Enhanced RACH (Random Access Channel) Design for 5G CIOT (Cellular Internet of Things)

Abstract

Techniques for random access (RA) in a cellular internet of things (CIOT) are discussed. An example apparatus configured for use in a user equipment (UE) includes a receiver circuit, a processor, and a transmitter circuit. The receiver circuit is configured to receive RA resource allocation information via one of a system information message or a downlink control information (DCI) message. The processor is operably coupled to the receiver circuit and is configured to: select an RA preamble sequence; generate a payload; and spread the payload via a spreading sequence. The transmitter circuit is configured to send an RA message including an RA preamble sequence and a payload based on the RA resource allocation information, wherein the RA message is sent in an RA time slot. The receiver circuit is further configured to receive a response including one of an uplink (UL) grant or RA rejection message and a device identity of the UE.

Description

[0001] Citation of Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 197,471, filed on July 27, 2015, entitled “Enhanced RACH Design for Clean State CIOT Systems,” the contents of which are incorporated herein by reference in their entirety.

[0003] This application is a divisional application of the invention patent application with the international application date of December 17, 2015, the international application number of PCT / US2015 / 066340, the national application number of CN201580082029.1, and the invention name of “Enhanced RACH (Random Access Channel) Design for 5GCIOT (Cellular Internet of Things)”. Technical Field

[0004] The present disclosure relates to wireless technologies, and more particularly to a random access channel (RACH) design for 5G (fifth generation) clean state cellular Internet of Things (5G-CIoT). Background Art

[0005] The random access (RA) process in a wireless system is generally used to extract the time and frequency (phase) information of the uplink (UL) transmission for UL time synchronization and initial frequency correction, and to initiate a network login process for a mobile device (e.g., UE (User Equipment)). In the GERAN (GSM (Global System for Mobile Communications) EDGE (Enhanced Data Rates for GSM Evolution) Radio Access Network) Clean State Cellular Internet of Things (CS-CIoT) research project, 3GPP (3rd Generation Partnership Project) TR (Technical Report) 45.820, the radio access network features are target features being developed, such as low cost, a large number of devices, very long device battery life, and delay-tolerant small packets. An additional important target feature of this network is a 20dB coverage extension for devices deployed deep in buildings or underground spaces. For UL, the CS-CIoT device first establishes a connection with the base station. It is important to complete the RA process for initiating this connection. The traditional RA process for CS-CIoT specified in 3GPP TR45.820 is based on slotted ALOHA type access. For this access mechanism, RA channel (RACH) resources are evenly distributed in superframes in the time domain and different UL channels in the frequency domain. The device obtains the location of RA resources by reading the system information message for contention-based RA or the downlink control information (DCI) for non-contention-based RA. These devices are then divided into different coverage categories based on their link quality. Finally, different RA resources are allocated across different coverage categories. System information (SI-2) carries the MCS (modulation and coding scheme) level, UL PCId (physical channel identity), and RACH index. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a block diagram illustrating an example user equipment (UE) that can be used in conjunction with various aspects described herein.

[0007] Figure 2 is a block diagram of a system that can be used in a UE to assist in communicating RA (random access) messages over a RACH (RA channel) in a CS (Clean State)-CIoT (Cellular Internet of Things) wireless system in accordance with various aspects described herein.

[0008] Figure 3 is a block diagram of a system that may be used in an enhanced Node B (eNB) or other base station to facilitate communication with one or more UEs over a RACH in a CS-CIoT wireless system in accordance with various aspects described herein.

[0009] Figure 4 is a flow chart illustrating a method for facilitating RA message communication over a RACH in a CS-CIoT wireless system in accordance with various aspects described herein.

[0010] Figure 5 is a flow chart illustrating a method for facilitating communication with one or more UEs via a RACH in a CS-CIoT wireless system in accordance with various aspects described herein.

[0011] Figure 6 is a diagram illustrating an example structure of an RA message with a guard band in accordance with various aspects described herein.

[0012] Figure 7 is a diagram illustrating a second example structure of an RA message with a guard band and dummy bits according to various aspects described herein. DETAILED DESCRIPTION

[0013] The present disclosure will now be described with reference to the accompanying drawings, wherein, throughout the present disclosure, similar reference numerals are used to refer to similar elements, and the structures and devices shown are not necessarily drawn to scale. As used herein, the terms "component", "system", "interface", etc. are used to refer to computer-related entities, hardware, software (e.g., in execution), and / or firmware. For example, a component can be a processor (e.g., a microprocessor, a controller, or other processing devices), a process running on the processor, a controller, an object, an executable instruction, a program, a storage device, a computer, a tablet PC, and / or a user device (e.g., a mobile phone, etc.) with a processing device. For example, an application and a server running on a server can also be a component. One or more components can reside in a process, and a component can be located on a computer and / or distributed between two or more computers. A group of elements or a group of other components can be described here, wherein the term "group" can be understood as "one or more".

[0014] In addition, these components can be executed by various computer-readable storage media (e.g., modules) having various data structures stored thereon. Components can communicate through local and / or remote processes, for example, based on signals having one or more data packets (e.g., data from another component in a local system, a distributed system, and / or across a network (e.g., the Internet, a local area network, a wide area network, or the like, or a component that interacts with other systems through signals)).

[0015] As another example, a component may be a device having mechanical parts provided with specific functionality by electrical or electronic circuitry operated by software applications or firmware applications executed by one or more processors. The one or more processors may be internal or external to the device and may execute at least a portion of the software or firmware application. As yet another example, a component may be a device that provides specific functionality by electronic components without mechanical parts; the electronic components may include one or more processors in which software and / or firmware that at least partially imparts functionality to the electronic components is executed.

[0016] The use of the word "exemplary" is used to give a concept in a specific way. The term "or" as used in this application is used to express an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or it is clear from the context, "X adopts A or B" refers to any natural inclusive replacement. That is, if X adopts A; X adopts B; or X adopts both A and B; then "X adopts A or B" satisfies any of the aforementioned examples. In addition, the articles "one" and "an" used in this application and the appended claims should be generally understood to mean "one or more" unless otherwise specified or it is clear from the context to point to a singular form. In addition, to a certain extent, the terms "include", "comprise", "have", "contain", "combined with" and their variations are used in the detailed description and claims, and these terms represent an inclusive meaning similar to the term "include".

