TWI387245B - Code interleaving for a structured code - Google Patents

Description

Structured code code interleaving

Code Division Multiple Access (CDMA) is a modulation and multiple access scheme that uses wideband spread spectrum techniques for signal transmission, as opposed to the use of narrowband channel techniques in conventional analog systems. Therefore, the information contained in a transmission is spread over a very large frequency band, thereby facilitating the simultaneous sharing of the same frequency band by multiple users. This involves applying a code to a data bit that explicitly identifies information pertaining to a particular call (user) in a particular geographic location such that at the receiver end only the same code can read it. Thus, the data bits of all users in a particular geographic cell (a local transceiver station typically can reach that particular geographic cell) are simultaneously transmitted across the wide spectrum. The user's device picks up the signals and discards all of the coded bits except those that are explicitly targeted to them. The user device then strips the code and restores the transmission to its original data stream. Since the use of a spread signal with more bandwidth than the data signal modulates the data signal, the spread spectrum technique causes the data to unnecessarily occupy more bandwidth. The bit that implements the extension of the signal is called a chip. Therefore, CDMA can improve privacy and security by picking up a signal that spreads over the spectrum and requires knowledge about the code separating a call from another call, which is easier to monitor using a radio receiver. The signals concentrated in the narrow frequency band are opposite.

Each user in a CDMA communication system can be identified in a variety of ways. Orthogonal multiple access is a technique in which a user is assigned one of a plurality of orthogonal waveforms obtained from an orthogonal code. If the cross-correlation of the two signals is zero for a zero time shift, then they are orthogonal. Cross-correlation is a general measure of the degree to which two different time-shifted signals are shifted over time. Therefore, the orthogonal signals/waveforms assigned to different users simultaneously do not interfere with each other.

An example of an orthogonal code set is a Walsh set. The Walsh function is generated by using an iterative process of constructing a Hadamard matrix starting with H ₁ =[0]. Therefore, the Walsh function is used for two purposes in CDMA. It is used in a forward link of a base station-to-mobile terminal to form an independent transmission channel. It is used to perform quadrature modulation from a mobile terminal to the reverse link of the base station. However, message signals processed via orthogonal Walsh sequences are susceptible to false alarms and channel decorrelation, where a time shifted version of a transmitted Walsh sequence is erroneously identified as transmitted data, resulting in performance degradation.

A simplified summary of the subject matter of the invention is set forth below to provide a basic understanding of certain aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is not intended to identify key or critical elements of the claimed subject matter, and is not intended to limit the scope of the claimed subject matter. Its sole purpose is to present some concepts of the subject matter of the present invention

The communication system in accordance with an embodiment of the present invention described herein provides a transmitter that includes a channelizer/expander, a code interleaver, and a scrambler. The channelizer provides extended data by processing a received data using a channelized code. The code interleaver reorders the data received from the channelizer and provides the interleaved data to the scrambler. The scrambler uses the PN sequence to scramble the interleaved data and transmit the scrambled signal.

Another embodiment relates to a receiver operable to be used with the transmitter described above. The receiver includes a descrambler, a deinterleaver, a dechannelizer/despreader, and a combiner. The descrambler receives the scrambled input from the receiver and multiplies it by a PN sequence used to scramble the input, and provides the descrambled input. A chip deinterleaver deinterleaves the output from the descrambler in a manner complementary to the interleaving performed during transmission. The deinterleaved chips are then provided to a dechannelizer/despreader that provides extended symbols. A combiner combines despread symbols from a plurality of finger elements or receiving antennas to provide detected data.

According to another aspect, orthogonal Walsh codes are used to extend the information within the communication system. Thus, yet another embodiment includes a transmitter in which a Walsh mapper maps message material including K bits to a specific Walsh code of length L = ^2K . A code interleaver interleaves the L chips of the Walsh code. A scrambler multiplies the interlaced chips by a PN sequence of chips and provides scrambled chips for transmission.

According to still another aspect, a receiver operable to read a message from the transmitter includes a descrambler, a deinterleaver, a FHT unit, a combiner, and a message detector. The descrambler unwinds the message received from the transmitter and provides it to the deinterleaver. The deinterleaver deinterleaves the message bits and provides them to an FHT (Fast Hadamard Transform) unit. The FHT unit despreads the deinterleaved chips and provides energy for each Walsh code. The combiner combines the energy of each Walsh code of a different antenna/signal path. A channel detector identifies the Walsh code with the greatest energy as the transmitted message.

Still another aspect relates to a communication method for providing extended data by processing a received data using a channelized code. The extended material is then reordered to provide interleaved data for scrambling. The PN sequence is then used to scramble the interleaved data and transmit the interleaved data. Since the extended data is interleaved prior to transmission, any phase slopes of Doppler due to the launch motion will be dispersed within the interlaced chips, thereby breaking the structure that would result in a higher false alarm.

Yet another aspect relates to a method of receiving data for obtaining transmissions according to the previously described method of transmission. The method involves receiving a scrambled input and multiplying it by a PN sequence used to scramble the input to obtain the descrambled input. The de-scrambled chips are then deinterlaced in a staggered complement that is implemented during transmission. The deinterlaced chips are then despread to obtain the despread symbols. The despread symbols from the plurality of finger elements or receiving antennas are then combined to provide the detected data.

According to still another aspect, orthogonal Walsh codes are used to extend the information within the communication system. Accordingly, another embodiment includes a transmission method in which message material including K bits is mapped to a specific Walsh code of length L = ^2K . Then, the L chips of the Walsh code are interleaved. The chips of a PN sequence are then used to scramble the interlaced chips and then transmit the interlaced chips.

Yet another aspect relates to a method of receiving and processing signals to obtain a message that is mapped to a Walsh code and transmitted as described above. Initially, unscramble and deinterlace the received data. The deinterleaved message bits are then despread. An energy value reflecting the likelihood that the Walsh code is to transmit a Walsh code is provided for the despread Walsh codes. Combine the energy of each Walsh code of a different antenna/signal path. The Walsh code with the greatest energy is identified, and if it exceeds a certain threshold, it is declared as the transmitted message, otherwise an erase is indicated.

