BR112017027335B1 - SINGLE WORD BASED (UW) MULTIPLE ACCESS MESSAGE PROCESSING - Google Patents

Abstract

SINGLE WORD BASED MULTIPLE ACCESS MESSAGE PROCESSING (UW). A communications terminal receives a data communications signal via a random access channel. A processor searches for bursts of data in a first time slot that include one of a first set of signature sequences designated for the first time slot. When a data burst A in the first time slot includes one of the first set of signature sequences, the data burst A in the first time slot is an initial burst of a message from a first communications terminal. The processor determines whether a second time slot includes a data burst B that includes a signature sequence. When the second time slot includes data burst B, the message is a multiburst message and data burst B is a second burst of the multiburst message. When the second time slot does not include data burst B the message is a single burst message that was completed through the first time slot.

Description

BACKGROUND

[001] Multiple access schemes are employed by modern radio systems to allow multiple users to share a limited amount of bandwidth while maintaining acceptable system performance. Common multiple access schemes include Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA). System performance is also helped through error control codes. Almost all communications systems rely on some form of error control to manage errors that can occur due to noise and other factors when transmitting information over a communications channel. These communications systems may include satellite systems, fiber optic systems, cellular systems, and radio and television broadcast systems. Efficient error control schemes implemented at the transmission end of these communications systems have the capability to enable the transmission of data including audio, video, text, etc., with very low error rates within a given signal-to-ratio environment. noise (SNR). Powerful error control schemes also enable a communications system to achieve target error performance rates in very low SNR environments, such as in satellite systems and other wireless systems where noise is prevalent and high transmit power levels They are expensive, if even feasible.

[002] Interleaving Division Multiple Access (IDMA) is a multiple access technique where different users sharing the same bandwidth and time slots are separated by user-specific interleavers. As bandwidth and power become scarce to support the demands of ever-increasing transfer rates, more complex but more efficient techniques reproduce more important functions in future communications systems. IDMA is an effective technique that trades extra receiver complexity for bandwidth and power savings. On the other hand, in systems where the number of users is high and the block size is large, storing a high number of long interleavers may be undesirable. Scrambled Coded Multiple Access (SCMA) addresses this complexity by using a single shuffle sequence with different shift factors for different users without any performance penalty. With SCMA, IDMA's user-specific interleavers are replaced with user-specific scrambler sequences. Although there is no considerable performance difference between the two approaches, generation and implementation of scramble sequences are significantly simpler. In fact, the same scrambling sequence with different rotation factors can be used for different users with no impact on performance, which further reduces receiver complexity. With SCMA, therefore, all the benefits of IDMA are achieved with reduced complexity.

[003] Similar to IDMA or random waveform Code Division Multiple Access (CDMA), SCMA is a non-orthogonal multiple access technique. Although orthogonal multiple access schemes, such as Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA), are implicitly too restrictive to reach theoretical limits on fading channels, non-orthogonal CDMA, IDMA, or SCMA have the potential to reach these limits. Additionally, as discussed previously, FEC encoding is typically used to improve performance. The main difference between CDMA and SCMA is that while in CDMA different users are separated with different signature sequences with a spreading factor greater than one, in SCMA even a spreading factor of one would be sufficient to detect overlapping users based on in user-specific scrambling sequences and iterative multi-user cancellation with FEC decoding. As a result, the available bandwidth can be used for very low rate coding which gives extra SCMA coding gain that is not available in CDMA. Indeed, it is also possible to use SCMA with a scattering factor greater than one. Another benefit of SCMA's iterative receiver structure is that system performance actually improves with power variations between users, which eliminates the need for power control, an important requirement of traditional CDMA.

[004] Additionally, in conventional burst mode communication systems, a transmitter transmits burst mode signals at a certain frequency, phase and timing, which are received by a receiver through a communication channel. In conventional burst mode communication systems, it is necessary to quickly estimate various parameters of the received bursts as they arrive. These parameters include detection of the presence of a burst (onset time), frequency, initial phase, timing and amplitude. In typical burst transmission systems, a single word is used to facilitate identification of the start of a transmitted burst and determination of phase shift by the receiver. The term “Single Word” (UW) refers to a known predetermined pattern (known a priori to the receiver) that is transmitted at the beginning of each burst, whereby the receiver detects the UW and synchronizes it with the received bursts (i.e. the receiver estimates the burst parameters based on the detected UW).

[005] At the receiver, iterative multiple user detection or interference cancellation followed by decoding is performed to address maximum likelihood (ML) receiver performance without excessive complexity. However, for coded CDMA systems, even this iterative receiver can result in complicated algorithms especially when the number of users is large. Typically with CDMA, the complexity of multi-user detection or soft interference cancellation algorithms grows polynomially with the number of users/user terminals. On the other hand, similar to IDMA, SCMA serves as a simple chip-by-chip detection algorithm whose total complexity grows only linearly with the number of users. Additionally, uncoded SCMA systems perform at least as well as and usually better than uncoded CDMA, and the performance difference between the two classes of schemes grows larger for heavily loaded systems.

[006] Additionally, (as discussed in more detail below), in a large-scale shared bandwidth communications system, a number of channels may be designated as random access contention channels for terminals to send short messages . In a TDMA system, such random access contention channels typically are implemented as time slotted Aloha (S-Aloha) channels. The terminal in a TDMA-based network can use the S-Aloha contention channel to send control messages to a respective communication port to request a dedicated channel for a communications session (for example, a network browsing session). The terminal then waits for the dedicated channel assignment before beginning session data transmissions. Much more efficiently, however, SCMA can be employed for a contention channel to send short messages directly, without requesting and waiting for dedicated bandwidth assignment. Furthermore, such applications for an SCMA channel are becoming increasingly important for delay-sensitive communications that cannot provide the added latency of the dedicated bandwidth request and bandwidth assignment response. Additionally, latency reduction has become more important for network browsing applications for faster response times and improved user experience.

[007] Additionally, in relation to web browsing sessions, each web page request transmitted by the client terminal or web browser typically requires more data to be transmitted, as web pages are becoming more complex (e.g. For example, on average, a typical web page contains upwards of 30-60 objects). A typical network page request would require many SCMA bursts to complete.

[008] Although SCMA complexity only grows linearly with the number of users, however, with larger systems (e.g., having upwards of tens or hundreds of thousands of user terminals), implementations of SCMA systems can become relatively complex with each user/user terminal having a distinct scrambling signature. Additionally, with reference to applications that may require multiple SCMA bursts for a message (for example, a network page request message), receiver complexity increases the delay when processing a request like this. What is needed, therefore, is an approach to an SCMA protocol, where applications may require multiple SCMA bursts for a message, which facilitates more efficient and optimized processing at the receiver, and consequently reduces processing time.

SOME EXAMPLE METHODS

[009] Embodiments of the present invention advantageously address the requirements and needs indicated above, as well as others, by providing approaches to SCMA protocol, where applications may require multiple SCMA bursts for a message, which facilitates more efficient and optimized processing at the receiver, and consequently reduces processing time.

[010] In a large-scale shared bandwidth communications system, a SCMA multiple access approach is employed, which facilitates random access to a communications channel by a network of terminals in an efficient manner without prior coordination. Unique words are respectively assigned to individual terminals, and each terminal uses its assigned UW for each transmitted burst. On the receiving side, the receiver correlates the received signal bursts with these UWs to determine whether one or more terminals are accessing the channel and the number of terminals accessing the channel (assuming there is at least one), to identify the signature or initial vector. of scrambling that each such terminal is using to access the channel, and for synchronization (e.g., determining the timing and phase) of each individual received modulated signal for appropriate demodulation and decoding. Therefore, a receiver separates overlapping transmissions from multiple terminals on the same frequency and in the same time slot, based on a UW correlation process employed to detect UWs transmitted in parallel and thereby identify the terminals accessing the channel and subscription/ initial scrambling vector of each such terminal, and to synchronize with each individual received modulated signal for appropriate demodulation and decoding. In accordance with exemplary embodiments of the present invention, additional approaches are provided within this SCMA scheme to facilitate more efficient processing and thereby reduce processing overhead and load on the receiver with reference to the initial processing performed to detect and correlate the UWs to determine the terminals transmitting in each time slot. According to one embodiment such as this, an approach is provided that takes advantage of the fact that most backlink request messages (i.e., terminal request messages) transmitted on the SCMA contention channel require a number of consecutive SCMA bursts. Therefore, because such consecutive bursts are from the same terminal, each burst will utilize the same UW and associated signature or initial scrambling vector, and will be transmitted at essentially the same frequency and phase. If a UW is detected in a previous SCMA time slot, then the search/correlation for the particular UW can be performed in a more efficient mode for subsequent bursts, which significantly reduces the receiver's processing load.

[011] Additionally, SCMA request message bursts from terminals generally arrive in a random fashion, and typically can be modeled as Poisson arrival with an average arrival rate. According to a further embodiment, therefore, reasonably sized temporary storage may be employed on the client side of the receiver to enable the receiver to process incoming bursts at a reduced rate (e.g., at a rate relatively marginally above the rate of average arrival), rather than at the peak reception rate, which would facilitate additional processing complexity reduction. Additionally, the number of interference cancellation iterations required to achieve correct results can be significantly smaller when fewer bursts are transmitted in an SCMA time slot (i.e., because of the associated reduction in interference). Therefore, the receiver can stop processing and send the results, and start the next time slot when all bursts in the time slot are decoded correctly. Auxiliary temporary storage and early processing termination reduces the complexity of iterative interference processing significantly. According to also a further embodiment, in a network utilizing multiple SCMA carriers, an x number of SCMA receivers may be grouped together with a y number of SCMA carriers with common temporary storage to take advantage of additional statistical multiplexing between the y carriers. for additional complexity reduction.

[012] According to example embodiments, a method for communicating over a random access contention channel is provided. A data communications signal is received over a random access channel of a wireless communications network. The data communications signal is processed to search for bursts of data in a first time slot of the random access channel that include any of a first set of signature sequences designated for the first time slot, it is determined that a data burst A in the first time slot includes a first signature sequence from the first set of signature sequences designated for the first time slot, and, based on this determination, decide that data burst A in the first time slot is an initial burst of a message from a first communications terminal. The data communications signal is processed to determine whether a second slot of the random access channel (immediately following the first slot) includes a data burst B that includes the first signature sequence of the first set of signature sequences. assigned to the first time slot. In a situation where it is determined that the second time slot includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that the message from the first terminal communications terminal is a multiburst message and that data burst B is a second burst of the multiburst message from the first communications terminal. In a situation where it is determined that the second time slot does not include data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that the message from the first communications terminal is a single burst message that was completed through the first time slot.

