive spectrum spreading receiver
US5719899A (en) * 1994-02-25 1998-02-17 U.S. Philips Corporation Multiple access digital transmission system and a radio base station and a receiver for use in such a system
DE69526892D1 (en) * 1994-09-01 2002-07-11 Nec Corp Beam excitation with adaptive filters with limited coefficient for suppression of interference signals
JPH09116475A (en) * 1995-10-23 1997-05-02 Nec Corp Time diversity transmission/reception system
EP0931388B1 (en) 1996-08-29 2003-11-05 Cisco Technology, Inc. Spatio-temporal processing for communication
US6275543B1 (en) 1996-10-11 2001-08-14 Arraycomm, Inc. Method for reference signal generation in the presence of frequency offsets in a communications station with spatial processing
KR100204599B1 (en) * 1996-12-21 1999-06-15 정선종 Adaptive and mixed noise eliminating method
US6331837B1 (en) 1997-05-23 2001-12-18 Genghiscomm Llc Spatial interferometry multiplexing in wireless communications
US5872540A (en) * 1997-06-26 1999-02-16 Electro-Radiation Incorporated Digital interference suppression system for radio frequency interference cancellation
JPH11251959A (en) * 1998-03-05 1999-09-17 Fujitsu Ltd Interference canceler device and radio communication equipment
US6363103B1 (en) * 1998-04-09 2002-03-26 Lucent Technologies Inc. Multistage interference cancellation for CDMA applications using M-ary orthogonal moduation
US6301293B1 (en) 1998-08-04 2001-10-09 Agere Systems Guardian Corp. Detectors for CDMA systems
DE69832483T2 (en) * 1998-08-19 2006-06-08 Siemens Ag A spread spectrum receiver for reducing intersymbol interference
JP3800382B2 (en) * 1998-09-04 2006-07-26 富士通株式会社 Channel estimation method and interference canceller in the interference canceller
US6363104B1 (en) 1998-10-02 2002-03-26 Ericsson Inc. Method and apparatus for interference cancellation in a rake receiver
US6456647B1 (en) 1998-12-16 2002-09-24 Lsi Logic Corporation Two step signal recovery scheme for a receiver
JP3121319B2 (en) * 1998-12-17 2000-12-25 日本電気株式会社 Ds-cdma multiuser interference canceller and the system
US6700923B1 (en) * 1999-01-04 2004-03-02 Board Of Regents The University Of Texas System Adaptive multiple access interference suppression
US6721293B1 (en) 1999-03-10 2004-04-13 Nokia Corporation Unsupervised adaptive chip separation filter for CDMA terminal
US6782036B1 (en) * 1999-05-26 2004-08-24 Board Of Regents, The University Of Texas System Smart antenna multiuser detector
US6393073B1 (en) * 1999-06-28 2002-05-21 Raytheon Company Method of frequency offset estimation and correction for adaptive antennas
US6252540B1 (en) * 1999-12-21 2001-06-26 The United States Of America As Represented By The Secretary Of The Air Force Apparatus and method for two stage hybrid space-time adaptive processing in radar and communication systems
US6975666B2 (en) * 1999-12-23 2005-12-13 Institut National De La Recherche Scientifique Interference suppression in CDMA systems
US20030206577A1 (en) 2000-03-21 2003-11-06 Liberti Joseph Charles Combined adaptive spatio-temporal processing and multi-user detection for CDMA wireless systems
US6618433B1 (en) 2000-08-04 2003-09-09 Intel Corporation Family of linear multi-user detectors (MUDs)
US6768747B1 (en) 2000-11-30 2004-07-27 Arraycomm, Inc. Relative and absolute timing acquisition for a radio communications system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5818882A (en) * 1995-01-31 1998-10-06 Nec Corporation Frequency offset cancellation apparatus
US5596600A (en) * 1995-04-06 1997-01-21 Mayflower Communications Company, Inc. Standalone canceller of narrow band interference for spread spectrum receivers
US6137788A (en) * 1995-06-13 2000-10-24 Ntt Mobile Communications Network, Inc. CDMA demodulating apparatus
US6115409A (en) * 1999-06-21 2000-09-05 Envoy Networks, Inc. Integrated adaptive spatial-temporal system for controlling narrowband and wideband sources of interferences in spread spectrum CDMA receivers