The following description and the annexed drawings set forth in the claims However, the present invention is intended to cover only a few of the various embodiments of the subject matter of the invention. Other advantages and distinguishing features of the subject matter claimed in the present invention are set forth in the Detailed Description of the <RTIgt;

The subject matter of the present invention is now described with reference to the drawings, in which the same reference numerals are used throughout the drawings. For the sake of explanation, numerous specific details are set forth in the following description in order to provide a thorough understanding of the claimed subject matter. However, it is apparent that the subject matter of the invention may be practiced without the specific details. In other instances, well-known structures and devices are shown in the <RTIgt;

The embodiments are described with reference to the drawings, in which the same reference numerals are used throughout the drawings. In the following description, for the purposes of illustration However, it is apparent that such embodiments may be practiced without such specific details. In other instances, well-known structures and devices are shown in the form of a block diagram in order to illustrate one or more embodiments.

The terms "component", "module", "system" and similar terms used in this application are intended to mean a computer-related entity that is a combination of hardware, firmware, hardware and software, software or is being executed. Software in the middle. For example, a component can be, but is not limited to being, a process running on a processor, a processor, an object, an executable file, a thread of execution, a program, and/or a computer. For example, an application running on a computing device and the device can be a component. One or more components can reside within a process and/or an execution thread, and a component can be localized on a computer and/or distributed between two or more computers. In addition, such components can execute from various computer readable media having various data structures stored thereon. The components can communicate by local and/or remote processes, for example, based on a signal having one or more data packets (eg, from one interacting with another component in a local system, a distributed system) A function, and/or a component of a component that interacts with other systems over a network (eg, the Internet) by means of a signal).

In addition, various embodiments are also described herein in connection with a wireless terminal and/or a base station. A wireless terminal can refer to a device that provides voice and/or data connectivity to a user. A wireless terminal can be coupled to a computing device such as a laptop or desktop computer, or it can be a "self contained" device, such as a PDA. A wireless terminal can also be called a system, a subscriber unit, a subscriber station, a mobile station, a mobile device, a remote station, an access point, a remote terminal, an access terminal, a user terminal, a user agent. , user device or user device. The wireless terminal can be a subscriber station, a wireless device, a cellular phone, a PCS phone, a cordless phone, a conversation initiation protocol (SIP) phone, a wireless local loop (WLL) station, a number of person assistants (PDAs), and a wireless device. A handheld device with connectivity, or other processing device connected to a wireless data processor. A base station (e.g., an access point) can refer to a device in an access network that can communicate with a wireless terminal over an empty interfacing plane via one or more sectors. The base station can act as a router between the wireless terminal and the rest of the access network by converting the received empty intermediaries into IP packets, the access network including an internet protocol (IP) network. The base station also coordinates the property management of the empty intermediary. In addition, the various aspects or features described herein can be constructed as a method, apparatus, or article of manufacture using standard stylized and/or engineering techniques. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. By way of example, computer readable media may include, but are not limited to, magnetic storage devices (eg, hard disks, floppy disks, magnetic strips...), optical disks (eg, compact disks (CDs), digital versatile compact disks (DVD). ..), smart card, and flash memory devices (such as cards, sticks, flash drives).

Embodiments are described below in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules, etc. discussed in connection with the drawings. You can also use one of these methods to combine.

Referring now to the drawings, FIG. 1 is a diagram of a wireless multiple access communication system 100 in accordance with various aspects. In one example, wireless multiple access communication system 100 includes a plurality of base stations 110 and a plurality of terminals 120. Each base station 110 and terminal 120 in system 100 can have one or more antennas to facilitate communication with one or more base stations 110 and/or terminals 120 in system 100. In one example, a base station 110 can simultaneously transmit a plurality of data streams for broadcast, multicast, and/or unicast services, wherein the data stream is an independently receivable data stream of interest to the terminal device 120. Terminals 120 within the coverage area of a base station 110 can then receive one or more data streams transmitted from base station 110. By way of non-limiting example, a base station 110 can be an access point, a Node B, and/or other suitable network entity. Each base station 110 provides communication coverage for a particular geographic area 102. As used herein and generally in the art, the term "cell" may refer to a base station 110 and/or its coverage area 102 depending on the context in which it is used. To increase system capacity, the coverage area 102 corresponding to a base station 110 can be partitioned into a plurality of smaller areas (eg, areas 104a, 104b, and 104c). Each of the smaller regions 104a, 104b, and 104c can be servoed by a respective base transceiver subsystem (BTS, not shown). As used herein and generally in the art, the term "sector" may refer to a BTS and/or its coverage area depending on the context in which it is used. In a cell 102 having a plurality of sectors 104, the BTSs of all sectors 104 of the cell 102 can be co-located within the base station 110 of the cell 102.

In another example, system 100 can utilize a centralized architecture and can provide coordination and control for base station 110 by using a system controller 130 that can be coupled to one or more base stations 110. According to an alternative aspect, system controller 130 can be a collection of a single network entity or a network entity. Additionally, system 100 can utilize a distributed architecture so that base station 110 can communicate with one another as needed. According to an example, terminal 120 can be distributed throughout system 100. Each terminal 120 can be stationary or mobile. By way of non-limiting example, a terminal 120 may require an access terminal (AT), a mobile station, user equipment, a subscriber station, and/or other suitable network entity. The terminal can be a wireless device, a cellular phone, a personal digital assistant (PDA), a wireless data device, a palm-sized device, or the like. In one example, terminal 120 can transmit data to a base station 110 or to another terminal 120.

According to another aspect, system 100 can generate transmission resources in the form of channels. By way of non-limiting example, such channels may be generated via one or more of Code Division Multiplexing (CDM), Frequency Division Multiple (FDM) Time Division Multiplexing (TDM). Orthogonal Frequency Division Multiplexing (OFDM) (a variant of FDM) can be used to effectively partition the total bandwidth of system 100 into a plurality of orthogonal subcarriers that can then be modulated to have data. These subcarriers may also be referred to as tones, bins, and channels. Alternatively, in a time division based technique, each subcarrier may comprise a sequential time slice or a portion of a time slot. Each terminal 120 can be provided with one or more time slot/subcarrier combinations to transmit and receive information in a defined burst period or frame. The one-time division technique can also use a symbol rate hopping scheme and/or a hopping scheme.

