|Publication number||USRE42681 E1|
|Application number||US 11/124,595|
|Publication date||Sep 6, 2011|
|Filing date||May 5, 2005|
|Priority date||May 28, 1999|
|Also published as||DE60017836D1, DE60017836T2, EP1073212A2, EP1073212A3, EP1073212B1, US6594473|
|Publication number||11124595, 124595, US RE42681 E1, US RE42681E1, US-E1-RE42681, USRE42681 E1, USRE42681E1|
|Inventors||Anand G. Dabak, Srinath Hosur|
|Original Assignee||Texas Instruments Incorporated|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (22), Classifications (30), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
More than one reissue application has been filed for the reissue of U.S. Pat. No. 6,594,473. The reissue applications are application Ser. No. 11/287,564 and the instant reissue application.
This application claims the benefit, under 35 U.S.C. §119(e)(1), of U.S. Provisional Application No. 60/136,413, filed May 28, 1999, and incorporated herein by this reference.
The present embodiments relate to wireless communications systems and, more particularly, to transmitters with multiple transmit antennas used in such systems.
Wireless communications have become very prevalent in business, personal, and other applications, and as a result the technology for such communications continues to advance in various areas. One such advancement includes the use of spread spectrum communications, including that of code division multiple access (“CDMA”) and wideband code division multiple access (“WCDMA”) cellular communications. In such communications, a user station (e.g., a hand held cellular phone) communicates with a base station, where typically the base station corresponds to a “cell.”
Due to various factors including the fact that CDMA communications are along a wireless medium, an originally transmitted communication from a base station to a user station may arrive at the user station at multiple and different times. Each different arriving signal that is based on the same original communication is said to have a diversity with respect to other arriving signals originating from the same transmitted communication. Further, various diversity types may occur in CDMA communications, and the CDMA art strives to ultimately receive and process the originally transmitted data by exploiting the effects on each signal that are caused by the one or more diversities affecting the signal.
One type of CDMA diversity occurs because a transmitted signal from the base station is reflected by objects such as the ground, mountains, buildings, and other things that it contacts. As a result, a same single transmitted communication may arrive at the receiver at numerous different times, and assuming that each such arrival is sufficiently separated in time, then each different arriving signal is said to travel along a different channel and arrive as a different “path.” These multiple signals are referred to in the art as multiple paths or multipaths. Several multipaths may eventually arrive at the user station and the channel traveled by each may cause each path to have a different phase, amplitude, and signal-to-noise ratio (“SNR”). Accordingly, for one communication between one base station and one user station, each multipath is a replica of the same user information, and each path is said to have time diversity relative to other mulitpath(s) due to the difference in arrival time which causes different (uncorrelated) fading/noise characteristics for each multipath. Although multipaths carry the same user information to the receiver, they may be separately recognized by the receiver based on the timing of arrival of each multipath. More particularly, CDMA communications are modulated using a spreading code which consists of a series of binary pulses, and this code runs at a higher rate than the symbol data rate and determines the actual transmission bandwidth. In the current industry, each piece of CDMA signal transmitted according to this code is said to be a “chip,” where each chip corresponds to an element in the CDMA code. Thus, the chip frequency defines the rate of the CDMA code. Given the use of transmission of the CDMA signal using chips, then multipaths separated in time by more than one of these chips are distinguishable at the receiver because of the low autocorrelations of CDMA codes as known in the art.
In contrast to multipath diversity which is a natural phenomenon, other types of diversity are sometimes designed into CDMA systems in an effort to improve SNR, thereby improving other data accuracy measures (e.g., bit error rate (“BER”), frame error rate (“FER”), and symbol error rate (“SER”)). An example of such a designed diversity scheme is antenna diversity and is introduced here since it has particular application to the preferred embodiments discussed later. Antenna diversity, or sometimes referred to as antenna array diversity, describes a wireless system using more than one antenna by a same station. Antenna diversity often proves useful because fading is independent across different antennas. Further, the notion of a station using multiple antennas is more typically associated with a base station using multiple antennas to receive signals transmitted from a single-antenna mobile station, although more recently systems have been proposed for a base station using multiple antennas to transmit signals transmitted to a single-antenna mobile station. Each of these alternatives is further explored below.
Certain antenna array diversity techniques suggest the use of more than one antenna at the receiver, and this approach is termed receive antenna diversity. For example, in prior art analog systems, often a base station receiver was equipped with two antennas, each for receiving a signal from a single-antenna mobile station. Thus, when the single-antenna mobile station transmits to the base station, each receiver antenna provides at least one corresponding received signal for processing. By implementing multiple receive antennas, the performance of an ideal receiver is enhanced because each corresponding received signal may be separately processed and combined for greater data accuracy.