[0017] As used herein, the term "circuit" may refer to or include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, group), and / or a memory (shared, dedicated, group), a combinational logic circuit, and / or other appropriate hardware components that provide the described functionality, or a portion thereof, that executes one or more software or firmware programs. In some embodiments, the circuit may be implemented in one or more software or firmware modules, or the functionality associated with the circuit may be implemented by one or more software or firmware modules. In some embodiments, the circuit may include logic that is at least partially operable in hardware.

[0018] The embodiments described herein may be implemented as a system using any suitably configured hardware and / or software. Figure 1 Example components of a user equipment (UE) device 100 of one embodiment are shown. In some embodiments, the UE device 100 may include application circuitry 102, baseband circuitry 104, radio frequency (RF) circuitry 106, front end module (FEM) circuitry 108, and one or more antennas 110 coupled together at least as shown.

[0019] The application circuitry 102 may include one or more application processors. For example, the application circuitry 102 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The one or more processors may include any combination of general-purpose processors and special-purpose processors (e.g., graphics processors, application processors, etc.). The processor may be coupled to and / or may include a memory / storage device, and may be configured to execute instructions stored in the memory / storage device to enable various applications and / or operating systems to run on the system.

[0020] The baseband circuit 104 may include circuits such as, but not limited to, one or more single-core or multi-core processors. The baseband circuit 104 may include one or more baseband processors and / or control logic for processing baseband signals received from the receive signal path of the RF circuit 106 and generating baseband signals for the transmit signal path of the RF circuit 106. The baseband processing circuit 104 may interface with the application circuit 102 for baseband signal generation and processing and for controlling the operation of the RF circuit 106. For example, in some embodiments, the baseband circuit 104 may include a second generation (2G) baseband processor 104a, a third generation (3G) baseband processor 104b, a fourth generation (4G) baseband processor 104c, and / or one or more baseband processors 104d for other existing generations, generations under development or generations to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuit 104 (e.g., one or more of the baseband processors 104a-d) may manipulate various radio control functions that enable communication with one or more radio networks through the RF circuit 106. The radio control functions may include, but are not limited to, signal modulation / demodulation, encoding / decoding, radio frequency shifting, etc. In some embodiments, the modulation / demodulation circuitry of the baseband circuitry 104 may include fast Fourier transform (FFT), precoding, and / or constellation mapping / demapping functions. In some embodiments, the encoding / decoding circuitry of the baseband circuitry 104 may include convolution, tail-biting convolution, turbo, Viterbi, and / or low-density parity check (LDPC) encoder / decoder functions. The embodiments of the modulation / demodulation and encoder / decoder functions are not limited to these examples, and may include other suitable functions in other embodiments.

[0021] In some embodiments, the baseband circuit 104 may include elements of a protocol stack, such as elements of an Evolved Universal Terrestrial Radio Access Network (EUTRAN) protocol, including, for example, physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and / or radio resource control (RRC) elements. The central processing unit (CPU) 104e of the baseband circuit 104 may be configured to run elements of a protocol stack for signaling of the PHY, MAC, RLC, PDCP, and / or RRC layers. In some embodiments, the baseband circuit may include one or more audio digital signal processors (DSPs) 104f. One or more audio DSPs 104f may include elements for compression / decompression and echo cancellation, and may include other appropriate processing elements in other embodiments. The components of the baseband circuit may be appropriately combined in a single chip or a single chipset, or may be placed on the same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuit 104 and the application circuit 102 may be implemented together, for example, on a system on a chip (SOC).

[0022] In some embodiments, the baseband circuit 104 may provide communications compatible with one or more radio technologies. For example, in some embodiments, the baseband circuit 104 may support communications with an Evolved Universal Terrestrial Radio Access Network (EUTRAN) and / or other wireless metropolitan area networks (WMANs), wireless local area networks (WLANs), wireless personal area networks (WPANs). Embodiments in which the baseband circuit 104 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuits.

[0023] The RF circuit 106 may enable communication with a wireless network using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuit 106 may include switches, filters, amplifiers, etc. that facilitate communication with the wireless network. The RF circuit 106 may include a receive signal path that may include circuitry that down-converts RF signals received from the FEM circuit 108 and provides baseband signals to the baseband circuit 104. The RF circuit 106 may also include a transmit signal path that may include circuitry that up-converts baseband signals provided by the baseband circuit 104 and provides an RF output signal to the FEM circuit 108 for transmission.

[0024] In some embodiments, the RF circuit 106 may include a receive signal path and a transmit signal path. The receive signal path of the RF circuit 106 may include a mixer circuit 106a, an amplifier circuit 106b, and a filter circuit 106c. The transmit signal path of the RF circuit 106 may include a filter circuit 106c and the mixer circuit 106a. The RF circuit 106 may also include a synthesizer circuit 106d for synthesizing frequencies for use by the mixer circuit 106a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuit 106a of the receive signal path may be configured to down-convert the RF signal received from the FEM circuit 108 based on the synthesized frequency provided by the synthesizer circuit 106d. The amplifier circuit 106b may be configured to amplify the down-converted signal, and the filter circuit 106c may be a low pass filter (LPF) or a band pass filter (BPF) configured to remove undesirable signals from the down-converted signal to generate an output baseband signal. The output baseband signal may be provided to the baseband circuit 104 for further processing. In some embodiments, the output baseband signal may be a zero-frequency baseband signal, although this is not required. In some embodiments, the mixer circuit 106a of the receive signal path may include a passive mixer, although the scope of the embodiments is not limited in this respect.

[0025] In some embodiments, mixer circuit 106a of the transmit signal path may be configured to up-convert an input baseband signal based on a synthesized frequency provided by synthesizer circuit 106d to generate an RF output signal for RF circuit 108. The baseband signal may be provided by baseband circuit 104 and may be filtered by filter circuit 106c. Filter circuit 106c may include a low pass filter (LPF), although the scope of the embodiments is not limited in this respect.