Cited By (79)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7535867B1 (en) 2001-02-02 2009-05-19 Science Applications International Corporation Method and system for a remote downlink transmitter for increasing the capacity and downlink capability of a multiple access interference limited spread-spectrum wireless network
US7099374B2 (en) * 2001-03-14 2006-08-29 Mercury Computer Systems, Inc. Wireless communication systems and methods for long-code communications for regenerative multiple user detection involving matched-filter outputs
US7453922B2 (en) 2001-03-14 2008-11-18 Mercury Computer Systems, Inc. Wireless communication systems and methods for contiguously addressable memory enabled multiple processor based multiple user detection
US20030076875A1 (en) * 2001-03-14 2003-04-24 Oates John H. Hardware and software for performing computations in a short-code spread-spectrum communications system
US7327780B2 (en) 2001-03-14 2008-02-05 Mercury Computer Systems, Inc. Wireless communications systems and methods for multiple operating system multiple user detection
US20030091058A1 (en) * 2001-03-14 2003-05-15 Oates John H. Wireless communications systems and methods for virtual user based multiple user detection utilizing vector processor generated mapped cross-correlation matrices
US20030091102A1 (en) * 2001-03-14 2003-05-15 Oates John H. Computational methods for use in a short-code spread-spectrum communications system
US20030091106A1 (en) * 2001-03-14 2003-05-15 Oates John H. Load balancing computational methods in a short-code spread-spectrum communications system
US20030099225A1 (en) * 2001-03-14 2003-05-29 Oates John H. Wireless communication systems and methods for long-code communications for regenerative multiple user detection involving pre-maximal combination matched filter outputs
US20030099224A1 (en) * 2001-03-14 2003-05-29 Oates John H. Wireless communications systems and methods for short-code multiple user detection
US20030128739A1 (en) * 2001-03-14 2003-07-10 Oates John H. Wireless communications systems and methods for multiple operating system multiple user detection
US20030191887A1 (en) * 2001-03-14 2003-10-09 Oates John H. Wireless communications systems and methods for direct memory access and buffering of digital signals for multiple user detection
US20030198197A1 (en) * 2001-03-14 2003-10-23 Oates John H. Wireless communication systems and methods for contiguously addressable memory enabled multiple processor based multiple user detection
US20030202559A1 (en) * 2001-03-14 2003-10-30 Oates John H. Wireless communications systems and methods for nonvolatile storage of operating parameters for multiple processor based multiple user detection
US20030231702A1 (en) * 2001-03-14 2003-12-18 Oates John H. Wireless communications systems and methods for cache enabled multiple processor based multiple user detection
US7248623B2 (en) 2001-03-14 2007-07-24 Mercury Computer Systems, Inc. Wireless communications systems and methods for short-code multiple user detection
US7218668B2 (en) 2001-03-14 2007-05-15 Mercury Computer Systems, Inc. Wireless communications systems and methods for virtual user based multiple user detection utilizing vector processor generated mapped cross-correlation matrices
US7210062B2 (en) 2001-03-14 2007-04-24 Mercury Computer Systems, Inc. Wireless communications systems and methods for nonvolatile storage of operating parameters for multiple processor based multiple user detection
US7203221B2 (en) 2001-03-14 2007-04-10 Mercury Computer Systems, Inc. Load balancing computational methods in a short-code spread-spectrum communications system
US7177344B2 (en) 2001-03-14 2007-02-13 Mercury Computer Systems, Inc. Wireless communication systems and methods for long-code communications for regenerative multiple user detection involving implicit waveform subtraction
US7164706B2 (en) 2001-03-14 2007-01-16 Mercury Computer Systems, Inc. Computational methods for use in a short-code spread-spectrum communications system
US7139306B2 (en) 2001-03-14 2006-11-21 Mercury Computer Systems, Inc. Wireless communication systems and methods for long-code communications for regenerative multiple user detection involving pre-maximal combination matched filter outputs