More recently there have been proposals to use more than one antenna at the transmitter, and this approach is termed transmit antenna diversity. For example, in the field of mobile communications, a base station transmitter is equipped with two antennas for transmitting to a single-antenna mobile station. The use of multiple antennas at the base station for transmitting has been viewed as favorable over using multiple antennas at the mobile station because typically the mobile station is in the form of a hand-held or comparable device, and it is desirable for such a device to have lower power and processing requirements as compared to those at the base station. Thus, the reduced resources of the mobile station are less supportive of multiple antennas, whereas the relatively high-powered base station more readily lends itself to antenna diversity. In any event, transmit antenna diversity also provides a form of diversity from which SNR may be improved over single antenna communications by separately processing and combining the diverse signals for greater data accuracy at the receiver. Also in connection with transmit antenna diversity and to further contrast it with multipath diversity described above, note that the multiple transmit antennas at a single station are typically within several meters (e.g., three to four meters) of one another, and this spatial relationship is also sometimes referred to as providing spatial diversity. Given the spatial diversity distance, the same signal transmitted by each antenna will arrive at a destination (assuming no other diversity) at respective times that relate to the distance between the transmitting antennas. However, the difference between these times is considerably smaller than the width of a chip and, thus, the arriving signals are not separately distinguishable in the same manner as are multipaths described above.
Given the development of transmit antenna diversity schemes, two types of signal communication techniques have evolved to improve data recognition at the receiver given the transmit antenna diversity, namely, closed loop transmit diversity and open loop transmit diversity. Both closed loop transmit diversity and open loop transmit diversity have been implemented in various forms, but in all events the difference between the two schemes may be stated with respect to feedback. Specifically, a closed loop transmit diversity system includes a feedback communication channel while an open loop transmit diversity system does not. Both of these systems as well as the distinction between them are further detailed below.
Transmitter 12 receives information bits Bi at an input to a channel encoder 13. Channel encoder 13 encodes the information bits Bi in an effort to improve raw bit error rate. Various encoding techniques may be used by channel encoder 13 and as applied to bits Bi, with examples including the use of convolutional code, block code, turbo code, or a combination of any of these codes. The encoded output of channel encoder 13 is coupled to the input of an interleaver 15. Interleaver 15 operates with respect to a block of encoded bits and shuffles the ordering of those bits so that the combination of this operation with the encoding by channel encoder 13 exploits the time diversity of the information. For example, one shuffling technique that may be performed by interleaver 15 is to receive bits in a matrix fashion such that bits are received into a matrix in a row-by-row fashion, and then those bits are output from the matrix to a symbol mapper 16 in a column-by-column fashion. Symbol mapper 16 then converts its input bits to symbols, designated generally as Si. The converted symbols Si may take various forms, such as quadrature phase shift keying (“QPSK”) symbols, binary phase shift keying (“BPSK”) symbols, or quadrature amplitude modulation (“QAM”) sybmols. In any event, symbols Si may represent various information such as user data symbols, as well as pilot symbols and control symbols such as transmit power control (“PC”) symbols and rate information (“RI”) symbols. Symbols Si are coupled to a modulator 18. Modulator 18 modulates each data symbol by combining it with, or multiplying it times, a CDMA spreading sequence which can be a pseudonoise (“PN”) digital signal or PN code or other spreading codes (i.e., it utilizes spread spectrum technology). In any event, the spreading sequence facilitates simultaneous transmission of information over a common channel by assigning each of the transmitted signals a unique code during transmision. Further, this unique code makes the simultaneously transmitted signals over the same bandwidth disinguishble at receiver 14 (or other receivers). Modulator 18 has two outputs, a first output 18 1 connected to a multiplier 20 1 and a second output 18 2 connected to a multiplier 20 2. Each of multipliers 20 1 and 20 2 multiplies its input times a weight value, W1 and W2, respectively, and provides an output to a respective transmit antenna A12 1 and A12 2. By way of example, assume that transmit antennas A12
Receiver 14 includes a receive antenna A14 1 for receiving communications from both of transmit antennas A12 1 and A12 2. Recall that such communications may pass by various multipaths, and due to the spatial relationship of transmit antennas A12 1 and A12 2, each multipath may include a communication from both transmit antenna A12 1 and transmit antenna A12 2. In the illustration of