[0026] In some embodiments, the mixer circuit 106a of the receive signal path and the mixer circuit 106a of the transmit signal path may include two or more mixers and may be arranged for orthogonal down-conversion and / or up-conversion, respectively. In some embodiments, the mixer circuit 106a of the receive signal path and the mixer circuit 106a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuit 106a of the receive signal path and the mixer circuit 106a of the transmit signal path may be arranged for direct down-conversion and / or direct up-conversion, respectively. In some embodiments, the mixer circuit 106a of the receive signal path and the mixer circuit 106a of the transmit signal path may be configured for superheterodyne operation.

[0027] In some embodiments, the output baseband signal and the input baseband signal may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternative embodiments, the output baseband signal and the input baseband signal may be digital baseband signals. In these alternative embodiments, RF circuit 106 may include an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC), and baseband circuit 104 may include a digital baseband interface that communicates with RF circuit 106.

[0028] In some dual-mode embodiments, separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

[0029] In some embodiments, synthesizer circuit 106 d may be a fractional-N synthesizer or a fractional-N / N+1 synthesizer, although the scope of the embodiments is not limited in this respect, as other types of frequency synthesizers may also be suitable. For example, synthesizer circuit 106 d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase-locked loop with a divider.

[0030] Synthesizer circuit 106d may be configured to synthesize an output frequency for use by mixer circuit 106a of RF circuit 106 based on the frequency input and the divider control input. In some embodiments, synthesizer circuit 106d may be a fractional-N / N+1 synthesizer.

[0031] In some embodiments, the frequency input may be provided by a voltage controlled oscillator (VCO), although this is not required. The divider control input may be provided by either baseband circuitry 104 or application processor 102, depending on the desired output frequency. In some embodiments, the divider control input (e.g., N) may be determined from a lookup table based on the channel indicated by application processor 102.

[0032] The synthesizer circuit 106d of the RF circuit 106 may include a divider, a delay locked loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the divider may be a dual-mode divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by N or N+1 (e.g., based on carry) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded tunable delay elements, a phase detector, a charge pump, and a D-type flip-flop. In these embodiments, the delay element may be configured to decompose the VCO cycle into Nd equal phase packets (packet of phase), where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0033] In some embodiments, the synthesizer circuit 106d can be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency can be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with the quadrature generator and divider circuit to generate multiple signals at the carrier frequency with multiple different phases relative to each other. In some embodiments, the output frequency can be the LO frequency (fLO). In some embodiments, the RF circuit 106 can include an IQ / polarity converter.

[0034] FEM circuitry 108 may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas 110, amplify the receive signals, and provide the amplified versions of the receive signals to RF circuitry 106 for further processing. FEM circuitry 108 may also include a transmit signal path that may include circuitry configured to amplify transmit signals provided by RF circuitry 106 for transmission by one or more of one or more antennas 110.

[0035] In some embodiments, the FEM circuit 108 may include a TX / RX switch that switches between transmit mode and receive mode operation. The FEM circuit may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuit may include a low noise amplifier (LNA) to amplify the received RF signal and provide the amplified received RF signal as an output (e.g., to the output of the RF circuit 106). The transmit signal path of the FEM circuit 108 may include a power amplifier (PA) that amplifies the input RF signal (e.g., provided by the RF circuit 106), and one or more filters that generate an RF signal for subsequent transmission (e.g., by one or more of the one or more antennas 110).

[0036] In some embodiments, the UE device 100 may include additional elements, such as memory / storage, displays, cameras, sensors, and / or input / output (I / O) interfaces.

[0037] The traditional RACH design for CS-CIoT has several disadvantages.

[0038] First, RA is based on slotted ALOHA technology. However, when a large number (e.g., millions, etc.) of CIoT UEs are deployed, there is a high probability that multiple UEs of the same coverage category will simultaneously attempt to access the network, which leads to RA conflicts and failures.

[0039] Second, in order to meet the low-cost target of CS-CIoT UE, the RACH procedure specified in 3GPP TR 45.820 (which inherently includes multiple sub-procedures) will lead to a longer execution time of the RACH procedure, thereby consuming more UE power. Therefore, reducing the execution of the RACH procedure is the key to improving the battery life of the UE.

[0040] In various embodiments disclosed herein, a preamble-based RA mechanism may be employed. A base station such as an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (evolved Node B, eNodeB or eNB) may periodically allocate RA resources for different coverage categories. For contention-based RA, multiple UEs of the same coverage category may access the network using a sequence randomly selected from a set of known sequences; for non-contention-based RA, the base station may assign a sequence to the UE. The UE's RA request may be made via an RA message, which includes an RA preamble sequence and a payload (e.g., containing a UE ID, RA cause, and buffer status report) that may follow the RA preamble sequence transmission. The payload may be spread using another random spreading sequence, which may be selected from another set of sequences. A UE-specific random time offset selected from a set of predefined time offsets may be imposed on the transmission of the RA message to increase the likelihood of identifying a RA preamble collision when two UEs select the same preamble sequence. The time offset may be selected so that peaks corresponding to different sequences are visible during the auto-correlation process.

[0041] The various aspects discussed herein may provide multiple advantages over conventional RACH designs in CS-CIoT. First, the preamble sequence-based RA process discussed herein may reduce RA conflicts in contention-based RA. Second, a predefined random delay between RA transmissions of UEs in RA resources may be employed to identify UEs (even if they select the same preamble sequence). Third, different random spreading sequences may be used to spread the RA payload to distinguish UEs during preamble conflicts.

[0042] In the traditional RACH design for CS-CIoT, the base station periodically allocates resources for RA in a superframe. Since there is no RACH logical channel defined, RA transmission is performed in the traffic channel using resource mapping of the traffic channel. The UE can send a random number in the allocated RA resources. If the RA messages with random numbers from two UEs collide, there is no mechanism provided in the traditional design to distinguish these UEs. If the random number is successfully received, the base station can allocate dedicated resources for payload transmission from the UE. In addition, the traditional CS-CIoT RA process follows a relatively long RA process similar to the old LTE (Long Term Evolution) RA process in several steps.

[0043] In various aspects discussed herein, a RA message including a RA preamble sequence and a payload may be sent in a RA slot. The preamble sequence may help with time and frequency estimation. The payload may be sent with the preamble to shorten the RA process. A predefined time delay may be introduced for each UE to identify preamble collisions.