US7110437B2 (en) 2001-03-14 2006-09-19 Mercury Computer Systems, Inc. Wireless communications systems and methods for direct memory access and buffering of digital signals for multiple user detection
US7110440B2 (en) 2001-03-14 2006-09-19 Mercury Computer Systems, Inc. Wireless communications systems and methods for multiple processor based multiple user detection
US20030002569A1 (en) * 2001-03-14 2003-01-02 Oates John H. Wireless communication systems and methods for long-code communications for regenerative multiple user detection involving implicit waveform subtraction
US7209515B2 (en) * 2001-03-30 2007-04-24 Science Applications International Corporation Multistage reception of code division multiple access transmissions
US20030048800A1 (en) * 2001-03-30 2003-03-13 Daniel B. Kilfoyle Mutlistage reception of code division multiple access transmissions
US7630344B1 (en) 2001-03-30 2009-12-08 Science Applications International Corporation Multistage reception of code division multiple access transmissions
US7242710B2 (en) * 2001-04-02 2007-07-10 Coding Technologies Ab Aliasing reduction using complex-exponential modulated filterbanks
US20030016772A1 (en) * 2001-04-02 2003-01-23 Per Ekstrand Aliasing reduction using complex-exponential modulated filterbanks
US20030076872A1 (en) * 2001-08-21 2003-04-24 Jalloul Louay M. A. Method and apparatus for enhancing data rates in spread spectrum communication systems
US7133433B2 (en) * 2001-08-21 2006-11-07 Infineon Technologies Ag Method and apparatus for enhancing data rates in spread spectrum communication systems
US20060077927A1 (en) * 2001-09-17 2006-04-13 Kilfoyle Daniel B Method and system for a channel selective repeater with capacity enhancement in a spread-spectrum wireless network
US7936711B2 (en) 2001-09-17 2011-05-03 Science Applications International Corporation Method and system for a channel selective repeater with capacity enhancement in a spread-spectrum wireless network
US20060083196A1 (en) * 2001-09-17 2006-04-20 Kilfoyle Daniel B Method and system for a channel selective repeater with capacity enhancement in a spread-spectrum wireless network
US20060077920A1 (en) * 2001-09-17 2006-04-13 Kilfoyle Daniel B Method and system for a channel selective repeater with capacity enhancement in a spread-spectrum wireless network
US7710913B2 (en) 2001-09-17 2010-05-04 Science Applications International Corporation Method and system for a channel selective repeater with capacity enhancement in a spread-spectrum wireless network
US20070049349A1 (en) * 2002-08-01 2007-03-01 Interdigital Technology Corporation Simple smart-antenna system for mud-enabled cellular networks
US20040023691A1 (en) * 2002-08-01 2004-02-05 Interdigital Technology Corporation Simple smart-antenna system for MUD-enabled cellular networks
WO2004013984A1 (en) * 2002-08-01 2004-02-12 Interdigital Technology Corporation Simple smart-antenna method and apparatus for mud-enabled cellular networks
US7130662B2 (en) * 2002-08-01 2006-10-31 Interdigital Technology Corporation Simple smart-antenna system for MUD-enabled cellular networks
US7260161B2 (en) * 2002-12-24 2007-08-21 Electronics And Telecommunications Research Institute Hybrid multi-user interference cancellation method and device using clustering algorithm based on dynamic programming
US20040123227A1 (en) * 2002-12-24 2004-06-24 Lee Sang-Hyun Hybrid multi-user interference cancellation method and device using clustering algorithm based on dynamic programming
US20050175074A1 (en) * 2004-02-11 2005-08-11 Interdigital Technology Corporation Wireless communication method and apparatus for performing multi-user detection using reduced length channel impulse responses
WO2005076831A2 (en) * 2004-02-11 2005-08-25 Interdigital Technology Corporation Wireless communication method and apparatus for performing multi-user detection using reduced length channel impulse responses
WO2005076831A3 (en) * 2004-02-11 2008-09-18 Aykut Bultan Wireless communication method and apparatus for performing multi-user detection using reduced length channel impulse responses
US7724851B2 (en) * 2004-03-04 2010-05-25 Bae Systems Information And Electronic Systems Integration Inc. Receiver with multiple collectors in a multiple user detection system