Returning to open loop diversity decoder 23 of receiver 14, once it applies the estimates to the despread data, its result is output to a deinterleaver 25 which operates to perform an inverse of the function of interleaver 15, and the output of deinterleaver 25 is connected to a channel decoder 26. Channel decoder 26 may include a Viterbi decoder, a turbo decoder, a block decoder (e.g., Reed-Solomon decoding), or still other appropriate decoding schemes as known in the art. In any event, channel decoder 26 further decodes the data received at its input, typically operating with respect to certain error correcting codes, and it outputs a resulting stream of decoded symbols. Indeed, note that the probability of error for data input to channel decoder 26 is far greater than that after processing and output by channel decoder 26. For example, under current standards, the probability of error in the output of channel decoder 26 may be between 10−3 and 10 −6. Finally, the decoded symbol stream output by channel decoder 26 may be received and processed by additional circuitry in receiver 14, although such circuitry is not shown in
Having detailed system 10, attention is now returned to its identification as a closed loop system. Specifically, system 10 is named a closed loop system because, in addition to the data communication channels from transmitter 12 to receiver 14, system 10 includes the feedback communication channel for communicating weights W1 and W2 from receiver 14 to transmitter 12; thus, the data communication and feedback communication channels create a circular and, hence, “closed” loop system. Note further that weights W1 and W2 may reflect various channel affecting aspects. For example, receiver 14 may ascertain a level of fading in signals it receives from transmitter 12, such as may be caused by local interference and other causes such as the Doppler rate of receiver 14 (as a mobile station), and in any event where the fading may be characterized by Rayleigh fading. As a result, receiver 14 feeds back weights W1 and W2 and these weights are used by multipliers 20 1 and 20 2, thereby applying weight W1 to various symbols to provide a transmitted signal along transmitter antenna A12 1 and applying weight W2 to various symbols to provide a transmitted signal along transmitter antenna A12 2. Thus, for a first symbol S1 to be transmitted by station 12, it is transmitted as part of a product W1S1 along transmitter antenna A12 1 and also as part of a product W2S2 along transmitter antenna A12 2. By way of illustration, therefore, these weighted products are also shown in
Turning now to a prior art open loop transmit diversity system, it may described generally and in comparison to the closed loop system 10 of
To further depict open loop transmit diversity,
The operation of transmitter 30 is now explored, and recall in general from above that open loop system transmitters adjust data differently at each transmit antenna without the assistance of feedback. In the case of transmitter 30, STTD encoder 32 first buffers a number of symbols equal to the number of transmit antennas. In the example of
Having detailed both closed loop and open loop transmit antenna diversity systems, additional observations are now made regarding the benefits and drawbacks of each. In general, under the ideal situation, a closed loop system outperforms an open loop system for a given transmitted signal power. However, due to non-ideal occurrences in the feedback information, a closed loop system may be inferior to an open loop system in some situations. For example, as Doppler fading increases, by the time the feedback information is received by the transmitter, the weights included or derived from the feedback information may be relatively outdated and therefore less effective when applied to future transmissions by the transmitter. Conversely, because the open loop system does not implement feedback from the receiver to the transmitter, then such a system may provide greater performance in a high Doppler environment. In the prior art, the drawbacks of both the closed loop and open loop systems have been addressed in one manner by further increasing the number of antennas in either the closed loop or open loop system. While this approach may improve error rates as compared to fewer antennas for the same system, there are diminishing returns in data error rates to be considered versus the complexities of adding more antennas to a system. Moreover, for each antenna added to a closed loop diversity system, there is a corresponding increase in the amount of bandwidth required to accommodate the additional feedback information required for the added transmit antenna.
In view of the above, there arises a need to improve upon the drawbacks of prior art closed loop systems and prior art open loop Systems, and such a need is addressed by the preferred embodiments described below.
In the preferred embodiment, there is a wireless communication system. The system comprises transmitter circuitry comprising encoder circuitry for receiving a plurality of symbols. The system further comprises a plurality of antennas coupled to the transmitter circuitry and for transmitting signals from the transmitter circuitry to a receiver, wherein the signals are responsive to the plurality of symbols. Further, the encoder circuitry is for applying open loop diversity and closed loop diversity to the plurality of symbols to form the signals. Other circuits, systems, and methods are also disclosed and claimed.