[0044] Compared with the traditional CS-CIoT RACH design, the embodiments discussed here reduce RA conflicts and failure rates and improve RA channel capacity. In addition, the shortened RA process reduces power consumption at the UE, allowing longer battery life.

[0045] refer to Figure 2 , a block diagram of a system 200 is shown for facilitating transmission of LAA burst control information associated with an LAA burst to a mobile terminal in accordance with various aspects described herein. The system 200 may include a receiver circuit 210, a processor 220, a transmitter circuit 230, and a memory 240 (the memory may include any of a variety of storage media and may store instructions and / or data associated with one or more of the receiver circuit 210, the processor 220, or the transmitter circuit 230). In various aspects, the system 200 may be included in a user equipment (UE). As described in more detail below, the system 200 may facilitate transmission of RA messages to an eNB in ​​a CS-CIoT wireless system with less power consumption and collision potential than a conventional CS-CIoT RACH design.

[0046] The receiver circuit 210 may receive a set of RA resource allocation information from one of two sources depending on whether contention-based RA or non-contention-based RA is being employed. For contention-based RA, the receiver circuit 210 may receive the RA resource allocation information from a system information (SI) message sent by the eNB. For non-contention-based RA, the receiver circuit 210 may receive the RA resource allocation information and an index of the preamble sequence from a downlink control information (DCI) message received from the eNB. The receiver circuit 210 may also monitor radio link conditions associated with the communication channel.

[0047] Based on the monitored radio link conditions, the processor 220 may determine the coverage class of the UE.The processor 220 may also construct a RA message including a RA preamble and a payload.

[0048] The processor 220 may select one of the two RA preamble sequences according to whether the RA message will be sent via contention-based RA or non-contention-based RA. For contention-based RA, the processor 220 may randomly select the RA preamble from a set of RA preamble sequences for contention-based RA mode. For non-contention-based RA, the RA resource allocation information received from the eNB via a DCI message may indicate the RA preamble via an associated index, and the processor 220 may select the RA preamble associated with the index from a set of RA preamble sequences for non-contention-based RA. In some aspects, different groups of sequences are associated with different coverage categories, and the processor 220 may select the RA preamble from a set of sequences associated with the coverage category (e.g., using appropriate techniques, etc., depending on whether contention-based or non-contention-based RA will be adopted). In these aspects, a longer preamble sequence (e.g., in a coverage category associated with a poorer radio link condition) may be employed to assist in decoding the RA message. In some embodiments, the RA preamble may be padded with one or more dummy bits (eg, at the front, at the end, or both), which may eliminate inter-symbol interference.

[0049] For contention-based or non-contention-based RA, the processor 220 may generate a preamble that may include one or more of a UE identity, a buffer status report (e.g., an indication of the amount of data to be sent, etc.), a reason for the RA request, a repetition number (e.g., when included, the repetition number may be selected based at least in part on the coverage category), or other information. The processor 220 may spread the generated payload via a spreading sequence, wherein the processor 220 may select the spreading sequence from a set of pseudo-random sequences (e.g., randomly or based on RA resource allocation information, which may depend on whether the RA mode is contention-based or non-contention-based). In various aspects, in a contention-based RA mode or a non-contention-based RA mode, a set of pseudo-random sequences from which the spreading sequence is selected may be different from a set of pseudo-random sequences from which the RA preamble is selected. In some aspects, different groups of sequences are associated with different coverage categories, and the processor 220 may select the spreading sequence from a set of sequences associated with the coverage category. In these aspects, longer spreading sequences may be employed (e.g., in coverage categories associated with poorer radio link conditions) to assist in decoding of RA messages.

[0050] The transmitter circuit 230 may transmit an RA message in a random access channel (RACH) in an RA slot (e.g., in an RA slot associated with the coverage class determined by the processor 220). The RA message may include a selected RA preamble and a payload (e.g., spread by a selected spreading sequence). In various aspects, the transmitter circuit 230 may transmit the RA message with a guard interval in one or more of the following locations: before the RA preamble, between the RA preamble and the payload, or after the payload. For multiple repetitions, the transmitter circuit 230 may transmit the RA message multiple times (in different RA slots), the number of transmissions being equal to the number of repetitions indicated by the payload.

[0051] In various aspects, the transmitter circuit 230 can transmit the RA message using a delay that can be selected from a set of predefined delay values. In this aspect, the delay can be a UE-specific value. The set of delay values ​​can be defined so that peaks corresponding to different sequences can be identified through autocorrelation, which can help identify preamble code collisions.

[0052] The receiver circuit 210 may also receive a response to the RA message from the eNB to which the RA message is sent. Assuming that the RA message is successfully received by the eNB, the eNB may allocate resources or reject the RA request. In the former case, the response to the RA message may include the UE identity of the UE and an uplink (UL) grant. In the latter case, the response to the RA message may include the UE identity and an RA rejection message.

[0053] refer to Figure 3 , a block diagram of a system 300 for facilitating communication over a random access channel (RACH) for a cellular Internet of Things (CIoT) user equipment (UE) according to various aspects described herein is shown. The system 300 may include a processor 310, a transmitter circuit 320, a receiver circuit 330, and a memory 340 (the memory may include any of a variety of storage media and may store instructions and / or data associated with one or more of the processor 310, the transmitter circuit 320, or the receiver circuit 330). In various aspects, the system 300 may be included in an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (evolved Node B, eNode B, or eNB) or other base station in a wireless communication network. As described in more detail below, the system 300 may facilitate the transmission of RA messages from a CS-CIoT UE with less power consumption and a lower likelihood of collision than conventional systems.

[0054] The processor 310 may select an RA mode from a contention-based RA mode and a non-contention-based RA mode. The processor 310 may allocate one or more groups of resources as RA time slots for RA requests in an RA channel (RACH). In various aspects, different resources may be allocated for different coverage categories. In these aspects, different amounts of resources may be allocated for different coverage categories, for example, a larger amount of resources may be allocated for coverage categories associated with poorer link conditions.