In another example, a code division based technique can facilitate data transfer over a number of frequencies that are available at any time in a range. The data can be digitized and expanded over the available bandwidth of system 100 such that multiple terminals 120 can be overlaid on the channel and a unique serial number can be assigned to respective terminal 120. The terminal 120 can transmit in the same wide frequency block of the spectrum, wherein the signals corresponding to each terminal 120 are spread over the entire bandwidth by their respective unique spreading codes. In one example, the technique can be shared, wherein one or more of the terminals 120 can transmit and receive simultaneously. Such sharing can be achieved, for example, by spread spectrum digital modulation, in which a bit stream corresponding to a terminal 120 is encoded and spread over a very wide channel. Base station 110 can then identify the unique sequence code associated with a terminal 120 and de-assert the bits to collect the bits of the particular terminal 120 in a coherent manner.

In another example, system 100 can utilize one or more multiple access schemes, such as CDMA, TDMA, FDMA, OFDMA, single carrier FDMA (SC-FDMA), and/or other suitable multiple access schemes. OFDMA uses orthogonal frequency division multiplexing (OFDM), and SC-FDMA uses single carrier frequency division multiplexing (SC-FDM). Additionally, system 100 can use a combination of multiple access schemes, such as OFDMA and CDMA. In addition, system 100 can use various framed structures to indicate the manner in which data and communications are sent over the forward and reverse links. System 100 can further use one or more schedulers (not shown) to assign bandwidth and other system resources. In one example, a scheduler can be used at one or more of a base station 110, a terminal 120, and a system controller 130.

2 is a block diagram of an embodiment of a transmitter system 210 (also referred to as an access point) and a receiver system 250 (also referred to as an access terminal) in a MIMO system 200. At the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

In one embodiment, each data stream is transmitted on a respective transmit antenna. TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide encoded data.

The OFDM technology can be used to multiplex the encoded data of each data stream by using pilot data. The pilot data is typically a known pattern of data processed in a known manner and which can be used at the receiver system to estimate channel response. The multiplexed pilot and encoded data for each data stream is then modulated based on a particular modulation scheme selected for that data stream (eg, BPSK, QSPK, M-PSK, or M-QAM). The data rate, encoding, and modulation of each data stream can be determined based on instructions executed by processor 230.

The modulated symbols of all data streams are then provided to a TX MIMO processor 220, which may further process the modulated symbols (e.g., for OFDM). Then, TX MIMO processor 220 then provides N _T modulation symbol streams variants provided to N _T transmitters (TMTR) 222a through 222t. In some embodiments, TX MIMO processor 220 applies beamforming weights to the symbols of the data streams and to the antennas that are transmitting the symbols.

Each transmitter 222 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a suitable transmission on the MIMO channel. Modulated signal. Then, separately from the N _T transmit antennas 224a through 224t 222a through 222t of N _T modulated signals from transmitters number.

At receiver system 250, the modulated signal received by the transmit these N _R antennas 252a through 252r, and the sum is provided to a respective receiver (RCVR) 254a through 254r from the signal received by each antenna 252. Each receiver 254 conditions (eg, filters, amplifies, and downconverts) the respective received signals, digitizing the conditioned signals to provide samples, and further processing the samples to provide a corresponding "received" symbol stream .

Then, a RX data processor 260 receives from the symbol streams N N _{R R} receivers 254 based on the reception of a particular receiver processing technique to process it, to provide a number N _T "detected by the" symbol streams. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. The processing performed by RX data processor 260 is complementary to the processing performed by TX MIMO processor 220 and TX data processor 214 at transmitter system 210.

Processor 270 periodically determines which precoding matrix to use (discussed below). Processor 270 can form a reverse link message comprising a matrix index portion and a rank value portion.

The reverse link message can include various types of information about the communication link and/or the received data stream. Then, the reverse link message is processed by a TX data processor 238 (which also receives a plurality of data streams from a data source 236), modulated by a modulator 280, and transmitted via the transmitter 254a. The 254r is adjusted and transmitted back to the transmitter system 210.

At transmitter system 210, the modulated signals from receiver system 250 are received by antenna 224, adjusted by receiver 222, demodulated by demodulation transformer 240, and processed by an RX data processor 242. To extract the reverse link information transmitted by receiver system 250. Processor 230 then determines which precoding matrix to use for determining the beamforming weights and then processes the extracted information.

The advantage of spread spectrum technology for personal communication is that it can accommodate multiple users simultaneously on the same frequency. As mentioned earlier, orthogonal multiple access is a way of distinguishing between users in a CDMA communication system operating in accordance with spread spectrum techniques. Since the waveforms assigned to different users are orthogonal, users with different codes do not interfere with each other. An example orthogonal waveform set is a Walsh code/function based on a Hadamard matrix. However, processing data signals from a mobile station via orthogonal Walsh codes can be susceptible to false alarms and performance degradation. This is because the Doppler shift caused by the motion of the mobile station introduces a phase ramp into the signal signal processed via a Walsh sequence, resulting in a non-negligible correlation with another Walsh sequence. Since the channel needs to be decorrelated across the CDMA segment, this can result in increased false alarms and degraded performance. The various systems and methods described herein relate to enhancing the functionality of a CDMA communication system and thereby mitigating the effects of Doppler shifts by understanding the Doppler shift.

Spread spectrum is a means of transmission in which the data is unnecessarily occupied by a larger bandwidth by modulating the data by using an extended signal of more bandwidth than the data signal. The bandwidth extension is achieved prior to the transmission by using a channelization code that is independent of the transmitted data. At the receiving end, the same code is used to demodulate the data. Accordingly, Figure 3A shows a block diagram of an embodiment of a transmitter 310 that uses code interleaving. A channelizer/expander 320 receives the data to be transmitted, expands the data by a channelization code, and provides the extended data. The information to be transmitted may be traffic information, control data, pilot information and/or some other type of information. The channelization code can be a Walsh code, an Orthogonal Variable Extended Digital (OVSF) or some other code. The extension can be achieved by: (1) copying one of the modulated symbols to obtain L replicated symbols; and (2) multiplying the L replicated symbols by L of the channelized code to generate L chips of the modulation symbol. The one-code interleaver 322 reorders the L chips of the modulated symbol in a pseudo-random or structured manner and provides an L-interlaced chip of the modulated symbol. The interleaving is performed over the length of the channelization code. The scrambler 324 multiplies the interlaced chips by a PN sequence and provides scrambled chips. The scrambled chips (not shown in Figure 3A) are further processed and transmitted to a receiver.