In various respects, system 40 may operate according to known general techniques for various types of cellular or other spread spectrum communications, including CDMA or WCDMA communications. Such general techniques are known in the art and include the commencement of a call from user station UST and the handling of that call by base station BST. Where system 40 differs from the prior art, however, is the system for, and method of, communicating signals from each of the four antennas AT1 through AT4 to user station UST. These distinctions are further detailed below in connection with
Looking to base station BST in
The operation of transmitter 42 is as follows. First, recall it is noted above that system 40 combines open loop and closed loop communication techniques. In the embodiment of
The open loop communication aspect of transmitter 42 may be appreciated by way of example with respect to STUD encoder 44, and note that the signals output by STTD encoder 44 to antennas AT1 and AT2 are shown in
The open loop diversity communication technique of system 40 may be appreciated further with reference to the pair of transmit antennas AT3 and AT4 and STTD encoder 46 which outputs signals to those antennas. Looking to the signals output along antennas AT3 and AT4, they each have a common factor of a weight, W2. Looking to the factors other than the weight, W2, in the output signals of STTD encoder 46, such signals alone also represent an open loop diversity communication technique. Specifically, STTD encoder 46 also buffers symbols S1 and S2 and transmits them in the same manner as STTD encoder 44 described above. Thus, STTD encoder 46 directly transmits symbols S1 and S2 along antenna AT3 (at time T′ and 2T, respectively) and STTD 46 encoder at the same time transmits −S*2, the negative symbol conjugate of the second symbol, at time T′ followed by S*1, the positive symbol conjugate of the first symbol, at time 2T′. These communications further demonstrate that system 40 implements an open loop communication technique relative to the pair of transmit antennas AT3 and AT4.
The closed loop diversity communication aspect of transmitter 42 may be appreciated by examining the differences in the output signals of STTD encoders 44 and 46, and further in view of user station UST. Looking first to user station UST, it includes a despreader 48, an open and closed loop diversity decoder 49, a channel estimator 50, a deinterleaver 51, and a channel decoder 52. Each of these devices may be constructed and operate according to techniques in various respects ascertainable by one skilled in the art and in view of the earlier discussion relative to
Having demonstrated the use of weights W1 and W2 in the closed loop aspect of system 40, attention is now directed to the generation of the optimum value for those weights by channel estimator 50. Specifically, these weights are calculated as follows. First, the following Equation 1 defines a matrix,
Next, the following Equations 2 and 3 define channel impulse response matrices for each of antennas AT1 through AT4 in system 40, where hi is the channel impulse response matrix for antenna AT1 in system 40.
H1=[h1h3] Equation 2
H2=[h2h4] Equation 3
For each of Equations 2 and 3, if there are a total of N resolvable multipaths from base station BST to user station UST, then hi is further defined as a vector relating to each of those multipaths as shown in the following Equation 4:
Next, a term r1 is defined in Equation 5 and is the signal received by user station UST after despreading the signal transmitted over time [0, T) and taking into account a noisefactor, n1:
r1=h1W1S1−h2W1S*2+h3W2S1−h4W2S*2+n1 Equation 5
Similarly, a term r2 is defined in Equation 6 and is the signal received by user station UST after despreading the signal transmitted over time [T, 2T), and taking into account a noise factor, n2:
r2=h1W1S2+h2W1S*1+h3W2S2+h4W2S*1+n2 Equation 6
Rearranging the preceding yields Equation 7 for the value r1:
Rearranging the preceding yields Equation 8 for the value r2:
When signals r1 and r2 reach decoder 52, they are decoded as known in the STFD art. This decoding therefore may be represented as in the following Equation 9, and using the conventions that the symbol (.)H denotes conjugate transpose of a vector, the symbol (.)T denotes a transpose of a vector, and the symbol (.)* denotes its conjugate:
Equation 10 then implies the following Equation 11:
The signal to noise ratio for symbol S1 is now given by Equation 13:
where σ2=E[n1 Hn1]=E[n2 Hn2] is the variance of the noise.
Similarly the SNR for symbol S2 is given by Equation 14:
Maximization of Equations 13 and 14 with respect to the weight vector implies the calculation of the eigen vectors for the matrix (H1 HH1+H2 HH2). Let V1, V2 indicate the two eigen vectors and μ1, μ2 be the two corresponding eigen values. User station UST picks the eigen vector with the maximum eigen value implying that:
User station UST then sends back the weight values W1 and W2 back to base station BST. Normalizing the weight W1=1, user station UST can optionally send back only the ratio (W2/W1) to base station BST and base station BST then sets the weights on the antennas accordingly.