[013] According to a further embodiment of the method, in the situation where it is determined that the second time interval includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first data interval time), the data communications signal is processed to determine whether a third random access channel time slot (immediately following the second time slot) includes a data burst C that includes the first signature sequence of the first set of sequences of signatures assigned to the first time slot. In a situation where it is determined that the third time slot includes data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that data burst C is a third burst of the multiburst message from the first communications terminal. In a situation where it is determined that the third time slot does not include data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that the multiple message bursts from the first communications terminal were completed by the second time slot.

[014] According to a further embodiment of the method, in the situation where it is determined that the third time slot includes data burst C (including the first signature sequence of the first set of signature sequences designated for the first data slot time), the data communications signal is processed to determine whether subsequent time slots of the random access channel respectively include additional data bursts each of which includes the first signature sequence of the first set of signature sequences designated for the first time interval. In a situation where it is determined that one or more such subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that each such additional data burst (each including the first signature sequence of the first set of signature sequences designated for the first time slot) is a respective subsequent burst of the message of multiple bursts from the first communications terminal. In a situation where it is determined that a time slot of such subsequent random access channel time slots does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that the multiburst message from the first communications terminal was completed by means of a time slot immediately preceding the time slot of such subsequent random access channel time slots that does not include any such burst additional data set (which includes the first signature sequence of the first set of signature sequences designated for the first time slot).

[015] According to a further embodiment of the method, it is determined that an AA data burst in the first time slot includes a second signature sequence from the first set of signature sequences designated for the first time slot, and, based on in this determination, decide that the AA data burst in the first time slot is an initial burst of a message from a second communications terminal. The data communications signal is processed to determine whether the second time slot of the random access channel includes a BB data burst that includes the second signature sequence of the first set of signature sequences designated for the first time slot. In a situation where it is determined that the second time slot includes the BB data burst (including the second signature sequence from the first set of signature sequences designated for the first time slot), it is decided that the message from the second terminal communications terminal is a multiburst message and the data burst BB is a second burst of the multiburst message from the second communications terminal. In a situation where it is determined that the second time slot does not include the BB data burst (including the first signature sequence of the first set of signature sequences designated for the first time slot), it is decided that the message of the second communications terminal is a single burst message that was completed through the first time slot.

[016] According to a further embodiment of the method, the data communications signal is processed to search for bursts of data in a future time slot of the random access channel that include any one of an additional set of data sequences. signatures designated for the future time slot, and determining that a burst of AAA data in the future time slot includes a first signature sequence from the additional set of signature sequences designated for the future time slot, and, based on this determination, deciding that the AAA data burst in the future time slot is an initial burst of a message from an additional communications terminal.

[017] According to a further embodiment of the method, the data communications signal is processed to determine whether a first subsequent time slot of the random access channel immediately following the future time slot includes a BBB data burst that includes the first signature sequence of the additional set of signature sequences designated for the future time slot. In a situation where it is determined that the first subsequent time slot of the random access channel includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), it is decided that the message from the additional communications terminal is a multiburst message and that the BBB data burst is a second burst of the multiburst message from the additional communications terminal. In a situation where it is determined that the first subsequent time slot of the random access channel does not include the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), it is decided that the message from the additional communications terminal is a single burst message that has been completed by the future time slot.

[018] According to a further embodiment of the method, in the situation where it is determined that the first subsequent time slot of the random access channel immediately following the future time slot includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), the data communications signal is processed to determine whether a second subsequent time slot of the random access channel immediately following the first subsequent time slot includes a burst of CCC data that includes the first signature sequence of the first set of signature sequences designated for the future time slot. In a situation where it is determined that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), it is decided that the CCC data burst is a third burst of the additional communications terminal multiburst message. In a situation where it is determined that the second subsequent time slot of the random access channel does not include the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), it is It is decided that the multiburst message from the additional communications terminal has been completed by the first subsequent time slot.

[019] According to a further embodiment of the method, in the situation where it is determined that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), the data communications signal is processed to determine whether additional subsequent time slots of the random access channel respectively include additional data bursts each of which includes the first signature sequence of the additional set of signature sequences assigned to the future time slot. In a situation where it is determined that one or more such additional subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the additional set of signature sequences designated for the future time slot), it is decided that each such additional data burst (each including the first signature sequence of the first set of signature sequences designated for the future time slot) is a respective subsequent burst of the multiburst message from the additional communications terminal. In a situation where it is determined that a time slot of such additional subsequent time slots of the random access channel does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot), it is decided that the multiburst message of the additional communications terminal has been completed by means of a time slot immediately preceding the time slot of such additional subsequent time slots of the random access channel that does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot).

[020] According to example embodiments, the communications terminal comprises a receiver and a processor. The receiver is configured to receive a data communications signal via a random access channel of a wireless communications network. The processor is configured to process the data communications signal to search for bursts of data in a first time slot of the random access channel that include any of a first set of signature sequences designated for the first time slot. . In a situation where the processor determines that a data burst A in the first time slot includes a first signature sequence from the first set of signature sequences designated for the first time slot, the processor is configured to decide that the data burst data A in the first time slot is an initial burst of a message from a first communications terminal. The processor is further configured to process the data communications signal to determine whether a second slot of the random access channel (immediately following the first slot) includes a B data burst that includes the first signature sequence of the first set of signature sequences assigned to the first time slot. In a situation where the processor determines that the second time slot includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the message from the first communications terminal is a multiburst message and the data burst B is a second burst of the multiburst message from the first communications terminal. In a situation where the processor determines that the second time slot does not include data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the message from the first communications terminal is a single burst message that was completed by means of the first time slot.

[021] According to a further embodiment of the communications terminal, in the situation where the processor determines that the second time slot includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is further configured to process the data communications signal to determine whether a third random access channel time slot (immediately following the second time slot) includes a data burst C that includes the first signature sequence of the first set of signature sequences assigned to the first time slot. In a situation where the processor determines that the third time slot includes data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that data burst C is a third burst of the multiburst message from the first communications terminal. In a situation where the processor determines that the third time slot does not include data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the multiburst message from the first communications terminal was completed by the second time slot.

[022] According to a further embodiment of the communications terminal, in the situation where the processor determines that the third time slot includes data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is further configured to process the data communications signal to determine whether subsequent random access channel time slots respectively include additional data bursts each including the first signature sequence of the first set of signature sequences assigned to the first time slot. In a situation where the processor determines that one or more such subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that each of such one or more subsequent time slots of the random access channel is a respective subsequent burst of the multiburst message of the first communications terminal. In a situation where the processor determines that a time slot of such subsequent random access channel time slots does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the multiburst message from the first communications terminal has been completed by means of a time slot immediately preceding the time slot of such subsequent random access channel time slots that does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the first time slot).

[023] According to a further embodiment of the communications terminal, in a situation in which the processor determines that an AA data burst in the first time slot includes a second signature sequence from the first set of signature sequences designated for the first time slot, the processor is configured to decide that the AA data burst in the first time slot is an initial burst of a message from a second communications terminal, and to process the data communications signal to determine whether the second time slot is time slot of the random access channel includes a BB data burst that includes the second signature sequence of the first set of signature sequences designated for the first time slot. In a situation where the processor determines that the second time slot includes the BB data burst (including the second signature sequence from the first set of signature sequences designated for the first time slot), the processor is configured to decide that the message from the second communications terminal is a multiburst message and the data burst BB is a second burst of the multiburst message from the second communications terminal. In a situation where the processor determines that the second time slot does not include the BB data burst (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the message from the second communications terminal is a single burst message that was completed by means of the first time slot.

[024] According to a further embodiment of the communications terminal, the processor is further configured to process the data communications signal to search for bursts of data in a future time slot of the random access channel that include any of an additional set of signature sequences designated for the future time slot, wherein, in a situation where the processor determines that a burst of AAA data in the future time slot includes a first signature sequence from the additional set of signature sequences signatures assigned to the future time slot, the processor is configured to decide that the AAA data burst in the future time slot is an initial burst of a message from an additional communications terminal.

[025] According to a further embodiment of the communications terminal, the processor is further configured to process the data communications signal to determine whether a first subsequent time slot of the random access channel immediately following the future time slot includes a BBB data burst that includes the first signature sequence of the additional set of signature sequences designated for the future time slot. In a situation where the processor determines that the first subsequent time slot of the random access channel includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), the The processor is configured to decide that the message from the additional communications terminal is a multiburst message and that the BBB data burst is a second burst of the multiburst message from the additional communications terminal. In a situation where the processor determines that the first subsequent time slot of the random access channel does not include the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), the processor is configured to decide that the message from the additional communications terminal is a single burst message that has been completed by the future time slot.

[026] According to a further embodiment of the communications terminal, in the situation where the processor determines that the first subsequent time slot of the random access channel immediately following the future time slot includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), the processor is further configured to process the data communications signal to determine whether a second subsequent time slot of the random access channel immediately following the first subsequent time slot includes a CCC data burst that includes the first signature sequence of the first set of signature sequences designated for the future time slot. In a situation where the processor determines that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), the processor is configured to decide that the CCC data burst is a third burst of the additional communications terminal's multiburst message. In a situation where the processor determines that the second subsequent time slot of the random access channel does not include the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), the processor is configured to decide that the multiburst message from the additional communications terminal has been completed by the first subsequent time slot.

[027] According to a further embodiment of the communications terminal, in the situation where the processor determines that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), the processor is further configured to process the data communications signal to determine whether additional subsequent time slots of the random access channel respectively include additional data bursts each of which includes the first signature sequence of the additional set of signature sequences designated for the future time slot. In a situation where the processor determines that one or more such additional subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the additional set of signature sequences designated for the future time slot), the processor is configured to decide that each such additional data burst (wherein each includes the first signature sequence of the first set of signature sequences designated for the future time slot) is a respective subsequent burst of the multiburst message from the additional communications terminal. In a situation where the processor determines that a time slot of such additional subsequent random access channel time slots does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot), the processor is configured to decide that the additional communications terminal multiburst message has been completed by means of a time slot immediately preceding the time slot of such additional subsequent time slots of the access channel random that does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot).