[0055] The transmitter circuit 320 may transmit the resources allocated for the RA message and the RA parameters. The RA parameters may indicate an RA mode (e.g., contention-based or non-contention-based), and for a non-contention-based RA mode, a designated preamble for each of the one or more UEs. The transmitter circuit 320 may transmit the RA parameters associated with contention-based RA via a system information message, and may transmit the RA parameters associated with non-contention-based RA to the UE via a DCI message, wherein the DCI message indicates the RA preamble for the UE via an associated index.

[0056] The receiver circuit 330 may receive one or more RA requests in the form of RA messages sent by the UE via the assigned UL resources. In various embodiments, each RA message may include an RA preamble and a payload (e.g., a payload that may indicate information associated with the request ID, which may include one or more of a UE ID, a buffer status report, a RA cause, and a number of repetitions to which the RA message will be sent). As described herein, the payload may be spread by a spreading sequence, and in some aspects, the length of the RA preamble and the spreading sequence may be changed based on the coverage category. In addition, as discussed herein, a guard interval and / or a dummy bit may be included in the RA message, and the transmission timing of the RA message may be offset by a certain delay (which may depend on the UE).

[0057] For each received RA message, the processor 310 may attempt to decode the RA message. For RA messages that are repeatedly sent multiple times, soft combining of multiple versions may be employed. If the RA message is successfully decoded, the processor 310 may generate one of an UL grant message or an RA rejection message, which may be based on the decision of the scheduler in the eNB. For each decoded RA message, the transmitter circuit 320 may send the UE ID of the UE (which sent the RA message) in response to the RA message, followed by an UL grant or RA rejection message.

[0058] refer to Figure 4, a flow chart of a method 400 for facilitating the transmission of RA messages over RACH in a CS-CIoT wireless network according to various aspects described herein is shown. In some aspects, the method 400 can be performed at a UE. In other aspects, a machine-readable medium can store instructions associated with the method 400 that, when executed, cause the UE to perform the actions of the method 400.

[0059] At 410, a set of RA resource allocation information may be received (eg, via system information or a DCI message), the set of RA resource allocation information may include an indication of an RA mode and, in the case of non-contention based RA, an index of a designated RA preamble sequence.

[0060] At 420, a coverage class can be determined based on a radio link condition with the eNB.

[0061] At 430, an RA preamble sequence may be selected based at least in part on the RA resource allocation information. For contention-based RA, the RA preamble sequence may be randomly selected from a set of sequences used for contention-based RA; for non-contention-based RA, the RA preamble indicated by the index may be selected from a set of sequences used for non-contention-based RA.

[0062] At 440, a payload may be generated, which may include one or more of a UE ID of the UE implementing method 400, a buffer status report, a repetition number (the number of times the RA message is to be sent), and the like.

[0063] At 450, the payload can be spread by a spreading sequence, which can be selected (eg, randomly selected) from a set of sequences that can be different from a set of sequences used for the RA preamble.

[0064] At 460, an RA message including an RA preamble and a payload (and optionally one or more guard bands and / or dummy bits, etc.) may be sent. If the payload indicates a number of repetitions and the number is greater than 1, the RA message may be sent that number of times. In various aspects, the RA message may be sent with a delay that may be selected from a set of delays (which may be UE-specific).

[0065] refer to Figure 5 , a method 500 is shown for facilitating communication with one or more UEs via RACH in a CS-CIoT wireless system according to various aspects described herein. In some aspects, the method 500 can be performed at an eNB. In other aspects, a machine-readable medium can store instructions associated with the method 500, which when executed can cause the eNB to perform the actions of the method 500.

[0066] At 510, a RA mode may be selected between a contention-based mode and a non-contention-based mode.

[0067] At 520, a set of uplink (UL) resources can be allocated for the RA message.

[0068] At 530, RA parameters may be sent indicating the selected RA mode and, for non-contention based RA, the selected RA preamble for each UE for the non-contention based RA (eg, indicated by an associated index, etc.).

[0069] At 540, one or more RA messages can be received, each RA message including both a RA preamble and a payload (e.g., a payload indicating one or more of a UE ID, a buffer status report, a RA cause, a repetition number, etc.) according to various aspects described herein.

[0070] At 550, an attempt may be made to decode each received RA message. For RA messages that are sent repeatedly multiple times, soft combining may be employed.

[0071] At 560, for each RA message that is successfully decoded, a response may be sent, which may include either the UE ID that generated the RA message and a UL Grant or the UE ID that generated the RA message and a RA Reject message.

[0072] Additional details, example embodiments, and features are provided in the discussion that follows.

[0073] The uplink (UL) of the CS-CIoT system contains 36 FDMA (frequency division multiple access) channels, each with a 5kHz bandwidth. In the 5kHz bandwidth, 3.75kHz is allocated for data transmission, and the remaining bandwidth is used as a guard band. Since there is no UL common control channel in the CS-CIoT system, RA messages are sent on the UL traffic channel without any channel bonding. According to the traffic model specified in 3GPP TR 45.820, an average of 6.8 UEs access the network per second to send their packets. In the UL, when channel bonding is not used, the minimum allocation granularity is 8 time slots (40ms), which can carry a total of 150 uncoded symbols.

[0074] In the traditional RA process, the base station allocates RA resources for different coverage categories in a time division or frequency division manner. Since the RA message is sent using the same MSC (modulation and coding scheme) and CBS (code block size) as the data traffic, if two UEs send their RA messages at the same time, the base station cannot detect them, resulting in a collision of the received messages.

[0075] To address these issues, various embodiments may employ techniques disclosed herein to reduce RA collision likelihood and device (eg, UE) power usage.

[0076] refer to Figure 6 , shows an example structure of a RA message 600 with a guard band 630 according to various aspects described herein. Figure 6 As shown, the RA message 600 according to various embodiments includes a preamble sequence 610 and a payload 620. The preamble sequence 610 may be selected from a set of predefined sequences. The payload 620 may be spread by using a spreading sequence selected (e.g., randomly) from a set of spreading sequences. A predefined guard interval 630 may follow the preamble sequence 610 and precede the payload 620. In addition, the guard interval 630 may be included at the beginning and end of the RA message 600 (one before the preamble sequence 610 and one after the payload 620), which may eliminate ISI (inter-symbol interference) between adjacent time slots.