FIG. 3B shows a block diagram of an embodiment of a receiver 340 that can be used with transmitter 310 of FIG. 3A. A descrambler 350 multiplies the received input samples by the PN sequence used by the transmitter 310 and provides a scrambled sample. A chip deinterleaver 352 deinterlaces the de-scrambled samples in a manner complementary to the interleaving performed by the code interleaver 322 at the transmitter 310 and provides deinterlaced samples. The deinterlacing is performed over the length of the channelization code. A de-channelizer/despreader 354 despreads the deinterleaved samples and provides despread symbols. The despreading can be achieved by: (1) multiplying L deinterlaced samples of a modulation symbol by L chips of the channelization code; and (2) accumulating L samples obtained by Get a solution extension symbol. A combiner 356 can combine the despread symbols from a plurality of finger elements and/or receive antennas and provide a final despread symbol called detected data.

CDMA combines two different spreading sequences to produce a unique channel that conveys information about a user and the geographic cell in which the user is located. Examples of such spreading sequences are pseudo-random noise (PN) sequences. The PN sequence exhibits a known sequence of either a noise-like behavior or a random sequence characteristic. It addresses the need for privacy in the communication system by providing a code that is readable only by a given user, and for other users, the code looks like noise. It is generated by using a shift register, a modulo-2 adder (XOR gate) or a feedback loop. The maximum length of a PN sequence is determined by the length of the register or the feedback network configuration. An N-bit scratchpad can occupy a different 0 and 1 combination of 2 ^N. Regardless of where the inputs are all made up of 0s that produce a zero output, the maximum length of any PN sequence will be 2 ^N -1.

Different PN sequences can be used to distinguish between different control channels (of the same user), different users, and/or different zones/base stations. The PN sequence used in this embodiment may be: a function of a control channel for transmitting the message, a user identification of a user or a mobile terminal/station that transmits or receives the message (long/intra PN sequence) A sector identifier of a base station that receives or transmits the message (end/external PN sequence) and/or other parameters. The PN sequences can be generated by a base station transmission modulator that can generate signals that are spread by the outer PN code and the inner orthogonal code. For example, the intra-orthogonal code can be a Walsh code generated by a Hadamard-Walsh function. The PN scrambling also ensures low correlation between time shifted versions of different Walsh codes to mitigate false alarms in which one time shifted version of the Walsh code is falsely detected as another Walsh code. This is beneficial because there is a poor cross-correlation of Walsh codes in the case of a time shift to delay spread in a wireless channel. Therefore, the PN scrambling reduces the probability of false alarms in the presence of delay spread.

4A is a block diagram of an embodiment of a transmitter 410 that transmits a message. For the forward link (or downlink), the transmitter 410 can be part of a base station, and for reverse link (uplink) transmission, it can be part of a mobile terminal. At transmitter 410, a Walsh mapper 420 receives a message consisting of K information bits and maps the message to a specific Walsh code having a length L = ^2K . In an embodiment where K is equal to 10, the length L of the Walsh code encoding the message will be 2 ¹⁰ (which is equal to 1024). In this embodiment, a 10-bit message has one of the 1024 possible values, and the value can be different from 1024 each having a length of 1024. Then, the Walsh mapper 420 maps the 10-bit message to The message value is used to determine a specific 1024-chip Walsh code. After mapping the K-bit message to a Walsh code of a particular L-chip, then a code interleaver 422 similar to that discussed earlier interleaves (reorders) the L codes of the Walsh code from the mapper 420. The slices are provided with L interlaced chips. The scrambler 424 receives the interlaced chips from the interleaver 422, multiplies the interleaved chips by a PN (Pseudo Random Noise) sequence of chips and provides scrambled chips. Not shown in the figure, the scrambled chips are further processed to form a composite waveform, the scrambled chips are modulated onto a sinusoidal carrier, filtered by passband, and converted to a desired Operating frequency, amplified and broadcast.

4B shows a block diagram of an embodiment of a receiver 440 that can be used with the transmitter 410 of FIG. 4A for communication. For forward link transmission, receiver 440 can be part of a terminal or, for reverse link transmission, can be part of a base station. Receiver 440 includes a plurality of finger elements or receive antennas R1, R2, ... RN. In a single receive antenna R1, a descrambler 452 receives the input samples and the PN sequence and provides a scrambled sample. A chip deinterleaver 454 deinterleaves (or reorders) the de-scrambled samples in a manner complementary to the interleaving performed by the code interleaver 422 at the transmitter 410, and provides the deinterleaved samples. Sample. An inverse fast Hadamard transform (FHT) unit 456 uses each of the L different Walsh codes to despread the deinterlaced samples and provide an energy for each Walsh code. The processing for a specified Walsh code may include: (1) multiplying the deinterleaved samples by L chips of the Walsh code; (2) accumulating the obtained L chips to obtain a despread symbol; (3) Calculate the energy of the despread symbol. As described above, when the L Walsh codes are orthogonal to each other, and there is no noise and other harmful channel effects, the energy of the Walsh code provided by the Walsh mapper 420 will be high, and the energy of other L-1 Walsh codes. Will be low or (ideally) zero.

Each set of units 452, 454, and 456 implements processing for a signal instance received from a receive antenna. Signals transmitted by transmitter 410 may arrive at the receiver via a plurality of signal paths, such as a line of sight path and/or a reflected path caused by an obstacle in the wireless environment. Thus, the signal at receiver 450 can include multiple received signal instances of different signal paths. Each sufficiently strong received signal instance may be processed by a finger processor (or simply a finger element) comprised of cells 452, 454, and 456 to obtain the energy of the L Walsh codes. Receiver 440 can also receive signals transmitted by transmitter 410 via a plurality of receive antennas R1, R2, ... RN. Input samples from each receive antenna are processed by a set of finger elements to obtain the energy of the L Walsh codes of a particular receive antenna. A combiner 458 can sum the energy from all of the finger elements and/or receive antennas of each Walsh code and provide the total energy of the Walsh code. Combiner 458 also scales the energy prior to summing (e.g., based on the SNR (signal noise ratio) or signal strength of the finger elements). It also selects the maximum energy of each Walsh code from the energy of each Walsh code for different finger elements and/or receiving antennas. Combiner 458 can also combine signals from different finger elements in other ways. Regardless of the method employed, the combination is implemented for each Walsh code across the finger and/or the receiving antenna.