To further illustrate Equations 1 through 15 for simplicity, assume that there is only one multipath from base station BST to user station UST implying that N=1. Given this assumption, then user station UST receives the following two symbols shown in Equations 16 and 17 after despreading:
where N1 and N2 are additive white Guassian noise.
Rearranging Equations 16 and 17 yields the following Equations 18 and 19, respectively:
For subsituting into Equations 18 and 19, and letting
then one skilled in the art will appreciate that Equations 18 and 19 are in the form of standard STTD implying that the total SNR for each symbol S1 and S2 after STTD decoding will be as shown in the following Equation 20:
Having detailed system 40, various of its advantages now may be observed. For example, system 40 achieves a 2N path diversity where N is the number of paths from base station BST to user station UST. As another example, versus an open loop approach alone, there is an increase of a 3 dB gain in average SNR due to the use of closed loop transmit diversity across the two antenna groups (i.e., AT1 and AT2 versus AT3 and AT4). As still another example, the required reverse link bandwidth for providing the W1 and W2 feedback information is that corresponding to only two antennas while system 40 is supporting four transmit antennas. As a final example, the processing operations for receiving data by user station UST may be implemented using standard STTD decoding for each of the symbols S1, S2. From each of the preceding advantages, one skilled in the art should appreciate that the preferred embodiment achieves better performance with a lesser amount of complexity than is required in a prior art approach that increases the number of transmit antennas for a given (i.e., either closed or open) diversity scheme. As yet another advantage of the preferred embodiments, while such embodiments have been described in detail, various substitutions, modifications or alterations could be made to the descriptions set forth above without departing from the inventive scope. To further appreciate this inventive flexibility, various examples of additional changes contemplated within the preferred embodiments are explored below.
While the example of system 40 has demonstrated the use of four transmit antennas, the inventive implementation of system 40 also may be applied to wireless systems with other numbers of antennas, again using a combination of open loop transmit diversity and closed loop transmit diversity as between subsets of the entire number of transmit antennas. For example, one alternative embodiment contemplated includes six transmit antennas, which for the sake of discussion let such antennas be referred to as AT10 through AT15. With this system, open loop transmit diversity may applied to pairs of those antennas, as with a first antenna pair AT10 and AT11, a second antenna pair AT12 and AT13, and a third antenna pair AT14 and AT15. Further, closed loop transmit diversity may then be applied between each of those pairs of antennas, whereby a first weight is applied to signals transmitted by the first antenna pair, a second weight is applied to signals transmitted by the second antenna pair, and a third weight is applied to signals transmitted by the third antenna pair. As another example, a combination of open loop transmit diversity and closed loop transmit diversity may be applied to a transmitter with eight antennas. In this case, however, various additional alternatives exist. For example, the eight antennas may be split into four pairs of antennas, where open loop transmit diversity is applied within each pair of antennas, and closed loop transmit diversity is applied as between each antenna pair (i.e., four different weights, one for each antenna pair). Alternatively, the eight antennas may be split into two sets of four antennas each, where open loop transmit diversity is applied within each set of four antennas, and closed loop transmit diversity is applied as between the sets (i.e., two different weights, one for each set of four antennas).
Also while the previous examples have demonstrated more than two transmit antennas, it is recognized in connection with the present inventive aspects that a combination of open loop transmit diversity and closed loop transmit diversity may prove worthwhile for a transmitter with only two transmit antennas. Specifically, instances may arise where a transmitter in a closed loop diversity system receives feedback from a receiver to develop weights for future transmissions, but due to some factor (e.g., high Doppler) the transmitter is informed of some reduced amount of confidence in the weights; for such an application, therefore, an alternative of the preferred embodiment may be created by adding an open loop diversity technique to the closed-loop transmissions, thereby creating a combined diversity system.
The operation of encoder 60 may be understood in view of the principles discussed above, and further in view of the signals shown as output to antennas A60 1 and A60 2. For example, at time T′, antenna A60 1 outputs a combined signal formed by two addends, W3W1S1+W4S1, while at the same time T′ antenna A60 2 outputs a combined signal formed by two addends, W3W2S1−W4S2*. The notion of combining an open and closed loop diversity may be appreciated from these combined signals by looking at the addends in each signal; specifically, as shown below, encoder 60 operates so that for each signal transmitted it includes two addends, where the second-listed addend has a closed loop diversity and the first-listed addend has an open loop diversity. Each of the diversity types is separately discussed below.