[028] Other aspects, features and advantages of the present invention will also be readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the mode considered to be best for carrying out the present invention. The present invention is also capable of other and different embodiments, and its various details may be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Therefore, the drawings and description should be considered illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[029] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the attached drawings and in which equal reference numbers refer to similar elements, and in which: figures 1A and 1B illustrate systems of communications capable of employing approaches in accordance with exemplary embodiments of the present invention; Figure 1C illustrates a block diagram representing a transmitter configured to operate in the systems of Figures 1A and 1B, in accordance with exemplary embodiments of the present invention; Figure 1D illustrates a block diagram representing a receiver configured to operate in the systems of Figures 1A and 1B, in accordance with exemplary embodiments of the present invention; Figure 1E illustrates, for example, the frame format of a physical layer frame, for example according to the DVB S2 frame structure channel coding and modulation systems standard; Figure 2A illustrates a block diagram representing a multiple transmitter system using a SCMA scheme, in accordance with exemplary embodiments of the present invention; Figure 2B illustrates a flowchart representing a shuffling process of the system of Figure 2A, in accordance with exemplary embodiments of the present invention; Figure 3 illustrates a block diagram of a parallel single-word (UWs) correlator of a complex receiver sampling scheme for QPSK modulation, in accordance with exemplary embodiments of the present invention; Figure 4 illustrates a block diagram representing a series of group burst transmissions within respective time slots, where a group of single words (UWs) is divided into 4 sets, and each UW is associated with one of the time slots in module 4 (as identified by a respective filling pattern), in accordance with exemplary embodiments of the present invention; Figure 5 illustrates a bar graph representing the relative frequency of simultaneous transmission occurrence with an average Poisson arrival rate of 4, in a total of 50,000 SCMA burst transmissions, in accordance with example embodiments of the present invention; Figure 6 illustrates a block diagram depicting temporary input storage(s) implemented in front of the SCMA receiver processor to allow the receiver to decode more difficult time slots, in accordance with example embodiments hereof. invention; Figure 7 illustrates simulation results showing the size of an auxiliary buffer required for an SCMA decoding/interference cancellation mechanism as a function of the processing capacity of the mechanism, in accordance with example embodiments of the present invention; and Figure 8 illustrates simulation results showing the time series of the number of SCMA bursts queued in auxiliary temporary storage, with 15 SCMA carriers as an input, and 5 SCMA interference cancellation mechanisms serving the queue, in accordance with example embodiments of the present invention; and Figure 9 illustrates a block diagram representing a receiver with inputs of 16 SCMA carriers processed by 6 SCMA interference cancellation mechanisms employed after auxiliary temporary storage, in accordance with example embodiments of the present invention.

DETAILED DESCRIPTION

[030] Approaches to a SCMA Scrambled Coded Multiple Access protocol, where applications may require multiple SCMA bursts for a message, which facilitates more efficient and optimized processing at the receiver, and consequently reduces processing time, are described. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a complete understanding of the invention. It is clear, however, that the invention can be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form to avoid unnecessarily obscuring the invention.

[031] As will be understood, a module or component (as referred to in this document) may be composed of software component(s), which is(are) stored in a memory or on other computer-readable storage media, and executed by one or more processors or CPUs of the respective devices. However, as will also be understood, a module may alternatively be composed of hardware component(s) or firmware component(s), or a combination of hardware, firmware and/or software components. Additionally, with respect to the various example embodiments described herein, although certain functions are described as being performed by certain components or modules (or combinations thereof), such descriptions are provided as examples and thus are not intended to be limiting. Therefore, any such functions may be considered to be performed by other components or modules (or combinations thereof), without departing from the general spirit and scope of the present invention. Additionally, the methods, processes, and approaches described herein may be implemented per processor using processing circuitry that may comprise one or more microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other operable devices to be configured or programmed to implement the systems and/or methods described herein. For implementation in such devices that are operable to execute software instructions, the flowcharts and methods described herein may be implemented in processor instructions stored on a computer-readable medium, such as executable software stored in a computer memory store.

[032] Additionally, terminology referring to computer-readable media or computer media or the like, as used herein, refers to any media that participates in providing instructions to a computer's processor or processor module or component for execution . Such media can take many forms, including, but not limited to, non-volatile media and non-transient volatile media. Non-volatile media include, for example, optical disk media, magnetic disk media, or electrical disk media (e.g., solid-state disk or SDD). Volatile media include dynamic memory, such as random access memory or RAM. Common forms of computer-readable media include, for example, floppy disk, hard disk, magnetic tape, any other magnetic media, CD ROM, CDRW, DVD, any other optical media, random access memory (RAM), read-only memory programmable memory (PROM), erasable PROM, flash EPROM, any other memory chip or cartridge, or any other media from which a computer can read data.

[033] Figures 1A, 1B, 1C illustrate communications systems capable of employing approaches in accordance with various example embodiments of the present invention. 1A, a broadband communications system 110 includes one or more transmitters 112 (of which one is shown) that generate signal waveforms for transmission to one or more receivers 116 (of which one is shown). . The signal waveforms are transmitted over a communications channel 114, which (for example) may comprise a channel of a terrestrial, terrestrial wireless or satellite communications system. In this discrete communications system 110, the transmitter 112 has a signal source that produces a distinct set of data signals, where each of the data signals is transmitted in a corresponding signal waveform. The distinct set of data signals may first be encoded (e.g., via a forward error correction code) to combat noise and other problems associated with channel 114. Once encoded, the encoded signals may then be modulated. on a carrier for transmission on channel 114. Signal waveforms are attenuated, or otherwise altered, by communications channel 114.

[034] Figure 1B illustrates an example satellite communications system 130 capable of supporting communications between terminals with varying capabilities, according to example embodiments. The satellite communications system 130 includes a satellite 132 that supports communications between multiple satellite terminals (STs) 134a-134n, multiple communications ports (GWs) 138a-138n, and a network operations center (NOC) 142 The STs, GWs and NOC transmit and receive signals through antennas 136a-136n, 146a-146n and 156, respectively. According to different embodiments, the NOC 142 may reside at a separate location reachable via a separate satellite channel or may reside at a GW location. The NOC 142 performs the management plane functions of the system 130, while the GWs 138a-138n perform the data plane functions of the system 130. For example, the NOC 142 performs functions such as network management and configuration, data transfers, software (e.g. for STs 134a-134n), status monitoring, statistical functions (e.g. collection, aggregation and reporting), security functions (e.g. key generation, management and distribution), registration and authentication of ST and diversity management of GW. The NOC 142 communicates with each GW via the satellite 132, or via a secure private communications network 152 (e.g., an IPsec tunnel over a dedicated link or a virtual private network (VPN) or IPsec tunnel through of a public network, such as the Internet). It should be noted that, according to an example embodiment, the traffic classification approaches of embodiments of the present invention address classification of data traffic flowing through an aggregation point or node. Additionally, each GW and the NOC has connectivity to one or more public communications networks, such as the Internet or a PSTN.

[035] According to a further example embodiment, each of the GWs 138a-138n includes one or more IP communication ports (IPGWs) - whereby data plane functions are divided between a GW and its respective IPGWs. For example, GW 138a includes IPGWs 148a(1)-148a(n) and GW 138n includes IPGWs 148n(1)-148n(n). A GW can perform functions such as link-layer and physical-layer output route coding and modulation (e.g., DVB-S2 adaptive coding and modulation), link-layer and physical-layer input route handling (e.g., example, IPOS), bandwidth allocation and inbound route load balancing, outbound route prioritization, network acceleration and HTTP compression, flow control, encryption, redundancy changes, and traffic restriction policy enforcement. Therefore, an inbound route manager or inbound route group manager (IGM) (not shown) can be located on each of the communication ports. The IGM can be configured to control bandwidth allocations to remote endpoints (e.g., on an inbound route group or inbound route group basis), and to correspondingly control and manage bandwidth allocation approaches. band provided in accordance with exemplary embodiments of the present invention. Additionally, as would be appreciated, in certain embodiments, the IGM may be implemented in a distributed mode, with a master controller in the NOC 142, whereby the NOC may be configured to administer system-wide controls for such bandwidth allocation approaches. band, whereas inbound route-based controls would be administered for specific inbound routes/inbound route groups by the IGM on the respective communications port controlling such inbound routes/inbound route groups. Various other architectures can also be provided to satisfy different system design objectives and requirements.

[036] The IPGW can perform functions such as data compression, TCP performance enhancements (e.g., TCP performance enhancement proxies, such as TCP deceiver), quality of service functions (e.g., classification, prioritization, differentiation, Random early detection (RED), TCP/UDP flow control), bandwidth usage policing, dynamic load balancing and routing. Additionally, a GW and respective IPGW may be co-located with the NOC 142. The STs 134a-134n provide connectivity to one or more hosts 144a-144n and/or routers 154a-154n, respectively. The satellite communications system 130 may operate as a curved channel system, where the satellite essentially operates as a repeater or curved channel. Alternatively, system 130 may employ a switching or processing satellite supporting mesh communications (point-to-point communications directly between, for example, the two STs 134a and 134n).

[037] In a curved channel system of an example embodiment, satellite 132 operates as a repeater or curved channel, and communications to and from STs 134a-134n are transmitted by satellite 132 to and from respective IPGWs associated with particular STs. Additionally, in a spot beam system, any spot beam operates as a curved channel for the geographic region covered by the beam. For example, each spot beam operates as a curved channel communications channel to and from the STs and/or IPGW(s) within the geographic region covered by the beam. Therefore, signal transmissions to the satellite are from an ST and destined for an associated communication port, or from a communication port and destined for an associated ST. According to one embodiment, multiple GWs/IPGWs are distributed throughout the geographic region covered by all spot beams of satellite 132, where, in a beam in which a GW and respective IPGWs are located, only one GW (and no ST) occupies this beam. Additionally, each IPGW can serve as an aggregation node for a multiplicity of remote nodes or STs. The total number of GWs/IPGWs and the geographic distribution of the GWs/IPGWs depend on several factors, such as the total capacity of the dedicated satellite for data traffic, geographic traffic loading of the system (e.g., based on population densities and the geographical distribution of STs), locations of available terrestrial data centers (e.g. terrestrial data trunks for access to public and private dedicated networks).