A message selector 460 identifies the Walsh code having the maximum energy and compares the energy to a threshold. The selector 460 provides (1) the K bits corresponding to the Walsh code having the largest energy as the detected message if the energy exceeds the threshold (1) or (4) provides an erasure indication. The erasure occurs when the data frame is discarded due to a transmission error. This threshold can be set to achieve a desirable false alarm rate or probability. A low threshold increases the probability of declaring a wrong Walsh code and results in a higher false alarm probability. Conversely, a high threshold can result in an unrecognized transmission message. Thus, the erasure rate is a function of the target false alarm rate and the quality of the received signal.

Alternative embodiments (not shown) of transmitters 310, 410 or receivers 340, 440 may not include respective interleavers or deinterlacers. When the interleaver is not present in the transmitter (e.g., 410), the Walsh mapper inputs the L-chip orthogonal (Walsh) code to the scrambler to cause the L scrambling chips of the message to be transmitted. It is multiplied by L chips of a PN sequence. Similarly, when the deinterleaver does not exist in the receiver, the FHT units use each of the L different orthogonal (Walsh) codes to despread the de-scrambled samples (this is interleaved with the de-interleaving) The sample is reversed) and provides an energy for each code. These embodiments are well implemented under a variety of channel conditions. However, when there is a high Doppler that may be caused by a mobile transmitter and/or a mobile receiver, its performance is degraded. Doppler causes phase slopes in the input samples that can disturb the orthogonal nature of the codes, thus increasing the probability of false alarms.

The potential degradation of performance caused by high Doppler is illustrated by the data in Table 1 below.

As can be seen from the above table, if the transmitter or receiver moves at 350 km/h (km/hr), approximately 650 Hz (Hz) is observed at a carrier frequency of 2 Gigahertz (Hz). Doppler shift. If a message/Walsh code is transmitted within 0.911 microseconds (ms), there will be a full-cycle phase slope of approximately 0.6 (or 0.6 x 2π) in the input samples of the Walsh code length. For example, if the transmitted Walsh code 0 is related to the message, it can be expressed as:

Another Walsh code (eg, Walsh Code 1) can be evaluated by the receiver and can be expressed as:

When there is no Doppler, the two Walsh codes are orthogonal to each other. Applying a phase ramp to Walsh code 0 due to Doppler results in a waveform corresponding to a phase modified Walsh code 0. There will be no negligible correlation between this waveform and Walsh Code 1. This correlation results in a higher false alarm probability, for example, Walsh Code 1 is declared as the higher probability of transmitting Walsh code instead of Walsh code 0. The PN scrambling by the scrambler alone does not eliminate the problem, because both Doppler and scrambling are multiplicative. Therefore, the phase ramp will remain after the scrambling at the receiver.

In contrast, the inclusion of a code interleaver in transmitter 310/410 results in code interleaving in a pseudo-random or structured manner. In a pseudo-random interleaved embodiment, the L Walsh chips are written to L pseudo-randomly selected chip locations of a buffer and sequentially read. A pseudo-random interleaver can be obtained by implementing a thorough search to find an interleaver that provides the lowest cross-correlation in the presence of a phase slope. In an embodiment of structured interleaving, the L Walsh chips are reordered by a bit inversion interleaver. By means of the bit inversion interleaver, the L Walsh chips are written to the chip position in a buffer to obtain a position/address of a Walsh chip as an integer, and the binary representation of the integer is The bit inverted version of the binary representation of the Walsh chip order. The Walsh chips are read from the buffer in a linear order. As an example of a bit inverted interlace, a sequence of an original 8 Walsh chips can be given as [S ₀ , S ₁ , S ₂ , S ₃ , S ₄ , S ₅ , S ₆ , S ₇ ], The interleaved sequence can be given as [S ₀ , S ₄ , S ₂ , S ₆ , S ₁ , S ₅ , S ₃ , S ₇ ]. When the sequence length (L) is a power of two, a normal bit inversion interleaver can be used. Some known structured interleavers (eg, bit-inverted interlacers) may not solve this problem when associated with certain orthogonal codes (such as Walsh codes), but the pseudo-interlace (Feistel) interleaver always works. . As previously stated, regardless of the method employed, the interleaving is performed over the length of the Walsh code.

In the embodiment illustrated in Figures 3A-B and 4A-B, the code interleaving is performed prior to scrambling at the transmitter and the chip deinterleaving is performed after de-scrambling at the receiver. In other embodiments, the code interleaving is performed after scrambling at the transmitter and the chip deinterleaving is performed prior to de-scrambling at the receiver. In general, the code interleaving can be performed at any time after the Walsh mapping at the transmitter, and the chip deinterleaving can be performed at any time before the signal is processed by the FHT at the receiver.

Code interleaving and de-interlacing can be used to eliminate high Doppler and other unwanted channel effects. If a high Doppler at the receiver introduces a phase ramp into the input samples, the chip deinterleaving causes the phase ramp to be shuffled to produce a shuffle phase shift sequence. After the descrambling and chip deinterleaving, the receiver will observe a waveform corresponding to the transmitted Walsh chip multiplied by the shuffle phase shift sequence. The interlace can be designed such that the shuffled phase shift sequence looks like a pseudo-random phase error sequence. In this case, the correlation between the waveform observed by the receiver and any non-transmitted Walsh code should be quite low. Therefore, the false alarm performance will not be degraded due to the high Doppler.

Figures 3A through 4B show an embodiment of applying code interleaving using waveforms of structure codes. A structured code system has a code of a particular structure as opposed to a PN-like code (which is composed of pseudo-random chips). Some examples of structured codes include Walsh codes, OVSF codes, orthogonal codes, bi-orthogonal codes, quasi-orthogonal functions (eg, in cdma2000), multi-phase sequences with a flat envelope and flat frequency response. A structured code can operate on the data (e.g., as shown in Figures 3A and 3B) or representative data (e.g., as shown in Figures 4A and 4B). Scrambling can also be performed as described above or can be omitted. Code interleaving can be performed on waveforms that utilize structured codes in a manner other than those described above.