US7339980B2 (en) * 2004-03-05 2008-03-04 Telefonaktiebolaget Lm Ericsson (Publ) Successive interference cancellation in a generalized RAKE receiver architecture
US20050195889A1 (en) * 2004-03-05 2005-09-08 Grant Stephen J. Successive interference cancellation in a generalized RAKE receiver architecture
US7602835B1 (en) * 2004-08-10 2009-10-13 L-3 Communications Corporation Multi-rate spread spectrum composite code
US7801248B2 (en) * 2004-11-19 2010-09-21 Qualcomm Incorporated Interference suppression with virtual antennas
US20060109938A1 (en) * 2004-11-19 2006-05-25 Raghu Challa Interference suppression with virtual antennas
EP2093889A1 (en) * 2008-02-19 2009-08-26 Thales Method for processing a first and second signal superimposed within an incident aggregate signal and corresponding device.
FR2927748A1 (en) * 2008-02-19 2009-08-21 Thales Sa Method of processing a first and a second signal superposed in a composite signal incident and corresponding device
FR2930389A1 (en) * 2008-04-22 2009-10-23 Thales Sa Method for processing a first and a second signal superposed in a composite signal incident and corresponding device.
EP2120356A1 (en) * 2008-04-22 2009-11-18 Thales Method for processing a first and second signal superimposed within an aggregate signal and corresponding device.
US8710836B2 (en) 2008-12-10 2014-04-29 Nanomr, Inc. NMR, instrumentation, and flow meter/controller continuously detecting MR signals, from continuously flowing sample material
US8428629B2 (en) * 2010-03-31 2013-04-23 Qualcomm Incorporated Methods and apparatus for determining a communications mode and/or using a determined communications mode
US20110244899A1 (en) * 2010-03-31 2011-10-06 Qualcomm Incorporated Methods and apparatus for determining a communications mode and/or using a determined communications mode
US9476812B2 (en) 2010-04-21 2016-10-25 Dna Electronics, Inc. Methods for isolating a target analyte from a heterogeneous sample
US9869671B2 (en) 2010-04-21 2018-01-16 Dnae Group Holdings Limited Analyzing bacteria without culturing
US8841104B2 (en) 2010-04-21 2014-09-23 Nanomr, Inc. Methods for isolating a target analyte from a heterogeneous sample
US9696302B2 (en) 2010-04-21 2017-07-04 Dnae Group Holdings Limited Methods for isolating a target analyte from a heterogeneous sample
US9970931B2 (en) 2010-04-21 2018-05-15 Dnae Group Holdings Limited Methods for isolating a target analyte from a heterogenous sample
US9389225B2 (en) 2010-04-21 2016-07-12 Dna Electronics, Inc. Separating target analytes using alternating magnetic fields
US9428547B2 (en) 2010-04-21 2016-08-30 Dna Electronics, Inc. Compositions for isolating a target analyte from a heterogeneous sample
US9562896B2 (en) 2010-04-21 2017-02-07 Dnae Group Holdings Limited Extracting low concentrations of bacteria from a sample
US9671395B2 (en) 2010-04-21 2017-06-06 Dnae Group Holdings Limited Analyzing bacteria without culturing
JP2012100026A (en) * 2010-11-01 2012-05-24 Ntt Docomo Inc Radio communication device and radio communication method
US8412104B2 (en) 2010-11-16 2013-04-02 Samsung Electronics Co., Ltd. Method and apparatus of controlling inter cell interference based on cooperation of intra cell terminals
US9599610B2 (en) 2012-12-19 2017-03-21 Dnae Group Holdings Limited Target capture system
US9551704B2 (en) 2012-12-19 2017-01-24 Dna Electronics, Inc. Target detection
US9995742B2 (en) 2012-12-19 2018-06-12 Dnae Group Holdings Limited Sample entry
US9902949B2 (en) 2012-12-19 2018-02-27 Dnae Group Holdings Limited Methods for universal target capture
US10000557B2 (en) 2012-12-19 2018-06-19 Dnae Group Holdings Limited Methods for raising antibodies
US9804069B2 (en) 2012-12-19 2017-10-31 Dnae Group Holdings Limited Methods for degrading nucleic acid
US9825794B2 (en) * 2013-06-25 2017-11-21 Thuy Duong NGUYEN Weak signal detection in double transmission
US20160142236A1 (en) * 2013-06-25 2016-05-19 Thuy Duong NGUYEN Weak signal detection in double transmission
US20160036490A1 (en) * 2014-08-01 2016-02-04 Futurewei Technologies, Inc. Interference Cancellation in Coaxial Cable Connected Data Over Cable Service Interface Specification (DOCSIS) System or Cable Network