To appreciate the open loop addends communicated by encoder 60, assume that W3=0 in which case the signals communicated by antennas A60 1 and A60 2 at time T′ reduce to the second-listed addends of the combined signals shown above. Specifically, for W3=0, the signals output at time T′ by encoder 60 reduce to an output of W4S1 by antenna A60 1 and an output of −W4S2* by antenna A60 2. By removing the common factor of W4 from these two addends, one skilled in the art will appreciate that the remaining factors (i.e., S1 for antenna A60 1 and −S2* for antenna A60 2) have an open loop diversity with respect to one another. This same observation with respect to open loop diversity may be found at time 2T′. Specifically, if W3=0, then the signals output at time 2T′ by encoder 60 reduce to an output of W4S2 by antenna A60 1 and an output of W4S1* by antenna A60 2. By removing the common factor of W4 from these two addends, one skilled in the art will appreciate that the remaining factors (i.e., S2 for antenna A60 1 and S1* for antenna A60 2) have an open loop diversity with respect to one another.
To appreciate the closed loop addends communicated by encoder 60, assume that W4=0 in which case the signals communicated by antennas A60 1 and A60 2 at time T′ reduce to the first-listed addends of the combined signals shown above. Thus, for W4=0, the signals output at time T′ by encoder 60 reduce to an output of W3W1S1 by antenna A60 1 and an output of W3W2S1 by antenna A60 2. By removing the common factor of W3 from these two addends, one skilled in the art will appreciate that the remaining factors (i.e., W1S1 for antenna A60 1 and W2S1 for antenna A60 2) have a closed loop diversity with respect to one another inasmuch as they represent a product involving the same symbol but with a different weight multiplied times each symbol. This same observation with respect to closed loop diversity may be found at time 2T. Specifically, if W4=0, then the signals output at time 2T′ by encoder 60 reduce to W3W1S2 by antenna A60 1 and an output of W3W2S2 by antenna A60 2. Once more, by removing the common factor of W3 from these two addends, one skilled in the art will appreciate that the remaining factors (i.e., W1S2 for antenna A60 1 and W2S2 for antenna A60 2) have an open loop diversity with respect to one another.
Concluding the discussion of
As still another example of the present inventive scope, the types of open loop and closed loop transmit diversity also may be changed as applied to the preferred embodiments. Thus, while TxAA has been shown above as a closed loop technique, and STTD has been shown as an open loop technique, one or both of these may be replaced by corresponding alternative techniques and applied to a multiple transmit antenna system, thereby again providing a combined closed loop and open loop transmit antenna system. Indeed, recall above an example is set forth for an inventive system having eight antennas split into sets of four antennas, where open loop transit diversity is applied within each set of four antennas. In this case, the application of open loop transmit diversity as applied within a set of four antennas will require a type of open loop diversity other than solely the transmission of conjugates; in other words, a use only of conjugates provides two different signals, whereas for four different antennas a corresponding four different signals are required to achieved the open loop diversity. Accordingly, for this as well as other embodiments, a different open loop diversity approach may be implemented. For example, another open loop diversity technique that may be implemented according to the preferred embodiment includes orthogonal transmit diversity (“OTD”), and which is shown for a single OTD encoder 70 in
As still another example of the inventive scope, note that various of such teachings may be applied to other wireless systems. For example, the preceding may be applied to systems complying with the 3rd Generation partnership Project (“3GPPP”) for wireless communications, and to 3GPPP 2 systems, as well as still other standardized or non-standardized systems. Further, while the preceding example has been shown in a CDMA system (or a WCDMA system), the preferred embodiment may be implemented by including transmitter antenna diversity combining both open loop and closed loop diversity in a time division multiple access (“TDMA”) system, which has a spreading gain of one.
As a final example of the inventive scope, while the preceding embodiments have been shown in connection with a receiver having only a single antenna, note that systems using multiple receive antennas also are contemplated. In other words, therefore, the preceding also may be combined with various techniques of receive antenna diversity.
From the preceding, one skilled in the art should appreciate various aspects of the inventive scope, as is defined by the following claims.
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|U.S. Classification||455/101, 375/141, 375/146, 375/147, 370/201, 375/267, 455/133, 370/339, 370/334, 375/148, 455/103, 370/209, 370/441, 455/132|
|International Classification||H04B1/02, H04B7/02, H04L1/06, H04B7/06, H03C7/02, H04B7/26, H04J13/00|
|Cooperative Classification||H04B7/061, H04B7/0673, H04B7/0634, H04B7/0669, H04L1/0618|
|European Classification||H04B7/06B2F, H04L1/06T, H04B7/06C1F1W, H04B7/06C2C|