Figure 5A shows an embodiment of a three-stage Feistel network 500 that produces a pseudo-random arrangement of powers of size two. The Feistel network 500 can be used for the code interleaver 322 of Figure 3A and the code interleaver 422 of Figure 4A. The Feistel network 500 includes a first stage 510a, a second stage 510b, and a third stage 510c. The Feistel network 500 generates an arrangement π(x) of {0,1,2,...,.2 ⁿ -2,2 ⁿ -1} and operates as follows: 1. Divide an n-bit input x into two Parts L and R, each of which contains approximately the same number of bits. If n is an even number, then L contains n/2 most efficient bits (MSB) of x, and R contains n/2 least significant bits of x. If n is an odd number, then L contains (n-1)/2 MSBs of x, and R contains (n+1)/2 LSBs of x.

2. The output of the first stage 510a of Feistel network 500 is π ₁ (x) system form (R, L The n-bit quantity of f(R). Where f(R)=(R+S ₁ )mod 2 ^|L| , where |L| is the number of bits in L, and S ₁ is a |L| bit seed, and Represents XOR jobs on a bit by bit basis.

3. Feed the output π ₁ (x) to the second stage 510b of the Feistel network 500, which is identical to the first stage 510a except that the seed used is S ₂ . The output of the second stage 510b of the [pi] ₂ (π ₁ (x)) is fed to the third stage 510c, which in addition to the use of other than the seed S ₃ same as the previous two stages. The output π ₃ (π ₂ (π ₁ (x))) of the third stage 510c is the final output π(x) of the Feistel network 500.

Figure 5B shows a schematic diagram of an embodiment 550 of the first Feistel stage 510a, where n = 9 for this case. Stages 510b and 510c can be constructed in a manner similar to stage 410a. Figures 5A and 5B show some examples of Feistel networks. There may be other possible modifications. For example, change the number of stages in Figure 5A to 2 or 4 as an alternative to 3, or use multiplication with a prime number of another prime number, or use any other algebraic function instead of Figure 5B. "Addition of the modulus of 16" and so on.

Figure 6 shows a method 600 for reducing false alarms within the communication system in accordance with an aspect. Initially, the data to be transmitted is received at 602. At 604, the received data is extended by a channelization code that uses more bandwidth than the message signal. At 606, the chips from the sequence obtained at the time of the expansion are interleaved. As noted above, any of the pseudo-random or structured interleaving methods can be used. At 608, a PN sequence is used to scramble the interlaced bits. The PN sequence can be a combination of a short PN sequence associated with a particular base station and a long PN sequence identifying a user. At 610, the scrambled chips are further processed, for example, filtered, amplified, and broadcast.

FIG. 7 illustrates a method 700 constructed at a receiver that can receive and decode data transmitted in accordance with the method of FIG. At 702, an input processed in accordance with the method described earlier is received from a transmitter. At 704, the received input is de-scrambled by multiplying the associated PN sequence. At 706, the unscrambled input is deinterlaced. Although the deinterleaved samples may contain phase errors due to Doppler, the interleaving method described above shuffles the phase ramps on the interlaced chips, thereby mitigating false alarms at the receiver. Subsequently, the deinterlaced samples are despread. At 708, the deinterlaced samples are multiplied by a suitable channelization code, which is accumulated at 710 to obtain a despread symbol. At 712, the despread symbols thus obtained are combined for all of the receiving antennas, and the obtained symbols are provided as detection data. Thus, the method can be used to obtain detected data from interleaved input signals, and any orthogonal code can be used to extend the interleaved input signals.

Turning now to Figure 8, a method 800 of transmitting a signal is illustrated by which a false alarm introduced due to a Doppler caused by a mobile transmitter/receiver can be mitigated. At 802, a message containing K bit information is received for transmission. The message can be associated with a voice transmission, video transmission, data transmission, or a combination thereof. At 804, the K-bit message is now mapped to a specific ^2K chip Walsh code. At 806, the 2 ^K chips of the Walsh code are interleaved to produce 2 ^K interleaved chips. The interlace may be a pseudo-random interlace in which the symbols are interleaved in a pseudo-random manner to obtain information within the scheme without the knowledge of the formula originally applied to interlace the symbols. The symbols can also be interleaved in a structured manner. At 808, the interlaced chips are multiplied by a suitable PN sequence as described in detail above. At 810, the scrambled chips are further processed, for example, filtered, upconverted, and transmitted as a communication signal from an antenna (not shown).

If the Walsh code is transmitted from a mobile transmitter without interleaving, a phase ramp is introduced into the signal due to the Doppler shift. Both Doppler shift and Walsh sort are multiplication effects. Thus, if a set of vectors (eg, a structured Walsh sequence) is affected by a multiplicative Doppler shift, it becomes closed in the Euclidean space. Thus, a particular transmitted Walsh code will appear to be a different Walsh code at the receiver, thus increasing the false alarm rate. On the other hand, interleaving a Walsh sequence prior to transmission will shuffle the code bits within the sequence. Launching such shuffled sequences destroys the structure that causes false alarms. The phase error introduced into the Walsh sequence is now dispersed within the shuffled bits without causing a multiplication effect on successive chips of the Walsh sequences, which would result in a The transmitted Walsh code will appear as a different Walsh code. As explained in further detail below, after receiving, the shuffled Walsh codes are rearranged to obtain the original transmitted Walsh sequence.

Figure 9 illustrates a method 900 for obtaining a message transmitted in an interlaced Walsh sequence. At 902, the scrambled input samples and the PN sequence are received from a receiver. As described above, the signals can be received via multiple signal paths and/or one or more receive antennas. At step 904, after filtering and downconversion, the scrambled input samples are unscrambled by removing the PN code applied to the Walsh sequences. At 906, the de-scrambled Walsh codes are deinterlaced to obtain the original Walsh sequences. The Walsh sequence thus obtained may contain phase errors introduced by Doppler. However, the Walsh sequence detected at the receiver will still be the transmitted Walsh code because the phase slope is dispersed by interleaving the chips of the Walsh sequence. At 908, the commercially available FHT is used to despread the deinterlaced samples. At 910, energy is provided for each of the Walsh codes. The energy provided will typically correspond to the likelihood that the Walsh code is the transmitted code. At 912, the energy is scaled to remove noise or the like. At 914, the energy from each of the receive antennas or signals is summed for each Walsh code. At 916, the maximum energy value for each Walsh code is obtained. Alternate embodiments may omit step 914, and instead, at step 916, select a maximum energy value from the energy provided by each of the plurality of receive antenna/signal paths to each Walsh code. At 918, the energy values of all Walsh codes are compared and the Walsh code with the largest energy value is identified. At 920, the Walsh code energy value identified at 918 is compared to a threshold value. The threshold can be determined based on the criteria described above. If the energy value is greater than the threshold, then the data associated with the identified Walsh code is declared as the received information at 922, otherwise an erase is announced at 924.