[038] Figure 1C illustrates a block diagram representing a transmitter configured to operate in the systems of figures 1A and 1B, according to example embodiments of the present invention. Referring to Figure 1C, a transmitter 112 is equipped with a channel encoder (e.g., a turbo encoder or low density parity check code (LDPC) encoder) 111 that accepts input from an information source and outputs higher redundancy coded stream suitable for error correction processing at the receiver. The information source generates k signals from a distinct alphabet . For example, turbo codes are produced through parallel concatenation of two codes (e.g., convolutional codes) with an interleaver between the encoders. A low-density parity check code (LDPC) is a linear error correction code, constructed using a sparse bipartite graph. Any linear code has a bipartite graph and a parity check matrix representation, but not all linear codes have a sparse representation. An n x m matrix is sparse if the number of 1's in any row (the row weight wr) and the number of 1's in any column (the column weight wc) are much less than their dimension (i.e., wr « m, wc « n). A code represented by a sparse parity check matrix is called a low-density parity check code (LDPC). Essentially, the encoder 111 generates the coded signals/symbols from the Y alphabet, and the channel scrambler 113 scrambles the alphabet (e.g., the channel scrambler pseudorandomizes the code symbols). The scrambled signals are fed to a modulator 115, which maps the encoded messages from the encoder 111 to signal waveforms that are routed to a transmit antenna 117. The antenna 117 outputs these waveforms over the communication channel 114. Transmissions from the transmit antenna then propagate to a receiver, as discussed below.

[039] Figure 1D illustrates a block diagram representing a receiver configured to operate in the systems of figures 1A and 1B, according to example embodiments of the present invention. On the receiving side, a receiver 116 includes an antenna 121 that receives waveforms emitted on channel 114 by transmitter 112. Receiver 116 provides a demodulator 123 that performs demodulation of the received signals. After demodulation, the received signals are routed to a channel unscrambler 125, which unscrambles the demodulated symbols. A decoder 127 then attempts to reconstruct the original source messages.

[040] It is considered that the transmitter 112 and receiver 116 shown above can be implemented in a single wireless terminal, in which case a common antenna system can be shared. The wireless terminal, for example, can be configured to operate within a satellite communication, cellular system, wireless local area network (WLAN), etc.

[041] Figure 2A illustrates a block diagram representing a system with multiple transmitters using a SCMA scheme, in accordance with example embodiments of the present invention, and Figure 2B illustrates a flowchart representing a scrambling process of the system of Figure 2A, according to exemplary embodiments of the present invention. For the purpose of illustration, a communication system 200 supports multiple transmission terminals (i.e., users) 112a-112n, each configured with a respective encoder 201a-201n and scrambler 203a-203n.

[042] According to example embodiments, system 200 provides a SCMA multiple access scheme, which achieves good performance with relatively lower receiver complexity when compared to CDMA (as the number of users sharing the same channel increases) . With SCMA, each user sharing the transmission channel is separated by means of the user-specific initial scrambling sequence or vector used by the respective scramblers 203a-203n. According to one embodiment, by using low rate codes (e.g., low rate turbo codes or low rate LDPC codes), system 200 achieves greater power efficiency while spreading the spectrum, whereas conventional CDMA does not. By way of example, each of the 201a-201n encoders uses the same error correction codes. The encoded sequences are then provided to respective user/terminal specific scramblers 203a-203n. The scrambled sequences are then transmitted via channel 114 to a receiver 116. Additionally, SCMA is different from the IDMA multiple access technique, which also scatters with low-rate turbo-Hadamard codes, but uses random interleavers to allow for signatures of different users. With such SCMA implementations, low-rate decoders are much more straightforward to implement, and all users can utilize the same scrambler hardware, each using a distinct initial vector or seed to provide a distinct terminal scramble signature. Additionally, using shuffle sequences as signatures is simpler than signatures based on random interleavers.

[043] By way of example, each terminal encodes its data with, for example, an FEC code rate of 1/n, where n is an integer greater than 3. The encoded bits are then scrambled with a unique scramble sequence and transmitted. The number of unique sequences is virtually unlimited with common sequence generators such as Golden sequences. Alternatively, the same generator can generate all sequences, which are differentiated for each terminal by using a different initial vector or seed. Additionally, other low m/n ratios can be used (e.g., less than 1/3). By way of further example, the shuffle sequence can be generated by selecting a sequence of pseudorandom numbers (e.g., a Golden sequence) whose period is greater than the code block. On the receiving side, the receiving terminal uses the corresponding unscrambler and a 1/n rate decoder to recover the data. The signals are modulated by the same type of modulation, for example QPSK, of the same bandwidth, centered on the same frequency and transmitted at the same time (e.g. similar to CDMA). Additionally, for receivers located in a hub of a star-shaped network, the antennas can be shared. As mentioned, use of scramblers (as opposed to interleavers) reduces complexity. In a large system with numerous users, it is difficult to implement a large number of interleavers that are pre-arranged between each sender and receiver pair, whereas a common scrambler with a different initial vector (also known as a “seed”) can be used to each pair of emitter and receiver. Such an arrangement is substantially easier to implement.

[044] According to a further embodiment, the receiver includes a junction detector/interference cancellation unit 207 that interacts with decoders 213a-213n to iteratively produce an estimate of the received codewords. With each iteration, the decoder 213a-213n produces a better estimate for the junction detector/interference canceller unit 207 to achieve better cancellation. The information exchanged between the decoders 213a-213n and the junction detector/interference canceller unit 207 is scrambled or unscrambled by means of the scramblers 209a-209n or the unscramblers 211a-211n, respectively. Once “good” estimates of the decoded sequences are produced, they are produced by decoders 213a-213n. Unlike conventional CDMA systems, the junction detector/interference canceller unit 207 does not require that all signals accessing the same spectrum at the same time have the same power. In fact, performance is better when the signals have different power levels. Therefore, strict power controls are not necessary. Also, because of junction detection/interference cancellation, system 200 provides a scheme that is much more robust against Rician fading, which makes it particularly more attractive for small mobile terminals experiencing multipath Rician fading.

[045] With reference to Figure 2B, according to example embodiments, the SCMA system 200 can operate as follows. In step 221, each terminal encodes data using the corresponding encoder (e.g., respective encoders 201a-201n). Each terminal then scrambles the encoded data via its respective scrambler (e.g., respective scrambler 203a-203n), and transmits the encoded and scrambled data via channel 114 to receiver 116, in steps 223 and 225. At receiver 116, the The received signal is processed by the junction detector/interference canceller 207, and is then subjected to an iterative unscrambling and rescrambling process in step 227. The unscrambling and rescrambling are performed in combination with the decoding process, which produces decoded data (step 229).

[046] According to such example embodiments, such as a SCMA system using low-rate FEC coding, system 200 requires less power to transmit data at the same speed compared to a CDMA system. In one embodiment, the system 200 can be operated in a random access mode and does not require time slot reservation, which minimizes the delay for a satellite round trip. Additionally, as mentioned previously, system 200 does not require strict power control, minimizing the coordination required between transmitters 112 and receiver 116.

[047] Additionally, in a time division multiple access (TDMA) system, for example, several communications terminals can share the same communications channel (e.g., a common frequency). In the TDMA system, the signal transmitted through the channel is separated into different time slots, where each communications terminal transmits using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a portion of their channel capacity. At the physical layer, data is configured in the form of data frames. Figure 1E illustrates, for example, the frame format of a physical layer frame 131, for example, according to the DVB S2 frame structure channel coding and modulation systems standard. Each frame 131 generally comprises a header 133 and a data payload 135. The header is attached to the data payload for purposes such as, for example, synchronization, demodulation and decoding at the receiver. The data payload comprises the encoded (and in the case of SCMA, scrambled) source data sequence. The header includes a start-of-frame (SOF) or single-word (UW) segment 137 and a physical layer signaling field 139. The PLS field reflects certain modes considering, for example, the modulation and coding schemes applied to the data. The UW provides a mechanism for the receiver (e.g., receiver 116) to synchronize across frame boundaries, and consequently locate the data payload within each frame. The data payload includes the data and information intended to be received and processed by the destination receiver. By way of example, the receiver receives the transmitted signal, which comprises a series of physical layer data frames. Additionally, the receiver has a priori knowledge of the UW sequence(s) used by the respective transmission terminal(s). The receiver can then search for the respective UW(s) when performing a correlation operation. Once a threshold has been satisfied for the correlation operation, the receiver determines a start time for the first symbol of the respective UW. Based on the start time determined for the initial UW symbol, the receiver has thus also determined the initial reception time or start of the respective physical layer data frame. The receiver can then synchronize and process the symbols of the respective data payload based on the determined initial reception time or start of the respective physical layer data frame.

[048] In a large-scale shared-bandwidth communications system, several channels may be designated as random access containment channels for terminals to send short messages, such as control messages - that is, to establish a network communication session. private data or to provide bandwidth requests to a resource allocation manager located on a respective Communication Port. A random access contention channel like this can be implemented as a time-slotted Aloha channel (S-Aloha). Aloha is a communications network protocol, which can be implemented in two different versions or protocols depending on whether or not global synchronization is required. Aloha Puro does not require global synchronization. The basic idea of Aloha Puro is that a terminal is allowed to transmit data on the channel whenever the terminal has data to send. The transmission terminal monitors feedback and is thus able to detect when its transmitted data collides with data transmitted by another terminal in the same time interval. If a collision is detected, the transmit terminal will wait for a random or predetermined period of time and then attempt transmission again. The waiting period for each terminal is randomized such that the same transmissions are not delayed for the same amount of time and so the same collision does not occur repeatedly. In contrast, Time-Slotted Aloha or S-Aloha requires global time synchronization. Based on synchronization, the S-ALOHA protocol divides time into distinct intervals and each interval corresponds to a time interval for transmitting a data frame (where all terminals are synchronized with respect to the time interval limits). In contrast to Pure Aloha, the S-Aloha protocol does not allow a terminal to transmit at any time, but instead requires the terminal to wait for the start of the next transmission time slot. When a terminal has data to send, therefore, it must wait for the start of the next time slot before transmitting the data. With the S-Aloha protocol, although collisions can still occur, the frequency of collisions is reduced based on transmission only occurring at the beginning of a time slot.