[0077] refer to Figure 7 , shows an example structure of an RA message 700 with a guard band 730 and dummy bits 740 according to various aspects described herein. The preamble sequence 710 may be padded with dummy bits 740 to further eliminate ISI. The ISI may come from a payload modulated by GMSK (Gaussian Minimum Shift Keying) in the same time slot or a previous time slot. In an example embodiment, the 2 symbols at each end of the preamble 710 may be padded to a 16-symbol long sequence to make an example 20-symbol long sequence such as the example preamble 710. The payload 720 may be spread using a sequence selected from a set of known sequences, which may be a different set of sequences from the set of sequences from which the preamble 710 was selected. The set of sequences from which the preamble 710 was selected and the set of sequences from which the spreading sequence was selected may be a set of sequences having good correlation characteristics, respectively, and each of the two sets of sequences may be a set of orthogonal or non-orthogonal sequences. The spreading sequence and the preamble sequence may be selected from two different sets of sequences. A guard interval 730 may be introduced between the preamble 710 and the payload 720 to avoid collision of the preamble 710 from one UE with the payload 720 from another UE. Both the guard interval 730 (eg, the guard interval between the preamble 710 and the payload 720) and the dummy bits 740 are optional.

[0078] In some embodiments, the eNB (e.g., or other base stations) may allocate different amounts of RA resources for different coverage categories. For example, more RA resources may be allocated for weaker coverage categories. There are two possible options for using more resources, which may be used alone or in combination.

[0079] In the first option, a UE that repeatedly sends RA messages can use more RA resources for weaker coverage categories. The number of repetitions can be predetermined based on the coverage category. Upon receiving repeated messages, the eNB can use IQ combining or some other soft combining techniques to accumulate them.

[0080] In the second option, in a plurality of consecutive RA resources, the UE may use a longer preamble sequence and a higher spreading factor to improve RA decoding performance. In an embodiment implementing the second option, different groups of sequences may be allocated to different coverage categories.

[0081] The RACH design discussed here can reduce the power consumption of CS-CIoT devices by dividing the RACH process into multiple sub-processes. When the UE determines the coverage category and identifies the RA resources based on the downlink (DL) signal quality metric, two different RA processes can be implemented based on whether contention-based RA or non-contention-based RA will be adopted.

[0082] For contention-based RA, the UE obtains the RA resource allocation information from the system information message. The UE may then randomly select a preamble sequence from a set of predefined sequences. A payload may be generated that may include one or more of a UE ID, a buffer status report, a RA cause, a number of repetitions, etc. If the RA message is successfully received by the eNB, the eNB may respond with the UE ID and a UL grant in a DCI message. The UE may then decode the UL grant from the eNB and may send UL packets in the allocated resources indicated in the UL grant. Alternatively, if the eNB successfully receives the RA message but the eNB decides not to grant the UE, the eNB may send the UE ID and a RA rejection message.

[0083] For non-contention-based RA, the UE obtains RA resource allocation information and preamble sequence allocation (e.g., indicated by an associated index, etc.) from the DCI message. The UE may select a preamble sequence specified by the eNB and may generate a payload including one or more of a UE ID, a buffer status report, a RA cause, a number of repetitions, etc. If the RA message is successfully received by the eNB, the eNB may respond with the UE ID and a UL grant in the DCI message. The UE may decode the UL grant from the eNB and may send UL packets in the allocated resources indicated in the UL grant. Alternatively, if the eNB successfully receives the RA message but the eNB decides not to grant the UE, the eNB may send the UE ID and a RA rejection message.

[0084] Examples herein may include subject matter such as a method, an apparatus for performing the actions or blocks of the method, at least one machine-readable medium that, when executed by a machine (e.g., a processor with memory, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc.), causes the machine to perform the actions of the method, or an apparatus or system that communicates in parallel using multiple communication technologies according to the embodiments and examples described herein.

[0085] Example 1 is an apparatus configured to be used in a user equipment (UE), comprising a receiver circuit, a processor, and a transmitter circuit. The receiver circuit is configured to receive random access (RA) resource allocation information through one of a system information message or a downlink control information (DCI) message. The processor is operably coupled to the receiver circuit and is configured to: select an RA preamble sequence; generate a payload; and spread the payload through a spreading sequence. The transmitter circuit is configured to send an RA message including an RA preamble sequence and a payload based on the RA resource allocation information, wherein the RA message is sent in an RA time slot. The receiver circuit is further configured to receive a response including one of an uplink (UL) grant or RA rejection message and the device identity of the UE.

[0086] Example 2 includes the subject matter of Example 1, wherein the processor is configured to randomly select the RA preamble sequence from a first set of RA preamble sequences for a contention-based pseudo-random access mode.

[0087] Example 3 includes the subject matter of Example 1, wherein the processor is further configured to randomly select the spreading sequence from a second set of pseudo-random sequences.

[0088] Example 4 includes the subject matter of Example 1, wherein the processor is configured to, for a non-contention based random access mode, select the RA preamble sequence from a first set of RA preamble sequences based on the RA resource allocation information.

[0089] Example 5 includes the subject matter of Example 1, wherein the processor is further configured to select a spreading sequence from a second set of pseudo-random sequences, wherein the spreading sequence is selected based on the RA resource allocation information.

[0090] Example 6 includes the subject matter of any of Examples 1-5, including or omitting the optional features, wherein the payload indicates at least one of an amount of data available for transmission or a buffer status report, an identity of the UE, and a RA cause.

[0091] Example 7 includes the subject matter of Example 6, including or omitting the optional features, wherein the payload further indicates a repetition number, and wherein the transmitter circuit is configured to transmit the RA message N times, N being the repetition number.

[0092] Example 8 includes the subject matter of Example 7, including or omitting the optional features, wherein the processor is further configured to: determine a coverage class based on a radio link condition; and select a number of repetitions based on the coverage class.

[0093] Example 9 includes the subject matter of any of Examples 1-5, including or omitting the optional features, wherein the transmitter circuit is configured to send the RA message with a delay based on a delay value selected from a set of predefined delay values.

[0094] Example 10 includes the subject matter of any of Examples 1-8, including or omitting the optional features, wherein the transmitter circuit is configured to transmit the RA message with a delay based on a delay value selected from a set of predefined delay values.