The techniques described herein can be used with a variety of data and control channels. In one embodiment, the techniques are applicable to reverse link (RL) control channels that can be processed and transmitted, such as channel quality indicator channel (CQICH), request channel (REQCH), pilot channel (PICH). , acknowledge channel (ACKCH), beamforming feedback channel (BFCH), subband feedback channel (SFCH), and so on. These techniques can also be used for a time division multiplexed (TDM) pilot that is spread by channelization codes and scrambled. All channels/users (MACIDs) on the RL CDMA control segment can use the same interleaver so that an AP (access point) receiver only needs to implement one de-interlacing operation.

What has been described above includes examples of various embodiments. Of course, it is not possible to clarify every conceivable combination of components or methods for the purpose of illustrating the embodiments, but those skilled in the art will appreciate that many other combinations and permutations are possible. Accordingly, the description is intended to cover all such changes, modifications, and variations in the spirit and scope of the invention.

In particular, the various functions implemented by the above-described components, devices, circuits, systems, etc., unless otherwise indicated, the terms used to describe the components (including references to "components") are intended to correspond to any implementation. The components of the specified functions of the components (e.g., functionally equivalent components), even if they are not structurally equivalent to the disclosed exemplary embodiments of the embodiments described herein. In this regard, it should be appreciated that the embodiments include a system and a computer readable medium having computer executable instructions for performing the acts and/or events of the various methods.

In addition, although a particular feature may be disclosed with respect to only one of the various embodiments, the feature may be combined with one or more other features of other embodiments, which may be desirable and advantageous for any given or particular application. . In addition, the terms "including", "includes" and variations thereof are used in the context of the embodiments and/or claims, and the terms are intended to be expressed in a manner similar to "comprising". Contains scope.

100. . . Wireless multiple access communication system

104a. . . region

104b. . . region

104c. . . region

110. . . Base station

120. . . Terminal

130. . . System controller

200. . . MIMO system

210. . . Transmitter system

212. . . Data source

214. . . Transmit (TX) data processor

220. . . TXMIMO processor

222a. . . transmitter

222t. . . transmitter

224a. . . antenna

224t. . . antenna

230. . . processor

236. . . Data source

238. . . TX data processor

240. . . Demodulation transformer

242. . . RX data processor

250. . . Receiver system

252a. . . antenna

252r. . . antenna

254a. . . transmitter

254r. . . transmitter

260. . . RX data processor

270. . . processor

280. . . Modulator

310. . . transmitter

320. . . Channelizer/expander

322. . . Code interleaver

324. . . Scrambler

340. . . Receiver

350. . . De-scrambler

352. . . Chip deinterleaver

354. . . Decomposed channelizer/despreader

356. . . Combiner

410. . . transmitter

420. . . Walsh mapper

422. . . Code interleaver

424. . . Scrambler

440. . . Receiver

452. . . De-scrambler

454. . . Chip deinterleaver

456. . . Inverse Fast Hadamard Transform (FHT) unit

458. . . Combiner

460. . . Message selector

500. . . Three-stage Feistel network

510a. . . First level

510b. . . second level

510c. . . Third level

1 illustrates a wireless multiple access communication system in accordance with various aspects described herein.

2 is a block diagram of a communication system.

Figure 3A shows a block diagram of an embodiment of a transmitter that uses code interleaving.

Figure 3B shows a block diagram of a receiver that can be used to decode data transmitted in accordance with an aspect.

4A is a block diagram of an embodiment of a transmitter in accordance with an aspect.

Figure 4B is a block diagram of a receiver for decoding a message according to an aspect.

Figure 5A shows an embodiment of a three-stage Feistel network that produces a pseudo-random array of powers of size two.

Figure 5B shows an embodiment of a first Feistel stage 310a, where n = 9 for this case.

Figure 6 shows a method of emission according to an aspect.

Figure 7 illustrates a method of receiving a signal according to an aspect that reduces false alarms within the communication system.

Figure 8 illustrates a method of transmitting a signal by which false alarms introduced by Doppler can be mitigated.

Figure 9 is a diagram of a method of receiving and processing signals in accordance with another aspect.

(no component symbol description)

Claims (36)