[049] The main difference between SCMA and S-Aloha is that the SCMA scheme allows multiple terminals to transmit data in the same time slot (where data transmitted from each terminal is distinguished based on a distinct scrambling signature), whereas the S-Aloha scheme only allows data from a single terminal to be transmitted in a respective time slot (otherwise a collision occurs and the data cannot be received correctly by a receiver). More specifically, according to one embodiment, where a common scrambler is used in a SCMA scheme, the data transmitted by each terminal is scrambled through different segments of a sequence of pseudorandom numbers from that same scrambler, where each segment is generated based on into a distinct initial vector (or seed). Shuffling the data encoded by each terminal based on a distinct initial vector results in a distinct signature by which data transmitted by multiple terminals in a common time interval can be distinguished based on that signature.

[050] In a large-scale system, however, where the number of terminals reaches relatively large numbers (e.g., tens or even hundreds of thousands of terminals), traditional SCMA schemes may become impractical, or even relatively impossible. For example, in a traditional SCMA system like this with a relatively large number of terminals, when multiple terminals transmit in a single time slot, the receiver will have no way of knowing which terminals are transmitting in which time slot. The receiver could synchronize on a single word indicating that data was transmitted within a respective time interval, but would then have to operate in cycles or search all possible scrambling signatures or initial vectors of scrambling signatures to determine which terminals transmitted the data. . Therefore, with such a large number of terminals, such decoding would become very complex and time-consuming, and would therefore be impractical for a system like this.

[051] According to example embodiments, therefore, an approach is provided that enables scaling of traditional SCMA schemes to such large-scale systems. According to such an embodiment, a single word (UW) of sufficient length is associated with each of the signatures or initial scrambling vectors, wherein each terminal is designated with a UW and associated signature or initial scrambling vector. When transmitting data, each terminal scrambles the encoded data symbols using the designated signature or initial scrambling vector and appends the respective UW as part of the header of each transmitted packet. At the receiving end, upon detecting the presence of one or more UWs within a respective time interval, the receiver determines that one or more respective messages or data bursts were transmitted within that time interval, where each such data burst has been scrambled based on the signature or initial scrambling vector associated with the respective UW. Then, the receiver can proceed with processing each of the received data bursts based on the respective signature or initial scrambling vector associated with the UW of that data burst.

[052] With reference to the implementation of the SCMA protocol, embodiments of the present invention can be applied to the scenario where each terminal uses a unique signature or scrambling sequence to scramble the encoded symbols of data transmitted by the terminal, or to the scenario where each terminal uses the same shuffling signature with a unique initial or seed vector to scramble the encoded symbols of data transmitted by the terminal. In case each terminal uses a unique scrambling signature, each UW designated in accordance with example embodiments is associated with a respective scrambling signature, and in case each terminal uses the same scrambling signature with a unique starting vector, each UW designated according to example embodiments is associated with a respective initial vector. Therefore, although the following embodiments of description are in the context of the SCMA scenario where each terminal uses a common scrambling signature with a unique starting vector, those skilled in the art will recognize that such embodiments can also be applied to the SCMA scenario where each terminal uses a unique shuffle signature.

[053] With this embodiment, each terminal is assigned a distinct UW and associated initial scrambling vector, each user can be given a separate UW, and thus the terminal can be uniquely identified based on the identification of its UW and the respective unique initial vector can be used to decode/unscramble your messages. Because a large-scale shared bandwidth satellite or beam satellite network potentially has many thousands of users, designation of a distinct UW for each such terminal would be impractical in terms of the UW correlation process required at the receiver. More specifically, in practice, although only a limited number of the terminals may have data to transmit at any given time, at the beginning of each burst or time slot, the receiver would still have to search or correlate based on all of the terminals' UWs (including most terminals that did not transmit any data in that given time). Therefore, such receivers would require very complex processing on the client side, which would be impractical and expensive to implement.

[054] According to additional example embodiments, therefore, SCMA approaches are provided that take advantage of the fact that, in practice, only a relatively small number of terminals will require access to the random access contention channel at the same time. According to such an embodiment, a relatively small number of UWs are assigned to a respective number of terminal groups. The universe of implemented terminals is grouped across terminal groups, and each terminal in a terminal group is assigned the UW and initial vector or scrambling signature associated with that group. Therefore, because only a relatively small number of terminals can be accessing the contention channel in the same time slot, the probability of two or more users using the same UW within that time slot is relatively low. By way of example, a few hundred groups of terminals and respective UWs can be employed to divide a universe of many thousands of terminals (e.g., tens or even hundreds of thousands) by a factor that reduces the probability of burst collisions within a time interval for a minimum level of impact to system performance.

[055] Within the context of such example embodiments, an SCMA receiver correlates multiple UWs with the received signal to determine whether one or more terminals have data transmitted over the channel, and (if so) the number of terminals accessing the channel at each time interval, to determine the initial scrambling sequence or vector that each such terminal is using to scramble its data as part of the SCMA protocol, and to determine the timing and phase of the respective modulated signals from each such terminal in order to facilitate demodulation and decoding the respective data bursts.

[056] Figure 3 illustrates a block diagram of a parallel single-word correlator of a complex receiver sampling scheme for QPSK modulation, in accordance with example embodiments of the present invention. Two samples are used to represent a modulation symbol. In one sampling clock cycle, the correlator will shift in an incoming sample, and correlate (one at a time) with all n possible UWs, each p bits wide. With reference to Figure 4, UWi reflects the UW of order i in the receiver table (the UW in the table indexed by index i), which can be expressed by its real and imaginary components as RUWi and IUWi, respectively (UWi = [ RUWi, IUWi]). Additionally, real and imaginary components can be represented in binary format, as follows: In this binary format, a 0 means a “+1” and a multiplication by 0 means “passing through”. Similarly, a 1 means a “-1”, and multiplication by 1 means “2’s complement”. All n UWs in the table programmed or stored in the receiver must be cycled within the one sample duration. Alternatively, in the case where the universe of UWs is separated into subsets or groups (e.g., applied on a beam-by-beam basis, as described previously), then a given receiver need only cycle through all the UWs of its respective group. Similarly, cycling through a respective group must also be completed within a sample duration. The correlation result or interpolated correlation peak output is compared with an adjustable detection threshold. The threshold value is determined through a classic trade-off between probability of detecting error and false alarm. Once a UW passes the threshold, its index is marked and the UW and associated initial vector or scrambling seed are used by the receiver for further decoding and unscrambling of the respective data signal.

[057] Additionally, the correlation results can be used to estimate the initial phase of the particular burst, and the correlator output can be used to estimate the power level of the burst. Additionally, the peak of the correlator value, together with the value adjacent to the peak, can be used to estimate the timing of the burst onset. All these burst parameter values can also be used by the receiver for further decoding and unscrambling of the respective data signal. The same general approach is applicable for Offset QPSK (OQPSK) modulated signals. Because OQPSK shifts the imaginary part of the signal by half a symbol before it is transmitted, the lower half of the correlator in Figure 3 would thus pick up complex sample inputs by the same half-symbol shift. In other words, it would take inputs coming from a later element, rather than being equal to the top half of the correlator. The various algorithms that can be employed to estimate these burst parameter values are beyond the scope of embodiments of the present invention, as they would be readily known to those skilled in the art - and thus are not discussed herein.

[058] As discussed previously, according to example embodiments, SCMA can be employed as a resource to send short messages directly over a random access containment channel, without requiring the designation of dedicated channel bandwidth. Such SCMA applications are becoming increasingly important with the increasing implementation and use of delay-sensitive applications that cannot tolerate the added latency associated with the process of acquiring such dedicated channel bandwidth. For example, latency reduction has become more important for network browsing applications in order to provide an improved user experience. In relation to web browsing, each web page request transmitted by the client terminal or web browser typically requires more data to be transmitted, as web pages have become more complex. For example, on average, a typical web page contains over 30-60 objects, and each object request, on average, requires over 500 bytes of data. Additionally, typically at less than 120 bytes per SCMA burst (for example), the request for each object would require more than 4 SCMA bursts. When the request is not encrypted the problem can be somewhat mitigated through pre-recovery, as the communication port can anticipate the objects to be requested if the title page of the request is known. With increasing percentages of network sites employing secure connections (e.g., HUPS), however, pre-recovery becomes impractical (if not impossible) for such sites. Furthermore, messages on an SCMA contention channel for other applications may similarly incur several successive SCMA bursts for the complete message. For example, with a typical Internet Protocol (IP) packet, once encoded via its FEC code, the resulting information and parity bits would require several SCMA bursts to carry the entire IP packet information. Additionally, a single message may even consist of multiple IP packets, which would multiply the number of resulting SCMA bursts for the entire message.

[059] On the receiving side, with the UW approaches to SCMA (discussed previously), the SCMA receiver becomes significantly more complicated when compared to a SCMA receiver that does not employ such UW approaches or to a flat TDMA receiver. With a larger message that requires multiple SCMA bursts for transmission, the message is divided into multiple bursts that are transmitted sequentially on the contention channel. Each burst in this mode is transmitted independently with the respective UW, and is thus received and processed independently by the receiver. Therefore, at the receiver, the receiver is required to detect and correlate the UW for each such burst, which requires cycling through all possible UWs for each burst. Furthermore, the most computationally intensive part of SCMA burst processing at the receiver consists of performing a search for all possible UWs expected within each symbol timing interval within the opening of a time slot. Additionally, with each request for an object having more than 4 SCMA bursts on average (as outlined previously), each successive request by the terminal for an object on this network page would incur an additional 8 SCMA bursts. As a result, for each individual request message from the transmitting terminal to an additional network page object, the receiver must repeat the same initial UW processing for each burst of each request. This results in a significant level of initial processing for each request message (consisting of the sequential transmission of several SCMA bursts by the requesting terminal) received over the SCMA contention channel.

[060] In order to reduce the complexity and processing load on the receiver with reference to such sequential message bursts, therefore, example embodiments of the present invention provide approaches that take advantage of the fact that, where a contention channel message requires a sequence of multiple SCMA bursts to complete the transmission (from the same transmitter), each burst will use the same UW. Also, each of the SCMA bursts from the same terminal must have the same time offset from the time slot boundary, since SCMA bursts are transmitted consecutively time slot by time slot. According to example embodiment approaches, therefore, based on the known burst position from time slot to time slot, the processing required for each burst can be reduced, which in turn reduces UW lookup processing.