Also Published As

Publication number Publication date Type
US7688777B2 (en) 2010-03-30 grant
US8670418B2 (en) 2014-03-11 grant
US8111669B2 (en) 2012-02-07 grant
WO2001071927A2 (en) 2001-09-27 application
WO2001071927A3 (en) 2002-02-28 application
US20050111414A1 (en) 2005-05-26 application
US20120201279A1 (en) 2012-08-09 application
US20050128985A1 (en) 2005-06-16 application

Similar Documents

Publication Publication Date Title
Buehrer et al. A simulation comparison of multiuser receivers for cellular CDMA
US6088383A (en) Spread-spectrum signal demodulator
US6067292A (en) Pilot interference cancellation for a coherent wireless code division multiple access receiver
US6745050B1 (en) Multichannel multiuser detection
US6404760B1 (en) CDMA multiple access interference cancellation using signal estimation
US5724378A (en) CDMA multiuser receiver and method
US6658047B1 (en) Adaptive channel equalizer
US6922434B2 (en) Apparatus and methods for finger delay selection in RAKE receivers
Holtzman DS/CDMA successive interference cancellation
US6714585B1 (en) Rake combining methods and apparatus using weighting factors derived from knowledge of spreading spectrum signal characteristics
US6430216B1 (en) Rake receiver for spread spectrum signal demodulation
US6069912A (en) Diversity receiver and its control method
US5694388A (en) CDMA demodulator and demodulation method
US6363104B1 (en) Method and apparatus for interference cancellation in a rake receiver
US6205166B1 (en) CDMA receiver with antenna array adaptively controlled with combined errors of despread multipath components
US5692006A (en) Adaptive despreader
US5646964A (en) DS/CDMA receiver for high-speed fading environment
US5572552A (en) Method and system for demodulation of downlink CDMA signals
US20030013468A1 (en) Radio communication system
US5757845A (en) Adaptive spread spectrum receiver
US20080043680A1 (en) Receiver processing systems
US20060153283A1 (en) Interference cancellation in adjoint operators for communication receivers
US6201799B1 (en) Partial decorrelation for a coherent multicode code division multiple access receiver
US6782036B1 (en) Smart antenna multiuser detector
US6882678B2 (en) Method and system for canceling multiple access interference in CDMA wireless communication system

Legal Events

Date Code Title Description
AS Assignment

Owner name: TELCORDIA TECHNOLOGIES, INC., A CORPORATION OF DEL

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LIBERTI, JOSEPH CHARLES (JR.);MOSHAVI, SHIMON;ZABLOCKY, PAUL GERALD;REEL/FRAME:011861/0937;SIGNING DATES FROM 20010501 TO 20010508

AS Assignment

Owner name: JPMORGAN CHASE BANK, N.A., AS ADMINISTRATIVE AGENT

Free format text: SECURITY AGREEMENT;ASSIGNOR:TELCORDIA TECHNOLOGIES, INC.;REEL/FRAME:015886/0001

Effective date: 20050315

AS Assignment

Owner name: TELCORDIA TECHNOLOGIES, INC., NEW JERSEY

Free format text: TERMINATION AND RELEASE OF SECURITY INTEREST IN PATENT RIGHTS;ASSIGNOR:JPMORGAN CHASE BANK, N.A., AS ADMINISTRATIVE AGENT;REEL/FRAME:019520/0174

Effective date: 20070629

Owner name: TELCORDIA TECHNOLOGIES, INC.,NEW JERSEY

Free format text: TERMINATION AND RELEASE OF SECURITY INTEREST IN PATENT RIGHTS;ASSIGNOR:JPMORGAN CHASE BANK, N.A., AS ADMINISTRATIVE AGENT;REEL/FRAME:019520/0174

Effective date: 20070629

AS Assignment

Owner name: TELCORDIA TECHNOLOGIES, INC., NEW JERSEY

Free format text: RELEASE OF SECURITY INTEREST;ASSIGNOR:WILMINGTON TRUST COMPANY;REEL/FRAME:022408/0410

Effective date: 20090220

Owner name: TELCORDIA TECHNOLOGIES, INC.,NEW JERSEY

Free format text: RELEASE OF SECURITY INTEREST;ASSIGNOR:WILMINGTON TRUST COMPANY;REEL/FRAME:022408/0410

Effective date: 20090220

AS Assignment

Owner name: TELCORDIA LICENSING COMPANY LLC, NEW JERSEY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TELCORDIA TECHNOLOGIES, INC.;REEL/FRAME:022878/0348

Effective date: 20090616

AS Assignment

Owner name: TTI INVENTIONS C LLC, DELAWARE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TELCORDIA LICENSING COMPANY LLC;REEL/FRAME:027927/0853

Effective date: 20111102