An apparatus for mitigating false alarms due to incorrectly identifying Doppler time shifted data as correct data within a communication system, comprising: at least one processor configured to receive K to be transmitted to a receiver a message of one of the number of bits, mapping the message to one of a plurality of structured codes determined based on the message to obtain at least 2 ^K chips corresponding to a sequence of the message and interleaving the sequence at least prior to transmission 2 ^K chips; and a memory coupled to the at least one processor. The device of claim 1, wherein the plurality of structured codes are orthogonal codes. The device of claim 1, wherein the plurality of structured codes are Walsh codes. The device of claim 1, wherein the at least one processor constructs a Feistel network to interleave the sequence of chips in a pseudo-random manner. The device of claim 1, wherein the at least one processor spans one or more channels or users to collectively interleave the sequence of chips. The device of claim 1, wherein the at least one processor spans a length associated with each of the plurality of structured codes to interleave the sequence of chips. The device of claim 1, wherein the at least one processor scrambles the sequence of chips after interleaving. The device of claim 1, wherein the at least one processor scrambles the sequence of chips prior to interleaving. An apparatus for mitigating false alarms due to incorrectly identifying Doppler time shifted data as correct data within a communication system, comprising: at least one processor configured to receive at least one sequence transmitted from a transmitter ^K samples, deinterleaving the sequence of at least 2 ^K samples to obtain a sequence of at least 2 ^K de-interleave the samples, structured with a plurality of codes each of the despread sequence of at least two 2 ^K deinterleaved a sample, determining an energy of each of the plurality of structured codes, and providing one of the plurality of structured codes having the largest determined energy as a detected message, wherein the detected message The K number of bits is included; and the memory is coupled to the at least one processor. The device of claim 9, wherein the structured code is a Walsh code. The device of claim 9, wherein the at least one processor is configured to deinterleave the sequence of samples in at least one of a pseudo-random manner or a structured manner, the method being complementary to being implemented by the transmitter staggered. An apparatus for mitigating false alarms due to incorrectly identifying Doppler time shifted data as correct data within a communication system, comprising: a memory retaining a plurality of instructions for receiving a K to be transmitted to a receiver One of the number of bits, mapping the message to one of a plurality of structured codes determined based on the message to obtain at least 2 ^K chips corresponding to a sequence of the message and interleaving the sequence prior to transmission At least 2 ^K chips; and a processor coupled to the memory configured to execute the instructions retained in the memory. The device of claim 12, wherein mapping the message to one of the plurality of structured codes comprises mapping the message to one of a plurality of Walsh codes, wherein the structured code is a Walsh code, and wherein The serial code And wherein the structured code is a Walsh code, and wherein the sequence chip is one of the Walsh codes. The device of claim 12, wherein the sequence of interleaved chips comprises spanning a length associated with each of the plurality of structured codes to interleave the sequence of chips. An apparatus for mitigating false alarms due to incorrectly identifying Doppler time shifted data as correct data within a communication system, comprising: a memory that retains a plurality of instructions for receiving at least one sequence transmitted from a transmitter 2 ^K samples, deinterleaving the sequence of at least 2 ^K samples to obtain a sequence of at least 2 ^K de-interleave the samples to the despreading sequence of at least two 2 ^K de-structured with a plurality of codes each of Interleaving the sample, determining the energy of each of the plurality of structured codes, and providing one of the plurality of structured codes having the largest determined energy as a detected message, wherein the message comprises K a number of bits; and a processor coupled to the memory that is configured to execute the instructions retained in the memory. The apparatus of claim 15, wherein deinterlacing the sequence of samples comprises spanning a length associated with each of the plurality of structured codes to deinterlace the sequence of samples. The device of claim 15 wherein the structured code is a Walsh code. An apparatus for mitigating false alarms due to incorrectly identifying Doppler time shifted data as correct data within a communication system, comprising: means for receiving a message comprising one of K number of bits to be transmitted to a receiver Means for mapping the message to one of a plurality of structured codes for mapping the message to one of a plurality of structured codes based on the message to determine a length equal to at least 2 ^K Obtaining a sequence of at least 2 ^K chips; and means for interleaving the sequence of chips for interleaving the sequence of at least 2 ^K chips prior to transmission. The device of claim 18, wherein the means for mapping the message to one of the plurality of structured codes comprises means for mapping the message to one of a plurality of Walsh codes, wherein the structures The code is a Walsh code, and wherein the sequence chip is one of the Walsh codes. The apparatus of claim 18, wherein the means for interleaving the sequence of chips comprises means for spanning a length associated with each of the plurality of structured codes to interleave the sequence of chips. The device of claim 18, wherein the means for interleaving the sequence of chips interleaves the chips together for one or more channels or users. An apparatus for mitigating false alarms due to incorrectly identifying Doppler time shifted data as correct data within a communication system, comprising: means for receiving a sequence of at least 2 ^K samples transmitted from a transmitter; Deinterlacing the components of the sequence of chips for deinterlacing the sequence of at least 2 ^K samples to obtain a sequence of at least 2 ^K deinterleaved samples; for utilizing each of the plurality of structured codes Decomposing a component of at least 2 ^K deinterlaced samples of the sequence; means for determining energy of each of the plurality of structured codes; and for providing the plurality of plurality of determined energies One of the structured codes is a component of a detected message, wherein the detected message includes K number of bits. The device of claim 22, wherein the means for deinterlacing the sequence of chips comprises means for spanning a length associated with each of the plurality of structured codes to deinterlace the sequence of chips. The device of claim 22, wherein the structured code is a Walsh code. The apparatus of claim 22, wherein the means for deinterleaving performs a single de-interlacing operation on a plurality of channels or a plurality of users. A non-transitory computer readable medium that mitigates false alarms due to incorrectly identifying Doppler time shifted data as correct information within a communication system, the computer readable medium including a plurality of instructions when executed Having one or more processors perform the steps of: receiving a message comprising one of K number of bits to be transmitted to a receiver; mapping the message to one of a plurality of structured codes based on the message to determine Obtaining at least 2 ^K chips corresponding to a sequence of the message; and interleaving the sequence by at least 2 ^K chips prior to transmission. A non-transitory computer readable medium as claimed in claim 26, wherein the plurality of structured codes are orthogonal codes. A non-transitory computer readable medium as claimed in claim 26, wherein the plurality of structured codes are Walsh codes. A non-transitory computer readable medium of claim 26, wherein a Feistel network is used to interleave the sequence of chips in a pseudo-random manner. A non-transitory computer readable medium of claim 26, wherein the sequence of chips is interleaved across one or more channels or users. A non-transitory computer readable medium of claim 26, wherein a length of one of the plurality of structured codes is associated with each other to interleave the sequence of chips. A non-transitory computer readable medium as claimed in claim 26, further comprising scrambling the sequence of chips after interleaving. A non-transitory computer readable medium as claimed in claim 26, further comprising scrambling the sequence of chips prior to interleaving. A non-transitory computer readable medium that mitigates false alarms due to incorrectly identifying Doppler time shifted data as correct information within a communication system, the computer readable medium including a plurality of instructions when executed Having one or more processors perform the steps of: receiving at least 2 ^K samples from a transmitter transmission sequence; deinterleaving the sequence by at least 2 ^K samples to obtain at least 2 ^K deinterleaved one sequence samples; Decomposing each of the plurality of structured codes to despread at least 2 ^K of the deinterlaced sequence of samples; determining an energy of each of the plurality of structured codes; and providing the maximum determined energy One of the plurality of structured codes is used as a detected message, wherein the detected message includes K number of bits. A non-transitory computer readable medium of claim 34, wherein the structured code is a Walsh code. The non-transitory computer readable medium of claim 34, wherein the sequence of samples is deinterleaved in at least one of a pseudo-random manner or a structured manner, the method being complementary to interleaving performed by the transmitter .