[061] Such approaches reduce the initial UW processing loads of the receiver, according to one embodiment, by partitioning the terminals using an SCMA contention channel into two groups. One group consists of terminals newly accessing the SCMA channel, and the other group consists of terminals continuing a previous SCMA channel access. By way of example, to separate the new incoming population from the continuing access population, different sets of UW patterns are used at successive time intervals. New input terminals can be modeled as the arrival rate of a stochastic process, and continuing access terminals represent the duration of arrivals. The product of the arrival and its duration reflects the traffic load that the SCMA channel is designed to handle. In other words, the new arrival rate reflects the rate of new arrivals, and the duration of access continuing for each terminal reflects the duration of these total terminal transmissions after the respective new arrival. Therefore, the total load is the number of new arrivals times the duration of continued access of each such new arrival. Since the collision probability decreases proportionally with the arrival rate, to maintain a constant collision probability, the number of UWs can decrease proportionally with the decrease in the arrival rate.

[062] In other words, by way of example, a distinct set of UWs is assigned to each time slot, and a terminal beginning a transmission in a particular time slot chooses a UW from the set of UWs assigned to that time slot. . Then, for successive transmissions through the same terminal, the terminal uses the same UW. Then, for each time slot, the receiver searches for new starter terminals by searching only UWs from the set of UWs designated for that time slot, and confirms that continued transmissions from previous starters are present in the successive time slot. The terminal keeps track of UWs from previous beginners, and once a time interval occurs without a UW from a beginner from the previous beginners tracked, the receiver assumes that the respective terminal has completed its message transmission or contention channel access and removes this UW from the tracked list. Each set contains a sufficient number of UW patterns to reduce the collision probability to a desirable rate as dictated by the expected arrival rate of user traffic. By way of further example, the number of UW groups for new entrants would be a fixed number n, and the sequence of UW group assignments for respective time slots would be repeated every n time slots. In other words, each set of UWs is available or assigned in a continuous time sequence for each time slot that occurs at an equivalent successive time offset starting at a reference point or synchronization point in the timing of a transmission sequence. of a given channel. With reference to potential new entrants (new terminals accessing the SCMA channel), as part of the initial UW processing for each time slot, the receiver performs a search within the time slot for all possible UWs from only the new set of UWs of novices assigned to the respective time slot, along with a search for the particular UW of continued successive burst transmissions from each terminal that accessed the SCMA channel in a previous time slot (which is based on a list of UWs being tracked from such previous beginners).

[063] For example, if a terminal 1 wished to begin a group burst transmission at time slot 0, then the terminal would select a UW from the group of UWs assigned to time slot 0 and continue the group burst for intervals of successive times using the same UW. Similarly, if another terminal 2 also wished to begin a group burst transmission at time slot 0, then the terminal would ideally select a different UW from the group of UWs assigned to time slot 0 and continue the burst. group for successive time intervals using the same UW. If another terminal 3 wished to begin a group burst transmission in time slot 1, then the terminal would select a UW from the group of UWs assigned to time slot 1 and continue the group burst for successive time slots using the same UW. For this example, it is assumed that in time slot 0, the receiver is not tracking any previous upstart UWs from the previous time slots. At time slot 0, the receiver would perform initial UW processing by searching all UWs assigned to time slot 0 to detect any new starting terminals in that time slot, and detect UWs from transmissions from terminals 1 and 2. Then , in time slot 1, the receiver would perform initial UW processing by searching all UWs assigned to time slot 1 to detect any new starting terminals in that time slot, and would detect the UW of terminal 3's transmission. the receiver would be keeping track of UWs from previous entrants (in this case, the UWs used by terminals 1 and 2, respectively, in time slot 0), and thus, in time slot 1, the receiver would also perform a relatively simple determination of that the UWs of terminals 1 and 2 are also present in time slot 1 (indicating continued GB transmission from each terminal). This determination would consist of a search for the UW of terminal 1 and the UW of terminal 2 in time slot 1, at the same respective relative displacements within the time slot as that of time slot 0. Since the receiver determines that a Previous UW being tracked for a continued transmission from a terminal is not present within a time interval, the receiver assumes that the respective GB of that terminal has been completed and accordingly removes the respective UW from the list of previous UWs being tracked from previous starting terminals.

[064] With the example cited above, however, because there is no coordination between terminals, there is no guarantee that each of two terminals transmitting within the same burst or SCMA time slot will choose a different UW from the group of UWs designated for this time interval. According to example embodiments, therefore, approaches are employed to lessen the possibility that two such terminals would choose the same UW for a transmission in a common SCMA time slot. According to such an embodiment, terminal 1 would randomly select a UW from the group of UWs assigned to time slot 0 for its burst transmissions in time slot 0 and successive time slots. Similarly, terminal 2 would also randomly select the UW for its burst transmissions in time slot 0 and in successive time slots from the group of UWs assigned to time slot 0. By way of example, at the time the terminal 1 wanted to access the containment channel in the respective time slot (time slot 0 in this example), the terminal would generate a random number of n modules and use the generated random number as an index into a table of the UWs assigned to that slot of time (where n equals the number of UWs assigned to the time slot). Similarly, the moment terminal 2 wanted to access the contention channel in the respective time slot (again, time slot 0 in this example), that terminal would also generate a random number of n modules and use the random number generated as an index into a table of the UWs assigned to that time range. Therefore, with an example embodiment like this, the distribution of UWs and terminal groups is randomized and continuously changing, whose dynamic randomization should contribute to reduced probability of collisions. However, it should be noted that because the n modules are a many-to-one mapping, the probability that two terminals can use the same UW at the same time within the same time slot is still a non-zero probability.

[065] To realize additional computation reduction, according to a further embodiment, the terminals can be separated into n groups, and the SCMA time slots would be numbered into n modules. Then, a terminal in the group of order k would be allowed to begin a message burst transmission only in a time slot numbered k n modules, and would continue for each time slot until completing its message transmission. According to preliminary simulation analysis, with n = 8 and a total group of > 255 UWs, the number of clock cycles required to process an SCMA carrier can be distributed equally, thus doubling the number of channels that can be processed by the same receiver. The size of n, however, reflects a trade-off between probability of collisions, which is determined by the number of UWs usable by a group of terminals, and the complexity of reducing computation. As an example, based on analysis, 4 < n < 16 appears to be a practical choice.

[066] Figure 4 illustrates a block diagram representing a series of group burst transmissions within respective time slots, where a group of single words (UWs) is divided into 4 sets, and each UW is associated with one of the time intervals in the 4 modules (as identified by means of a respective filling pattern), in accordance with exemplary embodiments of the present invention. Therefore, Figure 4 shows an example for n = 4. The time slots are divided into 4 groups, each with a distinct filling pattern, and each filling pattern is associated with a respective set or group of UWs. In other words (as mentioned previously), each set of UWs is available or assigned in a continuous time sequence for each time interval that occurs at an equivalent successive time offset starting at a reference point or synchronization point in the synchronization of a transmission sequence on a given channel. With reference to Figure 4, the UWs associated with the time slot 0 filling pattern would be available or assigned to time slots occurring at time 0, time 4x, time 8x, time 12x, 16x..., and the UWs associated with the time slot 1 filling pattern would be available or assigned to time slots occurring at time x, time 5x, time 9x, time 13x, ... (where x is the length of a time slot). A request consists of a variable length of SCMA bursts, each of which is called a “Group Burst” or GB (for example, GB 0, GB 1, GB 11 shown in Figure 4). For example, a group burst may reflect an HTTP or HTTPS request from a particular endpoint, transmitted in successive SCMA bursts over a contention channel. A GB that starts in one of the standard time slots will continue for different time slots, and there may be different GBs that start in the same time slot. Each GB from a different endpoint that starts at a particular time slot will use a randomly selected UW from the group of UWs for that time slot. The UW detector will look for the UW associated with that particular group, plus those previously detected GBs to confirm the continuation of the GBs. If a UW from the previous time slot is no longer detected in the current time slot, the receiver assumes that the GB is complete, and it is removed from the list of UWs that it needs to track in the next time slot. Each group burst initially transmitted in a time slot uses one UW from the respective group, and continues to use the same UW for the GB's remaining SCMA bursts.

[067] For example, with reference to Figure 4, each of the terminals transmitting GB 0 and GB 4 is designated to begin a GB transmission in a designated time slot with the group of UWs designated by the time slot filling pattern. 0, 4, 8, 12, 16, ... . Similarly, each of the terminals transmitting GB 3, GB6, GB 11 is designated to begin a GB transmission in a designated time slot with the group of UWs designated by the filling pattern of time slots 3, 7, 11, 15, ... . As shown in the figure, GB 0 and GB 4 start at time slot 0, GB 1 starts at time slot 2, GB 2 starts at time slot 1, and GB 3 starts at time slot 3 At time slot 0, the receiver performs a search for all UWs associated with the filling pattern of time slot 0, and detects the UW of the initial burst of GB 0 and the UW of the initial burst of GB 4. The receiver. may then decode the initial burst of GB 0 based on the signature or initial scrambling vector associated with the detected UW of GB 0, and may decode the initial burst of GB 4 based on the signature or initial scrambling vector associated with the detected UW of GB 4. Then, in time slot 1, the receiver performs a search of all UWs associated with the filling pattern of time slot 1, and detects the UW of the initial burst of GB 2. In time slot 1, The receiver also performs a search of the UW of GB 0 and the UW of GB 4 to determine that a successive burst from each of GB 0 and GB 4 is contained within time slot 1. Then, in time slot 2 , the receiver performs a search for all UWs associated with the filling pattern of time slot 2, and detects the UW of the initial burst of GB 1. In time slot 2, the receiver also performs a search for the UW of GB 0 , the UW of GB 4, and the UW of GB 2 to determine that a successive burst from each of GB 0, GB 4, and GB 2 is contained within time interval 2. Later in the sequence, in the time 7, the receiver detects that a burst with the UW of GB 0 is not contained within this time interval. The receiver assumes as soon as GB 0 has been completed and stops searching for the respective UW at successive time intervals (except if the receiver searches for that same UW within the next time interval for which the respective group of UWs is assigned). The process continues in a similar fashion until time slot 16 and the detection of the successive burst from groups 5 to 11.