[0095] Example 11 includes the subject matter of any of Examples 1-10, including or omitting the optional features, wherein the RA message includes a plurality of guard intervals.

[0096] Example 12 includes the subject matter of Example 1, wherein the payload indicates at least one of an amount of data available for transmission or a buffer status report, a RA cause, and a device identity of the UE.

[0097] Example 13 includes the subject matter of Example 1, wherein the transmitter circuit is configured to transmit the RA message with a delay based on a delay value selected from a set of predefined delay values.

[0098] Example 14 includes the subject matter of Example 1, wherein the RA message includes a plurality of guard intervals.

[0099] Example 15 is a machine-readable medium comprising instructions that, when executed, cause a user equipment (UE) to: receive a set of random access (RA) resource allocation information indicating a RA mode; determine a coverage category based on a set of radio link conditions; select an RA preamble sequence based at least in part on the indicated RA mode; generate a payload based at least in part on the coverage category; spread the payload using a spreading sequence selected based at least in part on the RA mode; and send a RA message including the RA preamble sequence and the payload.

[0100] Example 16 includes the subject matter of Example 15, wherein the RA message includes a plurality of guard intervals.

[0101] Example 17 includes the subject matter of Example 16, wherein a first guard interval of the plurality of guard intervals precedes the RA preamble sequence and a second guard interval of the plurality of guard intervals follows the payload.

[0102] Example 18 includes the subject matter of Example 16, wherein a third guard interval of the plurality of guard intervals follows the RA preamble sequence and precedes the payload.

[0103] Example 19 includes the subject matter of any of Examples 15-18, including or omitting the optional features, wherein the RA preamble sequence includes one or more original dummy bits and one or more final dummy bits.

[0104] Example 20 includes the subject matter of any of Examples 15-18, including or omitting the optional features, wherein the RA mode is contention-based RA, wherein the RA preamble sequence is randomly selected from a first set of pseudo-random preamble sequences, and wherein the spreading sequence is randomly selected from a second set of pseudo-random sequences.

[0105] Example 21 includes the subject matter of Example 20, including or omitting the optional features, wherein the first set of pseudo-random preamble sequences is different from the second pseudo-random sequence.

[0106] Example 22 includes the subject matter of any of Examples 15-18, including or omitting the optional features, wherein the RA mode is non-contention-based RA, wherein the RA preamble sequence is selected from a first set of pseudo-random preamble sequences based on a set of RA parameters, and wherein the RA preamble sequence is selected from a second set of pseudo-random sequences based on a set of RA parameters.

[0107] Example 23 includes the subject matter of any of Examples 15-18, including or omitting the optional features, wherein the instructions, when executed, further cause the UE to receive a first response to the RA message including the UE's device identity and an uplink (UL) grant, or to receive a second response including the UE's device identity and an RA rejection message.

[0108] Example 24 includes the subject matter of any of Examples 15-18, including or omitting the optional features, wherein the RA message is sent delayed in the RA time slot by a delay value selected from a set of predefined delay values.

[0109] Example 25 includes the subject matter of Example 24, including or omitting the optional features, wherein a set of predefined delay values ​​is defined to facilitate selection by autocorrelation.

[0110] Example 26 includes the subject matter of Example 15, wherein the RA preamble sequence comprises one or more original dummy bits and one or more final dummy bits.

[0111] Example 27 includes the subject matter of Example 15, wherein the RA mode is contention-based RA, wherein the RA preamble sequence is randomly selected from a first set of pseudo-random preamble sequences, and wherein the spreading sequence is randomly selected from a second set of pseudo-random sequences.

[0112] Example 28 includes the subject matter of Example 15, wherein the RA mode is non-contention-based RA, wherein the RA preamble sequence is selected from a first set of pseudo-random preamble sequences based on a set of RA parameters, and wherein the RA preamble sequence is selected from a second set of pseudo-random sequences based on a set of RA parameters.

[0113] Example 29 includes the subject matter of Example 15, wherein the instructions, when executed, further cause the UE to receive a first response to the RA message including the UE's device identity and an uplink (UL) grant, or to receive a second response including the UE's device identity and an RA rejection message.

[0114] Example 30 includes the subject matter of Example 15, wherein the RA message is sent delayed in the RA time slot by a delay value selected from a set of predefined delay values.

[0115] Example 31 is a device configured to be used in an evolved Node B (eNB), comprising a processor, a transmitter circuit, and a receiver circuit. The processor is configured to: select a random access (RA) mode; and allocate a set of uplink (UL) resources for an RA message. The transmitter circuit is configured to send a set of RA parameters indicating the RA mode and a set of UL resources allocated for the RA message. The receiver circuit is configured to receive one or more RA requests through a set of UL resources allocated for the RA message, wherein each of the one or more RA requests includes an RA preamble sequence and a payload.

[0116] Example 32 includes the subject matter of Example 31, wherein the one or more RA requests include a first RA request received from a first UE among the plurality of UEs, and wherein a length of a payload of the first RA request and a length of a RA preamble sequence of the first RA request are based on a coverage class associated with the first UE.

[0117] Example 33 includes the subject matter of Example 31, wherein the one or more RA requests include a first RA request received from a first UE among the plurality of UEs, and wherein the transmitter circuit is further configured to send a downlink control message including a device identity of the first UE and a UL grant.

[0118] Example 34 includes the subject matter of Example 31, wherein the one or more RA requests include a first RA request received from a first UE among the plurality of UEs, and wherein the transmitter circuit is further configured to send a downlink control message including a device identity of the first UE and a RA reject message.

[0119] Example 35 includes the subject matter of Example 31, wherein the one or more RA requests include multiple repetitions of a first RA request received from a first UE in the plurality of UEs, and wherein the receiver circuit is configured to accumulate the multiple repetitions of the first RA request by soft combining.

[0120] Example 36 is an apparatus configured to be used in a user equipment (UE), comprising a component for receiving, a component for processing, and a component for sending. The component for receiving is configured to receive random access (RA) resource allocation information through one of a system information message or a downlink control information (DCI) message. The component for processing is operably coupled to the component for receiving and is configured to: select an RA preamble sequence; generate a payload; and spread the payload through a spreading sequence. The component for sending is configured to send an RA message including an RA preamble sequence and a payload based on the RA resource allocation information, wherein the RA message is sent in an RA time slot. The component for receiving is further configured to receive a response including one of an uplink (UL) grant or RA rejection message and the device identity of the UE.