[068] According to additional example embodiments, various approaches are provided for reducing the probability of data burst collisions. According to an embodiment like this, the terminals can be separated into groups, where each group would be allowed to begin a GB transmission only at certain time intervals. In other words, each group is associated with a respective group of UWs (or each terminal in a particular group is allowed to begin a GB message transmission only in a time slot associated with a respective group of UWs). A scheme like this, however, reduces each terminal's access to the respective contention channel and thereby increases latency by forcing the terminal to wait for a designated time interval to access the channel and transmit its data. This latency, however, is introduced only at the beginning of a respective GB transmission, because once the terminal accesses the SCMA channel in the respective time slot, the terminal continues this GB transmission in successive time slots. By way of example, a fixed designation of a group of UWs can be established for each terminal. For example, the designation can be fixed as a function of n modules of the manufacturing serial number, where n represents the number of groups of UWs. According to another such embodiment, the system may be configured whereby all terminals may select a UW and scrambling signature or initial scrambling vector from the available or designated group of UWs for the time slot at the time the terminal begins to GB transmission. Therefore, with this approach, each terminal would have to store the UWs and respective seeds for each of the groups of UWs.

[069] According to additional example embodiments, speed advantages can be achieved through earlier termination and statistical multiplexing. Within each time slot, the number of simultaneous transmissions is a random variable. The power received from each transmission terminal is also a random variable, within some limits. As a result, some transmitted bursts can be demodulated and decoded without error sooner and some bursts will take a longer time for decoding and demodulation. In particular, the detection and demodulation process is much easier if the number of simultaneous transmissions in a time interval is relatively small; whereas it can spend a significantly larger amount of time when the number of simultaneous transmissions is relatively large. Typically, packet arrival rates can be modeled as a Poisson distribution. Even with different packet lengths (typically modeled as an exponential distribution), the number of simultaneous transmissions in each time slot is still a Poisson distribution. Figure 5 illustrates a bar graph representing the relative frequency of occurrence of simultaneous transmissions with an average Poisson arrival rate of 4, in a total of 50,000 SCMA burst transmissions, in accordance with example embodiments of the present invention.

[070] According to one embodiment, for a single channel, receiver complexity can be reduced by including an auxiliary buffer with early termination. Figure 6 illustrates a block diagram depicting temporary input storage(s) implemented in front of the SCMA receiver processor to allow the receiver to decode more difficult time slots, in accordance with example embodiments of the present invention. invention. Temporary storage would be implemented between the channel downconverter and SCMA receiver processor, as illustrated in Figure 6. The auxiliary temporary storage is sized to be sufficient to store a fixed number of SCMA time slots x (in raw samples ). Since the receiver processor may spend varying processing time to fully decode each burst, auxiliary buffering ensures that input samples from the next x sample-worthy time intervals are not lost when the SCMA receiver is going slow. When a particularly difficult-to-decode time interval is completed, the processor can recover to work off the queued samples in auxiliary temporary storage. In other words, because the decoding process depends on the number of bursts received and the difficulty in decoding each such burst (e.g., based on a number of iterations required for interference cancellation, and the use of early termination of processing decoding iteration), processing is statistically variable. Auxiliary temporary storage facilitates smoothing out of decoding processing and Rx SCMA processor workload, which increases the processing speed and efficiency of the Rx SCMA processor.

[071] By way of example, the SCMA contention channel uses a powerful early error correction coding, such as a Low Density Parity Check (LDPC) code. In a case like this, when all the parity check equations of the LDPC code are satisfied, the burst can be considered to be decoded correctly. Additionally, the coding may also include a Cyclic Redundancy Check (CRC) code with the information portions of a burst. The decoded burst would therefore be considered correct if CRC checks are correct. Either mechanism provides the receiver with a mechanism for terminating iteration early in the decoding process. Therefore, once all simultaneous transmissions of a timeslot are successfully decoded, the receiver stops further interference cancellation iterations, outputs the results, and begins processing the next SCMA timeslot. In this mode, the receiver may be sized for slightly above average load rather than maximum load. Part of the gain in peak load versus average load is provided by the nature of random arrival. Additionally, the number of interference cancellation iterations required to achieve correct results may be significantly smaller when fewer bursts are transmitted in an SCMA time slot, because of significantly less interference. The receiver can stop processing, produce results, and start the next time slot when it believes that all bursts in the time slot are decoded correctly. Auxiliary temporary storage and early termination significantly reduce the complexity of iterative interference processing.

[072] Figure 7 illustrates simulation results showing the size of an auxiliary temporary storage required for an SCMA decoding/interference cancellation mechanism as a function of the processing capacity of the mechanism, in accordance with example embodiments of the present invention. The size of the auxiliary buffer is designed to offload the SCMA receiver's processing load. Figure 7 shows the number of auxiliary buffers required for an SCMA decoding/interference cancellation mechanism as a function of the processing capacity of the mechanism. The processing capacity increased from 2 Msps to 6 Msps as the temporary storage size increased from 2 SCMA time slots to 10 SCMA time slots. At a nominal SCMA operating point, larger auxiliary buffering reduces receiver idle time. For a given receiver implementation, greater processing power equals reduced complexity on average.

[073] According to an additional embodiment, for greater efficiency, the average auxiliary temporary storage size can be further reduced by employing statistical multiplexing between a large number of SCMA carriers. Figure 8 illustrates simulation results showing the time series of the number of SCMA bursts queued in auxiliary temporary storage, with 15 SCMA carriers as an input, and 5 SCMA interference cancellation mechanisms serving the queue, in accordance with example embodiments of the present invention. Referring to Figure 8, a total of 50 time slots worthy of auxiliary temporary storage were shared by 15 SCMA carriers, each operating at 2 Msps, for a total processing capacity of 30 Msps. They are handled by 5 SCMA interference cancellation mechanisms, each operating at 6 Msps. As shown, the staging queue length typically is 2 SCMA timeslots, but at some points it peaks above 35 SCMA timeslots, but the queue rarely grows beyond 20 SCMA timeslots. As is evident, with additional multiplexing between carriers and multiple interference cancellation mechanisms, a highly efficient receiver implementation is achieved. Figure 9 illustrates a block diagram representing a receiver with inputs of 16 SCMA carriers processed by 6 SCMA interference cancellation mechanisms employed after auxiliary temporary storage, in accordance with example embodiments of the present invention.

[074] The term “computer-readable media” as used herein refers to any media that participates in providing instructions to the processor 403 for execution. Media such as this can take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media include, for example, optical or magnetic disks, such as storage device 409. Volatile media may include dynamic memory, such as main memory 405. Common forms of computer-readable media include, for example, a floppy disk , a hard disk, magnetic tape, any other magnetic media, a CD ROM, CDRW, DVD, any other optical media, RAM, PROM, and EPROM, FLASH EPROM, any other memory chip or cartridge, or any other media that a computer can read.

[075] Various forms of computer-readable media may be involved in providing instructions to a processor for execution. For example, instructions for carrying out at least part of the present invention may initially be recorded on a magnetic disk of a remote computer. In a scenario like this, the remote computer loads the instructions into main memory and sends the instructions over a telephone line using a modem. A local computer system modem receives data over the telephone line and uses an infrared transmitter to convert the data into an infrared signal and transmit the infrared signal to a portable computing device, such as a personal digital assistant (PDA) and a laptop. An infrared detector in the portable computing device receives the information and instructions carried by the infrared signal and places the data on a bus. The bus transports data to main memory, from which a processor retrieves and executes instructions. Instructions received by main memory may optionally be stored in a storage device before or after execution by the processor.

[076] Although exemplary embodiments of the present invention may allow for various implementations (e.g., including hardware, firmware and/or software components), and, unless otherwise noted, all functions are performed by a CPU or a processor executing computer-executable program code stored on a non-transitory memory or computer-readable storage medium, the various components may be implemented in different configurations of hardware, firmware, software and/or a combination thereof. Except as otherwise disclosed herein, the various components shown in outline or block form in the figures are well known individually and their internal construction and operation are not critical to the construction or use of this invention or to a description of the best same way.

[077] In the preceding specification, various embodiments were described with reference to the attached drawings. However, it will be evident that various modifications can be made to this, and additional embodiments can be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings, therefore, are to be considered in an illustrative rather than a restrictive sense.

Claims (16)

1. Method, CHARACTERIZED by the fact that it comprises: receiving a data communications signal through a random access channel of a wireless communications network; process the data communications signal to search for bursts of data in a first time slot of the random access channel that include any of a first set of signature sequences designated for the first time slot, and determining that a data burst A in the first time slot includes a first signature sequence from the first set of signature sequences designated for the first time slot, and, based on this determination, decide that data burst A in the first time slot is an initial burst of a message from a first communications terminal; process the data communications signal to determine whether a second slot of the random access channel (immediately following the first slot) includes a data burst B that includes the first signature sequence of the first set of designated signature sequences for the first time interval; and in a situation where it is determined that the second time slot includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), deciding that the message from the first terminal communications terminal is a multi-burst message and data burst B is a second burst of the multi-burst message from the first communications terminal; and in a situation where it is determined that the second time slot does not include data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), deciding that the message of the first communications terminal is a single burst message that was completed through the first time slot. 2. Method according to claim 1, CHARACTERIZED by the fact that, in the situation in which it is determined that the second time interval includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), further comprises: processing the data communications signal to determine whether a third random access channel time slot (immediately following the second time slot) includes a data burst C that includes the first signature sequence of the first set of signature sequences designated for the first time slot; and in a situation where it is determined that the third time slot includes data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), deciding that data burst C is a third burst of the multiburst message from the first communications terminal; and in a situation where it is determined that the third time slot does not include the data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), decide that the multiple message bursts from the first communications terminal were completed by the second time slot. 3. Method, according to claim 2, CHARACTERIZED by the fact that, in the situation in which it is determined that the third time interval includes the data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), further comprises: processing the data communications signal to determine whether subsequent random access channel time slots respectively include additional data bursts each including the first signature sequence of the first set of sequences of signatures assigned to the first time slot; and in a situation wherein it is determined that one or more such subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the first set of signature sequences designated for the first time slot), decide that each such additional data burst (wherein each includes the first signature sequence of the first set of signature sequences designated for the first time slot) is a respective subsequent burst of the message of multiple bursts from the first communications terminal; and in a situation where it is determined that a time slot of such subsequent random access channel time slots does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the first time slot), decide that the multiburst message from the first communications terminal has been completed by means of a time slot immediately preceding the time slot of such subsequent random access channel time slots that does not include any such burst additional data set (which includes the first signature sequence of the first set of signature sequences designated for the first time slot). 4. Method according to claim 1, CHARACTERIZED by the fact that it further comprises: determining that an AA data burst in the first time slot includes a second signature sequence from the first set of signature sequences designated for the first time slot time, and, based on this determination, deciding that the AA data burst in the first time slot is an initial burst of a message from a second communications terminal; processing the data communications signal to determine whether the second time slot of the random access channel includes a BB data burst that includes the second signature sequence of the first set of signature sequences designated for the first time slot; and in a situation where it is determined that the second time slot includes the BB data burst (including the second signature sequence of the first set of signature sequences designated for the first time slot), deciding that the message from the second terminal communications terminal is a multi-burst message and the data burst BB is a second burst of the multi-burst message from the second communications terminal; and in a situation where it is determined that the second time slot does not include the BB data burst (including the first signature sequence of the first set of signature sequences designated for the first time slot), deciding that the message of the second communications terminal is a single burst message that was completed through the first time slot. 5. Method according to claim 1, CHARACTERIZED by the fact that it further comprises: processing the data communications signal to search for bursts of data in a future time slot of the random access channel that include any of an additional set of signature sequences designated for the future time slot, and determining that an AAA data burst in the future time slot includes a first signature sequence from the additional set of signature sequences designated for the future time slot, and , based on this determination, decide that the AAA data burst in the future time slot is an initial burst of a message from an additional communications terminal. 6. Method according to claim 5, CHARACTERIZED by the fact that it further comprises: processing the data communications signal to determine whether a first subsequent time slot of the random access channel immediately following the future time slot includes a burst of BBB data that includes the first signature sequence of the additional set of signature sequences designated for the future time slot; and in a situation where it is determined that the first subsequent time slot of the random access channel includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), decide that the message from the additional communications terminal is a multiburst message and that the BBB data burst is a second burst of the multiburst message from the additional communications terminal; and in a situation where it is determined that the first subsequent time slot of the random access channel does not include the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), deciding that the message from the additional communications terminal is a single burst message that has been completed by the future time slot. 7. Method according to claim 6, CHARACTERIZED by the fact that, in the situation wherein it is determined that the first subsequent time slot of the random access channel immediately following the future time slot includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), further comprises: processing the data communications signal to determine whether a second subsequent time slot of the random access channel immediately following the first slot subsequent time slot includes a CCC data burst that includes the first signature sequence of the first set of signature sequences designated for the future time slot; and in a situation where it is determined that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), decide that the CCC data burst is a third burst of the additional communications terminal multiburst message; and in a situation where it is determined that the second subsequent time slot of the random access channel does not include the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), deciding that the multiburst message from the additional communications terminal has been completed by the first subsequent time slot. 8. Method according to claim 7, CHARACTERIZED by the fact that, in the situation where it is determined that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), further comprises: processing the data communications signal to determine whether additional subsequent time slots of the random access channel respectively include additional data bursts each of which includes the first signature sequence of the additional set of signature sequences designated for the future time slot; and in a situation wherein it is determined that one or more such additional subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the additional set of signature sequences designated for the future time slot), decide that each such additional data burst (each including the first signature sequence of the first set of signature sequences designated for the future time slot) is a respective subsequent burst of the multi-burst message from additional communications terminal; and in a situation wherein it is determined that a time slot of such additional subsequent time slots of the random access channel does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot), decide that the additional communications terminal multiburst message has been completed by means of a time slot immediately preceding the time slot of such additional subsequent random access channel time slots that does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot). 9. Communications terminal, CHARACTERIZED by the fact that it comprises: a receiver configured to receive a data communications signal through a random access channel of a wireless communications network; and a processor configured to process the data communications signal to search for bursts of data in a first time slot of the random access channel that include any one of a first set of signature sequences designated for the first time slot. , wherein, in a situation where the processor determines that a burst of data A in the first time slot includes a first signature sequence from the first set of signature sequences designated for the first time slot, the processor is configured to decide that data burst A in the first time slot is an initial burst of a message from a first communications terminal; and wherein the processor is further configured to process the data communications signal to determine whether a second time slot of the random access channel (immediately following the first time slot) includes a data burst B that includes the first data sequence. signing the first set of signature sequences designated for the first time slot; and in a situation where the processor determines that the second time slot includes data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the message from the first communications terminal is a multiburst message and that data burst B is a second burst of the multiburst message from the first communications terminal; and in a situation where the processor determines that the second time slot does not include data burst B (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to deciding that the message from the first communications terminal is a single burst message that was completed through the first time slot. 10. Communications terminal, according to claim 9, CHARACTERIZED by the fact that, in the situation in which the processor determines that the second time interval includes data burst B (including the first signature sequence of the first set of sequences of signatures designated for the first time slot), the processor is further configured to: process the data communications signal to determine whether a third random access channel time slot (immediately following the second time slot) includes a burst of data C that includes the first signature sequence of the first set of signature sequences designated for the first time slot; and in a situation where the processor determines that the third time slot includes data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that data burst C is a third burst of the multiburst message from the first communications terminal; and in a situation where the processor determines that the third time slot does not include data burst C (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to deciding that the multiburst message from the first communications terminal has been completed by the second time slot. 11. Communications terminal, according to claim 10, CHARACTERIZED by the fact that, in the situation in which the processor determines that the third time interval includes the data burst C (including the first signature sequence of the first set of sequences of signatures designated for the first time slot), the processor is further configured to: process the data communications signal to determine whether subsequent random access channel time slots respectively include additional data bursts each of which includes the first signature sequence of the first set of signature sequences designated for the first time slot; and in a situation wherein the processor determines that one or more such subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that each of such one or more subsequent time slots of the random access channel is a respective subsequent burst of the multiburst message of the first communications terminal; and in a situation where the processor determines that a time slot of such subsequent random access channel time slots does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the multiburst message from the first communications terminal has been completed by means of a time slot immediately preceding the time slot of such subsequent random access channel time slots. which does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the first time slot). 12. Communications terminal, according to claim 9, CHARACTERIZED by the fact that, in a situation in which the processor determines that an AA data burst in the first time slot includes a second signature sequence from the first set of signature sequences signatures assigned to the first time slot, the processor is configured to: decide that the AA data burst in the first time slot is an initial burst of a message from a second communications terminal; and processing the data communications signal to determine whether the second time slot of the random access channel includes a BB data burst that includes the second signature sequence of the first set of signature sequences designated for the first time slot; and in a situation where the processor determines that the second time slot includes the BB data burst (including the second signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to decide that the message from the second communications terminal is a multiburst message and the data burst BB is a second burst of the multiburst message from the second communications terminal; and in a situation where the processor determines that the second time slot does not include the BB data burst (including the first signature sequence of the first set of signature sequences designated for the first time slot), the processor is configured to deciding that the message from the second communications terminal is a single burst message that was completed through the first time slot. 13. Communications terminal according to claim 9, CHARACTERIZED by the fact that the processor is further configured to: process the data communications signal to search for data bursts in a future access channel time slot random that include any one of a further set of signature sequences designated for the future time slot, wherein, in a situation where the processor determines that a burst of AAA data in the future time slot includes a first signature sequence of the additional set of signature sequences designated for the future time slot, the processor is configured to decide that the AAA data burst in the future time slot is an initial burst of a message from an additional communications terminal. 14. Communications terminal according to claim 13, CHARACTERIZED by the fact that the processor is further configured to: process the data communications signal to determine whether a first subsequent time slot of the random access channel immediately following the future time slot includes a BBB data burst that includes the first signature sequence of the additional set of signature sequences designated for the future time slot; and in a situation where the processor determines that the first subsequent time slot of the random access channel includes the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot), the processor is configured to decide that the message from the additional communications terminal is a multiburst message and that the BBB data burst is a second burst of the multiburst message from the additional communications terminal; and in a situation where the processor determines that the first subsequent time slot of the random access channel does not include the BBB data burst (including the first signature sequence of the additional set of signature sequences designated for the future time slot) , the processor is configured to decide that the message from the additional communications terminal is a single burst message that has been completed by the future time slot. 15. Communications terminal, according to claim 14, CHARACTERIZED by the fact that, in the situation in which the processor determines that the first subsequent time slot of the random access channel immediately following the future time slot includes the data burst BBB (including the first signature sequence of the additional set of signature sequences designated for the future time slot), the processor is further configured to: process the data communications signal to determine whether a subsequent second time slot of the random access immediately following the first subsequent time slot includes a CCC data burst that includes the first signature sequence of the first set of signature sequences designated for the future time slot; and in a situation where the processor determines that the second subsequent time slot of the random access channel includes the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot), the processor is configured to decide that the CCC data burst is a third burst of the multiburst message from the additional communications terminal; and in a situation where the processor determines that the second subsequent time slot of the random access channel does not include the CCC data burst (including the first signature sequence of the first set of signature sequences designated for the future time slot) , the processor is configured to decide that the multiburst message from the additional communications terminal has been completed by the first subsequent time slot. 16. Communications terminal according to claim 15, CHARACTERIZED by the fact that, in the situation in which the processor determines that the second subsequent time slot of the random access channel includes the CCC data burst (including the first sequence of signature of the first set of signature sequences designated for the future time slot), the processor is further configured to: process the data communications signal to determine whether additional subsequent time slots of the random access channel respectively include additional data bursts wherein each includes the first signature sequence of the additional set of signature sequences designated for the future time slot; and in a situation wherein the processor determines that one or more such additional subsequent time slots of the random access channel respectively include such additional data bursts (wherein each includes the first signature sequence of the additional set of signature sequences designated for the future time slot), the processor is configured to decide that each of such additional data bursts (wherein each includes the first signature sequence of the first set of signature sequences designated for the future time slot) is a respective subsequent burst of the multiburst message from the additional communications terminal; and in a situation where the processor determines that a time slot of such additional subsequent time slots of the random access channel does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot), the processor is configured to decide that the additional communications terminal multiburst message has been completed by means of a time slot immediately preceding the time slot of such additional subsequent time slots of the communications channel. random access that does not include any such additional data burst (which includes the first signature sequence of the first set of signature sequences designated for the future time slot).