[0121] Example 37 is an apparatus configured to be used in an evolved Node B (eNB), comprising a component for processing, a component for sending, and a component for receiving. The component for processing is configured to: select a random access (RA) mode; and allocate a set of uplink (UL) resources for an RA message. The component for sending is configured to send a set of RA parameters indicating the RA mode and a set of UL resources for the RA message. The component for receiving is configured to receive one or more RA requests through a set of UL resources allocated for the RA message, wherein each of the one or more RA requests includes an RA preamble sequence and a payload.

[0122] Example 38 includes the subject matter of Example 1, wherein the processor is a baseband processor.

[0123] The above description of the illustrated embodiments of the present disclosure (including what is described in the Abstract) is not intended to be exhaustive of the disclosed embodiments or to limit the disclosed embodiments to the precise forms disclosed. Although specific embodiments and examples are described herein for illustrative purposes, various modifications that are considered to fall within the scope of these embodiments and examples and that can be recognized by those skilled in the relevant art are also possible.

[0124] In this regard, although the disclosed subject matter has been described in conjunction with various available embodiments and corresponding drawings, it will be understood that other similar embodiments may be used where applicable or various modifications and additions may be made to the described embodiments without departing from the scope of the disclosed subject matter to perform the same, similar, or alternative functions of the disclosed subject matter. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but should be understood in accordance with the scope and breadth of the appended claims.

Claims

1. A user equipment UE, comprising: The receiver circuit is configured to receive random access RA resource allocation information through one of a system information message or a downlink control information DCI message; as well as a processor operably coupled to the receiver circuit and configured to: selecting a RA preamble sequence; and generating a payload including an identifier of the UE; a transmitter circuit configured to send an RA message including the RA preamble sequence and the payload based on the RA resource allocation information, Therein, the receiver circuit is further configured to receive a RA response in response to the RA message, the RA response having the same identifier of the UE as the identifier of the UE included in the payload of the RA message and including an uplink grant.

2. The UE according to claim 1, wherein: The identifier of the UE is a Cell Radio Network Temporary Identifier, C-RNTI.

3. The UE according to claim 1, wherein: The RA response is received via a DCI message.

4. The UE according to claim 1, wherein: The transmitter circuit is configured to transmit uplink data based on the RA response.

5. The UE according to claim 1, wherein: The processor is configured to randomly select the RA preamble sequence from a first set of RA preamble sequences for a contention-based pseudo-random access mode.

6. The UE according to claim 1, wherein: The processor is configured to select the RA preamble sequence from a first group of RA preamble sequences based on the RA resource allocation information for a non-contention based random access mode.

7. The UE according to claim 1, wherein: The payload indicates the amount of data available for transmission or a buffer status report.

8. The UE according to claim 4, wherein: The payload further indicates a repetition number, and wherein the transmitter circuit is configured to transmit the RA message N times, wherein N is the repetition number.

9. The UE according to claim 8, wherein: The processor is further configured to: determining a coverage class based on radio link conditions; and The number of repetitions is selected based on the coverage category.

10. The UE according to claim 1, wherein: The transmitter circuit is configured to transmit the RA message with a delay based on a delay value selected from a set of predefined delay values.

11. The UE according to claim 1, wherein: The processor is a baseband processor.

12. A method comprising: Receiving random access RA resource allocation information through one of a system information message or a downlink control information DCI message; Selecting the RA preamble sequence; generating a payload comprising an identifier of the UE; Based on the RA resource allocation information, sending an RA message including the RA preamble sequence and the payload; and An RA response is received in response to the RA message, the RA response having the same identifier of the UE as the identifier of the UE included in the payload of the RA message and including an uplink grant.

13. The method of claim 12, wherein: The identifier of the UE is a Cell Radio Network Temporary Identifier, C-RNTI.

14. The method of claim 12, wherein: The RA preamble sequence is randomly selected from a first set of RA preamble sequences for contention-based pseudo-random access mode.

15. The method of claim 12, wherein: The RA preamble sequence is selected from a first group of RA preamble sequences based on the RA resource allocation information for a non-contention-based random access mode.

16. The method of claim 12, wherein: The payload indicates the amount of data available for transmission or a buffer status report.

17. The method of claim 16, wherein: The payload further indicates a repetition number, and wherein the RA message is sent N times, wherein N is the repetition number.

18. The method of claim 17, further comprising: determining a coverage class based on radio link conditions; as well as The number of repetitions is selected based on the coverage category.

19. The method of claim 12, wherein: The RA message is sent with a delay based on a delay value selected from a set of predefined delay values.

20. A baseband processor configured to perform operations, the operations comprising: Receiving random access RA resource allocation information through one of a system information message or a downlink control information DCI message; Selecting the RA preamble sequence; generating a payload comprising an identifier of the UE; Based on the RA resource allocation information, outputting an RA message including the RA preamble sequence and the payload for sending to a base station; as well as In response to the sending of the RA message, a response indicating the identifier of the UE and uplink resource allocation that is the same as the identifier of the UE included in the payload of the RA message is received.

21. The baseband processor of claim 20, wherein: The identifier of the UE is a Cell Radio Network Temporary Identifier, C-RNTI.

22. The baseband processor of claim 20, wherein: The RA preamble sequence is randomly selected from a first set of RA preamble sequences for contention-based pseudo-random access mode.

23. The baseband processor of claim 20, wherein: The RA preamble sequence is selected from a first group of RA preamble sequences based on the RA resource allocation information for a non-contention-based random access mode.

24. The baseband processor of claim 20, wherein: The payload indicates at least one of an amount of data available for transmission or a buffer status report, a device identity of the UE, and a RA cause.

25. The baseband processor of claim 24, wherein: The payload further indicates a repetition number, and wherein the RA message is sent N times, wherein N is the repetition number.

26. The baseband processor of claim 25, wherein: The operations also include: determining a coverage class based on radio link conditions; and The number of repetitions is selected based on the coverage category.

27. The baseband processor of claim 20, wherein: The RA message is sent with a delay based on a delay value selected from a set of predefined delay values.

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